UV-Assisted 3D Printing of Glass and Carbon Fiber-Reinforced Dual-Cure Polymer Composites.

PubMed

Invernizzi, Marta; Natale, Gabriele; Levi, Marinella; Turri, Stefano; Griffini, Gianmarco

2016-07-16

Glass (GFR) and carbon fiber-reinforced (CFR) dual-cure polymer composites fabricated by UV-assisted three-dimensional (UV-3D) printing are presented. The resin material combines an acrylic-based photocurable resin with a low temperature (140 °C) thermally-curable resin system based on bisphenol A diglycidyl ether as base component, an aliphatic anhydride (hexahydro-4-methylphthalic anhydride) as hardener and (2,4,6,-tris(dimethylaminomethyl)phenol) as catalyst. A thorough rheological characterization of these formulations allowed us to define their 3D printability window. UV-3D printed macrostructures were successfully demonstrated, giving a clear indication of their potential use in real-life structural applications. Differential scanning calorimetry and dynamic mechanical analysis highlighted the good thermal stability and mechanical properties of the printed parts. In addition, uniaxial tensile tests were used to assess the fiber reinforcing effect on the UV-3D printed objects. Finally, an initial study was conducted on the use of a sizing treatment on carbon fibers to improve the fiber/matrix interfacial adhesion, giving preliminary indications on the potential of this approach to improve the mechanical properties of the 3D printed CFR components.

Photocurable acrylic composition, and U.V. curing with development of U.V. absorber

DOEpatents

McKoy, Vincent B.; Gupta, Amitava

1992-01-01

In-situ development of an ultraviolet absorber is provided by a compound such as a hydroxy-phenyl-triazole containing a group which protects the absorber during actinically activated polymerization by light at first frequency. After polymerization the protective group is removed by actinic reaction at a second frequency lower than the first frequency. The protective group is formed by replacing the hydrogen of the hydroxyl group with an acyl group containing 1 to 3 carbon atoms or an acryloxy group of the formula: ##STR1## where R.sup.1 is either an alkyl containing 1 to 6 carbon atoms or --CH.dbd.CH.sub.2.

Surface contamination to UV-curable acrylates in the furniture and parquet industry.

PubMed

Surakka, J; Lindh, T; Rosén, G; Fischer, T

2001-03-01

Surface contamination to ultraviolet radiation curable coatings (UV coatings), used increasingly in the parquet and furniture industry, is a matter of concern as a source for skin contamination. UV coatings contain chemically and biologically reactive acrylates, well known as skin contact irritants and sensitizers. Surface contamination may spread secondarily to equipment and other unexpected areas even outside the workplace. Yet, studies concerning this type of contamination are lacking due to lack of suitable sampling methods. Surface contamination of the work environment with risk for skin exposure to UV coating was measured employing a quantitative adhesive tape sampling method developed for this purpose. A pilot study was first performed at three workplaces to evaluate the contamination. In the main study, we wanted to locate and identify in detail the surface contamination of areas where problems exist, and to determine the extent of the problem. Measurements were performed at seven workplaces on two separate workdays (round 1 and 2) within a six-month period. Samples were collected from the workplaces based on the video monitoring of skin contact frequency with the surfaces and categorized into three groups to analyze risk. The pilot study indicated that surface contamination to TPGDA containing UV coatings was common, found in 76 percent of the surfaces, and varied with a maximum of 909 microg TPGDA 10 cm(-2) sampling area. In the main study TPGDA was found in 153 out of 196 collected samples (78.1%); for round one 78.1 percent (82 out of 105 samples) and for round two 78.0 percent (71 out of 91 samples). The average TPGDA mass on positive surface samples was on the first round 2,247 +/- 7,462 microg, and on the second round 2,960 +/- 4,590 microg. We conclude that surface contamination to uncured UV coatings at UV-curing lines is common and this involves a risk for harmful, unintentional skin exposure to acrylates.

Comparative study of sorption and solubility of heat-cure and self-cure acrylic resins in different solutions.

PubMed

Saini, Rajesh; Kotian, Ravindra; Madhyastha, Prashanthi; Srikant, N

2016-01-01

The objective of this study was to compare the sorption and solubility of heat-cure and self-cure acrylic resins in different solutions. One heat-cure acrylic resin (Trevalon) and one self-cure acrylic resin (Rapid Repair) were studied. Five groups of square-shaped specimens (20 mm × 20 mm × 2 mm) were prepared for each acrylic resin and then immersed in five solutions: distilled water, artificial saliva, denture cleansing solution, distilled water, and denture cleaning solution for 12 h alternatively, artificial saliva and denture cleaning solution for 12 h alternatively at 37 ± 2°C, and tested sorption and solubility by weight gain/loss method, respectively, after 1, 6, and 11 weeks. The data were analyzed by one-way analysis of variance followed by post hoc Tukey's test. Water sorption mean values varied from 17.5 ± 0.88 to 27.25 ± 1.04 μg/mm 3 for heat cure and from 12.75 ± 0.55 to 19.75 ± 1.04 μg/mm 3 for self-cure in the different solutions after different interval periods of 1, 6, and 11 weeks. These values were statistically significant (P< 0.001). Water solubility mean values varied from 0.25 ± 0.55 to 1.5 ± 0.55 μg/mm 3 for heat cure and from 1.5 ± 0.55 to 6.5 ± 0.55 μg/mm 3 for self-cure in the different solutions after different interval periods of 1, 6, and 11 weeks. These values were statistically not significant (P > 0.05). There was no linear correlation between sorption and solubility values. Overall, analysis of results showed the maximum sorption value in denture cleansing solution followed by alternative soaking in distilled water and artificial saliva. Least sorption was observed with artificial saliva followed by distilled water. Both heat-cure and self-cure acrylic resins showed varying water sorption and solubility. The results of both water sorption and solubility showed compliance with the International Standards Organization specification. No correlation was found between water sorption and solubility. Artificial saliva solution is a better storage medium than distilled water and denture cleansing solution for both heat-cure and self-cure acrylic resins.

Acrylic and metal based Y-branch plastic optical fiber splitter with optical NOA63 polymer waveguide taper region

NASA Astrophysics Data System (ADS)

Ehsan, Abang Annuar; Shaari, Sahbudin; Rahman, Mohd Kamil Abd.

2011-01-01

We proposed a simple low-cost acrylic and metal-based Y-branch plastic optical fiber (POF) splitter which utilizes a low cost optical polymer glue NOA63 as the main waveguiding medium at the waveguide taper region. The device is composed of three sections: an input POF waveguide, a middle waveguide taper region and output POF waveguides. A desktop high speed CNC engraver is utilized to produce the mold inserts used for the optical devices. Short POF fibers are inserted into the engraved slots at the input and output ports. UV curable optical polymer glue NOA63 is injected into the waveguide taper region and cured. The assembling is completed when the top plate is positioned to enclose the device structure and connecting screws are secured. Both POF splitters have an average insertion loss of 7.8 dB, coupling ratio of 55: 45 and 57: 43 for the acrylic and metal-based splitters respectively. The devices have excess loss of 4.82 and 4.73 dB for the acrylic and metal-based splitters respectively.

The Evaluation of Water Sorption/Solubility on Various Acrylic Resins

PubMed Central

Tuna, Suleyman Hakan; Keyf, Filiz; Gumus, Hasan Onder; Uzun, Cengiz

2008-01-01

Objectives The absorption of water by acrylic resins is a phenomenon of considerable importance since it is accompanied by dimensional changes, a further undesirable effect of absorbed water in acrylic resins to reduce the tensile strength of the material. Solubility is also an important property because it represents the mass of soluble materials from the polymers. Methods Ten acrylic resin-based materials were evaluated: two heat cure acrylic resins (De Trey QC-20, Meliodent Heat Cure) and eight self cure acrylic resins (Meliodent Cold, Akrileks, Akribel, Akribel Transparent, Vertex Trayplast, Formatray, Dentalon Plus, Palavit G). To evaluate water sorption and water solubility, thirty square-shaped specimens (20×20×1.5 mm) were fabricated from the wax specimens. One way ANOVA test, Tukey test and Pearson correlation coefficient performed for data. Results Water sorption mean values varied from 11.33±0.33 to 30.46±0.55 μg/mm3. Water solubility mean values varied from −0.05±0.23 to 3.69±0.12 μg/mm3. There was statistically significant difference between mean values of the materials (P<.05). There was no linear correlation between sorption and solubility values. Conclusions The results of the water sorption and water solubility values of both self-cured and heat-cured acrylic resins were in accordance with the ISO specification. No correlation found between water sorption and water solubility values. PMID:19212546

Processing factors affecting the clarity of a rapid-curing clear acrylic resin.

PubMed

Keng, S B; Cruickshanks-Boyd, D W; Davies, E H

1979-10-01

The difficulty in repeatedly producing unblemished, clear acrylic resin in the dental laboratory has hindered its wider use, despite its many advantages over coloured material. Recently, rapid-cure dental acrylics have been introduced, which are available in both clear and coloured forms. This investigation examined various factors which may influence the production of unblemished, rapid-curing, clear acrylic resin. Utilizing a quantitative assessment of clarity, the most important factor influencing the clarity of the resin is shown to be the choice of separating medium. Tin-foil produces extremely high clarity, but alginate mould separator causes surface blanching. However, this surface blanching can be removed by polishing. Porosity, caused by too rapid curing, and stone model dryness are of only secondary importance. Possible water contamination of the monomer liquid due to accidental exposure only affects clarity at very high levels of contamination.

Applications of Blue Light-curing Acrylic Resin to Forensic Sample Preparation and Microtomy.

PubMed

Groves, Ethan; Palenik, Christopher S

2016-03-01

This study discusses the results of an evaluation of a one-part blue light-curing acrylic resin for embedding trace evidence prior to the preparation of thin sections with a microtome. Through a comparison to several epoxy resins, the physical properties relevant to both trace evidence examination and analytical microscopy in general, including as viscosity, clarity, color, hardness, and cure speed, were explored. Finally, thin sections from paint samples embedded in this acrylic resin were evaluated to determine if, through smearing or impregnation, the resin contributed to the infrared spectra. The results of this study show that blue light-curing acrylic resins provide the desired properties of an embedding medium, generate high-quality thin sections, and can significantly simplify the preparation of paint chips, fibers and a multitude of other types of microscopic samples in the forensic trace evidence laboratory. © 2015 American Academy of Forensic Sciences.

Design and synthesis of bio-based UV curable PU acrylate resin from itaconic acid for coating applications

PubMed Central

Patil, Deepak M.; Phalak, Ganesh A.; Mhaske, S. T.

2017-01-01

Abstract UV curable PUA resin was successfully synthesized from polyol based on sustainable resource originated from itaconic acid (IA), isophorone diisocyanate (IPDI) and 2-hydroxyethyl methacrylate (HEMA). A polyol was synthesized by condensation reaction of IA with 16-hexanediol in the presence of p-Toluenesulfonic acid (pTSA). The synthesized PUA resin was characterized for its structural elucidation by using Fourier Transform Infrared Spectrophotometer (FTIR), 1H and 13C NMR spectroscopy. The synthesized UV curable PUA resin was incorporated in varying concentrations in conventional PUA coating system. The effects of varying concentration of synthesized UV curable PUA resin on rheology, crystallinity, thermal and coating properties were evaluated. The rheological behavior of the resins were evaluated at variable stress and result showed decrease in viscosity of resin as concentration of synthesized UV curable PUA resin increases in conventional PUA resin. The cured coatings have been evaluated for glass transition temperature (T g) and thermal behavior by differential scanning calorimeter and thermogravimetric analysis respectively. The degree of crystallinity of the coatings was determined from X-ray diffraction patterns using the PFM program. It was found that increase in the mass proportion of IA based PUA in coatings, the coating becomes more rigid and crystalline. The synthesized UV curable PUA coatings showed interesting mechanical, chemical, solvent and thermal properties as compared to the conventional PUA. Further, cured coatings were also evaluated for gel content and water absorption. PMID:29491798

Microscopic progression in the free radical addition reaction: modeling, geometry, energy, and kinetics.

PubMed

Zhang, Yun; Huang, Hong; Liang, Zhiling; Liu, Houhe; Yi, Ling; Zhang, Jinhong; Zhang, Zhiqiang; Zhong, Cheng; Huang, Yugang; Ye, Guodong

2017-03-01

The free radical addition reaction is very important in UV curing. The benzoyl radical is the most commonly observed radical. In the addition process, the benzoyl radical adds to an acrylate monomer, forming a primary radical that has great value for subsequent research. In this article, a quantum chemical method was used to study the microscopic progression from the reactive complex to the saddle point. The reactions of three monomers (amylene, allyl methyl ether and methyl acrylate) with a benzoyl radical were evaluated in terms of geometry and energy. The results were also interpreted with an expanded version of the Polanyi rules and the interaction/deformation theory. The deformation energy of methyl acrylate was found to be the smallest, and the bond formation index showed that the transition state in the methyl acrylate system forms early, and can easily reach the saddle point. The activity of the monomer was ascertained by charge analysis and was further confirmed by the reaction rate. Mayer bond order curves depicted the constantly changing chemical bonds during formation and dissociation. Reduced density gradient analysis showed a weak interaction between the monomer and the benzoyl radical.

Photo-Curing: UV Radiation curing of polymers

NASA Technical Reports Server (NTRS)

Inman, Christina A.

2004-01-01

The Polymers Branch of the Materials Division is dedicated to the development of high-performance for a variety of applications. Areas of significant interest include high- temperature polymers, low density, and high strength insulating materials, conductive polymers, and high density polymer electrolytes. This summer our group is working diligently on a photo-curing project. There is interest in the medical community feel the need for a new and improved balloon that will be used for angioplasty (a form of heart surgery). This product should maintain flexibility but add many other properties. Like possibly further processability and resistance to infection. Our group intends on coming up with this product by using photo-enolization (or simply, photo-curing) by Diels-Alder trapping. The main objective was to synthesize a series of new polymers by Diels-Alder cycloaddition of photoenols with more elastomeric properties. Our group was responsible for performing the proper photo-curing techniques of the polymers with diacrylates and bismaleimides, synthesizing novel monomers, and evaluating experimental results. We attempted to use a diacrylate to synthesize the polymer because of previous research done within the Polymers Branch here at NASA. Most acrylates are commercially available, have more elastometric properties than a typical rigid aromatic structure has and they contain ethylene oxides in the middle of their structure that create extensive flexibility. The problem we encountered with the acrylates is that they photo chemically and thermally self polymerize and create diradicals at low temperatures; these constraints caused a lot of unnecessary side reactions. We want to promote solely, diketone polymerization because this type of polymerization has the ability to cause very elastic polymers. We chose to direct our attention towards the usage of maleimides because they are known for eliminating these unnecessary side reactions.

Radiation cured polyester compositions containing metal-properties

NASA Astrophysics Data System (ADS)

Szalińska, H.; Pietrzak, M.; Gonerski, A.

The subject of the studies was unsaturated polyester resin, Polimal-109 and its compositions containing acrylates of: sodium, potassium, calcium, magnesium, barium, manganese, iron, cobalt, copper and acrylic acid. Polyester resin modified with acrylic acid salts was cured with 60Co gamma radiation. Measurements of Vicat softening temperature, water absorption, creep current resistance, volume and surface resistivity, the tangent of dielectric loss angle and permittivity of radiation cured compositions were carried out. The results of the studies presented testify to the fact that the properties of cross-linked polymers alter after ionogenic compounds have been introduced into them.

Effect of polymerization method and fabrication method on occlusal vertical dimension and occlusal contacts of complete-arch prosthesis.

PubMed

Lima, Ana Paula Barbosa; Vitti, Rafael Pino; Amaral, Marina; Neves, Ana Christina Claro; da Silva Concilio, Lais Regiane

2018-04-01

This study evaluated the dimensional stability of a complete-arch prosthesis processed by conventional method in water bath or microwave energy and polymerized by two different curing cycles. Forty maxillary complete-arch prostheses were randomly divided into four groups (n = 10): MW1 - acrylic resin cured by one microwave cycle; MW2 - acrylic resin cured by two microwave cycles: WB1 - conventional acrylic resin polymerized using one curing cycle in a water bath; WB2 - conventional acrylic resin polymerized using two curing cycles in a water bath. For evaluation of dimensional stability, occlusal vertical dimension (OVD) and area of contact points were measured in two different measurement times: before and after the polymerization method. A digital caliper was used for OVD measurement. Occlusal contact registration strips were used between maxillary and mandibular dentures to measure the contact points. The images were measured using the software IpWin32, and the differences before and after the polymerization methods were calculated. The data were statistically analyzed using the one-way ANOVA and Tukey test (α = .05). he results demonstrated significant statistical differences for OVD between different measurement times for all groups. MW1 presented the highest OVD values, while WB2 had the lowest OVD values ( P <.05). No statistical differences were found for area of contact points among the groups ( P =.7150). The conventional acrylic resin polymerized using two curing cycles in a water bath led to less difference in OVD of complete-arch prosthesis.

Designing an antibacterial acrylic resin using the cosolvent method -Effect of ethanol on the optical and mechanical properties of a cold-cure acrylic resin.

PubMed

Nezu, Takashi; Nagano-Takebe, Futami; Endo, Kazuhiko

2017-09-26

Antimicrobial cetylpyridinium chloride (CPC) has low miscibility with acrylic resin monomer but can be homogeneously mixed using ethanol as a cosolvent. This study investigated the effects of ethanol addition on the properties of a cold-cure acrylic resin. Ethanol was an excellent cosolvent for CPC and methyl methacrylate monomer (MMA), but the cured resin exhibited a strong change in coloration to yellow (ΔE* ab >8) and a drastically reduced bending strength (from 97 to 25 MPa) and elastic modulus (from 2.7 to 0.6 GPa) when equal volumes of ethanol and monomer were used together, possibly due to the solvation and deactivation of radicals by ethanol. However, these unfavorable effects diminished when the ethanol/MMA ratio was reduced to 0.25, and became smaller when each specimen was depressurized and excess ethanol was removed. Thus, it may be possible to develop a molecularly uniform antibacterial acrylic resin with acceptable color and strength using this simple technique.

TiO2-Nanofillers Effects on Some Properties of Highly- Impact Resin Using Different Processing Techniques.

PubMed

Aziz, Hawraa Khalid

2018-01-01

The criteria of conventional curing of polymethyl methacrylate do not match the standard properties of the denture base materials. This research was conducted to investigate the addition of TiO 2 nano practical on impact strength, thermal conductivity and color stability of acrylic resin cured by microwave in comparison to the conventional cured of heat-polymerized acrylic resin. 120 specimens made of high impact acrylic resin were divided into two main groups according to the type of curing (water bath, microwave), then each group was subdivided into two groups according to the addition of 3% TiO 2 nano-fillers and control group (without the addition of TiO 2 0%). Each group was subdivided according to the type of test into 3 groups with 10 specimens for each group. Data were statistically analyzed using Student t-test to detect the significant differences between tested and control groups at significance level ( P <0.05). According to curing type methods, the results showed that there was a significant decrease in impact strength of microwaved cured resin, but there was no significant difference in the thermal conductivity and color stability of resin. In addition, by using nanofiller, there was a significant increase in the impact strength and color stability with the addition of 3% TiO 2 nanofillers, but no significant difference was found in the thermal conductivity of the acrylic resin. The microwave curing of acrylic resin had no change in the color stability and thermal conductivity in comparison to the water bath, but the impact strength was decreased. The addition of 3% TiO 2 improved the impact and the color stability, but the thermal conductivity did not change.

Heat-cured acrylic resin versus light-activated resin: a patient, professional and technician-based evaluation of mandibular implant-supported overdentures.

PubMed

Asal, S A; Al-AlShiekh, H M

2017-12-01

Although light-activated resins (Eclipse) have been reported to possess superior physical and mechanical properties compared with the heat-cured acrylic resins (Lucitone-199), a few studies have compared overdentures with a locator attachment constructed from heat-cured acrylic resins with those constructed from light-activated resins. This clinical study was designed to compare the performance of a mandibular implant-supported overdenture constructed from a heat-cured acrylic resin (Lucitone-199) with that of an overdenture constructed from a light-activated resin (Eclipse). Ten participants received two identical mandibular implant-retained overdentures (Lucitone-199 and Eclipse) opposing one maxillary denture in a random order. Each mandibular overdenture was delivered and worn for 6 months, and two weeks of rest was advised between wears to minimize any carryover effects. Three questionnaires were devised. The first questionnaire (patient evaluation) focused on evaluating different aspects of the denture and overall satisfaction. The second questionnaire (professional dentist evaluation) was based on a clinical evaluation of soft tissues, complications, and the applied technique. The third questionnaire (technician evaluation) involved ranking the different manufacturing steps of the denture and overall preferences. The obtained data was statistically analyzed using an independent sample t-test and the Wilcoxon rank-sum test. The clinician and technician preferred the Eclipse dentures because of their technical aspects, whereas the patients preferred the Lucitone-199 dentures for their aesthetic properties. Implant-supported overdentures constructed from a heat-cured acrylic resin showed superior aesthetics and had a better odor compared with those constructed from a light-cured resin.

Fracture toughness of heat cured denture base acrylic resin modified with Chlorhexidine and Fluconazole as bioactive compounds.

PubMed

Al-Haddad, Alaa; Vahid Roudsari, Reza; Satterthwaite, Julian D

2014-02-01

This study investigated the impact of incorporating Chlorhexidine and Fluconazole as bioactive compounds on the fracture toughness of conventional heat cured denture base acrylic resin material (PMMA). 30 single edge-notched (SEN) samples were prepared and divided into three groups. 10% (mass) Chlorhexidine and 10% (mass) Diflucan powder (4.5% mass Fluconazole) were added to heat cured PMMA respectively to create the two study groups. A third group of conventional heat cured PMMA was prepared as the control group. Fracture toughness (3-point bending test) was carried out for each sample and critical force (Fc) and critical stress intensity factor (KIC) values measured. Data were subject to parametric statistical analysis using one-way ANOVA and Post hoc Bonferroni test (p=0.05). Fluconazole had no significant effect on the fracture toughness of the PMMA while Chlorhexidine significantly reduced the KIC and therefore affected the fracture toughness. When considering addition of a bioactive material to PMMA acrylic, Chlorhexidine will result in reduced fracture toughness of the acrylic base while Fluconazole has no effect. Copyright © 2013 Elsevier Ltd. All rights reserved.

Stress evolution in solidifying coatings

NASA Astrophysics Data System (ADS)

Payne, Jason Alan

The goal of this study is to measure, in situ, and control the evolution of stress in liquid applied coatings. In past studies, the stress in a coating was determined after processing (i.e., drying or curing). However, by observing a coating during drying or curing, the effects of processing variables (e.g., temperature, relative humidity, composition, etc.) on the stress state can be better determined. To meet the project goal, two controlled environment stress measurement devices, based on a cantilever deflection measurement principle, were constructed. Stress evolution experiments were completed for a number of coating systems including: solvent-cast homopolymers, tape-cast ceramics, aqueous gelatins, and radiation-cured multifunctional acrylates. In the majority of systems studied here, the final stresses were independent of coating thickness and solution concentration. Typical stress magnitudes for solvent-cast polymers ranged from zero to 18 MPa depending upon the pure polymer glass transition temperature (Tsb{g}), the solvent volatility, and additional coating components, such as plasticizers. Similar magnitudes and dependencies were observed in tape-cast ceramic layers. Stresses in gelatin coatings reached 50 MPa (due to the high Tsb{g} of the gelatin) and were highly dependent upon drying temperature and relative humidity. In contrast to the aforementioned coatings, stress in UV-cured tri- and tetrafunctional acrylate systems showed a large thickness dependence. For these materials, stress evolution rate and magnitude increased with photoinitiator concentration and with light intensity. Somewhat unexpectedly, larger monomer functionality led to greater stresses at faster rates even though the overall conversion fell. The stress magnitude and evolution rate at any stage in the solidification process are the result of a competition between shrinkage (due to drying, curing, etc.) and stress relaxation. A firm understanding of the mechanical, the thermal, and the microstructural properties of a coating is therefore necessary to properly study stress effects. Hence, observations from dynamic mechanical analysis, indentation, infrared spectroscopy, and optical microscopy were also studied in order to correlate coating properties (mechanical, thermal, and structural) to measured stresses.

An oxygen-insensitive degradable resist for fabricating metallic patterns on highly curved surfaces by UV-nanoimprint lithography.

PubMed

Hu, Xin; Huang, Shisong; Gu, Ronghua; Yuan, Changsheng; Ge, Haixiong; Chen, Yanfeng

2014-10-01

In this paper, an oxygen-insensitive degradable resist for UV-nanoimprint is designed, com-prising a polycyclic degradable acrylate monomer, 2,10-diacryloyloxymethyl-1,4,9,12-tetraoxa-spiro [4.2.4.2] tetradecane (DAMTT), and a multifunctional thiol monomer pentaerythritol tetra(3-mercaptopropionate) (PETMP). The resist can be quickly UV-cured in the air atmosphere and achieve a high monomer conversion of over 98%, which greatly reduce the adhesion force between the resist and the soft mold. High conversion, in company with an adequate Young's modulus (about 1 GPa) and an extremely low shrinkage (1.34%), promises high nanoimprint resolution of sub-50 nm. The cross-linked resist is able to break into linear molecules in a hot acid solvent. As a result, metallic patterns are fabricated on highly curved surfaces via the lift off process without the assistance of a thermoplastic polymer layer. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis, Characterization, and Visible Light Curing Capacity of Polycaprolactone Acrylate

PubMed Central

Tzeng, Jy-Jiunn; Hsiao, Yi-Ting; Wu, Yun-Ching; Chen, Hsuan; Lee, Shyh-Yuan

2018-01-01

Polycaprolactone (PCL) is drawing increasing attention in the field of medical 3D printing and tissue engineering because of its biodegradability. This study developed polycaprolactone prepolymers that can be cured using visible light. Three PCL acrylates were synthesized: polycaprolactone-530 diacrylate (PCL530DA), glycerol-3 caprolactone triacrylate (Glycerol-3CL-TA), and glycerol-6 caprolactone triacrylate (Glycerol-6CL-TA). PCL530DA has two acrylates, whereas Glycerol-3CL-TA and Glycerol-6CL-TA have three acrylates. The Fourier transform infrared and nuclear magnetic resonance spectra suggested successful synthesis of all PCL acrylates. All are liquid at room temperature and can be photopolymerized into a transparent solid after exposure to 470 nm blue LED light using 1% camphorquinone as photoinitiator and 2% dimethylaminoethyl methacrylate as coinitiator. The degree of conversion for all PCL acrylates can reach more than 80% after 1 min of curing. The compressive modulus of PCL530DA, Glycerol-3CL-TA, and Glycerol-6CL-TA is 65.7 ± 12.7, 80.9 ± 6.1, and 32.1 ± 4.1 MPa, respectively, and their compressive strength is 5.3 ± 0.29, 8.3 ± 0.18, and 3.0 ± 0.53 MPa, respectively. Thus, all PCL acrylates synthesized in this study can be photopolymerized and because of their solid structure and low viscosity, they are applicable to soft tissue engineering and medical 3D printing. PMID:29854803

Polyurethane-acrylate-based hydrophobic film: Facile fabrication, characterization, and application

NASA Astrophysics Data System (ADS)

Park, Jongsung; Nguyen, Bui Quoc Huy; Kim, Ji-Kwan; Shanmugasundaram, Arunkumar; Lee, Dong-Weon

2018-06-01

Polyurethane-acrylate (PUA) is a versatile UV-curable polymer with a short curing time at room temperature, whose surface structure can be flexibly modified by applying various micropatterns. In this paper, we propose a facile and cost-effective fabrication method for the continuous production of an optically transparent PUA-based superhydrophobic thin film. Poly(dimethylsiloxane) (PDMS) was employed as a soft mold for the fabrication of PUA films through the roll-to-roll technique. In addition, nanosilica was spray-coated onto the PUA surface to further improve the hydrophobicity. The fabricated PUA thin film showed the highest static water contact angle (WCA) of ∼140°. The high durability of the PUA film was also demonstrated through mechanical impacting tests. Furthermore, only ∼2% of voltage loss was observed in the solar panel covered with the PUA-based superhydrophobic film. These obtained results indicate the feasibility of applying the film as a protective layer in applications requiring a high transparency and a self-cleaning effect.

Study of the effects of adding Yttrium oxide particles in some physical, thermal, and mechanical properties of heat-curing acrylic resin

NASA Astrophysics Data System (ADS)

Khalil, Bassam I.; Gharkan, Mohammed R.; Ali, Ahmed H.

2018-05-01

Extensively use of hot-curing acrylic in prosthetic dentistry field, increase the needed to modifying its mechanical, thermal, and physical properties. In this work Yttrium oxide had added with different weight fractions, (5%, 10%, 15% and 20%), as reinforcement phase on purpose of developing these properties. Tensile strength, hardness, density, water adsorption, and thermal conductivity had been investigated for prepared composite specimens. The results show that the maximum tensile strength was at (10) % wt. of Y2O3 addition, (19) %more than that of plain acrylic, maximum hardness was at (15) % wt. of Y2O3 addition, (8.5) % more than that of plain acrylic, maximum density was at (20) % wt. of Y2O3 addition, (18.2) % more than that of plain acrylic, maximum decrease in water absorption was at (10) % wt. of Y2O3 addition, (29) % less than that of plain acrylic. Finally the maximum thermal conductivity was at (20) % wt. of Y2O3 addition, (16) % more than that of plain acrylic.

Induction Curing of Thiol-acrylate and Thiolene Composite Systems

PubMed Central

Ye, Sheng; Cramer, Neil B.; Stevens, Blake E.; Sani, Robert L.; Bowman, Christopher N.

2011-01-01

Induction curing is demonstrated as a novel type of in situ radiation curing that maintains most of the advantages of photocuring while eliminating the restriction of light accessibility. Induction curing is utilized to polymerize opaque composites comprised of thiol-acrylate and thiol-ene resins, nanoscale magnetic particles, and carbon nanotubes. Nanoscale magnetic particles are dispersed in the resin and upon exposure to the magnetic field, these particles lead to induction heating that rapidly initiates the polymerization. Heat transfer profiles and reaction kinetics of the samples are modeled during the reactions with varying induction heater power, species concentration, species type and sample thickness, and the model is compared with the experimental results. Thiol-ene polymerizations achieved full conversion between 1.5 minutes and 1 hour, depending on the field intensity and the composition, with the maximum reaction temperature decreasing from 146 – 87 °C when the induction heater power was decreased from 8 – 3 kW. The polymerization reactions of the thiol-acrylate system were demonstrated to achieve full conversion between 0.6 and 30 minutes with maximum temperatures from 139 to 86 °C. The experimental behavior was characterized and the temperature profile modeled for the thiol-acrylate composite comprised of sub100nm nickel particles and induction heater power in the range of 32 to 20 kW. A 9°C average deviation was observed between the modeling and experimental results for the maximum temperature rise. The model also was utilized to predict reaction temperatures and kinetics for systems with varying thermal initiator concentration, initiator half-life, monomer molecular weight and temperature gradients in samples with varying thickness, thereby demonstrating that induction curing represents a designable and tunable polymerization method. Finally, induction curing was utilized to cure thiol-acrylate systems containing carbon nanotubes where 1 wt% carbon nanotubes resulted in systems where the storage modulus increased from 17.6 ± 0.2 to 21.6 ± 0.1 MPa and an electrical conductivity that increased from <10−7 to 0.33 ± 0.5 S/m. PMID:21765552

(Meth)Acrylate Occupational Contact Dermatitis in Nail Salon Workers: A Case Series.

PubMed

DeKoven, Samuel; DeKoven, Joel; Holness, D Linn

Recently, many cases of acrylate-associated allergic contact dermatitis have appeared among nail salon workers. Common acrylate-containing products in nail salons include traditional nail polish, ultraviolet-cured shellac nail polish, ultraviolet-cured gel nails, and press-on acrylic nails. Nail salon technicians seen in the occupational medicine clinic in 2015 and 2016 were identified, and their patch test results and clinical features were summarized. Patch testing was done with the Chemotechnique (Meth)Acrylate nail series, and either the North American Standard series or the North American Contact Dermatitis Group screening series. Six patients were identified, all women, ages 38 to 58. Common presentations included erythematous dermatitis of the dorsa of the hands, palms, and forearms and fissures on the fingertips. Less common sites of eruptions included the periorbital region, cheeks, posterior ears, neck, sacral area, lateral thighs, and dorsa of the feet. All patients reacted to hydroxyethyl methacrylate, and 5 patients reacted to ethyl acrylate. Each patient also reacted to (meth)acrylates that are not found on either standard series, including ethyleneglycol dimethacrylate, 2-hydroxypropyl methacrylate, and 2-hydroxyethyl acrylate. The authors report 6 cases of allergic contact dermatitis to acrylates in nail technicians seen over the past year, representing a new trend in their clinic. These cases are reflective of a growing trend of nail technicians with allergic contact dermatitis associated with occupational (meth)acrylate exposure. Efforts to improve prevention are needed.

A Durable Airfield Marking System.

DTIC Science & Technology

1985-06-01

Resin is Mixed with the Black Curing Agent to Form the Epoxy Adhesive ..... ........... 17 14 The Gray Adhesive (White Resin Mixed with Black Curing...rubber 100 0 Polyester (peroxide-catalyzed) 100 0 Urethane 100 0 Epoxy polyamide 100 0 Acrylic latex (TT-P-1952) 100 0 Thermoplastic Tapes Type 1 100 0...suzmarrizes cost data co1parisons for traffic marking tapes, CAS tiles, fluorocarbon composites (Teflon ),and acrylic latex paint TT-P-1952. 8 -p °’. TABLE 2

Surface roughness of denture bases after immersion in fishcake vinegar solution

NASA Astrophysics Data System (ADS)

Kodir, K.; Tanti, I.; Odang, R. W.

2017-08-01

Fishcake is a common food in Palembang city and is usually eaten with fishcake vinegar sauce. Fishcake vinegar solution contains acetic acid and chloride and fluoride ions, all of which cause surface roughness on the denture base material. The objective of this study was to analyze the effect of fishcake vinegar solution on the surface roughness of heat-cured acrylic resin, thermoplastic nylon, and cobalt-chromium alloy denture bases. This laboratory-based experimental study was performed on heat-cured acrylic resins, thermoplastic nylon specimen plates formed in 15 × 10 × 1 mm shapes, and cobalt-chromium alloy specimens in cylinder forms with a 7.7 mm diameter and 17.5-mm height. Each group consisted of 10 pieces. Each specimen was immersed in a fishcake vinegar solution at 37 °C for 4 days. The surface roughness was measured using a profilometer before and after immersion. Statistical analyses showed significant (p < 0.05) changes in heat-cured acrylic resin, thermoplastic nylon, and the cobalt chromium alloy plates after immersion in a fishcake vinegar solution for 4 days. Fishcake vinegar solution affects the surface roughness of heat-cured acrylic resin, thermoplastic nylon, and cobalt-chromium alloy plates after a 4-day immersion period. The greatest surface roughness change occurred in the thermoplastic nylon plate, while the lowest change occurred in the cobalt-chromium alloy.

Inhibitory effect of zirconium oxide nanoparticles on Candida albicans adhesion to repaired polymethyl methacrylate denture bases and interim removable prostheses: a new approach for denture stomatitis prevention

PubMed Central

Gad, Mohammed M; Al-Thobity, Ahmad M; Shahin, Suliman Y; Alsaqer, Badar T; Ali, Aiman A

2017-01-01

Background Despite drawbacks, cold-cured acrylic resin is still the most common material used in denture repair. Zirconia nanoparticles were among the reinforcements added to increase the strength of the resin. The effect on Candida due to the addition of zirconia nanoparticles to the resin has not been investigated. Purpose The aim of this study was to evaluate the effect of zirconia nanoparticles added to cold-cured acrylic resin on Candida albicans adhesion. Materials and methods A total of 120 acrylic resin specimens with dimensions measuring 22×10×2.5 mm3 were prepared and divided into two equal groups. One group (repair) comprised heat-polymerized specimens that were sectioned at the center and prepared to create a 2 mm repair area that was repaired with cold-cured resin reinforced with 0% wt, 2.5% wt, 5% wt, and 7.5% wt zirconia nanoparticles. The second group contained intact cold-cured acrylic resin specimens reinforced with 0% wt, 2.5% wt, 5% wt, and 7.5% wt zirconia nanoparticles. Specimens were incubated at 37°C in artificial saliva containing C. albicans, and the effect of zirconia nanoparticles on C. albicans was assessed using two methods: 1) a slide count method and 2) a direct culture test. Variations in the number of living Candida were observed in relation to the different concentrations of zirconia nanoparticles. Analysis of variance (ANOVA) and post hoc Tukey’s tests were performed for data analysis. If the P-value was ≤0.05, then the difference was considered as statistically significant. Results It was found that C. albicans adhesion to repaired specimens was significantly decreased by the addition of zirconia nanoparticles (P<0.00001) in comparison with the control group. Intact cold-cured groups and groups repaired with cold-cured resin reinforced with 7.5% wt zirconia nanoparticles showed the lowest Candida count. Tukey’s test showed a significant difference between the repaired group and the intact cold-cured group, while the later demonstrated a lower Candida count. Conclusion The addition of zirconia nanoparticles to cold-cured acrylic resin is an effective method for reducing Candida adhesion to repaired polymethyl methacrylate (PMMA) denture bases and cold-cured removable prosthesis. Clinical significance Based on the results of the current study, zirconia nanoparticles have an antifungal effect, which could be incorporated in the repair material for repairing denture bases and in PMMA removable prostheses as a possible approach for denture stomatitis prevention. PMID:28814859

Inhibitory effect of zirconium oxide nanoparticles on Candida albicans adhesion to repaired polymethyl methacrylate denture bases and interim removable prostheses: a new approach for denture stomatitis prevention.

PubMed

Gad, Mohammed M; Al-Thobity, Ahmad M; Shahin, Suliman Y; Alsaqer, Badar T; Ali, Aiman A

2017-01-01

Despite drawbacks, cold-cured acrylic resin is still the most common material used in denture repair. Zirconia nanoparticles were among the reinforcements added to increase the strength of the resin. The effect on Candida due to the addition of zirconia nanoparticles to the resin has not been investigated. The aim of this study was to evaluate the effect of zirconia nanoparticles added to cold-cured acrylic resin on Candida albicans adhesion. A total of 120 acrylic resin specimens with dimensions measuring 22×10×2.5 mm 3 were prepared and divided into two equal groups. One group (repair) comprised heat-polymerized specimens that were sectioned at the center and prepared to create a 2 mm repair area that was repaired with cold-cured resin reinforced with 0% wt, 2.5% wt, 5% wt, and 7.5% wt zirconia nanoparticles. The second group contained intact cold-cured acrylic resin specimens reinforced with 0% wt, 2.5% wt, 5% wt, and 7.5% wt zirconia nanoparticles. Specimens were incubated at 37°C in artificial saliva containing C. albicans , and the effect of zirconia nanoparticles on C. albicans was assessed using two methods: 1) a slide count method and 2) a direct culture test. Variations in the number of living Candida were observed in relation to the different concentrations of zirconia nanoparticles. Analysis of variance (ANOVA) and post hoc Tukey's tests were performed for data analysis. If the P -value was ≤0.05, then the difference was considered as statistically significant. It was found that C. albicans adhesion to repaired specimens was significantly decreased by the addition of zirconia nanoparticles ( P <0.00001) in comparison with the control group. Intact cold-cured groups and groups repaired with cold-cured resin reinforced with 7.5% wt zirconia nanoparticles showed the lowest Candida count. Tukey's test showed a significant difference between the repaired group and the intact cold-cured group, while the later demonstrated a lower Candida count. The addition of zirconia nanoparticles to cold-cured acrylic resin is an effective method for reducing Candida adhesion to repaired polymethyl methacrylate (PMMA) denture bases and cold-cured removable prosthesis. Based on the results of the current study, zirconia nanoparticles have an antifungal effect, which could be incorporated in the repair material for repairing denture bases and in PMMA removable prostheses as a possible approach for denture stomatitis prevention.

Flexural Strength of Polymethyl Methacrylate Repaired with Fiberglass.

PubMed

Golbidi, Fariba; Pozveh, Maryam Amini

2017-07-01

The purpose of this experimental study was to discover a method to increase the strength of repaired polymethyl methacrylate (PMMA) samples. In this experimental study, 40 specimens with the dimensions of 65×10×2.5mm 3 were fabricated using heat-curing acrylic resin. Sixteen specimens were repaired with fiberglass and self-curing PMMA, while 16 samples were repaired with self-curing PMMA. Eight specimens were left intact as the control group. Afterwards, the flexural strengths of the repaired and intact specimens were measured by three-point bending test in a universal testing machine. Data were analyzed with one-way analysis of variance (ANOVA) and Tukey's HSD and LSD tests. The level of significance was set at P<0.05. The mean flexural strength of the samples repaired with fiberglass was higher than that of the other repaired samples. However, the difference was statistically significant only with respect to the Meliodent group (P=0.008). Impregnated fiberglass could be used in the repair of denture bases to improve the flexural strength. In terms of the fracture site, it can be concluded that the lower flexural strength of the auto-polymerizing acryl compared to that of the heat-curing type was the main reason for the occurrence of fractures, rather than the weak bond between heat-curing and auto-polymerizing acrylic resins.

Evaluation of the surface roughness of three heat-cured acrylic denture base resins with different conventional lathe polishing techniques: A comparative study.

PubMed

Rao, Duggineni Chalapathi; Kalavathy, N; Mohammad, H S; Hariprasad, A; Kumar, C Ravi

2015-01-01

Surface roughness promotes adhesion and colonization of denture plaque. Therefore, it is important to know the effects of polishing and finishing on the surface roughness of various acrylic resin materials. To evaluate and compare the effects of different conventional lathe polishing techniques on heat cured acrylic resins in producing surface roughness. Three different commercially available heat-cured acrylic resin materials namely DPI, Meliodent and Trevalon Hi were selected. 30 Specimens of each acrylic material (30 x 3 = 90, 10 x 60 x 2mm) were prepared and divided into 5 groups, each group consisted of 6 Nos. of specimens per material(6x3=18) and were grouped as Group A(unfinished), Group B (finished), Group C (Polishing Paste), Group D (Polishing Cake) and Group E (Pumice and Gold rouge). The resulted surface roughness (μm) was measured using Perthometer and observed under Scanning Electron Microscope. The values obtained were subjected statistical analyses. Among the materials tested, better results were obtained with Trevalon Hi followed by Meliodent and DPI. Among the polishing methods used, superior results were obtained with universal polishing paste followed by polishing cake; Pumice and Gold rouge. Although Pumice and Gold rouge values produced greater roughness value, they were well within the threshold value of 0.2 mm.

[The effect of denture base resins coated with antibacterial coating on water sorption, solubility and monomer elution].

PubMed

Yang, Yang; Gong, Hai-Huan; Song, Ai-Yang; Feng, Dan; Jin, Jie; Zhu, Song

2015-02-01

To determine the influence of denture base resins coated with antibacterial coating on water sorption, solubility and monomer elution. The values of water sorption and solubility were measured according to YY 0270-2003 and gas chromatography was used to examine the leachability of 4 commercially available heat-cured acrylic resins between experimental group and control group. Degree of crosslinking of the experimental heat-cured acrylic denture bases we remeasured by soxhlet extraction method. The data was analyzed by 17.0 software package. The values of water sorption, solubility and monomer elution of experimental group were lower compared to the control group. Degree of crosslinking of Heraeus reins was the highest among the experimental heat-cured acrylic denture bases. There is a same trend among water sorption, degree of crosslinking and the monomer elution. When the degree of crosslinking increases, the values of water sorption and monomer elution decrease. Antibacterial coating can improve the comprehensive properties of the denture base resins.

Synthesis and characterization of UV-absorbing fluorine-silicone acrylic resin polymer

NASA Astrophysics Data System (ADS)

Lei, Huibin; He, Deliang; Guo, Yanni; Tang, Yining; Huang, Houqiang

2018-06-01

A series of UV-absorbing fluorine-silicone acrylic resin polymers containing different amount of UV-absorbent were successfully prepared by solution polymerization, with 2-[3-(2H-Benzotriazol-2-yl)-4-hydroxyphenyl] ethyl methacrylate (BHEM), vinyltrimethoxysilane (VTMS) and hexafluorobutyl methacrylate (HFMA) as modifying monomers. The acrylic polymers and the coatings thereof were characterized by Fourier transform infrared spectrum (FT-IR), X-ray photoelectron spectroscopy (XPS), Ultraviolet-visible (UV-vis) absorption spectrum, thermogravimetric analysis (TGA), water contact angle (CA) and Xenon lamp artificial accelerated aging tests. Results indicated that the resin exhibited high UV absorption performance as well as good thermal stability. The hydrophobicity of the coatings was of great improvement because of the bonded fluorine and silicone. Meanwhile, the weather-resistance was promoted through preferably colligating the protective effects of BHEM, organic fluorine and silicone. Also, a fitting formula about the weatherability with the BMHE content was tentatively proposed.

Effect of UV curing time on physical and electrical properties and reliability of low dielectric constant materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kao, Kai-Chieh; Cheng, Yi-Lung, E-mail: yjcheng@ncnu.edu.tw; Chang, Wei-Yuan

2014-11-01

This study comprehensively investigates the effect of ultraviolet (UV) curing time on the physical, electrical, and reliability characteristics of porous low-k materials. Following UV irradiation for various periods, the depth profiles of the chemical composition in the low-k dielectrics were homogeneous. Initially, the UV curing process preferentially removed porogen-related CH{sub x} groups and then modified Si-CH{sub 3} and cage Si-O bonds to form network Si-O bonds. The lowest dielectric constant (k value) was thus obtained at a UV curing time of 300 s. Additionally, UV irradiation made porogen-based low-k materials hydrophobic and to an extent that increased with UV curing time.more » With a short curing time (<300 s), porogen was not completely removed and the residues degraded reliability performance. A long curing time (>300 s) was associated with improved mechanical strength, electrical performance, and reliability of the low-k materials, but none of these increased linearly with UV curing time. Therefore, UV curing is necessary, but the process time must be optimized for porous low-k materials on back-end of line integration in 45 nm or below technology nodes.« less

Short communication: pre- and co-curing effect of adhesives on shear bond strengths of composite resins to primary enamel and dentine: an in vitro study.

PubMed

Viswanathan, R; Shashibhushan, K K; Subba Reddy, V V

2011-12-01

To evaluate and compare shear bond strengths of composite resins to primary enamel and dentine when the adhesives are pre-cured (light cured before the application of the resin) or co-cured (adhesive and the resin light cured together). Buccal surfaces of 80 caries-free primary molars were wet ground to create bonding surfaces on enamel and dentine and specimens mounted on acrylic blocks. Two bonding agents (Prime and Bond NT® and Xeno III®) were applied to either enamel or dentine as per manufacturer's instructions. In 40 specimens, the bonding agent was light cured immediately after the application (pre-cured). The other 40 specimens were not light cured until the composite resin application (co-cured). Resin composite cylinders were made incrementally using acrylic moulds over the adhesives and light cured. Specimens were stored in deionised water for 24 hours at room temperature. Shear bond strength was measured using an Instron universal testing machine (in MPa) and was analysed with Student's unpaired t test. Light curing the adhesive separately produced significantly higher bond strengths to primary dentine than co-curing (p<0.001). At the same time light curing the adhesive separately did not produce significantly different bond strengths to primary enamel (p>0.05). Curing sequence had no significant effect on shear bond strength of adhesives on the primary enamel. Pre-curing adhesives before curing composite resins produced greater shear bond strength to primary dentine.

Flexural Strength of Polymethyl Methacrylate Repaired with Fiberglass

PubMed Central

Golbidi, Fariba

2017-01-01

Objectives: The purpose of this experimental study was to discover a method to increase the strength of repaired polymethyl methacrylate (PMMA) samples. Materials and Methods: In this experimental study, 40 specimens with the dimensions of 65×10×2.5mm3 were fabricated using heat-curing acrylic resin. Sixteen specimens were repaired with fiberglass and self-curing PMMA, while 16 samples were repaired with self-curing PMMA. Eight specimens were left intact as the control group. Afterwards, the flexural strengths of the repaired and intact specimens were measured by three-point bending test in a universal testing machine. Data were analyzed with one-way analysis of variance (ANOVA) and Tukey’s HSD and LSD tests. The level of significance was set at P<0.05. Results: The mean flexural strength of the samples repaired with fiberglass was higher than that of the other repaired samples. However, the difference was statistically significant only with respect to the Meliodent group (P=0.008). Conclusions: Impregnated fiberglass could be used in the repair of denture bases to improve the flexural strength. In terms of the fracture site, it can be concluded that the lower flexural strength of the auto-polymerizing acryl compared to that of the heat-curing type was the main reason for the occurrence of fractures, rather than the weak bond between heat-curing and auto-polymerizing acrylic resins. PMID:29285033

Closed hollow bulb obturator--one-step fabrication: a clinical report.

PubMed

Buzayan, Muaiyed M; Ariffin, Yusnidar T; Yunus, Norsiah

2013-10-01

A method is described for the fabrication of a closed hollow bulb obturator prosthesis using a hard thermoforming splint material and heat-cured acrylic resin. The technique allowed the thickness of the thermoformed bulb to be optimized for weight reduction, while the autopolymerized seal area was covered in heat-cured acrylic resin, thus eliminating potential leakage and discoloration. This technique permits the obturator prosthesis to be processed to completion from the wax trial denture without additional laboratory investing, flasking, and processing. © 2013 by the American College of Prosthodontists.

Investigation of test methods, material properties, and processes for solar cell encapsulants

NASA Technical Reports Server (NTRS)

Willis, P. B.

1982-01-01

Technical investigations concerned the development of advanced cure chemistries for lamination type pottants; the continued evaluation of soil resistant surface treatments, and the results of an accelerated aging test program for the comparison of material stabilities. New compounds were evaluated for efficiency in curing both ethylene/vinyl acetate and ethylene/methyl acrylate pottants intended for vacuum bag lamination of solar cells. One compound in particular, designated Lupersol - TBEC (Lucidol Division of Pennwalt Corp.) was found to be unusually effective in promoting the rapid cure of both these materials. Formulation of these resins with TBEC resulted in compositions of very high gel content, lower temperatures of activation, and much lower cure times, even in the ethylene/methyl acrylate polymer that is more difficult to cure. It is expected that TBEC modified pottant formulations may permit the lamination/encapsulation step to be operated at lower temperatures, higher speed, higher throughput and a much wider tolerance for intentional or accidental variations in the cure schedule. An experimental program continued to determine the effectiveness of soil resistant coatings.

Preparation and characterization of a photocrosslinkable bioadhesive inspired by marine mussel.

PubMed

Xue, Jie; Wang, Tao; Nie, Jun; Yang, Dongzhi

2013-02-05

Synthetic adhesives inspired by marine mussel have attracted great attention due to its excellent water-resistance and good biocompatibility. In this study, a photocrosslinkable bioadhesive containing 3,4-Dihydroxy-l-phenylalanine (DOPA) functional group, which is central to curing mussel adhesive proteins, was prepared by ultraviolet (UV) irradiation of a new photocurable monomer ethylene glycol acrylate methacrylate-dopamine (EGAMA-DOPA) and a UV photocrosslinkable crosslinking agent poly(vinyl alcohol) (UV-PVA) derivative. The chemical structures of EGAMA-DOPA and UV-PVA were confirmed by Fourier Transform Infrared Reflection (FTIR) and (1)H NMR spectroscopy, respectively. The effects of UV light intensity, content of photoinitiator, EGAMA-DOPA and UV-PVA on the photopolymerization kinetics were studied, and the effects of the content of UV-PVA and temperature on the adhesive strength were also investigated. It was found that the higher UV light intensity, the faster polymerization rate and the higher final conversion that was the same as the trend of photoinitiator, EGAMA-DOPA and UV-PVA. And the adhesion strength measurement showed that, for gels with 30wt.% EGAMA-DOPA, the adhesion strength was obviously improved by about 150% with 3.0wt.% UV-PVA instead of pure PVA, and for gels containing 40wt.% EGAMA-DOPA, the adhesion strength sharply enhanced by 123% with increasing the content of UV-PVA from 1.0wt.% to 3.0wt.%. Cell attachment results showed good cell viability of L929 cell on the EGAMA-DOPA/UV-PVA adhesive gels. Thanks to its strong adhesion strength and good biocompatibility, such photocrosslinkable gels could be applied to the areas of biomedical field. Copyright © 2012 Elsevier B.V. All rights reserved.

Investigation of Ultraviolet Light Curable Polysilsesquioxane Gate Dielectric Layers for Pentacene Thin Film Transistors.

PubMed

Shibao, Hideto; Nakahara, Yoshio; Uno, Kazuyuki; Tanaka, Ichiro

2016-04-01

Polysilsesquioxane (PSQ) comprising 3-methacryloxypropyl groups was investigated as an ultraviolet (UV)-light curable gate dielectric-material for pentacene thin film transistors (TFTs). The surface of UV-light cured PSQ films was smoother than that of thermally cured ones, and the pentacene layers deposited on the UV-Iight cured PSQ films consisted of larger grains. However, carrier mobility of the TFTs using the UV-light cured PSQ films was lower than that of the TFTs using the thermally cured ones. It was shown that the cross-linker molecules, which were only added to the UV-light cured PSQ films, worked as a major mobility-limiting factor for the TFTs.

High-impact strength acrylic denture base material processed by autoclave.

PubMed

Abdulwahhab, Salwan Sami

2013-10-01

To investigate the effect of two different cycles of autoclave processing on the transverse strength, impact strength, surface hardness and the porosity of high-impact strength acrylic denture base material. High Impact Acryl was the heat-cured acrylic denture base material included in the study. A total of 120 specimens were prepared, the specimens were grouped into: control groups in which high-impact strength acrylic resins processed by conventional water-bath processing technique (74°C for 1.5 h then boil for 30 min) and experimental groups in which high-impact strength acrylic resins processed by autoclave at 121°C, 210 kPa .The experimental groups were divided into (fast) groups for 15 min, and (slow) groups for 30 min. To study the effect of the autoclave processing (Tuttnauer 2540EA), four tests were conducted transverse strength (Instron universal testing machine), impact strength (Charpy tester), surface hardness (shore D), and porosity test. The results were analyzed to ANOVA and LSD test. In ANOVA test, there were highly significant differences between the results of the processing techniques in transverse, impact, hardness, and porosity test. The LSD test showed a significant difference between control and fast groups in transverse and hardness tests and a non-significant difference in impact test and a highly significant difference in porosity test; while, there were a highly significant differences between control and slow groups in all examined tests; finally, there were a non-significant difference between fast and slow groups in transverse and porosity tests and a highly significant difference in impact and hardness tests. In the autoclave processing technique, the slow (long) curing cycle improved the tested physical and mechanical properties as compared with the fast (short) curing cycle. The autoclave processing technique improved the tested physical and mechanical properties of High Impact Acryl. Copyright © 2013 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

Swelling of Superabsorbent Poly(Sodium-Acrylate Acrylamide) Hydrogels and Influence of Chemical Structure on Internally Cured Mortar

NASA Astrophysics Data System (ADS)

Krafcik, Matthew J.; Erk, Kendra A.

Superabsorbent hydrogel particles show promise as internal curing agents for high performance concrete (HPC). These gels can absorb and release large volumes of water and offer a solution to the problem of self-dessication in HPC. However, the gels are sensitive to ions naturally present in concrete. This research connects swelling behavior with gel-ion interactions to optimize hydrogel performance for internal curing, reducing the chance of early-age cracking and increasing the durability of HPC. Four different hydrogels of poly(sodium-acrylate acrylamide) are synthesized and characterized with swelling tests in different salt solutions. Depending on solution pH, ionic character, and gel composition, diffrerent swelling behaviors are observed. As weight percent of acrylic acid increases, gels demonstrate higher swelling ratios in reverse osmosis water, but showed substantially decreased swelling when aqueous cations are present. Additionally, in multivalent cation solutions, overshoot peaks are present, whereby the gels have a peak swelling ratio but then deswell. Multivalent cations interact with deprotonated carboxylic acid groups, constricting the gel and expelling water. Mortar containing hydrogels showed reduced autogenous shrinkage and increased relative humidity.

Real Time-NIR/MIR-Photorheology: A Versatile Tool for the in Situ Characterization of Photopolymerization Reactions.

PubMed

Gorsche, Christian; Harikrishna, Reghunathan; Baudis, Stefan; Knaack, Patrick; Husar, Branislav; Laeuger, Joerg; Hoffmann, Helmuth; Liska, Robert

2017-05-02

In photopolymerization reactions, mostly multifunctional monomers are employed, as they ensure fast reaction times and good final mechanical properties of the cured materials. Drawing conclusions about the influence of the components and curing conditions on the mechanical properties of the subsequently formed insoluble networks is challenging. Therefore, an in situ observation of chemical and mechanical characteristics during the photopolymerization reaction is desired. By coupling of an infrared spectrometer with a photorheometer, a broad spectrum of different photopolymerizable formulations can be analyzed during the curing reaction. The rheological information (i.e., time to gelation, final modulus, shrinkage force) can be derived from a parallel plate rheometer equipped with a UV- and IR-translucent window (glass for NIR and CaF 2 window for MIR). Chemical information (i.e., conversion at the gel point and final conversion) is gained by monitoring the decrease of the corresponding IR-peak for the reactive monomer unit (e.g., C═C double bond peak for (meth)acrylates, H-S thiol and C═C double bond peak in thiol-ene systems, C-O epoxy peak for epoxy resins). Depending on the relative concentration of reactive functional groups in the sample volume and the intensity of the IR signal, the conversion can be monitored in the near-infrared region (e.g., acrylate double bonds, epoxy groups) or the MIR region (e.g., thiol signal). Moreover, an integrated Peltier element and external heating hood enable the characterization of photopolymerization reactions at elevated temperatures, which also widens the window of application to resins that are waxy or solid at ambient conditions. By switching from water to heavy water, the chemical conversion during photopolymerization of hydrogel precursor formulations can also be examined. Moreover, this device could also represent an analytical tool for a variety of thermally and redox initiated systems.

Comparative evaluation of the amount of the residual monomer in conventional and deep-frozen heat cure polymethylmethacrylate acrylic resin: An in vitro study.

PubMed

Jadhav, Sonali S; Mahajan, Neerja; Sethuraman, Rajesh

2018-01-01

Heat cure acrylic resin material with reduced monomer content is generally recommended for clinical usage as it leads to improved mechanical, physical, and biocompatibility properties. The purpose of the present study was to evaluate and compare the amount of the residual monomer in the conventional and three different groups of deep-frozen heat cure polymethylmethacrylate (PMMA) acrylic resin. Totally 40 Specimens of heat cure PMMA acrylic resin (DPI India) (10 conventional heat cure and 30 deep frozen) were made using two disc-shaped stainless steel molds and invested into type II dental stone using compression molding technique. Each group contained 10 specimens ( n = 10). Group 1: Control group of conventional polished PMMA specimen stored in water for 24 h at +37°C (10 specimens), Group 2: Deep frozen unpolished PMMA (10 specimens), Group 3: Deep frozen polished PMMA (10 specimens), and Group 4: Deep frozen polished PMMA specimen stored in water for 24 h at +37°C (10 specimens). Amount of the residual monomer content in all the specimens was measured using high-performance liquid chromatography. Data were analyzed using One-Way Analysis of Variance and multiple comparison Tukey's post hoc test (α = 0.05). Least residual monomer content was found in Group 4 (0.12 wt%) followed by Group 3 (0.19 wt%), Group 2 (0.23 wt%), and Group 1 (0.26 wt%). Statistically significant difference ( P < 0.05) was found in residual monomer content for all the four groups tested. Post hoc test for intergroup comparison also showed a significant difference between groups. The amount of the residual monomer was found to be least in deep-frozen polished PMMA specimen stored in water for 24 h at +37°C (Group 4). Thus, it can be concluded that deep freezing, polishing, and storing in water can reduce the residual monomer content.

Preparation of carbon quantum dots based high photostability luminescent membranes.

PubMed

Zhao, Jinxing; Liu, Cui; Li, Yunchuan; Liang, Jiyuan; Liu, Jiyan; Qian, Tonghui; Ding, Jianjun; Cao, Yuan-Cheng

2017-06-01

Urethane acrylate (UA) was used to prepare carbon quantum dots (C-dots) luminescent membranes and the resultants were examined with FT-IR, mechanical strength, scanning electron microscope (SEM) and quantum yields (QYs). FT-IR results showed the polyurethane acrylate (PUA) prepolymer -C = C-vibration at 1101 cm -1 disappeared but there was strong vibration at1687cm -1 which was contributed from the-C = O groups in cross-linking PUA. Mechanical strength results showed that the different quantity of C-dots loadings and UV-curing time affect the strength. SEM observations on the cross-sections of the membranes are uniform and have no structural defects, which prove that the C-dots are compatible with the water-soluble PUA resin. The C-dot loading was increased from 0 to 1 g, the maximum tensile stress was nearly 2.67 MPa, but the tensile strain was decreased from 23.4% to 15.1% and 7.2% respectively. QYs results showed that the C-dots in the membrane were stable after 120 h continuous irradiation. Therefore, the C-dots photoluminescent film is the promising material for the flexible devices in the future applications. Copyright © 2016 John Wiley & Sons, Ltd.

Effects of Laboratory Disinfecting Agents on Dimensional Stability of Three Commercially Available Heat-Cured Denture Acrylic Resins in India: An In-Vitro Study

PubMed Central

Jujare, Ravikanth Haridas; Varghese, Rana Kalappattil; Singh, Vishwa Deepak; Gaurav, Amit

2016-01-01

Introduction Dental professionals are exposed to a wide variety of microorganisms which calls for use of effective infection control procedures in the dental office and laboratories that can prevent cross-contamination that could extend to dentists, dental office staff, dental technicians as well as patients. This concern has led to a renewed interest in denture sterilization and disinfection. Heat polymerized dentures exhibit dimensional change during disinfection procedure. Aim The purpose of this study was to determine the influence of different types of widely used laboratory disinfecting agents on the dimensional stability of heat-cured denture acrylic resins and to compare the dimensional stability of three commercially available heat-cured denture acrylic resins in India. Materials and Methods Twelve specimens of uniform dimension each of three different brands namely Stellon, Trevalon and Acralyn-H were prepared using circular metal disc. Chemical disinfectants namely 2% alkaline glutaraldehyde, 1% povidone-iodine, 0.5% sodium hypochlorite and water as control group were used. Diameter of each specimen was measured before immersion and after immersion with time interval of 1 hour and 12 hours. The data was evaluated statistically using one way analysis of variance. Results All the specimens in three disinfectants and in water exhibited very small amount of linear expansion. Among three disinfectants, specimens in 2% alkaline glutaraldehyde exhibited least(0.005mm) and water showed highest (0.009mm) amount of dimensional change. Among resins, Trevalon showed least (0.067mm) and Acralyn-H exhibited highest (0.110mm) amount of dimensional change. Conclusion Although, all the specimens of three different brands of heat-cured denture acrylic resins exhibited increase in linear dimensional change in all the disinfectants and water, they were found to be statistically insignificant. PMID:27134996

Color stability and marginal integrity of interim crowns: An in vitro study

PubMed Central

Elagra, Marwa I.; Rayyan, Mohammad R.; Alhomaidhi, Maisam M.; Alanaziy, Areej A.; Alnefaie, Mona O.

2017-01-01

Objective: Many commercial dental materials are used to fabricate interim restorations. This study aimed to compare the color stability and the marginal integrity of four different interim crown materials. Materials and Methods: An ivorine right maxillary central incisor was prepared for a full coverage all-ceramic restoration. A total of 36 specimens in the form of crowns were fabricated on the master die using four different materials (n = 9); Polymethyl methacrylate (PMMA) resin (TrimPLUS), PMMA computer-aided design, and computer-aided manufacturing (CAD-CAM) blocks (Ceramill TEMP), cold cure bis-acryl resin (Success CD), and bis-acryl resin dual-cure composite (TempSpan). Color change ΔE for each sample was calculated by measuring its color as Commission Internationale de l’Eclairage L* a* b* with a spectrophotometer before and after immersing in a concentrated tea solution for 7 days. Marginal gap was measured at four reference points using stereomicroscope at ×40. One-way ANOVA and the Tukey multiple comparisons test were used to determine any statistically significant difference between the four groups, (α = 0.05). Results: Success CD showed significantly the greatest color change (7.7) among all the tested materials, while no significant difference was found between the other three materials. TempSpan showed significantly the highest marginal gap formation (430.15 μm), while no significant difference was found between the three other materials. Conclusions: Bis-acryl resin composite materials demonstrated clinically noticeable change in color while PMMA materials demonstrated superior color stability. Dual cure interim materials exhibited significantly higher marginal discrepancy in comparison to PMMA and cold cure bis-acrylic resin materials. CAD-CAM PMMA material exhibited the best color stability and marginal integrity. PMID:28932142

An In vitro evaluation of the reliability of QR code denture labeling technique.

PubMed

Poovannan, Sindhu; Jain, Ashish R; Krishnan, Cakku Jalliah Venkata; Chandran, Chitraa R

2016-01-01

Positive identification of the dead after accidents and disasters through labeled dentures plays a key role in forensic scenario. A number of denture labeling methods are available, and studies evaluating their reliability under drastic conditions are vital. This study was conducted to evaluate the reliability of QR (Quick Response) Code labeled at various depths in heat-cured acrylic blocks after acid treatment, heat treatment (burns), and fracture in forensics. It was an in vitro study. This study included 160 specimens of heat-cured acrylic blocks (1.8 cm × 1.8 cm) and these were divided into 4 groups (40 samples per group). QR Codes were incorporated in the samples using clear acrylic sheet and they were assessed for reliability under various depths, acid, heat, and fracture. Data were analyzed using Chi-square test, test of proportion. The QR Code inclusion technique was reliable under various depths of acrylic sheet, acid (sulfuric acid 99%, hydrochloric acid 40%) and heat (up to 370°C). Results were variable with fracture of QR Code labeled acrylic blocks. Within the limitations of the study, by analyzing the results, it was clearly indicated that the QR Code technique was reliable under various depths of acrylic sheet, acid, and heat (370°C). Effectiveness varied in fracture and depended on the level of distortion. This study thus suggests that QR Code is an effective and simpler denture labeling method.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pern, F.J.; Glick, S.H.; Czanderna, A.W.

Results from extensive studies of the commercial ethylene vinyl acetate (EVA) formulations show that the UV absorber and curing-generated UV-excitable, {alpha},{beta}-unsaturated carbonyl chromophores facilitate the EVA discoloration, which is further enhanced by curing-generated acetic acid and probably residual peroxide curing agent also. Formation and concentration of the UV-excitable chromophores are substantially promoted by the antioxidant, Naugard P. The discoloration rate is greater under higher UV light intensity and temperatures. Heating in the dark at elevated temperatures (e.g., 85&hthinsp;{degree}C) in the air for {approximately}200 days only results in light yellowing. The discoloration reactions compete with photobleaching reactions, which destroy curing-generated chromophoresmore » and result in non-discoloring of EVA. By using better performance stabilizers to minimize the curing-generated UV-excitable chromophores, a new fast curing agent, and no UV absorber, the NREL-developed EVA formulations show a superior photothermal stability against browning to the commercial counterparts. Alternatively, the discoloration rate of the commercial EVA pottants can be considerably reduced by using UV-filtering glass superstrates that largely inhibit the UV-induced photooxidation reactions, or completely eliminated by using air-permeable polymer superstrate films that enable photobleaching reactions. {copyright} {ital 1999 American Institute of Physics.}« less

[Development of visible-light cured FRP denture].

PubMed

Yu, P Y

1990-06-01

Acrylic denture may be fractured easily because it has a relatively poor resistance to stresses of impact, and the thick acrylic denture base also uncomforted to denture wearers. In this study, for improvement of the mechanical properties, the FRP is applied to the denture base, and try to make a thin denture base. Using the visible light-curing system, the laboratory fabrication time is saved dramatically. To develop the visible light-cured FRP denture base, with various combination of matrix resins and reinforcements, the physical properties of FRP plates were investigated first. From the results of the bending test, hardness test, and manipulation considering, the sateen weave's glasscloth was choose as the reinforcement of the prepreg. The matrix resin of Bis-GMA/UDMA/3G at 48/48/4 wt% was determined. The 3 plies glasscloth included FRP plate is 0.8 mm thickness has the maximum bending strength about 50 kgf/mm2, which is about 5 times larger than that of acrylic resin. Succeeding the study of above, the FRP denture base was fabricated by using the 0.8 mm thickness 3 plies included prepreg. This repreg is manufactured in sheet form beforehand, which is ease to manipulate at laboratory. By using the visible light curing system, it is only taken 10 min. to make a FRP denture base. The following procedures of fabricating a FRP denture is the same as metalplate denture. The visible-light cured FRP denture has some advantages such as accuracy of fit, ease of fabrication and manipulation, and only 0.8 mm thickness but has superior strength.

Effects of gold nanoparticles on the electro-optical properties of a polymer dispersed liquid crystal

NASA Astrophysics Data System (ADS)

Hinojosa, A.; Shive, C.; Sharma, Suresh

2010-03-01

We have studied the electro-optical properties of a polymer-dispersed liquid crystal (PDLC) as functions of relative concentrations of gold nanoparticles. PDLC samples were synthesized between indium-tin-oxide (ITO) coated glass slides, separated by SiO2 spacers, by using liquid crystal E44, a monofunctional acrylic oligomer (CN135), and a tetrafunctional crosslinker (SR295). A UV photoinitiator (SR1124) was used to facilitate the curing of the monomer exposed to UV radiation from a Hg spectral lamp. A He-Ne laser was used to measure optical transmission through the PDLC as a function of applied ac electric field (1 kHz). The PDLC without gold nanoparticles shows the expected behavior; transmission through the PDLC increases from a minimum (opaque) to a maximum (transparent) with increasing electric field. The electro-optical behavior of the PDLC is altered significantly (e. g., relatively low switching field) upon addition of relatively low concentrations of gold nanoparticles into the starting PDLC syrup. We present electro-optical data as functions of gold nanoparticle concentration and discuss possible mechanism to understand our results.

Optical properties and indentation hardness of thin-film acrylated epoxidized oil

NASA Astrophysics Data System (ADS)

Rahman, Mohammad Syuhaimi Ab.; Shaktur, Khaled Mohamed; Mohammad, Rahmah; Zalikha, Wan Aimi; Nawi, Norwimie; Mohd, Ahmad Faiza

2012-02-01

Epoxy acrylate has been widely used as optical resin for applications such as cladding, the core of a waveguide, and other photonic devices. In this study, sustainable resin from edible oil was used as an alternative to epoxy acrylate. Structural features and the transmission of planar thin-film resin from an ultraviolet-visible spectroscopy (UV-VIS) spectrometer were investigated upon UV exposure. It was found that high transmission still persists for all samples with and without an UV absorber for exposed and unexposed samples. The film was found to absorb strongly below 400 nm. A change in the cut-off wavelength was observed upon exposure. Thin-film hardness and its dynamic indentation in the load-unload mode with different test forces were evaluated. Vickers hardness and the elastic modulus were determined for unacrylated epoxidized soybean oil (ESO) and acrylated epoxidized soybean oil (AESO). It was found that the AESO has a higher Vickers hardness and elastic modulus than those of unacrylated thin film. The Vickers hardness and elastic modulus were found to increase as the applied test force increased. The refractive index, thickness, and modes present were characterized from a spin-coated planar thin film. The refractive index in the transverse electric mode (TE) and transverse magnetic mode (TM) were determined and compared for unacrylated and acrylated epoxidized oil.

Acrylate Systemic Contact Dermatitis.

PubMed

Sauder, Maxwell B; Pratt, Melanie D

2015-01-01

Acrylates, the 2012 American Contact Dermatitis Society allergen of the year, are found in a range of products including the absorbent materials within feminine hygiene pads. When fully polymerized, acrylates are nonimmunogenic; however, if not completely cured, the monomers can be potent allergens.A 28-year-old woman is presented, who had her teeth varnished with Isodan (Septodont, Saint-Maur-des-Fossés, France) containing HEMA (2-hydroxyethyl methacrylate) with no initial reaction. Approximately 1 month later, the patient developed a genital dermatitis secondary to her feminine hygiene pads. The initial reaction resolved, but 5 months later, the patient developed a systemic contact dermatitis after receiving a second varnishing.The patient was dramatically patch test positive to many acrylates. This case demonstrates a reaction to likely unpolymerized acrylates within a feminine hygiene pad, as well as broad cross-reactivity or cosensitivity to acrylates, and possibly a systemic contact dermatitis with systemic re-exposure to unpolymerized acrylates.

Allergic contact dermatitis due to urethane acrylate in ultraviolet cured inks.

PubMed Central

Nethercott, J R; Jakubovic, H R; Pilger, C; Smith, J W

1983-01-01

Seven workers exposed to ultraviolet printing inks developed contact dermatitis. Six cases were allergic and one irritant. A urethane acrylate resin accounted for five cases of sensitisation, one of which was also sensitive to pentaerythritol triacrylate and another also to an epoxy acrylate resin. One instance of allergy to trimethylpropane triacrylate accounted for the sixth case of contact dermatitis in this group of workers. An irritant reaction is presumed to account for the dermatitis in the individual not proved to have cutaneous allergy by patch tests. In this instance trimethylpropane triacrylate was thought to be the most likely irritating agent. Laboratory investigation proved urethane acrylate to be an allergen. The results of investigations of the sensitisation potentials of urethane acrylate, methylmethacrylate, epoxy acrylate resins, toluene-2,4-diisocyanate, and other multifunctional acrylic monomers in the albino guinea pig are presented. The interpretation of such predictive tests is discussed. Images PMID:6223656

An In vitro evaluation of the reliability of QR code denture labeling technique

PubMed Central

Poovannan, Sindhu; Jain, Ashish R.; Krishnan, Cakku Jalliah Venkata; Chandran, Chitraa R.

2016-01-01

Statement of Problem: Positive identification of the dead after accidents and disasters through labeled dentures plays a key role in forensic scenario. A number of denture labeling methods are available, and studies evaluating their reliability under drastic conditions are vital. Aim: This study was conducted to evaluate the reliability of QR (Quick Response) Code labeled at various depths in heat-cured acrylic blocks after acid treatment, heat treatment (burns), and fracture in forensics. It was an in vitro study. Materials and Methods: This study included 160 specimens of heat-cured acrylic blocks (1.8 cm × 1.8 cm) and these were divided into 4 groups (40 samples per group). QR Codes were incorporated in the samples using clear acrylic sheet and they were assessed for reliability under various depths, acid, heat, and fracture. Data were analyzed using Chi-square test, test of proportion. Results: The QR Code inclusion technique was reliable under various depths of acrylic sheet, acid (sulfuric acid 99%, hydrochloric acid 40%) and heat (up to 370°C). Results were variable with fracture of QR Code labeled acrylic blocks. Conclusion: Within the limitations of the study, by analyzing the results, it was clearly indicated that the QR Code technique was reliable under various depths of acrylic sheet, acid, and heat (370°C). Effectiveness varied in fracture and depended on the level of distortion. This study thus suggests that QR Code is an effective and simpler denture labeling method. PMID:28123284

Application of Light-cured Dental Adhesive Resin for Mounting Electrodes or Microdialysis Probes in Chronic Experiments

PubMed Central

Okumura, Tetsu; Okanoya, Kazuo; Tani, Jun

2007-01-01

In chronic recording experiments, self-curing dental acrylic resins have been used as a mounting base of electrodes or microdialysis-probes. Since these acrylics do not bond to the bone, screws have been used as anchors. However, in small experimental animals like finches or mouse, their craniums are very fragile and can not successfully hold the anchors. In this report, we propose a new application of light-curing dental resins for mounting base of electrodes or microdialysis probes in chronic experiments. This material allows direct bonding to the cranium. Therefore, anchor screws are not required and surgical field can be reduced considerably. Past experiences show that the bonding effect maintains more than 2 months. Conventional resin's window of time when the materials are pliable and workable is a few minutes. However, the window of working time for these dental adhesives is significantly wider and adjustable. PMID:18997897

Fabrication of tough epoxy with shape memory effects by UV-assisted direct-ink write printing.

PubMed

Chen, Kaijuan; Kuang, Xiao; Li, Vincent; Kang, Guozheng; Qi, H Jerry

2018-03-07

3D printing of epoxy-based shape memory polymers with high mechanical strength, excellent thermal stability and chemical resistance is highly desirable for practical applications. However, thermally cured epoxy in general is difficult to print directly. There have been limited numbers of successes in printing epoxy but they suffer from relatively poor mechanical properties. Here, we present an ultraviolet (UV)-assisted 3D printing of thermally cured epoxy composites with high tensile toughness via a two-stage curing approach. The ink containing UV curable resin and epoxy oligomer is used for UV-assisted direct-ink write (DIW)-based 3D printing followed by thermal curing of the part containing the epoxy oligomer. The UV curable resin forms a network by photo polymerization after the 1st stage of UV curing, which can maintain the printed architecture at an elevated temperature. The 2nd stage thermal curing of the epoxy oligomer yields an interpenetrating polymer network (IPN) composite with highly enhanced mechanical properties. It is found that the printed IPN epoxy composites enabled by the two-stage curing show isotropic mechanical properties and high tensile toughness. We demonstrated that the 3D-printed high-toughness epoxy composites show good shape memory properties. This UV-assisted DIW 3D printing via a two-stage curing method can broaden the application of 3D printing to fabricate thermoset materials with enhanced tensile toughness and tunable properties for high-performance and functional applications.

Water-Base Coatings

DTIC Science & Technology

1974-11-01

reacted with hydroxypropyl methacrylate and 1-butanol modifier in butyl acrylate -isobutyl methacrylate reactive diluent mixture using dibutyltin dilaurate...disadvantages are: 1. only a few commercial systems (e. g., acrylic resins ) are available; 2. after application, the polymer must somehow be insolubilized...a bisphenol in the presence of an emulsifier and a water-miscible solvent (9); 2. emulsification of an epoxy resin -amine curing agent mixture , e.g

Effect of post-polymerization heat-treatments on degree of conversion, leaching residual MMA and in vitro cytotoxicity of autopolymerizing acrylic repair resin.

PubMed

Bural, Canan; Aktaş, Esin; Deniz, Günnur; Ünlüçerçi, Yeşim; Kızılcan, Nilgün; Bayraktar, Gülsen

2011-11-01

This study evaluated the effect of post-polymerization heat-treatments on degree of conversion (DC), residual methyl methacrylate concentration (MMA(r)) and in vitro cytotoxicity of autopolymerizing acrylic repair resin. A total of 336 specimens were prepared by bench- and hydroflask-curing and subjected to post-polymerization heat-treatments: a) water immersion at 60°C for 30 min, b) microwaving at 500 W for 3 min, c) combined use of water immersion and microwaving d) no treatment (as control). Specimens were eluted in cell culture medium for 1, 2, 5 and 7 days. DC and MMA(r) in eluates were measured by FTIR spectrometry and HPLC, respectively. In vitro cytotoxicity of eluates on L-929 fibroblasts was determined by XTT assay. Data were statistically analyzed with Dunn's multiple comparison and Pearson correlation tests (p≤0.05). DC was highest (99.9%) in bench- and hydroflask-cured groups which were subjected to water immersion. At all elution periods, MMA(r) was detected in eluates of all treatment groups and were higher in bench-cured groups than hydro-flask cured groups. Cell proliferation values indicated slightly cytotoxic effect throughout 7 days; regardless of the curing method or post-polymerization treatment. The correlation between MMA(r) and cell proliferation was negative after elution of 1, 2, 5 days and was only statistically significant (p<0.05) at 5 days. At elution of 7 days, the correlation was positive with no significance. Post-polymerization heat-treatment of autopolymerizing acrylic repair resin by immersion in water at 60°C for 30 min is clinically recommended to improve the DC while reducing the leaching residual MMA. Copyright © 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Effect of the addition of silanated silica on the mechanical properties of microwave heat-cured acrylic resin.

PubMed

da Silva, Lucas H; Feitosa, Sabrina A; Valera, Marcia C; de Araujo, Maria A M; Tango, Rubens N

2012-06-01

The purpose of this study was to evaluate the flexural strength and Vickers hardness of a microwave energy heat-cured acrylic resin by adding different concentrations of silane surface-treated nanoparticle silica. Acrylic resin specimens with dimensions of 65 × 10 × 2.5 mm were formed and divided into five experimental groups (n = 10) according to the silica concentration added to the acrylic resin mass (weight %) prior to polymerisation : G1, without silica; G2, 0.1% silica; G3, 0.5% silica; G4, 1.0% silica; and G5, 5.0% silica. The specimens were submitted to a three-point flexural strength test and to the Vickers hardness test (HVN). The data obtained were statistically analysed by anova and the Tukey test (α = 0.05). Regarding flexural strength, G5 differed from the other experimental groups (G1, G2, G3 and G4) presenting the lowest mean, while G4 presented a significantly higher mean, with the exception of group G3. Regarding Vickers hardness, a decrease in values was observed, in which G1 presented the highest hardness compared with the other experimental groups. Incorporating surface-treated silica resulted in direct benefits in the flexural strength of the acrylic resin activated by microwave energy; however, similar results were not achieved for hardness. © 2012 The Gerodontology Society and John Wiley & Sons A/S.

Ultrasonic Coating and Holographic Exposure Technology. Phase 1

DTIC Science & Technology

2015-09-01

introducing plaques to cure, which allowed the UV lamps to warm up. Temperature inside the UV oven could reach 35 °C if left on continuously. Curing time for...the deposition of thin films using an ultrasonic spray coater and patterning of the films using an ultraviolet ( UV ) laser. The main objectives for...required, and include such items as a corona discharge device, a UV curing oven, hot plate, and jigging for optics that were fabricated at Revision. Test

A Study of the Curing and Flammability Properties of Bisphenol A Epoxy Diacrylate Resin Utilizing a Novel Flame Retardant Monomer, bis[di-acryloyloxyethyl]-p-tert-butyl-phenyl Phosphate

PubMed Central

Rwei, Syang-Peng; Chen, Yu-Ming; Chiang, Whe-Yi; Ting, Yi-Tien

2017-01-01

A UV-curable, flame-retardant monomer, DAPP (bis[di-acryloyloxyethyl]-p-tert-butyl-phenyl-phosphate), was synthesized based on BPDCP (4-tert-butylphenyl-dichloro phosphate) and HEA (2-hydroxy ethyl acrylate). DAPP was blended with regular bisphenol A epoxy acrylate (BAEA) in various ratios to yield various phosphorus contents. The TGA-IR (thermogravimetric analyzer interface with an infrared spectrometer) results demonstrate that compounding 30 mol % DAPP with BAEA significantly reduced the amount of released CO gas. In contrast, the peak intensity of CO2 is independent of phosphorus content. The limiting oxygen index (LOI), reaching the saturated value of 26, and the heat release rate (HRR) measured using a cone-calorimeter, 156.43 KW/m2, confirm the saturation point when 30 mol % DAPP was compounded into BAEA. A study of the kinetics of pyrolysis reveals that Ea decreases as the phosphorus content increases. Both the TGA-IR and pyrolysis results reveal that the phosphorus compound DAPP is easily decomposed during the initial stage of burning to form an insulating layer, which inhibits further burning of the resin and the consequent release of other flammable gases. PMID:28772562

The sensitizing capacity of multifunctional acrylates in the guinea pig.

PubMed

Björkner, B

1984-10-01

The multifunctional acrylates used in ultraviolet (UV) curable resins act as cross-linkers and "diluents". They are usually based on di(meth)acrylate esters of dialcohols or tri- and tetra-acrylate esters of polyalcohols. In UV-curable coatings, the most commonly used are pentaerythritol triacrylate (PETA), trimethylolpropane triacrylate (TMPTA) and 1,6-hexanediol diacrylate (HDDA). In other uses, such as dental composite resin materials, the dimethacrylic monomers based on n-ethylene glycol are the most useful. The sensitizing capacity of various multifunctional acrylates and their cross-reactivity pattern have been investigated with the guinea pig maximization test. The tests show that BUDA (1,4-butanediol diacrylate) and HDDA are moderate to strong sensitizers and that they probably cross-react with each other. The n-ethylene glycol diacrylates and methacrylates tested are weak or non-sensitizers. Tripropylene glycol diacrylate (TPGDA) is a moderate and neopentyl glycol diacrylate (NPGDA) a strong sensitizer, whereas neopentyl glycol dimethacrylate is a non-sensitizer. The commercial PETA is a mixture of pentaerythritol tri- and tetra-acrylate (PETA-3 and PETA-4). PETA-3 is a much stronger sensitizer than PETA-4. Simultaneous reactions were seen between PETA-3, PETA-4 and TMPTA. The oligotriacrylate OTA 480 is a moderate sensitizer, but no concomitant reactions were seen with PETA-3, PETA-4 or TMPTA. Of the multifunctional acrylates tested, the di- and triacrylic compounds should be regarded as potent sensitizers. The methacrylated multifunctional acrylic compounds are weak or non-sensitizers.

Color Stability of Heat-cure Acrylic Resin Subjected to Simulated Short-term Immersion in Fast-acting Denture Cleansers.

PubMed

Lohitha, K; Prakash, M; Gopinadh, A; Sai Sankar, A J; Sandeep, C H; Sreedevi, B

2016-01-01

Regular usage of denture cleansers is recommended in complete denture wearers for effective plaque control, and these cleansers alter the physical properties of acrylic resin over a period of time. Thus, an in vitro study was carried out to assess the effect of denture cleansers on the color stability of heat-cure denture base resin. The aim of the present study was to evaluate the effect of commercially available fast-acting denture cleansers on the color stability of heat-cure denture base resin at different time intervals. Thirty-six heat-cure acrylic resin (Ivoclar Triplex Hot-V) specimens are randomly allocated into four groups - Group A (distilled water as control); Group B (polident - 3 min); Group C (fixodent scope plus); and Group D (stain away plus) comprising of nine samples each. After recording the baseline values, the specimens were immersed in their respective cleansing solutions for a prescribed time interval. This procedure was repeated daily, and the color change (ΔE) was evaluated after 90 and 180 days interval using a colorimeter in a standard "Commission International de l'Eclairage" color system. Paired t -test and Dunnett's T3 test. All the groups exhibited a variable color change (ΔE) for an immersion period of 90 days. However, significant color differences ( P = 0.001) were noticed among the test groups after 180 days. The color change of denture base resin was greater for Group D followed by Groups B, C, and A respectively after 180 days of immersion. The ΔE values of all test groups increased with time.

Nanoindentation and surface roughness profilometry of poly methyl methacrylate denture base materials.

PubMed

Zafar, Muhammad Sohail; Ahmed, Naseer

2014-01-01

Polymers have a wide range of applications in dentistry. Poly methyl methacrylate (PMMA) is the most popular for making orthodontic retainers, dentures as well as synthetic teeth. Prior to clinical applications, the appliances are polished in the dental laboratory to achieve smooth, polished and comfortable surfaces. The objective of this study was to analyze the surface roughness profiles of PMMA dentures polished using two different approaches. In addition, the effects of ultrasonication and sandblasting were also evaluated on the fitting surface of PMMA dentures. This was an in vitro study using non-contact mode surface roughness profilometer and nano-indenter. Samples were polished using two different techniques (Standard and modified). Both cold cure and heat cure PMMA denture surfaces were evaluated for roughness, nanohardness and elastic modulus. The absolute hardness was recorded 297.72±19.04 MPa and 229.93±18.53 MPa for heat cured PMMA and cold cured PMMA. Manufactured acrylic teeth were harder (319.20±12.58 MPa) with an elastic modulus of (4.34±1.86 GPa). Modified polishing techniques (group 3) produced smoother surface. It was concluded that elastic moduli of acrylic tooth and heat cure PMMA is not very different. Surface treatments such as ultrasonication or sandblasting do not affect the roughness profiles of denture fitting surfaces.

Effects of adding methacrylate monomers on viscosity and mechanical properties of experimental light-curing soft lining materials based on urethane (meth)acrylate oligomers.

PubMed

Kanie, Takahito; Kadokawa, Akihiko; Arikawa, Hiroyuki; Fujii, Koichi; Ban, Seiji

2008-11-01

We investigated the viscosity and mechanical properties of experimental light-curing soft lining materials based on six commercially available urethane (meth)acrylate oligomers. The viscosities of the six oligomers were 1.9, 20.6, 26.8, 144.0, 185.3, and 8803.4 Pa*s at 25 degrees C. Two monomers (ethyl- and butyl-methacrylate) were added at 20 wt% to these oligomers to decrease the viscosity, resulting in viscosity reductions of 0.2 to 13.6 Pa*s for the six oligomers. The mechanical properties (compressive modulus, Shore A hardness, and tensile strength) were measured after two times light-polymerization for 3 min. The addition of the monomers to the oligomers only slightly changed the mechanical properties, in contrast to the large viscosity changes. Based on these results, it appears that the addition of ethyl- or butyl-methacrylate monomers is useful for decreasing the viscosity of experimental light-curing soft lining materials without changing their mechanical properties.

Tensile and shear bond strength of hard and soft denture relining materials to the conventional heat cured acrylic denture base resin: An In-vitro study.

PubMed

Lau, Mayank; Amarnath, G S; Muddugangadhar, B C; Swetha, M U; Das, Kopal Anshuraj Ashok Kumar

2014-04-01

The condition of the denture bearing tissues may be adversely affected by high stress concentration during function. Chairside Denture (Hard and Soft) reliners are used to distribute forces applied to soft tissues during function. Tensile and shear bond strength has been shown to be dependent on their chemical composition. A weak bond could harbor bacteria, promote staining and delamination of the lining material. To investigate tensile and shear bond strength of 4 different commercially available denture relining materials to conventional heat cured acrylic denture base resin. 4 mm sections in the middle of 160 Acrylic cylindrical specimens (20 mm x 8 mm) were removed, packed with test materials (Mollosil, G C Reline Soft, G C Reline Hard (Kooliner) and Ufi Gel Hard and polymerized. Specimens were divided into 8 groups of 20 each. Tensile and shear bond strength to the conventional heat cured acrylic denture base resin were examined by Instron Universal Tensile Testing Machine using the equation F=N/A (F-maximum force exerted on the specimen (Newton) and A-bonding area= 50.24 mm2). One-way ANOVA was used for multiple group comparisons followed by Bonferroni Test and Hsu's MCB for multiple pairwise comparisons to asses any significant differences between the groups. The highest mean Tensile bond strength value was obtained for Ufi Gel Hard (6.49+0.08 MPa) and lowest for G C Reline Soft (0.52+0.01 MPa). The highest mean Shear bond strength value was obtained for Ufi Gel Hard (16.19+0.1 MPa) and lowest for Mollosil (0.59+0.05 MPa). The Benferroni test showed a significant difference in the mean tensile bond strength and the mean shear bond strength when the two denture soft liners were compared as well as when the two denture hard liners were compared. Hsu's MCB implied that Ufi gel hard is better than its other closest competitors. The Tensile and Shear bond strength values of denture soft reliners were significantly lower than denture hard reliners. How to cite the article: Lau M, Amarnath GS, Muddugangadhar BC, Swetha MU, Das KA. Tensile and shear bond strength of hard and soft denture relining materials to the conventional heat cured acrylic denture base resin: An In-vitro study. J Int Oral Health 2014;6(2):55-61.

Continuous and scalable fabrication of bioinspired dry adhesives via a roll-to-roll process with modulated ultraviolet-curable resin.

PubMed

Yi, Hoon; Hwang, Insol; Lee, Jeong Hyeon; Lee, Dael; Lim, Haneol; Tahk, Dongha; Sung, Minho; Bae, Won-Gyu; Choi, Se-Jin; Kwak, Moon Kyu; Jeong, Hoon Eui

2014-08-27

A simple yet scalable strategy for fabricating dry adhesives with mushroom-shaped micropillars is achieved by a combination of the roll-to-roll process and modulated UV-curable elastic poly(urethane acrylate) (e-PUA) resin. The e-PUA combines the major benefits of commercial PUA and poly(dimethylsiloxane) (PDMS). It not only can be cured within a few seconds like commercial PUA but also possesses good mechanical properties comparable to those of PDMS. A roll-type fabrication system equipped with a rollable mold and a UV exposure unit is also developed for the continuous process. By integrating the roll-to-roll process with the e-PUA, dry adhesives with spatulate tips in the form of a thin flexible film can be generated in a highly continuous and scalable manner. The fabricated dry adhesives with mushroom-shaped microstructures exhibit a strong pull-off strength of up to ∼38.7 N cm(-2) on the glass surface as well as high durability without any noticeable degradation. Furthermore, an automated substrate transportation system equipped with the dry adhesives can transport a 300 mm Si wafer over 10,000 repeating cycles with high accuracy.

Dimensional accuracy of pickup implant impression: an in vitro comparison of novel modular versus standard custom trays.

PubMed

Simeone, Piero; Valentini, Pier Paolo; Pizzoferrato, Roberto; Scudieri, Folco

2011-01-01

The purpose of this in vitro study was to compare the dimensional accuracy of the pickup impression technique using a modular individual tray (MIT) and using a standard individual tray (ST) for multiple internal-connection implants. The roles of both materials and geometric misfits were considered. First, because the MIT relies on the stiffness and elasticity of acrylic resin material, a preliminary investigation of the resin volume contraction during curing and polymerization was done. Then, two sets of specimens were tested to compare the accuracy of the MIT (test group) to that of the ST (control group). The linear and angular displacements of the transfer copings were measured and compared during three different stages of the impression procedure. Experimental measurements were performed with a computerized coordinate measuring machine. The curing dynamic of the acrylic resin was strongly dependent on the physical properties of the acrylic material and the powder/liquid ratio. Specifically, an increase in the powder/liquid ratio accelerated resin polymerization (curing time decreases by 70%) and reduced the final volume contraction by 45%. However, the total shrinkage never exceeded the elastic limits of the material; hence, it did not affect the coping's stability. In the test group, linear errors were reduced by 55% and angular errors were reduced by 65%. Linear and angular displacements of the transfer copings were significantly reduced with the MIT technique, which led to higher dimensional accuracy versus the ST group. The MIT approach, in combination with a thin and uniform amount of acrylic resin in the pickup impression technique, showed no significant permanent distortions in multiple misalignment internal-connection implants compared to the ST technique.

Comparison of the protection effectiveness of acrylic polyurethane coatings containing bark extracts on three heat-treated North American wood species: Surface degradation

NASA Astrophysics Data System (ADS)

Kocaefe, Duygu; Saha, Sudeshna

2012-04-01

High temperature heat-treatment of wood is a very valuable technique which improves many properties (biological durability, dimensional stability, thermal insulating characteristics) of natural wood. Also, it changes the natural color of wood to a very attractive dark brown color. Unfortunately, this color is not stable if left unprotected in external environment and turns to gray or white depending on the wood species. To overcome this problem, acrylic polyurethane coatings are applied on heat-treated wood to delay surface degradations (color change, loss of gloss, and chemical modifications) during aging. The acrylic polyurethane coatings which have high resistance against aging are further modified by adding bark extracts and/or lignin stabilizer to enhance their effectiveness in preventing the wood aging behavior. The aging characteristic of this coating is compared with acrylic polyurethane combined with commercially available organic UV stabilizers. In this study, their performance on three heat-treated North American wood species (jack pine, quaking aspen and white birch) are compared under accelerated aging conditions. Both the color change data and visual assessment indicate improvement in protective characteristic of acrylic polyurethane when bark extracts and lignin stabilizer are used in place of commercially available UV stabilizer. The results showed that although acrylic polyurethane with bark extracts and lignin stabilizer was more efficient compared to acrylic polyurethane with organic UV stabilizers in protecting heat-treated jack pine, it failed to protect heat-treated aspen and birch effectively after 672 h of accelerated aging. This degradation was not due to the coating adhesion loss or coating degradation during accelerated aging; rather, it was due to the significant degradation of heat-treated aspen and birch surface beneath this coating. The XPS results revealed formation of carbonyl photoproducts after aging on the coated surfaces and chain scission of Csbnd N of urethane linkages.

Effect of Heat Treatment on the Physical Properties of Provisional Crowns during Polymerization: An in Vitro Study

PubMed Central

Mei, May L.; So, Sam Y. C.; Li, Hao; Chu, Chun-Hung

2015-01-01

This study concerned the effect of heat treatment during setting on the physical properties of four resin-based provisional restorative materials: Duralay (polymethyl methacrylate), Trim II (polyethyl methacrylate), Luxatemp (bis-acrylic composite), and Protemp 4 (bis-acrylic composite). Specimens were prepared at 23, 37, or 60 °C for evaluation of flexural strength, surface roughness, color change and marginal discrepancy. Flexural strength was determined by a three-point bending test. Surface profile was studied using atomic force microscopy. Color change was evaluated by comparing the color of the materials before and after placement in coffee. A travelling microscope helped prepare standardized crowns for assessment of marginal discrepancy. Flexural strength of all tested materials cured at 23 °C or 37 °C did not significantly change. The surface roughness and marginal discrepancy of the materials increased at 60 °C curing temperature. Marginal discrepancies, color stability, and other physical properties of materials cured at 23 °C or 37 °C did not significantly change. Flexural strength of certain provisional materials cured at 60 °C increased, but there was also an increase in surface roughness and marginal discrepancy. PMID:28788031

Computational study on UV curing characteristics in nanoimprint lithography: Stochastic simulation

NASA Astrophysics Data System (ADS)

Koyama, Masanori; Shirai, Masamitsu; Kawata, Hiroaki; Hirai, Yoshihiko; Yasuda, Masaaki

2017-06-01

A computational simulation model of UV curing in nanoimprint lithography based on a simplified stochastic approach is proposed. The activated unit reacts with a randomly selected monomer within a critical reaction radius. Cluster units are chained to each other. Then, another monomer is activated and the next chain reaction occurs. This process is repeated until a virgin monomer disappears within the reaction radius or until the activated monomers react with each other. The simulation model well describes the basic UV curing characteristics, such as the molecular weight distributions of the reacted monomers and the effect of the initiator concentration on the conversion ratio. The effects of film thickness on UV curing characteristics are also studied by the simulation.

The Effect of Different Chemical Surface Treatments of Denture Teeth on Shear Bond Strength: A Comparative Study

PubMed Central

Palekar, Umesh; Awinashe, Vaibav; Mishra, Sunil Kumar; Kawadkar, Abhishek; Rahangdale, Tripti

2014-01-01

Background: The development of better cross linked acrylic resin teeth has solved the problems related to wearing and discoloration of acrylic teeth. The same cross linking at ridge lap region acts as a double edge sword as it weakens the bond between denture base and tooth. Aim of Study: The purpose of study was to evaluate the effect of surface treatment on the bond strength of resin teeth to denture base resin using monomethyl methacrylate monomer and dichloromethane with no surface treatment acting as control. Settings and Design:Denture base cylinder samples in wax (n=180) were made with maxillary central incisor attached at 450 (JIST 6506). These samples were randomly and equally divided into three groups of 60 each. These specimens were then flasked, dewaxed as per the standard protocol. Materials and Methods: Before acrylization, ridge lap area was treated as follows: Group A- no surface treatment act as control, Group B treated with monomethyl methacrylate monomer, Group C treated with dichloromethane. Digitally controlled acryliser was used for acrylization as per manufacturer’s instructions and shear bond strength was tested on Universal Testing Machine (Servo Hydraulic, 50kN High Strain, BISS Research). Statistical Analysis used: Result was statistically analyzed with One-way analysis of variance (ANOVA) and Post-hoc ANOVA Tukey’s HSD test at 5% level of significance. Results: The application of dichloromethane showed increased bond strength between cross linked acrylic resin teeth and heat cure denture base resin followed by monomethyl methacrylate monomer and control group. Conclusion: The application of dichloromethane on the ridge lap surface of the resin teeth before packing of the dough into the mold significantly increased the bond strength between cross linked acrylic resin teeth and heat cure denture base resin. PMID:25121057

Peculiarities of the photoinitiator-free photopolymerization of pentabrominated and pentafluorinated aromatic acrylates and methacrylates.

PubMed

Daikos, Olesya; Naumov, Sergej; Knolle, Wolfgang; Heymann, Katja; Scherzer, Tom

2016-11-30

Pentabrominated and fluorinated aromatic (meth)acrylates as well as their non-halogenated counterparts have been studied with the aim to avoid conventional photoinitiators and to overcome some negative consequences related to their use. Therefore, RTIR spectroscopy, laser flash photolysis and GC/MS were utilized. Even low concentrations (1 to 5 wt%) of brominated (meth)acrylates in the model varnish lead to initiation of a photopolymerization reaction under exposure to UV light with λ > 300 nm. This is due to the fact that excitation of the aryl moiety leads to the homolysis of bromine-phenyl bonds with a high quantum yield of ∼0.15-0.3. Both, bromine radicals released from either ortho, meta or para position as well as the corresponding tetrabromoaryl radicals, may initiate the polymerization of brominated aromatic (meth)acrylates. In contrast, fluorinated aromatic (meth)acrylates undergo α-cleavage of the carboxyl group (as in the case of non-halogenated aromatic (meth)acrylates), if excitation of the acrylic double bonds is done with UV-C light (λ < 280 nm). Radical formation occurs with a comparable quantum yield of 0.1-0.22 (fluorinated) and 0.16-0.36 (non-halogenated compounds), despite the different pathway of fragmentation. Thus, in all cases the efficiency of initiation is comparable to conventional photoinitiators. Quantum chemical calculations of orbitals involved and of the Gibbs free energy of transients and products support the suggested reaction pathway.

Thermal degradation and morphological studies on raw and reinforced polyacrylic rubbers

NASA Astrophysics Data System (ADS)

Sasikala, A.; Kala, A.

2017-05-01

Poly acrylate rubbers (ACM) of today are saturated copolymers of monomeric acrylic esters and reactive cure site monomers. ACM elastomer have also found use in vibration damping due to its excellent resilience. Other applications include textiles, adhesives, and coatings. Two state of Poly acrylic raw and reinforced Rubber are analyzed using FTIR spectroscopy, Optical Microscopy, DSC and TGA measurements. With the objective of determined the mechanical strength, Thermal analysis on TGA and DSC studies show that, the thermal degradation temperature Tg of the sample material is obtained and activation energy is also calaulated by Broido, Horowitz - Metzger, Piloyan-Novikova and Coats Redfern methods which are found.

[Surface characteristics of the acrylic resins according to the polishing methods].

PubMed

Vitalariu, Anca Mihaela; Lazăr, Lenuţa; Buruiană, Tinca; Diaconu, Diana; Tatarciuc, Monica Silvia

2011-01-01

The objective of this study was to evaluate the effect of the polishing technique and glazing on the porosity of the dental resins. The studied resins were: Castapress/Vertex, Prothyl Hot/Zermack, Rapid Simplified/Vertex, Duracryl Plus/Spofa Dental, Vertex-Soft/Vertex, Superacryl Plus/Spofa Dental. Thirty specimens, five for every resin, of 50/25/2 cm in size were done. One surface of each sample was polished with extrahard tungsten carbide burs, the other surface being polished with extrahard extrafine and diamond burs. The final polishing was done using a conventional method: pumice, water and lathe bristle brush for 90 seconds, 1500 rpm and soft leather polishing wheel for 90 seconds, 3000 rpm. Twenty surfaces were glazed after polishing with Glaze/Bosworth. Vertex Soft specimens were not polished because this is a resilient material. Surface porosity of the acrylic resin specimens was measured by optical microscopy. The lowest porosity was obtained by conventional polishing combined with glazing techniques. No differences between glazed and non/glazed self-curing resin specimens were noticed, but there were differences between self-curing and heat-curing resins. Conventional lathe polishing method is an effective and reliable technique for polishing dental resins. Specimens of self-curing resin had a higher porosity than heat curing resin following the same surface treatment. Higher surface smoothness was obtained by conventional lathe polishing completed by glazing.

Biocatalytic synthesis of maltodextrin-based acrylates from starch and α-cyclodextrin.

PubMed

Kloosterman, Wouter M J; Spoelstra-van Dijk, Gerda; Loos, Katja

2014-09-01

Novel 2-(β-maltooligooxy)-ethyl (meth)acrylate monomers are successfully synthesized by CGTase from Bacillus macerans catalyzed coupling of 2-(β-glucosyloxy)-ethyl acrylate and methacrylate with α-cyclodextrin or starch. HPLC-UV analysis shows that the CGTase catalyzed reaction yields 2-(β-maltooligooxy)-ethyl acrylates with 1 to 15 glucopyranosyl units. (1) H NMR spectroscopy reveals that the β-linkage in the acceptor molecule is preserved during the CGTase catalyzed coupling reaction, whereas the newly introduced glucose units are attached by α-(1,4)-glycosidic linkages. The synthesized 2-(β-maltooligooxy)-ethyl acrylate monomers are successfully polymerized by aqueous free radical polymerization to yield the comb-shaped glycopolymer poly(2-(β-maltooligooxy)-ethyl acrylate). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

New inorganic/organic copolymers (ORMOCER{reg_sign}s) for dental applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wolter, H.; Storch, W.; Ott, H.

1994-12-31

Urethane and thioether (meth)acrylate alkoxysilanes have been used, as sol-gel precursors, for the preparation of a special family of inorganic/organic copolymers (ORMOCER{reg_sign}s). The basic silane type offers the following structural and synthetic possibilities for modifying the properties of the resulting copolymers: variation of the number of alkoxy groups, combination with other, different, sol-gel precursors, variation of the number of attached (meth)acrylate groups (1--5), and variation within the molecular segment (kind, structure and length) connecting the inorganic with the organic polymer structure. To achieve the additional organic polymer structure in the cured copolymer the use of different radically induced polymerization approachesmore » (UV-, visible light-, thermal- and redox induced) is possible. Taking the incorporation of fillers into account, the Young`s modulus of these copolymers is adjustable in a range of 1--17,000 MPa, and the thermal expansion coefficient in a range of 17--250{center_dot}10{sup {minus}6}{center_dot}K{sup {minus}1} (5--50 C). Other advantages are the low shrinkage (1--2,8 vol.-%), the high flexural strength (up to 160 MPa), and the high abrasion resistance. This new copolymer type seems to have significant potential for medical applications, especially as dental filling material to replace the currently used controversial amalgam fillings.« less

Effects of alpha-zirconium phosphate on thermal degradation and flame retardancy of transparent intumescent fire protective coating

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xing, Weiyi; Zhang, Ping; Song, Lei

2014-01-01

Graphical abstract: - Highlights: • A transparent intumescent fire protective coating was obtained by UV-cured technology. • OZrP could enhance the thermal stability and anti-oxidation of the coating. • OZrP could reduce the combustion properties of the coatings. - Abstract: Organophilic alpha-zirconium phosphate (OZrP) was used to improve the thermal and fire retardant behaviors of the phenyl di(acryloyloxyethyl)phosphate (PDHA)-triglycidyl isocyanurate acrylate (TGICA)-2-phenoxyethyl acrylate (PHEA) (PDHA-TGICA-PHEA) coating. The morphology of nanocomposite coating was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The effect of OZrP on the flame retardancy, thermal stability, fireproofing time and char formation of the coatingsmore » was investigated by microscale combustion calorimeter (MCC), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS) and scanning electric microscope (SEM). The results showed that by adding OZrP, the peak heat release rate and total heat of combustion were significantly reduced. The highest improvement was achieved with 0.5 wt% OZrP. XPS analysis indicated that the performance of anti-oxidation of the coating was improved with the addition of OZrP, and SEM images showed that a good synergistic effect was obtained through a ceramic-like layer produced by OZrP covered on the surface of char.« less

Synthesis of Programmable Main-chain Liquid-crystalline Elastomers Using a Two-stage Thiol-acrylate Reaction.

PubMed

Saed, Mohand O; Torbati, Amir H; Nair, Devatha P; Yakacki, Christopher M

2016-01-19

This study presents a novel two-stage thiol-acrylate Michael addition-photopolymerization (TAMAP) reaction to prepare main-chain liquid-crystalline elastomers (LCEs) with facile control over network structure and programming of an aligned monodomain. Tailored LCE networks were synthesized using routine mixing of commercially available starting materials and pouring monomer solutions into molds to cure. An initial polydomain LCE network is formed via a self-limiting thiol-acrylate Michael-addition reaction. Strain-to-failure and glass transition behavior were investigated as a function of crosslinking monomer, pentaerythritol tetrakis(3-mercaptopropionate) (PETMP). An example non-stoichiometric system of 15 mol% PETMP thiol groups and an excess of 15 mol% acrylate groups was used to demonstrate the robust nature of the material. The LCE formed an aligned and transparent monodomain when stretched, with a maximum failure strain over 600%. Stretched LCE samples were able to demonstrate both stress-driven thermal actuation when held under a constant bias stress or the shape-memory effect when stretched and unloaded. A permanently programmed monodomain was achieved via a second-stage photopolymerization reaction of the excess acrylate groups when the sample was in the stretched state. LCE samples were photo-cured and programmed at 100%, 200%, 300%, and 400% strain, with all samples demonstrating over 90% shape fixity when unloaded. The magnitude of total stress-free actuation increased from 35% to 115% with increased programming strain. Overall, the two-stage TAMAP methodology is presented as a powerful tool to prepare main-chain LCE systems and explore structure-property-performance relationships in these fascinating stimuli-sensitive materials.

Characterization and optimization of an inkjet-printed smart textile UV-sensor cured with UV-LED light

NASA Astrophysics Data System (ADS)

Seipel, S.; Yu, J.; Periyasamy, A. P.; Viková, M.; Vik, M.; Nierstrasz, V. A.

2017-10-01

For the development of niche products like smart textiles and other functional high-end products, resource-saving production processes are needed. Niche products only require small batches, which makes their production with traditional textile production techniques time-consuming and costly. To achieve a profitable production, as well as to further foster innovation, flexible and integrated production techniques are a requirement. Both digital inkjet printing and UV-light curing contribute to a flexible, resource-efficient, energy-saving and therewith economic production of smart textiles. In this article, a smart textile UV-sensor is printed using a piezoelectric drop-on-demand printhead and cured with a UV-LED lamp. The UVcurable ink system is based on free radical polymerization and the integrated UVsensing material is a photochromic dye, Reversacol Ruby Red. The combination of two photoactive compounds, for which UV-light is both the curer and the activator, challenges two processes: polymer crosslinking of the resin and color performance of the photochromic dye. Differential scanning calorimetry (DSC) is used to characterize the curing efficiency of the prints. Color measurements are made to determine the influence of degree of polymer crosslinking on the developed color intensities, as well as coloration and decoloration rates of the photochromic prints. Optimized functionality of the textile UV-sensor is found using different belt speeds and lamp intensities during the curing process.

Effect of Layering Methods, Composite Type, and Flowable Liner on the Polymerization Shrinkage Stress of Light Cured Dental Composites

DTIC Science & Technology

2011-08-01

composite (Z350 flowable: 3M ESPE), and a silorane-based composite (P90: 3M ESPE). Scotchbond multipurpose adhesive ( 3M ESPE) was applied prior to...syringe. Composites used for filling the cavities were a methacrylate-based universal hybrid composite (Z250: 3M ESPE, St. Paul, MN, USA), a flowable... adhesive was light cured for 10 s using a LED light curing unit (S10: 3M ESPE), and the light intensity was 1200 mW/cm 2 . An acrylic case with

The effect of mechanical and chemical polishing techniques on the surface roughness of denture base acrylic resins.

PubMed

Al-Rifaiy, Mohammed Q

2010-01-01

Smooth polished surface of dental prostheses is important to prevent bacterial colonization and plaque accumulation. The acrylic base of prosthodontic appliances needs to be adjusted by grinding which often alters the surface of the denture base. It is therefore important to know how different polishing techniques affect surface roughness of acrylic resin. The aim of this study was to evaluate the effect of mechanical polishing (MP) and chemical polishing (CP) on the surface roughness of heat cured (HC) and auto cured (AC) denture base acrylic resins. Sixty acrylic resin specimens (30 × 15 × 3 mm) were made for each of the two types of acrylic resins. Thirty HC specimens received mechanical conventional lathe polishing using cone with pumice slurry and soft brush with chalk powder. The other thirty HC specimens received chemical polishing by immersing in methyl-methacrylate monomer heated to 75 °C ± 1 °C for 10 s. The sixty AC specimens received mechanical and chemical polishing in the same manner. Surface roughness was measured using surface analyzing instrument in microns. The data were statistically analyzed by two-way analysis of variance (ANOVA) followed by post hoc Tukey's test (α = 0.05). THE SURFACE ROUGHNESS MEAN IN MICRONS IN ORDER OF DECREASING VALUES WERE: CP-HC: 1.4132 μm; CP-AC: 1.3494 μm; MP-AC: 0.7364 μm and MP-HC: 0.6333 μm. Two-way ANOVA revealed that the MP-HC was significantly different from CP-HC and CP-AC (P < 0.05). The MP-AC is also significantly different from CP-HC and CP-AC (P < 0.05). There was no significant difference between MP and CP of HC and AC acrylic resin groups. It can be concluded that MP produced significantly smoother surfaces than CP. The surface roughness obtained by MP was not influenced by acrylic resin type where as this was not true for CP.

Development of a novel oxirane-acrylate composite restorative resin material

NASA Astrophysics Data System (ADS)

Sripathi Panditaradhyula, Anuhya

The need for resin with a long clinical life can be satiated through the novel formulation of varying concentrations of oxirane and acrylate monomers with an increase in filler loading in the sample, which will allow the creation of a resin that is less susceptible to chemical degradation along with improved mechanical properties. Various concentrations of oxirane and acrylate monomers with a three-component photoinitiation system, which is capable of both free radical (acrylate) and cationic (oxirane) initiation, are used. The resin composites were placed in the Speedmixer for 30 seconds and gravitation convection oven for one minute, repeated 5-7 times. The resin composites were used to create a 9.525 mm diameter * 1.5875 mm thick resin mold. The mold was then photocured for twenty seconds on both sides using VALO blue LED light. The Rockwell hardness and shore D durometer hardness served as relative measures of bonding between the monomers. The ideal formulation of oxirane and acrylate concentrations were used to perform the Instron 3 point bend test, as well as contact angle determination. The goal is to identify a resin with a clinical life twice that of the resins being used in practice. Potential findings include ideal oxirane and acrylate concentrations with the highest shore D durometer hardness, Rockwell hardness, contact angle values, and Instron 3 point bend test values. Ideal color, transparency and properties of the resin are taken into account. Optimization of oxirane and acrylate monomers, impact while using various filler components (salination, number of fillers), filler particle size variations and variations in using different filler concentrations are observed. Results of using micro and nano-sized monomers are also studied. Addition of fluorinated acrylate monomer to the micro and nano composite was the next goal. A comparison of all the above stated compositions to the control group 70/30 BisTEG was done. A study on the degradation behavior of these specimens were done by placing the respective specimens in distilled water, ascorbic acid (pH=1.5) and NaOH (pH=13). These resins were not fully cured with filler apart from filled 25:75 oxirane: acrylate cured best. Replacing 4-(Octyloxy) phenyl] phenyl iodonium SbF6 (OPPI) with 4-Isopropyl-4'- methyldiphenyl iodonium Tetrakis (pentafluorophenyl borate (Borate) initiator enhanced 24hr oxirane cure. Formulations had greater hardness compared with the controls. The increase in hardness was due to Increase in oxirane functionality, Increase in filler loading and use of acrylate-salinated filler. Modulus and ultimate transverse strength are greater than controls, but did not have statistically significance energy to break. Thus, these composites are as tough as controls and less brittle. They have the higher hydrophobicity than BisGMA: TEGDMA controls. Furthermore, other means of increasing hydrophobicity was explored, because higher the hydrophobicity, higher the resistance to hydrolytic degradation. Further research observations, such as dynamic mechanical analysis, should be carried out in order to determine the molecular interactions and usage of multi-walled, white carbon nanotubes as filler material.

21 CFR 882.5300 - Methyl methacrylate for cranioplasty.

Code of Federal Regulations, 2010 CFR

2010-04-01

... methacrylate for cranioplasty. (a) Identification. Methyl methacrylate for cranioplasty (skull repair) is a self-curing acrylic that a surgeon uses to repair a skull defect in a patient. At the time of surgery...

Characterization of curing behavior of UV-curable LSR for LED embedded injection mold

NASA Astrophysics Data System (ADS)

Tae, Joon-Sung; Yim, Kyung-Gyu; Rhee, Byung-Ohk; Kwak, Jae B.

2016-11-01

For many applications, liquid silicone rubber (LSR) injection molding is widely used for their great design flexibility and high productivity. In particular, a sealing part for a mobile device such as smartphone and watch has been produced by injection molding. While thermally curable LSR causes deformation problem due to a high mold temperature, UV-curable LSR can be molded at room temperature, which has advantages for over-molding with inserts of temperature-sensitive materials. Ultraviolet light-emitting diodes (UV LEDs) have advantages such as a longer service life, a lower heat dissipation, and smaller size to equip into the mold than conventional halogen or mercury UV lamps. In this work, rheological behavior of UV-curable LSR during curing process was analyzed by UV LEDs available in the market. UV-LEDs of various wave lengths and intensities were tested. The steady shear test was applied to find the starting time of curing and the SAOS was applied to find the ending time of curing to estimate processing time. In addition, the hardness change with irradiation energy was compared with the rheological data to confirm the reliability of the rheological test.

The effect of ultra-violet light curing on the molecular structure and fracture properties of an ultra low-k material

NASA Astrophysics Data System (ADS)

Smith, Ryan Scott

As the gate density increases in microelectronic devices, the interconnect delay or RC response also increases and has become the limiting delay to faster devices. In order to decrease the RC time delay, a new metallization scheme has been chosen by the semiconductor industry. Copper has replaced aluminum as the metal lines and new low-k dielectric materials are being developed to replace silicon dioxide. A promising low-k material is porous organosilicate glass or p-OSG. The p-OSG film is a hybrid material where the silicon dioxide backbone is terminated with methyl or hydrogen, reducing the dielectric constant and creating mechanically weak films that are prone to fracture. A few methods of improving the mechanical properties of p-OSG films have been attempted-- exposing the film to hydrogen plasma, electron beam curing, and ultra-violet light curing. Hydrogen plasma and electron-beam curing suffer from a lack of specificity and can cause charging damage to the gates. Therefore, ultra-violet light curing (UV curing) is preferable. The effect of UV curing on an ultra-low-k, k~2.5, p-OSG film is studied in this dissertation. Changes in the molecular structure were measured with Fourier Transform Infrared Spectroscopy and X-ray Photoelectron Spectroscopy. The evolution of the molecular structure with UV curing was correlated with material and fracture properties. The material properties were film shrinkage, densification, and an increase in dielectric constant. From the changes in molecular structure and material properties, a set of condensation reactions with UV light are predicted. The connectivity of the film increases with the condensation reactions and, therefore, the fracture toughness should also increase. The effect of UV curing on the critical and sub-critical fracture toughness was also studied. The critical fracture toughness was measured at four different mode-mixes-- zero, 15°, 32°, and 42°. It was found that the critical fracture toughness increases with UV exposure for all mode mixes. The sub-critical fracture toughness was measured in Mode I and found to be insensitive to UV cure. A simple reaction rate model is used to explain the difference in critical and sub-critical fracture toughness.

A combinaison of UV curing technology with ATL process

NASA Astrophysics Data System (ADS)

Balbzioui, I.; Hasiaoui, B.; Barbier, G.; L'hostis, G.; Laurent, F.; Ibrahim, A.; Durand, B.

2017-10-01

In order to reduce the time and the cost of manufacturing composite, UV curing technology combined with automated tape placement process (ATL) based on reverse approach by working with a fixed head was studied in this article. First, a brief description of the developed head placement is presented. Mechanical properties are then evaluated by varying process parameters, including compaction force and tape placement speed. Finally, a parametric study is carried out to identify suitable materials and process parameters to manufacture a photo composite material with high mechanical performances. The obtained results show that UV curing is a very good alternative for thermal polymerization because of its fast cure speed due to less dependency on temperature.

Fabrication of a dye-doped liquid crystal light shutter by thermal curing of polymer

NASA Astrophysics Data System (ADS)

Yu, Byeong-Hun; Ji, Seong-Min; Kim, Jin-Hun; Huh, Jae-Won; Yoon, Tae-Hoon

2017-07-01

We report a thermal curing method for fabrication of a dye-doped polymer-stabilized liquid crystal (PSLC) light shutter, which can prevent the decrease in absorption and discoloration of the dye caused by the UV curing process. We found that the measured transmittance in the opaque state of a dye-doped PSLC cell fabricated by thermal curing was approximately 35% lower than that of a dye-doped PSLC cell fabricated by UV curing. Thermal curing can be an alternative approach for fabrication of a dye-doped PSLC light shutter which can be used to provide high visibility of a see-through display.

Fire-Retardant Decorative Inks For Aircraft Interiors

NASA Technical Reports Server (NTRS)

Kourtides, D. A.; Nir, Z.; Mikroyannidis, J. A.

1988-01-01

Report describes testing of commercial and experimental fire retardants for incorporation into acrylic printing inks used on aircraft-interior sandwich panels. Films of acrylic ink containing fire-retardant additives prepared by casting on glass plates. Solvent evaporated in vacuum, cast films cured at 80 to 100 degree C for 30 minutes in air-circulating oven. Thermochemical properties of films examined by thermogravimetric analysis and differential scanning calorimetry (DSC). Samples of inks cast on sheets of polyvinylfloride (PVF), and their limiting oxygen indices and smoke evolution measured.

Material and fabrication strategies for artificial muscles (Conference Presentation)

NASA Astrophysics Data System (ADS)

Spinks, Geoffrey M.

2017-04-01

Soft robotic and wearable robotic devices seek to exploit polymer based artificial muscles and sensor materials to generate biomimetic movements and forces. A challenge is to integrate the active materials into a complex, three-dimensional device with integrated electronics, power supplies and support structures. Both 3D printing and textiles technologies offer attractive fabrication strategies, but require suitable functional materials. 3D printing of actuating hydrogels has been developed to produce simple devices, such as a prototype valve. Tough hydrogels based on interpenetrating networks of ionicially crosslinked alginate and covalently crosslinked polyacrylamide and poly(N-isopropylacrylamide) have been developed in a form suitable for extrusion printing with UV curing. Combined with UV-curable and extrudable rigid acrylated urethanes, the tough hydrogels can be 3D printed into composite materials or complex shapes with multiple different materials. An actuating valve was printed that operated thermally to open or close the flow path using 6 parallel hydrogel actuators. Textile processing methods such as knitting and weaving can be used to generate assemblies of actuating fibres. Low cost and high performance coiled fibres made from oriented polymers have been used for developing actuating textiles. Similarly, braiding methods have been developed to fabricate new forms of McKibben muscles that operate without any external apparatus, such as pumps, compressors or piping.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nahum, T.; Dodiuk, H.; Dotan, A.

Superhydrophobic surfaces with contact angle (CA) >150 and sliding angle (SA) <10 have been aroused curiosity over the years due to their various applications. Superhydrophobicity can be obtained tailoring the chemistry and the roughness of the surface, mimicking the Lotus flower. Most superhydrophobic surfaces based on secondary bonding lose their roughness in harsh conditions and are unsuitable for practical applications. Photoreactive SiO{sub 2} nanoparticles (NPs) based on benzophenone (BP) can be a very effective tool for formation of reactive species that function as a molecular bridge by covalent bonding between the NP and any polymer matrix with C-C and C-Hmore » bonds. The present work focused on thermoset radiation curing urethane acrylate. Upon UV irradiation reactive excited nπ* triplet benzophenone species are formed and react through hydrogen abstraction to form ketyl radicals which interact with a radicals from the UV irradiated polymer matrix to yield covalent bonding. Roughness was achieved by dipping the substrate in SiO{sub 2}@BPs NPs dispersion followed by irradiation. Fluoroalkylsilane was used to obtain hydrophobic top layer. AFM nano manipulation was used to verify the immobilization of NPs. Evaluation of durability was made using air flow at 300 km/hr. Preliminary results indicate the formation of super hydrophobic surfaces (CA>150 and SA<10) with improved stability.« less

Synthesis and controlled self-assembly of UV-responsive gold nanoparticles in block copolymer templates.

PubMed

Song, Dong-Po; Wang, Xinyu; Lin, Ying; Watkins, James J

2014-11-06

We demonstrate the facile synthesis of gold nanoparticles (GNPs) functionalized by UV-responsive block copolymer ligands, poly(styrene)-b-poly(o-nitrobenzene acrylate)-SH (PS-b-PNBA-SH), followed by their targeted distribution within a lamellae-forming poly(styrene)-b-poly(2-vinylpyridine) (PS-b-P2VP) block copolymer. The multilayer, micelle-like structure of the GNPs consists of a gold core, an inner PNBA layer, and an outer PS layer. The UV-sensitive PNBA segment can be deprotected into a layer containing poly(acrylic acid) (PAA) when exposed to UV light at 365 nm, which enables the simple and precise tuning of GNP surface properties from hydrophobic to amphiphilic. The GNPs bearing ligands of different chemical compositions were successfully and selectively incorporated into the PS-b-P2VP block copolymer, and UV light showed a profound influence on the spatial distributions of GNPs. Prior to UV exposure, GNPs partition along the interfaces of PS and P2VP domains, while the UV-treated GNPs are incorporated into P2VP domains as a result of hydrogen bond interactions between PAA on the gold surface and P2VP domains. This provides an easy way of controlling the arrangement of nanoparticles in polymer matrices by tailoring the nanoparticle surface using UV light.

Polymerization speed and diffractive experiments in polymer network LC test cells

NASA Astrophysics Data System (ADS)

Braun, Larissa; Gong, Zhen; Habibpourmoghadam, Atefeh; Schafforz, Samuel L.; Wolfram, Lukas; Lorenz, Alexander

2018-02-01

Polymer-network liquid crystals (LCs), where the response properties of a LC can be enhanced by the presence of a porous polymer network, are investigated. In the reported experiments, liquid crystals were doped with a small amount (< 10%) of photo-curable acrylate monomers. Samples with surface grafted photoinitiators, dissolvable photoinitiators, and samples with both kinds of photoinitiators were prepared. Both conventional (planar electrodes) and diffractive (interdigitated electrodes) test cells were used. These samples were exposed with a UV light source and changes of their capacitance were investigated with an LCR meter during exposure. Due to the presence of the in-situ generated polymer network, the electro-optic response properties of photo cured samples were enhanced. For example, their continuous phase modulation properties led to more localized responses in samples with interdigitated electrodes, which caused suppression of selected diffraction orders in the diffraction patterns recorded in polymer network LC samples. Moreover, capacitance changes were investigated during photopolymerization of a blue phase LC.

Nonthermal combined ultraviolet and vacuum-ultraviolet curing process for organosilicate dielectrics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, H.; Guo, X.; Pei, D.

2016-06-13

Porous SiCOH films are of great interest in semiconductor fabrication due to their low-dielectric constant properties. Post-deposition treatments using ultraviolet (UV) light on organosilicate thin films are required to decompose labile pore generators (porogens) and to ensure optimum network formation to improve the electrical and mechanical properties of low-k dielectrics. The goal of this work is to choose the best vacuum-ultraviolet photon energy in conjunction with vacuum ultraviolet (VUV) photons without the need for heating the dielectric to identify those wavelengths that will have the most beneficial effect on improving the dielectric properties and minimizing damage. VUV irradiation between 8.3more » and 8.9 eV was found to increase the hardness and elastic modulus of low-k dielectrics at room temperature. Combined with UV exposures of 6.2 eV, it was found that this “UV/VUV curing” process is improved compared with current UV curing. We show that UV/VUV curing can overcome drawbacks of UV curing and improve the properties of dielectrics more efficiently without the need for high-temperature heating of the dielectric.« less

A development of visible light cured FRP plate denture.

PubMed

Kimura, H; Teraoka, F

1990-12-01

A FRP denture base, which was made from visible light curing prepreg, was developed. The visible light cured FRP denture base had advantages with respect to an adequate strength, bonding strength of acrylic base resin, esthetic properties and ease to manipulation. The matrix resin of Bis-GMA/UDMA/3 G at 48/48/4 was determined from the results of the bending test and manipulation processing. The sateen weave's glasscloth was used for the reinforcement of the prepreg. The adaptability of the FRP plate denture was better than that of the resin base denture constructed with microwave heating.

Synthesis and characterization of functionalized methacrylates for coatings and biomedical applications

NASA Astrophysics Data System (ADS)

Shemper, Bianca Sadicoff

The research presented in this dissertation involves the design of polymers for biomaterials and for coatings applications. The development of non-wettable, hard UV-curing, or reactive coatings is discussed. The biomaterials section involves the syntheses of linear and star-like polymers of the functionalized monomer poly(propylene glycol) monomethacrylate (PPGM) via atom transfer radical polymerization (ATRP) (Chapter II). Its copolymerization with a perfluoroalkyl ethyl methacrylate monomer (1H,1H,2H,2H-heptadecafluorodecyl methacrylate) and the syntheses of linear and star-like amphiphilic copolymers containing the fluorinated monomer and poly(ethyleneglycol) methyl ether methacrylate (MPEGMA) are discussed in Chapter III. The four-arm amphiphilic block copolymer obtained showed unique associative properties leading to micellization in selective solvents. Chapter IV includes research involving the design of films with low surface energy by incorporating fluorine into the polymer. The synthesis, characterization and polymerization of a perfluoroalkylether-substituted methacrylic acid (C8F7) are discussed, and the properties of coatings obtained after its photopolymerization on different substrates are evaluated to confirm formation of low-surface energy polymeric coatings. Subsequently, hard coatings based on methyl (alpha-hydroxymethyl)acrylate (MHMA) were prepared via photopolymerization using UV-light. Firstly, mechanistic investigations into the photopolymerization behavior of (alpha-hydroxymethyl)acrylates (RHMA's) are reported (Chapter V). RHMA derivatives were photopolymerized with various multifunctional acrylates and methacrylates and the effect of crosslinker type and degree of functionality on photopolymerization rates and conversions was investigated. Then, in Chapter VI the synthesis of a series of new crosslinkers is described and their photopolymerization kinetics was investigated in bulk. The effect of these novel crosslinkers on the photopolymerization kinetics and coatings properties of MHMA systems is then shown in Chapter VII. This chapter also includes the effect of the presence of synthetic clay in these systems and the preparation of nanocomposite-based films. The final chapter of this dissertation involves the design of reactive coatings for biomedical applications. The syntheses and characterization of novel functionalized methacrylates containing succinimide ester groups susceptible to derivatization with amine-containing species were accomplished. Photopolymerization of these monomers led to formation of hydrogels and derivatization of the hydrogel surfaces with the tripeptide RGD (arginine-glycine-aspartic acid) was successfully achieved.

Toughening epoxy acrylate with polyurethane acrylates and hyper-branched polyester in three dimensional printing

NASA Astrophysics Data System (ADS)

Fang, Chao; Li, Ning; Liu, Yang; Lu, Gang

2018-05-01

In order to improve the toughness of epoxy acrylate (EA) in three dimensional printing (3D-printing), bifunctional polyurethane acrylate (PUA) and trifunctional PUA were firstly blended with EA. The multi-indicators orthogonal experiment, designed with the indicators of tensile strength, elongation at break and impact strength, was used to find out the optimal formulation. Then, hyper-branched polyesters (HBPs) was added to improve the toughness of the photocurable system. The microstructures of the cured specimens were characterized by optical microscopy and scanning electron microscopy. By analyzing their mechanical properties and microstructures, it was revealed that the best addition amounts of HBP are 10 wt%. Results indicated that their toughness improved a lot comparing with pure EA. The changes of mechanical properties were characterized by DMA. The addition of HBP could cause a loss in stiffness, elasticity modulus and thermostability.

Solid freeform fabrication of biomaterials

NASA Astrophysics Data System (ADS)

Chu, Tien-Min Gabriel

1999-12-01

The biological performance of porous Hydroxyapatite (HA) is closely related to the pore architecture in the implants. The study on the effect of architecture to the biological performance of porous HA requires new manufacturing methods that can fabricate implants with controlled pores channels. In this thesis, four highly loaded HA and alumina suspensions were formulated and three different processes involving Solid Freeform Fabrication (SFF) were developed. An aqueous HA suspension in acrylamides was first formulated and the UV-curing properties were evaluated. With a medical grade HA powder, two non-aqueous HA suspensions were formulated: a 40 vol.% HA suspension in Hexanediol Diacrylate (HDDA) and a 40 vol.% HA suspension in 1:1 mix of Propoxylated Neopentyl Glycol Diacrylate (PNPGDA) and Isobomyl Acrylate (EBA). A 50 vol.% Alumina suspension in PNPGDA/IBA was also formulated. The effect of dispersant to the viscosity of the suspensions was characterized. In the Stereolithography (SL) method, the curing parameters of HA/HDDA and HA/PNPGDA/IBA were determined. Prototype HA implants with 1,700 mum internal channels were built directly on an SL Apparatus (SLA). The designed internal channel patterns were preserved after sintering. In the Ink-jet printing method, the high temperature flow behaviors of the suspensions were characterized. The effects of solids loading to the viscosity of the suspensions were modeled with Krieger-Dougherty equation. Leveling theory developed in paint industry was employed to analyze the self-leveling capability of the suspensions. In the indirect SL method, the thermal curing behavior of HA and alumina suspensions were characterized. The total cure time was measured and the curing kinetics was modeled. Negative molds for the implants were designed and built on SLA with epoxy resin. HA/PNPGDA/IBA was cast into the mold and cured in an oven. The binders and the epoxy mold were pyrolyzed and the green bodies sintered. Internal channels with sizes in the range of 420 to 968 gm with standard deviation less than 50 mum were successfully built. The formulation and characterization techniques developed in this thesis were useful for evaluating the suspensions for SFF process. The manufacturing process developed in this thesis have provided new methods for controlling the channel size in porous HA implants.

Synthesis and Characterization of a Novel Borazine-Type UV Photo-Induced Polymerization of Ceramic Precursors.

PubMed

Wei, Dan; Chen, Lixin; Xu, Tingting; He, Weiqi; Wang, Yi

2016-06-21

A preceramic polymer of B,B',B''-(dimethyl)ethyl-acrylate-silyloxyethyl-borazine was synthesized by three steps from a molecular single-source precursor and characterized by Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectrometry. Six-member borazine rings and acrylate groups were effectively introduced into the preceramic polymer to activate UV photo-induced polymerization. Photo-Differential Scanning Calorimetry (Photo-DSC) and real-time FTIR techniques were adapted to investigate the photo-polymerization process. The results revealed that the borazine derivative exhibited dramatic activity by UV polymerization, the double-bond conversion of which reached a maximum in 40 s. Furthermore, the properties of the pyrogenetic products were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD), which proved the ceramic annealed at 1100 °C retained the amorphous phase.

Rapid Prototyping of Composite Structures

NASA Technical Reports Server (NTRS)

Colton, Jonathan S.

1998-01-01

This progress report for the project Rapid Production of Composite Structures covers the period from July 14, 1997 to June 30, 1998. It will present a short overview of the project, followed by the results to date and plans for the future. The goal of this research is to provide a minimum 100x reduction in the time required to produce arbitrary, laminated products without the need for a separate mold or an autoclave. It will accomplish this by developing the science underlying the rapid production of composite structures, specifically those of carbon fiber-epoxy materials. This scientific understanding will be reduced to practice in a demonstration device that will produce a part on the order of 12" by 12" by 6". Work in the past year has focussed on developing an understanding of the materials issues and of the machine design issues. Our initial goal was to use UV cureable resins to accomplish full cure on the machine. Therefore, we have centered our materials work around whether or not UV cureable resins will work. Currently, the answer seems to be that they will not work, because UV light cannot penetrate the carbon fibers, and because no "shadow" curing seems to occur. As a result, non-UV cureable resins are being investigated. This has resulted in a change in the machine design focus. We are now looking into a "dip and place" machine design, whereby a prepreg layer would have one side coated with a curing agent, and then would be placed onto the previous layer. This would lead to cure at the interface, but not to the top of the layer. The formulation of the resins to accomplish this task at room or slightly elevated temperatures is being investigated, as is the machine design needed to apply the curing agent and then cure or partially cure the part. A final, out-of-autoclave, post-cure may be needed with this strategy, as final cure on the machine may not be possible, as it was for the initial UV cure strategy. The remainder of this report details the progress in the materials and machine design areas. Materials Development The material system must be designed to fulfill the following requirements: to reduce the time and labor requirements of typical cure cycles; to reduce the thermal stresses developed during conventional heat curing; and to develop a structure that the build sequence requires. In order to accomplish these goals, there have been parallel tracks of investigation. One area has tested photopolymerizable (ultraviolet (UV) curable) materials and combinations of these materials with standard heat curing resins. The second area has investigated resins that cure rapidly at room or low heat temperatures. The main goal of these investigations has been to identify a system that will rapidly set or cure at room temperature during a tape lay-up process and hold its structure during a post-cure cycle.

Bonding of acrylic denture teeth to MMA/PMMA and light-curing denture base materials: the role of conditioning liquids.

PubMed

Palitsch, Anne; Hannig, Matthias; Ferger, Paul; Balkenhol, Markus

2012-03-01

The connection between resin denture teeth and the denture base is essential for the integrity of partial and full dentures. The aim of the present study was to analyse the bond strength of acrylic denture teeth to two light curing denture base materials compared to the gold-standard (MMA/PMMA) using different conditioning liquids. The ridge laps of 220 identical denture teeth were ground and pre-treated using different conditioning liquids (MMA, an experimental conditioning liquid as well as the two commercially available liquids Palabond and Versyo.bond). The denture base materials (PalaXpress, Versyo.com, Eclipse) were applied using a split mould to obtain tensile bond strength specimens of identical shape. Ten specimens per test group were either stored in water for 24h or thermocycled (5000×, 5-55°C) prior to tensile bond strength testing (cross-head speed 10mm/min). Data was subjected to parametric statistics (α=0.05). The three-way ANOVA revealed a significant influence of the material, pre-treatment as well as the storage. PalaXpress showed the highest bond strength (24.3MPa) of all materials tested after TC, whereas the use of MMA led to the most constant results. Lower values were recorded for Versyo.com (17.5MPa) and Eclipse (10.4MPa) bonded with Versyo.bond. The results indicate that MMA/PMMA based denture base resins provide reliable and durable bond strength to acrylic denture teeth. Using light-curing denture base materials requires the application of appropriate conditioning liquids to obtain acceptable bond strength. The use of MMA affects bond strength to light-curing denture base materials. The pre-treatment of denture teeth is critical regarding their bond-strength to denture base materials and in turn for the integrity of removable full and partial dentures. Light-curing denture base resins are more sensitive to the correct tooth pre-treatment compared to conventional MMA/PMMA materials, requiring specific conditioning liquids. Copyright © 2011 Elsevier Ltd. All rights reserved.

Evaluation of an alternative technique to optimize direct bonding of orthodontic brackets to temporary crowns.

PubMed

Dias, Francilena Maria Campos Santos; Pinzan-Vercelino, Célia Regina Maio; Tavares, Rudys Rodolfo de Jesus; Gurgel, Júlio de Araújo; Bramante, Fausto Silva; Fialho, Melissa Nogueira Proença

2015-01-01

To compare shear bond strength of different direct bonding techniques of orthodontic brackets to acrylic resin surfaces. The sample comprised 64 discs of chemically activated acrylic resin (CAAR) randomly divided into four groups: discs in group 1 were bonded by means of light-cured composite resin (conventional adhesive); discs in group 2 had surfaces roughened with a diamond bur followed by conventional direct bonding by means of light-cured composite resin; discs in group 3 were bonded by means of CAAR (alternative adhesive); and discs in group 4 had surfaces roughened with a diamond bur followed by direct bonding by means of CAAR. Shear bond strength values were determined after 24 hours by means of a universal testing machine at a speed of 0.5 mm/min, and compared by analysis of variance followed by post-hoc Tukey test. Adhesive remnant index (ARI) was measured and compared among groups by means of Kruskal-Wallis and Dunn tests. Groups 3 and 4 had significantly greater shear bond strength values in comparison to groups 1 and 2. Groups 3 and 4 yielded similar results. Group 2 showed better results when compared to group 1. In ARI analyses, groups 1 and 2 predominantly exhibited a score equal to 0, whereas groups 3 and 4 predominantly exhibited a score equal to 3. Direct bonding of brackets to acrylic resin surfaces using CAAR yielded better results than light-cured composite resin. Surface preparation with diamond bur only increased shear bond strength in group 2.

Characterization of passive polymer optical waveguides

NASA Astrophysics Data System (ADS)

Joehnck, Matthias; Kalveram, Stefan; Lehmacher, Stefan; Pompe, Guido; Rudolph, Stefan; Neyer, Andreas; Hofstraat, Johannes W.

1999-05-01

The characterization of monomode passive polymer optical devices fabricated according to the POPCORN technology by methods originated from electron, ion and optical spectroscopy is summarized. Impacts of observed waveguide perturbations on the optical characteristics of the waveguide are evaluated. In the POPCORN approach optical components for telecommunication applications are fabricated by photo-curing of liquid halogenated (meth)acrylates which have been applied on moulded thermoplastic substrates. For tuning of waveguide material refractive indices with respect to the substrate refractive index frequently comonomer mixtures are used. The polymerization characteristics, especially the polymerization kinetics of individual monomers, determine the formation of copolymers. Therefore the unsaturation as function of UV-illumination time in the formation of halogenated homo- and copolymers has been examined. From different suitable copolymer system, after characterization of their glass transition temperatures, their curing behavior and their refractive indices as function of the monomer ratios, monomode waveguides applying PMMA substrates have been fabricated. To examine the materials composition also in the 6 X 6 micrometers 2 waveguides they have been visualized by transmission electron microscopy. With this method e.g. segregation phenomena could be observed in the waveguide cross section characterization as well. The optical losses in monomode waveguides caused by segregation and other materials induce defects like micro bubbles formed as a result of shrinkage have been quantized by return loss measurements. Defects causing scattering could be observed by convocal laser scanning microscopy and by conventional light microscopy.

Construction material

DOEpatents

Wagh, Arun S [Orland Park, IL; Antink, Allison L [Bolingbrook, IL

2008-07-22

A structural material of a polystyrene base and the reaction product of the polystyrene base and a solid phosphate ceramic is applied as a slurry which includes one or more of a metal oxide or a metal hydroxide with a source of phosphate to produce a phosphate ceramic and a poly (acrylic acid or acrylate) or combinations or salts thereof and polystyrene or MgO applied to the polystyrene base and allowed to cure so that the dried aqueous slurry chemically bonds to the polystyrene base. A method is also disclosed of applying the slurry to the polystyrene base.

Comparative evaluation of color change between two types of acrylic resin and flexible resin after thermo cycling. An in vitro study.

PubMed

Hatim, Nadira A; Al-Tahho, Omar Zeno

2013-09-01

Evaluation of the effect of different beverages (tea with sugar, coffee with sugar, and Pepsi), and immersion time cycles (2, 4, and 12 weeks) on color change property, and dimensional change of Vertex Dental BV, Netherlands heat cured acrylic resin, recently modified Vertex Dental BV, Netherlands heat cured acrylic resin with additive (20 % banana oil), and Valplast(®) flexible resin (FR) denture base materials by using artificial saliva cycle. The total samples of this study for color, and dimensional changes were 360 samples, divided into three groups according to the type of the material, Vertex Dental BV, Netherlands heat cured acrylic resin, modified heat cured acrylic resin (Vertex with additive 20 % banana oil), and Valplast(®) FR groups, each group contains 120 samples. The thermal cycling used in this study was as follows: The samples were incubated in distilled water at 37 ± 1 °C for 2 days for conditioning. Then, the samples were immersed in beverage solutions for 10 min daily at 50 ± 1 °C temperature for tea, and coffee with sugar, while for Pepsi at 20 ± 1 °C. Then, the samples were immersed in artificial saliva at 37 ± 1 °C for 5 h, and 10 min. This cycle was repeated three times daily, and then the samples were immersed in distilled water at 22 ± 2 °C room temperature for 8 h at night. This cycle was repeated for 2, 4, and 12 weeks. At the end of each time period, the immersed samples were tested to evaluate the color change property. Descriptive statistics, ANOVA, and Duncan's multiple range tests were used to analyze the collected data. The results of this study showed that, in comparison between the materials at different times for colors L*a*b* properties, there were significant differences at P ≤ 0.05 except in color b* at 12 weeks, which showed no significant difference at P > 0.05 between materials. And there was a significant difference in dimensional change at P > 0.05 for different beverages, and times of immersion. The largest color, and dimensional changes were observed in the Valplast(®) FR, whereas tea was found to be the most chromatic agent, and showed unaccepted color change (ΔE ≤ 3.7) in vitro study as compared with coffee, Pepsi, and artificial saliva solutions.

21 CFR 882.5030 - Methyl methacrylate for aneurysmorrhaphy.

Code of Federal Regulations, 2014 CFR

2014-04-01

... aneurysms, which are balloonlike sacs formed on blood vessels) is a self-curing acrylic used to encase and reinforce intracranial aneurysms that are not amenable to conservative management, removal, or obliteration by aneurysm clip. (b) Classification. Class II (performance standards). ...

21 CFR 882.5030 - Methyl methacrylate for aneurysmorrhaphy.

Code of Federal Regulations, 2013 CFR

2013-04-01

... aneurysms, which are balloonlike sacs formed on blood vessels) is a self-curing acrylic used to encase and reinforce intracranial aneurysms that are not amenable to conservative management, removal, or obliteration by aneurysm clip. (b) Classification. Class II (performance standards). ...

21 CFR 882.5030 - Methyl methacrylate for aneurysmorrhaphy.

Code of Federal Regulations, 2012 CFR

2012-04-01

... aneurysms, which are balloonlike sacs formed on blood vessels) is a self-curing acrylic used to encase and reinforce intracranial aneurysms that are not amenable to conservative management, removal, or obliteration by aneurysm clip. (b) Classification. Class II (performance standards). ...

Do flexible acrylic resin lingual flanges improve retention of mandibular complete dentures?

PubMed Central

Ahmed Elmorsy, Ayman Elmorsy; Ahmed Ibraheem, Eman Mostafa; Ela, Alaa Aboul; Fahmy, Ahmed; Nassani, Mohammad Zakaria

2015-01-01

Objectives: The aim of this study was to compare the retention of conventional mandibular complete dentures with that of mandibular complete dentures having lingual flanges constructed with flexible acrylic resin “Versacryl.” Materials and Methods: The study sample comprised 10 completely edentulous patients. Each patient received one maxillary complete denture and two mandibular complete dentures. One mandibular denture was made of conventional heat-cured acrylic resin and the other had its lingual flanges made of flexible acrylic resin Versacryl. Digital force-meter was used to measure retention of mandibular dentures at delivery and at 2 weeks and 45 days following denture insertion. Results: The statistical analysis showed that at baseline and follow-up appointments, retention of mandibular complete dentures with flexible lingual flanges was significantly greater than retention of conventional mandibular dentures (P < 0.05). In both types of mandibular dentures, retention of dentures increased significantly over the follow-up period (P < 0.05). Conclusions: The use of flexible acrylic resin lingual flanges in the construction of mandibular complete dentures improved denture retention. PMID:26539387

Lithography With Metallo-Organic Resists

NASA Astrophysics Data System (ADS)

Pastor, A. C.; Pastor, R. C.; Braunstein, M.; Tangonan, G. L.

1981-02-01

Photolithography with metallo-organic resists is a relatively new addition to photo-engraving technology, and involves the chemical incorporation of inorganic constituents into photopolymerizable organic compounds, so that the photoresist functions not merely as a masking material, as in conventional photolithography, but also as the mass transference vehicle itself. The deposition of thin structured films of metal oxides with this method has been accomplished, the metal-doped resist in each case being the metal acrylate in acrylic acid, except in those cases where the metal acrylate was insoluble. Polymerization was effected with uv irradiation. The criteria for depositing other classes of inorganic compounds are outlined.

Synthesis and properties of hydroxy acrylic resin with high solid content

NASA Astrophysics Data System (ADS)

Yu, Zhen; Hu, Mingguang; Cui, Han; Xiao, Jijun

2017-10-01

Manufacturers of automotive repair finishes are tending to reduce more and more the level of volatile organic compounds in their paints in order to comply with increasingly strict environmental legislation. A high solid hydroxy acrylic resin was synthesised using CARDURA E10 and a type of hydroxyacrylic acid resin, its' acid value, hydroxylvalue, viscosity, structure, morphology was measured and film-forming properties after curing were characterised. The results show that the addition of CARDURA E10 in the copolymer composition significantly reduced the viscosity of the polymer system, improved the solid content of the resin and the physical properties of the coating. The hydroxyl acrylate resin with solid content of 90% and excellent comprehensive performance were successfully prepared by controlling the initiator dosage, polymerization temperature and monomer ratio.

Influence of various metal oxides on mechanical and physical properties of heat-cured polymethyl methacrylate denture base resins.

PubMed

Asar, Neset Volkan; Albayrak, Hamdi; Korkmaz, Turan; Turkyilmaz, Ilser

2013-08-01

To evaluate the effect of various metal oxides on impact strength (IS), fracture toughness (FT), water sorption (WSP) and solubility (WSL) of heat-cured acrylic resin. Fifty acrylic resin specimens were fabricated for each test and divided into five groups. Group 1 was the control group and Group 2, 3, 4 and 5 (test groups) included a mixture of 1% TiO2 and 1% ZrO2, 2% Al2O3, 2% TiO2, and 2% ZrO2 by volume, respectively. Rectangular unnotched specimens (50 mm × 6.0 mm × 4.0 mm) were fabricated and droptower impact testing machine was used to determine IS. For FT, compact test specimens were fabricated and tests were done with a universal testing machine with a cross-head speed of 5 mm/min. For WSP and WSL, discshaped specimens were fabricated and tests were performed in accordance to ISO 1567. ANOVA and Kruskal-Wallis tests were used for statistical analyses. IS and FT values were significantly higher and WSP and WSL values were significantly lower in test groups than in control group (P<.05). Group 5 had significantly higher IS and FT values and significantly lower WSP values than other groups (P<.05) and provided 40% and 30% increase in IS and FT, respectively, compared to control group. Significantly lower WSL values were detected for Group 2 and 5 (P<.05). Modification of heat-cured acrylic resin with metal oxides, especially with ZrO2, may be useful in preventing denture fractures and undesirable physical changes resulting from oral fluids clinically.

Factors that affect the EVA encapsulant discoloration rate upon accelerated exposure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pern, F.J.

1994-12-31

Several factors that may affect the net discoloration rate of the ethylene-vinyl acetate (EVA) copolymer encapsulants used in crystalline-Si photovoltaic (c-Si PV) modules upon accelerated exposure have been investigated by employing UV-visible spectrophotometry, spectrocolorimetry, and fluorescence analysis. A number of laminated films, including the two typical EVA formulations, A9918 and 15295, were studied. The results indicate that the rate of EVA discoloration is affected by the (1) curing agent and curing conditions; (2) presence and concentration of curing-generated, UV-excitable chromophores; (3) UV light intensity; (4) loss rate of the UV absorber, Cyasorb UV 531; (5) lamination; (6) film thickness; andmore » (7) photobleaching rate due to the diffusion of air into the laminated films. In general, the loss rate of the UV absorber and the rate of discoloration from light yellow to brown follow a sigmoidal pattern. A reasonable correlation for net changes in transmittance at 420 nm, yellowness index, and fluorescence peak area (or intensity) ratio is obtained as the extent of EVA discoloration progressed.« less

Effect of a Polymercaptan Material on the Electro-Optical Properties of Polymer-Dispersed Liquid Crystal Films.

PubMed

Sun, Yujian; Zhang, Cuihong; Zhou, Le; Fang, Hua; Huang, Jianhua; Ma, Haipeng; Zhang, Yi; Yang, Jie; Zhang, Lan-Ying; Song, Ping; Gao, Yanzi; Xiao, Jiumei; Li, Fasheng; Li, Kexuan

2016-12-30

Polymer-dispersed liquid crystal (PDLC) films were prepared by the ultraviolet-light-induced polymerization of photopolymerizable monomers in nematic liquid crystal/chiral dopant/thiol-acrylate reaction monomer composites. The effects of the chiral dopant and crosslinking agents on the electro-optical properties of the PDLC films were systematically investigate. While added the chiral dopant S811 into the PDLC films, the initial off-state transmittance of the films was decreased. It was found that the weight ratio among acrylate monomers, thiol monomer PETMP and the polymercaptan Capcure 3-800 showed great influence on the properties of the fabricated PDLC films because of the existence of competition between thiol-acrylate reaction and acrylate monomer polymerization reaction. While adding polymercaptans curing agent Capcure 3-800 with appropriate concentration into the PDLC system, lower driven voltage and higher contrast ratio were achieved. This made the polymer network and electro-optical properties of the PDLC films easily tunable by the introduction of the thiol monomers.

Metal-Filled Adhesives Amenable To X-Ray Inspection

NASA Technical Reports Server (NTRS)

Hermansen, Ralph D.; Sutherland, Thomas H.; Predmore, Roamer

1994-01-01

Adhesive joints between metal parts made amenable to nondestructive radiographic inspection by incorporating radiopaque fillers that increase x-ray contrasts of joints. Adhesives can be epoxies, urethanes, acrylics, phenolics, or silicones, with appropriate curing agents and with such modifiers as polysulfides, polyamides, or butadiene rubbers.

Effect of ultraviolet light irradiation and sandblasting treatment on bond strengths between polyamide and chemical-cured resin.

PubMed

Asakawa, Yuya; Takahashi, Hidekazu; Iwasaki, Naohiko; Kobayashi, Masahiro

2014-01-01

The aim of this study was to evaluate the effects of ultraviolet light (UV) irradiation and sandblasting treatment on the shear bond strength between polyamide and chemical-cured resin. Three types of commercial polyamides were treated using UV irradiation, sandblasting treatment, and a combining sandblasting and UV irradiation. The shear bond strength was measured and analyzed using the Kruskal-Wallis test (α=0.05). Comparing shear bond strengths without surface treatment, from 4.1 to 5.7 MPa, the UV irradiation significantly increased the shear bond strengths except for Valplast, whose shear bond strengths ranged from 5.2 to 9.3 MPa. The sandblasting treatment also significantly increased the shear bond strengths (8.0 to 11.4 MPa). The combining sandblasting and UV irradiation significantly increased the shear bond strengths (15.2 to 18.3 MPa) comparing without surface treatment. This combined treatment was considered the most effective at improving the shear bond strength between polyamide and chemical-cured resin.

Occupational skin hazards from synthetic plastics.

PubMed

Tosti, A; Guerra, L; Vincenzi, C; Peluso, A M

1993-01-01

Epoxy and acrylic resins have numerous industrial applications but are also widely used in the household environment. These compounds are presently one of the most important sources of occupational contact dermatitis. Contact sensitization to epoxy resins is usually caused by the resin itself but hardeners or other additives, such as reactive diluents, plasticizers, fillers and pigments, can occasionally be responsible. Since completely cured epoxy resins are not sensitizers, epoxy resin sensitization is always due to the presence, in the final polymer, of uncured allergenic low molecular weight oligomers. Acrylates are now considered the fourth most common cause of contact sensitization due to resins. Unpolymerized monomers of acrylic compounds are known to be responsible for the contact allergy. Accelerators, inhibitors and catalysts, which are usually added to the acrylates to promote the polymerization process, can also sensitize. Both allergic and irritant contact dermatitis may be caused by exposure to epoxy or acrylic resins and their additives. Contact urticaria, allergic or irritant airborne contact dermatitis caused by volatile compounds, onychia and paronychia can also occur. From January of 1984 to May of 1992 we detected 39 cases of occupational allergic contact dermatitis to epoxy resin system substances and 11 cases of occupational contact sensitization to acrylic compounds. In our experience, the electronics industry as well as paint and glue related activities were the most important sources of epoxy sensitization. Dental materials and anaerobic sealants were found to be the most frequent acrylate sensitizers.

Silane–Acrylate Chemistry for Regulating Network Formation in Radical Photopolymerization

PubMed Central

2017-01-01

Photoinitiated silane–ene chemistry has the potential to pave the way toward spatially resolved organosilicon compounds, which might find application in biomedicine, microelectronics, and other advanced fields. Moreover, this approach could serve as a viable alternative to the popular photoinitiated thiol–ene chemistry, which gives access to defined and functional photopolymer networks. A difunctional bis(trimethylsilyl)silane with abstractable hydrogens (DSiH) was successfully synthesized in a simple one-pot procedure. The radical reactivity of DSiH with various homopolymerizable monomers (i.e., (meth)acrylate, vinyl ester, acrylamide) was assessed via 1H NMR spectroscopic studies. DSiH shows good reactivity with acrylates and vinyl esters. The most promising silane–acrylate system was further investigated in cross-linking formulations toward its reactivity (e.g., heat of polymerization, curing time, occurrence of gelation, double-bond conversion) and compared to state-of-the-art thiol–acrylate resins. The storage stability of prepared resin formulations is greatly improved for silane–acrylate systems vs thiol–ene resins. Double-bond conversion at the gel point (DBCgel) and overall DBC were increased, and polymerization-induced shrinkage stress has been significantly reduced with the introduction of silane–acrylate chemistry. Resulting photopolymer networks exhibit a homogeneous network architecture (indicated by a narrow glass transition) that can be tuned by varying silane concentration, and this confirms the postulated regulation of radical network formation. Similar to thiol–acrylate networks, this leads to more flexible photopolymer networks with increased elongation at break and improved impact resistance. Additionally, swelling tests indicate a high gel fraction for silane–acrylate photopolymers. PMID:29033466

Erratum to: Application of addition-cured silicone denture relining materials to adjust mouthguards.

PubMed

Fukasawa, Shintaro; Churei, Hiroshi; Chowdhury, Ruman Uddin; Shirako, Takahiro; Shahrin, Sharika; Shrestha, Abhishekhi; Wada, Takahiro; Uo, Motohiro; Takahashi, Hidekazu; Ueno, Toshiaki

2016-01-01

The purposes of this study were to examine the shock absorption capability of addition-cured silicone denture relining materials and the bonding strength of addition-cured silicone denture relining materials and a commercial mouthguard material to determine its applicability to mouthguard adjustment. Two addition-cured silicone denture relining materials were selected as test materials. The impact test was applied by a free-falling steel ball. On the other hand, bonding strength was determined by a delamination test. After prepared surface treatments using acrylic resin on MG sheet surface, 2 types of addition-cured silicone denture relining materials were glued to MG surface. The peak intensity, the time to peak intensity from the onset of the transmitted force and bonding strength were statistically analyzed using ANOVA and Tukey's honest significant difference post hoc test (p<0.05). These results suggest that the silicone denture relining materials could be clinically applicable as a mouthguard adjustment material.

Application of photocuring technique on wood surface and its prospects in Bangladesh

NASA Astrophysics Data System (ADS)

Bhattcacharia, S. K.; Khan, Mubarak A.

2005-07-01

Photocuring technique has unveiled a new horizon in polymer science. Application of photocuring technique on wood surface has enhanced the use of low grade wood. As Bangladesh is an overpopulated country, necessity of good quality wood is increasing day by day. So low grade wood, like Simul or Partex, locally produced particleboard, would come out with great use. As Partex board, produced from Jute sticks and various types of indigenous low grade wood and particle board are abundant in Bangladesh, so photocuring could play a major role to improve the quality of low grade wood and serve the nation. Already, a lot of research works were carried out by the local scientists to improve the wood surface using UV curing method. Different formulations were also developed by the local scientists using various oligomer, monomer and different types of additives. The used oligomers are epoxy, polyester, urethane, etc. and monomers of different functionalities and used additives are acrylic monomer, CaCO3, sand, MgSiO3, talc, etc. Thin films were prepared on glass plate with different formulations using UV radiation and different characteristics properties (pendulum hardness, abrasion, gloss (60° and 20°), microscratch hardness, weathering effect, adhesion strength, etc.) were studied. Now, a Pilot Plant has already been established with the financial assistance by the government of Bangladesh, worth US 3.5 million.

Construction Material And Method

DOEpatents

Wagh, Arun S.; Antink, Allison L.

2006-02-21

A structural material of a polystyrene base and the reaction product of the polystyrene base and a solid phosphate ceramic. The ceramic is applied as a slurry which includes one or more of a metal oxide or a metal hydroxide with a source of phosphate to produce a phosphate ceramic and a poly (acrylic acid or acrylate) or combinations or salts thereof and polystyrene or MgO applied to the polystyrene base and allowed to cure so that the dried aqueous slurry chemically bonds to the polystyrene base. A method is also disclosed of applying the slurry to the polystyrene base.

Method of binding structural material

DOEpatents

Wagh, Arun S.; Antink, Allison L.

2007-12-25

A structural material of a polystyrene base and the reaction product of the polystyrene base and a solid phosphate ceramic. The ceramic is applied as a slurry which includes one or more of a metal oxide or a metal hydroxide with a source of phosphate to produce a phosphate ceramic and a poly (acrylic acid or acrylate) or combinations or salts thereof and polystyrene or MgO applied to the polystyrene base and allowed to cure so that the dried aqueous slurry chemically bonds to the polystyrene base. A method is also disclosed of applying the slurry to the polystyrene base.

Aqueous film coating to reduce recrystallization of guaifenesin from hot-melt extruded acrylic matrices.

PubMed

Bruce, Caroline D; Fegely, Kurt A; Rajabi-Siahboomi, Ali R; McGinity, James W

2010-02-01

This study investigated the effect of aqueous film coating on the recrystallization of guaifenesin from acrylic, hot-melt extruded matrix tablets. After hot-melt extrusion, matrix tablets were film-coated with either hypromellose or ethylcellulose. The effects of the coating polymer, curing and storage conditions, polymer weight gain, and core guaifenesin concentration on guaifenesin recrystallization were investigated. The presence of either film coating on the guaifenesin-containing tablets was found to prolong the onset time of drug crystallization. The coating polymer was the most important factor determining the delay in the onset of crystallization, with the more hydrophilic polymer, hypromellose, having a higher solubilization potential for the guaifenesin and delaying crystallization for longer period (3 or 6 months in tablets stored at 40 degrees C or 25 degrees C, respectively) than the more hydrophobic ethylcellulose, which displayed a lower solubilization potential for guaifenesin (crystal growth on tablets cured for 2 hours at 60 degrees C occurred within 3 weeks, whereas uncoated tablets displayed surface crystal growth after 30 minutes). Crystal morphology was also affected by the film coating. Elevated temperatures during both curing and storage, incomplete film coalescence, and high core drug concentrations all contributed to an earlier onset of crystal growth.

Fixation of chiral smectic liquid crystal (S)-(+)-4-(2-methyl-1-butyloyloxy)phenyl 4-[1-(propenoyloxy) butiloxy] benzoate using UV curing techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Afrizal,, E-mail: rizalunj04@yahoo.com; Nurdelima,; Umeir

2014-03-24

Chiral Smectic Liquid Crystal (S)-(+)-4-(2-methyl-1-butyloyloxy)phenyl 4-[1-(propenoyloxy) butiloxy] benzoate has been synthesized using method of steglich esterification at room temperature. The mesomorphic behavior of chiral smectic at 55°C that showed schlieren texture in POM analysis. Fixation of structure chiral smectic liquid crystal by means of photopolymerization of monomer (S)-(+)-4-(2-methyl-1-butyloyloxy)phenyl 4-[1-(propenoyloxy) butiloxy] benzoate under UV irradiation which called UV curing techniques. The curing process using UV 3 lamps 100 volt at 60°C for an hour. The product of photopolymerization could be seen by analysis of FTIR spectra both monomer and polymer. FTIR spectra of monomer, two peaks for ester carbonyl and C-Cmore » double bond groups appeared at 1729.09 cm-1and 3123.46 cm{sup −1}. After UV curing process, peak for the carbonyl group at 1729.09 cm{sup −1} decreased and a new peak at 1160.21 cm{sup −1} appeared due to the carbonyl group attached to a C-C bond group and then peak at 3123.46 cm{sup −1} for C-C double bond group was disappeared.« less

Photochromic cross-link polymer for color changing and sensing surface

NASA Astrophysics Data System (ADS)

Fu, Richard; Shi, Jianmin; Forsythe, Eric; Srour, Merric

2016-12-01

Photochromic cross-link polymers were developed using patented ultraviolet (UV) photoinitiator and commercial photochromic dyes. The photochromic dyes have been characterized by measuring absorbance before and after UV activation using UV-visible (Vis) spectrometry with varying activation intensities and wavelengths. Photochromic cross-link polymers were characterized by a dynamic xenon and UV light activation and fading system. The curing processes on cloth were established and tested to obtain effective photochromic responses. Both PulseForge photonic curing and PulseForge plus heat surface curing processes had much better photochromic responses (18% to 19%, 16% to 25%, respectively) than the xenon lamp treatment (8%). The newly developed photochromic cross-link polymer showed remarkable coloration contrasts and fast and comparable coloration and fading rates. Those intelligent, controlled color changing and sensing capabilities will be used on flexible and "drapeable" surfaces, which will incorporate ultra-low power sensors, sensor indicators, and identifiers.

Acrylic injectable and self-curing formulations for the local release of bisphosphonates in bone tissue.

PubMed

Rodríguez-Lorenzo, L M; Fernández, M; Parra, J; Vázquez, B; López-Bravo, A; Román, J San

2007-11-01

Two bisphosphonates (BPs), namely 1-hydroxy-2-[4-aminophenyl]ethane-1,1-diphosphonic acid (APBP) and 1-hydroxy-2-[3-indolyl]ethane-1,1-diphosphonic acid (IBP), have been synthesized and incorporated to acrylic injectable and self-curing formulations. Alendronic acid monosodium trihydrated salt (ALN) containing cement was formulated as control. These systems have potential applications in low density hard tissues affected by ailments characterized by a high osteoclastic resorption, i.e. osteoporosis and osteolysis. Values of curing parameters of APBP and IBP were acceptable to obtain pastes with enough fluency to be injected through a biopsy needle into the bone cavity. Working times ranged between 8 and 15 min and maximum temperature was around 50 degrees C. Cured systems stored for a month in synthetic body fluid had compressive strengths between 90 and 96 MPa and modulus between 1.2 and 1.3 GPa, which suggest mechanical stabilization after setting and in the short time. BPs were released in PBS at an initial rate depending on the corresponding chemical structure in the order ALN > APBP > IBP to give final concentrations in PBS of 2.21, 0.44, and 0.19 mol/mL for ALN, APBP, and IBP, respectively. Cytotoxicities of bisphosphonates were evaluated, IC(50) values being in the order APBP > ALN > IBP. Absence of cytotoxicity coming from leachables of the cured systems was observed in all cases independently of the BP. An improved cell growth and proliferation for the systems loaded with APBP and IBP compared with that loaded with ALN was observed, as assessed by measuring cell adhesion and proliferation, and total DNA content.

21 CFR 175.210 - Acrylate ester copolymer coating.

Code of Federal Regulations, 2012 CFR

2012-04-01

..., and methacrylic acid applied in emulsion form to molded virgin fiber and heat-cured to an insoluble... application of the emulsion may include substances named in this paragraph, in an amount not to exceed that... emulsion defoamer. Disodium hydrogen phosphate Do. Formaldehyde Glyceryl monostearate Methyl cellulose...

21 CFR 175.210 - Acrylate ester copolymer coating.

Code of Federal Regulations, 2013 CFR

2013-04-01

..., and methacrylic acid applied in emulsion form to molded virgin fiber and heat-cured to an insoluble... application of the emulsion may include substances named in this paragraph, in an amount not to exceed that... emulsion defoamer. Disodium hydrogen phosphate Do. Formaldehyde Glyceryl monostearate Methyl cellulose...

21 CFR 175.210 - Acrylate ester copolymer coating.

Code of Federal Regulations, 2011 CFR

2011-04-01

..., and methacrylic acid applied in emulsion form to molded virgin fiber and heat-cured to an insoluble... application of the emulsion may include substances named in this paragraph, in an amount not to exceed that... emulsion defoamer. Disodium hydrogen phosphate Do. Formaldehyde Glyceryl monostearate Methyl cellulose...

Passive fit and accuracy of three dental implant impression techniques.

PubMed

Al Quran, Firas A; Rashdan, Bashar A; Zomar, AbdelRahman A Abu; Weiner, Saul

2012-02-01

To reassess the accuracy of three impression techniques relative to the passive fit of the prosthesis. An edentulous maxillary cast was fabricated in epoxy resin with four dental implants embedded and secured with heat-cured acrylic resin. Three techniques were tested: closed tray, open tray nonsplinted, and open tray splinted. One light-cured custom acrylic tray was fabricated for each impression technique, and transfer copings were attached to the implants. Fifteen impressions for each technique were prepared with medium-bodied consistency polyether. Subsequently, the impressions were poured in type IV die stone. The distances between the implants were measured using a digital micrometer. The statistical analysis of the data was performed with ANOVA and a one-sample t test at a 95% confidence interval. The lowest mean difference in dimensional accuracy was found within the direct (open tray) splinted technique. Also, the one-sample t test showed that the direct splinted technique has the least statistical significant difference from direct nonsplinted and indirect (closed tray) techniques. All discrepancies were less than 100 Μm. Within the limitations of this study, the best accuracy of the definitive prosthesis was achieved when the impression copings were splinted with autopolymerized acrylic resin, sectioned, and rejoined. However, the errors associated with all of these techniques were less than 100 Μm, and based on the current definitions of passive fit, they all would be clinically acceptable.

Influence of chemical and mechanical polishing on water sorption and solubility of denture base acrylic resins.

PubMed

Rahal, Juliana Saab; Mesquita, Marcelo Ferraz; Henriques, Guilherme Elias Pessanha; Nóbilo, Mauro Antonio Arruda

2004-01-01

Influence of polishing methods on water sorption and solubility of denture base acrylic resins was studied. Eighty samples were divided into groups: Classico (CL), and QC 20 (QC) - hot water bath cured; Acron MC (AC), and Onda Cryl (ON) - microwave cured; and submitted to mechanical polishing (MP) - pumice slurry, chalk powder, soft brush and felt cone in a bench vise; or chemical polishing (CP) - heated monomer fluid in a chemical polisher. The first desiccation process was followed by storage in distilled water at 37 +/- 1 degrees C for 1 h, 1 day, 1, 2, 3 and 4 weeks. Concluding each period, water sorption was measured. After the fourth week, a second desiccation process was done to calculate solubility. Data were submitted to analysis of variance, followed by Tukey test (p

A Study on the Rheological and Mechanical Properties of Photo-Curable Ceramic/Polymer Composites with Different Silane Coupling Agents for SLA 3D Printing Technology.

PubMed

Song, Se Yeon; Park, Min Soo; Lee, Jung Woo; Yun, Ji Sun

2018-02-07

Silane coupling agents (SCAs) with different organofunctional groups were coated on the surfaces of Al₂O₃ ceramic particles through hydrolysis and condensation reactions, and the SCA-coated Al₂O₃ ceramic particles were dispersed in a commercial photopolymer based on interpenetrating networks (IPNs). The organofunctional groups that have high radical reactivity and are more effective in UV curing systems are usually functional groups based on acryl, such as acryloxy groups, methacrloxy groups, and acrylamide groups, and these silane coupling agents seem to improve interfacial adhesion and dispersion stability. The coating morphology and the coating thickness distribution of SCA-coated Al₂O₃ ceramic particles according to the different organofunctional groups were observed by FE-TEM. The initial dispersibility and dispersion stability of the SCA-coated Al₂O₃/High-temp composite solutions were investigated by relaxation NMR and Turbiscan. The rheological properties of the composite solutions were investigated by viscoelastic analysis and the mechanical properties of 3D-printed objects were observed with a nanoindenter.

A Study on the Rheological and Mechanical Properties of Photo-Curable Ceramic/Polymer Composites with Different Silane Coupling Agents for SLA 3D Printing Technology

PubMed Central

Song, Se Yeon; Park, Min Soo; Lee, Jung Woo; Yun, Ji Sun

2018-01-01

Silane coupling agents (SCAs) with different organofunctional groups were coated on the surfaces of Al2O3 ceramic particles through hydrolysis and condensation reactions, and the SCA-coated Al2O3 ceramic particles were dispersed in a commercial photopolymer based on interpenetrating networks (IPNs). The organofunctional groups that have high radical reactivity and are more effective in UV curing systems are usually functional groups based on acryl, such as acryloxy groups, methacrloxy groups, and acrylamide groups, and these silane coupling agents seem to improve interfacial adhesion and dispersion stability. The coating morphology and the coating thickness distribution of SCA-coated Al2O3 ceramic particles according to the different organofunctional groups were observed by FE-TEM. The initial dispersibility and dispersion stability of the SCA-coated Al2O3/High-temp composite solutions were investigated by relaxation NMR and Turbiscan. The rheological properties of the composite solutions were investigated by viscoelastic analysis and the mechanical properties of 3D-printed objects were observed with a nanoindenter. PMID:29414912

The analysis of colored acrylic, cotton, and wool textile fibers using micro-Raman spectroscopy. Part 2: comparison with the traditional methods of fiber examination.

PubMed

Buzzini, Patrick; Massonnet, Genevieve

2015-05-01

In the second part of this survey, the ability of micro-Raman spectroscopy to discriminate 180 fiber samples of blue, black, and red cottons, wools, and acrylics was compared to that gathered with the traditional methods for the examination of textile fibers in a forensic context (including light microscopy methods, UV-vis microspectrophotometry and thin-layer chromatography). This study shows that the Raman technique plays a complementary and useful role to obtain further discriminations after the application of light microscopy methods and UV-vis microspectrophotometry and assure the nondestructive nature of the analytical sequence. These additional discriminations were observed despite the lower discriminating powers of Raman data considered individually, compared to those of light microscopy and UV-vis MSP. This study also confirms that an instrument equipped with several laser lines is necessary for an efficient use as applied to the examination of textile fibers in a forensic setting. © 2015 American Academy of Forensic Sciences.

Fast-Curing Epoxy and Acrylate Adhesive Development for Adverse Marine Conditions

DTIC Science & Technology

2013-07-01

the bulk properties of the adhesive. Water contact can reduce the glass transition temperature, induce cracks , or initiate hydrolysis in which the...were the same as above except they were painted with gloss black enamel paint and allowed to dry 24 h prior to application of any adhesives

Synthesis of silica coated zinc oxide–poly(ethylene-co-acrylic acid) matrix and its UV shielding evaluation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramasamy, Mohankandhasamy; Kim, Yu Jun; Gao, Haiyan

Graphical abstract: - Highlights: • Well layer thickness controlled silica shell was made on ZnO nanoparticles. • PEAA, an interfacial agent is used to make nanocomposite–polymer matrix by twin-screw extruder. • Si-ZnO/PEAA matrix is highly stable and UV protective as compared to ZnO/PEAA matrix. • Nanoparticle embedded polymer matrix is suggested to make UV shielding fabrics with Nylon4. - Abstract: Silica coated zinc oxide nanoparticles (Si-ZnO NPs) (7 nm thick) were synthesized successfully and melt blended with poly(ethylene-co-acrylic acid) (PEAA resin) to improving ultraviolet (UV) shielding of zinc oxide nanoparticles (ZnO NPs). The photostability of both the ZnO NPs andmore » Si-ZnO NPs were analyzed by the difference in photoluminescence (PL) and by methylene blue (MB) degradation. Photo-degradation studies confirmed that Si-ZnO NPs are highly photostable compared to ZnO NPs. The melt blended matrices were characterized by field emission scanning electron microscopy interfaced with energy dispersive X-ray spectroscopy (FE-SEM-EDX). The UV shielding property was analyzed from the transmittance spectra of UV–visible (UV–vis) spectroscopy. The results confirmed fine dispersion of thick Si-ZnO NPs in the entire resin matrix. Moreover, the Si-ZnO/PEAA showed about 97% UV shielding properties than the ZnO/PEAA.« less

Maleate/vinyl ether UV-cured coatings: Effects of composition on curing and properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Noren, G.K.

1996-10-01

The effect of the composition of the maleate polyester and the vinyl ether terminated compound on their UV-curing and properties has been investigated. Linear unsaturated polyester resins based on maleic anhydride and 1,5-pentane diol were synthesized. The molecular weight of the unsaturated polyesters was varied by changing the ratio of maleic anhydride to 1,5-pentane diol and the double bond equivalent weight was varied by replacing maleic anhydride with succinic anhydride. Coating formulations containing these unsaturated polyesters, triethylene glycol divinyl ether and a free radical photoinitiator were crosslinked in the presence of UV light. The coatings were very brittle, exhibiting tensilemore » strengths in the range of 1.5-4.0 MPa and elongations of only 3-7%. Diethyl maleate and isobutyl vinyl ether were effective diluents for reducing viscosity but reduced the cure speed. A vinyl ether urethane oligomer was synthesized and enhanced the flexibility and toughness of the coatings when substituted for triethylene glycol divinyl ether.« less

Investigation of test methods, material properties, and processes for solar cell encapsulants

NASA Technical Reports Server (NTRS)

Willis, P. B.; Baum, B.; Goulet, A.

1981-01-01

The development of pottant compounds is emphasized. Formulation of the butyl acrylate syrup/casting pottant was completed. The formulation contains an ultraviolet stabilizer system and may be cured with an initiator that, unlike former selections, presents no shipping of handling hazards to the user. The catalyzed syrup is stable at room temperature and has a pot life of at least eight hours. The formulation of the ethylene/methyl acrylate lamination pottant was also completed. This compound is the alternative pottant to EVA and is similarly produced as an extruded sheet that is wound into rolls. This resin is inherently nonblocking.

Electron Beam Curing of Composite Positive Electrode for Li-Ion Battery

DOE PAGES

Du, Zhijia; Janke, C. J.; Li, Jianlin; ...

2016-10-12

We have successfully used electron beam cured acrylated polyurethanes as novel binders for positive electrodes for Li-ion batteries. Furthermore, the cross-linked polymer after electron beam curing coheres active materials and carbon black together onto Al foil. Electrochemical tests demonstrate the stability of the polymer at a potential window of 2.0 V–4.6 V. The electrode is found to have similar voltage profiles and charge-transfer resistance compared to the conventional electrode using polyvinylidene fluoride as the binder. Finally, when the electrode is tested in full Li-ion cells, they exhibit excellent cycling performance, indicating promising use for this new type of binder inmore » commercial Li-ion batteries in the future.« less

Finite element analysis of provisional structures of implant-supported complete prostheses.

PubMed

Carneiro, Bruno Albuquerque; de Brito, Rui Barbosa; França, Fabiana Mantovani Gomes

2014-04-01

The use of provisional resin implant-supported complete dentures is a fast and safe procedure to restore mastication and esthetics of patients soon after surgery and during the adaptation phase to the new denture. This study assessed stress distribution of provisional implant-supported fixed dentures and the all-on-4 concept using self-curing acrylic resin (Tempron) and bis-acrylic resin (Luxatemp) to simulate functional loads through the three-dimensional finite element method. Solidworks software was used to build three-dimensional models using acrylic resin (Tempron, model A) and bis-acrylic resin (Luxatemp, model B) for denture captions. Two loading patterns were applied on each model: (1) right unilateral axial loading of 150 N on the occlusal surfaces of posterior teeth and (2) oblique loading vector of 150 N at 45°. The results showed that higher stress was found on the bone crest below oblique load application with a maximum value of 187.57 MPa on model A and 167.45 MPa on model B. It was concluded that model B improved stress distribution on the denture compared with model A.

Microstructural aspects in steel fiber reinforced acrylic emulsion polymer modified concrete

NASA Astrophysics Data System (ADS)

Hazimmah, Dayang; Ayob, Afizah; Sie Yee, Lau; Chee Cung, Wong

2018-03-01

Scanning electron microscope observations of polymer-free and polymer-modified cements have shown that the polymer particles are partitioned between the inside of hydrates and the surface of anhydrous cement grains. For optimum dosage of acrylic emulsion polymer with 2.5%, the C-S-H gel in this structure is finer and more acicular. Some polymer adheres or deposit on the surface of the C-S-H gel. The presence of acrylic emulsion polymer confines the ionic diffusion so that the Ca(OH)2 crystallized locally to form fine crystals. The void in the structures seems to be smaller but no polymer films appears to be bridging the walls of pores although many polymer bonds or C-S-H spread into the pore spaces. In addition to porosity reduction, acrylic emulsion polymer modified the hydration products in the steel fiber -matrix ITZ. The hydration product C-S-H appeared as a needle like shape. The needle-shaped C-S-H increases and gradually formed the gel, with needles growing into the pore space. The phenomenon is more obvious as curing age increased.

Effect of the spectral emission energy of various UV sources on photochemical curing of unsaturated oligomeric ester coatings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Skubin, V.K.; Sazonov, A.P.; Torgonenko, V.A.

1988-11-10

In this paper, using the example of unsaturated oligomeric esters, the effect of UV radiation of various domestic sources on the rate of curing of coatings is investigated. For the investigations a 60% styrene solution of PN-15 grade unsaturated oligomeric ester based on an equimolar ratio of maleic anhydride and oxypropylated diphenylenepropene was used. Isobutyl ether of benzoin served as the photoinitiator. The following lamps were used as radiation sources: electrodeless high-frequency lamps of continuous action with additions of mercury, cadmium, and phosphorus; a DRKS-500 mercury-xenon-arc lamp; and a DRT-1000 tubular mercury-arc lamp. When choosing UV sources to increase themore » efficiency of photochemical decay of the initiator and the rate of curing of the coating it is necessary first of all to be guided by the distribution of the spectral energy of the lamp radiation and the UV absorption spectrum of the photoinitiator.« less

Mechanical and Thermal Properties of Dental Composites Cured with CAD/CAM Assisted Solid-State Laser

PubMed Central

De Santis, Roberto; Gloria, Antonio; Maietta, Saverio; Martorelli, Massimo; De Luca, Alessandro; Spagnuolo, Gianrico; Riccitiello, Francesco; Rengo, Sandro

2018-01-01

Over the last three decades, it has been frequently reported that the properties of dental restorative composites cured with argon laser are similar or superior to those achieved with conventional halogen and light emitting diode (LED) curing units. Whereas laser curing is not dependent on the distance between the curing unit and the material, such distance represents a drawback for conventional curing units. However, a widespread clinical application of this kind of laser remains difficult due to cost, heavy weight, and bulky size. Recently, with regard to the radiation in the blue region of the spectrum, powerful solid-state lasers have been commercialized. In the current research, CAD (computer-aided design)/CAM (computer-aided manufacturing) assisted solid-state lasers were employed for curing of different dental restorative composites consisting of micro- and nanoparticle-reinforced materials based on acrylic resins. Commercial LED curing units were used as a control. Temperature rise during the photopolymerisation process and bending properties were measured. By providing similar light energy dose, no significant difference in temperature rise was observed when the two light sources provided similar intensity. In addition, after 7 days since curing, bending properties of composites cured with laser and LED were similar. The results suggested that this kind of laser would be suitable for curing dental composites, and the curing process does not suffer from the tip-to-tooth distance. PMID:29584683

Application of addition-cured silicone denture relining materials to adjust mouthguards.

PubMed

Fukasawa, Shintaro; Churei, Hiroshi; Chowdhury, Ruman Uddin; Shirako, Takahiro; Shahrin, Sharika; Shrestha, Abhishekhi; Wada, Takahiro; Uo, Motohiro; Takahashi, Hidekazu; Ueno, Toshiaki

2016-01-01

The purposes of this study were to examine the shock absorption capability of addition-cured silicone denture relining materials and the bonding strength of addition-cured silicone denture relining materials and a commercial mouthguard material to determine its applicability to mouthguard adjustment. Two addition-cured silicone denture relining materials and eleven commercial mouthguard materials were selected as test materials. The impact test was applied by a free-falling steel ball. On the other hand, bonding strength was determined by a delamination test. After prepared surface treatments using acrylic resin on MG sheet surface, 2 types of addition-cured silicone denture relining materials were glued to MG surface. The peak intensity, the time to peak intensity from the onset of the transmitted force and bonding strength were statistically analyzed using ANOVA and Tukey's honest significant difference post hoc test (p<0.05). These results suggest that the silicone denture relining materials could be clinically applicable as a mouthguard adjustment material.

Synthesis and electromechanical characterization of a new acrylic dielectric elastomer with high actuation strain and dielectric strength

NASA Astrophysics Data System (ADS)

Hu, Wei; Niu, Xiaofan; Yang, Xinguo; Zhang, Naifang; Pei, Qibing

2013-04-01

Dielectric Elastomers (DEs) can be actuated under high electric field to produce large strains. Most high-performing DE materials such as the 3M™ VHB™ membranes are commercial products designed for industrial pressure-sensitive adhesives. The limited knowledge of the exact chemical structures of these commercial materials has made it difficult to understand the relationship between molecular structures and electromechanical properties. In this work, new acrylic elastomers based on n-butyl acrylate and acrylic acid were synthesized from monomer solutions by UV-initiated bulk polymerization. The new acrylic copolymers have a potential to obtain high dielectric constant, actuation strain, dielectric strength, and a high energy density. Silicone and ester oligomer diacrylates were also added onto the copolymer structures to suppress crystallization and to crosslink the polymer chains. Four acrylic formulations were developed with different amounts of acrylic acid. This gives a tunable stiffness, while the dielectric constant is varied from 4.3 to 7.1. The figure-of-merit performance of the best formulation is 186 % area strain, 222 MV/m of dielectric strength, and 2.7 MJ/m3 of energy density. To overcome electromechanical instability, different prestrain ratios were investigated, and under the optimized prestrain, the material has a lifetime of thousands of cycles at 120 % area strain.

Presidential Green Chemistry Challenge: 2005 Greener Reaction Conditions Award

EPA Pesticide Factsheets

Presidential Green Chemistry Challenge 2005 award winner, BASF, invented a one-component, urethane acrylate oligomer primer system for automobile refinishing that is UV-curable, has VOCs, and is free of diisocyanates.

Synthesis and characterization of composite polysulfone membranes for desalination in nanofiltration technique.

PubMed

Akbari, A; Homayonfal, M; Jabbari, V

2010-01-01

Composite nanofiltration (NF) membrane was developed polyacrylic acid (PAA) in situ UV graft polymerization process using ultrafiltration (UF) polysulfone (PSF) membrane as porous support. FT-IR spectra indicated that grafting was performed and it show peaks at 1,732 cm⁻¹ and 3,396 cm⁻¹ region for CO and OH starching bond of acrylic acid (AA) monomer, respectively. AFM microscopy showed the roughness of surface was reduced by increase of UV irradiation times. Effect of irradiation time on the grafting of acrylic acid (AA) in the same concentration was discussed. The salts rejection increase was accompanied with grafting of polysulfone (PSF) ultrafiltration (UF) membrane. The rejection of Na₂SO₄, MgSO₄, NaCl and CaCl₂ salts by PSF-grafted-PAA nanofiltration (NF) membrane was in 98, 60, 52 and 30% respectively, under 0.3 MPa.

Capillary Force Lithography for Cardiac Tissue Engineering

PubMed Central

Macadangdang, Jesse; Lee, Hyun Jung; Carson, Daniel; Jiao, Alex; Fugate, James; Pabon, Lil; Regnier, Michael; Murry, Charles; Kim, Deok-Ho

2014-01-01

Cardiovascular disease remains the leading cause of death worldwide1. Cardiac tissue engineering holds much promise to deliver groundbreaking medical discoveries with the aims of developing functional tissues for cardiac regeneration as well as in vitro screening assays. However, the ability to create high-fidelity models of heart tissue has proven difficult. The heart’s extracellular matrix (ECM) is a complex structure consisting of both biochemical and biomechanical signals ranging from the micro- to the nanometer scale2. Local mechanical loading conditions and cell-ECM interactions have recently been recognized as vital components in cardiac tissue engineering3-5. A large portion of the cardiac ECM is composed of aligned collagen fibers with nano-scale diameters that significantly influences tissue architecture and electromechanical coupling2. Unfortunately, few methods have been able to mimic the organization of ECM fibers down to the nanometer scale. Recent advancements in nanofabrication techniques, however, have enabled the design and fabrication of scalable scaffolds that mimic the in vivo structural and substrate stiffness cues of the ECM in the heart6-9. Here we present the development of two reproducible, cost-effective, and scalable nanopatterning processes for the functional alignment of cardiac cells using the biocompatible polymer poly(lactide-co-glycolide) (PLGA)8 and a polyurethane (PU) based polymer. These anisotropically nanofabricated substrata (ANFS) mimic the underlying ECM of well-organized, aligned tissues and can be used to investigate the role of nanotopography on cell morphology and function10-14. Using a nanopatterned (NP) silicon master as a template, a polyurethane acrylate (PUA) mold is fabricated. This PUA mold is then used to pattern the PU or PLGA hydrogel via UV-assisted or solvent-mediated capillary force lithography (CFL), respectively15,16. Briefly, PU or PLGA pre-polymer is drop dispensed onto a glass coverslip and the PUA mold is placed on top. For UV-assisted CFL, the PU is then exposed to UV radiation (λ = 250-400 nm) for curing. For solvent-mediated CFL, the PLGA is embossed using heat (120 °C) and pressure (100 kPa). After curing, the PUA mold is peeled off, leaving behind an ANFS for cell culture. Primary cells, such as neonatal rat ventricular myocytes, as well as human pluripotent stem cell-derived cardiomyocytes, can be maintained on the ANFS2. PMID:24962161

Digital micromirror device (DMD)-based 3D printing of poly(propylene fumarate) scaffolds.

PubMed

Mott, Eric J; Busso, Mallory; Luo, Xinyi; Dolder, Courtney; Wang, Martha O; Fisher, John P; Dean, David

2016-04-01

Our recent investigations into the 3D printing of poly(propylene fumarate) (PPF), a linear polyester, using a DMD-based system brought us to a resin that used titanium dioxide (TiO2) as an ultraviolet (UV) filter for controlling cure depth. However, this material hindered the 3D printing process due to undesirable lateral or "dark" curing (i.e., in areas not exposed to light from the DMD chip). Well known from its use in sunscreen, another UV filter, oxybenzone, has previously been used in conjunction with TiO2. In this study we hypothesize that combining these two UV filters will result in a synergistic effect that controls cure depth and avoids dark cure. A resin mixture (i.e., polymer, initiator, UV filters) was identified that worked well. The resin was then further characterized through mechanical testing, cure testing, and cytotoxicity testing to investigate its use as a material for bone tissue engineering scaffolds. Results show that the final resin eliminated dark cure as shown through image analysis. Mechanically the new scaffolds proved to be far weaker than those printed from previous resins, with compressive strengths of 7.8 ± 0.5 MPa vs. 36.5 ± 1.6 MPa, respectively. The new scaffolds showed a 90% reduction in elastic modulus and a 74% increase in max strain. These properties may be useful in tissue engineering applications where resorption is required. Initial cytotoxicity evaluation was negative. As hypothesized, the use of TiO2 and oxybenzone showed synergistic effects in the 3D printing of PPF tissue engineering scaffolds. Copyright © 2015 Elsevier B.V. All rights reserved.

UV-cured polymer optics

NASA Astrophysics Data System (ADS)

Piñón, Victor; Santiago, Freddie; Vogelsberg, Ashten; Davenport, Amelia; Cramer, Neil

2017-10-01

Although many optical-quality glass materials are available for use in optical systems, the range of polymeric materials is limited. Polymeric materials have some advantages over glass when it comes to large-scale manufacturing and production. In smaller scale systems, they offer a reduction in weight when compared to glass counterparts. This is especially important when designing optical systems meant to be carried by hand. We aimed to expand the availability of polymeric materials by exploring both crown-like and flint-like polymers. In addition, rapid and facile production was also a goal. By using UV-cured thiolene-based polymers, we were able to produce optical materials within seconds. This enabled the rapid screening of a variety of polymers from which we down-selected to produce optical flats and lenses. We will discuss problems with production and mitigation strategies in using UV-cured polymers for optical components. Using UV-cured polymers present a different set of problems than traditional injection-molded polymers, and these issues are discussed in detail. Using these produced optics, we integrated them into a modified direct view optical system, with the end goal being the development of drop-in replacements for glass components. This optical production strategy shows promise for use in lab-scale systems, where low-cost methods and flexibility are of paramount importance.

Advanced ultraviolet-resistant silver mirrors for use in solar reflectors

DOEpatents

Jorgensen, Gary J [Pine, CO; Gee, Randy [Arvada, CO

2009-11-03

A silver mirror construction that maintains a high percentage of hemispherical reflectance throughout the UV and visible spectrum when used in solar reflectors, comprising:a) a pressure sensitive adhesive layer positioned beneath a silver overlay;b) a polymer film disposed on the silver overlay;c) an adhesive layer positioned on the polymer film; andd) a UV screening acrylic film disposed on the adhesive layer.

Excimer Laser Curing Of Polymer Coatings

NASA Astrophysics Data System (ADS)

Klick, David; Akerman, M. Alfred; Paul, George L.; Supurovic, Darko; Tsuda, Haruki

1988-12-01

The use of the excimer laser as a source of energy for photo-assisted curing of industrial polymeric coatings was investigated. Presently, UV lamps are sometimes used to excite a photoinitiating molecule mixed with the starting monomers and oligomers of a coating. The resulting polymeric chain reaction multiplies the effect of the initial photons, making economical use of the light source. The high cost of laser photons may thus be justifiable if lasers provide advantages over lamps. A series of visibly transparent 7 μm coatings (a typical thickness for 'slick' magazine coatings) with various photoinitiators, monomers, and oligomers was illuminated with excimer laser light of various wavelengths, fluences, and pulse repetition rates. For the optimum parameters, it was found that the laser had large advantages in curing speed over existing UV lamp processes, due to its monochromaticity. Pigmented coatings (20 μm TiO2 mixtures typical of appliance or automotive finishes) are not easily cured with UV lamps due to the inability of light to penetrate the absorbing and scattering pigmented layer. However, economically-viable cure rates were achieved with certain photoinitiators using a tunable excimer-pumped dye laser. A prototype of such a laser suitable for factory use was built and used to cure these coatings. Results are scaled to a factory situation, and costs are calculated to show the advantages of the laser method over currently used processes.

Ester-free cross-linker molecules for ultraviolet-light-cured polysilsesquioxane gate dielectric layers of organic thin-film transistors

NASA Astrophysics Data System (ADS)

Okada, Shuichi; Nakahara, Yoshio; Uno, Kazuyuki; Tanaka, Ichiro

2018-04-01

Pentacene thin-film transistors (TFTs) were fabricated with ultraviolet-light (UV)-cured polysilsesquioxane (PSQ) gate dielectric layers using cross-linker molecules with or without ester groups. To polymerize PSQ without ester groups, thiol-ene reaction was adopted. The TFTs fabricated with PSQ layers comprising ester-free cross-linkers showed a higher carrier mobility than the TFTs with PSQ layers cross-linked with ester groups, which had large electric dipole moments that limited the carrier mobility. It was demonstrated that the thiol-ene reaction is more suitable than the conventional radical reaction for UV-cured PSQ with small dielectric constant.

The influence of polishing techniques on pre-polymerized CAD\\CAM acrylic resin denture bases

PubMed Central

Alammari, Manal Rahma

2017-01-01

Background Lately, computer-aided design and computer-aided manufacturing (CAD/CAM) has broadly been successfully employed in dentistry. The CAD/CAM systems have recently become commercially available for fabrication of complete dentures, and are considered as an alternative technique to conventionally processed acrylic resin bases. However, they have not yet been fully investigated. Objective The purpose of this study was to inspect the effects of mechanical polishing and chemical polishing on the surface roughness (Ra) and contact angle (wettability) of heat-cured, auto-cured and CAD/CAM denture base acrylic resins. Methods This study was conducted at the Advanced Dental Research Laboratory Center of King Abdulaziz University from March to June 2017. Three denture base materials were selected: heat cure poly-methylmethacrylate resin, thermoplastic (polyamide resin) and (CAD\\CAM) denture base resin. Sixty specimens were prepared and divided into three groups, twenty in each. Each group was divided according to the polishing techniques into (Mech P) and (Chem P), ten specimens in each; surface roughness and wettability were investigated. Data were analyzed by SPSS version 22, using one-way ANOVA and Pearson coefficient. Results One-way analysis of variance (ANOVA) and post hoc tests were used for comparing the surface roughness values between three groups which revealed a statistical significant difference between them (p1<0.001). Heat-cured denture base material of (Group I) in both methods, showed the highest mean surface roughness value (2.44±0.07, 2.72±0.09, Mech P and Chem P respectively); while CAD\\CAM denture base material (group III) showed the least mean values (1.08±0.23, 1.39±0.31, Mech P and Chem P respectively). CAD/CAM showed the least contact angle in both polishing methods, which were statistically significant at 5% level (p=0.034 and p<0.001). Conclusion Mechanical polishing produced lower surface roughness of CAD\\CAM denture base resin with superior smooth surface compared to chemical polishing. Mechanical polishing is considered the best effective polishing technique. CAD/CAM denture base material should be considered as the material of choice for complete denture construction in the near future, especially for older dental patients with changed salivary functions, because of its wettability. PMID:29238483

The influence of polishing techniques on pre-polymerized CAD\\CAM acrylic resin denture bases.

PubMed

Alammari, Manal Rahma

2017-10-01

Lately, computer-aided design and computer-aided manufacturing (CAD/CAM) has broadly been successfully employed in dentistry. The CAD/CAM systems have recently become commercially available for fabrication of complete dentures, and are considered as an alternative technique to conventionally processed acrylic resin bases. However, they have not yet been fully investigated. The purpose of this study was to inspect the effects of mechanical polishing and chemical polishing on the surface roughness (Ra) and contact angle (wettability) of heat-cured, auto-cured and CAD/CAM denture base acrylic resins. This study was conducted at the Advanced Dental Research Laboratory Center of King Abdulaziz University from March to June 2017. Three denture base materials were selected: heat cure poly-methylmethacrylate resin, thermoplastic (polyamide resin) and (CAD\\CAM) denture base resin. Sixty specimens were prepared and divided into three groups, twenty in each. Each group was divided according to the polishing techniques into (Mech P) and (Chem P), ten specimens in each; surface roughness and wettability were investigated. Data were analyzed by SPSS version 22, using one-way ANOVA and Pearson coefficient. One-way analysis of variance (ANOVA) and post hoc tests were used for comparing the surface roughness values between three groups which revealed a statistical significant difference between them (p 1 <0.001). Heat-cured denture base material of (Group I) in both methods, showed the highest mean surface roughness value (2.44±0.07, 2.72±0.09, Mech P and Chem P respectively); while CAD\\CAM denture base material (group III) showed the least mean values (1.08±0.23, 1.39±0.31, Mech P and Chem P respectively). CAD/CAM showed the least contact angle in both polishing methods, which were statistically significant at 5% level (p=0.034 and p<0.001). Mechanical polishing produced lower surface roughness of CAD\\CAM denture base resin with superior smooth surface compared to chemical polishing. Mechanical polishing is considered the best effective polishing technique. CAD/CAM denture base material should be considered as the material of choice for complete denture construction in the near future, especially for older dental patients with changed salivary functions, because of its wettability.

Inert Reassessment Document for 2-(2'-Hydroxy-5'-methylpheny)benzotriazole

EPA Pesticide Factsheets

2-(2'-Hydroxy-5'-methylphenyl)benzotriazole commonly known as Drometrizole is most commonly used as an UV light absorber helping to stabilizeand protect plastics, polyesters, celluloses, acrylates, dyes, rubber, synthetic and natural fibers, waxes,

Effect of pigment concentration on fastness and color values of thermal and UV curable pigment printing

NASA Astrophysics Data System (ADS)

Baysal, Gulcin; Kalav, Berdan; Karagüzel Kayaoğlu, Burçak

2017-10-01

In the current study, it is aimed to determine the effect of pigment concentration on fastness and colour values of thermal and ultraviolet (UV) curable pigment printing on synthetic leather. For this purpose, thermal curable solvent-based and UV curable water-based formulations were prepared with different pigment concentrations (3, 5 and 7%) separately and applied by screen printing technique using a screen printing machine. Samples printed with solvent-based formulations were thermally cured and samples printed with water-based formulations were cured using a UV curing machine equipped with gallium and mercury (Ga/Hg) lamps at room temperature. The crock fastness values of samples printed with solvent-based formulations showed that increase in pigment concentration was not effective on both dry and wet crock fastness values. On the other hand, in samples printed with UV curable water-based formulations, dry crock fastness was improved and evaluated as very good for all pigment concentrations. However, increasing the pigment concentration affected the wet crock fastness values adversely and lower values were observed. As the energy level increased for each irradiation source, the fastness values were improved. In comparison with samples printed with solvent-based formulations, samples printed with UV curable water-based formulations yielded higher K/S values at all pigment concentrations. The results suggested that, higher K/S values can be obtained in samples printed with UV curable water-based formulations at a lower pigment concentration compared to samples printed with solvent-based formulations.

Photo-induced living radical polymerization of acrylates utilizing a discrete copper(II)-formate complex.

PubMed

Anastasaki, Athina; Nikolaou, Vasiliki; Brandford-Adams, Francesca; Nurumbetov, Gabit; Zhang, Qiang; Clarkson, Guy J; Fox, David J; Wilson, Paul; Kempe, Kristian; Haddleton, David M

2015-04-04

A photo-polymerization protocol, utilizing a pre-formed and well-characterized Cu(II) formate complex, [Cu(Me6-Tren)(O2CH)](ClO4), mediated by UV light is described. In the absence of additional reducing agents and/or photosensitizers, ppm concentrations of the oxidatively stable [Cu(Me6-Tren)(O2CH)](ClO4), furnish near-quantitative conversions within 2 h, yielding poly(acrylates) with low dispersities (∼1.10) and exceptional end-group fidelity, capable of undergoing in situ chain extension and block copolymerization.

Fabrication of a 3D Printing Definitive Obturator Prosthesis: a Clinical Report.

PubMed

Tasopoulos, Theodoros; Kouveliotis, Georgios; Polyzois, Grigoris; Karathanasi, Vasiliki

2017-03-01

Digital technologies related to imaging and manufacturing provide the clinician with a wide variety of treatment options. Stereolithography (SLA) offers a simple and predictable way for an accurate reconstruction of congenital or acquired defects. A 65-years old cancer patient with non- keratinized squamous cell carcinoma of left maxillary sinus came for a prosthetic clinical evaluation. A bilateral maxillectomy was performed and the treatment plan included definite obturator prosthesis for the upper arch. CT data and 3D planning software were used to create a 3D printing plastic model of the defect. A wax pattern of the hollow bulb was fabricated and cured with heat-cured silicone soft liner. A final impression was obtained with the hollow bulb placed intraorally. The master cast was duplicated and the new cast was invested and reflasked. The flasks were opened, wax was boiled out and some space was created in the internal part of the obturator. Transparent heat cured acrylic resin was sandwiched with, at the inner part of the bulb, improving the retention between the acrylic denture base and the silicone based soft lining material. The patient was then placed on a 6-month recall. The five-year follow up consists of a chair side relining, when needed, of the definite removable prostheses. Maxillofacial surgery patients may develop postoperative complications such as trismus and pain. In these cases, the combination of digital technology and conventional techniques provide an accurate prosthetic restoration.

Fabrication of a 3D Printing Definitive Obturator Prosthesis: a Clinical Report

PubMed Central

Kouveliotis, Georgios; Polyzois, Grigoris; Karathanasi, Vasiliki

2017-01-01

Introduction Digital technologies related to imaging and manufacturing provide the clinician with a wide variety of treatment options. Stereolithography (SLA) offers a simple and predictable way for an accurate reconstruction of congenital or acquired defects. Clinical case A 65-years old cancer patient with non- keratinized squamous cell carcinoma of left maxillary sinus came for a prosthetic clinical evaluation. A bilateral maxillectomy was performed and the treatment plan included definite obturator prosthesis for the upper arch. CT data and 3D planning software were used to create a 3D printing plastic model of the defect. A wax pattern of the hollow bulb was fabricated and cured with heat-cured silicone soft liner. A final impression was obtained with the hollow bulb placed intraorally. The master cast was duplicated and the new cast was invested and reflasked. The flasks were opened, wax was boiled out and some space was created in the internal part of the obturator. Transparent heat cured acrylic resin was sandwiched with, at the inner part of the bulb, improving the retention between the acrylic denture base and the silicone based soft lining material. The patient was then placed on a 6-month recall. The five-year follow up consists of a chair side relining, when needed, of the definite removable prostheses. Conclusion Maxillofacial surgery patients may develop postoperative complications such as trismus and pain. In these cases, the combination of digital technology and conventional techniques provide an accurate prosthetic restoration. PMID:28740271

Antimicrobial activity of denture adhesive associated with Equisetum giganteum- and Punica granatum-enriched fractions against Candida albicans biofilms on acrylic resin surfaces.

PubMed

Almeida, Nara Ligia Martins; Saldanha, Luiz Leonardo; da Silva, Rafaela Alves; Pinke, Karen Henriette; da Costa, Eliane Ferraz; Porto, Vinicius Carvalho; Dokkedal, Anne Lígia; Lara, Vanessa Soares

2018-01-01

Candida biofilms adhere to the internal surface of removable dentures, which is an etiological factor in the pathogenesis of denture stomatitis (DS). Adhesive materials are used at the base of maxillary complete dentures to improve their retention and chewing qualities. This article reports the antimicrobial activity of the enriched fractions of Equisetum giganteum and Punica granatum incorporated into a denture adhesive against C. albicans biofilm. The biofilms were induced on the surface of heat-cured acrylic resin specimens that were previously treated with a mixture of adhesive/herb extracts. The antimicrobial activity was evaluated by CFU counts, XTT reduction, and SEM and CLSM analysis. Both herb extracts amplified the anti-biofilm action of the adhesive on the acrylic resin by up to 12 h. Therefore, when these extracts were combined with COREGA®, they played a collaborative and innovative role in biofilm control and can be considered alternatives for temporary use in the treatment and/or prevention of DS.

Double-bond-containing polyallene-based triblock copolymers via phenoxyallene and (meth)acrylate

NASA Astrophysics Data System (ADS)

Ding, Aishun; Lu, Guolin; Guo, Hao; Huang, Xiaoyu

2017-03-01

A series of ABA triblock copolymers, consisting of double-bond-containing poly(phenoxyallene) (PPOA), poly(methyl methacrylate) (PMMA), or poly(butyl acrylate) (PBA) segments, were synthesized by sequential free radical polymerization and atom transfer radical polymerization (ATRP). A new bifunctional initiator bearing azo and halogen-containing ATRP initiating groups was first prepared followed by initiating conventional free radical homopolymerization of phenoxyallene with cumulated double bond to give a PPOA-based macroinitiator with ATRP initiating groups at both ends. Next, PMMA-b-PPOA-b-PMMA and PBA-b-PPOA-b-PBA triblock copolymers were synthesized by ATRP of methyl methacrylate and n-butyl acrylate initiated by the PPOA-based macroinitiator through the site transformation strategy. These double-bond-containing triblock copolymers are stable under UV irradiation and free radical circumstances.

Improvement in device performance from a mixture of a liquid crystal and photosensitive acrylic prepolymer with the photoinduced vertical alignment method

PubMed Central

Ho, Czung-Yu; Lin, Fa-Hsin; Tao, Yu-Tai; Lee, Jiunn-Yih

2011-01-01

In a multicomponent nematic liquid crystal (NLC) mixture of a liquid crystal (negative-type NLC) and a photosensitive acrylic prepolymer, photopolymerization upon UV irradiation induces the separation of the LC and photosensitive acrylic prepolymer layers, thereby leading to a vertical arrangement of LC molecules. In this study, we propose a simple vertical alignment method for LC molecules, by adding a chiral smectic A (SmA∗) liquid crystal having homeotropic texture characteristics to an NLC mixture solution. Measurements of electro-optical properties revealed that the addition of the SmA∗ LC not only strengthened the anchoring force of the copolymer alignment film surface, but also significantly enhanced the contrast ratio (∼73%), response time and grayscale switching performance of the device. PMID:27877462

Light weight dentures: An innovative technique.

PubMed

Gundawar, Sham; Zamad, Aakanksha; Gundawar, Sneha

2014-01-01

Retention, stability and support are the basic principles on which the success of a complete denture relies. The severely resorbed maxillary and mandibular edentulous arches that are narrow and constricted with increased interarch space provide decreased support, retention and stability. To decrease the leverage, reduction in the weight of the prosthesis was recommended and also found beneficial. This article describes a simple procedure to reduce the weight of maxillary complete denture by use of an autopolymerizing acrylic resin shell which is incorporated during the packing stage. This method has the advantage of being easy and requires very little additional time. Hollow maxillary complete denture considerably reduces the weight of the prosthesis, which in turn prevents transmission of detrimental forces by reducing leverage action. This results in increased retention and stability and up to some extent it also preserves the existing residual alveolar ridge. The technique uses a clear matrix of trial denture to facilitate shaping of dough spacer to ensure an even thickness of acrylic to resist deformation and prevent seepage of saliva into the cavity making this technique more predictable. An autopolymerizing acrylic resin shell which creates hollow space and also has strength. Technique is simple to execute, easy economical and matching the shade of autopolymerizing acrylic resin with heat cures acrylic resin enhances esthetics. Light weight hollow dentures provide healthy and comfortable living for the geriatric edentulous patient.

Investigation of Test Methods, Material Properties, and Processes for Solar Cell Encapsulants

NASA Technical Reports Server (NTRS)

Willis, P. B.

1981-01-01

Encapsulant materials and processes for the production of cost effective, long life solar cell modules are identified, and evaluated. Ethylene vinyl acetate lamination pottant studies are conducted with respect to the time/temperature cure requirements for successful use of this compound. The time needed to produce successful gel contents are redetermined at a variety of temperatures and are related to the peroxide half life temperature curve. Formulation of the butyl acrylate syrup casting pottant is complete. The formulation contains an ultraviolet stabilizer system and is cured with an initiator that presents no shipping or handling hazards. The catalyzed syrup is stable at room temperature and has a pot life of at least an eight hour period of time. The syrup cures to a transparent rubber in 18 minutes at a temperature of 60 C.

Experimental study on mix proportion of fiber reinforced cementitious composites

NASA Astrophysics Data System (ADS)

Jia, Yi; Zhao, Renda; Liao, Ping; Li, Fuhai; Yuan, Yuan; Zhou, Shuang

2017-10-01

To study the mechanical property of fiber reinforced cementations composites influenced by the fiber length, quartz sand diameter, matrix of water cement ratio, volume fraction of fiber and magnesium acrylate solution. Several 40×40×160 mm standard test specimens, "8" specimens and long "8" specimens and 21 groups of fiber concrete specimens were fabricated. The flexural, compressive and uniaxial tensile strength were tested by using the bending resistance, compression resistance and electronic universal testing machine. The results show that flexural and compressive strength of fiber reinforced cementations composites increases along with the increase of quartz sand diameter, with the growth of the PVA fiber length increases; When the water-binder ratio is 0.25 and powder-binder ratio is 0.3, the PVA fiber content is 1.5% of the mass of cementations materials, there is a phenomenon of strain hardening; The addition of magnesium acrylate solution reduces the tensile strength of PVA fiber reinforced cementations composites, the tensile strength of the specimens in the curing age of 7d is decreased by about 21% and the specimens in curing age of 28d is decreased by more than 50%.

Radiation curing: Science and technology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pappas, S.P.

1992-01-01

The science and technology of radiation curing have progressed substantially within the last 20 years. Nevertheless, radiation-curable compositions typically command relatively small shares in many of their competitive markets. This situation signifies that potential advantages of radiation curing are not generally perceived to overcome their limitations. An important objective of this book is to address this issue, within the scope of the subjects offered, by providing the present state of knowledge and by identifying the directions and challenges for future studies. The first chapter introduces radiation curing. Chapter 2 offers the first systematic presentation of inorganic and organometallic photoinitiators. Chaptersmore » 3 and 4 present the analytical techniques of photocalorimetry and real-time infrared spectroscopy, respectively. Recent advances in resin technology are offered in Chapters 5 and 6, which constitute the first comprehensive accounts of (meth)acrylated silicones and vinyl ethers, respectively. Radiation-curable coatings, printing inks, and adhesives are discussed in Chapters 7-9, respectively. Chapter 10 offers a discussion on photopolymer imaging systems.« less

Overdenture retained by teeth using a definitive denture base technique: a case report.

PubMed

Nascimento, D F F; dos Santos, J F F; Marchini, L

2010-09-01

This paper presents a technique involving the use of a definitive denture base to make overdentures. Cores with ball attachments were cemented over remaining lower teeth. Impressions of the edentulous maxilla and mandible were taken to obtain a definitive acrylic resin base. The definitive base of the mandible was perforated at the location of ball attachments and its female components were fixed to the base using acrylic resin directly in the patient's mouth. Wax rims were then made, jaw relationships recorded, teeth mounted and tried in, and the dentures were cured. This technique allowed for easy fixing of female components and better retention during the recording of jaw relationships, and can also be used in the construction of implant retained dentures.

Low-cost encapsulation materials for terrestrial solar cell modules

NASA Technical Reports Server (NTRS)

Cuddihy, E. F.; Baum, B.; Willis, P.

1979-01-01

The paper presents the findings of material surveys intended to identify low cost materials which could be functional as encapsulants (by 1986) for terrestrial solar cell modules. Economic analyses have indicated that in order to meet the low cost goal of $2.70 per sq m, some or all of the following material technologies must be developed or advanced: (1) UV screening outer covers; (2) elastomeric acrylics; (3) weatherproofing and waterproofing of structural wood and paper products; (4) transparent UV stabilizers for the UV-sensitive transparent pottants; and (5) cost-effective utilization of silicone and fluorocarbon materials.

Ultraviolet /UV/ sensitive phosphors for silicon imaging detectors

NASA Technical Reports Server (NTRS)

Viehmann, W.; Cowens, M. W.; Butner, C. L.

1981-01-01

The fluorescence properties of UV sensitive organic phosphors and the radiometric properties of phosphor coated silicon detectors in the VUV, UV, and visible wavelengths are described. With evaporated films of coronene and liumogen, effective quantum efficiencies of up to 20% have been achieved on silicon photodiodes in the vacuum UV. With thin films of methylmethacrylate (acrylic), which are doped with organic laser dyes and deposited from solution, detector quantum efficiencies of the order of 15% for wavelengths of 120-165 nm and of 40% for wavelengths above 190 nm have been obtained. The phosphor coatings also act as antireflection coatings and thereby enhance the response of coated devices throughout the visible and near IR.

Thermal processing of EVA encapsulants and effects of formulation additives

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pern, F.J.; Glick, S.H.

1996-05-01

The authors investigated the in-situ processing temperatures and effects of various formulation additives on the formation of ultraviolet (UV) excitable chromophores, in the thermal lamination and curing of ethylene-vinyl acetate (EVA) encapsulants. A programmable, microprocessor-controlled, double-bag vacuum laminator was used to study two commercial as formulated EVA films, A9918P and 15295P, and solution-cast films of Elvaxrm (EVX) impregnated with various curing agents and antioxidants. The results show that the actual measured temperatures of EVA lagged significantly behind the programmed profiles for the heating elements and were affected by the total thermal mass loaded inside the laminator chamber. The antioxidant Naugardmore » P{trademark}, used in the two commercial EVA formulations, greatly enhances the formation of UV-excitable, short chromophores upon curing, whereas other tested antioxidants show little effect. A new curing agent chosen specifically for the EVA formulation modification produces little or no effect on chromophore formation, no bubbling problems in the glass/EVX/glass laminates, and a gel content of {approximately}80% when cured at programmed 155{degrees}C for 4 min. Also demonstrated is the greater discoloring effect with higher concentrations of curing-generated chromophores.« less

Thermal processing of EVA encapsulants and effects of formulation additives

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pern, F.J.; Glick, S.H.

1996-09-01

The authors investigated the in-situ processing temperatures and effects of various formulation additives on the formation of ultraviolet (UV) excitable chromophores in the thermal lamination and curing of ethylene-vinyl acetate (EVA) encapsulants. A programmable, microprocessor-controlled, double-bag vacuum laminator was used to study two commercial as-formulated EVA films. A9918P and 15295P, and solution-cast films of Elvax{trademark} (EVX) impregnated with various curing agents and antioxidants. The results show that the actual measured temperatures of EVA lagged significantly behind the programmed profiles for the heating elements and were affected by the total thermal mass loaded inside the laminator chamber. The antioxidant Naugard P{trademark},more » used in the two commercial EVA formulations, greatly enhances the formation of UV-excitable, short chromophores upon curing, whereas other tested antioxidants show little effect. A new curing agent chosen specifically for the EVA formulation modification produces little or no effect on chromophore formation, no bubbling problems in the glass/EVX/glass laminates, and a gel content of {approximately}80% when cured at programmed 155 C for 4 min. Also demonstrated is the greater discoloring effect with higher concentrations of curing-generated chromophores.« less

[Preparation of carbon fiber reinforced fluid type resin denture (author's transl)].

PubMed

Kasuga, H; Sato, H; Nakabayashi, N

1980-01-01

Transverse strength of cured fluid resins is weaker than that of the heat cured. We have studied to improve the mechanical strength of self-cured acrylic resin by application of carbon fibers as reinforcement and simple methods which must be acceptable for technicians are proposed. A cloth type carbon fiber was the best reinforcement among studied carbon fibers such as chopped or mat. The chopped fibers were difficult to mix homogeneously with fluid resins and effectiveness of the reinforcement was low. Breaking often occurred at the interface between the reinforcement and resin in the cases of mat which gave defects to the test specimens. To prepare reinforced denture, the cloth was trimmed on the master cast after removal of wax and the prepreg was formed with the alginate impression on the cast by Palapress and the cloth. Other steps were same as the usual fluid resin.

Contact allergy to epoxy (meth)acrylates.

PubMed

Aalto-Korte, Kristiina; Jungewelter, Soile; Henriks-Eckerman, Maj-Len; Kuuliala, Outi; Jolanki, Riitta

2009-07-01

Contact allergy to epoxy (meth)acrylates, 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy) phenyl]propane (bis-GMA), 2,2-bis[4-(2-hydroxy-3-acryloxypropoxy)phenyl]-propane (bis-GA), 2,2-bis[4-(methacryl-oxyethoxy)phenyl] propane (bis-EMA), 2,2-bis[4-(methacryloxy)phenyl]-propane (bis-MA), and glycidyl methacrylate (GMA) is often manifested together with contact allergy to diglycidyl ether of bisphenol A (DGEBA) epoxy resin. To analyse patterns of concomitant allergic reactions to the five epoxy (meth)acrylates in relation to exposure. We reviewed the 1994-2008 patch test files at the Finnish Institute of Occupational Health (FIOH) for reactions to the five epoxy (meth)acrylates, and examined the patients' medical records for exposure. Twenty-four patients had an allergic reaction to at least one of the studied epoxy (meth)acrylates, but specific exposure was found only in five patients: two bis-GMA allergies from dental products, two bis-GA allergies from UV-curable printing inks, and one bis-GA allergy from an anaerobic glue. Only 25% of the patients were negative to DGEBA epoxy resin. The great majority of allergic patch test reactions to bis-GMA, bis-GA, GMA and bis-EMA were not associated with specific exposure, and cross-allergy to DGEBA epoxy resin remained a probable explanation. However, independent reactions to bis-GA indicated specific exposure. Anaerobic sealants may induce sensitization not only to aliphatic (meth)acrylates but also to aromatic bis-GA.

Dimensional changes of acrylic resin denture bases: conventional versus injection-molding technique.

PubMed

Gharechahi, Jafar; Asadzadeh, Nafiseh; Shahabian, Foad; Gharechahi, Maryam

2014-07-01

Acrylic resin denture bases undergo dimensional changes during polymerization. Injection molding techniques are reported to reduce these changes and thereby improve physical properties of denture bases. The aim of this study was to compare dimensional changes of specimens processed by conventional and injection-molding techniques. SR-Ivocap Triplex Hot resin was used for conventional pressure-packed and SR-Ivocap High Impact was used for injection-molding techniques. After processing, all the specimens were stored in distilled water at room temperature until measured. For dimensional accuracy evaluation, measurements were recorded at 24-hour, 48-hour and 12-day intervals using a digital caliper with an accuracy of 0.01 mm. Statistical analysis was carried out by SPSS (SPSS Inc., Chicago, IL, USA) using t-test and repeated-measures ANOVA. Statistical significance was defined at P<0.05. After each water storage period, the acrylic specimens produced by injection exhibited less dimensional changes compared to those produced by the conventional technique. Curing shrinkage was compensated by water sorption with an increase in water storage time decreasing dimensional changes. Within the limitations of this study, dimensional changes of acrylic resin specimens were influenced by the molding technique used and SR-Ivocap injection procedure exhibited higher dimensional accuracy compared to conventional molding.

Dimensional Changes of Acrylic Resin Denture Bases: Conventional Versus Injection-Molding Technique

PubMed Central

Gharechahi, Jafar; Asadzadeh, Nafiseh; Shahabian, Foad; Gharechahi, Maryam

2014-01-01

Objective: Acrylic resin denture bases undergo dimensional changes during polymerization. Injection molding techniques are reported to reduce these changes and thereby improve physical properties of denture bases. The aim of this study was to compare dimensional changes of specimens processed by conventional and injection-molding techniques. Materials and Methods: SR-Ivocap Triplex Hot resin was used for conventional pressure-packed and SR-Ivocap High Impact was used for injection-molding techniques. After processing, all the specimens were stored in distilled water at room temperature until measured. For dimensional accuracy evaluation, measurements were recorded at 24-hour, 48-hour and 12-day intervals using a digital caliper with an accuracy of 0.01 mm. Statistical analysis was carried out by SPSS (SPSS Inc., Chicago, IL, USA) using t-test and repeated-measures ANOVA. Statistical significance was defined at P<0.05. Results: After each water storage period, the acrylic specimens produced by injection exhibited less dimensional changes compared to those produced by the conventional technique. Curing shrinkage was compensated by water sorption with an increase in water storage time decreasing dimensional changes. Conclusion: Within the limitations of this study, dimensional changes of acrylic resin specimens were influenced by the molding technique used and SR-Ivocap injection procedure exhibited higher dimensional accuracy compared to conventional molding. PMID:25584050

Influence of mechanical and chemical polishing in the solubility of acrylic resins polymerized by microwave irradiation and conventional water bath.

PubMed

Machado, Cristiane; Rizzatti-Barbosa, Célia M; Gabriotti, Morgana N; Joia, Fábio A; Ribeiro, Margarete C; Sousa, Rodrigo L S

2004-07-01

The aim of this work was to evaluate the solubility of acrylic resin activated by microwave irradiation (MI) or water bath (WB), when submitted to chemical (CP) or mechanical (MP) polishing. Forty acrylic resin samples were made and processed either by water bath (74 +/- 1 degrees C, 9 h) or microwave irradiation (500 W, 3 min). After deflasking, the samples were finished with aluminum oxide sandpapers in decreasing granulations till reaching similar dimensions. The samples were divided into four groups according to the association between kind of polymerization and polishing: A (WB + CP), B (WB + MP), C (MI + CP) and D (MI + MP). Solubility test was performed for each group and percentile solubility was calculated. Data were statistically analyzed using variance analysis and Kruskal-Wallis. The average of percentile solubility (%) was obtained: A = 0.07, B = 0.02, C = 0.04, D = -0.14, however, no significant difference was found between types of polishing in the samples polymerized by water bath (A and B). When processed by microwave irradiation (C and D), there was significant difference between the applied methods of polishing, so that mechanical polishing lead to a lower solubility. Solubility is a property of acrylic resins, representing not reacted substances releasing that could promote tissular reactions in prosthesis users. The association between polymerization by microwave irradiation and mechanical polishing showed less residual substances releasing for heat-cured acrylic resins, reducing the probability of developing tissular reactions.

The role of partitioning of reagents in grafting and curing reactions initiated by ionizing radiation and UV

NASA Astrophysics Data System (ADS)

Chaplin, R. P.; Dworjanyn, P. A.; Gamage, N. J. W.; Garnett, J. L.; Jankiewicz, S. V.; Khan, M. A.; Sangster, D. F.

1996-03-01

Experimental evidence involving monomer absorption studies using tritiated styrene is shown to support the proposal that additives such as mineral acids and certain inorganic salts when dissolved in the monomer solution enhance radiation grafting yields by a mechanism involving partitioning of reagents. Photoinitiators such as benzoin ethyl ether and its methyl analogue are reported as new additives for grafting of styrene in methanol to cellulose and polypropylene initiated by ionizing radiation. The partitioning concept is shown to be relevant in analogous UV grafting and curing processes.

Comparative Evaluation of Effect of Water Absorption on the Surface Properties of Heat Cure Acrylic: An in vitro Study

PubMed Central

Chandu, G S; Asnani, Pooja; Gupta, Siddarth; Faisal Khan, Mohd.

2015-01-01

Background: Use of alkaline peroxide denture cleanser with different temperature of water could cause a change in surface hardness of the acrylic denture and also has a bleaching effect. The purpose of the study was to determine the effect of increased water content during thermal cycling of hot water-treated acrylic on the surface hardness of acrylic denture base when compared to warm water treated acrylic. And to compare the bleaching effect of alkaline peroxide solution on the acrylic denture base on hot water and warm water treated acrylic. Materials and Methods: Forty samples (10 mm × 10 mm × 2.5 mm) were prepared. After the calculation of the initial hardness 40 samples, each was randomly assigned to two groups. Group A: 20 samples were immersed in 250 ml of warm distilled water at 40°C with alkaline peroxide tablet. Group B: 20 samples were immersed in 250 ml of hot distilled water at 100°C with alkaline peroxide tablet. The surface hardness of each test sample was obtained using the digital hardness testing machine recording the Rockwell hardness number before the beginning of the soaking cycles and after completion of 30 soak cycles and compared. Values were analyzed using paired t-test. Five samples from the Group A and five samples from Group B were put side by side and photographed using a Nikon D 40 digital SLR Camera and the photographs were examined visually to assess the change in color. Results: Acrylic samples immersed in hot water showed a statistically significant decrease of 5.8% in surface hardness. And those immersed in warm water showed a statistically insignificant increase of 0.67% in surface hardness. Samples from the two groups showed clinically insignificant difference in color when compared to each other on examination of the photographs. Conclusion: Thermocycling of the acrylic resin at different water bath temperature at 40°C and 100°C showed significant changes in the surface hardness. PMID:25954074

Preparation and luminescent properties of the novel polymer-rare earth complexes composed of Poly(ethylene-co-acrylic acid) and Europium ions

NASA Astrophysics Data System (ADS)

Wu, Yuewen; Hao, Haixia; Wu, Qingyao; Gao, Zihan; Xie, Hongde

2018-06-01

A series of novel polymer-rare earth complexes with Eu3+ ions have been synthesized and investigated successfully, including the binary complexes containing the single ligand poly(ethylene-co-acrylic acid) (EAA) and the ternary complexes using 1,10-phenanthroline (phen), dibenzoylmethane (DBM) or thenoyltrifluoroacetone (TTA) as the second ligand. Their structures have been characterized by Fourier transform infrared spectroscopy (FT-IR), elemental analysis and X-ray diffraction (XRD), which confirm that both EAA and small molecules participate in the coordination reaction with rare earth ions, and they can disperse homogeneously in the polymer matrixes. Both ultraviolet-visible (UV-vis) absorption and photoluminescence tests for the complexes have been recorded. The relationship between fluorescence intensity of polymer-rare earth complexes and the quantity of ligand EAA has been studied and discussed. The films casted from the complexes solution can emit strong characteristic red light under UV light excitation. All these results suggest that the complexes possess potential application as luminescent materials.

Comparison of the Effect of two Denture Cleansers on Tensile bond Strength of a Denture Liner.

PubMed

Farzin, M; Bahrani, F; Adelpour, E

2013-09-01

One of the most clinical challenging issues in prosthodontics is debonding of soft liners from the denture base. The aim of this study was to evaluate and compare tensile bond strength between soft liner and heat-cured acrylic resin when immersed in two different types of denture cleanser and distilled water, at different period of times. In this experimental in vivo study, 238 heat-cured acrylic blocks were made. A soft liner was embedded between the acrylic blocks. Samples were divided into four groups: 17 samples were in the control group and were not soaked in any solution .The remaining samples were divided into 3 groups (Distilled water, Calgon and Fittydent). Each group was then subdivided into two subcategories, regarding the immersion time variable; 15 and 45 minutes. All samples were placed in tension force and tensile bond strength was recorded with the testing machine. One- way ANOVA and Tucky HSD post-hoc test were adopted to analyze the yielded data (α> 0.05). Specimens which were immersed in two denture cleansers (Fittydent and Calgon) and in distilled water showed significant difference (p= 0.001) in bonding strength when compared to the control group. The subjects immersed in denture cleanser solutions and distilled water did not reveal any significant difference (p= 0.90). For all groups; most of the bonding failures (72%) were cohesive type. The effect of the denture cleansers and distilled water on the bond strength was not statistically different; however, the difference was significant between the immersed groups with the non-immersed group. Moreover, type of the denture cleanser did not show any effect on the tensile strength. The tensile strength increases with time of immersion.

Antifungal Effect of Henna against Candida albicans Adhered to Acrylic Resin as a Possible Method for Prevention of Denture Stomatitis

PubMed Central

Nawasrah, Amal; AlNimr, Amani; Ali, Aiman A.

2016-01-01

Denture stomatitis is a very common disease affecting the oral mucosa of denture wearers. The aim of this study was to measure the antifungal effect of henna against Candida albicans adhered to acrylic resin as a possible method for prevention of denture stomatitis. One-hundred-eighty acrylic plates were prepared of heat-cured acrylic denture resin. The specimens were divided into six groups of 30 samples each. The first group was only polymer and monomer following the conventional manufacturer instruction for processing complete dentures. The other five groups were processed by adding different concentration of Yamani henna powder (Harazi) to the polymer in a concentration of henna: polymer 1%, 2.5%, 5%, 7.5% and 10%, respectively. Samples were incubated in artificial saliva rich with Candida albicans at 37 °C, and the effect of henna on Candida albicans was evaluated in two different methods: semi-quantitative slide count and a culture-based quantitative assay (quantitative). Variation in the number of live Candida was observed with the increase in the concentration of Yamani henna powder. It was observed that the variation in live Candida, between control group and group B (concentration of Yamani henna powder was 1%), was statistically significant with a p-value of 0.0001. Similarly, variations in live Candida were significant, when the concentration of powder was 7.5% or 10% in contrast with control group and p-values were 0.0001 and 0.001 respectively. Adding henna to acrylic resin denture could be effective in controlling Candida albicans proliferation on the denture surface; however, its effects on the physical properties of acrylic resin denture need further studies. PMID:27223294

Synthesis and luminescent properties of the novel poly(ethylene-co-acrylic acid) films based on surface modification with lanthanide (Eu3+, Tb3+) complexes

NASA Astrophysics Data System (ADS)

Wu, Yuewen; Chu, Yang; Yu, Zhenjiang; Hao, Haixia; Wu, Qingyao; Xie, Hongde

2017-10-01

Two kinds of novel fluorescent films have been successfully synthesized by surface modification on the poly(ethylene-co-acrylic acid) films using the lanthanide (Eu3+, Tb3+) complexes. The process consists of three steps: conversion of carboxylic acid groups on the surface of the poly(ethylene-co-acrylic acid) films to acid chloride groups, synthesis of the lanthanide complexes bearing amino groups, and amidation to form the modified films. To characterize the modified films, Fourier transform infrared, thermogravimetric analysis, static water contact angle measurements and photoluminescence tests have been employed. Fourier transform infrared verifies the successful preparation of the lanthanide complexes and the modified poly(ethylene-co-acrylic acid) films. These films can emit strong characteristic red and green light under UV light excitation. In addition, the films both have short lifetime (1.14 ms and 1.21 ms), high thermal stability (Td = 408 °C and 411 °C) and, compared with unmodified ones, increased hydrophilicity. All these results suggest that the modified films have potential application as luminescent materials under high temperature.

Sulfonated macro-RAFT agents for the surfactant-free synthesis of cerium oxide-based hybrid latexes.

PubMed

Garnier, Jérôme; Warnant, Jérôme; Lacroix-Desmazes, Patrick; Dufils, Pierre-Emmanuel; Vinas, Jérôme; van Herk, Alex

2013-10-01

Three types of amphiphatic macro-RAFT agents were employed as compatibilizers to promote the polymerization reaction at the surface of nanoceria for the synthesis of CeO2-based hybrid latexes. Macro-RAFT copolymers and terpolymers were first synthesized employing various combinations of butyl acrylate as a hydrophobic monomer and acrylic acid (AA) and/or 2-acrylamido-2-methylpropane sulfonic acid (AMPS) as hydrophilic monomers. After characterizing the adsorption of these macro-RAFT agents at the cerium oxide surface by UV-visible spectrometry, emulsion copolymerization reactions of styrene and methyl acrylate were then carried out in the presence of the surface-modified nanoceria. Dynamic Light Scattering and cryo-Transmission Electron Microscopy were employed to confirm the hybrid structure of the final CeO2/polymer latexes, and proved that the presence of acrylic acid units in amphiphatic macro-RAFT agents enabled an efficient formation of hybrid structures, while the presence of AMPS units, when combined with AA units, resulted in a better distribution of cerium oxide nanoclusters between latex particles. Copyright © 2013 Elsevier Inc. All rights reserved.

The Effects of UV Light on the Chemical and Mechanical Properties of a Transparent Epoxy-Diamine System in the Presence of an Organic UV Absorber

PubMed Central

Nikafshar, Saeid; Zabihi, Omid; Ahmadi, Mojtaba; Mirmohseni, Abdolreza; Taseidifar, Mojtaba; Naebe, Minoo

2017-01-01

Despite several excellent properties including low shrinkage, good chemical resistance, curable at low temperatures and the absence of byproducts or volatiles, epoxy resins are susceptible to ultra violet (UV) damage and their durability is reduced substantially when exposed to outdoor environments. To overcome this drawback, UV absorbers have been usually used to decrease the rate of UV degradation. In this present study, the effects of UV light on the chemical, mechanical and physical properties of cured epoxy structure, as well as the effect of an organic UV absorber, Tinuvin 1130, on the epoxy properties were investigated. Chemical changes in a cured epoxy system as a result of the presence and absence of Tinuvin 1130 were determined using Fourier transform infrared spectroscopy (FT-IR) analyses. The effect of Tinuvin 1130 on the surface morphology of the epoxy systems was also investigated by scanning electron microscopy (SEM) imaging. Additionally, the glass transition temperatures (Tg) before and during UV radiation were measured. After an 800 h UV radiation, mechanical test results revealed that the lack of the UV absorber can lead to a ~30% reduction in tensile strength. However, in the presence of Tinuvin 1130, the tensile strength was reduced only by ~11%. It was hypothesized that the use of Tinuvin 1130, as an organic UV absorber in the epoxy-amine system, could decrease the undesirable effects, arising from exposure to UV light. PMID:28772538

Electron-beam-initiated polymerization of poly(ethylene glycol)-based wood impregnants.

PubMed

Trey, Stacy M; Netrval, Julia; Berglund, Lars; Johansson, Mats

2010-11-01

The current study demonstrates that methacrylate and acrylate poly(ethylene glycol) (PEG) functional oligomers can be effectively impregnated into wood blocks, and cured efficiently to high conversions without catalyst by e-beam radiation, allowing for less susceptibility to leaching, and favorable properties including higher Brinell hardness values. PEG based monomers were chosen because there is a long history of this water-soluble monomer being able to penetrate the cell wall, thus bulking it and decreasing the uptake of water which further protects the wood from fungal attack. Diacrylate, dimethacrylate, and dihydroxyl functional PEG of M(w) 550-575, of concentrations 0, 30, 60, and 100 wt % in water, were vacuum pressure impregnated into Scots Pine blocks of 15 × 25 × 50 mm in an effort to bulk the cell wall. The samples were then irradiated and compared with nonirradiated samples. It was shown by IR, DSC that the acrylate polymers were fully cured to much higher conversions than can be reached with conventional methods. Leaching studies indicated a much lower amount of oligomer loss from the cured vinyl functional PEG chains in comparison to hydroxyl functional PEG indicating a high degree of fastening of the polymer in the wood. The Brinell hardness indicated a significant increase in hardness to hardwood levels in the modified samples compared to the samples of hydroxyl functional PEG and uncured vinyl PEG samples, which actually became softer than the untreated Scots Pine. By monitoring the dimensions of the sample it was found by weight percent gain calculations (WPG %) that water helps to swell the wood structure and allow better access of the oligomers into the cell wall. Further, the cure shrinkage of the wood samples demonstrated infiltration of the oligomers into the cell wall as this was not observed for methyl methacrylate which is well-documented to remain in the lumen. However, dimensional stability of the vinyl polymer modified blocks when placed in water was not observed to the same extent as PEG.

Characterization of ultraviolet light cured polydimethylsiloxane films for low-voltage, dielectric elastomer actuators

NASA Astrophysics Data System (ADS)

Töpper, Tino; Wohlfender, Fabian; Weiss, Florian; Osmani, Bekim; Müller, Bert

2016-04-01

The reduction the operation voltage has been the key challenge to realize of dielectric elastomer actuators (DEA) for many years - especially for the application fields of robotics, lens systems, haptics and future medical implants. Contrary to the approach of manipulating the dielectric properties of the electrically activated polymer (EAP), we intend to realize low-voltage operation by reducing the polymer thickness to the range of a few hundred nanometers. A study recently published presents molecular beam deposition to reliably grow nanometer-thick polydimethylsiloxane (PDMS) films. The curing of PDMS is realized using ultraviolet (UV) radiation with wavelengths from 180 to 400 nm radicalizing the functional side and end groups. The understanding of the mechanical properties of sub-micrometer-thin PDMS films is crucial to optimize DEAs actuation efficiency. The elastic modulus of UV-cured spin-coated films is measured by nano-indentation using an atomic force microscope (AFM) according to the Hertzian contact mechanics model. These investigations show a reduced elastic modulus with increased indentation depth. A model with a skin-like SiO2 surface with corresponding elastic modulus of (2.29 +/- 0.31) MPa and a bulk modulus of cross-linked PDMS with corresponding elastic modulus of (87 +/- 7) kPa is proposed. The surface morphology is observed with AFM and 3D laser microscopy. Wrinkled surface microstructures on UV-cured PDMS films occur for film thicknesses above (510 +/- 30) nm with an UV-irradiation density of 7.2 10-4 J cm-2 nm-1 at a wavelength of 190 nm.

Impact of Packing and Processing Technique on Mechanical Properties of Acrylic Denture Base Materials

PubMed Central

Nejatian, Touraj; Sefat, Farshid; Johnson, Tony

2015-01-01

The fracture resistance of polymethylmethacrylate (PMMA) as the most popular denture base material is not satisfactory. Different factors can be involved in denture fracture. Among them, flexural fatigue and impact are the most common failure mechanisms of an acrylic denture base. It has been shown that there is a correlation between the static strength and fatigue life of composite resins. Therefore, the transverse strength of the denture base materials can be an important indicator of their service life. In order to improve the fracture resistance of PMMA, extensive studies have been carried out; however, only a few promising results were achieved, which are limited to some mechanical properties of PMMA at the cost of other properties. This study aimed at optimizing the packing and processing condition of heat-cured PMMA as a denture base resin in order to improve its biaxial flexural strength (BFS). The results showed that the plain type of resin with a powder/monomer ratio of 2.5:1 or less, packed conventionally and cured in a water bath for 2 h at 95 °C provides the highest BFS. Also, it was found that the performance of the dry heat processor is inconsistent with the number of flasks being loaded.

UV dichroic coatings on metallic reflectors

NASA Astrophysics Data System (ADS)

Raghunath, C.; Babu, N. J.; chandran, K. M.

2008-05-01

The work presented here explains the design and deposition process of dichroic coating on metallic reflectors developed for UV curing systems. Special designs are adopted to achieve the spectral band and optimized to suit to the requirements. A mirror, which reflects the UV radiation (220 - 400 nm) and absorbs visible and infrared radiation (400 - 2000nm), is described in detail.

Electron beams in research and technology

NASA Astrophysics Data System (ADS)

Mehnert, R.

1995-11-01

Fast electrons lose their energy by inelastic collisions with electrons of target molecules forming secondary electrons and excited molecules. Coulomb interaction of secondary electrons with valence electrons of neighboring molecules leads to the formation of radical cations, thermalized electrons, excited molecular states and radicals. The primary reactive species initiate chemical reactions in the materials irradiated. Polymer modifications using accelerated electrons such as cross-linking of cable insulation, tubes, pipes and moldings, vulcanization of elastomers, grafting of polymer surfaces, processing of foamed plastics and heat shrinkable materials have gained wide industrial acceptance. A steadily growing electron beam technology is curing of paints, lacquers, printing inks and functional coatings. Electron beam processing offers high productivity, the possibility to treat the materials at normal temperature and pressure, excellent process control and clean production conditions. On an industrial scale the most important application of fast electrons is curing of 100% reactive monomer/prepolymer systems. Mainly acrylates and epoxides are used to formulate functional coatings on substrates such as paper, foil, wood, fibre board and high pressure laminates. A survey is given about the reaction mechanism of curing, the characterization of cured coatings, and of some industrial application.

Durability to oxygen reactive ion etching enhanced by addition of synthesized bis(trimethylsilyl)phenyl-containing (meth)acrylates in ultraviolet nanoimprint lithography

NASA Astrophysics Data System (ADS)

Ito, Shunya; Sato, Hiroki; Tasaki, Yuhei; Watanuki, Kimihito; Nemoto, Nobukatsu; Nakagawa, Masaru

2016-06-01

We investigated the selection of bis(trimethylsilyl)phenyl-containing (meth)acrylates as additives to improve the durability to oxygen reactive ion etching (O2 RIE) of sub-50 nm imprint resist patterns suitable for bubble-defect-free UV nanoimprinting with a readily condensable gas. 2,5-Bis(2-acryloyloxyethoxy)-1,4-bis(trimethylsilyl)benzene, which has a diacrylate chemical structure similar to that of glycerol 1,3-diglycerolate diacrylate used as a base monomer, and 3-(2-methacryloyloxyethoxy)-1-(hydroxylethoxy)-2-propoxy-3,5-bis(trimethylsilyl)benzene, which has a hydroxy group similar to the base monomer, were synthesized taking into consideration the Ohnishi and ring parameters, and the oxidization of the trimethylsilyl moiety to inorganic species during O2 RIE. The addition of the latter liquid additive to the base monomer decreased etching rate owing to the good miscibility of the additive in the base monomer, while the addition of the former crystalline additive caused phase separation after UV nanoimprinting. The latter additive worked as a compatibilizer to the former additive, which is preferred for etching durability improvement. The coexistence of the additives enabled the fabrication of a 45 nm line-and-space resist pattern by UV nanoimprinting, and its residual layer could be removed by O2 RIE.

Flow lithography in ultraviolet-curable polydimethylsiloxane microfluidic chips

PubMed Central

Kim, Junbeom; An, Heseong; Seo, Yoojin; Jung, Youngmee; Lee, Jong Suk; Bong, Ki Wan

2017-01-01

Flow Lithography (FL) is the technique used for the synthesis of hydrogel microparticles with various complex shapes and distinct chemical compositions by combining microfluidics with photolithography. Although polydimethylsiloxane (PDMS) has been used most widely as almost the sole material for FL, PDMS microfluidic chips have limitations: (1) undesired shrinkage due to the thermal expansion of masters used for replica molding and (2) interfacial delamination between two thermally cured PDMS layers. Here, we propose the utilization of ultraviolet (UV)-curable PDMS (X-34-4184) for FL as an excellent alternative material of the conventional PDMS. Our proposed utilization of the UV-curable PDMS offers three key advantages, observed in our study: (1) UV-curable PDMS exhibited almost the same oxygen permeability as the conventional PDMS. (2) The almost complete absence of shrinkage facilitated the fabrication of more precise reverse duplication of microstructures. (3) UV-cured PDMS microfluidic chips were capable of much stronger interfacial bonding so that the burst pressure increased to ∼0.9 MPa. Owing to these benefits, we demonstrated a substantial improvement of productivity in synthesizing polyethylene glycol diacrylate microparticles via stop flow lithography, by applying a flow time (40 ms) an order of magnitude shorter. Our results suggest that UV-cured PDMS chips can be used as a general platform for various types of flow lithography and also be employed readily in other applications where very precise replication of structures on micro- or sub-micrometer scales and/or strong interfacial bonding are desirable. PMID:28469763

Effect of grape bunch sunlight exposure and UV radiation on phenolics and volatile composition of Vitis vinifera L. cv. Pinot noir wine.

PubMed

Song, Jianqiang; Smart, Richard; Wang, Hua; Dambergs, Bob; Sparrow, Angela; Qian, Michael C

2015-04-15

The effect of canopy leaf removal and ultraviolet (UV) on Pinot noir grape and wine composition was investigated in this study. Limited basal leaf removal in the fruit zone was conducted, compared to shaded bunches. The UV exposure was controlled using polycarbonate screens to block UV radiation, and acrylic screens to pass the UV. The results showed that bunch sunlight and UV exposure significantly increased the Brix and pH in the grape juice, and increased substantially wine colour density, anthocyanins, total pigment, total phenolics and tannin content. Bunch sunlight and UV exposure affected terpene alcohols, C13-norisprenoids and other volatile composition of the wine differently. Sunlight exposure and UV resulted in increase of nerol, geraniol and citronellol but not linalool. Sunlight exposure slightly increased the concentration of β-ionone, but the increase was not statistically significant for UV treatment. Neither sunlight nor UV treatment showed any impact on the concentration of β-damascenone. Copyright © 2014 Elsevier Ltd. All rights reserved.

Novel biobased photo-crosslinked polymer networks prepared from vegetable oil and 2,5-furan diacrylate

USDA-ARS?s Scientific Manuscript database

Novel biobased crosslinked polymer networks were prepared from vegetable oil with 2,5-furan diacrylate as a difunctional stiffener through UV photopolymerization, and the mechanical properties of the resulting films were evaluated. The vegetable oil raw materials used were acrylated epoxidized soybe...

Investigation of Test Methods, Material Properties and Processes for Solar Cell Encapsulants

NASA Technical Reports Server (NTRS)

Willis, P.; Baum, B.

1982-01-01

The evaluation of potentially useful low cost encapsulation materials is discussed. The goal is to identify, evaluate, test and recommend encapsulant materials and processes for the production of cost effective, long life solar cell modules. Technical investigations concerned the development of advanced cure chemistries for lamination type pottants; the continued evaluation of soil resistant surface treatment, and the results of an accelerated aging test program for the comparison of material stabilities. New compounds were evaluated for efficiency in curing both ethylene/vinyl acetate and ethylene/methyl acrylate pottants intended for vacuum bag lamination of solar cells. Two component aliphatic urethane casting syrups were evaluated for suitability as solar module pottants on the basis of optical, physical and fabrication characteristics.

[Development of denture base resin. 2. Manufacturing of visible-light cured prepreg and physical properties of FRP].

PubMed

Kimura, H; Yu, P Y; Teraoka, F; Sugita, M

1989-09-01

To develop the visible light-cured FRP denture base, we investigated the physical properties and the warp of FRP plate by using various combinations of matrix resin and reinforcement. From the results of the bending test, hardness test and manipulation processing, the matrix resin of Bis-GMA/UDMA/3 G at 48/48/4 wt% was determined. The sateen weave's glasscloth as the reinforcement of the prepreg was used. The maximum plies included FRP of 0.5 mm, 0.8 and 1.0 mm thickness have the same maximum bending strengths of 45 kgf/mm2, which is about 5 times larger than that of conventional acrylic resin. The warp of these FRP plates were not found.

High performance printed oxide field-effect transistors processed using photonic curing.

PubMed

Garlapati, Suresh Kumar; Marques, Gabriel Cadilha; Gebauer, Julia Susanne; Dehm, Simone; Bruns, Michael; Winterer, Markus; Tahoori, Mehdi Baradaran; Aghassi-Hagmann, Jasmin; Hahn, Horst; Dasgupta, Subho

2018-06-08

Oxide semiconductors are highly promising candidates for the most awaited, next-generation electronics, namely, printed electronics. As a fabrication route for the solution-processed/printed oxide semiconductors, photonic curing is becoming increasingly popular, as compared to the conventional thermal curing method; the former offers numerous advantages over the latter, such as low process temperatures and short exposure time and thereby, high throughput compatibility. Here, using dissimilar photonic curing concepts (UV-visible light and UV-laser), we demonstrate facile fabrication of high performance In 2 O 3 field-effect transistors (FETs). Beside the processing related issues (temperature, time etc.), the other known limitation of oxide electronics is the lack of high performance p-type semiconductors, which can be bypassed using unipolar logics from high mobility n-type semiconductors alone. Interestingly, here we have found that our chosen distinct photonic curing methods can offer a large variation in threshold voltage, when they are fabricated from the same precursor ink. Consequently, both depletion and enhancement-mode devices have been achieved which can be used as the pull-up and pull-down transistors in unipolar inverters. The present device fabrication recipe demonstrates fast processing of low operation voltage, high performance FETs with large threshold voltage tunability.

Hierarchically porous materials from layer-by-layer photopolymerization of high internal phase emulsions.

PubMed

Sušec, Maja; Ligon, Samuel Clark; Stampfl, Jürgen; Liska, Robert; Krajnc, Peter

2013-06-13

A combination of high internal phase emulsion (HIPE) templating and additive manufacturing technology (AMT) is applied for creating hierarchical porosity within an acrylate and acrylate/thiol-based polymer network. The photopolymerizable formulation is optimized to produce emulsions with a volume fraction of droplet phase greater than 80 vol%. Kinetic stability of the emulsions is sufficient enough to withstand in-mold curing or computer-controlled layer-by-layer stereolithography without phase separation. By including macroscale cellular cavities within the build file, a level of controlled porosity is created simultaneous to the formation of the porous microstructure of the polyHIPE. The hybrid HIPE-AMT technique thus provides hierarchically porous materials with mechanical properties tailored by the addition of thiol chain transfer agent. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The residual monomer content and mechanical properties of CAD\\CAM resins used in the fabrication of complete dentures as compared to heat cured resins

PubMed Central

Ayman, Al-Dharrab

2017-01-01

Background The utilization of computer-assisted designing and computer-assisted milling CAD\\CAM resins in the fabrication of removable prostheses is a modern-day concept that offers many advantages over the use of the traditional polymethylmethacrylate (PMMA). Aim This study instigated some of the mechanical properties of CAD\\CAM denture base resin including the amount of residual monomer. Methods This study was conducted at the Faculty of Dentistry, King Abdulaziz University from October 2016 to February 2017. A total of seventy rectangular specimens were fabricated (group A: 35 heat-cured PMMA and group B: 35 CAD/CAM pre-polymerized acrylic resin blocks). The flexural strength and surface hardness were tested while the residual monomer content at baseline, two-day and seven-day intervals was estimated using gas chromatography (GC). Means and standard deviations were determined for each group as well as independent-samples t-test and ANOVA with repeated measures for comparison between the groups and subgroups of varying time intervals. Results Heat cured PMMA (A), displayed higher flexural strength and low value flexural modulus compared to CAD/CAM acrylic resin denture base material (B). Student t-test indicated highly significant differences (p<0.001) of the flexural strength (t=37.911) and flexural modulus (t=88.559). The surface hardness of group (B) was significantly higher compared to group (A) as indicated by the t-test (t=20.430). Higher release of the monomer content was detected by GC in group (A) at different time intervals with a statistically significant difference (p<0.001) in residual monomer content. Conclusion CAD/CAM resin may be considered suitable for use in the construction of denture bases. PMID:28894533

Light insensitive silver(I) cyanoximates as antimicrobial agents for indwelling medical devices.

PubMed

Gerasimchuk, Nikolay; Gamian, Andrzej; Glover, Garrett; Szponar, Bogumila

2010-11-01

Ten silver(I) cyanoximates of AgL composition (L = NC-C(NO)-R, where R is electron withdrawing groups: -CN, -C(O)NR(2), -C(O)R' (alkyl), -C(O)OEt, 2-heteroaryl fragments such as 2-pyridyl, 2-benzimidazolyl, 2-benzoxazolyl, 2-benzthiazolyl) were synthesized and characterized using spectroscopic methods and X-ray analysis. Crystal structures of four complexes were determined and revealed the formation of two-dimensional (2D) coordination polymers of different complexity in which anions exhibit bridging or combined chelate and bridging binding modes. In these compounds, anions are in the nitroso form. All studied AgL complexes are sparingly soluble in water and are thermally stable to 150 °C. Synthesized compounds demonstrated remarkable insensitivity toward visible light and UV-radiation, which was explained based on their polymeric structures with multiple covalent bonds between bridging cyanoxime ligands and Ag(I) centers. All 10 silver(I) cyanoximates were tested in vitro on the subject of their antimicrobial activity against both Gram-positive and Gram-negative microorganisms such as Escherichia coli, Klebsiella pneumoniae, Proteus sp., Pseudomonas aeruginosa, Enterococcus hirae, Streptococcus mutans, Staphylococcus aureus, and Mycobacterium fortuitum as well as against Candida albicans in solutions, and in the solid state as pressed pellets and dried filter paper disks presoaked with solutions of AgL in DMF. Results showed pronounced antimicrobial activity for all investigated complexes. A combination of five factors: (1) light insensitivity, (2) poor water solubility, (3) high thermal stability, (4) lack of toxicity of organic ligands, and (5) in vitro antimicrobial activity allows development of silver(I) cyanoximates for medical applications. These include antimicrobial additives to acrylate glue, cured by UV-radiation, used in introduction of prosthetic joints and dental implants, and prevention of biofilm formation on several types of indwelling medical devices.

Process equipped with a sloped UV lamp for the fabrication of gradient-refractive-index lenses.

PubMed

Liu, Jui-Hsiang; Chiu, Yi-Hong

2009-05-01

In this investigation, a method for the preparation of gradient-refractive-index (GRIN) lenses by UV-energy-controlled polymerization has been developed. A glass reaction tube equipped with a sloped UV lamp was designed. Methyl methacrylate and diphenyl sulfide were used as the reactive monomer and nonreactive dopant, respectively. Ciba IRGACURE 184 (1-hydroxy-cyclohexyl-phenyl-ketone) was used as the initiator. The effects of initiator concentration, the addition of acrylic polymers, and the preparation conditions on the optical characteristics of the GRIN lenses produced by this method were also investigated. Refractive index distributions and image transmission properties were estimated for all GRIN lenses prepared.

Comparison of halogen, plasma and LED curing units.

PubMed

Nomoto, Rie; McCabe, John F; Hirano, Susumu

2004-01-01

This study evaluated the characteristics of two kinds of recently developed light-curing unit; plasma arc and blue light emitting diodes (LED), in comparison with a conventional tungsten-halogen light-curing unit. The light intensity and spectral distribution of light from these light-curing units, the temperature rise of the bovine enamel surface and the depth of cure of composites exposed to each unit were investigated. The light intensity and depth of cure were determined according to ISO standards. The spectral distributions of emitted light were measured using a spectro-radiometer. The temperature increase induced by irradiation was measured by using a thermocouple. Generally, light intensities in the range 400-515 nm emitted from the plasma arc were greater than those from other types. Light in the UV-A region was emitted from some plasma arc units. The required irradiation times were six to nine seconds for the plasma arc units and 40 to 60 seconds for the LED units to create a depth of cure equal to that produced by the tungsten-halogen light with 20 seconds of irradiation. The temperature increased by increasing the irradiation time for every light-curing unit. The temperature increases were 15 degrees C to 60 degrees C for plasma arc units, around 15 degrees C for a conventional halogen unit and under 10 degrees C for LED units. Both the plasma arc and LED units required longer irradiation times than those recommended by their respective manufacturers. Clinicians should be aware of potential thermal rise and UV-A hazard when using plasma arc units.

A Twofold Comparison between Dual Cure Resin Modified Cement and Glass Ionomer Cement for Orthodontic Band Cementation.

PubMed

Attar, Hanaa El; Elhiny, Omnia; Salem, Ghada; Abdelrahman, Ahmed; Attia, Mazen

2016-12-15

To test the solubility of dual cure resin modified resin cement in a food simulating solution and the shear bond strength compared to conventional Glass ionomer cement. The materials tested were self-adhesive dual cure resin modified cement and Glass Ionomer (GIC). Twenty Teflon moulds were divided into two groups of tens. The first group was injected and packed with the modified resin cement, the second group was packed with GIC. To test the solubility, each mould was weighed before and after being placed in an analytical reagent for 30 days. The solubility was measured as the difference between the initial and final drying mass. To measure the Shear bond strength, 20 freshly extracted wisdom teeth were equally divided into two groups and embedded in self-cure acrylic resin. Four mm sections of stainless steel bands were cemented to the exposed buccal surfaces of teeth under a constant load of 500 g. Shear bond strength was measured using a computer controlled materials testing machine and the load required to deband the samples was recorded in Newtons. GIC showed significantly higher mean weight loss and an insignificant lower Shear bond strength, compared to dual cure resin Cement. It was found that dual cure resin modified cement was less soluble than glass ionomer cement and of comparable bond strength rendering it more useful clinically for orthodontic band cementation.

Replication of cicada wing's nano-patterns by hot embossing and UV nanoimprinting.

PubMed

Hong, Sung-Hoon; Hwang, Jaeyeon; Lee, Heon

2009-09-23

The hydrophobicity of the cicada wing originates from its naturally occurring, surface nano-structure. The nano-structure of the cicada wing consists of an array of nano-sized pillars, 100 nm in diameter and 300 nm in height. In this study, the nano-structure of the cicada wing was successfully duplicated by using hot embossing lithography and UV nanoimprint lithography (NIL). The diameter and pitch of replication were the same as those of the original cicada wing and the height was a little smaller than that of the original master. The transmittance of the hot embossed PVC film was increased by 2-6% compared with that of the bare PVC film. The hydrophobicity was measured by water contact angle measurements. The water contact angle of the replica, made of UV cured polymer, was 132 degrees +/- 2 degrees , which was slightly lower than that of the original cicada wing (138 degrees +/- 2 degrees ), but much higher than that of the UV cured polymer surface without any nano-sized pillars (86 degrees ).

Effect of plasma pretreatment on adhesion and mechanical properties of UV-curable coatings on plastics

NASA Astrophysics Data System (ADS)

Gururaj, T.; Subasri, R.; Raju, K. R. C. Soma; Padmanabham, G.

2011-02-01

An attempt was made to study the effect of plasma surface activation on the adhesion of UV-curable sol-gel coatings on polycarbonate (PC) and polymethylmethacrylate (PMMA) substrates. The sol was synthesized by the hydrolysis and condensation of a UV-curable silane in combination with Zr-n-propoxide. Coatings deposited by dip coating were cured using UV-radiation followed by thermal curing between 80 °C and 130 °C. The effect of plasma surface treatment on the wettability of the polymer surface prior to coating deposition was followed up by measuring the water contact angle. The water contact angle on the surface of as-cleaned substrates was 80° ± 2° and that after plasma treatment was 43° ± 1° and 50° ± 2° for PC and PMMA respectively. Adhesion as well as mechanical properties like scratch resistance and taber abrasion resistance were evaluated for coatings deposited over plasma treated and untreated surfaces.

Biophysical characterization of functionalized titania nanoparticles and their application in dental adhesives.

PubMed

Sun, Jirun; Petersen, Elijah J; Watson, Stephanie S; Sims, Christopher M; Kassman, Alexander; Frukhtbeyn, Stanislav; Skrtic, Drago; Ok, Meryem T; Jacobs, Debbie S; Reipa, Vytas; Ye, Qiang; Nelson, Bryant C

2017-04-15

It is demonstrated that carboxylic acid-functionalized titanium dioxide (TiO 2 ) NPs produce significantly higher levels of reactive oxygen species (ROS) after visible light irradiation (400-800nm, 1600mW/cm 2 ) in comparison to nonfunctionalized TiO 2 NPs. The level of ROS produced under these irradiation conditions was not capable of generating oxidatively induced DNA damage in a cell-free system for TiO 2 concentrations of 0.5mg/L or 5mg/L. In addition, specific incorporation of the acrylic acid-functionalized TiO 2 NPs into dental composites allowed us to utilize the generated ROS to enhance photopolymerization (curing and degree of vinyl conversion (DC)) of resin adhesives and create mechanically superior and biocompatible materials for dental applications. Incorporation of the TiO 2 NPs into selected dental composites increased the mean DC values by ≈7%. The modified TiO 2 materials and dental composite materials were extensively characterized using thermogravimetric analysis, electron microscopy, Fourier transform infrared spectroscopy, and electron paramagnetic resonance. Notably, dental adhesives incorporated with acrylic acid-functionalized TiO 2 NPs produced stronger bonds to human teeth following visible light curing in comparison to traditional dental adhesives not containing NPs with an increase in the shear bond strength of ≈29%. In addition, no leaching of the incorporated NPs was detectable from the dental adhesives after 2500 thermal cycles using inductively coupled plasma-optical emission spectroscopy, indicating that biocompatibility of the adhesives was not compromised after extensive aging. These findings suggest that NP-induced ROS may be useful to produce enhanced nanocomposite materials for selected applications in the medical device field. Titanium dioxide nanoparticles (TiO 2 NPs) have unique photocatalytic, antibacterial and UV-absorbing properties that make them beneficial additives in adhesives and composites. However, there is concern that the reactive oxygen species (ROS) produced by photoactivated TiO 2 NPs might pose toxicological risks. We demonstrate that it is possible to incorporate acid-functionalized TiO 2 NPs into dental resins which can be applied as dental adhesives to human teeth. The ROS generated by these NPs through visible-light irradiation may be utilized to increase the degree of vinyl conversion of resins, leading to adhesives that have an enhanced shear-bond strength to human teeth. Investigation into the potential genotoxicity of the NPs and their potential for release from dental composites indicated a low risk of genotoxic effects. Published by Elsevier Ltd.

Advances in acrylic-alkyd hybrid synthesis and characterization

NASA Astrophysics Data System (ADS)

Dziczkowski, Jamie

2008-10-01

In situ graft acrylic-alkyd hybrid resins were formed by polymerizing acrylic and acrylic-mixed monomers in the presence of alkyds by introduction of a free radical initiator to promote graft formation. Two-dimensional NMR, specifically gradient heteronuclear multiple quantum coherence (gHMQC), was used to clarify specific graft sites of the hybrid materials. Both individual and mixed-monomer systems were produced to determine any individual monomer preferences and to model current acrylic-alkyd systems. Different classes of initiators were used to determine any initiator effects on graft location. The 2D-NMR results confirm grafting at doubly allylic hydrogens located on the fatty acid chains and the polyol segment of the alkyd backbone. The gHMQC spectra show no evidence of grafting across double bonds on either pendant fatty acid groups or THPA unsaturation sites for any of the monomer or mixed monomer systems. It was also determined that choice of initiator has no effect on graft location. In addition, a design of experiments using response surface methodology was utilized to obtain a better understanding of this commercially available class of materials and relate both the chemical and physical properties to one another. A Box-Behnkin design was used, varying the oil length of the alkyd phase, the degree of unsaturation in the polyester backbone, and acrylic to alkyd ratio. Acrylic-alkyd hybrid resins were reduced with an amine/water mixture. Hydrolytic stability was tested and viscoelastic properties were obtained to determine crosslink density. Cured films were prepared and basic coatings properties were evaluated. It was found that the oil length of the alkyd is the most dominant factor for final coatings properties of the resins. Acrylic to alkyd ratio mainly influences the resin properties such as acid number, average molecular weight, and hydrolytic stability. The degree of unsaturation in the alkyd backbone has minimal effects on resin and film performance. Reversible-addition fragmentation polymerization techniques were employed to create a new class of acrylic-alkyd hybrid materials. Medium and long oil alkyds made from the monoglyceride process using soybean oil, glycerol, and phthalic anhydride were modified with a RAFT chain transfer agent. The alkyd macro-RAFT agents were reached by end-capping a medium oil soya-based alkyd with a carboxy-functional trithiocarbonate. The alkyd macro-RAFT agents were then used to create acrylic-alkyd block structures by polymerizing different acrylic monomers, including both acrylates and methacrylates in the presence of the macro-RAFT agent and 2, 2'-azobisisobutyronitrile (AIBN). Co-acrylic segments were reached by complete polymerization of one monomer followed by the addition of a second monomer and additional free radical initiator. The alkyds, macro-RAFT agents and, acrylic-alkyd blocks were characterized by size-exclusion chromatography (SEC), FTIR, and 1H-NMR. Pseudo-first-order kinetics behavior and conversion vs. molecular weight plots show that the RAFT-mediated reaction afforded a more controlled process for the synthesis of acrylated-alkyd materials. Preliminary coatings tests showed that material properties of acrylated-alkyds achieved by RAFT polymerization exhibit good overall coatings properties including adhesion, gloss, hardness, and impact resistance.

Deformation and flexural properties of denture base polymer reinforced with glass fiber sheet.

PubMed

Kanie, Takahito; Arikawa, Hiroyuki; Fujii, Koichi; Ban, Seiji

2005-09-01

The purpose of this study was to investigate the deformation and flexural properties of acrylic and urethane polymers reinforced with glass fiber sheet. Four types of specimen--self-curing resin plate (R), light-curing oligomer plate containing a reinforcement (GO), and self-curing resin plate containing a reinforcement on one (GR) or both (GRG) sides--were prepared with three thicknesses: 1.5, 2.4, and 3.0 mm. Gaps between polymerized test specimen and a standard metal plate were measured at the corner (C), middle of the long sides (LS), and middle of the short sides (SS). The gaps for R were 0-2.0 microm. GO and GR markedly deformed at Points C, LS, and SS, and the degree of deformation increased as GO became thinner. Flexural strength was significantly increased by the reinforcement (p < 0.05). The flexural moduli of 3.0-mm thick R, GO, and GR were significantly smaller than that of 1.5-mm thick specimens.

Electron beam-induced graft polymerization of acrylic acid and immobilization of arginine-glycine-aspartic acid-containing peptide onto nanopatterned polycaprolactone.

PubMed

Sun, Hui; Wirsén, Anders; Albertsson, Ann-Christine

2004-01-01

Electron beam- (EB-) induced graft polymerization of acrylic acid and the subsequent immobilization of arginine-glycine-aspartic acid (RGD) peptide onto nanopatterned polycaprolactone with parallel grooves is reported. A high concentration of carboxylic groups was introduced onto the polymer substrate by EB-induced polymerization of acrylic acid. In the coupling of the RGD peptide to the carboxylated polymer surface, a three-step peptide immobilization process was used. This process included the activation of surface carboxylic acid into an active ester intermediate by use of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS), the introduction of disulfide groups by use of 2-(2-pyridinyldithio)ethanamine hydrochloride (PDEA), and final immobilization of the peptide via a thiol-disulfide exchange reaction. The extent of coupling was measured by UV spectroscopy. A preliminary study of the in vitro behavior of keratinocytes (NCTC 2544) cultured on the acrylic acid-grafted and RGD peptide-coupled surface showed that most cells grown on the coupled samples had a spread-rounded appearance, while the majority of cells tended to be elongated along the grooves on uncoupled substrates.

Radiation induced deposition of copper nanoparticles inside the nanochannels of poly(acrylic acid)-grafted poly(ethylene terephthalate) track-etched membranes

NASA Astrophysics Data System (ADS)

Korolkov, Ilya V.; Güven, Olgun; Mashentseva, Anastassiya A.; Atıcı, Ayse Bakar; Gorin, Yevgeniy G.; Zdorovets, Maxim V.; Taltenov, Abzal A.

2017-01-01

Poly(ethylene terephthalate) PET, track-etched membranes (TeMs) with 400 nm average pore size were UV-grafted with poly(acrylic acid) (PAA) after oxidation of inner surfaces by H2O2/UV system. Carboxylate groups of grafted PAA chains were easily complexed with Cu2+ ions in aqueous solutions. These ions were converted into metallic copper nanoparticles (NPs) by radiation-induced reduction of copper ions in aqueous-alcohol solution by gamma rays in the dose range of 46-250 kGy. Copper ions chelating with -COOH groups of PAA chains grafted on PET TeMs form polymer-metal ion complex that prevent the formation of agglomerates during reduction of copper ions to metallic nanoparticles. The detailed analysis by X-Ray diffraction technique (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) confirmed the deposition of copper nanoparticles with the average size of 70 nm on the inner surface of nanochannels of PET TeMs. Samples were also investigated by FTIR, ESR spectroscopies to follow copper ion reduction.

Photosensitive dissolution inhibitors and resists based on onium salt carboxylates

DOEpatents

Dentinger, Paul M.; Simison, Kelby L.

2005-11-29

A photoresist composition that employs onium salt carboxylates as thermally stable dissolution inhibitors. The photoresist composition can be either an onium carboxylate salt with a phenolic photoresist, such as novolac, or an onium cation protected carboxylate-containing resin such as an acrylic/acrylic acid copolymer. The onium carboxylate can be an onium cholate, wherein the onium cholate is an iodonium cholate. Particularly preferred iodonium cholates are alkyloxyphenylphenyl iodonium cholates and most particularly preferred is octyloxyphenyphenyl iodonium cholate. The photoresist composition will not create nitrogen or other gaseous byproducts upon exposure to radiation, does not require water for photoactivation, has acceptable UV radiation transmission characteristics, and is thermally stable at temperatures required for solvent removal.

Comparison of self-written waveguide techniques and bulk index matching for low-loss polymer waveguide interconnects

NASA Astrophysics Data System (ADS)

Burrell, Derek; Middlebrook, Christopher

2016-03-01

Polymer waveguides (PWGs) are used within photonic interconnects as inexpensive and versatile substitutes for traditional optical fibers. The PWGs are typically aligned to silica-based optical fibers for coupling. An epoxide elastomer is then applied and cured at the interface for index matching and rigid attachment. Self-written waveguides (SWWs) are proposed as an alternative to further reduce connection insertion loss (IL) and alleviate marginal misalignment issues. Elastomer material is deposited after the initial alignment, and SWWs are formed by injecting ultraviolet (UV) light into the fiber or waveguide. The coupled UV light cures a channel between the two differing structures. A suitable cladding layer can be applied after development. Such factors as longitudinal gap distance, UV cure time, input power level, polymer material selection and choice of solvent affect the resulting SWWs. Experimental data are compared between purely index-matched samples and those with SWWs at the fiber-PWG interface. It is shown that < 1 dB IL per connection can be achieved by either method and results indicate lowest potential losses associated with a fine-tuned self-writing process. Successfully fabricated SWWs reduce overall processing time and enable an effectively continuous low-loss rigid interconnect.

Workers' dermal exposure to UV-curable acrylates in the furniture and Parquet industry.

PubMed

Surakka, J; Lindh, T; Rosén, G; Fischer, T

2000-12-01

The use of ultraviolet radiation-curable coatings (UV-coatings) has increased rapidly in the parquet and furniture industry. Work with UV-coatings involves risk from skin exposure to chemically reactive, concentrated acrylates that are known skin contact irritants and sensitizers. Yet, the methods and tools for measuring and quantifying dermal exposure from hazardous chemicals directly on the skin are limited and methods to measure skin exposure to UV-coatings in occupational or environmental settings have been lacking. Skin exposure to UV-coatings was measured employing a quantitative tape stripping method that we have developed for this purpose. A pilot study was performed at three workplaces. In the main study, workers' skin exposure to uncured UV-coatings was measured at seven workplaces and on two separate workdays (rounds 1 and 2) within a six-month period to determine exposure variation. Skin exposure was measured at four standardized sites on the hand, 3-4 times per work shift. The forehead was sampled once. A questionnaire was carried out with the workers in both rounds to find out factors that can affect skin exposure to UV-coatings. The pilot study indicated that both skin and surface contamination to TPGDA-containing UV-coatings were common and varied up to 2110 microgram on the sampling area of 10cm(2). In the main study skin contamination due to TPGDA was found on 16 of 23 workers, at 6 out of the 7 workplaces, and from 36 (5. 4%) of the 664 samples. In round one 8.6% (n=383) of the samples contained TPGDA and in round two 1.1 % (n=281). The average TPGDA mass on all the positive samples (n=36) was 30.4+/-77.0 microgram for the first and second rounds alone this mass was 30.6+/-80 (n=33) and 28.3+/-16.5 microgram (n=3), respectively. Despite the limited sampling area and sampling sites, we could find residues of TPGDA at all sampling times, even at the beginning of the work shift. This may be due to transfer of UV-coatings through contaminated equipment, shoes and surfaces. Our study indicates that there is a risk of harmful skin exposure to UV-coatings in the furniture and parquet industry.

Protective effects of platinum nanoparticles against UV-light-induced epidermal inflammation.

PubMed

Yoshihisa, Yoko; Honda, Ayumi; Zhao, Qing-Li; Makino, Teruhiko; Abe, Riichiro; Matsui, Kotaro; Shimizu, Hiroshi; Miyamoto, Yusei; Kondo, Takashi; Shimizu, Tadamichi

2010-11-01

Intracellular reactive oxygen species (ROS) and apoptosis play important roles in the ultraviolet (UV)-induced inflammatory responses in the skin. Metal nanoparticles have been developed to increase the catalytic activity of metals, which is because of the large surface area of smaller particles. Platinum nanoparticles (nano-Pt) protected by poly acrylic acid were manufactured by reduction with ethanol. A marked increase in ROS production was observed in UV-treated HaCaT keratinocytes cell lines, while a decrease in ROS production was observed in nano-Pt-treated cells. Pretreatment of the cells with nano-Pt also caused a significant inhibition of UVB- and UVC-induced apoptosis. Furthermore, we found that mice treated with nano-Pt gel prior to UV irradiation showed significant inhibition of UVB-induced inflammation and UVA-induced photoallergy compared to UV-irradiated control mice. These results suggest that nano-Pt effectively protects against UV-induced inflammation by decreasing ROS production and inhibiting apoptosis in keratinocytes. © 2010 John Wiley & Sons A/S.

Synthesis, Structure, and Film Properties of Novel low-k UV-active Polycarbosilanes with Embedded Disilacyclobutanes

NASA Astrophysics Data System (ADS)

LeFevre, Scott W.

The phenylene-bridged cyclolinear polycarbosilane (PBCLPCS) was synthesized via Grignard coupling from 1,4-bis(bromomagnesio)benzene with 1,3-dichloro-, and 1,3-diethoxy-1,3-disilacyclobutanes (DCDSCB, and DEDSCB respectively). Investigation of the resulting chemical structures by nuclear magnetic resonance spectroscopy (NMR) revealed a wide array of possible end groups and thus termination mechanisms. Temperature-gradient interaction chromatography (TGIC) was employed as an effective separation tool to achieve a predominantly monomer-by-monomer separation of the low molecular weight reaction products. Further analysis of the TGIC fractions by matrix-assisted laser desorption ionization mass spectrometry with time of flight detection (MALDI-ToF) allowed for a much more detailed study of chemical structure, revealing very different primary modes of termination for the two synthesis schemes. While the slightly more reactive Si-Cl groups from DCDSCB are more sensitive to multiple side reactions including hydrolysis, it was shown that the primary end groups were phenyl rings, indicating a possible imbalance in stoichiometry favoring the aryl-Grignard reagent. The DEDSCB-based synthesis has fewer side reactions, as indicated by few groupings of MALDI peaks at regular intervals equal to the repeat unit molecular weight; however the primary end groups were unreacted ethoxy moieties, and a bromine terminated phenyl ring. This indicates that the primary modes of termination were either limited chain growth from the less reactive ethoxy groups, or incomplete formation of the di-Grignard. The optical, UV-curing and thin film characteristics of PBCLPCS were investigated to gain an understanding of the unique film properties of this new class of material. Upon UV-curing PBCLPCS, the chromophore blue shifts 11nm but still absorbs appreciably at 254nm, leading to UV attenuation at greater depths within a film. The thickness dependent UV-curing characteristics were investigated and it was found that the apparent quantum efficiencies for 20 nm and 210 nm thick films are 2.75 and 2% respectively, corresponding to 180mJ and 2.5J of UV irradiation required to achieve a fully cured sample. A UV-dosage dependent film thickness relationship was derived from confocal Raman depth profiles, and it was found that the maximum thickness attainable is 40 microns. The physical effects on thin films of PBCLPCS before and after UV irradiation was examined, and while it was found that there is approximately 17% shrinkage in film thickness that occurs, this is accompanied by a reduction in film roughness. For the thickest films (> 150nm), the surface roughness drops from roughly 14% to 7% in height variation, while for films <100nm a final surface roughness of 1-2% is consistently observed. The films also retain a high degree of hydrophobicity after curing (>100° water contact angle). To test the photoresist capabilities of these films various photomasks were employed showing feature sizes down to 1mum in width with surface roughness variations consistent with that of non-patterned films. There was a 18%-50% expansion of cured polymer beyond the photomask, depending on the feature size. Finally the synthesis of 1-(4-(dimethyl(phenyl)silyl)phenyl)-1,3,3-trimethyl-1,3-disilacyclobutane (DMPSP-DSCB), an extended chromophore (SiDSCB-C6H4-Si-C 6H4-) small molecule variant of PBCLPCS was carried out, where SiDSCB represents silicon atoms within a disilacyclobutane ring. The UV absorption and molar absorptivity at longer wavelengths was shown to increase along with the observed secondary absorption bands. A red shift of approximately 2 nm was observed compared to its trimethylsilylbenzene-DSCB (TMSB-DSCB) analogue. The observed red shift in UV absorption allows for improved ring-opening (RO) conversion efficiencies of the disilacyclobutane ring by 30% after 2 hours irradiation of the compared to the single Ph substituted chromophore (Si DSCB-C6H4-Si) 1,1,3-trimethyl-3-(4-(trimethylsilyl)phenyl)-1,3-disilacyclobutane.

Development and characterization of adjustable refractive index scattering epoxy acrylate polymer layers

NASA Astrophysics Data System (ADS)

Eiselt, Thomas; Preinfalk, Jan; Gleißner, Uwe; Lemmer, Uli; Hanemann, Thomas

2016-09-01

This work presents different polymer diffusing films for optical components. In optical applications it is sometimes important to have a film with an adjusted refractive index, scattering properties and a low surface roughness. These diffusing films can be used to increase the efficiency of optical components like organic light emitting diodes (OLEDs). In this study three different epoxy acrylate mixtures containing Syntholux 291 EA, bisphenol a glycerolate dimethacrylate, Sartomer SR 348 L are characterized and optimized with different additives. The adjustable refractive index of the material is achieved with a chemical doping by 9-vinylcarbazole. Titanium nanoparticles in the mixtures generate light scattering and increase the refractive index additionally. To prevent sedimentation and agglomeration of these nanoparticles, a stabilization agent [2-(2-methoxyethoxy)ethoxy]acetic acid is added to the mixture. Other ingredients are a UV-starter and thermal starter for the radical polymerization. A high power stirrer (ultraturrax) is used to mix and disperse all chemical substances together to a homogenous mixture. The viscosity behavior of the mixtures is an important property for the selection of the production method and gets characterized. After the mixing, the monomer mixture is applied on glass substrates by blade coating or screen printing. To initiate the chain growing (polymerization) the produced films are irradiated for 10 minutes long with UV light (UV LED Spot Hönle, 405 nm). After this step a final post bake from the layers in the oven (150°C, 30 min.) is operated. Light transmission measurements (UV-Vis) of the polymer matrix and roughness measurements complement the characterization.

Light scattering and light transmittance of cadaver eye-explanted intraocular lenses of different materials.

PubMed

Morris, Caleb; Werner, Liliana; Barra, Daniel; Liu, Erica; Stallings, Shannon; Floyd, Anne

2014-01-01

To evaluate light scattering and light transmittance in cadaver eye-explanted intraocular lenses (IOLs) manufactured from different materials. John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. Experimental study. Forty-nine pseudophakic cadaver eyes were selected according to IOL material/type and implantation duration, and the IOLs were explanted. Hydrophobic acrylic, hydrophilic acrylic, poly(methyl methacrylate) (PMMA), and silicone IOLs were included. Gross and light microscopy was performed for all IOLs. Light scattering was measured with an EAS 1000 Scheimpflug camera, and light transmittance was assessed using a Lambda 35 UV/Vis spectrophotometer (single-beam configuration with an RSA PE-20 integrating sphere). Analyses were performed at room temperature in the hydrated state and compared with analyses of controls. The highest levels of surface light scattering were measured for 3-piece hydrophobic acrylic, which was also the IOL type with the longest implantation duration among the Acrysof hydrophobic acrylic IOLs. Hydrophilic acrylic, PMMA, and silicone IOLs exhibited relatively low light-scattering levels. The lowest light-scattering levels were observed with PMMA IOLs (1-piece looped and 3-piece) and plate silicone IOLs, which represent the IOL types with the longest implantation duration in this series. Light transmittance values measured for all IOL types appeared to be similar to the values of the corresponding control IOLs. The phenomenon of surface light scattering (nanoglistenings) is more particularly related to hydrophobic acrylic IOLs and increases with implantation time. No significant effect of surface light scattering on IOL light transmittance was found. Copyright © 2013 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Self-initiation of UV photopolymerization reactions using tetrahalogenated bisphenol A (meth)acrylates.

PubMed

Pelras, Théophile; Knolle, Wolfgang; Naumov, Sergej; Heymann, Katja; Daikos, Olesya; Scherzer, Tom

2017-05-17

The potential of tetrachlorinated and tetrabrominated bisphenol A diacrylates and dimethacrylates for self-initiation of a radical photopolymerization was investigated. The kinetics of the photopolymerization of an acrylic model varnish containing halogenated monomers was studied by real-time FTIR spectroscopy, whereas the formation of reactive species and secondary products was elucidated by laser flash photolysis and product analysis by GC-MS after steady-state photolysis. The interpretation of the experimental data and the analysis of possible reaction pathways were assisted by quantum chemical calculations. It was shown that all halogenated monomers lead to a significant acceleration of the photopolymerization kinetics at a minimum concentration of 5 wt%. Steady-state and laser flash photolysis measurements as well as quantum chemical calculations showed that brominated and chlorinated samples do not follow the same pathway to generate radical species. Whereas chlorinated (meth)acrylates may cleave only at the C-O bonds of the carboxyl groups resulting in acrolein and oxyl radicals for initiation, brominated monomers may cleave either at the C-O bonds or at the C-Br bonds delivering aryl and bromine radicals. The quantum yields for the photolysis of the halogenated monomers were found to be in the order of 0.1 for acrylates and 0.2 for methacrylates (with an estimated error of 25%), independently of the attached Br and Cl halogens. Finally, the trihalogenated bisphenol A di(meth)acrylate radicals and the acrolein radicals were found to show the highest efficiencies for the reaction with another acrylic double bond leading to the formation of a polymer network.

Acrylate-induced allergic contact dermatitis in a car windscreen repairer.

PubMed

Fremlin, G; Sansom, J

2014-10-01

We report a case of an allergic skin reaction to ultraviolet-cured acrylates in a windscreen repair worker. The patient presented with a 6 month history of fingertip dryness, vesicles and desquamation. He had worked as a self-employed car windscreen repairer for 19 years. Previous management with vinyl glove protection and treatment with clobetasol propionate ointment had produced little improvement. He was patch tested to the British Society for Cutaneous Allergy standard and preservatives series and to the two acrylates used in his work environment, identified using safety data sheets, methyl methacrylate 2% pet and 2-hydroxyethylmethacrylate (2-HEMA) 2% pet. A positive reaction was seen at Day 4 to 2-HEMA, but all other patch tests were negative. An occupational allergic contact dermatitis to 2-HEMA was diagnosed. The patient was given avoidance advice and advised to use nitrile gloves. Although he was unable to give up his current work, he has continued his job using nitrile gloves with marked improvement. © The Author 2014. Published by Oxford University Press on behalf of the Society of Occupational Medicine. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Thermal and mechanical properties of palm oil-based polyurethane acrylate/clay nanocomposites prepared by in-situ intercalative method and electron beam radiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Salih, A. M.; Ahmad, Mansor Bin; Ibrahim, Nor Azowa

2014-02-12

Palm oil based-polyurethane acrylate (POBUA)/clay nanocomposites were prepared via in-situ intercalative polymerization using epoxidized palm oil acrylate (EPOLA) and 4,4' methylene diphenyl diisocyante (MDI). Organically modified Montmorillonite (ODA-MMT) was incorporated in EPOLA (1, 3 and 5%wt), and then subjected to polycondensation reaction with MDI. Nanocomposites solid films were obtained successfully by electron beam radiation induced free radical polymerization (curing). FTIR results reveal that the prepolymer was obtained successfully, with nanoclay dispersed in the matrix. The intercalation of the clay in the polymer matrix was investigated by XRD and the interlayer spacing of clay was found to be increased up tomore » 37 Å, while the structure morphology of the nanocomposites was investigated by TEM and SEM. The nanocomposites were found to be a mixture of exfoliated and intercalated morphologies. The thermal stability of the nanocomposites was significantly increased by incorporation of nanoclay into the polymer matrix. DSC results reveal that the Tg was shifted to higher values, gradually with increasing the amount of filler in the nanocomposites. Tensile strength and Young's modulus of the nanocomposites showed remarkable improvement compared to the neat POBUA.« less

The Soft Palate Friendly Speech Bulb for Velopharyngeal Insufficiency.

PubMed

Kahlon, Sukhdeep Singh; Kahlon, Monaliza; Gupta, Shilpa; Dhingra, Parvinder Singh

2016-09-01

Velopharyngeal insufficiency is an anatomic defect of the soft palate making palatopharyngeal sphincter incomplete. It is an important concern to address in patients with bilateral cleft lip and palate. Speech aid prosthesis or speech bulbs are best choice in cases where surgically repaired soft palate is too short to contact pharyngeal walls during function but these prosthesis have been associated with inadequate marginal closure, ulcerations and patient discomfort. Here is a case report of untreated bilateral cleft lip and palate associated with palatal insufficiency treated by means of palate friendly innovative speech bulb. This modified speech bulb is a combination of hard acrylic and soft lining material. The hard self-curing acrylic resin covers only the hard palate area and a permanent soft silicone lining material covering the soft palate area. A claw-shaped wire component was extended backwards from acrylic and was embedded in soft silicone to aid in retention and approximation of two materials. The advantage of adding the soft lining material in posterior area helped in covering the adequate superior extension and margins for maximal pharyngeal activity. This also improved the hypernasality, speech, comfort and overall patient acceptance.

Nanostructures and surface hydrophobicity of self-assembled thermosets involving epoxy resin and poly(2,2,2-trifluoroethyl acrylate)-block-poly(ethylene oxide) amphiphilic diblock copolymer.

PubMed

Yi, Fangping; Zheng, Sixun; Liu, Tianxi

2009-02-19

Poly(2,2,2-trifluoroethyl acrylate)-block-poly(ethylene oxide) (PTFEA-b-PEO) amphiphilic diblock copolymer was synthesized via the reversible addition-fragmentation transfer polymerization of 2,2,2-triffluroethyl acrylate with dithiobenzoyl-terminated poly(ethylene oxide) as a chain-transfer agent. The amphiphilic diblock copolymer was incorporated into epoxy resin to prepare the nanostructured epoxy thermosets. The nanostructures were investigated by means of atomic force microscopy, small-angle X-ray scattering, and dynamic mechanical analysis. In terms of the miscibility of the subchains of the block copolymer with epoxy after and before curing reaction, it is judged that the formation of the nanostructures follows the mechanism of self-assembly. The static contact angle measurements indicate that the nanostructured thermosets containing PTFEA-b-PEO diblock copolymer displayed a significant enhancement in surface hydrophobicity as well as a reduction in surface free energy. The improvement in surface properties was ascribed to the enrichment of the fluorine-containing subchain (i.e., PTFEA block) of the amphiphilic diblock copolymer on the surface of the nanostructured thermosets, which was evidenced by surface atomic force microscopy and energy-dispersive X-ray spectroscopy.

Preparation and characterization of polymeric nanocomposite films for application as protective coatings

NASA Astrophysics Data System (ADS)

Gagliardi, S.; Rondino, F.; D'Erme, C.; Persia, F.; Menchini, F.; Santarelli, M. L.; Paulke, B.-R.; Enayati, A. L.; Falconieri, M.

2017-08-01

Addiction of ceramic nanoparticles to acrylic polymers provides a simple and effective means to produce paints with important properties, such as mechanical resistance and tailored wettability, even though for optimal performances, an engineered nanoparticle distribution would be desirable. In this paper we report on the realization and on the morphological and functional characterization of nanocomposites where the nanophase is distributed on the surface of acrylic polymer films, in order to enhance the expression of surface-related properties. To this aim, commercial titanium oxide and silicon oxide nanopowders were dispersed in water and the suspensions were air-sprayed on polymeric films prepared by paint brushing, thus producing a nanostructured ceramic surface coating. Control of the pH of suspensions and acrylic acid functionalization of the surface of titania were used together with high power ultrasonic treatments in order to control dimension of the aggregates in the sprayed suspensions. Optical microscopy, mechanical profilometry, and atomic force microscopy were used to characterize the nanocomposite surface morphology and correlate it to the coating functional properties, evaluated through mechanical abrasion tests and contact angle measurements; also, colorimetry on coated stones was performed in order to test the impact of the coatings on the aesthetical appearance and their photostability under UV irradiation. Results show that the nanostructured ceramic layer slightly improves the resistance of coatings to mechanical abrasion in case of polymer films prepared from latexes. The nanocomposite surface layer does not affect the wettability of the polymer, which remained slightly hydrophilic; this behavior is likely due to inadequate distribution of the nanophase. On the other hand UV-induced superhydrophilicity was observed when the concentration of surface titania nanoparticles is about 0.6 mg/cm2. Colorimetric analysis on historical and Carrara marbles before and after coating evidenced the good transparency of the nanocomposites. Accelerated aging tests permitted to demonstrate that, on the historical marbles, the presence of the nanoparticles has a protective action against UV-induced damage of the underlying polymer film, preventing photodegradation.

CAD/CAM Handbook for Polymer Composite Reliability. Volume II. Figures and Tables.

DTIC Science & Technology

1983-03-01

for 177*C (350°F) service temperature epoxy resins ....................... 149 5-2 Repeat structure for 50:50 mole % isoamyl acrylate = neopentyl...and measured Tg (X’s) for Hercules 3501-5 epoxy resin (see Table 1-6 and Ref. 44) ................. 162 Chapter 6 6-1 Tensile response of C2F...173 6-12 Calculated (X) and experiment (.) effects of moisture on T_ of six cured epoxy resins (3501-5, 3501-6, 5208

Abrasion-Resistant Aluminized-Coated Aramid Fabrics for Manufacture of Firefighters’ Protective Clothing

DTIC Science & Technology

1985-05-01

OK 3-600 IV -5 D. ELECTRON-BEAM (EB) CURABLE "OATINGS These coatings are formed by curing or crosslinking a complex mixture of multifunctional acrylic ...1. 8p. Cooper, B.E., D.W. Butler, inventors; Dow Coming Corp., assignee. Curable siloxane resin coating composition. EP patent 048,114. (1982) March...limit use in the water-prone firefighters environment. We believe other high-temperature melting resins , such as polysulfone or polyether-imide, would

Variations in Flexural Strength of Heat-polymerized Acrylic Resin after the Usage of Denture Cleansers.

PubMed

Ragher, Mallikarjuna; Vinayakumar, G; Patil, Sanketsopan; Chatterjee, Aishwarya; Mallikarjuna, D M; Dandekeri, Savita; Swetha, V; Pradeep, M R

2016-04-01

The objective of this study was to evaluate and compare changes in the flexural strength of heat-cured denture base resins when treated using denture cleansers. A total of 40 specimens with dimension 65 mm length, 10 mm width, and 3 mm thickness were prepared as per ISO 1567 specification. A total of 10 specimens were immersed in distilled water to be used as control. Of the remaining 30 samples, 10 were treated with Clinsodent, 10 with VI-Clean, and 10 with Clanden denture cleansers. Specimens in each group were subjected to three-point flexural load in universal testing machine at a cross-head speed of 5 mm/min. The peak load (N) was recorded and flexural strength was calculated. The findings were analyzed using Kruskal-Wallis analysis of variance and Mann-Whitney test. Heat-cured denture base resin selected for this study showed significant difference in flexural strength after immersion in denture cleansers Clinsodent, VI-Clean, and Clanden solutions, when compared with the control group. Findings of this study showed that denture cleansers altered the flexural strength of heat polymerized acrylic resins that endured soaking cycles which simulated 180 days of use. Hence, denture cleansers should be used with caution, once a day after brushing the dentures. It is advisable for patients to follow the manufacturer's instructions.

In Vitro Comparative Evaluation of Different Types of Impression Trays and Impression Materials on the Accuracy of Open Tray Implant Impressions: A Pilot Study

PubMed Central

Gupta, Sonam; Balakrishnan, Dhanasekar

2017-01-01

Purpose. For a precise fit of multiple implant framework, having an accurate definitive cast is imperative. The present study evaluated dimensional accuracy of master casts obtained using different impression trays and materials with open tray impression technique. Materials and Methods. A machined aluminum reference model with four parallel implant analogues was fabricated. Forty implant level impressions were made. Eight groups (n = 5) were tested using impression materials (polyether and vinylsiloxanether) and four types of impression trays, two being custom (self-cure acrylic and light cure acrylic) and two being stock (plastic and metal). The interimplant distances were measured on master casts using a coordinate measuring machine. The collected data was compared with a standard reference model and was statistically analyzed using two-way ANOVA. Results. Statistically significant difference (p < 0.05) was found between the two impression materials. However, the difference seen was small (36 μm) irrespective of the tray type used. No significant difference (p > 0.05) was observed between varied stock and custom trays. Conclusions. The polyether impression material proved to be more accurate than vinylsiloxanether impression material. The rigid nonperforated stock trays, both plastic and metal, could be an alternative for custom trays for multi-implant impressions when used with medium viscosity impression materials. PMID:28348595

Preparation and properties studies of UV-curable silicone modified epoxy resin composite system.

PubMed

Yu, Zhouhui; Cui, Aiyong; Zhao, Peizhong; Wei, Huakai; Hu, Fangyou

2018-01-01

Modified epoxy suitable for ultraviolet (UV) curing is prepared by using organic silicon toughening. The curing kinetics of the composite are studied by dielectric analysis (DEA), and the two-phase compatibility of the composite is studied by scanning electron microscopy (SEM). The tensile properties, heat resistance, and humidity resistance of the cured product are explored by changing the composition ratio of the silicone and the epoxy resin. SEM of silicone/epoxy resin shows that the degree of cross-linking of the composites decreases with an increase of silicone resin content. Differential thermal analysis indicates that the glass transition temperature and the thermal stability of the composites decrease gradually with an increase of silicone resin content. The thermal degradation rate in the high temperature region, however, first decreases and then increases. In general, after adding just 10%-15% of the silicone resin and exposing to light for 15 min, the composite can still achieve a better curing effect. Under such conditions, the heat resistance of the cured product decreases a little. The tensile strength is kept constant so that elongation at breakage is apparently improved. The change rate after immersion in distilled water at 60°C for seven days is small, which shows excellent humidity resistance.

UV-cured adhesives for carbon fiber composite applications

NASA Astrophysics Data System (ADS)

Lu, Hsiao-Chun

Carbon fiber composite materials are increasingly used in automobile, marine, and aerospace industries due to their unique properties, including high strength, high stiffness and low weight. However, due to their brittle characteristic, these structures are prone to physical damage, such as a bird strike or impact damage. Once the structure is damaged, it is important to have fast and reliable temporary repair until the permanent repair or replacement can take place. In this dissertation, UV-based adhesives were used to provide a bonding strength for temporary repair. Adhesively bonded patch repair is an efficient and effective method for temporary repair. In this study, precured patches (hard patches) and dry fabric patches with laminating resins (soft patches) were performed. UV-based epoxy adhesives were applied to both patch repair systems. For precured patch repair, the bonding strengths were investigated under different surface treatments for bonding area and different adhesives thicknesses. The shear stresses of different UV exposure times and curing times were tested. Besides, the large patch repair was investigated as well. For soft patch repair, the hand wet lay-up was applied due to high viscosity of UV resins. A modified single lap shear testing (ASTM D5868) was applied to determine the shear stress. The large patches used fiber glass instead of carbon fiber to prove the possibility of repair with UV epoxy resin by hand wet lay-up process. The hand lay-up procedure was applied and assisted by vacuum pressure to eliminate the air bubbles and consolidate the patches. To enhance the bonding strength and effective soft patch repair, vacuum assisted resin transferring molding (VaRTM) is the better option. However, only low viscosity resins can be operated by VaRTM. Hence, new UV-based adhesives were formulated. The new UV-based adhesives included photoinitiator (PI), epoxy and different solvents. Solvents were used to compound the photoinitiator into epoxy monomer. Acetone, tetrahydrofuran (THF) and chloroform were used as well as their anhydrous solvents. The UV exposure times and curing times of new UV-based resins were tested. FT-IR, DSC and DMA were used to investigate structure, glass transition temperatures(Tg) and properties of polymer. In summary, the UV-based adhesive was applied to adhesively bonded hard patch and soft patch repair. In addition, new UV-based resins were formulated for the VaRTM process. The in-field repair can be effective and efficient by using UV adhesives.

Tensile bond strength of filled and unfilled adhesives to dentin.

PubMed

Braga, R R; Cesar, P F; Gonzaga, C C

2000-04-01

To determine the tensile bond strength of three filled and two unfilled adhesives applied to bovine dentin. Fragments of the labial dentin of bovine incisors were embedded in PVC cylinders with self-cure acrylic resin, and ground flat using 200 grit and 600 grit sandpaper. The following adhesive systems were tested (n=10): Prime & Bond NT, Prime & Bond NT dual cure, Prime & Bond 2.1, OptiBond Solo and Single Bond. A 3 mm-diameter bonding surface was delimited using a perforated adhesive tape. After etching with 37% phosphoric acid and adhesive application, a resin-based composite truncated cone (TPH, shade A3) was built. Tensile test was performed after 24 hrs storage in distilled water at 37 degrees C. Failure mode was accessed using a x10 magnification stereomicroscope. Weibull statistical analysis revealed significant differences in the characteristic strength between Single Bond and Prime & Bond NT dual cure, and between Single Bond and Prime & Bond 2.1. The Weibull parameter (m) was statistically similar among the five groups. Single Bond and Prime & Bond NT showed areas of dentin cohesive failure in most of the specimens. For OptiBond Solo, Prime & Bond NT dual cure and Prime & Bond 2.1 failure was predominantly adhesive.

Color stability and flexural strength of poly (methyl methacrylate) and bis-acrylic composite based provisional crown and bridge auto-polymerizing resins exposed to beverages and food dye: an in vitro study.

PubMed

Gujjari, Anil K; Bhatnagar, Vishrut M; Basavaraju, Ravi M

2013-01-01

To evaluate the color stability and flexural strength of poly (methyl methacrylate) (PMMA) and bis-acrylic composite based provisional crown and bridge auto-polymerizing resins exposed to tea, coffee, cola, and food dye. Two provisional crown and bridge resins, one DPI self-cure tooth molding powder (PMMA) (Group A), and one Protemp 4 Temporization Material (bis-acrylic composite) (Group B) were used. Disk-shaped specimens for color stability testing (n = 30 for each material) and bar-shaped specimens for flexural strength testing (n = 30 for each material) were fabricated using a metal mold. The specimens were immersed in artificial saliva, artificial saliva + tea, artificial saliva + coffee, artificial saliva + cola, and artificial saliva + food dye solutions and stored in an incubator at 37°C. Color measurements were taken before immersion, and then after 3 and 7 days of immersion. Flexural strength was evaluated after 7 days of immersion. Group A showed significantly higher color stability as compared to Group B, and artificial saliva + coffee solution had the most staining capacity for the resins. Test solutions had no effect on the flexural strength of Group A, but Group B specimens immersed in artificial saliva + cola showed significantly lower flexural strength values as compared to the control group. The findings of the study showed that for materials used in the study, PMMA was more color stable than bis-acrylic composite based resin. Also, material based on PMMA was more resistant to damage from dietary beverages as compared to bis-acrylic composite based provisional crown and bridge resin.

Evaluation of wetting ability of five new saliva substitutes on heat-polymerized acrylic resin for retention of complete dentures in dry mouth patients: a comparative study

PubMed Central

Mohsin, Abdul Habeeb Bin; Reddy, Varalakshmi; Kumar, Praveen; Raj, Jeevan; Babu, Siva Santosh

2017-01-01

Introduction The aim of this study was to evaluate & compare the wetting ability of five saliva substitutes & distilled water on heat-polymerized acrylic resin. Contact angle of the saliva substitute on denture base can be taken as an indicator of wettability. Good wetting of heat-polymerized acrylic resin is critical for optimum retention of complete dentures. Methods Two hundred & forty samples of heat-polymerized acrylic resin were fabricated using conventional method. 240 samples divided into 6 groups with 40 samples in each group. Advancing & Receding contact angles were measured using Contact Angle Goniometer & DSA4 software analysis. Results Anova test was carried out to test the significance in difference of contact angle values in the six groups. The mean of advancing angle values & mean of receding angle values of all the six groups has shown statistically significant difference between the groups. The mean of angle of hysteresis values of all the six groups are statistically not significant between the groups. A multiple comparison using Bonferroni’s test was carried out to verify the significance of difference between the contact angles in a pair of groups. Statistically significant difference was seen when Aqwet (Group II) was compared to Distilled water (Group I), Wet Mouth (Group III), E-Saliva (Group IV), Biotene (Group V), and Moi-Stir (Group VI). Conclusion The contact angles of five saliva substitutes and distilled water were measured and compared. Group II (AQWET) has the lowest advancing and receding contact angle values and the highest angle of hysteresis on heat-polymerized acrylic resin. Based on contact angle values, Group II (AQWET) has the best wetting ability on heat-cured acrylic resins. The ability of saliva to wet the denture surface is one of the most important properties for complete denture retention in dry mouth cases. PMID:29187918

Ultraviolet (UV)-Curable Coatings for Aerospace Applications

DTIC Science & Technology

2012-08-31

OF RESPONSIBLE PERSON Dave Madden a. REPORT U b. ABSTRACT U c . THIS PAGE U UU 259 19b. TELEPHONE NUMBER (include area code) (937) 656-5709...127 Appendix C - DSM Desotech Month by Month Progress...17 Figure 6. Black Topcoat Cured on 911th Airlift Wing C -130.......................................18 Figure 7. Black Topcoat Cured on C

Demonstration of UV LED versatility when paired with molded UV transmitting glass optics to produce unique irradiance patterns

NASA Astrophysics Data System (ADS)

Jasenak, Brian

2017-02-01

Ultraviolet light-emitting diode (UV LED) adoption is accelerating; they are being used in new applications such as UV curing, germicidal irradiation, nondestructive testing, and forensic analysis. In many of these applications, it is critically important to produce a uniform light distribution and consistent surface irradiance. Flat panes of fused quartz, silica, or glass are commonly used to cover and protect UV LED arrays. However, they don't offer the advantages of an optical lens design. An investigation was conducted to determine the effect of a secondary glass optic on the uniformity of the light distribution and irradiance. Glass optics capable of transmitting UV-A, UV-B, and UV-C wavelengths can improve light distribution, uniformity, and intensity. In this work, two simulation studies were created to illustrate distinct irradiance patterns desirable for potential real world applications. The first study investigates the use of a multi-UV LED array and optic to create a uniform irradiance pattern on the flat two dimensional (2D) target surface. The uniformity was improved by designing both the LED array and molded optic to produce a homogenous pattern. The second study investigated the use of an LED light source and molded optic to improve the light uniformity on the inside of a canister. The case study illustrates the requirements for careful selection of LED based on light distribution and subsequent design of optics. The optic utilizes total internal reflection to create optimized light distribution. The combination of the LED and molded optic showed significant improvement in uniformity on the inner surface of the canister. The simulations illustrate how the application of optics can significantly improve UV light distribution which can be critical in applications such as UV curing and sterilization.

ON THE UV CURABILITY AND MECHANICAL PROPERTIES OF NOVEL BINDER SYSTEMS DERIVED FROM POLY(ETHYLENE TEREPHTHALATE) PET WASTE FOR SOLVENTLESS MAGNETIC TAPE MANUFACTURING: ACRYLATED OLIGOESTERS. (R827121)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

ON THE UV CURABILITY AND MECHANICAL PROPERTIES OF NOVEL BINDER SYSTEMS DERIVED FROM POLY(ETHYLENE TEREPHTHALATE) PET WASTE FOR SOLVENTLESS MAGNETIC TAPE MANUFACTURING: ACRYLATED OLIGOESTERS. (R826728)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

Accelerated laboratory weathering of acrylic lens materials

NASA Astrophysics Data System (ADS)

Arndt, Thomas; Richter, Steffen; Kogler, René; Pasierb, Mike; Walby, Christopher

2014-09-01

Flat samples from various PMMA formulations subjected to accelerated laboratory weathering in an "Atlas Xenotest Alpha +" weathering device operating at 3 Sun irradiance remain transparent after 6.48GJ/m2 radiant exposure (300 - 400nm). Transmittance is reduced and yellowness index increases. However, the amount of change depends largely on the PMMA formulation. Higher UV absorber concentrations lead to smaller changes in optical properties. Based on a model of CPV efficiency for a particular power train, relative losses of efficiency are between 1 and 28%. Performance regarding these properties can be linked to the UV absorber type and concentrations used.

Argon Ion Laser Polymerized Acrylic Resin: A Comparative Analysis of Mechanical Properties of Laser Cured, Light Cured and Heat Cured Denture Base Resins

PubMed Central

Murthy, S Srinivasa; Murthy, Gargi S

2015-01-01

Background: Dentistry in general and prosthodontics in particular is evolving at greater pace, but the denture base resins poly methyl methacrylate. There has been vast development in modifying chemically and the polymerization techniques for better manipulation and enhancement of mechanical properties. One such invention was introduction of visible light cure (VLC) denture base resin. Argon ion lasers have been used extensively in dentistry, studies has shown that it can polymerize restorative composite resins. Since composite resin and VLC resin share the same photo initiator, Argon laser is tested as activator for polymerizing VLC resin. In the Phase 1 study, the VLC resin was evaluated for exposure time for optimum polymerization using argon ion laser and in Phase 2; flexural strength, impact strength, surface hardness and surface characteristics of laser cured resin was compared with light cure and conventional heat cure resin. Materials and Methods: Phase 1; In compliance with American Dental Association (ADA) specification no. 12, 80 samples were prepared with 10 each for different curing time using argon laser and evaluated for flexural strength on three point bend test. Results were compared to established performance requirement specified. Phase 2, 10 specimen for each of the mechanical properties (30 specimen) were polymerized using laser, visible light and heat and compared. Surface and fractured surface of laser, light and heat cured resins were examined under scanning electron microscope (SEM). Results: In Phase 1, the specimen cured for 7, 8, 9 and 10 min fulfilled ADA requirement. 8 min was taken as suitable curing time for laser curing. Phase 2 the values of mechanical properties were computed and subjected to statistical analysis using one-way ANOVA and Tukey post-hoc test. The means of three independent groups showed significant differences between any two groups (P < 0.001). Conclusion: Triad VLC resin can be polymerized by argon ion laser with 1 W/mm2 power and exposure time of 8 min to satisfy ADA specification. Impact strength, surface hardness of laser cure was better than light cure and heat cure resin. Flexural strength of light cure was better than laser cure and heat cure resin. The SEM study showed similar density on surface, the fractured surface of heat cure resin was dense and compact. PMID:26124596

A Twofold Comparison between Dual Cure Resin Modified Cement and Glass Ionomer Cement for Orthodontic Band Cementation

PubMed Central

Attar, Hanaa El; Elhiny, Omnia; Salem, Ghada; Abdelrahman, Ahmed; Attia, Mazen

2016-01-01

AIM: To test the solubility of dual cure resin modified resin cement in a food simulating solution and the shear bond strength compared to conventional Glass ionomer cement. MATERIALS AND METHOD: The materials tested were self-adhesive dual cure resin modified cement and Glass Ionomer (GIC). Twenty Teflon moulds were divided into two groups of tens. The first group was injected and packed with the modified resin cement, the second group was packed with GIC. To test the solubility, each mould was weighed before and after being placed in an analytical reagent for 30 days. The solubility was measured as the difference between the initial and final drying mass. To measure the Shear bond strength, 20 freshly extracted wisdom teeth were equally divided into two groups and embedded in self-cure acrylic resin. Four mm sections of stainless steel bands were cemented to the exposed buccal surfaces of teeth under a constant load of 500 g. Shear bond strength was measured using a computer controlled materials testing machine and the load required to deband the samples was recorded in Newtons. RESULTS: GIC showed significantly higher mean weight loss and an insignificant lower Shear bond strength, compared to dual cure resin Cement. CONCLUSION: It was found that dual cure resin modified cement was less soluble than glass ionomer cement and of comparable bond strength rendering it more useful clinically for orthodontic band cementation. PMID:28028417

Replication of cicada wing's nano-patterns by hot embossing and UV nanoimprinting

NASA Astrophysics Data System (ADS)

Hong, Sung-Hoon; Hwang, Jaeyeon; Lee, Heon

2009-09-01

The hydrophobicity of the cicada wing originates from its naturally occurring, surface nano-structure. The nano-structure of the cicada wing consists of an array of nano-sized pillars, 100 nm in diameter and 300 nm in height. In this study, the nano-structure of the cicada wing was successfully duplicated by using hot embossing lithography and UV nanoimprint lithography (NIL). The diameter and pitch of replication were the same as those of the original cicada wing and the height was a little smaller than that of the original master. The transmittance of the hot embossed PVC film was increased by 2-6% compared with that of the bare PVC film. The hydrophobicity was measured by water contact angle measurements. The water contact angle of the replica, made of UV cured polymer, was 132° ± 2°, which was slightly lower than that of the original cicada wing (138° ± 2°), but much higher than that of the UV cured polymer surface without any nano-sized pillars (86°).

Nucleotide Crosslinked Polybutadiene for Replacement of Isocyanate-Cured Hydroxyl-Terminated Polybutadiene (HTPB) Systems (Briefing Charts)

DTIC Science & Technology

2014-08-10

sulfur , nitrate salts, carbon (charcoal) – Unreliable ballistic properties – Could not be used in large diameter, high thrust motors • Consolidation of...a programmed manner – Molten Asphalt • Heated to a fluid melt, mixed with oxidant, cast into motor cavity and allowed to cool • Low solids content...which could be formulated • Poor mechanical properties of highly loaded asphalt – Acrylate monomers • Monomers mixed with oxidizers and curative (divinyl

Photo-Patternable ZnO Thin Films Based on Cross-Linked Zinc Acrylate for Organic/Inorganic Hybrid Complementary Inverters.

PubMed

Jeong, Yong Jin; An, Tae Kyu; Yun, Dong-Jin; Kim, Lae Ho; Park, Seonuk; Kim, Yebyeol; Nam, Sooji; Lee, Keun Hyung; Kim, Se Hyun; Jang, Jaeyoung; Park, Chan Eon

2016-03-02

Complementary inverters consisting of p-type organic and n-type metal oxide semiconductors have received considerable attention as key elements for realizing low-cost and large-area future electronics. Solution-processed ZnO thin-film transistors (TFTs) have great potential for use in hybrid complementary inverters as n-type load transistors because of the low cost of their fabrication process and natural abundance of active materials. The integration of a single ZnO TFT into an inverter requires the development of a simple patterning method as an alternative to conventional time-consuming and complicated photolithography techniques. In this study, we used a photocurable polymer precursor, zinc acrylate (or zinc diacrylate, ZDA), to conveniently fabricate photopatternable ZnO thin films for use as the active layers of n-type ZnO TFTs. UV-irradiated ZDA thin films became insoluble in developing solvent as the acrylate moiety photo-cross-linked; therefore, we were able to successfully photopattern solution-processed ZDA thin films using UV light. We studied the effects of addition of a tiny amount of indium dopant on the transistor characteristics of the photopatterned ZnO thin films and demonstrated low-voltage operation of the ZnO TFTs within ±3 V by utilizing Al2O3/TiO2 laminate thin films or ion-gels as gate dielectrics. By combining the ZnO TFTs with p-type pentacene TFTs, we successfully fabricated organic/inorganic hybrid complementary inverters using solution-processed and photopatterned ZnO TFTs.

NirN Protein from Pseudomonas aeruginosa is a Novel Electron-bifurcating Dehydrogenase Catalyzing the Last Step of Heme d1 Biosynthesis*

PubMed Central

Adamczack, Julia; Hoffmann, Martin; Papke, Ulrich; Haufschildt, Kristin; Nicke, Tristan; Bröring, Martin; Sezer, Murat; Weimar, Rebecca; Kuhlmann, Uwe; Hildebrandt, Peter; Layer, Gunhild

2014-01-01

Heme d1 plays an important role in denitrification as the essential cofactor of the cytochrome cd1 nitrite reductase NirS. At present, the biosynthesis of heme d1 is only partially understood. The last step of heme d1 biosynthesis requires a so far unknown enzyme that catalyzes the introduction of a double bond into one of the propionate side chains of the tetrapyrrole yielding the corresponding acrylate side chain. In this study, we show that a Pseudomonas aeruginosa PAO1 strain lacking the NirN protein does not produce heme d1. Instead, the NirS purified from this strain contains the heme d1 precursor dihydro-heme d1 lacking the acrylic double bond, as indicated by UV-visible absorption spectroscopy and resonance Raman spectroscopy. Furthermore, the dihydro-heme d1 was extracted from purified NirS and characterized by UV-visible absorption spectroscopy and finally identified by high-resolution electrospray ionization mass spectrometry. Moreover, we show that purified NirN from P. aeruginosa binds the dihydro-heme d1 and catalyzes the introduction of the acrylic double bond in vitro. Strikingly, NirN uses an electron bifurcation mechanism for the two-electron oxidation reaction, during which one electron ends up on its heme c cofactor and the second electron reduces the substrate/product from the ferric to the ferrous state. On the basis of our results, we propose novel roles for the proteins NirN and NirF during the biosynthesis of heme d1. PMID:25204657

Alternative glues for the production of ATLAS silicon strip modules for the Phase-II upgrade of the ATLAS Inner Detector

NASA Astrophysics Data System (ADS)

Poley, L.; Bloch, I.; Edwards, S.; Friedrich, C.; Gregor, I.-M.; Jones, T.; Lacker, H.; Pyatt, S.; Rehnisch, L.; Sperlich, D.; Wilson, J.

2016-05-01

The Phase-II upgrade of the ATLAS detector for the High Luminosity Large Hadron Collider (HL-LHC) includes the replacement of the current Inner Detector with an all-silicon tracker consisting of pixel and strip detectors. The current Phase-II detector layout requires the construction of 20,000 strip detector modules consisting of sensor, circuit boards and readout chips, which are connected mechanically using adhesives. The adhesive used initially between readout chips and circuit board is a silver epoxy glue as was used in the current ATLAS SemiConductor Tracker (SCT). However, this glue has several disadvantages, which motivated the search for an alternative. This paper presents a study of six ultra-violet (UV) cure glues and a glue pad for possible use in the assembly of silicon strip detector modules for the ATLAS upgrade. Trials were carried out to determine the ease of use, thermal conduction and shear strength. Samples were thermally cycled, radiation hardness and corrosion resistance were also determined. These investigations led to the exclusion of three UV cure glues as well as the glue pad. Three UV cure glues were found to be possible better alternatives than silver loaded glue. Results from electrical tests of first prototype modules constructed using these glues are presented.

Soil burial biodegradation studies of palm oil-based UV-curable films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tajau, Rida, E-mail: rida@nuclearmalaysia.gov.my; Salleh, Mek Zah, E-mail: mekzah@nuclearmalaysia.gov.my; Salleh, Nik Ghazali Nik, E-mail: nik-ghazali@nuclearmalaysia.gov.my

The palm oil-based ultraviolet (uv)-curable films were subjected to an outdoor soil burial test to investigate the biodegradation under natural environment. The films were burial in the soil experiment plot at the Nuclear Malaysia’s Dengkil complex. The uv-curable films were synthesized from the epoxidized palm oil acrylated (EPOLA) resin and the polyurethane palm oil (POBUA) resin, respectively. Biodegradation tests are more specific to burial film in soil experiments for 12 months under natural conditions. The biodegradability of palm oil resin based uv-curable films were investigated and compared with the petrochemical resin based film. The films properties were compared with respectmore » to properties of the thermal characteristic, the crystallinity, the morphology and the weight loss which are analyzed using the thermogravimetric analysis (TGA), the differential scanning calorimetry (DSC), the scanning electron microscope (SEM), an optical microscope and the weight loss of film calculation. These findings suggested that the palm oil-based uv-curable films show quite satisfactory biodegradation levels.« less

Soil burial biodegradation studies of palm oil-based UV-curable films

NASA Astrophysics Data System (ADS)

Tajau, Rida; Salleh, Mek Zah; Salleh, Nik Ghazali Nik; Abdurahman, Mohamad Norahiman; Salih, Ashraf Mohammed; Fathy, Siti Farhana; Azman, Anis Asmi; Hamidi, Nur Amira

2016-01-01

The palm oil-based ultraviolet (uv)-curable films were subjected to an outdoor soil burial test to investigate the biodegradation under natural environment. The films were burial in the soil experiment plot at the Nuclear Malaysia's Dengkil complex. The uv-curable films were synthesized from the epoxidized palm oil acrylated (EPOLA) resin and the polyurethane palm oil (POBUA) resin, respectively. Biodegradation tests are more specific to burial film in soil experiments for 12 months under natural conditions. The biodegradability of palm oil resin based uv-curable films were investigated and compared with the petrochemical resin based film. The films properties were compared with respect to properties of the thermal characteristic, the crystallinity, the morphology and the weight loss which are analyzed using the thermogravimetric analysis (TGA), the differential scanning calorimetry (DSC), the scanning electron microscope (SEM), an optical microscope and the weight loss of film calculation. These findings suggested that the palm oil-based uv-curable films show quite satisfactory biodegradation levels.

Biofriendly bonding processes for nanoporous implantable SU-8 microcapsules for encapsulated cell therapy.

PubMed

Nemani, Krishnamurthy; Kwon, Joonbum; Trivedi, Krutarth; Hu, Walter; Lee, Jeong-Bong; Gimi, Barjor

2011-01-01

Mechanically robust, cell encapsulating microdevices fabricated using photolithographic methods can lead to more efficient immunoisolation in comparison to cell encapsulating hydrogels. There is a need to develop adhesive bonding methods which can seal such microdevices under physiologically friendly conditions. We report the bonding of SU-8 based substrates through (i) magnetic self assembly, (ii) using medical grade photocured adhesive and (iii) moisture and photochemical cured polymerization. Magnetic self-assembly, carried out in biofriendly aqueous buffers, provides weak bonding not suitable for long term applications. Moisture cured bonding of covalently modified SU-8 substrates, based on silanol condensation, resulted in weak and inconsistent bonding. Photocured bonding using a medical grade adhesive and of acrylate modified substrates provided stable bonding. Of the methods evaluated, photocured adhesion provided the strongest and most stable adhesion.

A Facile in Situ and UV Printing Process for Bioinspired Self-Cleaning Surfaces

PubMed Central

González Lazo, Marina A.; Katrantzis, Ioannis; Dalle Vacche, Sara; Karasu, Feyza; Leterrier, Yves

2016-01-01

A facile in situ and UV printing process was demonstrated to create self-cleaning synthetic replica of natural petals and leaves. The process relied on the spontaneous migration of a fluorinated acrylate surfactant (PFUA) within a low-shrinkage acrylated hyperbranched polymer (HBP) and its chemical immobilization at the polymer-air interface. Dilute concentrations of 1 wt. % PFUA saturated the polymer-air interface within 30 min, leading to a ten-fold increase of fluorine concentration at the surface compared with the initial bulk concentration and a water contact angle (WCA) of 108°. A 200 ms flash of UV light was used to chemically crosslink the PFUA at the HBP surface prior to UV printing with a polydimethylsiloxane (PDMS) negative template of red and yellow rose petals and lotus leaves. This flash immobilization hindered the reverse migration of PFUA within the bulk HBP upon contacting the PDMS template, and enabled to produce texturized surfaces with WCA well above 108°. The synthetic red rose petal was hydrophobic (WCA of 125°) and exhibited the adhesive petal effect. It was not superhydrophobic due to insufficient concentration of fluorine at its surface, a result of the very large increase of the surface of the printed texture. The synthetic yellow rose petal was quasi-superhydrophobic (WCA of 143°, roll-off angle of 10°) and its self-cleaning ability was not good also due to lack of fluorine. The synthetic lotus leaf did not accurately replicate the intricate nanotubular crystal structures of the plant. In spite of this, the fluorine concentration at the surface was high enough and the leaf was superhydrophobic (WCA of 151°, roll-off angle below 5°) and also featured self-cleaning properties. PMID:28773860

[Light protection for xeroderma pigmentosum].

PubMed

Ettinger, M; Berneburg, M

2017-05-01

Xeroderma pigmentosum is a rare autosomal recessive disorder which is caused by germinal mutations responsible for the repair of ultraviolet (UV) radiation-induced DNA lesions. It is characterized by hypersensitivity to UV radiation, poikiloderma, ocular surface disease, and in some patients pronounced sunburn and neurological disease. Patients have a very high risk of developing ocular and skin cancer on exposed body sites. No cure is available for these patients except complete protection from all types of UV radiation.

The Effects of Ultraviolet Radiation on Attached Wetland Algae and Bacteria

NASA Astrophysics Data System (ADS)

Thomas, V. K.; Kuehn, K. A.; Francoeur, S. N.

2005-05-01

Despite the well-known increases in ultraviolet radiation (UV-R) reaching the Earth's surface due to the destruction of the ozone layer, little is known about effects of UV-R on wetland periphyton. To study the effects of UV-R on wetland periphyton, artificial substrata were placed under acrylic mesocosms in the Paint Creek Wetland, Ypsilanti, MI. One treatment mesocosm excluded light in the UV range (<340nm) and the other allowed the passage of full light. Periphyton attached to artificial substrata was collected on 4 dates during August and September 2004 and analyzed for Chlorophyll a, ash-free dry mass (AFDM), bacterial density, colloidal extracellular polysaccharides (EPS) and algal community composition. Over the length of the experiment the proportion of dead to live bacteria (p<0.02), EPS accrual (μgram glucose equivalents/cm2) (p=0.046), and the ratio of EPS to AFDM (p=0.027) were significantly greater in the UV-R-exposed treatment. These results suggest that ambient levels of UV-R damage periphytic bacteria and increase EPS production by periphyton.

Composition and method for encapsulating photovoltaic devices

DOEpatents

Pern, Fu-Jann

2000-01-01

A composition and method for encapsulating a photovoltaic device which minimizes discoloration of the encapsulant. The composition includes an ethylene-vinyl acetate encapsulant, a curing agent, an optional ultraviolet light stabilizer, and/or an optional antioxidant. The curing agent is preferably 1,1-di-(t-butylperoxy)-3,3,5-trimethylcyclohexane; the ultraviolet light stabilizer is bis-(N-octyloxy-tetramethyl) piperidinyl sebacate and the antioxidant is selected from the group consisting of tris (2,4-di-tert-butylphenyl) phosphite, tetrakis methylene (3,5-di-tert-butyl-4-hydroxyhydrocinnamate) methane, octadecyl 3,5-di-tert-butyl-4-hydroxyhydrocinnamate, and 2,2'-ethylidene bis(4,6-di-t-butylphenyl) fluorophosponite. The composition is applied to a solar cell then cured. The cured product contains a minimal concentration of curing-generated chromophores and resists UV-induced degradation.

Synthesis of TiO{sub 2} nanoparticles by self-assembling reverse micelle cores of PS-b-PAA for functional textile applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Akpolat, Leyla Budama; Çakır, Burçin Acar; Topel, Önder, E-mail: ondertopel@akdeniz.edu.tr

2015-04-15

Highlights: • TiO{sub 2} nanoparticles were synthesized within poly(styrene)-b-poly(acrylic acid) micelles. • The copolymer solution including nano TiO{sub 2} was coated onto textile fabrics. • UV-protective factor of nano TiO{sub 2} coated fabrics was estimated as 50+. • Nano TiO{sub 2} coated fabrics was found to exhibit a high photocatalytic activity. - Abstract: Titanium dioxide (i.e., titanium(IV) oxide, TiO{sub 2}) nanoparticles have been fabricated using a copolymer templating technique in micellar solution of poly(styrene)-block-poly(acrylic acid), PS(10912)-b-PAA(4842) synthesized by atom transfer radical polymerization (ATRP). The size and morphology of the synthesized TiO{sub 2} nanoparticles have been characterized via TEM and XRDmore » measurements. The average size of TiO{sub 2} nanoparticles was determined as 13 ± 3 and 13 ± 4 nm for titanium:copolymer ratios of 20:1 and 33:1, respectively. The copolymer solution including nano TiO{sub 2} particles has been coated onto textile fabrics to enhance their UV-blocking and self-cleaning properties. It has been determined that nano TiO{sub 2} coated textile fabrics have very good UV-blocking properties with 50+ of the ultraviolet protecting factor (UPF) and high photocatalytic efficiency with 69.2% of the photodegradation of methylene blue.« less

Surface modification of commercial seawater reverse osmosis membranes by grafting of hydrophilic monomer blended with carboxylated multiwalled carbon nanotubes

NASA Astrophysics Data System (ADS)

Vatanpour, Vahid; Zoqi, Naser

2017-02-01

In this study, modification of commercial seawater reverse osmosis membranes was carried out with simultaneous use of surface grafting and nanoparticle incorporation. Membrane grafting with a hydrophilic acrylic acid monomer and thermal initiator was used to increase membrane surface hydrophilicity. The used nanomaterial was carboxylated multiwalled carbon nanotubes (MWCNTs), which were dispersed in the grafting solution and deposited on membrane surface to reduce fouling by creating polymer brushes and hydrodynamic resistance. Effectiveness of the grafting process (formation of graft layer on membrane surface) was proved by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analyses. Increase of membrane surface hydrophilicity was approved with contact angle test. First, the grafting was performed on the membrane surfaces with different monomer concentrations, various contact times and several membrane curing times (three variables for optimization). The modified membranes were tested by a cross-flow setup using saline solution for permeability and rejection tests, and bovine serum albumin (BSA) solution for fouling test. The results showed that the modified membranes with 0.75 M of monomer, 3 min contact time and 80 min curing time in an oven at 50 °C presented the highest flux and lowest rejection decline related to the commercial reverse osmosis membrane. In the next step, the optimum grafting condition was selected and the nanotubes with different weight percentages were dispersed in the acrylic acid monomer solution. The membrane containing 0.25 wt% COOH-MWCNTs showed the highest fouling resistance.

Evaluation of Flexural Strength of Polymethyl Methacrylate modified with Silver Colloidal Nanoparticles subjected to Two Different Curing Cycles: An in vitro Study.

PubMed

Munikamaiah, Ranganath L; Jain, Saket K; Pal, Kapil S; Gaikwad, Ajay

2018-03-01

Silver colloidal nanoparticles have been incorporated into acrylic resins to induce antimicrobial properties. However, as additives, they can influence the mechanical properties of the final product. Mechanical properties are also dependent on different curing cycles. The aim of this study was to evaluate flexural strength of a denture base resin incorporated with different concentrations of silver colloidal nanoparticles subjected to two different curing cycles. Lucitone 199 denture base resin was used into which silver colloidal nanoparticles were incorporated at 0.5 and 5% by polymer mass. Specimens devoid of nanoparticles were used as controls. A total of 60 specimens were fabricated and divided into two groups. Each group was divided into three subgroups consisting of 10 specimens each. The specimens were fabricated according to American Dental Association (ADA) specification No. 12 and tested for flexural strength using universal testing machine. Silver colloidal nanoparticle incorporation at 0.5% concentration increased the mean flexural strength in both curing cycles by 7.5 and 4.4%, respectively, when compared with the control group. The study suggested that the mean flexural strength value of 0.5% silver colloidal nanoparticles in denture base resin was above the value of the control group both in short and long curing cycles, which makes it clinically suitable as a denture base material. However, at 5% concentration, the statistically significant amount of decrease in flexural strength compared with the value of control group both in short and long curing cycles gives it a questionable prognosis. The specimens incorporated with the antimicrobial agent 0.5% silver colloidal nanoparticles and processed by long curing cycles showed significant increase in its flexural strength compared with the control group, which makes it clinically suitable as a denture base material.

Preparation of Fe 3O 4/poly(styrene-butyl acrylate-[2-(methacryloxy)ethyl]trimethylammonium chloride) by emulsifier-free emulsion polymerization and its interaction with DNA

NASA Astrophysics Data System (ADS)

Li, Xiaolong; Liu, Guoqiang; Yan, Wei; Chu, Paul K.; Yeung, Kelvin W. K.; Wu, Shuilin; Yi, Changfeng; Xu, Zushun

2012-04-01

Cationic magnetic polymer particles Fe3O4/poly(styrene-butyl acrylate-[2-(methacryloxy)ethyl]trimethylammonium chloride), a type of potential gene carrier, were prepared by emulsifier-free emulsion polymerization with oleic acid modified magnetite Fe3O4, styrene, butyl acrylate and [2-(methacryloxy)ethyl]trimethylammonium chloride) (METAC). The morphology of the particles was characterized by transmission electron microscopy and the composites of particles were characterized by FT-IR spectroscopy, X-ray diffraction. These results showed that magnetic particles were well dispersed in polymers with the content of about 15%(wt/wt). The composites exhibited superparamagnetism and possessed a certain level of magnetic response. The interactions between the particles with calf-thymus DNA (ct DNA) were confirmed by zeta potential measurement, UV-vis spectroscopy and fluorescence spectroscopy. The DNA-binding capacity determined by the agarose gel electrophoresis showed good binding capacity of the emulsion to DNA. These results suggested the potential of the cationic magnetic polymer emulsion as gene target delivery carrier.

Organic compounds containing methoxy and cyanoacrylic acid: Synthesis, characterization, crystal structures, and theoretical studies

NASA Astrophysics Data System (ADS)

Khalaji, A. D.; Maddahi, E.; Dusek, M.; Fejfarova, K.; Chow, T. J.

2015-12-01

Metal-free organic compounds 24-SC (( E)-2-cyano-3-(2,4-dimethoxyphenyl)acrylic acid) and 34-SC (( E)-2-cyano-3-(3,4-dimethoxyphenyl)acrylic acid), containing methoxy groups as a donor and the acrylic acid as an acceptor were synthesized and characterized by CHN, FT-IR, UV-Vis, 1H-NMR and single crystal X-ray diffraction and used as photosensitizers for the application of dye-sensitized solar cells (DSSC). The sensitizing characteristics of them were evaluated. Both compounds contain the natural molecule, its anionic form and the piperidinium cation and they differ by number of these molecules in the asymmetric unit. To get further insight into the effect of molecular structure on the performance of DSSC, their geometry and energies of HOMO and LUMO were optimized by density functional theory calculation at the B3LYP/6-31G(d) level with Gaussian 03. Overall conversion efficiencies of 0.78 under full sunlight irradiation are obtained for DSSCs based on the new metal-free organic dyes 24-SC and 34-SC.

Improved photostability of NREL-developed EVA pottant formulations for PV module encapsulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pern, F.J.; Glick, S.H.

1997-12-31

Several new formulations of ethylene vinyl acetate (EVA)-based encapsulant have been developed at NREL and have greatly improved photostability against UV-induced discoloration. The new EVA formulations use stabilizers and a curing agent entirely different from any of those used in existing formulations known to the authors. No discoloration was observed for the laminated and cured samples that were exposed to a {approximately}5-sun UV light (300--400 nm) from a solar simulator at a black panel temperature (BPT) of 44 {+-} 2 C for {approximately}3250 h followed by at 85 C for {approximately}850 h, an equivalent of approximately 9.4 years for anmore » average 6-h daily, 1-sun solar exposure in Golden, Colorado. Under the same conditions, substantial discoloration and premature delamination were observed for two commercial EVA formulations. Encapsulation with the new EVA formulations should extend the long-term stability for PV modules in the field, especially when coupled with UV-filtering, Ce-containing glass superstrates.« less

SYNTHESIS AND IN VITRO CHARACTERIZATION OF HYDROXYPROPYL METHYLCELLULOSE-GRAFT-POLY (ACRYLIC ACID/2-ACRYLAMIDO-2-METHYL-1-PROPANESULFONIC ACID) POLYMERIC NETWORK FOR CONTROLLED RELEASE OF CAPTOPRIL.

PubMed

Furqan Muhammad, Iqbal; Mahmood, Ahmad; Aysha, Rashid

2016-01-01

A super-absorbent hydrogel was developed by crosslinking of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and acrylic acid with hydroxypropyl methylcellulose (HPMC) for controlled release drug delivery of captopril, a well known antihypertensive drug. Acrylic acid and AMPS were polymerized and crosslinked with HPMC by free radical polymerization, a widely used chemical crosslinking method. N,N'-methylenebisacrylamide (MBA) and potassium persulfate (KPS) were added as cross-linker and initiator, respectively. The hydrogel formulation was loaded with captopril (as model drug). The concentration of captopril was monitored at 205 nm using UV spectrophotometer. Equilibrium swelling ratio was determined at pH 2, 4.5 and 7.4 to evaluate the pH responsiveness of the formed hydrogel. The super-absorbent hydrogels were evaluated by FTIR, SEM, XRD, and thermal analysis (DSC and TGA). The formation of new copolymeric network was determined by FTIR, XRD, TGA and DSC analysis. The hydrogel formulations with acrylic acid and AMPS ratio of 4: 1 and lower amounts of crosslinker had shown maximum swelling. Moreover, higher release rate of captopril was observed at pH 7.4 than at pH 2, because of more swelling capacity of copolymer with increasing pH of the aqueous medium. The present research work confirms the development of a stable hydrogel comprising of HPMC with acrylic acid and AMPS. The prepared hydrogels exhibited pH sensitive behav-ior. This superabsorbent composite prepared could be a successful drug carrier for treating hypertension.

Microfluidic conceived Trojan microcarriers for oral delivery of nanoparticles.

PubMed

Khan, Ikram Ullah; Serra, Christophe A; Anton, Nicolas; Er-Rafik, Mériem; Blanck, C; Schmutz, Marc; Kraus, Isabelle; Messaddeq, Nadia; Sutter, Christophe; Anton, Halina; Klymchenko, Andrey S; Vandamme, Thierry F

2015-09-30

In this study, we report on a novel method for the synthesis of poly(acrylamide) Trojan microparticles containing ketoprofen loaded poly(ethyl acrylate) or poly(methyl acrylate) nanoparticles. To develop these composite particles, a polymerizable nanoemulsion was used as a template. This nanoemulsion was obtained in an elongational-flow micromixer (μRMX) which was linked to a capillary-based microfluidic device for its emulsification into micron range droplets. Downstream, the microdroplets were hardened into Trojan particles in the size range of 213-308 μm by UV initiated free radical polymerization. The nanoemulsion size varied from 98 -132 nm upon changes in surfactant concentration and number of operating cycles in μRMX. SEM and confocal microscopy confirmed the Trojan morphology. Under SEM it was observed that the polymerization reduced the size of the nanoemulsion down to 20-32 nm for poly(ethyl acrylate) and 10-15 nm for poly(methyl acrylate) nanoparticles. This shrinkage was confirmed by cryo-TEM studies. We further showed that Trojan microparticles released embedded nanoparticles on contact with suitable media as confirmed by transmission electron microscopy. In a USP phosphate buffer solution of pH 6.8, Trojan microparticles containing poly(ethyl acrylate) nanoparticles released 35% of encapsulated ketoprofen over 24h. The low release of the drug was attributed to the overall low concentration of nanoparticles and attachment of some of nanoparticles to the poly(acrylamide) matrix. Thus, this novel method has shown possibility to develop Trojan particles convieniently with potential to deliver nanoparticles in the gastrointestinal tract. Copyright © 2015 Elsevier B.V. All rights reserved.

Photochemical stability of UV-screening transparent acrylic copolymers of 2-(2-hydroxy-5-vinylphenyl)-2H-benzotriazole

NASA Technical Reports Server (NTRS)

Gupta, A.; Scott, G. W.; Kliger, D.; Vogl, O.

1983-01-01

The mechanism of photodegradation of certain hydroxyphenyl benzotriazole based ultraviolet absorbers has been investigated and a new polymerizable ultraviolet absorber in this group has been synthesized. The photoreactivity is entirely confined at the surface of polymethylmethacrylate films containing the ultraviolet absorbers as pendant groups. A mechanism involving sensitized photooxidation has been proposed to interpret the data.

Curing dynamics of photopolymers measured by single-shot heterodyne transient grating method.

PubMed

Arai, Mika; Fujii, Tomomi; Inoue, Hayato; Kuwahara, Shota; Katayama, Kenji

2013-01-01

The heterodyne transient grating (HD-TG) method was first applied to the curing dynamics measurement of photopolymers. The curing dynamics for various monomers including an initiator (2.5 vol%) was monitored optically via the refractive index change after a single UV pulse irradiation. We could obtain the polymerization time and the final change in the refractive index, and the parameters were correlated with the viscosity, molecular structure, and reaction sites. As the polymerization time was longer, the final refractive change was larger, and the polymerization time was explained in terms of the monomer properties.

Effect of gamma radiation on the stability of UV replicated composite mirrors

NASA Astrophysics Data System (ADS)

Zaldivar, Rafael J.; Kim, Hyun I.; Ferrelli, Geena L.

2018-04-01

Composite replicated mirrors are gaining increasing attention for space-based applications due to their lower density, tailorable mechanical properties, and rapid manufacturing times over state-of-the-art glass mirrors. Ultraviolet (UV)-cured mirrors provide a route by which high-quality mirrors can be manufactured at relatively low processing temperatures that minimize residual stresses. The successful utilization of these mirrors requires nanometer scale dimensional stability after both thermal cycling and hygrothermal exposure. We investigate the effect of gamma irradiation as a process to improve the stability of UV replicated mirrors. Gamma radiation exposure was shown to increase the cure state of these mirrors as evidenced by an increase in modulus, glass transition temperature, and the thermal degradation behavior with dosage. Gas chromatography-mass spectroscopy also showed evidence of consumption of the primary monomers and initiation of the photosensitive agent with gamma exposure. The gamma-exposed mirrors exhibited significant improvement in stability even after multiple thermal cycling in comparison with nonirradiated composite mirrors. Though improvements in the cure state contribute to the overall stability, the radiation dosage was also shown to reduce the film stress of the mirror by over 80% as evidenced using Stoney replicated specimens. This reduction in residual stress is encouraging considering the utilization of these structures for space applications. This paper shows that replicated composite mirrors are a viable alternative to conventional optical structures.

Free Volume Structure of Acrylic-Type Dental Nanocomposites Tested with Annihilating Positrons.

PubMed

Shpotyuk, Olha; Ingram, Adam; Shpotyuk, Oleh

2016-12-01

Positron annihilation spectroscopy in lifetime measuring mode exploring conventional fast-fast coincidence ORTEC system is employed to characterize free volume structure of commercially available acrylic-type dental restorative composite Charisma® (Heraeus Kulzer GmbH, Germany). The measured lifetime spectra for uncured and light-cured composites are reconstructed from unconstrained x3-term fitting and semi-empirical model exploring x3-x2-coupling decomposition algorithm. The governing channel of positron annihilation in the composites studied is ascribed to mixed positron-Ps trapping, where Ps decaying in the third component is caused entirely by input from free-volume holes in polymer matrix, while the second component is defined by free positron trapping in interfacial free-volume holes between filler nanoparticles and surrounded polymer matrix. Microstructure scenario of the photopolymerization shrinkage includes cross-linking of structural chains in polymer matrix followed by conversion of bound positron-electron (positronium) traps in positron-trapping interfacial free-volume voids in a vicinity of agglomerated filler nanoparticles.

Impregnation with antimicrobials has an impact on degree of conversion and colour stability of acrylic liner.

PubMed

Salim, Nesreen; Satterthwaite, Julian; Rautemaa, Riina; Silikas, Nick

2012-01-01

This study investigated the impact of impregnation of a poly(ethyl methacrylate) /tetrahydrofurfuryl methacrylate (PEM/THFM) polymer with chlorhexidine or fluconazole on the degree of conversion (DC) and colour stability (ΔE). The DC of uncured (0 h) and cured (24 h) samples was analysed by Fourier transform infrared spectroscopy (FTIR) and colour stability was analysed colorimetrically. The DC percentage of the control samples was significantly greater than those containing chlorhexidine and fluconazole (p≤0.05). The control discs exhibited only slight colour change compared to the impregnated discs which showed marked colour change (p≤0.05). A strong negative correlation between the extent of colour change and the degree of conversion was detected (r=0.97). The DC and colour stability were influenced by the addition of chlorhexidine or fluconazole. However, the final values were comparable to other commonly used acrylic liners and within acceptable ranges. PEM/THFM can be considered as a biocompatible drug delivery system.

Digital One-Disc-One-Compound Method for High-Throughput Discovery of Prostate Cancer - Targeting Ligands

DTIC Science & Technology

2015-10-01

shown in Fig. 1a, the prepolymer mixture was sandwiched between photo mask and glass slide. Microdiscs were fabricated on the glass substrate through...polymerization of the prepolymer mixture and the acrylated silane under UV exposure. To achieve the more stable microdiscs for peptide synthesis, the...composition of prepolymer mixture was changed to PEG (Polyethylene Glycol)-diacrylate, crosslinker, photo initiator, 2-aminoethylmethacrylate, water

Graft polymerization of acrylic acid onto chitin nanofiber to improve dispersibility in basic water.

PubMed

Ifuku, Shinsuke; Iwasaki, Masayoshi; Morimoto, Minoru; Saimoto, Hiroyuki

2012-09-01

Graft copolymerization of acrylic acid (AA) on chitin nanofibers was carried out with potassium persulfate as a free radical initiator in an aqueous medium. The molar ratio of grafted AA increased with the AA concentration. The grafted chitin nanofibers were characterized by FT-IR, FE-SEM, UV-vis, XRD, and TGA. After polymerization, the characteristic morphology of chitin nanofibers was maintained. Chitin nanofibers grafted with AA were efficiently dissociated and dispersed homogeneously in basic water because of the electrostatic repulsion effect between nanofibers. AA was grafted on the surface and amorphous part of chitin nanofibers, and the original crystalline structure of α-chitin was maintained. At 330 °C, the weight residue of the graft copolymer increased with the grafted AA content. Copyright © 2012 Elsevier Ltd. All rights reserved.

Synthesis and characterization of zinc chloride containing poly(acrylic acid) hydrogel by gamma irradiation

NASA Astrophysics Data System (ADS)

Park, Jong-Seok; Kuang, Jia; Gwon, Hui-Jeong; Lim, Youn-Mook; Jeong, Sung-In; Shin, Young-Min; Seob Khil, Myung; Nho, Young-Chang

2013-07-01

In this study, the characterization of zinc chloride incorporated into a poly(acrylic acid) (PAAc) hydrogel prepared by gamma-ray irradiation was investigated. Zinc chloride powder with different concentrations was dissolved in the PAAc solution, and it was crosslinked with gamma-ray irradiation. The effects of various parameters such as zinc ion concentration and irradiation doses on characteristics of the hydrogel formed were investigated in detail for obtaining an antibacterial wound dressing. In addition, the gel content, pH-sensitive (pH 4 or 7) swelling ratio, and UV-vis absorption spectra of the zinc particles in the hydrogels were characterized. Moreover, antibacterial properties of these new materials against Staphylococcus aureus and Escherichia coli strains were observed on solid growth media. The antibacterial tests indicated that the zinc chloride containing PAAc hydrogels have good antibacterial activity.

Optically transparent super-hydrophobic thin film fabricated by reusable polyurethane-acrylate (PUA) mold

NASA Astrophysics Data System (ADS)

Park, J.-S.; Park, J.-H.; Lee, D.-W.

2018-02-01

In this paper, we describe a simple manufacturing method for producing an optically transparent super-hydrophobic polymer thin film using a reusable photo-curable polymer mold. Soluble photoresist (PR) molds were prepared with under-exposed and under-baked processes, which created unique hierarchical micro/nano structures. The reverse phase of the PR mold was replicated on the surface of polydimethylsiloxane (PDMS) substrates. The unique patterns on the replicated PDMS molds were successfully transferred back to the UV curable polyurethane-acrylate (PUA) using a laboratory-made UV exposure system. Continuous production of the super-hydrophobic PDMS thin film was demonstrated using the reusable PUA mold. In addition, hydrophobic nano-silica powder was sprayed onto the micro/nano structured PDMS surfaces to further improve hydrophobicity. The fabricated PDMS thin films with hierarchical surface texturing showed a water contact angle  ⩾150°. Excellent optical transmittance within the range of visible light of wavelengths between 400-800 nm was experimentally confirmed using a spectrophotometer. High efficiency of the super-hydrophobic PDMS film in optical transparency was also confirmed using solar panels. The fabricated PUA molds are very suitable for use in roll-to-roll or roll-to-plate systems which allow continuous production of super-hydrophobic thin films with an excellent optical transparency.

Relevance of nanocomposite packaging on the stability of vacuum-packed dry cured ham.

PubMed

Lloret, Elsa; Fernandez, Avelina; Trbojevich, Raul; Arnau, Jacint; Picouet, Pierre A

2016-08-01

In this study effects of a novel high barrier multilayer polyamide film containing dispersed nanoclays (PAN) on the stability of vacuum packed dry-cured ham were investigated during 90days refrigerated storage in comparison with non-modified multilayer polyamide (PA) and a commercial high barrier film. Characteristic bands of the mineral in FT-IR spectra confirmed the presence of nanoclays in PAN, enhancing oxygen transmission barrier properties and UV protection. Packaging in PAN films did not originate significant changes on colour or lipid oxidation during prolonged storage of vacuum-packed dry-cured ham. Larger oxygen transmission rates in PA films caused changes in CIE b* during refrigerated storage. Ham quality was not affected by light exposition during 90days and only curing had a significant benefit on colour and TBARS, being cured samples more stable during storage in all the packages used. Packaging of dry-cured ham in PAN was equivalent to commercial high barrier films. Copyright © 2016 Elsevier Ltd. All rights reserved.

Experimental and numeric stress analysis of titanium and zirconia one-piece dental implants.

PubMed

Mobilio, Nicola; Stefanoni, Filippo; Contiero, Paolo; Mollica, Francesco; Catapano, Santo

2013-01-01

To compare the stress in bone around zirconia and titanium implants under loading. A one-piece zirconia implant and a replica of the same implant made of commercially pure titanium were embedded in two self-curing acrylic resin blocks. To measure strain, a strain gauge was applied on the surface of the two samples. Loads of 50, 100, and 150 N, with orientations of 30, 45, and 60 degrees with respect to the implant axis were applied on the implant. Strain under all loading conditions on both samples was measured. Three-dimensional virtual replicas of both the implants were reproduced using the finite element method and inserted into a virtual acrylic resin block. All the materials were considered isotropic, linear, and elastic. The same geometry and loading conditions of the experimental setup were used to realize two new models, with the implants embedded within a virtual bone block. Very close values of strain in the two implants embedded in acrylic resin were obtained both experimentally and numerically. The stress states generated by the implants embedded in virtual bone were also very similar, even if the two implants moved differently. Moreover, the stress levels were higher on cortical bone than on trabecular bone. The stress levels in bone, generated by the two implants, appeared to be very similar. From a mechanical point of view, zirconia is a feasible substitute for titanium.

Methodology for UV Cured Conformal Coating

DTIC Science & Technology

1980-06-01

were coated and cured in the Hughes 5•C facility and delivered to MIRADCO& M for their evaluation. At the conclusion of the contract, two 1-day...identification of two coating materials which were fast curing, had few processing problems, and had the potential of meeting M !L..I- 46058C requiremerts...C" 0 c . m O5 C= ~ - cm CLm 6 EU~~ rJ-CS. Ln 0 IN J W a MS C-4 !2Z. 21 Oh.2 C + 2w IN C M C L-o 4 CO IN 0 .EU c i -c a- 0 IN0 oc 30 A 0 E90 -= cc rn

Bio-based Polymer Foam from Soyoil

NASA Astrophysics Data System (ADS)

Bonnaillie, Laetitia M.; Wool, Richard P.

2006-03-01

The growing bio-based polymeric foam industry is presently lead by plant oil-based polyols for polyurethanes and starch foams. We developed a new resilient, thermosetting foam system with a bio-based content higher than 80%. The acrylated epoxidized soybean oil and its fatty acid monomers is foamed with pressurized carbon dioxide and cured with free-radical initiators. The foam structure and pore dynamics are highly dependent on the temperature, viscosity and extent of reaction. Low-temperature cure hinds the destructive pore coalescence and the application of a controlled vacuum results in foams with lower densities ˜ 0.1 g/cc, but larger cells. We analyze the physics of foam formation and stability, as well as the structure and mechanical properties of the cured foam using rigidity percolation theory. The parameters studied include temperature, vacuum applied, and cross-link density. Additives bring additional improvements: nucleating agents and surfactants help produce foams with a high concentration of small cells and low bulk density. Hard and soft thermosetting foams with a bio content superior to 80% are successfully produced and tested. Potential applications include foam-core composites for hurricane-resistant housing, structural reinforcement for windmill blades, and tissue scaffolds.

Flexural properties of ethyl or methyl methacrylate-UDMA blend polymers.

PubMed

Kanie, Takahito; Kadokawa, Akihiko; Arikawa, Hiroyuki; Fujii, Koichi; Ban, Seiji

2010-10-01

Light-curing polyethyl methacrylate (PEMA)-urethane dimethacrylate (UDMA) resins and polymethyl methacrylate (PMMA)-UDMA resins were prepared by two processes. For first step, PEMA or PMMA powders were fully dissolved in ethyl methacrylate (EMA) or methyl methacrylate (MMA) and then the PEMA-EMA/PMMA-MMA mixtures were mixed with UDMA. The flexural properties of cured PEMA-UDMA and PMMA-UDMA polymers were measured using two PEMA (Mw: 300,000-400,000 and 650,000-1,000,000) and three PMMA (Mw: 30,000-60,000, 350,000 and 650,000-1,000,000) powders with different molecular weight, four mixing ratios of PMMA-MMA, and three mixing ratios of PMMA-MMA mixture and UDMA oligomer. Polymers with PMMA(Mw: 350,000) MMA=25/50, and with PMMA(Mw: 350,000)-MMA/UDMA=1/2 and =1/1, showed no-fracture in a flexural test at 1 mm/min and flexural strength and flexural modulus showed no significant difference compared with those of commercially available heat- and self-curing acrylic resins (p>0.01). Within limitation of this investigation, methyl methacrylate-UDMA blend polymer of this composition is available for denture base resin.

Transdermal thiol-acrylate polyethylene glycol hydrogel synthesis using near infrared light

NASA Astrophysics Data System (ADS)

Chung, Solchan; Lee, Hwangjae; Kim, Hyung-Seok; Kim, Min-Gon; Lee, Luke P.; Lee, Jae Young

2016-07-01

Light-induced polymerization has been widely applied for hydrogel synthesis, which conventionally involves the use of ultraviolet or visible light to activate a photoinitiator for polymerization. However, with these light sources, transdermal gelation is not efficient and feasible due to their substantial interactions with biological systems, and thus a high power is required. In this study, we used biocompatible and tissue-penetrating near infrared (NIR) light to remotely trigger a thiol-acrylate reaction for efficient in vivo gelation with good controllability. Our gelation system includes gold nanorods as a photothermal agent, a thermal initiator, diacrylate polyethylene glycol (PEG), and thiolated PEG. Irradiation with a low-power NIR laser (0.3 W cm-2) could induce gelation via a mixed-mode reaction with a small increase in temperature (~5 °C) under the optimized conditions. We also achieved successful transdermal gelation via the NIR-assisted photothermal thiol-acryl reactions. This new type of NIR-assisted thiol-acrylate polymerization provides new opportunities for in situ hydrogel formation for injectable hydrogels and delivery of drugs/cells for various biomedical applications.Light-induced polymerization has been widely applied for hydrogel synthesis, which conventionally involves the use of ultraviolet or visible light to activate a photoinitiator for polymerization. However, with these light sources, transdermal gelation is not efficient and feasible due to their substantial interactions with biological systems, and thus a high power is required. In this study, we used biocompatible and tissue-penetrating near infrared (NIR) light to remotely trigger a thiol-acrylate reaction for efficient in vivo gelation with good controllability. Our gelation system includes gold nanorods as a photothermal agent, a thermal initiator, diacrylate polyethylene glycol (PEG), and thiolated PEG. Irradiation with a low-power NIR laser (0.3 W cm-2) could induce gelation via a mixed-mode reaction with a small increase in temperature (~5 °C) under the optimized conditions. We also achieved successful transdermal gelation via the NIR-assisted photothermal thiol-acryl reactions. This new type of NIR-assisted thiol-acrylate polymerization provides new opportunities for in situ hydrogel formation for injectable hydrogels and delivery of drugs/cells for various biomedical applications. Electronic supplementary information (ESI) available: FE-SEM image of thiol-acrylate hydrogels; UV/Vis spectra of Ellman's assay; the temperature increase during transdermal photothermal hydrogelation. See DOI: 10.1039/c6nr01956k

Custom fabrication of biomass containment devices using 3-D printing enables bacterial growth analyses with complex insoluble substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nelson, Cassandra E.; Beri, Nina R.; Gardner, Jeffrey G.

Physiological studies of recalcitrant polysaccharide degradation are challenging for several reasons, one of which is the difficulty in obtaining a reproducibly accurate real-time measurement of bacterial growth using insoluble substrates. Current methods suffer from several problems including (i) high background noise due to the insoluble material interspersed with cells, (ii) high consumable and reagent cost and (iii) significant time delay between sampling and data acquisition. A customizable substrate and cell separation device would provide an option to study bacterial growth using optical density measurements. To test this hypothesis we used 3-D printing to create biomass containment devices that allow interactionmore » between insoluble substrates and microbial cells but do not interfere with spectrophotometer measurements. Evaluation of materials available for 3-D printing indicated that UV-cured acrylic plastic was the best material, being superior to nylon or stainless steel when examined for heat tolerance, reactivity, and ability to be sterilized. Cost analysis of the 3-D printed devices indicated they are a competitive way to quantitate bacterial growth compared to viable cell counting or protein measurements, and experimental conditions were scalable over a 100-fold range. The presence of the devices did not alter growth phenotypes when using either soluble substrates or insoluble substrates. Furthermore, we applied biomass containment to characterize growth of Cellvibrio japonicus on authentic lignocellulose (non-pretreated corn stover), and found physiological evidence that xylan is a significant nutritional source despite an abundance of cellulose present.« less

Custom fabrication of biomass containment devices using 3-D printing enables bacterial growth analyses with complex insoluble substrates

DOE PAGES

Nelson, Cassandra E.; Beri, Nina R.; Gardner, Jeffrey G.

2016-09-21

Physiological studies of recalcitrant polysaccharide degradation are challenging for several reasons, one of which is the difficulty in obtaining a reproducibly accurate real-time measurement of bacterial growth using insoluble substrates. Current methods suffer from several problems including (i) high background noise due to the insoluble material interspersed with cells, (ii) high consumable and reagent cost and (iii) significant time delay between sampling and data acquisition. A customizable substrate and cell separation device would provide an option to study bacterial growth using optical density measurements. To test this hypothesis we used 3-D printing to create biomass containment devices that allow interactionmore » between insoluble substrates and microbial cells but do not interfere with spectrophotometer measurements. Evaluation of materials available for 3-D printing indicated that UV-cured acrylic plastic was the best material, being superior to nylon or stainless steel when examined for heat tolerance, reactivity, and ability to be sterilized. Cost analysis of the 3-D printed devices indicated they are a competitive way to quantitate bacterial growth compared to viable cell counting or protein measurements, and experimental conditions were scalable over a 100-fold range. The presence of the devices did not alter growth phenotypes when using either soluble substrates or insoluble substrates. Furthermore, we applied biomass containment to characterize growth of Cellvibrio japonicus on authentic lignocellulose (non-pretreated corn stover), and found physiological evidence that xylan is a significant nutritional source despite an abundance of cellulose present.« less

Low gloss UV-cured coatings for aircraft

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bowman, Mark; Muschar, Harry

A method of applying a low gloss coating to a substrate such as the exterior surface of an aircraft is disclosed. The coating composition comprising a polyene, a polythiol, a flatting agent and a coloring pigment is applied to the substrate and given a first dosage of UV radiation followed by a second dosage in which the second dosage is greater than the first resulting in an ultralow gloss coating.

Low-cost integrated-optic fiber couplers

NASA Astrophysics Data System (ADS)

Sheem, Sang K.; Zhang, Feng; Choi, Jong-Ho; Lee, Yong-Woo; Low, Sarah; Lu, Shih-Yau

1997-04-01

In an effort to lower the cost of fiber optic couplers, integrated optic channel waveguide circuits are made of a UV-curable polymer using a molding technique, and then a novel fiber-to-channel connecting approach is employed in which UV light radiating from an optical fiber core cures the polymer in the channel, thus accomplishing a 'touchdown' of the core-extension waveguide onto the walls of the channel waveguide.

A new UV-curing elastomeric substrate for rapid prototyping of microfluidic devices

NASA Astrophysics Data System (ADS)

Alvankarian, Jafar; Yeop Majlis, Burhanuddin

2012-03-01

Rapid prototyping in the design cycle of new microfluidic devices is very important for shortening time-to-market. Researchers are facing the challenge to explore new and suitable substrates with simple and efficient microfabrication techniques. In this paper, we introduce and characterize a UV-curing elastomeric polyurethane methacrylate (PUMA) for rapid prototyping of microfluidic devices. The swelling and solubility of PUMA in different chemicals is determined. Time-dependent measurements of water contact angle show that the native PUMA is hydrophilic without surface treatment. The current monitoring method is used for measurement of the electroosmotic flow mobility in the microchannels made from PUMA. The optical, physical, thermal and mechanical properties of PUMA are evaluated. The UV-lithography and molding process is used for making micropillars and deep channel microfluidic structures integrated to the supporting base layer. Spin coating is characterized for producing different layer thicknesses of PUMA resin. A device is fabricated and tested for examining the strength of different bonding techniques such as conformal, corona treating and semi-curing of two PUMA layers in microfluidic application and the results show that the bonding strengths are comparable to that of PDMS. We also report fabrication and testing of a three-layer multi inlet/outlet microfluidic device including a very effective fluidic interconnect for application demonstration of PUMA as a promising new substrate. A simple micro-device is developed and employed for observing the pressure deflection of membrane made from PUMA as a very effective elastomeric valve in microfluidic devices.

The translucency of dental composites investigated by UV-VIS spectroscopy

NASA Astrophysics Data System (ADS)

Dumitrescu, L. Silaghi; Pastrav, O.; Prejmerean, C.; Prodan, D.; Boboia, S.; Codruta, S.; Moldovan, M.

2013-11-01

Translucency is the property of a material to partially transmit and diffuse incident light, and can be described as a partial opacity or a state between complete opacity and complete transparency. The purpose of this study is to evaluate the translucency index of resin composites according to their chemical structure and to the light source used for curing. Our study was achieved on four commercial composite samples (30 mm × 2 mm) cured with two different lamps (Optilux - halogen bulb and Ultralight - LED). Measurements were made with a UV-VIS spectrophotometer, and the reflection spectrum was recorded in the 380-770 nm region on white and black, compared with a SPECTRALON standard white. For all materials cured with the LED lamp on the glossy sides, the best results were given by Tetric Evo Ceram followed by Filtek Supreme, RestacrilRO and Premise. The measurements made on samples cured with an Optilux lamp, to the smooth and rough sides of the samples, revealed that the highest index of translucency is provided by Tetric Evo Ceram on the smooth side, followed by Filtek Supreme, RestacrilRO and Premises. We can say that the translucency of the composites is mostly determined by the chemical composition of the material, which is observed from transmittance values recorded for each sample, and by the source of radiation applied on the sample.

The translucency of dental composites investigated by UV-VIS spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dumitrescu, L. Silaghi; Pastrav, O.; Prejmerean, C.

Translucency is the property of a material to partially transmit and diffuse incident light, and can be described as a partial opacity or a state between complete opacity and complete transparency. The purpose of this study is to evaluate the translucency index of resin composites according to their chemical structure and to the light source used for curing. Our study was achieved on four commercial composite samples (30 mm × 2 mm) cured with two different lamps (Optilux - halogen bulb and Ultralight - LED). Measurements were made with a UV-VIS spectrophotometer, and the reflection spectrum was recorded in themore » 380-770 nm region on white and black, compared with a SPECTRALON standard white. For all materials cured with the LED lamp on the glossy sides, the best results were given by Tetric Evo Ceram followed by Filtek Supreme, Restacril{sup RO} and Premise. The measurements made on samples cured with an Optilux lamp, to the smooth and rough sides of the samples, revealed that the highest index of translucency is provided by Tetric Evo Ceram on the smooth side, followed by Filtek Supreme, Restacril{sup RO} and Premises. We can say that the translucency of the composites is mostly determined by the chemical composition of the material, which is observed from transmittance values recorded for each sample, and by the source of radiation applied on the sample.« less

Research on the calibration of ultraviolet energy meters

NASA Astrophysics Data System (ADS)

Lin, Fangsheng; Yin, Dejin; Li, Tiecheng; Lai, Lei; Xia, Ming

2016-10-01

Ultraviolet (UV) radiation is a kind of non-lighting radiation with the wavelength range from 100nm to 400nm. Ultraviolet irradiance meters are now widely used in many areas. However, as the development of science and technology, especially in the field of light-curing industry, there are more and more UV energy meters or UV-integrators need to be measured. Because the structure, wavelength band and measured power intensity of UV energy meters are different from traditional UV irradiance meters, it is important for us to take research on the calibration. With reference to JJG879-2002, we SIMT have independently developed the UV energy calibration device and the standard of operation and experimental methods for UV energy calibration in detail. In the calibration process of UV energy meter, many influencing factors will affect the final results, including different UVA-band UV light sources, different spectral response for different brands of UV energy meters, instability and no uniformity of UV light source and temperature. Therefore we need to take all of these factors into consideration to improve accuracy in UV energy calibration.

Curing of polymer thermosets via click reactions and on demand processes

NASA Astrophysics Data System (ADS)

Brei, Mark Richard

In the first project, an azide functional resin and tetra propargyl aromatic diamines were fabricated for use as a composite matrix. These systems take already established epoxy/amine matrices and functionalize them with click moieties. This allows lower temperatures to be used in the production of a thermoset part. These new systems yield many better mechanical properties than their epoxy/amine derivatives, but their Tgs are low in comparison. The second project investigates the characterization of a linear system based off of the above azide functional resin and a difunctional alkyne. Through selectively choosing catalyst, the linear system can show regioselectivity to either a 1,4-disubstituted triazole, or a 1,5-disubstituted triazole. Without the addition of catalyst, the system produces both triazoles in almost an equal ratio. The differently catalyzed systems were cured and then analyzed by 1H and 13C NMR to better understand the structure of the material. The third project builds off of the utility of the aforementioned azide/alkyne system and introduces an on-demand aspect to the curing of the thermoset. With the inclusion of copper(II) within the azide/alkyne system, UV light is able to catalyze said reaction and cure the material. It has been shown that the copper(II) loading levels can be extremely small, which helps in reducing the copper's effect on mechanical properties The fourth project takes a look at polysulfide-based sealants. These sealants are normally cured via an oxidative reaction. This project took thiol-terminated polysulfides and fabricated alkene-terminated polysulfides for use as a thiol-ene cured material. By changing the mechanism for cure, the polysulfide can be cured via UV light with the use of a photoinitiator within the thiol/alkene polysulfide matrix. The final chapter will focus on a characterization technique, MALDI-TOF, which was used to help characterize the above materials as well as many others. By using MALDI-TOF, the researcher is able to elicit the molecular weight of the repeat unit and end group, which allows the determination of the polymer's structure. This technique can also determine the Mn and M w, as well as the PDI for each given polymer.

Ultrafast third-order nonlinear optical response of pyrene derivatives

NASA Astrophysics Data System (ADS)

Shi, Yufang; Li, Zhongguo; Fang, Yu; Sun, Jinyu; Zhao, Minggen; Song, Yinglin

2017-05-01

Two mono-substituted pyrene derivatives with delocalized electron system 1-(pyren-1-yl)-3-(4-Methyl thiophene-2-yl) acrylic ketone (13#) and 1-(pyren-1-yl)-3-(4-bromo thiophene-2-yl) acrylic ketone (15#) were successfully synthesized. The resultant compounds were characterized by nuclear magnetic resonance (NMR), infrared spectroscopy (IR), high resolution mass spectrum (HR-MS), and UV-vis spectra. The third-order nonlinear optical properties of the compounds were investigated using Z-scan technique with femtosecond laser pulses at 500 nm and 700 nm, respectively. Both of the compounds showed a decrease in transmittance about the focus, which are typical of two-photon absorption. It was found that the two-photon absorption behavior of the pyrene derivatives were modified by substituents on thiophene ring. These results indicate that both compounds can be promising candidates for future optoelectronic and bio-imaging applications.

UV Grafting Modification of Polyethylene Separator for Liion Battery

NASA Astrophysics Data System (ADS)

Lv, Xiaoyuan; Li, Hua; Zhang, Zhiqiang; Chang, Hiunam; Jiang, Li; Liu, Hezhou

Polyethylene (PE) separator was modified by UV grafting methyl acrylate (MA) and nano-SiO2 composite layer. The structure of functional group and morphology of the separator were analyzed by Fourier transform infrared spectrum (FT-IR) and scanning electron microscope (SEM). The wetting behavior and the heat resistance of the separator were also investigated by contact angle test and thermal shrinkage test respectively. The results show that MA/nano-SiO2 composite layer is successfully grafted onto the PE separator, and the addition of the DI water and butanol can make the nano-SiO2 dispersed better and lead to a microporous structure of the grafting layer. The grafted separator has a better wettability and heat resistance than the pristine one.

Spectral properties of common intraocular lens (IOL) types

NASA Astrophysics Data System (ADS)

Milne, Peter J.; Chapon, Pascal F.; Hamaoui, Marie; Parel, Jean-Marie A.; Clayman, H.; Rol, Pascal O.

1999-06-01

Currently over 50 kinds of intraocular lenses (IOLs) are approved for patient use in the treatment of cataracts and ametropia. These lenses are manufactured from at least 2 kinds of silicones as well as several kinds of acrylic polymers including polyHEMA, Poly HOXEMA, a range of polymethacrylate and polyacrylate formulations. We sought to measure spectral transmission curves of a range of IOLS in the UV-visible and near IR spectral regions in order to better characterize their optical properties and to provide a baseline from which to assess their alteration following implantation over time. Consideration of how this may best be achieved are discussed. The variable ability of both explained IOLs and some samples from a range of manufacturers to block UV wavelengths is commented upon.

Selection of UV Resins for Nanostructured Molds for Thermal-NIL.

PubMed

Jia, Zheng; Choi, Junseo; Park, Sunggook

2018-06-18

Nanoimprint molds made of soft polymeric materials have advantages of low demolding force and low fabrication cost over Si or metal-based hard molds. However, such advantages are often sacrificed by their reduced replication fidelity associated with the low mechanical strength. In this paper, we studied replication fidelity of different UV-resin molds copied from a Si master mold via UV nanoimprint lithography (NIL) and their thermal imprinting performance into a thermoplastic polymer. Four different UV resins were studied: two were high surface energy UV resins based on tripropyleneglycol diacrylate (TPGDA resin) and polypropyleneglycol diacrylate (PPGDA resin), and the other two were commercially available, low surface energy poly-urethane acrylate (PUA resin) and fluorine-containing (MD 700) UV resins. The replication fidelity among the four UV-resins during UV nanoimprint lithograph from a Si master with sharp nanostructures was in the increasing order of (poorest) PUA resin < MD 700 < PPGDA resin < TPGDA resin (best). The results show that the high surface energy and small monomer size are keys to achieving good UV resin filling into sharp nanostructures over the viscosity of the resin solution. When the four UV-resin molds were used for thermal-NIL into a thermoplastic polymer, the replication fidelity was in the increasing order of (poorest) MD 700 < TPGDA resin < PUA resin (best), which follows the same order of their Young's moduli. Our results indicate that the selection of an appropriate UV resin for NIL molds requires consideration of the replication fidelities in the mold fabrication and the subsequent thermal-NIL into thermoplastic polymers. © 2018 IOP Publishing Ltd.

FT-IR, UV-vis, 1H and 13C NMR spectra and the equilibrium structure of organic dye molecule disperse red 1 acrylate: a combined experimental and theoretical analysis.

PubMed

Cinar, Mehmet; Coruh, Ali; Karabacak, Mehmet

2011-12-01

This study reports the characterization of disperse red 1 acrylate compound by spectral techniques and quantum chemical calculations. The spectroscopic properties were analyzed by FT-IR, UV-vis, (1)H NMR and (13)C NMR techniques. FT-IR spectrum in solid state was recorded in the region 4000-400 cm(-1). The UV-vis absorption spectrum of the compound that dissolved in methanol was recorded in the range of 200-800 nm. The (1)H and (13)C NMR spectra were recorded in CDCl(3) solution. The structural and spectroscopic data of the molecule in the ground state were calculated using density functional theory (DFT) employing B3LYP exchange correlation and the 6-311++G(d,p) basis set. The vibrational wavenumbers were calculated and scaled values were compared with experimental FT-IR spectrum. A satisfactory consistency between the experimental and theoretical spectra was obtained and it shows that the hybrid DFT method is very useful in predicting accurate vibrational structure, especially for high-frequency region. The complete assignments were performed on the basis of the experimental results and total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. Isotropic chemical shifts were calculated using the gauge-invariant atomic orbital (GIAO) method. A study on the electronic properties were performed by timedependent DFT (TD-DFT) and CIS(D) approach. To investigate non linear optical properties, the electric dipole moment μ, polarizability α, anisotropy of polarizability Δα and molecular first hyperpolarizability β were computed. The linear polarizabilities and first hyperpolarizabilities of the studied molecule indicate that the compound can be a good candidate of nonlinear optical materials. Copyright © 2011 Elsevier B.V. All rights reserved.

Vacuum-deposited polymer/silver reflector material

NASA Astrophysics Data System (ADS)

Affinito, John D.; Martin, Peter M.; Gross, Mark E.; Bennett, Wendy D.

1994-09-01

Weatherable, low cost, front surface, solar reflectors on flexible substrates would be highly desirable for lamination to solar concentrator panels. The method to be described in this paper may permit such reflector material to be fabricated for less the 50$CNT per square foot. Vacuum deposited Polymer/Silver/Polymer reflectors and Fabry-Perot interference filters were fabricated in a vacuum web coating operation on polyester substrates. Reflectivities were measured in the wavelength range from .4 micrometers to .8 micrometers . It is hoped that a low cost substrate can be used with the substrate laminated to the concentrator and the weatherable acrylic polymer coating facing the sun. This technique should be capable of deposition line speeds approaching 1500 linear feet/minute2. Central to this technique is a new vacuum deposition process for the high rate deposition of polymer films. This polymer process involves the flash evaporation of an acrylic monomer onto a moving substrate. The monomer is subsequently cured by an electron beam or ultraviolet light. This high speed polymer film deposition process has been named the PML process- for Polymer Multi- Layer.

Calcium-selective electrodes based on photo-cured polyurethane-acrylate membranes covalently attached to methacrylate functionalized poly(3,4-ethylenedioxythiophene) as solid-contact.

PubMed

Ocaña, Cristina; Abramova, Natalia; Bratov, Andrey; Lindfors, Tom; Bobacka, Johan

2018-08-15

We report here the fabrication of solid-contact calcium-selective electrodes (Ca 2+ -SCISEs) made of a polyurethane acrylate ion-selective membrane (ISM) that was covalently attached to the underlying ion-to-electron transducer (solid-contact). Methacrylate-functionalized poly(3,4-ethylenedioxythiophene) (Meth-PEDOT) and Meth-PEDOT films containing either multiwalled carbon nanotubes (MWCNT) or carboxylated MWCNT (cMWCNT) were used as solid contacts. The solid contacts were deposited by drop-casting on screen-printed electrodes and characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and potentiometry. Covalent binding between the solid contact and the ISM was obtained via photopolymerization in order to increase the robustness of the Ca 2+ -SCISEs. The performance of the Ca 2+ -SCISEs was studied by measuring their potentiometric response and their sensitivity to light, oxygen and carbon dioxide. Meth-PEDOT was found to be a promising solid-contact material to develop low-cost and easy to prepare ISEs. Copyright © 2018 Elsevier B.V. All rights reserved.

Superficial and Inner Examination of a Microwave-Irradiated Dental Acrylic Resin and Its Metal-Polymer Interface.

PubMed

Popescu, Marian C; Bita, Bogdan I; Tucureanu, Vasilica; Vasilache, Dan; Banu, Melania A; Avram, Andrei M; Giurescu-Dumitrescu, Raluca A

2018-02-01

The aim of this study is to conduct an extended surface and cross-section characterization of a denture base acrylic resin subjected to 500, 650, and 750 W microwave irradiation for 2, 3, and 5 min to assess its morphological modifications. A commercial heat-cured powder was polymerized according to the manufacturer's specifications and distributed into 20 circular samples. A stainless-steel wire was partially embedded in half of the discs, in order to investigate the metal-polymer interface. High-resolution scanning electron microscopy (SEM) imaging, white light interferometry, roughness measurements and Fourier transform infrared spectrometry were employed for morphological and structural evaluation of the irradiated polymer. Superficial adaptation was discovered after 5 min exposure at 500 W, 650 W, and 750 W, revealing significant roughness correction for 750 W. SEM characterization revealed the inner alteration of the resin for the 750 W protocol and a metal-polymer gap developed regardless of the irradiation conditions. The considerable temperature fluctuations that the samples were subject to during the experiments did not essentially change the poly(methyl-methacrylate) bond structure.

Surface characterization of lignocellulosics for composite manufacture

NASA Astrophysics Data System (ADS)

Iyer, Ananth V.

The objectives of this research were to form moisture resistant wheat strawboards, either by altering the straw surface characteristics or by changing the chemistry of the polymeric 4, 4' diphenylmethane diisocyanate (PMDI)-based matrix and interface. Part I compared the surface characteristics of wheat, barley, oat, rice, kenaf, hemp and softwood particles. All cereal straws had two surfaces: epidermis and brittle-pith unlike one heterogeneous type observed for bast fibers and softwood particles. The epidermis of cereal straws was not wet by water or aqueous binders, whereas the pith surface allowed the penetration of water, but was not readily wetted by aqueous binders. Between the different surface treatments evaluated for wheat straw in Part II, NaOH selectively peeled-off the epidermis and pith layers. The treated straw particles were formable into strawboards using aqueous phenol-formaldehyde, urea-formaldehyde, and duroplastic acrylic acid binders with good internal bond strength (IBS) and adequate water resistance. In Part III it was shown that, decreasing straw particle sizes and bleaching worsened the mechanical properties of strawboards, but the moisture absorption properties of bleached strawboards were lower than the unbleached ones. Layering of straw particles in strawboards did not seem to affect their mechanical or moisture absorption properties. Part IV showed that the pith surface of wheat straw was fractured on curing with PMDI, providing hollow microcrevices for water accumulation. Furthermore, the cured PMDI formed a network polyurea/polyuretonimine/polycarbodiimide/polyisocyanurate polymer on straw surfaces whose properties dictated the properties of strawboards. Among the different mono-, bi-, and tri-functional alcohols, amines and carboxylic acids evaluated in Part V as H-donor substitutes to moisture for reaction with PMDI on straw surfaces, ethylene glycol, resorcinol, glycerin and citric acid provided IBS values greater than the ANSI recommended minimum (60 psi) and lower thickness swell values than the moisture-cure process. In Part VI, strawboards formed with 2% PMDI and 5% epoxy or duroplastic acrylic acid binders had high IBS values, and their thickness swell after 24 h soaking in water was restricted to 13%, which was much lower than the ˜18--20% values obtained for strawboards made with 5% PMDI.

Effect of rutile titania dioxide nanoparticles on the mechanical property, thermal stability, weathering resistance and antibacterial property of styrene acrylic polyurethane coating

NASA Astrophysics Data System (ADS)

Vuong Nguyen, Thien; Nguyen, Tuan Anh; Dao, Phi Hung; Phuc Mac, Van; Hiep Nguyen, Anh; Thanh Do, Minh; Nguyen, The Huu

2016-12-01

This study aims to enhance the mechanical properties, thermal stability, weathering resistance and antibacterial property of a styrene acrylic polyurethane coating by adding rutile titania dioxide (R-TiO2) nanoparticles in coating formulation. The styrene acrylic polyurethane/R-TiO2 nanocomposite had been prepared by using ultrasonication. The effects of nanoparticles on the mechanical properties, thermal stability and weathering resistance of as-prepared coatings were investigated by using the adhesion strength and ball impact tests, the Fourier transform infrared and UV-vis analyses, thermogravimetric analysis (TGA), and UV/condensation weathering chamber equipped with UVA-340 fluorescent lamps, respectively. The disperse quality of nanoparticles in the coating was examined by using the field emission scanning electron microscope (FESEM). The mechanical test results showed that suitable content of R-TiO2 nanoparticles in the nanocomposite coating was 2 wt%. The FESEM images indicated that the nanoparticles were dispersed homogeneously into the entire volume of the coating. For the nanocomposite prepared by 3 h of ultrasonication, the average size of nanoparticles was in range of 40-50 nm. The ball impact and adhesion tests showed that the incorporation of nanoparticles into the coating significantly enhanced the impact strength from 120 to 145 kg cm and increased the adhesion from level 1 to level 0. The TGA test illustrated that in presence of nanoparticles, the decomposition temperature of coating increased from 146.9 °C to 154.21 °C. For the temperature at 50% loss in mass (T 50%), it was found that the T 50% of the neat coating is 351.86 °C. Adding the 2 wt% R-TiO2 nanoparticles into coating increased the T 50% value to 360.06 °C. After UV/condensation accelerated weathering test (30 cycles), the significant improvement in weight loss, impact strength and adhesion of the neat coating was observed with the presence of nanoparticles. The antibacterial test showed that in the nanocomposite coating, R-TiO2 nanoparticles exhibited their photocatalytic effect in the inhibition against E. coli bacterial growth. Incorporating 2 wt% of R-TiO2 nanoparticles into the coating reduced the bacterial concentration by 6.1% after 60 min of culture.

Modified EVA Encapsulant Formulations for Low Temperature Processing: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mei, Z.; Pern, F. J.; Glick, S. H.

2001-10-01

Presented at the 2001 NCPV Program Review Meeting: We have developed several new ethylene-vinyl acetate (EVA) formulations modified on the basis of NREL patented EVA formulations [1]. The new formulations can be cured to a desired gel content of {approx}80% in the ambient at temperatures 20-30 C lower than the typical conditions in vacuum (i.e. {approx}150 C). Glass/glass laminates showed transmittance spectra that are essentially the same as that of EVA 15295P in the visible and NIR regions but higher in the UV region. Results of fluorescence analysis of the ambient-processed new EVA formulations showed the concentrations of the curing-generatedmore » {alpha},{beta}-unsaturated carbonyl chromophores, which are responsible for the UV induced EVA discoloration and photodegradation, were considerably lower than that of EVA 15295P, therefore suggesting a better photochemical stability of new EVA formulations.« less

Development of aircraft lavatory compartments with improved fire resistance characteristics. Phase 4: Sandwich panel decorative ink development

NASA Technical Reports Server (NTRS)

Jayarajan, A.; Johnson, G. A.; Korver, G. L.; Anderson, R. A.

1983-01-01

Five chemically different resin systems with improved fire resistance properties were studied for a possible screenprinting ink application. Fire resistance is hereby defined as the cured ink possessing improvements in flammability, smoke emission, and thermal stability. The developed ink is for application to polyvinyl fluoride film. Only clear inks without pigments were considered. Five formulations were evaluated compared with KC4900 clear acrylic ink, which was used as a baseline. The tests used in the screening evaluation included viscosity, smoke and toxic gas emission, limiting oxygen index (LOI), and polyvinyl fluoride film (PVF) printability. A chlorofluorocarbon resin (FPC461) was selected for optimization studies. The parameters for optimization included screenprinting process performance, quality of coating, and flammability of screenprinted 0.051-mm (0.002-in.) white Tedlar. The quality of the screenprinted coating on Tedlar is dependent on viscosity, curing time, adhesion to polyvinyl fluoride film, drying time (both inscreen and as an applied film), and silk screen mesh material and porosity.

Weak interfaces for UV cure nanoimprint lithography

NASA Astrophysics Data System (ADS)

Houle, Frances; Fornof, Ann; Simonyi, Eva; Miller, Dolores; Truong, Hoa

2008-03-01

Nanoimprint lithography using a photocurable organic resist provides a means of patterning substrates with a spatial resolution in the few nm range. The usefulness of the technique is limited by defect generation during template removal, which involves fracture at the interface between the template and the newly cured polymer. Although it is critical to have the lowest possible interfacial fracture toughness (Gc less than 0.1 Jm-2) to avoid cohesive failure in the polymer, there is little understanding on how to achieve this using reacting low viscosity resist fluids. Studies of debonding of a series of free-radical cured polyhedral silsesquioxane crosslinker formulations containing selected reactive diluents from fluorosilane-coated quartz template materials will be described. At constant diluent fraction the storage modulus of cured resists follows trends in initial reaction rate, not diluent Tg. Adhesion is uncorrelated with both Tg and storage modulus. XPS studies of near-interface compositions indicate that component segregation within the resist fluid on contact with the template, prior to cure, plays a significant role in controlling the fracture process.

Production of cured meat color in nitrite-free Harbin red sausage by Lactobacillus fermentum fermentation.

PubMed

Zhang, Xue; Kong, Baohua; Xiong, Youling L

2007-12-01

Lactobacillus fermentum was substituted for nitrite to produce cured pink color in a Chinese-style sausage. Treatments included inoculations (10(4), 10(6), and 10(8)CFU/g meat) followed by fermentation at 30°C for 8h and then at 4°C for 16h. Control sausage (with sodium nitrite, 60mg/kg meat) was cured at 4°C for 24h without L. fermentum. The UV-Vis spectra of pigment extract from L. fermentum-treated sausage were identical to that of nitrosylmyoglobin (NO-Mb) formed in nitrite-treated control. The NO-Mb concentration and the colorimetric a(∗) value of sausage treated with 10(8)CFU/g meat of L. fermentum essentially replicated those in nitrite-cured meat. Free amino acid content in sausage treated with L. fermentum was greater and the pH slightly lower compared with the nitrite-cured control sample. This study showed that L. fermentum has the potential to substitute for nitrite in the sausage production.

UV-Surface Treatment of Fungal Resistant Polyether Polyurethane Film-Induced Growth of Entomopathogenic Fungi.

PubMed

Lando, Gabriela Albara; Marconatto, Letícia; Kessler, Felipe; Lopes, William; Schrank, Augusto; Vainstein, Marilene Henning; Weibel, Daniel Eduardo

2017-07-18

Synthetic polymers are the cause of some major environmental impacts due to their low degradation rates. Polyurethanes (PU) are widely used synthetic polymers, and their growing use in industry has produced an increase in plastic waste. A commercial polyether-based thermoplastic PU with hydrolytic stability and fungus resistance was only attacked by an entomopathogenic fungus, Metarhiziumanisopliae , when the films were pre-treated with Ultraviolet (UV) irradiation in the presence of reactive atmospheres. Water contact angle, Fourier transform infrared spectroscopy in attenuated total reflection mode (FTIR-ATR), scanning electron microscopy (SEM), and profilometer measurements were mainly used for analysis. Permanent hydrophilic PU films were produced by the UV-assisted treatments. Pristine polyether PU films incubated for 10, 30, and 60 days did not show any indication of fungal growth. On the contrary, when using oxygen in the UV pre-treatment a layer of fungi spores covered the sample, indicating a great adherence of the microorganisms to the polymer. However, if acrylic acid vapors were used during the UV pre-treatment, a visible attack by the entomopathogenic fungi was observed. SEM and FTIR-ATR data showed clear evidence of fungal development: growth and ramifications of hyphae on the polymer surface with the increase in UV pre-treatment time and fungus incubation time. The results indicated that the simple UV surface activation process has proven to be a promising alternative for polyether PU waste management.

Electrical Properties and Manufacturability of ITO-MgF2 and Related Transparent Arcproof Spacecraft Coatings

NASA Technical Reports Server (NTRS)

Hambourger, Paul D.

2003-01-01

To investigate the applicability of co-deposited indium tin oxide and magnesium fluoride as a transparent arcproof coating on the exterior of PowerSphere microsatellites. This included testing coating performance after deposition on flexible polymeric substrates, determining whether ultraviolet (UV) radiation present during deposition might affect the UV-curing resin contained in the substrate, and preparation of coated polymeric samples for radiation damage studies by the PowerSphere team.

Meeting Future C3I (Command-Control-Communications-Intelligence) Needs with Fiber Optics,

DTIC Science & Technology

1985-05-01

Frequency dependence of the sensitivity of fibers with hard coatings is relatively small. Nylon gives the weakest dependence, while the soft UV -cured...elastomer gives the strongest. Maximum sensitivity is obtained with Teflon TFE, while the minimum is achieved with the soft UV coating. With the latter...fiber-optics systems: the LED (Light Emitting Diode) and ILD (Injection Laser Diode). These devices emit light when an electric current is applied. The

Comparative evaluation of different thermally modified wood samples finishing with UV-curable and waterborne coatings

NASA Astrophysics Data System (ADS)

Herrera, René; Muszyńska, Monika; Krystofiak, Tomasz; Labidi, Jalel

2015-12-01

Thermally modified wood has been developed as an industrial method to improve durability and dimensional stability of wood and thus extends the range of uses and service life of wood-based products. Despite the improvements gained by treatment, surface finishing using coatings prevents esthetical changes such as color degradation or occasional growth of mold adding protection in outdoor use and extending the service life of products. The wood finishing process was carried out with commercially available waterborne and UV-curable coatings on industrially modified at 192, 200, 212 °C and unmodified European ash (Fraxinus excelsior L.) wood, using an industrial rollers system and a laboratory brushing system. Changes caused by thermal treatment which could affect the surface finish were measured and compared with control samples, such as water uptake, wettability and acidity. Following the wood finishing, surface properties and esthetic changes were evaluated; as well as the coatings performance. Thermally modified wood presented improved adherence compared with unmodified wood with a significant improvement in samples modified at 212 °C, which also present the highest hardness when UV-cured. Finishes with UV-curing maintain the hydrophobic effect of thermally modified wood, whereas waterborne finishes increase the surface wettability. Thermal modification did not negatively influence on the elastic properties of the coated substrate and thus allows this material to be finished with different coating systems in the same conditions as unmodified wood.

Effect of cavity preparation on the flexural strengths of acrylic resin repairs

PubMed Central

ELHADIRY, Safa Salim; YUNUS, Norsiah; ARIFFIN, Yusnidar Tajul

2010-01-01

Objective To investigate the effect of cavity preparation on the flexural strength of heat-curing denture resin when repaired with an auto-curing resin. Material and methods Ninety-six rectangular specimens (64x10x2.5 mm) prepared from heat-curing denture base resin (Meliodent) were randomly divided into four groups before repair. One group was left intact as control. Each repair specimen was sectioned into two; one group was repaired using the conventional repair method (Group 1). Two groups had an additional transverse cavity (2x3.5x21.5 mm) prepared prior to the repair; one repaired with (Group 2) and one without glass-fiber reinforcement (Group 3). A three-point flexural bending test according to the ISO 1567:1999 specification8 for denture base polymers was carried out on all groups after 1, 7 and 30 days of water immersion. Statistical analysis was carried out using two-way ANOVA, Kruskal Wallis and post-hoc Mann Whitney tests. Results The highest flexural strength was observed in the control group. Control and conventional repairs group (Group 1) showed reduction in the flexural strength 30 days after water immersion. No significant change in the strength was observed for Groups 2 and 3 where the repair joints were similarly prepared with additional transverse cavity. Conclusion Repaired specimens showed lower flexural strength values than intact heat-curing resin. Cavity preparation had no significant effect on the flexural strength of repair with water immersion. PMID:21308283

Optically transparent/colorless polyimides

NASA Technical Reports Server (NTRS)

Stclair, A. K.; Stclair, T. L.; Slemp, W.; Ezzell, K. S.

1985-01-01

Several series of linear aromatic polyimide films have been synthesized and characterized with the objective of obtaining maximum optical transparency. Two approaches have been used as part of this structure-property relationship study. The first approach is to vary the molecular structure so as to separate chromophoric centers and reduce electronic interactions between polymer chains to lower the intensity of color in the resulting polymer films. A second and concurrent approach is to perform polymerizations with highly purified monomers. Glass transition temperatures of thermally cured polyimide films are obtained by thermomechanical analysis and thermal decomposition temperatures are determined by thermogravimetric analysis. Transmittance UV-visible spectra of the polyimide films are compared to that of a commercial polyimide film. Fully imidized films are tested for solubility in common organic solvents. The more transparent films prepared in this study are evaluated for use on second-surface mirror thermal control coating systems. Lightly colored to colorless films are characterized by UV-visible spectroscopy before and after exposure to 300 equivalent solar hours UV irradiation and varying doses of 1 MeV electron irradiation. The effects of monomer purity, casting solvent and cure atmosphere on polyimide film transparency are also investigated.

Preparation and Characterization of UV Emitting Fluoride Phosphors for Phototherapy Lamps

NASA Astrophysics Data System (ADS)

Belsare, P. D.; Moharil, S. V.; Joshi, C. P.; Omanwar, S. K.

2011-10-01

The use of ultraviolet radiation for the treatment of various skin diseases is well known for long time. Phototherapy employs ultraviolet-blue radiation to cure skin diseases. The basis of phototherapy is believed to be the direct interaction of light of certain frequencies with tissue to cause a change in immune response. Currently dermatologists use UV lamps having specific emissions in UV region for treating various skin diseases. The treatment of skin diseases using artificial sources of UV radiation is now well established and more than 50 types of skin diseases are treated by phototherapy. This is an effective treatment for many skin disorders, such as psoriasis, vitiligo, ofujis disease, morphea , scleroderma, cutaneous T-cell lymphoma, lupus erythematosus, hyperbilirubinemia commonly known as infant jaundice, acne vulgaris, This paper reports photoluminescence properties of UV emitting fluoride phosphors prepared by wet chemical method. Emission characteristics of these phosphors are found similar to those of commercial UV lamp phosphors with comparable intensities. The usefulness of UV emitting fluoride phosphor is discussed in the paper.

Investment casting using multi-jet modelling patterns: the thermogravimetric analysis of visijet® SR200 UV curable acrylate plastic

NASA Astrophysics Data System (ADS)

Hafsa, M. N.; Ibrahim, M.; Sharif, S.

2013-12-01

Rapid Prototyping (RP) technology is actively studied to be implemented in Investment Casting (IC) process. Nowadays RP techniques are studied for their feasibility as IC master patterns, in terms of pattern collapsibility and drainage during burnout. The purpose of the study is to determine the characteristic of Visijet® SR200 acrylate material during burnout process. Traditional IC patterns made from wax have properties that limit their application in precision casting, especially for parts with thin geometries that readily break or deform when handled or dipped in the refractory slurry. Furthermore, it is not economical when producing a small number of parts. Non wax patterns fabricated for IC process, revealed ceramic shell cracking due to excessive thermal expansions, incomplete collapsibility of pattern during burnout, residual ash and poor surface finish. Thermogravimetric analysis (TGA) was used to measured the weight loss of acrylate material as the temperature was increased. TGA measured the change of material's mass as it is heated. It represents the decomposition temperature after being subjected to varying temperatures, as well as the amount of residual ash. In this experiment, the temperature range was from 20°C to 700°C with 5°C increment. Experiment results show the values of material's optimum reaction temperature and decomposing temperature of Visijet® SR200 acrylate. The percentages of remaining materials were also monitored throughout the process to obtain the amount of residual ash. All of the temperature values obtained is a resemblance for the actual burnout process and can be used as references.

Imprintable, bendable, and shape-conformable polymer electrolytes for versatile-shaped lithium-ion batteries.

PubMed

Kil, Eun-Hye; Choi, Keun-Ho; Ha, Hyo-Jeong; Xu, Sheng; Rogers, John A; Kim, Mi Ri; Lee, Young-Gi; Kim, Kwang Man; Cho, Kuk Young; Lee, Sang-Young

2013-03-13

A class of imprintable, bendable, and shape-conformable polymer electrolyte with excellent electrochemical performance in a lithium battery system is reported. The material consists of a UV-cured polymer matrix, high-boiling point liquid electrolyte, and Al2 O3 nanoparticles, formulated for use in lithium-ion batteries with 3D-structured electrodes or flexible characteristics. The unique structural design and well-tuned rheological characteristics of the UV-curable electrolyte mixture, in combination with direct UV-assisted nanoimprint lithography, allow the successful fabrication of polymer electrolytes in geometries not accessible with conventional materials. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

UV-CURED FINISHING WORKS FOR LANE

EPA Science Inventory

The Midwest Research Institute, under a cooperative agreement with the U.S. EPA, conducted a study to identify wood furniture manufacturing facilities that had converted to low-VOC/HAP wood furniture coatings and to develop case studies for those facilities. This article addresse...

Jet printing of convex and concave polymer micro-lenses.

PubMed

Blattmann, M; Ocker, M; Zappe, H; Seifert, A

2015-09-21

We describe a novel approach for fabricating customized convex as well as concave micro-lenses using substrates with sophisticated pinning architecture and utilizing a drop-on-demand jet printer. The polymeric lens material deposited on the wafer is cured by UV light irradiation yielding lenses with high quality surfaces. Surface shape and roughness of the cured polymer lenses are characterized by white light interferometry. Their optical quality is demonstrated by imaging an USAF1951 test chart. The evaluated modulation transfer function is compared to Zemax simulations as a benchmark for the fabricated lenses.

Investigation of Test Methods, Material Properties, and Processes for Solar Cell Encapsulants

NASA Technical Reports Server (NTRS)

1979-01-01

During this quarter the technical activities were directed toward the reformulation of ethylene/vinyl acetate copolymer for use as a compound in solar cell module fabrication. Successful formulations were devised that lowered the temperature required for cure and raised the gel content. A major volatile component was also eliminated (acrylate crosslinking agent) which should aid in the production of bubble free laminates. Adhesive strengths and primers for the bonding of ethylene/vinyl acetate to supersyrate and substrate materials was assessed with encouraging results. The incorporation of silane compounds gave high bond strengths. A survey of scrim materials was also conducted.

High Refractive Organic–Inorganic Hybrid Films Prepared by Low Water Sol-Gel and UV-Irradiation Processes

PubMed Central

Ma, Hsiao-Yuan; Wang, Tzong-Liu; Chang, Pei-Yu; Yang, Chien-Hsin

2016-01-01

Organic-inorganic hybrid sols (Ti–O–Si precursor) were first synthesized by the sol-gel method at low addition of water, and were then employed to prepare a highly refractive hybrid optical film. This film was obtained by blending the Ti–O–Si precursor with 2-phenylphenoxyethyl acrylate (OPPEA) to perform photo-polymerization by ultraviolet (UV) irradiation. Results show that the film transparency of poly(Ti–O–Si precursor-co-OPPEA) film is higher than that of a pure poly(Ti–O–Si precursor) film, and that this poly(Ti–O–Si precursor-co-OPPEA) hybrid film exhibits a high transparency of ~93.7% coupled with a high refractive index (n) of 1.83 corresponding to a thickness of 2.59 μm. PMID:28344303

DCT-TCI: Real Gas Characterization of Plasma Flow Control - An Integrated Approach

DTIC Science & Technology

2011-12-23

as Navier-Stokes equations are solved in this study. We utilize the two-species basic model to reduce the computational complexity of plasma...constant of 3.0. Copper tape was first adhered to both sides of a 3 mm thick acrylic plate. A negative photo-resist, a transparent film and a UV light...ferric chloride. The reminiscence of the adhesive glue left behind by the copper tape was removed using a solvent such as methanol or acetone. The

Custom fabrication of biomass containment devices using 3-D printing enables bacterial growth analyses with complex insoluble substrates.

PubMed

Nelson, Cassandra E; Beri, Nina R; Gardner, Jeffrey G

2016-11-01

Physiological studies of recalcitrant polysaccharide degradation are challenging for several reasons, one of which is the difficulty in obtaining a reproducibly accurate real-time measurement of bacterial growth using insoluble substrates. Current methods suffer from several problems including (i) high background noise due to the insoluble material interspersed with cells, (ii) high consumable and reagent cost and (iii) significant time delay between sampling and data acquisition. A customizable substrate and cell separation device would provide an option to study bacterial growth using optical density measurements. To test this hypothesis we used 3-D printing to create biomass containment devices that allow interaction between insoluble substrates and microbial cells but do not interfere with spectrophotometer measurements. Evaluation of materials available for 3-D printing indicated that UV-cured acrylic plastic was the best material, being superior to nylon or stainless steel when examined for heat tolerance, reactivity, and ability to be sterilized. Cost analysis of the 3-D printed devices indicated they are a competitive way to quantitate bacterial growth compared to viable cell counting or protein measurements, and experimental conditions were scalable over a 100-fold range. The presence of the devices did not alter growth phenotypes when using either soluble substrates or insoluble substrates. We applied biomass containment to characterize growth of Cellvibrio japonicus on authentic lignocellulose (non-pretreated corn stover), and found physiological evidence that xylan is a significant nutritional source despite an abundance of cellulose present. Copyright © 2016 Elsevier B.V. All rights reserved.

Clinical Issues-October 2016.

PubMed

Wood, Amber

2016-10-01

Wearing nail polish Key words: nail, polish, UV-cured, gel nail, Shellac. Preventing dry skin Key words: dry skin, chapped, dermatitis, hand hygiene. Wearing rings Key words: ring, jewelry, wedding ring, band, hand hygiene. Copyright © 2016 AORN, Inc. Published by Elsevier Inc. All rights reserved.

UV-Surface Treatment of Fungal Resistant Polyether Polyurethane Film-Induced Growth of Entomopathogenic Fungi

PubMed Central

Lando, Gabriela Albara; Marconatto, Letícia; Schrank, Augusto; Vainstein, Marilene Henning

2017-01-01

Synthetic polymers are the cause of some major environmental impacts due to their low degradation rates. Polyurethanes (PU) are widely used synthetic polymers, and their growing use in industry has produced an increase in plastic waste. A commercial polyether-based thermoplastic PU with hydrolytic stability and fungus resistance was only attacked by an entomopathogenic fungus, Metarhiziumanisopliae, when the films were pre-treated with Ultraviolet (UV) irradiation in the presence of reactive atmospheres. Water contact angle, Fourier transform infrared spectroscopy in attenuated total reflection mode (FTIR-ATR), scanning electron microscopy (SEM), and profilometer measurements were mainly used for analysis. Permanent hydrophilic PU films were produced by the UV-assisted treatments. Pristine polyether PU films incubated for 10, 30, and 60 days did not show any indication of fungal growth. On the contrary, when using oxygen in the UV pre-treatment a layer of fungi spores covered the sample, indicating a great adherence of the microorganisms to the polymer. However, if acrylic acid vapors were used during the UV pre-treatment, a visible attack by the entomopathogenic fungi was observed. SEM and FTIR-ATR data showed clear evidence of fungal development: growth and ramifications of hyphae on the polymer surface with the increase in UV pre-treatment time and fungus incubation time. The results indicated that the simple UV surface activation process has proven to be a promising alternative for polyether PU waste management. PMID:28718785

Measuring UV Curing Parameters of Commercial Photopolymers used in Additive Manufacturing.

PubMed

Bennett, Joe

2017-12-01

A testing methodology was developed to expose photopolymer resins and measure the cured material to determine two key parameters related to the photopolymerization process: E c (critical energy to initiate polymerization) and D p (penetration depth of curing light). Five commercially available resins were evaluated under exposure from 365 nm and 405 nm light at varying power densities and energies. Three different methods for determining the thickness of the cured resin were evaluated. Caliper measurements, stylus profilometry, and confocal laser scanning microscopy showed similar results for hard materials while caliper measurement of a soft, elastomeric material proved inaccurate. Working curves for the five photopolymers showed unique behavior both within and among the resins as a function of curing light wavelength. E c and D p for the five resins showed variations as large as 10×. Variations of this magnitude, if unknown to the user and not controlled for, will clearly affect printed part quality. This points to the need for a standardized approach for determining and disseminating these, and perhaps, other key parameters.

A low-cost, manufacturable method for fabricating capillary and optical fiber interconnects for microfluidic devices.

PubMed

Hartmann, Daniel M; Nevill, J Tanner; Pettigrew, Kenneth I; Votaw, Gregory; Kung, Pang-Jen; Crenshaw, Hugh C

2008-04-01

Microfluidic chips require connections to larger macroscopic components, such as light sources, light detectors, and reagent reservoirs. In this article, we present novel methods for integrating capillaries, optical fibers, and wires with the channels of microfluidic chips. The method consists of forming planar interconnect channels in microfluidic chips and inserting capillaries, optical fibers, or wires into these channels. UV light is manually directed onto the ends of the interconnects using a microscope. UV-curable glue is then allowed to wick to the end of the capillaries, fibers, or wires, where it is cured to form rigid, liquid-tight connections. In a variant of this technique, used with light-guiding capillaries and optical fibers, the UV light is directed into the capillaries or fibers, and the UV-glue is cured by the cone of light emerging from the end of each capillary or fiber. This technique is fully self-aligned, greatly improves both the quality and the manufacturability of the interconnects, and has the potential to enable the fabrication of interconnects in a fully automated fashion. Using these methods, including a semi-automated implementation of the second technique, over 10,000 interconnects have been formed in almost 2000 microfluidic chips made of a variety of rigid materials. The resulting interconnects withstand pressures up to at least 800psi, have unswept volumes estimated to be less than 10 femtoliters, and have dead volumes defined only by the length of the capillary.

Silver nanowire-carbon fiber cloth nanocomposites synthesized by UV curing adhesive for electrochemical point-of-use water disinfection.

PubMed

Hong, Xuesen; Wen, Junjie; Xiong, Xuhua; Hu, Yongyou

2016-07-01

Novel silver nanowire (AgNW) - carbon fiber cloth (CC) nanocomposites were synthesized by a rapid and facile method. Acting as filter in an electrical gravity filtration device, the AgNW-CC nanocomposites were applied to electrochemical point-of-use water disinfection. AgNW-CC nanocomposites were characterized by FESEM, XRD, and FTIR. Their disinfection performance toward Escherichia coli and bacteriophage MS2 was evaluated by inhibition zone tests, optical density growth curve tests, and flow tests. The results showed that complex 3D AgNW networks with controllable silver release (<100 ppb) were fabricated on CC by using UV curing adhesive. AgNW-CC nanocomposites exhibited excellent intrinsic antibacterial activities against E. coli. The concentration of AgNWs and UV adhesive controlled the released silver and hence led to the change in antibacterial activity. The external electric field significantly enhanced the disinfection efficiency of AgNW-CC nanocomposites. Over 99.999% removal of E. coli and MS2 could be achieved. More complex AgNW networks contributed to higher disinfection efficiency under 10 V and 10(6) CFU (PFU) mL(-1) of microorganism. UV adhesive could keep the disinfection performance from being affected by flow rate. The convenient synthesis and outstanding disinfection performance offer AgNW-CC nanocomposites opportunities in the application of electrochemical point-of-use drinking water disinfection. Copyright © 2016 Elsevier Ltd. All rights reserved.

Development of ultraviolet rigidizable materials. [expandable space erectable structures

NASA Technical Reports Server (NTRS)

Salisbury, D. P.

1979-01-01

A series of tests was performed to determine an optimum resin to be used as a UV rigidizable matrix in expandable rigidizable space structures. Commercially available resins including several types of polyesters, epoxies, epoxy-acrylics, an acrylic and a urethane were used as well as a polyester, produced by 3M Company's Solar Laboratory facility, which was found the best from the standpoint of physical properties and ability to be 'B' staged. Two other synthesized materials were also tested, but were not found to be superior to the Solar resin. An optimum fabric for use with the preferred resin was not found; however, the 15 ounce fabric from Solar Laboratories has the best combination of physical properties with respect to handling and processing characteristics. Expansion techniques for tubular structures, 'B' staging of the solar resin, and stowage techniques for up to 5 months were developed. A one meter high tetrahedron preprototype structure was prepared to evaluate and demonstrate stowage, deployment, and rigidization techniques.

Method of holding optical elements without deformation during their fabrication

DOEpatents

Hed, P.P.

1997-04-29

An improved method for securing and removing an optical element to and from a blocking tool without causing deformation of the optical element is disclosed. A lens tissue is placed on the top surface of the blocking tool. Dots of UV cement are applied to the lens tissue without any of the dots contacting each other. An optical element is placed on top of the blocking tool with the lens tissue sandwiched therebetween. The UV cement is then cured. After subsequent fabrication steps, the bonded blocking tool, lens tissue, and optical element are placed in a debonding solution to soften the UV cement. The optical element is then removed from the blocking tool. 16 figs.

Method of holding optical elements without deformation during their fabrication

DOEpatents

Hed, P. Paul

1997-01-01

An improved method for securing and removing an optical element to and from a blocking tool without causing deformation of the optical element. A lens tissue is placed on the top surface of the blocking tool. Dots of UV cement are applied to the lens tissue without any of the dots contacting each other. An optical element is placed on top of the blocking tool with the lens tissue sandwiched therebetween. The UV cement is then cured. After subsequent fabrication steps, the bonded blocking tool, lens tissue, and optical element are placed in a debonding solution to soften the UV cement. The optical element is then removed from the blocking tool.

Rapid prototyping of microstructures in polydimethylsiloxane (PDMS) by direct UV-lithography.

PubMed

Scharnweber, Tim; Truckenmüller, Roman; Schneider, Andrea M; Welle, Alexander; Reinhardt, Martina; Giselbrecht, Stefan

2011-04-07

Microstructuring of polydimethylsiloxane (PDMS) is a key step for many lab-on-a-chip (LOC) applications. In general, the structure is generated by casting the liquid prepolymer against a master. The production of the master in turn calls for special equipment and know how. Furthermore, a given master only allows the reproduction of the defined structure. We report on a simple, cheap and practical method to produce microstructures in already cured PDMS by direct UV-lithography followed by chemical development. Due to the available options during the lithographic process like multiple exposures, the method offers a high design flexibility granting easy access to complex and stepped structures. Furthermore, no master is needed and the use of pre-cured PDMS allows processing at ambient (light) conditions. Features down to approximately 5 µm and a depth of 10 µm can be realised. As a proof of principle, we demonstrate the feasibility of the process by applying the structures to various established soft lithography techniques.

Utilization of UV Curing Technology to Significantly Reduce the Manufacturing Cost of LIB Electrodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Voelker, Gary; Arnold, John

2015-11-30

Previously identified novel binders and associated UV curing technology have been shown to reduce the time required to apply and finish electrode coatings from tens of minutes to less than one second. This revolutionary approach can result in dramatic increases in process speeds, significantly reduced capital (a factor of 10 to 20) and operating costs, reduced energy requirements, and reduced environmental concerns and costs due to the virtual elimination of harmful volatile organic solvents and associated solvent dryers and recovery systems. The accumulated advantages of higher speed, lower capital and operating costs, reduced footprint, lack of VOC recovery, and reducedmore » energy cost is a reduction of 90% in the manufacturing cost of cathodes. When commercialized, the resulting cost reduction in Lithium batteries will allow storage device manufacturers to expand their sales in the market and thereby accrue the energy savings of broader utilization of HEVs, PHEVs and EVs in the U.S., and a broad technology export market is also envisioned.« less

Research of vacuum polymer film on three-dimension surface (Conference Presentation)

NASA Astrophysics Data System (ADS)

Bau, Yung-Han

2016-09-01

This study focused on UV-curable acrylic hybrid of solute in vacuum-deposited on the surface and make it smooth. On the surface coating of the entire process, including the pre-treatment of organic solutes, vacuum, nozzle pressure, airflow, frequency ratio, the surface of the rotation rate, nozzle angle, UV light irradiation time, waste solute recycling.Organic solutes through a flow meter and precise measured,by high pressure or vibration of a piezoelectric material, spray our organic solute in a certain degree of vacuum,leaving nozzle of tiny micro-mist volatiles in a vacuum to form secondary atomization,deposited our surface,Since no UV light irradiation, the surface is a liquid having fluidity, so the non-planar substrates can have good performance, finally it is irradiated by UV light of sufficient energy solidify to form a solid film.The advantage of this approach is that a smooth surface,Strong adhesion, low-cost equipment, low temperature, a wide range of high deposition rate can be combined with other deposition method,Under vacuum have not waste because excess paint can be recycled.Avoid solute direct contact with human, relative to the environment-friendly.

Effect of ultrasonic tip designs on intraradicular post removal.

PubMed

Aguiar, Anny Carine Barros; de Meireles, Daniely Amorim; Marques, André Augusto Franco; Sponchiado Júnior, Emílio Carlos; Garrido, Angela Delfina Bitencourt; Garcia, Lucas da Fonseca Roberti

2014-11-01

To evaluate the effect of different ultrasonic tip designs on intraradicular post removal. The crowns of forty human canine teeth were removed, and after biomechanical preparation and filling, the roots were embedded in acrylic resin blocks. The post spaces were made, and root canal molding was performed with self-cured acrylic resin. After casting (Cu-Al), the posts were cemented with zinc phosphate cement. The specimens were randomly separated into 4 groups (n = 10), as follows: G1 - no ultrasonic vibration (control); G2 - ultrasonic vibration using an elongated cylindrical-shaped and active rounded tip; G3 - ultrasonic vibration with a flattened convex and linear active tip; G4 - ultrasonic vibration with active semicircular tapered tip. Ultrasonic vibration was applied for 15 seconds on each post surface and tensile test was performed in a Universal Testing Machine (Instron 4444 - 1 mm/min). G4 presented the highest mean values, however, with no statistically significant difference in comparison to G3 (P > 0.05). G2 presented the lowest mean values with statistically significant difference to G3 and G4 (P < 0.05). Ultrasonic vibration with elongated cylindrical-shaped and active rounded tip was most effective in reducing force required for intraradicular post removal.

The Design and Synthesis of Epoxy Matrix Composites Curable by Electron Beam Induced Cationic Polymerization

NASA Technical Reports Server (NTRS)

Crivello, James V.

2000-01-01

Several new series of novel, high reactivity epoxy resins are described which are designed specifically for the fabrication of high performance carbon fiber reinforced composites for commercial aircraft structural applications using cationic UV and e-beam curing. The objective of this investigation is to provide resin matrices which rapidly and efficiently cure under low e-beam doses which are suitable to high speed automated composite fabrication techniques such as automated tape and tow placement. It was further the objective of this work to provide resins with superior thermal, oxidative and atomic oxygen resistance.

Lifetime Improvement of Organic Light Emitting Diodes using LiF Thin Film and UV Glue Encapsulation

NASA Astrophysics Data System (ADS)

Huang, Jian-Ji; Su, Yan-Kuin; Chang, Ming-Hua; Hsieh, Tsung-Eong; Huang, Bohr-Ran; Wang, Shun-Hsi; Chen, Wen-Ray; Tsai, Yu-Sheng; Hsieh, Huai-En; Liu, Mark O.; Juang, Fuh-Shyang

2008-07-01

This work demonstrates the use of lithium fluoride (LiF) as a passivation layer and a newly developed UV glue for encapsulation on the LiF passivation layer to enhance the stability of organic light-emitting devices (OLEDs). Devices with double protective layers showed a 25-fold increase in operational lifetime compared to those without any packaging layers. LiF has a low melting point and insulating characteristics and it can be adapted as both a protective layer and pre-encapsulation film. The newly developed UV glue has a fast curing time of only 6 s and can be directly spin-coated onto the surface of the LiF passivation layer. The LiF thin film plus spin-coated UV glue is a simple packaging method that reduces the fabrication costs of OLEDs.

Synthesis of improved phenolic resins

NASA Technical Reports Server (NTRS)

Delano, C. B.; Mcleod, A. H.

1979-01-01

Twenty seven addition cured phenolic resin compositions were prepared and tested for their ability to give char residues comparable to state-of-the-art phenolic resins. Cyanate, epoxy, allyl, acrylate, methacrylate and ethynyl derivatized phenolic oligomers were investigated. The novolac-cyanate and propargyl-novolac resins provided anaerobic char yields at 800 C of 58 percent. A 59 percent char yield was obtained from modified epoxy novolacs. A phosphonitrilic derivative was found to be effective as an additive for increasing char yields. The novolac-cyanate, epoxy-novolac and methacrylate-epoxy-novolac systems were investigated as composite matrices with Thornel 300 graphite fiber. All three resins showed good potential as composite matrices. The free radical cured methacrylate-epoxy-novolac graphite composite provided short beam shear strengths at room temperature of 93.3 MPa (13.5 ksi). The novolac-cyanate graphite composite produced a short beam shear strength of 74 MPa (10.7 ksi) and flexural strength of 1302 MPa (189 ksi) at 177 C. Air heat aging of the novolac-cyanate and epoxy novolac based composites for 12 weeks at 204 C showed good property retention.

Dismantlable Thermosetting Adhesives Composed of a Cross-Linkable Poly(olefin sulfone) with a Photobase Generator.

PubMed

Sasaki, Takeo; Hashimoto, Shouta; Nogami, Nana; Sugiyama, Yuichi; Mori, Madoka; Naka, Yumiko; Le, Khoa V

2016-03-02

A novel photodetachable adhesive was prepared using a photodepolymerizable cross-linked poly(olefin sulfone). A mixture of a cross-linkable poly(olefin sulfone), a cross-linking reagent, and a photobase generator functioned as a thermosetting adhesive and exhibited high adhesive strength on quartz plates comparable to that obtained for commercially available epoxy adhesives. The cured resin was stable in the absence of UV light irradiation but completely lost its adhesive strength upon exposure of glued quartz plates to UV light in conjunction with heating to 100 °C.

Self-assembly of block copolymers for the fabrication of functional nanomaterials

NASA Astrophysics Data System (ADS)

Yao, Li

This dissertation explores the use of block copolymers which can self-assemble into different morphologies as templates to fabricate nanostructured materials. The first section (Chapters 2-4) reports the formation of mesoporous silica films with spherical, cylindrical and bicontinuous pores up to 40 nm in diameter through replicating the morphologies of the solid block copolymer (BCP) templates, polystyrene-b-poly(tert-butyl acrylate) (PS-b-PtBA), via phase selective condensation of tetraethylorthosilicate in supercritical CO2. Next, directed self-assembly was used to control the orientation of cylindrical domains in PS- b-PtBA templates. Large-area aligned mesochannels in silica films with diameters tunable between 5 and 30 nm were achieved through the replication of oriented templates via scCO2 infusion. The long-range alignment of mesochannels was confirmed through GISAXS with sample stage azimuthal rotation. In the second section (Chapters 5-6), enantiopure tartaric acid was used as an additive to dramatically improve ordering in poly(ethylene oxide-block- tert-butyl acrylate) (PEO-b-PtBA) copolymers. Transmission electron microscopy (TEM), atomic force microscopy (AFM) and X-ray scattering were used to study the phase behavior and morphologies within both bulk and thin films. With the addition of a photo acid generator, photo-induced disorder in the PEO-b-PtBA/tartaric acid composite system was achieved upon UV exposure which deprotected the PtBA block to yield poly(acrylic acid) (PAA), which is phase-miscible with PEO. Area-selective UV exposure using a photo-mask was applied with the assistance of trace amounts of base quencher to achieve high-resolution hierarchical patterns. Helical superstructures were observed by TEM in this BCP/chiral additive system with 3D handedness confirmed by TEM tomography. In the last section (Chapter 7), ultra-high loadings of nanoparticles into target domains of block copolymer composites were achieved by blending the block copolymer hosts with small molecule additives that exhibit strong interactions with one of the polymer chain segments and with the nanoparticle ligands via hydrogen bonding. The addition of 40 wt% D-tartaric acid to poly(ethylene oxide-block-tert-butyl acrylate) (PEO-b-PtBA) enabled the loading of up to 150 wt% of 4-hydroxythiophenol functionalized Au nanoparticles relative to the mass of the target hydrophilic domain. This was equivalent to over 40% Au by mass of the resulting well ordered composite as measured by thermal gravimetric analysis.

Tensile strength of glass fiber posts submitted to different surface treatments.

PubMed

Faria, Maria Isabel A; Gomes, Érica Alves; Messias, Danielle Cristine; Silva Filho, João Manoel; Souza Filho, Celso Bernardo; Paulino, Silvana Maria

2013-01-01

The aim of this in vitro study was to evaluate the tensile strength of glass fiber posts submitted to different surface treatments. Forty-eight maxillary canines had their crowns sectioned and root canals endodontically treated. The roots were embedded in acrylic resin and distributed into 3 groups according to the surface treatment: Group I: the posts were treated with silane agent for 30 s and adhesive; Group II: the posts were cleaned with alcohol before treatment with silane agent and adhesive; Group III: the posts were submitted to conditioning with 37% phosphoric acid for 30 s before treatment with silane agent and adhesive. Each group was divided into 2 subgroups for adhesive polymerization or not before insertion into the canal: A - adhesive was not light cured and B - adhesive was light cured. All posts were cemented with Panavia F and the samples were subjected to tensile strength test in a universal testing machine at crosshead speed of 1 mm/min. Data were submitted to one-way ANOVA and Tukey's test at 5% significance level. There was statistically significant difference (p<0.01) only between group GIII-B and groups GI-A and GI-B. No significant difference was found among the other groups (p>0.05). It was concluded that the products used for cleaning the posts influenced the retention regardless of adhesive light curing.

Photocurable acrylic composition, and U. V. curing with development of U. V. absorber

DOEpatents

McKoy, V.B.; Gupta, A.

1992-08-25

In-situ development of an ultraviolet absorber is provided by a compound such as a hydroxy-phenyl-triazole containing a group which protects the absorber during actinically activated polymerization by light at first frequency. After polymerization the protective group is removed by actinic reaction at a second frequency lower than the first frequency. The protective group is formed by replacing the hydrogen of the hydroxyl group with an acyl group containing 1 to 3 carbon atoms or an acryloxy group of the formula shown in a figure where R[sup 1] is either an alkyl containing 1 to 6 carbon atoms or --CH[double bond]CH[sub 2]. 2 figs.

Puncture-Healing Thermoplastic Resin Carbon-Fiber-Reinforced Composites

NASA Technical Reports Server (NTRS)

Grimsley, Brian W. (Inventor); Gordon, Keith L. (Inventor); Cano, Roberto J. (Inventor); Czabaj, Michael W. (Inventor); Siochi, Emilie J. (Inventor)

2015-01-01

A composite comprising a combination of a self-healing polymer matrix and a carbon fiber reinforcement is described. In one embodiment, the matrix is a polybutadiene graft copolymer matrix, such as polybutadiene graft copolymer comprising poly(butadiene)-graft-poly(methyl acrylate-co-acrylonitrile). A method of fabricating the composite is also described, comprising the steps of manufacturing a pre-impregnated unidirectional carbon fiber preform by wetting a plurality of carbon fibers with a solution, the solution comprising a self-healing polymer and a solvent, and curing the preform. A method of repairing a structure made from the composite of the invention is described. A novel prepreg material used to manufacture the composite of the invention is described.

Puncture-Healing Thermoplastic Resin Carbon-Fiber Reinforced Composites

NASA Technical Reports Server (NTRS)

Gordon, Keith L. (Inventor); Siochi, Emilie J. (Inventor); Grimsley, Brian W. (Inventor); Cano, Roberto J. (Inventor); Czabaj, Michael W. (Inventor)

2017-01-01

A composite comprising a combination of a self-healing polymer matrix and a carbon fiber reinforcement is described. In one embodiment, the matrix is a polybutadiene graft copolymer matrix, such as polybutadiene graft copolymer comprising poly(butadiene)-graft-poly(methyl acrylate-co-acrylonitrile). A method of fabricating the composite is also described, comprising the steps of manufacturing a pre-impregnated unidirectional carbon fiber preform by wetting a plurality of carbon fibers with a solution, the solution comprising a self-healing polymer and a solvent, and curing the preform. A method of repairing a structure made from the composite of the invention is described. A novel prepreg material used to manufacture the composite of the invention is described.

UV solid state laser ablation of intraocular lenses

NASA Astrophysics Data System (ADS)

Apostolopoulos, A.; Lagiou, D. P.; Evangelatos, Ch.; Spyratou, E.; Bacharis, C.; Makropoulou, M.; Serafetinides, A. A.

2013-06-01

Commercially available intraocular lenses (IOLs) are manufactured from silicone and acrylic, both rigid (e.g. PMMA) and foldable (hydrophobic or hydrophilic acrylic biomaterials), behaving different mechanical and optical properties. Recently, the use of apodizing technology to design new diffractive-refractive multifocals improved the refractive outcome of these intraocular lenses, providing good distant and near vision. There is also a major ongoing effort to refine laser refractive surgery to correct other defects besides conventional refractive errors. Using phakic IOLs to treat high myopia potentially provides better predictability and optical quality than corneal-based refractive surgery. The aim of this work was to investigate the effect of laser ablation on IOL surface shaping, by drilling circular arrays of holes, with a homemade motorized rotation stage, and scattered holes on the polymer surface. In material science, the most popular lasers used for polymer machining are the UV lasers, and, therefore, we tried in this work the 3rd and the 5th harmonic of a Q-switched Nd:YAG laser (λ=355 nm and λ=213 nm respectively). The morphology of the ablated IOL surface was examined with a scanning electron microscope (SEM, Fei - Innova Nanoscope) at various laser parameters. Quantitative measurements were performed with a contact profilometer (Dektak-150), in which a mechanical stylus scanned across the surface of gold-coated IOLs (after SEM imaging) to measure variations in surface height and, finally, the ablation rates were also mathematically simulated for depicting the possible laser ablation mechanism(s). The experimental results and the theoretical modelling of UV laser interaction with polymeric IOLs are discussed in relation with the physical (optical, mechanical and thermal) properties of the material, in addition to laser radiation parameters (laser energy fluence, number of pulses). The qualitative aspects of laser ablation at λ=213 nm reveal a smooth optical surface on the intraocular lens with no irregularities, observed with other wavelengths.

Development of silane-hydrolysate binder for UV-resistant thermal control coatings

NASA Technical Reports Server (NTRS)

Patterson, W. J.

1981-01-01

Detailed characterizaton and formulation studies were performed on a methyltriakoxysilane hydrolysate as a binder for thermal control coatings. The binder was optimized by varying hydrolysis temperature, time, catalyst type, and water concentration. The candidate coating formulations, based on this binder with TiO2 pigment, were optimized via a detailed series of sprayed test panels that included the parameters of binder/pigment ratio, ethanol content, pigment particle size, coating thickness and cure conditions. A typical optimized coating was prepared by acetic acid catalyzed hydrolysis of methyltriethoxysilane with 3.25 mol-equivalents of water over a 24 hour period at room temperature. The resulting hydrolysate was directly mixed with pre-milled TiO2 (12 grams pigment/26 grams binder) to yield a sprayable consistency. Panels were sprayed to result in a nominal cure coating thickness of 2 mils. Cure was affected by air drying for 24 hr at room temperature plus 72 hr at 150 F. These coatings are typically extremely tough and abrasion-resistant, with an absorptance (alpha) of 0.20 and emittance (e) of 0.89. No significant coating damage was observed in the mandrel bend test, even after exposure to thermal cycling from -160 to 160 F. Vacuum exposure of the coatings for 930 hours at 1 equivalent UV sun resulted in no visible degradation and no significant increase in absorptance.

EVALUATION OF BARRIERS TO THE USE OF RADIATION CURED COATINGS IN WIDE-WEB FLEXOGRAPHIC PRINTING

EPA Science Inventory

The report gives results of a study to investigate and identify the technical, economic, and educational barriers to the use and implementation of radiation-curable coatings (primarily ultraviolet (UV) curable inks) in the wide-web flexographic printing industry. (NOTE: In suppor...

Formation of random and regular relief-phase structures on silver halide photographic emulsions by holographic methods

NASA Astrophysics Data System (ADS)

Ganzherli, N. M.; Gulyaev, S. N.; Gurin, A. S.; Kramushchenko, D. D.; Maurer, I. A.; Chernykh, D. F.

2009-07-01

The formation of diffusers and microlens rasters on silver halide emulsions by holographic methods is considered. Two techniques for converting amplitude holographic recording to relief-phase recording, selective curing and irradiation of the emulsion gelatin by short-wavelength UV radiation, are compared.

Curing potential of experimental resin composites with systematically varying amount of bioactive glass: Degree of conversion, light transmittance and depth of cure.

PubMed

Par, Matej; Spanovic, Nika; Bjelovucic, Ruza; Skenderovic, Hrvoje; Gamulin, Ozren; Tarle, Zrinka

2018-06-17

The aim of this work was to investigate the curing potential of an experimental resin composite series with the systematically varying amount of bioactive glass 45S5 by evaluating the degree of conversion, light transmittance and depth of cure. Resin composites based on a Bis-GMA/TEGDMA resin with a total filler load of 70 wt% and a variable amount of bioactive glass (0-40 wt%) were prepared. The photoinitiator system was camphorquinone and ethyl-4-(dimethylamino) benzoate. The degree of conversion and light transmittance were measured by Raman spectroscopy and UV-vis spectroscopy, respectively. The depth of cure was evaluated according to the classical ISO 4049 test. The initial introduction of bioactive glass into the experimental series diminished the light transmittance while the further increase in the bioactive glass amount up to 40 wt% caused minor variations with no clear trend. The curing potential of the experimental composites was similar to or better than that of commercial resin composites. However, unsilanized bioactive glass fillers demonstrated the tendency to diminish both the maximum attainable conversion and the curing efficiency at depth. Experimental composite materials containing bioactive glass showed a clinically acceptable degree of conversion and depth of cure. The degree of conversion and depth of cure were diminished by bioactive glass fillers in a dose-dependent manner, although light transmittance was similar among all of the experimental composites containing 5-40 wt% of bioactive glass. Reduced curing potential caused by the bioactive glass has possible consequences on mechanical properties and biocompatibility. Copyright © 2018 Elsevier Ltd. All rights reserved.

High performance printed oxide field-effect transistors processed using photonic curing

NASA Astrophysics Data System (ADS)

Garlapati, Suresh Kumar; Cadilha Marques, Gabriel; Gebauer, Julia Susanne; Dehm, Simone; Bruns, Michael; Winterer, Markus; Baradaran Tahoori, Mehdi; Aghassi-Hagmann, Jasmin; Hahn, Horst; Dasgupta, Subho

2018-06-01

Oxide semiconductors are highly promising candidates for the most awaited, next-generation electronics, namely, printed electronics. As a fabrication route for the solution-processed/printed oxide semiconductors, photonic curing is becoming increasingly popular, as compared to the conventional thermal curing method; the former offers numerous advantages over the latter, such as low process temperatures and short exposure time and thereby, high throughput compatibility. Here, using dissimilar photonic curing concepts (UV–visible light and UV-laser), we demonstrate facile fabrication of high performance In2O3 field-effect transistors (FETs). Beside the processing related issues (temperature, time etc.), the other known limitation of oxide electronics is the lack of high performance p-type semiconductors, which can be bypassed using unipolar logics from high mobility n-type semiconductors alone. Interestingly, here we have found that our chosen distinct photonic curing methods can offer a large variation in threshold voltage, when they are fabricated from the same precursor ink. Consequently, both depletion and enhancement-mode devices have been achieved which can be used as the pull-up and pull-down transistors in unipolar inverters. The present device fabrication recipe demonstrates fast processing of low operation voltage, high performance FETs with large threshold voltage tunability.

Hybrid AlGaN-SiC Avalanche Photodiode for Deep-UV Photon Detection

NASA Technical Reports Server (NTRS)

Aslam, Shahid; Herrero, Federico A.; Sigwarth, John; Goldsman, Neil; Akturk, Akin

2010-01-01

The proposed device is capable of counting ultraviolet (UV) photons, is compatible for inclusion into space instruments, and has applications as deep- UV detectors for calibration systems, curing systems, and crack detection. The device is based on a Separate Absorption and Charge Multiplication (SACM) structure. It is based on aluminum gallium nitride (AlGaN) absorber on a silicon carbide APD (avalanche photodiode). The AlGaN layer absorbs incident UV photons and injects photogenerated carriers into an underlying SiC APD that is operated in Geiger mode and provides current multiplication via avalanche breakdown. The solid-state detector is capable of sensing 100-to-365-nanometer wavelength radiation at a flux level as low as 6 photons/pixel/s. Advantages include, visible-light blindness, operation in harsh environments (e.g., high temperatures), deep-UV detection response, high gain, and Geiger mode operation at low voltage. Furthermore, the device can also be designed in array formats, e.g., linear arrays or 2D arrays (micropixels inside a superpixel).

Vertical misfit of laser-sintered and vacuum-cast implant-supported crown copings luted with definitive and temporary luting agents.

PubMed

Castillo-de-Oyagüe, Raquel; Sánchez-Turrión, Andrés; López-Lozano, José-Francisco; Albaladejo, Alberto; Torres-Lagares, Daniel; Montero, Javier; Suárez-García, Maria-Jesús

2012-07-01

This study aimed to evaluate the vertical discrepancy of implant-supported crown structures constructed with vacuum-casting and Direct Metal Laser Sintering (DMLS) technologies, and luted with different cement types. Crown copings were fabricated using: (1) direct metal laser sintered Co-Cr (LS); (2) vacuum-cast Co-Cr (CC); and (3) vacuum-cast Ti (CT). Frameworks were luted onto machined implant abutments under constant seating pressure. Each alloy group was randomly divided into 5 subgroups (n = 10 each) according to the cement system utilized: Subgroup 1 (KC) used resin-modified glass-ionomer Ketac Cem Plus; Subgroup 2 (PF) used Panavia F 2.0 dual-cure resin cement; Subgroup 3 (RXU) used RelyX Unicem 2 Automix self-adhesive dual-cure resin cement; Subgroup 4 (PIC) used acrylic/urethane-based temporary Premier Implant Cement; and Subgroup 5 (DT) used acrylic/urethane-based temporary DentoTemp cement. Vertical misfit was measured by scanning electron microscopy (SEM). Two-way ANOVA and Student-Newman-Keuls tests were run to investigate the effect of alloy/fabrication technique, and cement type on vertical misfit. The statistical significance was set at α = 0.05. The alloy/manufacturing technique and the luting cement affected the vertical discrepancy (p < 0.001). For each cement type, LS samples exhibited the best fit (p < 0.01) whereas CC and CT frames were statistically similar. Within each alloy group, PF and RXU provided comparably greater discrepancies than KC, PIC, and DT, which showed no differences. Laser sintering may be an alternative to vacuum-casting of base metals to obtain passive-fitting implant-supported crown copings. The best marginal adaptation corresponded to laser sintered structures luted with glass-ionomer KC, or temporary PIC or DT cements. The highest discrepancies were recorded for Co-Cr and Ti cast frameworks bonded with PF or RXU resinous agents. All groups were within the clinically acceptable misfit range.

Control and reduction of peak temperature in self-curing resins.

PubMed

Schiavetti, R; DE Vico, G; Casucci, A; Covello, F; Ottria, L; Sannino, G; Barlattani, A

2009-07-01

INTRODUCTION.: The aim of this experimental study was to reduce the exothermic reaction during curing of the resins to cold. The significant exotherm generated by the reaction of polymerization of the resin curing involves many clinical complications including the high risk of necrosis against tooth. MATERIAL AND METHODS.: They were used four different types of self curing resins all based on methyl methacrylate, Jet Kit, Major Dentin, Dura Lay, Temporary Cold. The reaction of polymerization of the resins was done in Teflon pans and was monitored by a thermocouple which recorded the highest level reached by each temperature resin with and without additive. The polymerization reaction took place for each resin in the presence of an essential oil, the terpinolene, which acted as a "chain transfer" and different temperatures were recorded. RESULTS.: Resins Dura Lay and Jet kit showed a reduction of very high temperature in the presence of terpinolene, with a statistically significant difference compared to the same reaction without terpinolene Major resin dentin in the presence of the additive has reduced by 8.4°C peak temperature. Resin Temporary Cold has showed benefits with respect to peak temperature, but the reaction was much more 'consistent presence of the additive. DISCUSSION.: The system through which the chain transfer acts to lower the temperature of the reaction is that of chain transfer. Namely that interfere with the reaction of the polymer chains, by transferring these acrylic radicals are no longer active, ie, no longer able to bind to other monomer units, thus avoiding the excessive growth of macromolecules which are those that determine the temperature rise. This leads to the formation of more polymer chains with lower molecular weight.

Stereolithography of perfluoropolyethers for the microfabrication of robust omniphobic surfaces

NASA Astrophysics Data System (ADS)

Credi, Caterina; Levi, Marinella; Turri, Stefano; Simeone, Giovanni

2017-05-01

In this work, we provide a simple and straightforward method for the fabrication of stable highly hydrophobic and oleophobic surfaces by applying stereolithography (SL) to perfluoropolyethers (PFPEs). Inspired by the liquid repellency widely shown in nature, our approach enables to easily mimic the interplay between the chemistry and physics by microtexturing low surface tension PFPEs. To this end, UV-curable resins suitable for SL-processing were formulated by blending multifunctional (meth-)acrylates PFPEs oligomers with photoinitiator and visible dyes whose content was tuned to tailor resin SL sensitivities. Photocalorimetric studies were also performed to investigate the curing behavior of the different formulations upon SL light exposure. Being the first example of stereolithography applied to PFPEs, stereolithographic processability of new developed PFPEs photopolymer was compared with a standard photoresist taken as benchmark (DL260®). Optimized formulations were characterized by reduced laser penetration depth (<75 μm) and small critical energies thus enabling for fast printing of micrometric structures. Arrays of cylindrical pillars (85 μm diameter, 400 μm height) characterized by varied pillars spacing (200 ÷ 350 μm) were rapidly printed with high fidelity as attested by SEM examination. Contact angle measurements in static and dynamic conditions were performed to investigate the surface properties of textured samples using water and oil as the probing liquids. PFPEs liquid repellent performances were compared with those from DL260® textured surfaces arrayed by SL. High water contact angles coupled with low hysteresis asserted that high hydrophobic surfaces were successfully obtained and best-performing textured surfaces were also characterized by high oil repellency. Finally, this study demonstrated that omniphobic surfaces can be easily realized via a single-step, cost-effective, and time-saving process.

Engineering topochemical polymerizations using block copolymer templates.

PubMed

Zhu, Liangliang; Tran, Helen; Beyer, Frederick L; Walck, Scott D; Li, Xin; Agren, Hans; Killops, Kato L; Campos, Luis M

2014-09-24

With the aim to achieve rapid and efficient topochemical polymerizations in the solid state, via solution-based processing of thin films, we report the integration of a diphenyldiacetylene monomer and a poly(styrene-b-acrylic acid) block copolymer template for the generation of supramolecular architectural photopolymerizable materials. This strategy takes advantage of non-covalent interactions to template a topochemical photopolymerization that yields a polydiphenyldiacetylene (PDPDA) derivative. In thin films, it was found that hierarchical self-assembly of the diacetylene monomers by microphase segregation of the block copolymer template enhances the topochemical photopolymerization, which is complete within a 20 s exposure to UV light. Moreover, UV-active cross-linkable groups were incorporated within the block copolymer template to create micropatterns of PDPDA by photolithography, in the same step as the polymerization reaction. The materials design and processing may find potential uses in the microfabrication of sensors and other important areas that benefit from solution-based processing of flexible conjugated materials.

Resonance Raman and UV-visible spectroscopy of black dyes on textiles.

PubMed

Abbott, Laurence C; Batchelor, Stephen N; Smith, John R Lindsay; Moore, John N

2010-10-10

Resonance Raman and UV-visible diffuse reflectance spectra were recorded from samples of cotton, viscose, polyester, nylon, and acrylic textile swatches dyed black with one of seven single dyes, a mixture of two dyes, or one of seven mixtures of three dyes. The samples generally gave characteristic Raman spectra of the dyes, demonstrating that the technique is applicable for the forensic analysis of dyed black textiles. Survey studies of the widely used dye Reactive Black 5 show that essentially the same Raman spectrum is obtained on bulk sampling from the dye in solution, on viscose, on cotton at different uptakes, and on microscope sampling from the dye in cotton threads and single fibres. The effects of laser irradiation on the Raman bands and emission backgrounds from textile samples with and without dye are also reported. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

Development of flow systems by direct-milling on poly(methyl methacrylate) substrates using UV-photopolymerization as sealing process.

PubMed

Rodrigues, Eunice R G O; Lapa, Rui A S

2009-03-01

An alternative process for the design and construction of fluidic devices is presented. Several sealing processes were studied, as well as the hydrodynamic characteristics of the proposed fluidic devices. Manifolds were imprinted on polymeric substrates by direct-write milling, according to Computer Assisted Design (CAD) data. Poly(methyl methacrylate) (PMMA) was used as substrate due to its physical and chemical properties. Different bonding approaches for the imprinted channels were evaluated and UV-photopolymerization of acrylic acid (AA) was selected. The hydrodynamic characteristics of the proposed flow devices were assessed and compared to those obtained in similar flow systems using PTFE reactors and micro-pumps as propulsion units (multi-pumping approach). The applicability of the imprinted reactors was evaluated in the sequential determination of calcium and magnesium in water samples. Results obtained were in good agreement with those obtained by the reference procedure.

Low voltage polymer network liquid crystal for infrared spatial light modulators.

PubMed

Peng, Fenglin; Xu, Daming; Chen, Haiwei; Wu, Shin-Tson

2015-02-09

We report a low-voltage and fast-response polymer network liquid crystal (PNLC) infrared phase modulator. To optimize device performance, we propose a physical model to understand the curing temperature effect on average domain size. Good agreement between model and experiment is obtained. By optimizing the UV curing temperature and employing a large dielectric anisotropy LC host, we have lowered the 2π phase change voltage to 22.8V at 1.55μm wavelength while keeping response time at about 1 ms. Widespread application of such a PNLC integrated into a high resolution liquid-crystal-on-silicon (LCoS) for infrared spatial light modulator is foreseeable.

Variables that affect the mechanism of drug release from osmotic pumps coated with acrylate/methacrylate copolymer latexes.

PubMed

Jensen, J L; Appel, L E; Clair, J H; Zentner, G M

1995-05-01

The feasibility of using modified Eudragit acrylic latexes as microporous coatings for osmotic devices was investigated. Potassium chloride tablets were coated with mixtures of Eudragit RS30D and RL30D acrylic latexes that also contained a plasticizer (triethyl citrate or acetyl tributyl citrate) and a pore-forming agent (urea). A 2(5-1) fractional factorial experimental design was employed to determine the effect of five formulation variables (RS30D:RL30D polymer ratio plasticizer type, plasticizer level, urea level, and cure) on the in vitro release rate of KCl in deionized water (di water), lag time, and coat burst strength. The RS30D:RL30D polymer ratio had the greatest effect on the release rate, and both lag time and burst strength were most affected by the urea level. Statistical optimization was performed, and a coat formulation with predicted desirable in vitro performance was prepared and tested. The in vitro release rate (di water), lag time, and coat burst strength agreed well with the prediction. Dissolutions were also performed in phosphate buffered saline (PBS; pH 7.4); several formulations released markedly slower in PBS than in di water. This discrepancy was dependent on the type of plasticizer and the amount of pore former. Only those coat formulations containing acetyl tributyl citrate as the plasticizer and a 100% urea [(g urea/g polymer solids) x 100] level exhibited similar release rates in di water and PBS. The mechanism of release from these devices was primarily osmotic, whereas the release from devices coated with a formulation containing triethyl citrate and 50% urea was not dependent on the osmotic pressure difference. Devices with an osmotic release mechanism behaved similarly in vivo and in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

Porosity, water sorption and solubility of denture base acrylic resins polymerized conventionally or in microwave.

PubMed

Figuerôa, Rosana Marques Silva; Conterno, Bruna; Arrais, César Augusto Galvão; Sugio, Carolina Yoshi Campos; Urban, Vanessa Migliorini; Neppelenbroek, Karin Hermana

2018-01-01

The proper selection of polymerization cycle is important to prevent overheating of the monomer that could cause degradation, porosity and, consequently, deleterious effects on the denture base properties. Objective This study evaluated the porosity, water sorption and solubility of acrylic resins (Vipi Cril-VC and Vipi Wave-VW) after conventional or microwave polymerization cycles. Material and Methods Specimens (n = 10) were made and cured: 1-WB = 65°C during 90 min + boiling during 90 min (VC cycle - control group); 2-M25 = 10 min at 270 W + 5 min at 0 W + 10 min at 360 W (VW cycle); 3-M3 = 3 min at 550 W; and 4-M5 = 5 min at 650 W. Afterward, they were polished and dried in a dessicator until a constant mass was reached. Specimens were then immersed in distilled water at 37°C and weighed regularly until a constant mass was achieved. For porosity, an additional weight was made with the specimen immediately immersed in distilled water. For water sorption and solubility, the specimens were dried again until equilibrium was reached. Data were submitted to 2 way-ANOVA and Tukey HSD (α=0.05). Results Porosity mean values below 1.52% with no significant difference among groups for both materials were observed. Resins showed water sorption and solubility values without a significant difference. However, there was a significant difference among groups for these both properties (P<0.013). The highest sorption (2.43%) and solubility (0.13%) values were obtained for WB and M3, respectively. Conclusions The conventional acrylic resin could be polymerized in a microwave since both the materials showed similar performance in the evaluated properties. Shorter microwave cycles could be used for both the materials without any detectable increase in volume porosity.

Correction of nonuniformity error of Gafchromic EBT2 and EBT3.

PubMed

Katsuda, Toshizo; Gotanda, Rumi; Gotanda, Tatsuhiro; Akagawa, Takuya; Tanki, Nobuyoshi; Kuwano, Tadao; Yabunaka, Kouichi

2016-05-08

This study investigates an X-ray dose measurement method for computed tomography using Gafchromic films. Nonuniformity of the active layer is a major problem in Gafchromic films. In radiotherapy, nonuniformity error is reduced by applying the double-exposure technique, but this is impractical in diagnostic radiology because of the heel effect. Therefore, we propose replacing the X-rays in the double-exposure technique with ultraviolet (UV)-A irradiation of Gafchromic EBT2 and EBT3. To improve the reproducibility of the scan position, Gafchromic EBT2 and EBT3 films were attached to a 3-mm-thick acrylic plate. The samples were then irradiated with a 10 W UV-A fluorescent lamp placed at a distance of 72cm for 30, 60, and 90 minutes. The profile curves were evaluated along the long and short axes of the film center, and the standard deviations of the pixel values were calculated over large areas of the films. Paired t-test was performed. UV-A irradiation exerted a significant effect on Gafchromic EBT2 (paired t-test; p = 0.0275) but not on EBT3 (paired t-test; p = 0.2785). Similarly, the homogeneity was improved in Gafchromic EBT2 but not in EBT3. Therefore, the double-exposure technique under UV-A irradiation is suitable only for EBT2 films.

The effect of water uptake on the mechanical properties of low-k organosilicate glass

NASA Astrophysics Data System (ADS)

Guo, X.; Jakes, J. E.; Nichols, M. T.; Banna, S.; Nishi, Y.; Shohet, J. L.

2013-08-01

Water uptake in porous low-k dielectrics has become a significant challenge for both back-end-of-line integration and circuit reliability. The influence of absorbed water on the mechanical properties of plasma-enhanced chemical-vapor-deposited organosilicate glasses (SiCOH) was investigated with nanoindentation. The roles of physisorbed (α-bonded) and chemisorbed (β-bonded) water were examined separately through annealing at different temperatures. Nanoindentation measurements were performed on dehydrated organosilicate glass during exposure to varying humidity conditions. The elastic modulus and hardness for as-deposited SiCOH are intimately linked to the nature and concentration of the absorbed water in the dielectric. Under mild-annealing conditions, the water-related film mechanical property changes were shown to be reversible. The mechanical properties of UV-cured SiCOH were also shown to depend on absorbed water, but to a lesser extent because UV curing depopulates the hydrophilic chemical groups in SiCOH. High-load indentation tests showed that in-diffusion of water in the film/substrate interface can degrade the hardness of SiCOH/Si film stacks significantly, while not significantly changing the elastic modulus.

Removal of Pb(II) from aqueous solutions using waste textiles/poly(acrylic acid) composite synthesized by radical polymerization technique.

PubMed

Zhou, Tao; Xia, Fafa; Deng, Yue; Zhao, Youcai

2018-05-01

Waste textiles (WTs) are the inevitable outcome of human activity and should be separated and recycled in view of sustainable development. In this work, WT was modified through grafting with acrylic acid (AA) via radical polymerization process using ceric ammonium nitrate (CAN) as an initiator and microwave and/or UV irradiation as energy supply. The acrylic acid-grafted waste textiles (WT-g-AA) thus obtained was then used as an adsorbent to remove Pb(II) from Pb(II)-containing wastewater. The effects of pH, initial concentrations of Pb(II) and adsorbent dose were investigated, and around 95% Pb(II) can be removed from the aqueous solution containing 10mg/L at pH6.0-8.0. The experimental adsorption isotherm data was fitted to the Langmuir model with maximum adsorption capacity of 35.7mg Pb/g WT-g-AA. The Pb-absorbed WT-g-AA was stripped using dilute nitric acid solution and the adsorption capacity of Pb-free material decreased from 95.4% (cycle 1) to 91.1% (cycle 3). It was considered that the WT-g-AA adsorption for Pb(II) may be realized through the ion-exchange mechanism between COOH and Pb(II). The promising results manifested that WT-g-AA powder was an efficient, eco-friendly and reusable adsorbent for the removal of Pb(II) from wastewater. Copyright © 2017. Published by Elsevier B.V.

Combined experimental and theoretical studies on the molecular structures, spectroscopy, and inhibitor activity of 3-(2-thienyl)acrylic acid through AIM, NBO,FT-IR, FT-Raman, UV and HOMO-LUMO analyses, and molecular docking

NASA Astrophysics Data System (ADS)

Issaoui, N.; Ghalla, H.; Bardak, F.; Karabacak, M.; Aouled Dlala, N.; Flakus, H. T.; Oujia, B.

2017-02-01

In this work, the molecular structures and vibrational spectral analyses of 3-(2-Theinyl)acrylic acid (3-2TAA) monomer and dimer structures have been reported by using density functional theory calculations at B3LYP/6-311++G(d,p) level of theory. The complete assignments of the fundamental vibrational modes were obtained using potential energy distribution. Intermolecular interactions were analyzed by orbital NBO and topological AIM approaches. The electronic properties have been carried out using TD-DFT approach. Great agreements between experimental and theoretical values were achieved throughout the analysis of structural parameters and spectroscopic features. Inhibitor characteristics on human monoamine oxidase B (MAOB) enzyme of two determined stable conformers of 3-2TAA (β and γ) along with four selective inhibitors, namely safinamide, a coumarin analogue, farnesol, and phenyethylhydrazine were investigated via molecular docking. Moreover, molecular electrostatic potential (MEP) and temperature dependency of thermodynamic functions have been reported.

Starch-g-Poly-(N, N-dimethyl acrylamide-co-acrylic acid): an efficient Cr (VI) ion binder.

PubMed

Kolya, Haradhan; Roy, Anirban; Tripathy, Tridib

2015-01-01

Synthesis of Starch-g-(Poly N, N-dimethylacrylamide-co-acrylic acid) was carried out by solution polymerization technique using potassium perdisulfate (K(2)S(2)O(8)) as the initiator. The graft copolymer was characterized by measuring molecular weight, using size exclusion chromatography (SEC), FTIR spectroscopy and X-ray diffraction (XRD) studies. The synthetic graft copolymer was used for removal of hexavalent chromium ion [Cr (VI)] from its aqueous solution. Various operating variables affecting the metal sorption such as, the amount of adsorbent, solution pH, contact time, temperature and the Cr (VI) solution concentration were extensively investigated. FTIR and UV-VIS spectroscopy, cyclic voltammetry (CV) were employed to study the metal complexation. The adsorption data could be well described by the pseudo-second-order and Langmuir isotherm model which indicate a chemisorption process. Calculation of the various thermodynamic parameters for the adsorption was also done. The negative value of free energy change (ΔG°) indicates the spontaneous nature of the adsorption. Copyright © 2014 Elsevier B.V. All rights reserved.

Flexible Nonstick Replica Mold for Transfer Printing of Ag Ink.

PubMed

Lee, Bong Kuk; Yu, Han Young; Kim, Yarkyeon; Yoon, Yong Sun; Jang, Won Ik; Do, Lee-Mi; Park, Ji-Ho; Park, Jaehoon

2016-03-01

We report the fabrication of flexible replica molds for transfer printing of Ag ink on a rigid glass substrate. As mold precursors, acrylic mixtures were prepared from silsesquioxane-based materials, silicone acrylate, poly(propylene glycol) diacrylate, 3,3,4,4,5,5,6,6,7,7,8,8, 9,9,10,10,10-heptadecafluorodecyl methacrylate, and photoinitiator. By using these materials, the replica molds were fabricated from a silicon master onto a flexible substrate by means of UV-assisted molding process at room temperature. The wettability of Ag ink decreased with increase in the water contact angle of replica molds. On the other hand, the transfer rate of Ag ink onto adhesive-modified substrates increased with increase in the water contact angle of replica molds. Transferred patterns were found to be thermally stable on the photocurable adhesive layer, whereas Ag-ink patterns transferred on non-photocurable adhesives were distorted by thermal treatment. We believe that these characteristics of replica molds and adhesives offer a new strategy for the development of the transfer printing of solution-based ink materials.

Synthesis of poly acrylic acid modified silver nanoparticles and their antimicrobial activities.

PubMed

Ni, Zhihui; Wang, Zhihua; Sun, Lei; Li, Binjie; Zhao, Yanbao

2014-08-01

Poly acrylic acid modified silver (Ag/PAA) nanoparticles (NPs) have been successfully synthesized in the aqueous solution by using tannic acid as a reductant. The structure, morphology and composition of Ag/PAA NPs were characterized by various techniques such as X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible absorption spectroscopy (UV-vis) and thermogravimetry analysis (TGA). The results show that PAA/Ag NPs have a quasi-ball shape with an average diameter of 10 nm and exhibit well crystalline, and the reaction conditions have some effect on products morphology and size distribution. In addition, the as-synthesized Ag/PAA NPs antimicrobial activities against Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa) and Staphylococcus aureus (S. aureus) were evaluated by the methods of broth dilution, cup diffusion, optical density (OD600) and electron microscopy observation. The as-synthesized Ag/PAA NPs exhibit excellent antibacterial activity. The antimicrobial mechanism may be attributed to the damaging of bacterial cell membrane and causing leakage of cytoplasm. Copyright © 2014 Elsevier B.V. All rights reserved.

Impact of UV irradiation on multiwall carbon nanotubes in nanocomposites: formation of entangled surface layer and mechanisms of release resistance

PubMed Central

Nguyen, Tinh; Petersen, Elijah J.; Pellegrin, Bastien; Gorham, Justin M.; Lam, Thomas; Zhao, Minhua; Sung, Lipiin

2017-01-01

Multiwall carbon nanotubes (MWCNTs) are nanofillers used in consumer and structural polymeric products to enhance a variety of properties. Under weathering, the polymer matrix will degrade and the nanofillers may be released from the products potentially impacting ecological or human health. In this study, we investigated the degradation of a 0.72 % (by mass) MWCNT/amine-cured epoxy nanocomposite irradiated with high intensity ultraviolet (UV) light at various doses, the effects of UV exposure on the surface accumulation and potential release of MWCNTs, and possible mechanisms for the release resistance of the MWCNT surface layer formed on nanocomposites by UV irradiation. Irradiated samples were characterized for chemical degradation, mass loss, surface morphological changes, and MWCNT release using a variety of analytical techniques. Under 295 nm to 400 nm UV radiation up to a dose of 4865 MJ/m2, the nanocomposite matrix underwent photodegradation, resulting in formation of a dense, entangled MWCNT network structure on the surface. However, no MWCNT release was detected, even at very high UV doses, suggesting that the MWCNT surface layer formed from UV irradiation of polymer nanocomposites resist release. Four possible release resistance mechanisms of the UV-induced MWCNT surface layer are presented and discussed. PMID:28603293

Migration of DEHP and DINP into dust from PVC flooring products at different surface temperature.

PubMed

Jeon, Seunghwan; Kim, Ki-Tae; Choi, Kyungho

2016-03-15

Phthalates are important endocrine disrupting chemicals that have been linked to various adverse human health effects. Phthalates are ubiquitously present in indoor environment and could enter humans. Vinyl or PVC floorings have been recognized as one of important sources of phthalate release to indoor environment including house dust. In the present study, we estimated the migration of di(2-ethylhexyl)phthalate (DEHP) and di-isononyl phthalate (DINP) from the flooring materials into the dust under different heating conditions. For this purpose, a small chamber specifically designed for the present study and a Field and Laboratory Emission Cell (FLEC) were used, and four major types of PVC flooring samples including two UV curing paint coated, an uncoated residential, and a wax-coated commercial type were tested. Migration of DEHP was observed for an uncoated residential type and a wax-coated commercial type flooring. After 14 days of incubation, the levels of DEHP in the dust sample was determined at room temperature on average (standard deviation) at 384 ± 19 and 481 ± 53 μg/g, respectively. In contrast, migration of DINP was not observed. The migration of DEHP was strongly influenced by surface characteristics such as UV curing coating. In the residential flooring coated with UV curing paint, migration of DEHP was not observed at room temperature. But under the heated condition, the release of DEHP was observed in the dust in the FLEC. Migration of DEHP from flooring materials increased when the flooring was heated (50 °C). In Korea, heated flooring system, or 'ondol', is very common mode of heating in residential setting, therefore the contribution of PVC flooring to the total indoor DEHP exposure among general population is expected to be greater especially during winter season when the floor is heated. Copyright © 2015 Elsevier B.V. All rights reserved.

Soft-lithography fabrication of microfluidic features using thiol-ene formulations.

PubMed

Ashley, John F; Cramer, Neil B; Davis, Robert H; Bowman, Christopher N

2011-08-21

In this work, a novel thiol-ene based photopolymerizable resin formulation was shown to exhibit highly desirable characteristics, such as low cure time and the ability to overcome oxygen inhibition, for the photolithographic fabrication of microfluidic devices. The feature fidelity, as well as various aspects of the feature shape and quality, were assessed as functions of various resin attributes, particularly the exposure conditions, initiator concentration and inhibitor to initiator ratio. An optical technique was utilized to evaluate the feature fidelity as well as the feature shape and quality. These results were used to optimize the thiol-ene resin formulation to produce high fidelity, high aspect ratio features without significant reductions in feature quality. For structures with aspect ratios below 2, little difference (<3%) in feature quality was observed between thiol-ene and acrylate based formulations. However, at higher aspect ratios, the thiol-ene resin exhibited significantly improved feature quality. At an aspect ratio of 8, raised feature quality for the thiol-ene resin was dramatically better than that achieved by using the acrylate resin. The use of the thiol-ene based resin enabled fabrication of a pinched-flow microfluidic device that has complex channel geometry, small (50 μm) channel dimensions, and high aspect ratio (14) features. This journal is © The Royal Society of Chemistry 2011

Flexible barrier film, method of forming same, and organic electronic device including same

DOEpatents

Blizzard, John; Tonge, James Steven; Weidner, William Kenneth

2013-03-26

A flexible barrier film has a thickness of from greater than zero to less than 5,000 nanometers and a water vapor transmission rate of no more than 1.times.10.sup.-2 g/m.sup.2/day at 22.degree. C. and 47% relative humidity. The flexible barrier film is formed from a composition, which comprises a multi-functional acrylate. The composition further comprises the reaction product of an alkoxy-functional organometallic compound and an alkoxy-functional organosilicon compound. A method of forming the flexible barrier film includes the steps of disposing the composition on a substrate and curing the composition to form the flexible barrier film. The flexible barrier film may be utilized in organic electronic devices.

A Method for Direct Fabrication of a Lingual Splint for Management of Pediatric Mandibular Fractures

PubMed Central

Davies, Sarah; Costello, Bernard J.

2013-01-01

Summary: Pediatric mandibular fractures have successfully been managed in various ways. The use of a lingual splint is one such option. The typical indirect method for acrylic lingual splint fabrication involves obtaining dental impressions. Dental models are produced from those impressions so that model surgery may be performed. The splint is then made on those models using resin powder and liquid monomer in a wet laboratory and transferred to the patient. Obvious limitations to this technique exist for both patient and operator. We present a technique for direct, intraoperative, fabrication of a splint using commercially available light-cured material that avoids some of the shortcomings of the indirect method. Recommendations are made based on available material safety information. PMID:25289246

Nonlinear absorption enhancement of AuNPs based polymer nanocomposites

NASA Astrophysics Data System (ADS)

Zulina, Natalia A.; Baranov, Mikhail A.; Kniazev, Kirill I.; Kaliabin, Viacheslav O.; Denisyuk, Igor Yu.; Achor, Susan U.; Sitnikova, Vera E.

2018-07-01

Au nanoparticles (AuNPs) based polymer nanocomposites with high nonlinear absorption coefficient were synthesized by UV-photocuring. AuNPs were synthesized by laser ablation method in liquid monomer isodecyl acrylate (IDA). In this research, two colloids with 70 nm and 20 nm nanoparticles average sizes were studied. Size control was performed with SEM and STEM. Prepared nanomaterials exhibit strong third-order nonlinear optical responses under CW laser irradiation at 532 nm, which was estimated by using z-scan technique performed with open aperture. It was found experimentally that nonlinear absorption β is almost twice higher for nanocomposites with smaller AuNPs.

Effects of sterilization on optical and mechanical reliability of specialty optical fibers and terminations

NASA Astrophysics Data System (ADS)

Stolov, Andrei A.; Warych, Edward T.; Smith, William P.; Fournier, Paula L.; Hokansson, Adam S.; Li, Jie; Allen, R. Steve

2014-02-01

Optical fibers and terminations were subjected to different sterilization techniques, including multiple autoclaving and treatments with peracetic acid, E-beam and UV radiation. Effects of different sterilization techniques on key optical and mechanical properties of the fibers and the terminations were revealed. The primary attention was given to behavior of the coatings on the fibers and adhesives used in the terminations in harsh sterilization environments. The optical fibers with following four coating/buffer types were investigated: (i) dual acrylate, (ii) polyimide, (iii) silicone/PEEK and (iv) fluoroacrylate hard cladding/ETFE.

Fiber Optic Sensors for Cure/Health Monitoring of Composite Materials

NASA Technical Reports Server (NTRS)

Wood, K. H.; Brown, T. L.; Wu, M. C.; Gause, C. B.

2004-01-01

The objective of the current program is to develop techniques for using optical fibers to monitor the cure of composite materials in real time during manufacture and to monitor the in-service structural health of composite structures. Single and multimode optical fibers containing Bragg gratings have been used to perform Near Infrared (NIR) spectroscopy on high refractive index resins and show promise as embedded sensors. In order for chemical spectroscopy to be possible, intimate contact must be achieved between the fiber core and the composite resin. This contact is often achieved by stripping the cladding off of a portion of the fiber, thus making it brittle and easily broken in the composite processing environment. To avoid weakening the fiber to this extent, high refractive index fibers have been fabricated that use a low refractive index acrylate coating which serves as the cladding. This is ideal, as the coating is easily solvent stripped and intimate contact with the glass core can be achieved. Real time resin and composite chemical spectra have been obtained, with possible multifunctional capability using Bragg gratings to assess physical properties such as strain, modulus and other parameters of interest.

Modeling the free-radical polymerization of hexanediol diacrylate (HDDA): a molecular dynamics and graph theory approach.

PubMed

Torres-Knoop, Ariana; Kryven, Ivan; Schamboeck, Verena; Iedema, Piet D

2018-05-02

In the printing, coating and ink industries, photocurable systems are becoming increasingly popular and multi-functional acrylates are one of the most commonly used monomers due to their high reactivity (fast curing). In this paper, we use molecular dynamics and graph theory tools to investigate the thermo-mechanical properties and topology of hexanediol diacrylate (HDDA) polymer networks. The gel point was determined as the point where a giant component was formed. For the conditions of our simulations, we found the gel point to be around 0.18 bond conversion. A detailed analysis of the network topology showed, unexpectedly, that the flexibility of the HDDA molecules plays an important role in increasing the conversion of double bonds, while delaying the gel point. This is due to a back-biting type of reaction mechanism that promotes the formation of small cycles. The glass transition temperature for several degrees of curing was obtained from the change in the thermal expansion coefficient. For a bond conversion close to experimental values we obtained a glass transition temperature around 400 K. For the same bond conversion we estimate a Young's modulus of 3 GPa. Both of these values are in good agreement with experiments.

Influence of light intensity on surface free energy and dentin bond strength of core build-up resins.

PubMed

Shimizu, Y; Tsujimoto, A; Furuichi, T; Suzuki, T; Tsubota, K; Miyazaki, M; Platt, J A

2015-01-01

We examined the influence of light intensity on surface free energy characteristics and dentin bond strength of dual-cure direct core build-up resin systems. Two commercially available dual-cure direct core build-up resin systems, Clearfil DC Core Automix with Clearfil Bond SE One and UniFil Core EM with Self-Etching Bond, were studied. Bovine mandibular incisors were mounted in acrylic resin and the facial dentin surfaces were wet ground on 600-grit silicon carbide paper. Adhesives were applied to dentin surfaces and cured with light intensities of 0 (no irradiation), 200, 400, and 600 mW/cm(2). The surface free energy of the adhesives (five samples per group) was determined by measuring the contact angles of three test liquids placed on the cured adhesives. To determine the strength of the dentin bond, the core build-up resin pastes were condensed into the mold on the adhesive-treated dentin surfaces according to the methods described for the surface free energy measurement. The resin pastes were cured with the same light intensities as those used for the adhesives. Ten specimens per group were stored in water maintained at 37°C for 24 hours, after which they were shear tested at a crosshead speed of 1.0 mm/minute in a universal testing machine. Two-way analysis of variance (ANOVA) and a Tukey-Kramer test were performed, with the significance level set at 0.05. The surface free energies of the adhesive-treated dentin surfaces decreased with an increase in the light intensity of the curing unit. Two-way ANOVA revealed that the type of core build-up system and the light intensity significantly influence the bond strength, although there was no significant interaction between the two factors. The highest bond strengths were achieved when the resin pastes were cured with the strongest light intensity for all the core build-up systems. When polymerized with a light intensity of 200 mW/cm(2) or less, significantly lower bond strengths were observed. CONClUSIONS: The data suggest that the dentin bond strength of core build-up systems are still affected by the light intensity of the curing unit, which is based on the surface free energy of the adhesives. On the basis of the results and limitations of the test conditions used in this study, it appears that a light intensity of >400 mW/cm(2) may be required for achieving the optimal dentin bond strength.

Roles of Salmonella typhimurium umuDC and samAB in UV mutagenesis and UV sensitivity.

PubMed Central

Nohmi, T; Yamada, M; Watanabe, M; Murayama, S Y; Sofuni, T

1992-01-01

Expression of the umuDC operon is required for UV mutagenesis and most chemical mutagenesis in Escherichia coli. The closely related species Salmonella typhimurium has two sets of umuDC-like operons; the samAB operon is located in a 60-MDa cryptic plasmid, while the S. typhimurium umuDC (umuDCST) operon resides in a chromosome. The roles of these two umuDC-like operons in UV mutagenesis and UV sensitivity of S. typhimurium were investigated. A pBR322-derived plasmid carrying the samAB operon more efficiently restored UV mutability to a umuD44 strain and a umuC122::Tn5 strain of E. coli than a plasmid carrying the umuDCST operon did. When the umuDCST operon was specifically deleted from the chromosome of S. typhimurium TA2659, the resulting strain was not UV mutable and was more sensitive to the killing effect of UV irradiation than the parent strain was. Curing of the 60-MDa cryptic plasmid carrying the samAB operon did not influence the UV mutability of strain TA2659 but did increase its resistance to UV killing. A pSC101-derived plasmid carrying the samAB operon did not restore UV mutability to a umuD44 strain of E. coli, whereas pBR322- or pBluescript-derived plasmids carrying the samAB operon efficiently did restore UV mutability. We concluded that the umuDCST operon plays a major role in UV mutagenesis in S. typhimurium and that the ability of the samAB operon to promote UV mutagenesis is strongly affected by gene dosage. Possible reasons for the poor ability of samAB to promote UV mutagenesis when it is present on low-copy-number plasmids are discussed. Images PMID:1400244

Summary of Glue Tests 1993

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bell, D.; /Fermilab

1993-01-07

I have reported most of the results of my adhesive testing to members of the VLPC design team at one time or another, usually verbally, but I am wnnng this summary as an easy reference to the results I obtained. The adhesives I tested were for two primary purposes. The first was adhering optical fibers to Torlon 7130; the other was for securing an aluminum nitride substrate to the same material. I have not had access to a scanning electron microscope and someone with the knowledge to determine actual failure mechanisms, so the deductions I have made about why somemore » adhesives have worked well at low temperatures for some purposes and not for other applications while a different material never worked and another always worked are partially speculation. They should be taken merely at face value with no particular results 'carved in stone' so to speak. The first aspect of my testing was adhesion of optical fiber to torlon. Knowing that this is a very important joint, I tested a variety of glues of two primary types: acrylic and W cure. W cure adhesives are known to possess reasonably good properties at low temperatures and are quite convenient to use as long as a W source is available. The W cure adhesives I tested were: Loctite Utak 376 and also 7EN484(?), Master Bond 1 Component W 15-7, and Norland optical adhesive 61. I found them quite easy to use, and they were packaged in a way in which they were not likely to cause a mess. Lab 6 e Perimenters generally used the Loctite 376 optical cure adhesive in their research into connecting scintillating fibers to the standard type. The acrylics I tested were Loctite Speed Bonder 324 and Permabond Quick Bond 610. These worked reasonably well, but they require a considerably longer set time than the W cure adhesives and are more complicated to use. (5 minutes set time or so for the acrylics versus about 30 seconds for the W. The Loctite must have the activator applied about 5 minutes prior to the adhesive application and the Permabond must be mixed adequately.) I also used a cyanoacrylate ester (superglue type) adhesive which appeared to function adequately in this test, but I would not recommend it for extended use, and I am certain neither would anyone else. I would highly recommend using a W curing adhesive for this purpose if the adhesives and the W treatment can be determined to cause no damage to the fibers. There is no apparent physical damage, but transmission could potentially be damaged. The final optical fiber to torlon test that I did involved testing to see if individual fibers could hold the weight of the entire VlPC copper isotherm in the event that a small number of fibers shrink more than the others as the cryostat is cooled down. While this test was primarily for the purpose of testing the fibers themselves, I constructed a new sample to avoid breaking the others that had already been finished. The adhesive I used for this test was 3M 3535 BIA two part urethane adhesive. I had no problems whatsoever with this product, but like the other two part adhesives, it is considerably less convenient and more messy than the W curing adhesives. The short pot life of this adhesive was also a reason to avoid urethane, since mixing would be required frequently. The other portion of the adhesive testing for the VLPC that I performed was the adhesion of the substrate to the torlon used as a carrier. This bond is extremely small in practice, and I could not completely simulate the size and likely construction methods. I used larger pieces than those that will be bonded, but the primary goal of these tests was to test the performance of the adhesives. These tests contained harsher conditions of temperature changes and loadings than the substrates are likely to meet. By lightly loading the substrates before and after the cooling, it is possible to see if the cold temperatures had any effect on the adhesive-torlon interface, the adhesivesubstrate interface, or the adhesive itself. I tested about 10 adhesives intensely. In addition to these tests I also talked to people with about 20 different adhesive manufactures (maybe more) and Jay Hoffman, an adhesive expert here at the Lab. The general consensus from the. people that I spoke with is that the temperature range near liquid helium is very harsh and many adhesives that set quickly are not able to withstand these temperatures. Only one of the companies that I spoke with had any experience with temperatures that low (they made adhesives for space applications). I will go over each adhesive used in my testing. In addition, I will describe and speculate on the cause of any failures.« less

Development of high power UV irradiance meter calibration device

NASA Astrophysics Data System (ADS)

Xia, Ming; Gao, Jianqiang; Yin, Dejin; Li, Tiecheng

2016-09-01

With the rapid development of China's economy, many industries have more requirements for UV light applications, such as machinery manufacturing, aircraft manufacturing using high power UV light for detection, IT industry using high power UV light for curing component assembly, building materials, ink, paint and other industries using high power UV light for material aging test etc. In these industries, there are many measuring instruments for high power UV irradiance which are need to traceability. But these instruments are mostly imported instruments, these imported UV radiation meter are large range, wide wavelength range and high accuracy. They have exceeded our existing calibration capability. Expand the measuring range and improve the measurement accuracy of UV irradiance calibration device is a pressing matter of the moment. The newly developed high power UV irradiance calibration device is mainly composed of high power UV light, UV filter, condenser, UV light guide, optical alignment system, standard cavity absolute radiometer. The calibration device is using optical alignment system to form uniform light radiation field. The standard is standard cavity absolute radiometer, which can through the electrical substitution method, by means of adjusting and measuring the applied DC electric power at the receiver on a heating wire, which is equivalent to the thermo-electromotive force generated by the light radiation power, to achieve absolute optical radiation measurement. This method is the commonly used effective method for accurate measurement of light irradiation. The measuring range of calibration device is (0.2 200) mW/cm2, and the uncertainty of measurement results can reached 2.5% (k=2).

On-chip micropatterning of plastic (cylic olefin copolymer, COC) microfluidic channels for the fabrication of biomolecule microarrays using photografting methods.

PubMed

Pu, Qiaosheng; Oyesanya, Olufemi; Thompson, Bowlin; Liu, Shantang; Alvarez, Julio C

2007-01-30

This paper reports on the surface modification of plastic microfluidic channels to prepare different biomolecule micropatterns using ultraviolet (UV) photografting methods. The linkage chemistry is based upon UV photopolymerization of acryl monomers to generate thin films (0.01-6 microm) chemically linked to the organic backbone of the plastic surface. The commodity thermoplastic, cyclic olefin copolymer (COC) was selected to build microfluidic chips because of its significant UV transparency and easiness for microfabrication by molding techniques. Once the polyacrylic films were grafted on the COC surface using photomasks, micropatterns of proteins, DNA, and biotinlated conjugates were readily obtained by surface chemical reactions in one or two subsequent steps. The thickness of the photografted films can be tuned from several nanometers up to several micrometers, depending on the reaction conditions. The micropatterned films can be prepared inside the microfluidic channel (on-chip) or on open COC surfaces (off-chip) with densities of functional groups about 10(-7) mol/cm2. Characterization of these films was performed by attenuated-total-reflectance IR spectroscopy, fluorescence microscopy, profilometry, atomic force microscopy, and electrokinetic methods.

UV-Induced [2+2] Grafting-To Reactions for Polymer Modification of Cellulose.

PubMed

Conradi, Matthias; Ramakers, Gijs; Junkers, Thomas

2016-01-01

Benzaldehyde-functional cellulose paper sheets have been synthesized via tosylation of cellulose (Whatman No 5) followed by addition of p-hydroxy benzaldehyde. Via UV-induced Paterno-Büchi [2+2] cycloaddition reactions, these aldehyde functional surfaces are grafted with triallylcyanurate, trimethylolpropane allyl ether, and vinyl chloroacetate. In the following, allyl-functional polymers (poly(butyl acrylate), pBA, Mn = 6990 g mol(-1) , Đ = 1.12 and poly(N-isopropyl acrylamide), pNIPAAm, Mn = 9500 g mol(-1) , Đ = 1.16) synthesized via reversible addition fragmentation chain transfer polymerization are conjugated to the celloluse surface in a UV-induced grafting-to approach. With pBA, hydrophobic cellulose sheets are obtained (water contact angle 116°), while grafting of pNIPAAm allows for generation of "smart" surfaces, which are hydrophilic at room temperature, but that become hydrophobic when heated above the characteristic lower critical solution temperature (93° contact angle). The Paterno-Büchi reaction has been shown to be a versatile synthetic tool that also performs well in grafting-to approaches whereby its overall performance seems to be close to that of radical thiol-ene reactions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fabrication of 3D nano-structures using reverse imprint lithography

NASA Astrophysics Data System (ADS)

Han, Kang-Soo; Hong, Sung-Hoon; Kim, Kang-In; Cho, Joong-Yeon; Choi, Kyung-woo; Lee, Heon

2013-02-01

In spite of the fact that the fabrication process of three-dimensional nano-structures is complicated and expensive, it can be applied to a range of devices to increase their efficiency and sensitivity. Simple and inexpensive fabrication of three-dimensional nano-structures is necessary. In this study, reverse imprint lithography (RIL) with UV-curable benzylmethacrylate, methacryloxypropyl terminated poly-dimethylsiloxane (M-PDMS) resin and ZnO-nano-particle-dispersed resin was used to fabricate three-dimensional nano-structures. UV-curable resins were placed between a silicon stamp and a PVA transfer template, followed by a UV curing process. Then, the silicon stamp was detached and a 2D pattern layer was transferred to the substrate using diluted UV-curable glue. Consequently, three-dimensional nano-structures were formed by stacking the two-dimensional nano-patterned layers. RIL was applied to a light-emitting diode (LED) to evaluate the optical effects of a nano-patterned layer. As a result, the light extraction of the patterned LED was increased by about 12% compared to an unpatterned LED.

Fabrication of 3D nano-structures using reverse imprint lithography.

PubMed

Han, Kang-Soo; Hong, Sung-Hoon; Kim, Kang-In; Cho, Joong-Yeon; Choi, Kyung-Woo; Lee, Heon

2013-02-01

In spite of the fact that the fabrication process of three-dimensional nano-structures is complicated and expensive, it can be applied to a range of devices to increase their efficiency and sensitivity. Simple and inexpensive fabrication of three-dimensional nano-structures is necessary. In this study, reverse imprint lithography (RIL) with UV-curable benzylmethacrylate, methacryloxypropyl terminated poly-dimethylsiloxane (M-PDMS) resin and ZnO-nano-particle-dispersed resin was used to fabricate three-dimensional nano-structures.UV-curable resins were placed between a silicon stamp and a PVA transfer template, followed by a UV curing process. Then, the silicon stamp was detached and a 2D pattern layer was transferred to the substrate using diluted UV-curable glue. Consequently, three-dimensional nano-structures were formed by stacking the two-dimensional nano-patterned layers. RIL was applied to a light-emitting diode (LED) to evaluate the optical effects of a nano-patterned layer. As a result, the light extraction of the patterned LED was increased by about 12% compared to an unpatterned LED.

Different small, acid-soluble proteins of the alpha/beta type have interchangeable roles in the heat and UV radiation resistance of Bacillus subtilis spores.

PubMed Central

Mason, J M; Setlow, P

1987-01-01

Spores of Bacillus subtilis strains which carry deletion mutations in one gene (sspA) or two genes (sspA and sspB) which code for major alpha/beta-type small, acid-soluble spore proteins (SASP) are known to be much more sensitive to heat and UV radiation than wild-type spores. This heat- and UV-sensitive phenotype was cured completely or in part by introduction into these mutant strains of one or more copies of the sspA or sspB genes themselves; multiple copies of the B. subtilis sspD gene, which codes for a minor alpha/beta-type SASP; or multiple copies of the SASP-C gene, which codes for a major alpha/beta-type SASP of Bacillus megaterium. These findings suggest that alpha/beta-type SASP play interchangeable roles in the heat and UV radiation resistance of bacterial spores. Images PMID:3112127

Rapid fabrication method of a microneedle mold with controllable needle height and width.

PubMed

Lin, Yen-Heng; Lee, I-Chi; Hsu, Wei-Chieh; Hsu, Ching-Hong; Chang, Kai-Ping; Gao, Shao-Syuan

2016-10-01

The main issue of transdermal drug delivery is that macromolecular drugs cannot diffuse through the stratum corneum of skin. Many studies have pursued micro-sized needles encapsulated with drugs to overcome this problem, as these needles can pierce the stratum corneum and allow drugs to enter the circulatory system of the human body. However, most microneedle fabrication processes are time-consuming and require expensive equipment. In this study, we demonstrate a rapid method for fabricating a microneedle mold using drawing lithography and a UV-cured resin. The mold was filled with a water-soluble material, polyvinylpyrrolidone (PVP), which was then demolded to produce a water-soluble microneedle array. The results of an in vitro skin insertion test using PVP microneedles and pig ear skin demonstrated the feasibility of the microneedle mold. In addition, by controlling the viscosity of the UV-cured resin through various heat treatments, microneedles with different heights and aspect ratios were produced. Compared with other methods, this technology significantly simplifies and accelerates the mold fabrication process. In addition, the required equipment is relatively simple and inexpensive. Through this technology, we can rapidly fabricate microneedle molds with controllable dimensions for various applications.

A detailed experimental and theoretical investigation of the role of cyano groups in the π-bridged acceptor of sensitizers for use in dye-sensitized solar cells (DSCs).

PubMed

Xu, Qinqin; Yang, Guang; Ren, Yu; Lu, Futai; Zhang, Nuonuo; Qamar, Muhammad; Yang, Manlin; Zhang, Bao; Feng, Yaqing

2017-11-01

Three donor-π conjugated unit-acceptor (D-π-A) type zinc porphyrin sensitizers LX1, LX2 and LX3 bearing meso acrylic acid, α-cyanoacrylic acid, and α-cyanopentadienoic acid, respectively, as the π-bridged acceptors were designed and synthesized for use in dye-sensitized solar cells (DSCs). The interesting role of the cyano group attached to the α position of the acrylic and pentadienoic acid acceptor was investigated. It was shown that even though the introduction of the cyano group and the elongation of the π-bridge can both increase the light-harvesting as indicated by the UV-vis absorption spectra, the relevant cell performance dropped significantly. The photo to power conversion efficiencies (PCEs) of the devices increase in the order of LX1 > LX2 > LX3, with the highest PCE of 6.04% achieved for the LX1-based cell, which bears acrylic acid as the π-bridged acceptor. To further explore the effect of -CN and -CH[double bond, length as m-dash]CH- on the interaction between the absorbed dye and TiO 2 substrates, their density of states (DOS) and partial density of states (PDOS), as well as electronic properties were investigated in detail using theoretical calculations. The results suggest that introducing the -CN group into the acceptor and extending the conjugation of the π-bridge have decreased the LUMO levels of the dyes, leading to weak interfacial coupling, low electron injection driving force, low J sc , and thus poor cell performance.

Carbon Nanotube Composites from Modified Plant Oils

NASA Astrophysics Data System (ADS)

McAninch, Ian; Wool, Richard

2006-03-01

Carbon nanotubes (CNTs) with their impressive mechanical properties are ideal reinforcement material. Acrylated epoxidized soy oil (AESO) has been previously shown to have favorable interactions with carbon nanotubes. CNTs mixed into AESO, both with and without styrene as a co-monomer, using mechanical shear mixing showed dispersion only on the micron level, resulting in modest mechanical property improvements. Greater improvements were seen, especially in the rubbery modulus, when the resin's viscosity was kept high, either through a reduction of the styrene content, or by curing at a lower temperature. CNTs were also dispersed via sonication in methyl methacrylate. The resulting dispersion was then mixed with AESO. The resulting composites showed better CNT dispersion, with no micron-sized aggregates, as verified using SEM and optical microscopy. The mechanical properties also showed greater improvement.

Characterization and prediction of monomer-based dose rate effects in electron-beam polymerization

NASA Astrophysics Data System (ADS)

Schissel, Sage M.; Lapin, Stephen C.; Jessop, Julie L. P.

2017-12-01

Properties of some materials produced by electron-beam (EB) induced polymerization appear dependent upon the rate at which the initiating dose was delivered. However, the magnitude of these dose rate effects (DREs) can vary greatly with different monomer formulations, suggesting DREs are dependent on chemical structure. The relationship among dose, dose rate, conversion, and the glass transition temperature (Tg) of the cured material was explored for an acrylate monomer series. A strong correlation was determined between the DRE magnitude and monomer size, and this correlation may be attributed to chain transfer. Using the Tg shift caused by changes in dose, a preliminary predictive relationship was developed to estimate the magnitude of the Tg DRE, enabling scale-up of process variables for polymers prone to dose rate effects.

RSRM-13 (360Q013) ballistics mass properties flight designation STS-41

NASA Technical Reports Server (NTRS)

Laubacher, Brian A.; Richards, M. C.

1990-01-01

The propulsion performance and reconstructed mass properties data from Thiokol's RSRM-13 motors which were assigned to the STS-41 launch are presented. The SRM propellant, TP-H1148, is a composite type solid propellant, formulated of polybutadiene acrylic acid acryonitrile terpolymer binder, epoxy curing agent, ammonium perchlorate oxidizer, and aluminum powder fuel. A small amount of burning rate catalyst (iron oxide) was added to achieve the desired propellant burn rate. The propellant evaluation and raw material information are also presented. The presented ballistic performance was based on the Operational Flight Instrumentation. The adjustments made to the raw data on this flight include biasing the data to correct ambient pressure before liftoff. The performance from each motor as well as matched pair performance values were well within the CEI Specification requirements.

Overlay removable denture for treatment of worn teeth.

PubMed

Beyth, Nurit; Tamari, Israel; Buller Sharon, Anat

2014-01-01

Rehabilitation of partially edentulous patients with excessively worn dentitions can be challenging. Factors including medical history as well as the cost of the treatment and patient wishes for simpler approaches must be considered. This manuscript describes the use of an overlay partial denture to treat patients with excessive wear of the maxillary teeth. We describe a technique to restore severely worn teeth using heat-cured acrylic as part of a partial or full denture. Minimal preparations of the teeth are required, and the restoration provides protection from further wear, and stabilizes the occlusion. This solution was functionally and esthetically suitable to the patients. The technique can be used in medically complex patients where extractions are contraindicated, such as post radiation therapy or bisphosphonate treatment. © 2014 Special Care Dentistry Association and Wiley Periodicals, Inc.

Stratospheric experiments on curing of composite materials

NASA Astrophysics Data System (ADS)

Chudinov, Viacheslav; Kondyurin, Alexey; Svistkov, Alexander L.; Efremov, Denis; Demin, Anton; Terpugov, Viktor; Rusakov, Sergey

2016-07-01

Future space exploration requires a large light-weight structure for habitats, greenhouses, space bases, space factories and other constructions. A new approach enabling large-size constructions in space relies on the use of the technology of polymerization of fiber-filled composites with a curable polymer matrix applied in the free space environment on Erath orbit. In orbit, the material is exposed to high vacuum, dramatic temperature changes, plasma of free space due to cosmic rays, sun irradiation and atomic oxygen (in low Earth orbit), micrometeorite fluence, electric charging and microgravitation. The development of appropriate polymer matrix composites requires an understanding of the chemical processes of polymer matrix curing under the specific free space conditions to be encountered. The goal of the stratospheric flight experiment is an investigation of the effect of the stratospheric conditions on the uncured polymer matrix of the composite material. The unique combination of low residual pressure, high intensity UV radiation including short-wave UV component, cosmic rays and other aspects associated with solar irradiation strongly influences the chemical processes in polymeric materials. We have done the stratospheric flight experiments with uncured composites (prepreg). A balloon with payload equipped with heater, temperature/pressure/irradiation sensors, microprocessor, carrying the samples of uncured prepreg has been launched to stratosphere of 25-30 km altitude. After the flight, the samples have been tested with FTIR, gel-fraction, tensile test and DMA. The effect of cosmic radiation has been observed. The composite was successfully cured during the stratospheric flight. The study was supported by RFBR grants 12-08-00970 and 14-08-96011.

In situ Synthesis of Metal Nanoparticle Embedded Free Standing Multifunctional PDMS Films.

PubMed

Goyal, Anubha; Kumar, Ashavani; Patra, Prabir K; Mahendra, Shaily; Tabatabaei, Salomeh; Alvarez, Pedro J J; John, George; Ajayan, Pulickel M

2009-07-01

We demonstrate a simple one-step method for synthesizing noble metal nanoparticle embedded free standing polydimethylsiloxane (PDMS) composite films. The process involves preparing a homogenous mixture of metal salt (silver, gold and platinum), silicone elastomer and the curing agent (hardener) followed by curing. During the curing process, the hardener crosslinks the elastomer and simultaneously reduces the metal salt to form nanoparticles. This in situ method avoids the use of any external reducing agent/stabilizing agent and leads to a uniform distribution of nanoparticles in the PDMS matrix. The films were characterized using UV-Vis spectroscopy, transmission electron microscopy and X-ray photoemission spectroscopy. The nanoparticle-PDMS films have a higher Young's modulus than pure PDMS films and also show enhanced antibacterial properties. The metal nanoparticle-PDMS films could be used for a number of applications such as for catalysis, optical and biomedical devices and gas separation membranes. Copyright © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Holley, W.H. Jr.; Agro, S.C.; Galica, J.P.

The problem of browning in a number of EVA encapsulated flat plate photovoltaic modules has led to the questioning of EVA as a suitable material for such applications. By isolating the variables that could possibly lead to EVA browning, such as module construction, types of glass superstrates, additives, and processing conditions, the authors have been able to determine those significant specific variables that seem to have the most influence on discoloration.When standard-cure EVA-based laminates were exposed to accelerated UV aging, measurable yellowing of those laminates was evident after only one to two weeks exposure, and visual discoloration was observed aftermore » four to six weeks. Some samples yellowed quickly and some not at all, and there were significant differences in the rates of discoloration between standard-cure and fast-cure EVA. This paper looks at the results of these studies, especially focusing on the effect of additives in the EVA on the rate of yellowing, and discusses how preliminary results can be used to reformulate EVA encapsulants.« less

Determination of selected fate and aquatic toxicity characteristics of acrylic acid and a series of acrylic esters.

PubMed

Staples, C A; Murphy, S R; McLaughlin, J E; Leung, H W; Cascieri, T C; Farr, C H

2000-01-01

Acrylic acid, methyl acrylate, ethyl acrylate, and butyl acrylate are commercially important and widely used materials. This paper reports the results of a series of fate and aquatic toxicity studies. The mobility in soil of acrylic acid and its esters ranged from 'medium' to 'very high'. Calculated bioconcentration factors ranged from 1 to 37, suggesting a low bioconcentration potential. Acrylic acid and methyl acrylate showed limited biodegradability in the five day biochemical oxygen demand (BOD5) test, while ethyl acrylate and butyl acrylate were degraded easily (77% and 56%, respectively). Using the OECD method 301D 28-d closed bottle test, degradability for acrylic acid was 81% at 28 days, while the acrylic esters ranged from 57% to 60%. Acrylic acid degraded rapidly to carbon dioxide in soil (t1/2 < 1 day). Toxicity tests were conducted using freshwater and marine fish, invertebrates, and algae. Acrylic acid effect concentrations for fish and invertebrates ranged from 27 to 236 mg/l. Effect concentrations (LC50 or EC50) for fish and invertebrates using methyl acrylate, ethyl acrylate, and butyl acrylate ranged from 1.1 to 8.2 mg/l. The chronic MATC for acrylic acid with Daphnia magna was 27 mg/l based on length and young produced per adult reproduction day and for ethyl acrylate was 0.29 mg/l based on both the reproductive and growth endpoints. Overall these studies show that acrylic acid and the acrylic esters studied can rapidly biodegrade, have a low potential for persistence or bioaccumulation in the environment, and have low to moderate toxicity.

Dramatically improve the Safety Performance of Li ion Battery Separators and Reduce the Manufacturing Cost Using Ultraviolet Curing and High Precision Coating Technologies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Voelker, Gary; Arnold, John

The objective of this project was to improve the safety of operation of Lithium ion batteries (LIB)and at the same time significantly reduce the manufacturing cost of LIB separators. The project was very successful in demonstrating the improved performance and reduced cost attributed to using UV curable binder and high speed printing technology to place a very thin and precisely controlled ceramic layer on the surface of base separators made of polyolefins such as Polyethylene, Polypropylene and combinations of the two as well as cellulosic base separators. The underlying need for this new technology is the recently identified potential ofmore » fire in large format Lithium ion batteries used in hybrid, plug-in hybrid and electric vehicles. The primary potential cause of battery fire is thermal runaway caused by several different electrical or mechanical mechanisms; such as, overcharge, puncture, overheating, compaction, and internal short circuit. During thermal runaway, the ideal separator prevents ion flow and continues to physically separate the anode from the cathode. If the temperature of the battery gets higher, the separator may melt and partially clog the pores and help prevent ion flows but it also can shrink which can result in physical contact of the electrodes and accelerate thermal run-away even further. Ceramic coated separators eliminate many of the problems related to the usage of traditional separators. The ceramic coating provides an electrically insulating layer that retains its physical integrity at high temperature, allows for more efficient thermal heat transfer, helps reduce thermal shrinkage, and inhibits dendrite growth that could create a potential short circuit. The use of Ultraviolet (UV) chemistry to bind fine ceramic particles on separators is a unique and innovative approach primarily because of the instant curing of the UV curable binder upon exposure to UV light. This significant reduction in drying/curing time significantly reduces the cost of a ceramic coating. Another innovation is high precision, high speed, printing techniques that can apply a unique pattern of ceramic particles on base separators. The pattern will maximize ionic conductivity and minimize ceramic coating weight and thickness, while retaining the benefits of increased puncture strength, reduced thermal shrinkage and no decomposition. This project has met all of its goals and has been successfully completed. This successful completion has enabled Miltec UV to take the final steps leading to the commercialization of an innovative technology that will result in ceramic coated separators that can be manufactured and sold from the US, with increased production capacity, reduced cost, and improved battery safety.« less

Accelerated laboratory weathering of acrylic lens materials

NASA Astrophysics Data System (ADS)

Arndt, Thomas; Richter, Steffen; Kogler, René; Pasierb, Mike; Walby, Christopher

2015-09-01

Flat samples from various poly(methyl methacrylate) (PMMA) formulations were subjected to outdoor weathering in Arizona and Florida, EMMAQUA® accelerated outdoor weathering, and two accelerated laboratory weathering procedures at 3 Sun irradiance which, imitate dry (Arizona) and wet (Florida) conditions. The main mode of degradation is yellowing and not the generation of haze for any weathering procedure within the investigated radiant exposure. Higher UV absorber concentrations lead to smaller changes in optical properties and in the resulting relative concentrator photovoltaic (CPV) module efficiencies. Comparison of sample properties after various weathering procedures reveals that the influence of weathering factors other than radiant exposure depends on the sample as well.

Two decades of occupational (meth)acrylate patch test results and focus on isobornyl acrylate.

PubMed

Christoffers, Wietske A; Coenraads, Pieter-Jan; Schuttelaar, Marie-Louise A

2013-08-01

Acrylates constitute an important cause of occupational contact dermatitis. Isobornyl acrylate sensitization has been reported in only 2 cases. We encountered an industrial process operator with occupational contact dermatitis caused by isobornyl acrylate. (i) To investigate whether it is relevant to add isobornyl acrylate to the (meth)acrylate test series. (ii) To report patients with (meth)acrylate contact allergy at an occupational dermatology clinic. Our patch test database was screened for positive reactions to (meth)acrylates between 1993 and 2012. A selected group of 14 patients was tested with an isobornyl acrylate dilution series: 0.3%, 0.1%, 0.033%, and 0.01%. Readings were performed on D2, D3, and D7. One hundred and fifty-one patients were tested with our (meth)acrylate series; 24 had positive reactions. Most positive reactions were to 2-hydroxypropyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl methacrylate, and diethyleneglycol diacrylate. Hypothetical screening with 2-hydroxypropyl acrylate, ethyleneglycol dimethacrylate, ethoxylated bisphenol A glycol dimethacrylate and trimethylolpropane triacrylate identified 91.7% of the 24 patients. No positive reactions were observed in 14 acrylate-positive patients tested with the isobornyl acrylate dilution series. The 0.3% isobornyl acrylate concentration induced irritant reactions in 3 patients. We report a rare case of allergic contact dermatitis caused by isobornyl acrylate. However, this study provides insufficient support for isobornyl acrylate to be added to a (meth)acrylate series. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Microencapsulation of 2-octylcyanoacrylate tissue adhesive for self-healing acrylic bone cement.

PubMed

Brochu, Alice B W; Chyan, William J; Reichert, William M

2012-10-01

Here, we report the first phase of developing self-healing acrylic bone cement: the preparation and characterization of polyurethane (PUR) microcapsules containing a medical cyanoacrylate tissue adhesive. Capsules were prepared by interfacial polymerization of a toluene-2,4-diisocyanate-based polyurethane prepolymer with 1,4-butanediol to encapsulate 2-octylcyanoacrylate (OCA). Various capsule characteristics, including: resultant morphology, average size and size distribution, shell thickness, content and reactivity of encapsulated agent, and shelf life are investigated and their reliance on solvent type and amount, surfactant type and amount, temperature, pH, agitation rate, reaction time, and mode of addition of the oil phase to the aqueous phase are presented. Capsules had average diameters ranging from 74 to 222 μm and average shell thicknesses ranging from 1.5 to 6 μm. The capsule content was determined via thermogravimetric analysis and subsequent analysis of the capsules following up to 8 weeks storage revealed minimal loss of core contents. Mechanical testing of OCA-containing capsules showed individual capsules withstood compressive forces up to a few tenths of Newtons, and the contents released from crushed capsules generated tensile adhesive forces of a few Newtons. Capsules were successfully mixed into the poly(methyl methacrylate) bone cement, surviving the mixing process, exposure to methyl methacrylate monomer, and the resulting exothermic matrix curing. Copyright © 2012 Wiley Periodicals, Inc.

Optical X-ray density of composite resin luting agents.

PubMed

Carracho, Helena G; da Silveira, Ivori D; Soares, Clarissa G; Paranhos, Maria Paula G; Júnior, Luiz Henrique Burnett; Spohr, Ana Maria

2011-01-01

This study verified the optical density of four composite resin luting agents - RelyX ARC (RY), Enforce (E), C&B Cement (CB) and Flow it (FI), at thicknesses of 2, 3, and 4 mm. The optical density of the luting agents was compared with that of enamel and dentin at the same thicknesses. Fifteen tooth crowns were embedded in PVC cylinders with self-cured acrylic resin. In addition, acrylic resin was poured into 5 PVC cylinders and four equidistant 5 mm diameter holes were prepared, with one luting material inserted in each. A laboratory cutting machine was used to prepare 4-, 3- and 2-mm thick slices of the tooth crowns and materials. Digital images were obtained with a Digora system. Three radiographs of each thickness were obtained, totalizing 135 radiographs of the crowns and 45 of the materials. Three readings were carried out on each radiograph: three in enamel, three in dentin and three in each material, totalizing 1350. According to Students t-test (p

Characterization of photochemical-cured acrylates with calorimetric methods

NASA Astrophysics Data System (ADS)

Strehmel, Bernd; Anwand, Dirk; Wetzel, Henrik

1994-05-01

Radical polymerization kinetics of different kinds of diacrylates was investigated in linear polymers (binders) by using an isoperibolic calorimeter. For all experiments benzoin compounds were added as photoinitiator. The ester between acrylic acid and bisphenol-A-diglycidylether (DDGDA) and hexamethylenediacrylate were used as monomers. Both compounds have a high limiting conversion and a large polymerization rate in the binders investigated. Additionally, three kinds of termination reaction were observed: first order, second order, and primary radical termination. The last reaction was mainly found in the case of using the hexamethylenediacrylate monomer. The materials were investigated by DSC to determine the phase behavior. Both monomers form one phase with the binder (polymethylmethacrylate, PMMA). In contrast, a phase separation was observed between the crosslinked hexamethylenediacrylate and PMMA. Formations of semi- interpenetrating networks were found in the case of crosslinked DDGDA and PMMA. The glass transition temperatures were determined at different polymerization degrees also. The obtained results indicate that most of the network formation occurred in the glassy state. Fluorescence probe technique was applied to study changes in the mobility during network formation. The fluorescence probe crystal violet (CV) was used because this compound shows a strong free volume-dependent fluorescence. It was found that in the glassy state, where most of networks were formed, a large variation of the molecular mobility was observed during irradiation of the photopolymers. This result was in agreement with the observations during DSC experiments.

ShellFit: Reconstruction in the MiniCLEAN Detector

NASA Astrophysics Data System (ADS)

Seibert, Stanley

2010-02-01

The MiniCLEAN dark matter experiment is an ultra-low background liquid cryogen detector with a fiducial volume of approximately 150 kg. Dark matter candidate events produce ultraviolet scintillation light in argon at 128 nm and in neon at 80 nm. In order to detect this scintillation light, the target volume is enclosed by acrylic plates forming a spherical shell upon which an organic fluor, tetraphenyl butadiene (TPB), has been applied. TPB absorbs UV light and reemits visible light isotropically which can be detected by photomultiplier tubes. Two significant sources of background events in MiniCLEAN are decays of radon daughters embedded in the acrylic surface and external sources of neutrons, such as the photomultiplier tubes themselves. Both of these backgrounds can be mitigated by reconstructing the origin of the scintillation light and cutting events beyond a particular radius. The scrambling of photon trajectories at the TPB surface makes this task very challenging. The ``ShellFit'' algorithm for reconstructing event position and energy in a detector with a spherical wavelength-shifting shell will be described. The performance of ShellFit will be demonstrated using Monte Carlo simulation of several event types in the MiniCLEAN detector. )

Development and characterization of high refractive index and high scattering acrylate polymer layers

NASA Astrophysics Data System (ADS)

Eiselt, Thomas; Gomard, Guillaume; Preinfalk, Jan; Gleissner, Uwe; Lemmer, Uli; Hanemann, Thomas

2016-04-01

The aim is to develop a polymer layer which has the ability to diffuse light homogeneously and exhibit a high refractive index. The mixtures are containing an acrylate casting resin, benzylmethacrylate, phenanthrene and other additives. Phenanthrene is employed to increase the refractive index. The mixtures are first rheologically characterized and then polymerized with heat and UV radiation. For the refractive index measurements the polymerized samples require a planar surface without air bubbles. To produce flat samples a special construction consisting of a glass plate, a teflon sheet, a silicone ring (PDMS mold), another teflon sheet and another glass plate is developed. Glue clamps are used to fix this construction together. Selected samples have a refractive index of 1.585 at 20°C at a wavelength of 589nm. A master mixture with a high refractive index is taken for further experiments. Nano scaled titanium dioxide is added and dispersed into the master mixture and then spin coated on a glass substrate. These layers are optically characterized. The specular transmission and the overall transmission are measured to investigate the degree of scattering, which is defined as the haze. Most of the presented layers express the expected haze of over 50%.

Development and characterization of high refractive index and high scattering acrylate polymer layers

NASA Astrophysics Data System (ADS)

Eiselt, Thomas; Gomard, Guillaume; Preinfalk, Jan; Gleißner, Uwe; Lemmer, Uli; Hanemann, Thomas

2016-11-01

In this work, we develop a wet-processable scattering layer exhibiting a high refractive index that can be used in organic light-emitting diodes for light outcoupling purposes. The composite layers contain an acrylate casting resin, benzylmethacrylate, and phenanthrene, which is employed to increase the refractive index. The mixtures are first rheologically characterized and then polymerized with heat and UV radiation. For the refractive index measurements, the polymerized samples require a planar surface without air bubbles. To produce flat samples, a special construction consisting of a glass plate, a teflon sheet, a silicone ring (PDMS mold), another teflon sheet, and another glass plate is developed. Glue clamps are used to hold the construction together. The refractive index of the samples can be increased from 1.565 to 1.585 at 20°C at a wavelength of 589 nm following the addition of 20 wt% phenanthrene. A master mixture with a high refractive index is taken for further experiments. Nanoscaled titanium dioxide is added and dispersed into the master mixture and then spin coated on a glass substrate. These layers are optically characterized. Most of the presented layers present the expected haze of over 50%.

Controlled Transdermal Iontophoresis by Polypyrrole/Poly(Acrylic Acid) Hydrogel

NASA Astrophysics Data System (ADS)

Chansai, Phithupha; Sirivat, Anuvat

2008-03-01

Transdermal drug delivery system delivers a drug into a body at desired site and rate. The conductive polymer-hydrogel blend between polypyrrole (PPy) doped with anionic drug and poly(acrylic acid) (PAA) were developed as a matrix/carrier of drug for the transdermal drug delivery in which the characteristic releases depend on the electrical field applied. The PAA films and their blend films were prepared by solution casting using ethylene glycol dimethacrylate (EGDMA) as a crosslinking agent. A mechanical blending of PPy particles and PAA matrix was then carried out. Drug diffusions in the blended PPy/PAA hydrogel and the non-blended one were investigated and determined by using a modified Franz-diffusion cell with an acetate buffer, pH 5.5, at 37 0C, for a period of 48 hours to determine the effects of crosslinking ratio and electric field strength. Amounts of the released drug were measured by UV-Visible spectrophotometry. The diffusion coefficient of drug was determined through the Higuchi equation via different conditions, with and without an electric field. Moreover, thermal properties and electrical conductivity of the polypyrrole and drug-loaded polypyrrole were investigated by means of the thermogravimetric analysis and by using a two-point probe meter, respectively.

Radiolysis of poly(acrylic acid) in aqueous solution

NASA Astrophysics Data System (ADS)

Ulanski, Piotr; Bothe, Eberhard; Hildenbrand, Knut; Rosiak, Janusz M.; von Sonntag, Clemens

1995-02-01

Poly(acrylic acid), PAA, reacts with OH-radicals yielding -CHCH(CO 2H)- (β-radicals) and -CH 2C(CO 2H)- (α-radicals) in a ratio of approximately 2:1. This estimate is based on pulse radiolysis data where the absorption spectrum of the PAA-radicals was compared with the spectra of α-radicals from model systems. The β-radicals convert slowly into α-radicals ( k = 0.7 s -1 at pH 10). This process has also been observed by ESR. At PAA-concentrations of 10 -2 mol dm -3 chain scission dominates over other competing reactions except at low pH. The rate of chain scission was followed by pulse conductometry and in the pH range 7-9 k = 4 × 10 -2s -1 was observed. Oxygen reacts with PAA-radicals with k = 3.1 × 10 8 dm 3 mol -1 s -1 at pH 3.5 and k = 1.0 × 10 8 dm 3 mol -1 s -1 at pH 10. The corresponding peroxyl radicals undergo slow intramolecular H-transfer yielding a UV-absorbing product whose properties are that of 1,3-diketones.

[Study on the choice of functional monomer before preparation of myclobutanil molecularly imprinted polymer].

PubMed

Gao, Wen-Hui; Liu, Bo; Li, Xing-Feng; Han, Jun-Hua; Jia, Ying-Min

2014-03-01

To prepare myclobutanil molecularly imprinted polymer, a method was established for the choice of the appropriate functional monomer and its dosage. UV spectra was applied to study the combination form, the effect intensity, the optimal concentration ratio and the numbers of binding sites between myclobutanil and methyl acrylic acid (MAA) or acrylamide (AM) functional monomer. The results showed that hydrogen-bonding interaction could be formed between myclobutanil and methyl acrylic acid (MAA) or acrylamide (AM) functional monomer. The pi electron of the triazole ring conjugated double bond in my clobutanil could transit to pi* conjugate antibonding orbital when it absorbed energy. The formation of hydrogen bond could make pi-->pi* absorption band transit. Maximum absorption wavelength produced red shift with the increase in the functional monomer concentration in the system. The research revealed that the optimal concentration ratios between myclobutanil and the two monomers were c(M):c(MAA) = 1:4, c(M):c(AM) = 1:2. Myclobutanil and the both the functional monomers had the bonding ability, and strong bonding force. The prepared molecularly imprinted polymer using AM as a functional monomer had better stability and specificity of recognition for myclobutanil.

Preparation, properties and biological application of pH-sensitive poly(ethylene oxide) (PEO) hydrogels grafted with acrylic acid(AAc) using gamma-ray irradiation

NASA Astrophysics Data System (ADS)

Nho, Young Chang; Mook Lim, Youn; Moo Lee, Young

2004-09-01

pH-sensitive hydrogels were studied as a drug carrier for the protection of insulin from the acidic environment of the stomach before releasing it in the small intestine. In this study, hydrogels based on poly(ethylene oxide) (PEO) networks grafted with acrylic acid (AAc) were prepared via a two-step process. PEO hydrogels were prepared by γ-ray irradiation, and then grafting by AAc monomer onto the PEO hydrogels with the subsequent irradiation (radiation dose: 5-20 kGy, dose rate: 2.15 kGy/h). These grafted hydrogels showed a pH-sensitive swelling behavior. The grafted hydrogels were used as a carrier for the drug delivery systems for the controlled release of insulin. The in vitro drug release behaviors of these hydrogels were examined by quantification analysis with a UV/VIS spectrophotometer. Insulin was loaded into freeze-dried hydrogels (7 mm×3 mm×2.5 mm) and administrated orally to healthy and diabetic Wistar rats. The oral administration of insulin-loaded hydrogels to Wistar rats decreased the blood glucose levels obviously for at least 4 h due to the absorption of insulin in the gastrointestinal tract.

Maskless Lithography Using Negative Photoresist Material: Impact of UV Laser Intensity on the Cured Line Width

NASA Astrophysics Data System (ADS)

Mohammed, Mohammed Ziauddin; Mourad, Abdel-Hamid I.; Khashan, Saud A.

2018-06-01

The application of maskless lithography technique on negative photoresist material is investigated in this study. The equipment used in this work is designed and built especially for maskless lithography applications. The UV laser of 405 nm wavelength with 0.85 Numerical Aperture is selected for direct laser writing. All the samples are prepared on a glass substrate. Samples are tested at different UV laser intensities and different stage velocities in order to study the impact on patterned line width. Three cases of spin coated layers of thickness 90 μm, 40 μm, and 28 μm on the substrate are studied. The experimental results show that line width has a generally increasing trend with intensity. However, a decreasing trend was observed for increasing velocity. The overall performance shows that the mr-DWL material is suitable for direct laser writing systems.

Maskless Lithography Using Negative Photoresist Material: Impact of UV Laser Intensity on the Cured Line Width

NASA Astrophysics Data System (ADS)

Mohammed, Mohammed Ziauddin; Mourad, Abdel-Hamid I.; Khashan, Saud A.

2018-04-01

The application of maskless lithography technique on negative photoresist material is investigated in this study. The equipment used in this work is designed and built especially for maskless lithography applications. The UV laser of 405 nm wavelength with 0.85 Numerical Aperture is selected for direct laser writing. All the samples are prepared on a glass substrate. Samples are tested at different UV laser intensities and different stage velocities in order to study the impact on patterned line width. Three cases of spin coated layers of thickness 90 μm, 40 μm, and 28 μm on the substrate are studied. The experimental results show that line width has a generally increasing trend with intensity. However, a decreasing trend was observed for increasing velocity. The overall performance shows that the mr-DWL material is suitable for direct laser writing systems.

Rapid laser fabrication of microlens array using colorless liquid photopolymer for AMOLED devices

NASA Astrophysics Data System (ADS)

Kim, Kwang-Ryul; Jeong, Han-Wook; Lee, Kong-Soo; Yi, Junsin; Yoo, Jae-Chern; Cho, Myung-Woo; Cho, Sung-Hak; Choi, Byoungdeog

2011-01-01

Microlens array (MLA) is microfabricated using Ultra Violet (UV) laser for display device applications. A colorless liquid photopolymer, Norland Optical Adhesive (NOA) 60, is spin-coated and pre-cured via UV light for completing the laser process. The laser energy controlled by a galvano scanner is radiated on the surface of the NOA 60. A rapid thermal volume expansion inside the material creates microlens array when the Gaussian laser energy is absorbed. The fabrication process conditions for various shapes and densities of MLA using a non-contact surface profiler are investigated. Furthermore, we analyze the optical and display characteristics for the Organic Light Emitting Diode (OLED) devices. Optimized condition furnishes the OLED with the enhancement of light emission by 15%. We show that UV laser technique, which is installed with NOA 60 MLA layer, is eligible for improving the performance of the next generation display devices.

Vertical misfit of laser-sintered and vacuum-cast implant-supported crown copings luted with definitive and temporary luting agents

PubMed Central

Sánchez-Turrión, Andrés; López-Lozano, José F.; Albaladejo, Alberto; Torres-Lagares, Daniel; Montero, Javier; Suárez-García, Maria J.

2012-01-01

Objectives. This study aimed to evaluate the vertical discrepancy of implant-supported crown structures constructed with vacuum-casting and Direct Metal Laser Sintering (DMLS) technologies, and luted with different cement types. Study Design. Crown copings were fabricated using: (1) direct metal laser sintered Co-Cr (LS); (2) vacuum-cast Co-Cr (CC); and (3) vacuum-cast Ti (CT). Frameworks were luted onto machined implant abutments under constant seating pressure. Each alloy group was randomly divided into 5 subgroups (n = 10 each) according to the cement system utilized: Subgroup 1 (KC) used resin-modified glass-ionomer Ketac Cem Plus; Subgroup 2 (PF) used Panavia F 2.0 dual-cure resin cement; Subgroup 3 (RXU) used RelyX Unicem 2 Automix self-adhesive dual-cure resin cement; Subgroup 4 (PIC) used acrylic/urethane-based temporary Premier Implant Cement; and Subgroup 5 (DT) used acrylic/urethane-based temporary DentoTemp cement. Vertical misfit was measured by scanning electron microscopy (SEM). Two-way ANOVA and Student-Newman-Keuls tests were run to investigate the effect of alloy/fabrication technique, and cement type on vertical misfit. The statistical significance was set at α = 0.05. Results. The alloy/manufacturing technique and the luting cement affected the vertical discrepancy (p < 0.001). For each cement type, LS samples exhibited the best fit (p < 0.01) whereas CC and CT frames were statistically similar. Within each alloy group, PF and RXU provided comparably greater discrepancies than KC, PIC, and DT, which showed no differences. Conclusions. Laser sintering may be an alternative to vacuum-casting of base metals to obtain passive-fitting implant-supported crown copings. The best marginal adaptation corresponded to laser sintered structures luted with glass-ionomer KC, or temporary PIC or DT cements. The highest discrepancies were recorded for Co-Cr and Ti cast frameworks bonded with PF or RXU resinous agents. All groups were within the clinically acceptable misfit range. Key words:Dental alloy, laser sintering, implant-supported prostheses, vertical discrepancy, vertical misfit. PMID:22322524

Encapsulant materials and associated devices

DOEpatents

Kempe, Michael D [Littleton, CO; Thapa, Prem [Lima, OH

2011-03-08

Compositions suitable for use as encapsulants are described. The inventive compositions include a high molecular weight polymeric material, a curing agent, an inorganic compound, and a coupling agent. Optional elements include adhesion promoting agents, colorants, antioxidants, and UV absorbers. The compositions have desirable diffusivity properties, making them suitable for use in devices in which a substantial blocking of moisture ingress is desired, such as photovoltaic (PV) modules.

Encapsulant materials and associated devices

DOEpatents

Kempe, Michael D [Littleton, CO; Thapa, Prem [Lima, OH

2012-05-22

Compositions suitable for use as encapsulants are described. The inventive compositions include a high molecular weight polymeric material, a curing agent, an inorganic compound, and a coupling agent. Optional elements include adhesion promoting agents, colorants, antioxidants, and UV absorbers. The compositions have desirable diffusivity properties, making them suitable for use in devices in which a substantial blocking of moisture ingress is desired, such as photovoltaic (PV) modules.

Greyscale Photolithography for Multilayer PZT Microelectromechanical Systems (MEMS) Device Applications

DTIC Science & Technology

We present development of a process to perform greyscale photolithography on a 2.55-m thick photoresist in order to transfer tiered and sloped...platinum or iridium oxide (IrO2) electrodes above and below each layer. Process variables including resist rehydration , focus of the exposure, and UV cure...bake temperature were optimized to produce the best greyscale profile through the thickness of the resist.

Atomic Oxygen Durability Evaluation of a UV Curable Ceramer Protective Coating

NASA Technical Reports Server (NTRS)

Banks, Bruce A.; Karniotis, Christina A.; Dworak, David; Soucek, Mark

2004-01-01

The exposure of most silicones to atomic oxygen in low Earth orbit (LEO) results in the oxidative loss of methyl groups with a gradual conversion to oxides of silicon. Typically there is surface shrinkage of oxidized silicone protective coatings which leads to cracking of the partially oxidized brittle surface. Such cracks widen and branch crack with continued atomic oxygen exposure ultimately allowing atomic oxygen to reach any hydrocarbon polymers under the silicone coating. A need exists for a paintable silicone coating that is free from such surface cracking and can be effectively used for protection of polymers and composites in LEO. A new type of silicone based protective coating holding such potential was evaluated for atomic oxygen durability in an RF atomic oxygen plasma exposure facility. The coating consisted of a UV curable inorganic/organic hybrid coating, known as a ceramer, which was fabricated using a methyl substituted polysiloxane binder and nanophase silicon-oxo-clusters derived from sol-gel precursors. The polysiloxane was functionalized with a cycloaliphatic epoxide in order to be cured at ambient temperature via a cationic UV induced curing mechanism. Alkoxy silane groups were also grafted onto the polysiloxane chain, through hydrosilation, in order to form a network with the incorporated silicon-oxo-clusters. The prepared polymer was characterized by H-1 and Si-29 NMR, FT-IR, and electrospray ionization mass spectroscopy. The paper will present the results of atomic oxygen protection ability of thin ceramer coatings on Kapton H as evaluated over a range of atomic oxygen fluence levels.

Process margin enhancement for 0.25-μm metal etch process

NASA Astrophysics Data System (ADS)

Lee, Chung Y.; Ma, Wei Wen; Lim, Eng H.; Cheng, Alex T.; Joy, Raymond; Ross, Matthew F.; Wong, Selmer S.; Marlowe, Trey

2000-06-01

This study evaluates electron beam stabilization of UV6, a positive tone Deep-UV (DUV) resist from Shipley, for a 0.25 micrometer metal etch application. Results are compared between untreated resist and resist treated with different levels of electron beam stabilization. The electron beam processing was carried out in an ElectronCureTM flood electron beam exposure system from Honeywell International Inc., Electron Vision. The ElectronCureTM system utilizes a flood electron beam source which is larger in diameter than the substrate being processed, and is capable of variable energy so that the electron range is matched to the resist film thickness. Changes in the UV6 resist material as a result of the electron beam stabilization are monitored via spectroscopic ellipsometry for film thickness and index of refraction changes and FTIR for analysis of chemical changes. Thermal flow stability is evaluated by applying hot plate bakes of 150 degrees Celsius and 200 degrees Celsius, to patterned resist wafers with no treatment and with an electron beam dose level of 2000 (mu) C/cm2. A significant improvement in the thermal flow stability of the patterned UV6 resist features is achieved with the electron beam stabilization process. Etch process performance of the UV6 resist was evaluated by performing a metal pattern transfer process on wafers with untreated resist and comparing these with etch results on wafers with different levels of electron beam stabilization. The etch processing was carried out in an Applied Materials reactor with an etch chemistry including BCl3 and Cl2. All wafers were etched under the same conditions and the resist was treated after etch to prevent further erosion after etch but before SEM analysis. Post metal etch SEM cross-sections show the enhancement in etch resistance provided by the electron beam stabilization process. Enhanced process margin is achieved as a result of the improved etch resistance, and is observed in reduced resist side-wall angles after etch. Only a slight improvement is observed in the isolated to dense bias effects of the etch process. Improved CD control is also achieved by applying the electron beam process, as more consistent CDs are observed after etch.

A novel star-shaped poly(carboxylic acid) for resin-modified glass-ionomer restoratives.

PubMed

Weng, Y; Howard, L; Xie, D

2014-07-01

We have developed a novel glass-ionomer cement (GIC) system composed of photo-curable star-shaped poly(acrylic acid-co-itaconic acid)s. These polyacids were synthesized via a chain-transfer radical polymerization using a newly synthesized multi-arm chain-transfer agent. The star-shaped polyacids showed significantly lower viscosities in water as compared to the linear polyacids. Due to the lower viscosities, the molecular weight (MW) of the polyacids can be significantly increased for enhancing the mechanical strengths while keeping the ease of mixing and handling. The effects of MW, GM-tethering ratio, P/L ratio, and aging on the compressive properties of the experimental cements were significant. The light-cured experimental cements showed significantly improved mechanical strengths i.e. 49% in yield strength, 41% in modulus, 25% in CS, 20% in DTS, and 36% in FS, higher than commercial Fuji II LC. After aging in water for 1 month, the compressive strength of the novel light-cured experimental cement reached 343 MPa, which was 34% and 42% higher than Fuji II and Fuji II LC, respectively. This one-month aged experimental cement was also 23% higher than itself after one day aging, indicating that aging in water can significantly enhance salt-bridge formation for this novel star-shaped polyacid-comprised GIC.

The effect of air thinning on dentin adhesive bond strength.

PubMed

Hilton, T J; Schwartz, R S

1995-01-01

The purpose of this study was to determine if air thinning three dentin adhesives would affect bond strength to dentin. Ninety human molars were mounted in acrylic and the occlusal surfaces ground to expose a flat dentin surface. Thirty teeth were randomly assigned to one of the following dentin bonding agent/composite combinations: A) Universal Bond 3/TPH (Caulk), B) All-Bond 2/Bis-Fil-P (Bisco), and C) Scotchbond Multi-Purpose/Z-100 (3m). The primers were applied following the manufacturers' instructions. The adhesives were applied by two methods. A thin layer of adhesive was applied with a brush to 15 specimens in each group and light cured. Adhesive was brushed on to the remaining 15 teeth in the group, air thinned for 3 seconds, and then polymerized. The appropriate composite was applied in 2 mm increments and light cured utilizing a 5 mm-in-diameter split Teflon mold. Following 3 months of water storage, all groups were shear tested to failure on an Instron Universal Testing Machine. Bond strength was significantly higher in all groups when the dentin bonding agent was painted on without being air thinned. Scotchbond Multi-Purpose had significantly higher bond strength than All-Bond 2, which had significantly higher bond strength than Universal Bond 3.

Effect of copolymer latexes on physicomechanical properties of mortar containing high volume fly ash as a replacement material of cement.

PubMed

Negim, El-Sayed; Kozhamzharova, Latipa; Gulzhakhan, Yeligbayeva; Khatib, Jamal; Bekbayeva, Lyazzat; Williams, Craig

2014-01-01

This paper investigates the physicomechanical properties of mortar containing high volume of fly ash (FA) as partial replacement of cement in presence of copolymer latexes. Portland cement (PC) was partially replaced with 0, 10, 20, 30 50, and 60% FA. Copolymer latexes were used based on 2-hydroxyethyl acrylate (2-HEA) and 2-hydroxymethylacrylate (2-HEMA). Testing included workability, setting time, absorption, chemically combined water content, compressive strength, and scanning electron microscopy (SEM). The addition of FA to mortar as replacement of PC affected the physicomechanical properties of mortar. As the content of FA in the concrete increased, the setting times (initial and final) were elongated. The results obtained at 28 days of curing indicate that the maximum properties of mortar occur at around 30% FA. Beyond 30% FA the properties of mortar reduce and at 60% FA the properties of mortar are lower than those of the reference mortar without FA. However, the addition of polymer latexes into mortar containing FA improved most of the physicomechanical properties of mortar at all curing times. Compressive strength, combined water, and workability of mortar containing FA premixed with latexes are higher than those of mortar containing FA without latexes.

Effect of Copolymer Latexes on Physicomechanical Properties of Mortar Containing High Volume Fly Ash as a Replacement Material of Cement

PubMed Central

Kozhamzharova, Latipa; Gulzhakhan, Yeligbayeva; Bekbayeva, Lyazzat; Williams, Craig

2014-01-01

This paper investigates the physicomechanical properties of mortar containing high volume of fly ash (FA) as partial replacement of cement in presence of copolymer latexes. Portland cement (PC) was partially replaced with 0, 10, 20, 30 50, and 60% FA. Copolymer latexes were used based on 2-hydroxyethyl acrylate (2-HEA) and 2-hydroxymethylacrylate (2-HEMA). Testing included workability, setting time, absorption, chemically combined water content, compressive strength, and scanning electron microscopy (SEM). The addition of FA to mortar as replacement of PC affected the physicomechanical properties of mortar. As the content of FA in the concrete increased, the setting times (initial and final) were elongated. The results obtained at 28 days of curing indicate that the maximum properties of mortar occur at around 30% FA. Beyond 30% FA the properties of mortar reduce and at 60% FA the properties of mortar are lower than those of the reference mortar without FA. However, the addition of polymer latexes into mortar containing FA improved most of the physicomechanical properties of mortar at all curing times. Compressive strength, combined water, and workability of mortar containing FA premixed with latexes are higher than those of mortar containing FA without latexes. PMID:25254256

Effect of different photoinitiators and reducing agents on cure efficiency and color stability of resin-based composites using different LED wavelengths.

PubMed

de Oliveira, Dayane Carvalho Ramos Salles; Rocha, Mateus Garcia; Gatti, Alexandre; Correr, Americo Bortolazzo; Ferracane, Jack Liborio; Sinhoret, Mario Alexandre Coelho

2015-12-01

To evaluate the effect of photoinitiators and reducing agents on cure efficiency and color stability of resin-based composites using different LED wavelengths. Model resin-based composites were associated with diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide (TPO), phenylbis(2,4,6-trimethylbenzoyl) phosphine oxide (BAPO) or camphorquinone (CQ) associated with 2-(dimethylamino) ethyl methacrylate (DMAEMA), ethyl 4-(dimethyamino) benzoate (EDMAB) or 4-(N,N-dimethylamino) phenethyl alcohol (DMPOH). A narrow (Smartlite, Dentisply) and a broad spectrum (Bluephase G2, Ivoclar Vivadent) LEDs were used for photo-activation (20 J/cm(2)). Fourier transform infrared spectroscopy (FT-IR) was used to evaluate the cure efficiency for each composite, and CIELab parameters to evaluated color stability (ΔE00) after aging. The UV-vis absorption spectrophotometric analysis of each photoinitiator and reducing agent was determined. Data were analyzed using two-way ANOVA and Tukey's test for multiple comparisons (α=0.05). Higher cure efficiency was found for type-I photoinitiators photo-activated with a broad spectrum light, and for CQ-systems with a narrow band spectrum light, except when combined with an aliphatic amine (DMAEMA). Also, when combined with aromatic amines (EDMAB and DMPOH), similar cure efficiency with both wavelength LEDs was found. TPO had no cure efficiency when light-cured exclusively with a blue narrowband spectrum. CQ-systems presented higher color stability than type-I photoinitiators, especially when combined with DMPOH. After aging, CQ-based composites became more yellow and BAPO and TPO lighter and less yellow. However, CQ-systems presented higher color stability than type-I photoinitiators, as BAPO- and TPO-, despite their higher cure efficiency when photo-activated with corresponding wavelength range. Color matching is initially important, but color change over time will be one of the major reasons for replacing esthetic restorations; despite the less yellowing of these alternative photoinitiators, camphorquinone presented higher color stability. Copyright © 2015 Elsevier Ltd. All rights reserved.

Ultraviolet Irradiation of Blood: "The Cure That Time Forgot"?

PubMed

Hamblin, Michael R

2017-01-01

Ultraviolet blood irradiation (UBI) was extensively used in the 1940s and 1950s to treat many diseases including septicemia, pneumonia, tuberculosis, arthritis, asthma and even poliomyelitis. The early studies were carried out by several physicians in USA and published in the American Journal of Surgery. However with the development of antibiotics, UBI use declined and it has now been called "the cure that time forgot". Later studies were mostly performed by Russian workers and in other Eastern countries and the modern view in Western countries is that UBI remains highly controversial.This chapter discusses the potential of UBI as an alternative approach to current methods used to treat infections, as an immune-modulating therapy and as a method for normalizing blood parameters. No resistance of microorganisms to UV irradiation has been reported, and multi-antibiotic resistant strains are as susceptible as their wild-type counterparts. Low and mild doses of UV kill microorganisms by damaging the DNA, while any DNA damage in host cells can be rapidly repaired by DNA repair enzymes. However the use of UBI to treat septicemia cannot be solely due to UV-mediated killing of bacteria in the blood-stream, as only 5-7% of blood volume needs to be treated with UV to produce the optimum benefit. UBI may enhance the phagocytic capacity of various phagocytic cells (neutrophils and dendritic cells), inhibit lymphocytes, and oxidize blood lipids. The oxidative nature of UBI may have mechanisms in common with ozone therapy and other oxygen therapies. There may be some similarities to extracorporeal photopheresis (ECP) using psoralens and UVA irradiation. However there are differences between UBI and ECP in that UBI tends to stimulate the immune system, while ECP tends to be immunosuppressive. With the recent emergence of bacteria that are resistant to all known antibiotics, UBI should be more investigated as an alternative approach to infections, and as an immune-modulating therapy.

Functionalized Carbon Nanotubes in Modified Plant Oil Composites.

NASA Astrophysics Data System (ADS)

McAninch, Ian M.; Wool, Richard P.

2007-03-01

Carbon nanotubes (CNTs) with their impressive mechanical properties are ideal reinforcement material. Acrylated epoxidized soy oil (AESO) has been previously shown to have favorable interactions with carbon nanotubes; however a mixture of aggregates and dispersed tubes were found even at low CNT concentrations. In order to prevent re-aggregation, the CNTs were functionalized with a 10 carbon long aliphatic chain. These aliphatic chains are similar to the fatty acids that make up soy oil. Functionalization was verified using XPS and IR spectroscopy. These functionalized CNTs were dispersed by mechanical shear mixing into AESO both with and without styrene as a comonomer. No large aggregates were observed in the liquid, uncured, samples or in the final cured composites. Dispersion in the solid composites was verified using optical and electron microscopy. Better dispersion also resulted in improved mechanical properties.

Enhancement of a solar photo-Fenton reaction with ferric-organic ligands for the treatment of acrylic-textile dyeing wastewater.

PubMed

Soares, Petrick A; Batalha, Mauro; Souza, Selene M A Guelli U; Boaventura, Rui A R; Vilar, Vítor J P

2015-04-01

Literature describes a kinetic mineralization profile for most of acrylic-textile dyeing wastewaters using a photo-Fenton reaction characterized by a slow degradation process and high reactants consumption. This work tries to elucidate that the slow decay on DOC concentration is associated with the formation of stable complexes between Fe(3+) and textile auxiliary products, limiting the photoreduction of Fe(3+). This work also evaluates the enhancement of a solar photo-Fenton reaction through the use of different ferric-organic ligands applied to the treatment of a simulated acrylic-textile dyeing wastewater, as a pre-oxidation step to enhance its biodegradability. The photo-Fenton reaction was negatively affected by two dyeing auxiliary products: i) Sera(®) Tard A-AS, a surfactant mainly composed of alkyl dimethyl benzyl ammonium chloride and ii) Sera(®) Sperse M-IW, a dispersing agent composed of polyglycol solvents. The catalytic activity of the organic ligands toward the ferrous-catalysed system followed this order: Fe(III)-Oxalate > Fe(III)-Citrate > Fe(III)-EDDS, and all were better than the traditional photo-Fenton reaction. Different design parameters such as iron concentration, pH, temperature, flow conditions, UV irradiance and H2O2 addition strategy and dose were evaluated. The ferrioxalate induced photo-Fenton process presented the best results, achieving 87% mineralization after 9.3 kJUV L(-1) and allowing to work until near neutral pH values. As expected, the biodegradability of the textile wastewater was significantly enhanced during the photo-Fenton treatment, achieving a value of 73%, consuming 32.4 mM of H2O2 and 5.7 kJUV L(-1). Copyright © 2015 Elsevier Ltd. All rights reserved.

Bag molding processes

NASA Astrophysics Data System (ADS)

Slobodzinsky, A.

Features, materials, and techniques of vacuum, pressure, and autoclave FRP bag molding processes are described. The bags are used in sealed environments, inflated to flexibly force a curing FRP laminate to conform to a stiff mold form which defines the shape of the finished product. Densification is achieved as the bag presses out the voids and excess resin from the laminate, and consolidation occurs as the plies and adherends are bonded by the bag pressure. Curing techniques nominally involved room temperature or high temperature, and investigations of alternative techniques, such as induction, dielectric, microwave, xenon flash, UV, electron beam, and gamma radiation heating are proceeding. Polysulfone is the most common thermoplastic. Details are given of mold preparations, peel plies or release films and fabrics, bagging techniques, and reusable venting blankets and silicone rubber bags.

Soft Polymers for Building up Small and Smallest Blood Supplying Systems by Stereolithography

PubMed Central

Meyer, Wolfdietrich; Engelhardt, Sascha; Novosel, Esther; Elling, Burkhard; Wegener, Michael; Krüger, Hartmut

2012-01-01

Synthesis of a homologous series of photo-polymerizable α,ω-polytetrahydrofuranether-diacrylate (PTHF-DA) resins is described with characterization by NMR, GPC, DSC, soaking and rheometrical measurements. The curing speeds of the resins are determined under UV light exposure. Young’s modulus and tensile strength of fully cured resins show flexible to soft material attributes dependent on the molar mass of the used linear PTHF-diacrylates. Structuring the materials by stereo lithography (SL) and multiphoton polymerization (MPP) leads to tubes and bifurcated tube systems with a diameter smaller than 2 mm aimed at small to smallest supplying systems with capillary dimensions. WST-1 biocompatibility tests ofm polymer extracts show nontoxic characteristics of the adapted polymers after a washing process. Some polymers show shape memory effect (SME). PMID:24955530

Dynamic refractometer

NASA Technical Reports Server (NTRS)

Curley, Michael J. (Inventor); Sarkisov, Sergey S. (Inventor)

2008-01-01

A refractometer computer controls the rotation of a rotary plate upon which are mounted a prism optically coupled via an optical window to a spectroscopic cell holding a resin exhibiting a dynamic refractive index during photocuring. The computer system positions the prism and spectroscopic cell relative to a visible light laser which illuminates the prism-resin interface at selected incidence angles. A photodetector mounted on the plate generates a signal to the computer proportional to intensity of an internally reflected light beam. A curing light is selectively transmitted through the prism and into the photocurable resin. The refractometer determines the intensity of the internally reflected beam a selected incidence angles and determines the effective refractive index curve of the resin at an uncured state and, optionally, at a completely cured state. Next, an amount of uncured resin and selected optical components to be joined by the resin is placed in the spectroscopic cell and irradiated with the UV light. The refractometer is fixed at a selected incidence angle and measures the intensity of an internally reflected light beam of light throughout the cure cycle. The refractometer determines the resin's refractive index of the polymeric mixture by means of extrapolation of a horizontal shift in the effective refractive index curve of the resin from an uncured state to a selected point in the cure cycle.

Fabrication of polyimide based microfluidic channels for biosensor devices

NASA Astrophysics Data System (ADS)

Zulfiqar, Azeem; Pfreundt, Andrea; Svendsen, Winnie Edith; Dimaki, Maria

2015-03-01

The ever-increasing complexity of the fabrication process of Point-of-care (POC) devices, due to high demand of functional versatility, compact size and ease-of-use, emphasizes the need of multifunctional materials that can be used to simplify this process. Polymers, currently in use for the fabrication of the often needed microfluidic channels, have limitations in terms of their physicochemical properties. Therefore, the use of a multipurpose biocompatible material with better resistance to the chemical, thermal and electrical environment, along with capability of forming closed channel microfluidics is inevitable. This paper demonstrates a novel technique of fabricating microfluidic devices using polyimide (PI) which fulfills the aforementioned properties criteria. A fabrication process to pattern microfluidic channels, using partially cured PI, has been developed by using a dry etching method. The etching parameters are optimized and compared to those used for fully cured PI. Moreover, the formation of closed microfluidic channel on wafer level by bonding two partially cured PI layers or a partially cured PI to glass with high bond strength has been demonstrated. The reproducibility in uniformity of PI is also compared to the most commonly used SU8 polymer, which is a near UV sensitive epoxy resin. The potential applications of PI processing are POC and biosensor devices integrated with microelectronics.

Physiological limit of the daily endogenous cholecalciferol synthesis from UV light in cattle.

PubMed

Hymøller, L; Jensen, S K; Kaas, P; Jakobsen, J

2017-04-01

The link between UV light (sunlight) and endogenous cholecalciferol (vitamin D 3 ) synthesis in the skin of humans has been known for more than a 100 years, since doctors for the first time successfully used UV light to cure rickets in children. Years later, it was shown that UV light also had a significant effect on the cholecalciferol status in the body of cattle. The cholecalciferol status in the body is measured as the plasma concentration of 25-hydroxycholecalciferol, which in cattle and humans is the major circulating metabolite of cholecalciferol. Very little is, however, known about the quantitative efficiency of UV light as a source of cholecalciferol in cattle nutrition and physiology. Hence, the aim of this study was to determine the efficiency of using UV light for increasing the plasma 25-hydroxycholecalciferol concentration in cholecalciferol-deprived cattle. Twelve cows deprived of cholecalciferol for 6 months were divided into three treatment groups and exposed to UV light for 30, 90 or 120 min/day during 28 days. UV-light wavelengths ranged from 280 to 415 nm and 30-min exposure to the UV light was equivalent to 60-min average summer-sunlight exposure at 56 °N. Blood samples were collected every 3-4 days and analysed for 25-hydroxycholecalciferol and cholecalciferol. Results showed that increasing the exposure time from 90-120 min/day did not change the slope of the daily increase in plasma 25-hydroxycholecalciferol. Hence, it appears that cholecalciferol-deprived dairy cattle are able to increase their plasma 25-hydroxycholecalciferol concentration by a maximum of 1 ng/ml/day from UV-light exposure. Journal of Animal Physiology and Animal Nutrition © 2016 Blackwell Verlag GmbH.

High efficiency environmental sampling with UV-cured peelable coatings (aka NuGoo project)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Henzl, Vladimir; Junghans, Sylvia Ann; Lakis, Rollin Evan

This report presents slides on CA Related Project (FY13-17); Environmental sampling by IAEA (not only) during CA; Decontamination gels; Cotton swipes vs. decon gel (FY15); Contamination removal study; The origins of the NuGoo; NuGoo – proof of concept; NuGoo – FY17 project ($250K); LED lamp – which one works and why; Selecting photoinitiator; Monomers and oligomers; Results.

Scalable and continuous fabrication of bio-inspired dry adhesives with a thermosetting polymer.

PubMed

Lee, Sung Ho; Kim, Sung Woo; Kang, Bong Su; Chang, Pahn-Shick; Kwak, Moon Kyu

2018-04-04

Many research groups have developed unique micro/nano-structured dry adhesives by mimicking the foot of the gecko with the use of molding methods. Through these previous works, polydimethylsiloxane (PDMS) has been developed and become the most commonly used material for making artificial dry adhesives. The material properties of PDMS are well suited for making dry adhesives, such as conformal contacts with almost zero preload, low elastic moduli for stickiness, and easy cleaning with low surface energy. From a performance point of view, dry adhesives made with PDMS can be highly advantageous but are limited by its low productivity, as production takes an average of approximately two hours. Given the low productivity of PDMS, some research groups have developed dry adhesives using UV-curable materials, which are capable of continuous roll-to-roll production processes. However, UV-curable materials were too rigid to produce good adhesion. Thus, we established a PDMS continuous-production system to achieve good productivity and adhesion performance. We designed a thermal roll-imprinting lithography (TRL) system for the continuous production of PDMS microstructures by shortening the curing time by controlling the curing temperature (the production speed is up to 150 mm min-1). Dry adhesives composed of PDMS were fabricated continuously via the TRL system.

Design and fabrication of a variable optical attenuator based on polymer-dispersed liquid crystal

NASA Astrophysics Data System (ADS)

She, Jun; Xu, Su; Tao, Tao; Wang, Qian

2005-02-01

In order to obtain a low polarization dependent loss (PDL) and a large attenuation range simultaneously, an optimal design and fabrication of a polymer-dispersed liquid crystal (PDLC) based variable optical attenuator (VOA) is presented. First, an optimal diameter of the liquid crystal droplets is determined by the anomalous diffraction approach (ADA). This optimal diameter gives maximal scattering and thus a large attenuation range is achieved with a relatively thin liquid crystal cell. Secondly, the fabrication of PDLC cell is carried out. The influence of the ultraviolet (UV) curing condition on the morphology of the LC droplets is investigated. For a given liquid crystal concentration, the optimal UV curing power is obtained after a series of statistically designed experiments. Finally, an optical configuration of the PDLC based VOA is presented. Measurements of the attenuation and the PDL are carried out with this configuration. The measured results show that the device has a typical attenuation range of 25dB. The corresponding PDL is nearly 1dB and the insertion loss is 1.8dB. The threshold voltage is 8Vrms and the saturation voltage is 40Vrms. From these measured results, one can see that the fabricated VOA based on PDLC is much more practical for optical communications as compared to the existing ones.

21 CFR 175.210 - Acrylate ester copolymer coating.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Acrylate ester copolymer coating. 175.210 Section... COATINGS Substances for Use as Components of Coatings § 175.210 Acrylate ester copolymer coating. Acrylate...) The acrylate ester copolymer is a fully polymerized copolymer of ethyl acrylate, methyl methacrylate...

Influence of the fast-processing technique on the number of the occlusal contacts and occlusal vertical dimension of complete dentures.

PubMed

Atashrazm, Parsa; Alavijeh, Leila Zamani; Afshar, Maryam Sadat Sadrzadeh

2011-03-01

Occlusal errors during acryl processing affect the retention and stability of complete dentures. The aim of the present study was to assess the influence of a short curing technique on the number of occlusal contacts and the occlusal vertical dimension (OVD) of complete dentures. Complete dentures were prepared. The number of occlusal contacts was recorded in centric relation (CR) using 60 µ articulation paper. The OVD was recorded with the waxed trial denture in place. Dentures were then invested and processed with compression molding and short cure water bath technique. The number of occlusal contacts was recorded again. The amount of pin opening was measured for all of the complete dentures on the articulator. Data were analyzed with paired t-test to determine the alterations. The mean number of occlusal contacts before and after processing was 10.9 ± 2.4 and 6.3 ± 3.1 respectively (4.7 ± 1.9 decrease; p < 0.001). A 2 mm mean increase in OVD was observed in 47.7% of the dentures with < 6 occlusal contact changes and 88.9% of the dentures with ≥ 6 occlusal contact changes (p < 0.003). A significant change in the number of occlusal contacts was associated with an OVD increased up to two times. The short curing technique seems to be related to the decreased occlusal contacts and increased OVD. CLINICAL SIGNIFICANCES: More time is needed to adjust the occlusal errors of this method, because it has a negative effect on the morphologic pattern of artificial teeth of complete dentures and thus should be used carefully.

A simple solubility tests for the discrimination of acrylic and modacrylic fibers.

PubMed

Suga, Keisuke; Narita, Yuji; Suzuki, Shinichi

2014-05-01

In a crime scene investigation, single fibers play an important role as significant trace physical evidence. Acrylic fibers are frequently encountered in forensic analysis. Currently, acrylic and modacrylic are not discriminated clearly in Japan. Only results of FT-IR, some of acrylics were difficult to separate clearly to acrylic and modacrylic fibers. Solubility test is primitive but convenient useful method, and Japan Industrial Standards (JIS) recommends FT-IR and solubility test to distinguish acrylic and modacrylic fibers. But recommended JIS dissolving test using 100% N,N-dimethylformamide (DMF) as a solvent, some acrylics could not be discriminated. In this report, we used DMF and ethanol (90:10, v/v) solvent. The JIS method could not discriminate 6 acrylics in 60 acrylics; hence, DMF and ethanol (90:10, v/v) solvent discriminated 59 of the 60 fibers (43 acrylic and 16 modacrylic fibers) clearly, but only one modacrylic fiber incorrectly identified as acrylic. © 2014 American Academy of Forensic Sciences.

Ultraviolet blood irradiation: Is it time to remember "the cure that time forgot"?

PubMed

Wu, Ximing; Hu, Xiaoqing; Hamblin, Michael R

2016-04-01

Ultraviolet blood irradiation (UBI) was extensively used in the 1940s and 1950s to treat many diseases including septicemia, pneumonia, tuberculosis, arthritis, asthma, and even poliomyelitis. The early studies were carried out by several physicians in USA and published in the American Journal of Surgery. However, with the development of antibiotics, the use of UBI declined and it has now been called "the cure that time forgot." Later studies were mostly performed by Russian workers, and in other Eastern countries, and the modern view in Western countries is that UBI remains highly controversial. This review discusses the potential of UBI as an alternative approach to current methods used to treat infections, as an immune-modulating therapy and as a method for normalizing blood parameters. Low and mild doses of UV kill microorganisms by damaging the DNA, while any DNA damage in host cells can be rapidly repaired by DNA repair enzymes. However, the use of UBI to treat septicemia cannot be solely due to UV-mediated killing of bacteria in the bloodstream, as only 5-7% of blood volume needs to be treated with UV to produce the optimum benefit, and higher doses can be damaging. There may be some similarities to extracorporeal photopheresis (ECP) using psoralens and UVA irradiation. However, there are differences between UBI and ECP in that UBI tends to stimulate the immune system, while ECP tends to be immunosuppressive. With the recent emergence of bacteria that are resistant to all known antibiotics, UBI should be more investigated as an alternative approach to infections, and as an immune-modulating therapy. Copyright © 2016. Published by Elsevier B.V.

Ultraviolet blood irradiation: Is it time to remember “the cure that time forgot”?

PubMed Central

Wu, Ximing; Hu, Xiaoqing; Hamblin, Michael R.

2016-01-01

Ultraviolet blood irradiation (UBI) was extensively used in the 1940s and 1950s to treat many diseases including septicemia, pneumonia, tuberculosis, arthritis, asthma and even poliomyelitis. The early studies were carried out by several physicians in USA and published in the American Journal of Surgery. However with the development of antibiotics, the use of UBI declined and it has now been called “the cure that time forgot”. Later studies were mostly performed by Russian workers and in other Eastern countries, and the modern view in Western countries is that UBI remains highly controversial. This review discusses the potential of UBI as an alternative approach to current methods used to treat infections, as an immune-modulating therapy and as a method for normalizing blood parameters. Low and mild doses of UV kill microorganisms by damaging the DNA, while any DNA damage in host cells can be rapidly repaired by DNA repair enzymes. However the use of UBI to treat septicemia cannot be solely due to UV-mediated killing of bacteria in the bloodstream, as only 5–7% of blood volume needs to be treated with UV to produce the optimum benefit, and higher doses can be damaging. There may be some similarities to extracorporeal photopheresis (ECP) using psoralens and UVA irradiation. However there are differences between UBI and ECP in that UBI tends to stimulate the immune system, while ECP tends to be immunosuppressive. With the recent emergence of bacteria that are resistant to all known antibiotics, UBI should be more investigated as an alternative approach to infections, and as an immune-modulating therapy. PMID:26894849

Preparation of poly(ethylene glycol) hydrogels with different network structures for the application of enzyme immobilization.

PubMed

Choi, Dongkil; Lee, Woojin; Park, Jinwon; Koh, Wongun

2008-01-01

In this study, poly(ethylene glycol) (PEG)-based hydrogels having different network structures were synthesized by UV-initiated photopolymerization and used for the enzyme immobilization. PEGs with different molecular weight were acrylated by derivatizing both ends with acryloyl chloride and photopolymerization of PEG-diacrylate (PEG-DA) yielded crosslinked hydrogel network within 5 seconds. Attachment of acrylate groups and gelation were confirmed by ATR/FT-IR and FT-Raman spectroscopy. Network structures of hydrogels could be easily controlled by changing the molecular weight (MW) of PEG-DA and characterized by calculating molecular weight between crosslinks and mesh size from the swelling measurement. Synthesis of hydrogels with higher MW of PEG produced less crosslinked hydrogels having higher water content, larger value of Mc and mesh size, which resulted in enhanced mass transfer but loss of mechanical properties. For the enzyme immobilization, glucose oxidase (GOX) was immobilized inside PEG hydrogels by means of physical entrapment and covalent immobilization. Encapsulated GOX were covalently bound to PEG backbone using acryloyl-PEG-N-hydroxysuccinimide and maintained their activity over a week period without leakage. Kinetic study indicated that immobilized enzyme inside hydrogel prepared from higher MW of PEG possessed lower apparent Km (Michaelis-Menten constant) and higher activity.

[Preparation of Pb2+ imprinted acrylic acid-co-styrene and analysis of its adsorption properties by FAAS].

PubMed

Shawket, Abliz; Abdiryim, Supahun; Wang, Ji-De; Ismayil, Nurulla

2011-06-01

With lead ion template, acrylic acid as functional monomer, potassium persulfate as initiator, strytrene as framework monomer, lead ion imprinted polymers (Pb(II)-IIPs) were prepared using free emulsion polymerization method. The structure and morphology of the polymers were analyzed by UV-spectra, FTIR and scanning electron microscopy. The adsorption/ desorption and selectivity for Pb2+ were investigated by flame atomic absorption spectrometry (FAAS) as the detection means. The results show that compared with non-imprinted polymers(NIPs), the Pb(II)-IIPs had higher specific adsorption properties and selective recognition ability for Pb(II). The relative selectivity coefficient of Pb(II)-IIPs for Pb(II) was 6.25, 6.18, 6.25 and 6.38 in the presence of Cd(II), Cu(II), Mn(II) and Zn(II) interferences, respectively. The absorption rate was the best at the pH of adsorbent solution of 6, Adsorption rate reached 96% during the 2.5 h static adsorption time. Using 3.0 mol x L(-1) HCI as the best desorption solvent to desorb the adsorbents, the desorbtion rate reached 98%. Under the best adsorption conditions, the adsorption capacity of Pb(II)-IIPs for Pb(II) was found to be 40. mg x g(-1).

A hybrid fluorous monolithic capillary column with integrated nanoelectrospray ionization emitter for determination of perfluoroalkyl acids by nano-liquid chromatography-nanoelectrospray ionization-mass spectrometry/mass spectrometry.

PubMed

Zhang, Haiyang; Ou, Junjie; Wei, Yinmao; Wang, Hongwei; Liu, Zhongshan; Zou, Hanfa

2016-04-01

A hybrid fluorous monolithic column was simply prepared via photo-initiated free radical polymerization of an acrylopropyl polyhedral oligomeric silsesquioxane (acryl-POSS) and a perfluorous monomer (2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl acrylate) in UV-transparent fused-silica capillaries within 5min. The physical characterization of hybrid fluorous monolith, including scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, mercury intrusion porosimetry (MIP) and nitrogen adsorption/desorption measurement was performed. Chromatographic performance was also evaluated by capillary liquid chromatography (cLC). Due to the fluorous-fluorous interaction between fluorous monolith and analytes, fluorobenzenes could well be separated, and the column efficiencies reached 86,600-92,500plates/m at the velocity of 0.87mm/s for alkylbenzenes and 51,900-76,000plates/m at the velocity of 1.10mm/s for fluorobenzenes. Meanwhile, an approach to integrate nanoelectrospray ionization (ESI) emitter with hybrid fluorous monolithic column was developed for quantitative determination of perfluoroalkyl acids by nanoHPLC-ESI-MS/MS. The integration design could minimize extracolumn volume, thus excluding undesirable peak broadening and improving separation performance. Copyright © 2016 Elsevier B.V. All rights reserved.

Laterally injected light-emitting diode and laser diode

DOEpatents

Miller, Mary A.; Crawford, Mary H.; Allerman, Andrew A.

2015-06-16

A p-type superlattice is used to laterally inject holes into an III-nitride multiple quantum well active layer, enabling efficient light extraction from the active area. Laterally-injected light-emitting diodes and laser diodes can enable brighter, more efficient devices that impact a wide range of wavelengths and applications. For UV wavelengths, applications include fluorescence-based biological sensing, epoxy curing, and water purification. For visible devices, applications include solid state lighting and projection systems.

Synthesis and optical properties of metal (M) atom-doped polycarbosilane (PCS) with extended conjugation (M = Al, Dy, Er and Eu)

NASA Astrophysics Data System (ADS)

Yao, Rongqian; Zhao, Haoran; Feng, Zude; Chen, Lifu; Zhang, Ying

2013-10-01

Optical properties of metal atom-doped polycarbosilane (PCS) which originated from σ-conjugation effect were studied. Al, Dy, Er and Eu were introduced into PCS by one-pot method to yield polyaluminocarbosilane (PACS), polydysprosiumcarbosilane (PDCS), polyerbiumcarbosilane (PErCS) and polyeuropiumcarbosilane (PECS), respectively. Effects of oxidation curing and ultraviolet (UV) radiation on the photoluminescence (PL) properties of the samples were investigated. PL spectra show strong blue light-emissions and the intensity of PCS is enhanced by adding metal atoms. PACS with extended σ-conjugation exhibits an obvious PL red-shift, high intensity, high quantum yield and excellent oxidation resistance as compared with those of others. As treated under UV lamp for 3 h in air, PACS retains good UV resistance performance, owing to the AlOx (x = 4, 5, or 6) groups which effectively extend the σ-conjugation. The obtained results are expected to have important applications in active sources for electroluminescence (EL) devices, especially suitable for blue emission.

Mechanochromic behavior of a luminescent silicone rubber under tensile deformation

NASA Astrophysics Data System (ADS)

Kim, Yeon Ju; Lee, Sang Hwan; Jeong, Kwang-Un; Nah, Changwoon

2016-09-01

A novel mechanochromic elastomer based on silicone rubber and coumarin 6 dye have been prepared with various concentrations of the dye ranges from 2wt.% to a maximum of 5wt.% by solution mixing technique. After evaporating the solvent, cured samples were prepared as thin films using compression molding at 170° C. The optimum composition of the dye in rubber composites was determined based on the mechanochromic performance characterized with ultraviolet/visible (UV/Vis) spectrometer, x-ray diffraction (XRD) and spectrofluorometer (FL). The UV/Vis spectrometer monitors the dye aggregation in polymer film during the tensile deformation. The XRD monitors the change in size of dye aggregates. The FL monitors the optical response during tensile deformation due to the re-arrangement of dyes. As increasing a mechanical deformation to the polymeric composite film, UV/Vis absorption intensity was decreased and the FL emission wavelength was moved to decrease wavelength because of breaking dye aggregations. Also, XRD intensity peak was decreased, which dye aggregations were broken after mechanical deformation.

Fabrication of corner cube array retro-reflective structure with DLP-based 3D printing technology

NASA Astrophysics Data System (ADS)

Riahi, Mohammadreza

2016-06-01

In this article, the fabrication of a corner cube array retro-reflective structure is presented by using DLP-based 3D printing technology. In this additive manufacturing technology a pattern of a cube corner array is designed in a computer and sliced with specific software. The image of each slice is then projected from the bottom side of a reservoir, containing UV cure resin, utilizing a DLP video projector. The projected area is cured and attached to a base plate. This process is repeated until the entire part is made. The best orientation of the printing process and the effect of layer thicknesses on the surface finish of the cube has been investigated. The thermal reflow surface finishing and replication with soft molding has also been presented in this article.

Methods for the synthesis of olefins and derivatives

DOEpatents

Burk, Mark J; Pharkya, Priti; Van Dien, Stephen J; Burgard, Anthony P; Schilling, Christophe H

2013-06-04

The invention provides a method of producing acrylic acid. The method includes contacting fumaric acid with a sufficient amount of ethylene in the presence of a cross-metathesis transformation catalyst to produce about two moles of acrylic acid per mole of fumaric acid. Also provided is an acrylate ester. The method includes contacting fumarate diester with a sufficient amount of ethylene in the presence of a cross-metathesis transformation catalyst to produce about two moles of acrylate ester per mole of fumarate diester. An integrated process for process for producing acrylic acid or acrylate ester is provided which couples bioproduction of fumaric acid with metathesis transformation. An acrylic acid and an acrylate ester production also is provided.

Methods for the synthesis of olefins and derivatives

DOEpatents

Burk, Mark J [San Diego, CA; Pharkya, Priti [San Diego, CA; Van Dien, Stephen J [Encinitas, CA; Burgard, Anthony P [Bellefonte, PA; Schilling, Christophe H [San Diego, CA

2011-09-27

The invention provides a method of producing acrylic acid. The method includes contacting fumaric acid with a sufficient amount of ethylene in the presence of a cross-metathesis transformation catalyst to produce about two moles of acrylic acid per mole of fumaric acid. Also provided is an acrylate ester. The method includes contacting fumarate diester with a sufficient amount of ethylene in the presence of a cross-metathesis transformation catalyst to produce about two moles of acrylate ester per mole of fumarate diester. An integrated process for process for producing acrylic acid or acrylate ester is provided which couples bioproduction of fumaric acid with metathesis transformation. An acrylic acid and an acrylate ester production also is provided.

Methods for synthesis of olefins and derivatives

DOEpatents

Burk, Mark J.; Pharkya, Priti; Van Dien, Stephen J.; Burgard, Anthony P.; Schilling, Christophe H.

2016-06-14

The invention provides a method of producing acrylic acid. The method includes contacting fumaric acid with a sufficient amount of ethylene in the presence of a cross-metathesis transformation catalyst to produce about two moles of acrylic acid per mole of fumaric acid. Also provided is an acrylate ester. The method includes contacting fumarate diester with a sufficient amount of ethylene in the presence of a cross-metathesis transformation catalyst to produce about two moles of acrylate ester per mole of fumarate diester. An integrated process for process for producing acrylic acid or acrylate ester is provided which couples bioproduction of fumaric acid with metathesis transformation. An acrylic acid and an acrylate ester production also is provided.

In-house manufacturing of cylindrical silicone models for hemodynamic research

NASA Astrophysics Data System (ADS)

Denisenko, Nikita S.; Kulik, Viktor M.

2017-10-01

Laboratory studies of fluid motion in artificial vessels modeling a distinct part of circulatory system of human are of a great importance for fundamental biomechanics and for medical applications. In the medicine they are used for advancing known and developing new methods for curing cardiovascular diseases. In biomechanics, the phantoms of blood vessels are used for studying the fluid motion. However, they are quite expensive. Therefore, a development of technique for in-house manufacturing of phantoms is quite attractive. In this paper methods of manufacturing cylindrical channels of silicone rubbers (the model of the straight part of an artery) and determination of their elastic properties are described. A specially developed acrylic mold is used for this purpose. The phantoms are cast from a mixture of SKTN-A silicone and PMS-5 oil (Penta-91, Novosibirsk, Russia). The oil is used for changing elasticity properties of the silicone.

Comparative analysis of skin sensitization potency of acrylates (methyl acrylate, ethyl acrylate, butyl acrylate, and ethylhexyl acrylate) using the local lymph node assay.

PubMed

Dearman, Rebecca J; Betts, Catherine J; Farr, Craig; McLaughlin, James; Berdasco, Nancy; Wiench, Karin; Kimber, Ian

2007-10-01

There are currently available no systematic experimental data on the skin sensitizing properties of acrylates that are of relevance in occupational settings. Limited information from previous guinea-pig tests or from the local lymph node assay (LLNA) is available; however, these data are incomplete and somewhat contradictory. For those reasons, we have examined in the LLNA 4 acrylates: butyl acrylate (BA), ethyl acrylate (EA), methyl acrylate (MA), and ethylhexyl acrylate (EHA). The LLNA data indicated that all 4 compounds have some potential to cause skin sensitization. In addition, the relative potencies of these acrylates were measured by derivation from LLNA dose-response analyses of EC3 values (the effective concentration of chemical required to induce a threefold increase in proliferation of draining lymph node cells compared with control values). On the basis of 1 scheme for the categorization of skin sensitization potency, BA, EA, and MA were each classified as weak sensitizers. Using the same scheme, EHA was considered a moderate sensitizer. However, it must be emphasized that the EC3 value for this chemical of 9.7% is on the borderline between moderate (<10%) and weak (>10%) categories. Thus, the judicious view is that all 4 chemicals possess relatively weak skin sensitizing potential.

Improved Fiber Optics Final Report CRADA No. TSB-957-94

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fox, Glenn; Wilford, Sandy

The existing chemistry of Lumenyte® (an illumination fiber optic developed by LIC) was such that the component monomers inherently polymerized to a very hard mass if exposed to environmental IR, UV, or a combination of these frequencies. Lumenyte optic also would cure to a hard mass by exposure to the UV & IR generated by the illuminating lamps-although this could occur at a much slower rate, and the hardening could occur even when the adverse frequencies were filtered. The resultant product did not have the flexibility for the required applications. LIC's objective was to include other monomeric components in themore » formulation to impart permanent flexibility. LIC sought the expertise and the use of the facilities in the Polymeric Materials Section at LLNL to achieve this objective.« less

Electric field induced self-assembly of monolayers of gold nanoparticles for surface enhanced Raman scattering applications

NASA Astrophysics Data System (ADS)

Das, Suchandra; Musunuri, Naga; Kucheryavy, Pavel; Lockard, Jenny; Fischer, Ian; Singh, Pushpendra; New Jersey Institute of Technology Collaboration; Rutgers University Newark Collaboration

2017-11-01

We present a technique that uses an electric field in the direction normal to the interface for self-assembling monolayers of gold nanoparticles on fluid-liquid interfaces and freezing these monolayers onto the surface of a flexible thin film. The electric field gives rise to dipole-dipole and capillary forces which cause the particles to arrange in a triangular pattern. The technique involves assembling the monolayer on the interface between a UV-curable resin and another fluid by applying an electric field, and then curing the resin by applying UV light. The monolayer becomes embedded on the surface of the solidified resin film. We are using these films for surface enhanced Raman scattering (SERS) applications. Initial measurements indicate improved performance over commercially available SERS substrates.

Fabrication of CuInS2/ZnS quantum dots-based white light-emitting diodes with high color rendering index

NASA Astrophysics Data System (ADS)

Hsiao, Chih-Chun; Su, Yu-Sheng; Chung, Shu-Ru

2017-09-01

Among solid-state lighting technology, phosphor-converted white light-emitting diodes (pc-WLEDs) are excellent candidates to replace incandescent lamps for their merit of high energy conservation, long lifetime, high luminous efficiency as well as polarized emissions. Semiconductor quantum dots (QDs) are emerging color tunable emissive light converters. They have shown significant promise as light emitters, as solar cells, and in biological imaging. It has been demonstrated that the pc-WLED devices integrated with red emissive ZnCdSe QDs show improved color rendering index of device. However, cadmium-based QDs have limited future owing to the well-known toxicity. Recently, non-cadmium luminescence materials, i.e. CuInS2-based QDs, are investigated as desirable low toxic alternatives. Particularly, CuInS2-based QDs exhibit very broad emissions spectra with full width at half maximum (FWHM) of 100-120 nm, large Stokes shifts of 200 300 meV and finely-tunable emissions. In order to adjust emission wavelengths and improved quantum yield (QY), CuInS2/ZnS (CIS/ZnS) core/shell structure was introduced. Therefore, CIS/ZnS QDs have been extensively investigated and be used as color converter in solid-state lighting. Synthesis and application of CuInS2/ZnS core/shell QDs are conducted using a hot injection route. CIS/ZnS core/shell QDs with molar ratio of Cu:In equal to 1:4 are prepared. For WLED fabrication, the CIS/ZnS QD is dispersed in toluene first, and then it is blended with transparent acrylic-based UV resin. Subsequently, the commercial green-emitting Lu3Al5O12: Ce3+ (LuAG) phosphors are mixed with QDs-resin mixture. After that, the QDs-phosphors-resin mixtures are put in the oven at 140 °C for 1 h to evaporate the toluene. Subsequently, the homogeneous QDs-phosphors-resin mixture is dropped on the top of a blue LED chip (InGaN). Then, the device is cured by 400 W UV light to form WLED. The emission wavelength of CIS/ZnS QD exhibits yellow region of 552 nm with QY of 76 %, and with relatively broad bandwidth of 86 nm. The structure of CIS/ZnS belongs to chalcopyrite phase and its average particle size is 3.2 nm. The luminous efficacy, color rendering index (CRI), correlated color temperature (CCT), and CIE chromaticity coordinate of WLED is 47 lm/W, 89, 5661 K, and (0.33, 0.29), respectively.

Automatic centring and bonding of lenses

NASA Astrophysics Data System (ADS)

Krey, Stefan; Heinisch, J.; Dumitrescu, E.

2007-05-01

We present an automatic bonding station which is able to center and bond individual lenses or doublets to a barrel with sub micron centring accuracy. The complete manufacturing cycle includes the glue dispensing and UV curing. During the process the state of centring is continuously controlled by the vision software, and the final result is recorded to a file for process statistics. Simple pass or fail results are displayed to the operator at the end of the process.

Graphene-silica composite thin films as transparent conductors.

PubMed

Watcharotone, Supinda; Dikin, Dmitriy A; Stankovich, Sasha; Piner, Richard; Jung, Inhwa; Dommett, Geoffrey H B; Evmenenko, Guennadi; Wu, Shang-En; Chen, Shu-Fang; Liu, Chuan-Pu; Nguyen, SonBinh T; Ruoff, Rodney S

2007-07-01

Transparent and electrically conductive composite silica films were fabricated on glass and hydrophilic SiOx/silicon substrates by incorporation of individual graphene oxide sheets into silica sols followed by spin-coating, chemical reduction, and thermal curing. The resulting films were characterized by SEM, AFM, TEM, low-angle X-ray reflectivity, XPS, UV-vis spectroscopy, and electrical conductivity measurements. The electrical conductivity of the films compared favorably to those of composite thin films of carbon nanotubes in silica.

Graphene-silica Composite Thin Films as Transparent Conductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Watcharotone,S.; Dikin, D.; Stankovich, S.

2007-01-01

Transparent and electrically conductive composite silica films were fabricated on glass and hydrophilic SiO{sub x}/silicon substrates by incorporation of individual graphene oxide sheets into silica sols followed by spin-coating, chemical reduction, and thermal curing. The resulting films were characterized by SEM, AFM, TEM, low-angle X-ray reflectivity, XPS, UV-vis spectroscopy, and electrical conductivity measurements. The electrical conductivity of the films compared favorably to those of composite thin films of carbon nanotubes in silica.

Inkjet 3D printing of UV and thermal cure silicone elastomers for dielectric elastomer actuators

NASA Astrophysics Data System (ADS)

McCoul, David; Rosset, Samuel; Schlatter, Samuel; Shea, Herbert

2017-12-01

Dielectric elastomer actuators (DEAs) are an attractive form of electromechanical transducer, possessing high energy densities, an efficient design, mechanical compliance, high speed, and noiseless operation. They have been incorporated into a wide variety of devices, such as microfluidic systems, cell bioreactors, tunable optics, haptic displays, and actuators for soft robotics. Fabrication of DEA devices is complex, and the majority are inefficiently made by hand. 3D printing offers an automated and flexible manufacturing alternative that can fabricate complex, multi-material, integrated devices consistently and in high resolution. We present a novel additive manufacturing approach to DEA devices in which five commercially available, thermal and UV-cure DEA silicone rubber materials have been 3D printed with a drop-on-demand, piezoelectric inkjet system. Using this process, 3D structures and high-quality silicone dielectric elastomer membranes as thin as 2 μm have been printed that exhibit mechanical and actuation performance at least as good as conventionally blade-cast membranes. Printed silicone membranes exhibited maximum tensile strains of up to 727%, and DEAs with printed silicone dielectrics were actuated up to 6.1% area strain at a breakdown strength of 84 V μm-1 and also up to 130 V μm-1 at 2.4% strain. This approach holds great potential to manufacture reliable, high-performance DEA devices with high throughput.

Real-time measurement system for tracking birefringence, weight, thickness, and surface temperature during drying of solution cast coatings and films

NASA Astrophysics Data System (ADS)

Unsal, E.; Drum, J.; Yucel, O.; Nugay, I. I.; Yalcin, B.; Cakmak, M.

2012-02-01

This paper describes the design and performance of a new instrument to track temporal changes in physical parameters during the drying behavior of solutions, as well as curing of monomers. This real-time instrument follows in-plane and out-of-plane birefringence, weight, thickness, and surface temperature during the course of solidification of coatings and films through solvent evaporation and thermal or photocuring in a controlled atmosphere. It is specifically designed to simulate behavior of polymer solutions inside an industrial size, continuous roll-to-roll solution casting line and other coating operations where resins are subjected to ultraviolet (UV) curing from monomer precursors. Controlled processing parameters include air speed, temperature, initial cast thickness, and solute concentration, while measured parameters are thickness, weight, film temperature, in-plane and out-of-plane birefringence. In this paper, we illustrate the utility of this instrument with solution cast and dried poly (amide-imide)/DMAc (Dimethylacetamide) solution, water based black paint, and organo-modified clay/NMP (N-Methylpyrrolidone) solution. In addition, the physical changes that take place during UV photo polymerization of a monomer are tracked. This instrument is designed to be generic and it can be used for tracking any drying/swelling/solidification systems including paper, foodstuffs such as; grains, milk as well as pharmaceutical thin paste and slurries.

The PM2.5 capture of poly (lactic acid)/nano MOFs eletrospinning membrane with hydrophilic surface

NASA Astrophysics Data System (ADS)

Wang, Yating; Dai, Xiu; Li, Xu; Wang, Xinlong

2018-03-01

In this article, metal organic frameworks (MOFs) material is introduced in the poly (lactic acid) (PLA) by electrospinning to fabricate the nanocomposite membrane. The acrylic acid (AA) is grafted onto the membrane under UV light. The prepared membrane is studied by scanning electron microscopy (SEM), x-ray diffraction (XRD), thermogravimetry (TG), contact angle test and tensile strength test. The SEM image and XRD indicate that nano MOFs particles adhere to the membrane. Contact angle test shows that grafting AA on the composite fiber membrane improves its hydrophilicity effectively. TG analyses show that the particulate matter (PM) capture capacity of PLA membrane with 2 wt% ZIF-8 content is 22%, which rises to 37% after grafting.

Nail Care Products

MedlinePlus

... Acrylics") Artificial nails are composed primarily of acrylic polymers and are made by reacting together acrylic monomers, such as ethyl methacrylate monomer, with acrylic polymers, such as polymethylmethacrylate. When the reaction is completed, ...

Polymer matrix of fiber-reinforced composites: Changes in the semi-interpenetrating polymer network during the shelf life.

PubMed

Khan, Aftab A; Al-Kheraif, Abdulaziz A; Al-Shehri, Abdullah M; Säilynoja, Eija; Vallittu, Pekka K

2018-02-01

This laboratory study was aimed to characterize semi-interpenetrating polymer network (semi-IPN) of fiber-reinforced composite (FRC) prepregs that had been stored for up to two years before curing. Resin impregnated prepregs of everStick C&B (StickTech-GC, Turku, Finland) glass FRC were stored at 4°C for various lengths of time, i.e., two-weeks, 6-months and 2-years. Five samples from each time group were prepared with a light initiated free radical polymerization method, which were embedded to its long axis in self-curing acrylic. The nanoindentation readings on the top surface toward the core of the sample were made for five test groups, which were named as "stage 1-5". To evaluate the nanohardness and modulus of elasticity of the polymer matrix, a total of 4 slices (100µm each) were cut from stage 1 to stage 5. Differences in nanohardness values were evaluated with analysis of variance (ANOVA), and regression model was used to develop contributing effect of the material's different stages to the total variability in the nanomechanical properties. Additional chemical and thermal characterization of the polymer matrix structure of FRC was carried out. It was hypothesized that time of storage may have an influence on the semi-IPN polymer structure of the cured FRC. The two-way ANOVA test revealed that the storage time had no significant effect on the nanohardness of FRC (p = 0.374). However, a highly significant difference in nanohardness values was observed between the different stages of FRC (P<0.001). The regression coefficient suggests nanohardness increased on average by 0.039GPa for every storage group. The increased nanohardness values in the core region of 6-months and 2-years stored prepregs might be due to phase-segregation of components of semi-IPN structure of FRC prepregs before their use. This may have an influence to the surface bonding properties of the cured FRC. Copyright © 2017 Elsevier Ltd. All rights reserved.

Metabolism of Acrylate to β-Hydroxypropionate and Its Role in Dimethylsulfoniopropionate Lyase Induction by a Salt Marsh Sediment Bacterium, Alcaligenes faecalis M3A

PubMed Central

Ansede, John H.; Pellechia, Perry J.; Yoch, Duane C.

1999-01-01

Dimethylsulfoniopropionate (DMSP) is degraded to dimethylsulfide (DMS) and acrylate by the enzyme DMSP lyase. DMS or acrylate can serve as a carbon source for both free-living and endophytic bacteria in the marine environment. In this study, we report on the mechanism of DMSP-acrylate metabolism by Alcaligenes faecalis M3A. Suspensions of citrate-grown cells expressed a low level of DMSP lyase activity that could be induced to much higher levels in the presence of DMSP, acrylate, and its metabolic product, β-hydroxypropionate. DMSP was degraded outside the cell, resulting in an extracellular accumulation of acrylate, which in suspensions of citrate-grown cells was then metabolized at a low endogenous rate. The inducible nature of acrylate metabolism was evidenced by both an increase in the rate of its degradation over time and the ability of acrylate-grown cells to metabolize this molecule at about an eight times higher rate than citrate-grown cells. Therefore, acrylate induces both its production (from DMSP) and its degradation by an acrylase enzyme. 1H and 13C nuclear magnetic resonance analyses were used to identify the products resulting from [1-13C]acrylate metabolism. The results indicated that A. faecalis first metabolized acrylate to β-hydroxypropionate outside the cell, which was followed by its intracellular accumulation and subsequent induction of DMSP lyase activity. In summary, the mechanism of DMSP degradation to acrylate and the subsequent degradation of acrylate to β-hydroxypropionate in the aerobic β-Proteobacterium A. faecalis has been described. PMID:10543825

Allergic contact dermatitis caused by acrylic-based medical dressings and adhesives.

PubMed

Mestach, Lien; Huygens, Sara; Goossens, An; Gilissen, Liesbeth

2018-06-11

Acrylates and methacrylates are acrylic resin monomers that are known to induce skin sensitization as a result of their presence in different materials, such as nail cosmetics, dental materials, printing inks, and adhesives. Allergic contact dermatitis resulting from the use of modern wound dressings containing them has only rarely been reported. To describe 2 patients who developed allergic contact dermatitis caused by acrylic-based modern medical dressings and/or adhesives. The medical charts of patients observed since 1990 were retrospectively reviewed for (meth)acrylate allergy resulting from contact with such materials, and their demographic characteristics and patch test results were analysed. Two patients were observed in 2014 and 2016 who had presented with positive patch test reactions to several acrylic-based dressings and/or adhesive materials, and to several (meth)acrylates, that is, hydroxyethyl acrylate, hydroxyethyl methacrylate, ethyleneglycol dimethacrylate, bisphenol A-glycidyl methacrylate/epoxy-acrylate, urethane diacrylate, and/or penta-erythritol acrylate. Allergic contact dermatitis needs to be considered in patients with eczematous reactions or delayed healing following the use of acrylic-based modern dressings or adhesives. However, identification of the culprit allergen is hampered by poor cooperation from the producers, so adequate labelling of medical devices is an urgent necessity. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Occupational methacrylate and acrylate allergy--cross-reactions and possible screening allergens.

PubMed

Aalto-Korte, Kristiina; Henriks-Eckerman, Maj-Len; Kuuliala, Outi; Jolanki, Riitta

2010-12-01

Acrylic resin monomers, especially acrylates and methacrylates, are important occupational allergens. To analyse patterns of concomitant patch test reactions to acrylic monomers in relation to exposure, and to suggest possible screening allergens. We reviewed the patch test files for the years 1994-2009 at the Finnish Institute of Occupational Health for allergic reactions to acrylic monomers, and analysed the clinical records of sensitized patients. In a group of 66 patients allergic to an acrylic monomer, the most commonly positive allergens were three methacrylates, namely ethyleneglycol dimethacrylate (EGDMA), 2-hydroxyethyl methacrylate (2-HEMA) and 2-hydroxypropyl methacrylate (2-HPMA), and an acrylate, namely diethyleneglycol diacrylate (DEGDA). The patterns of concomitant reactions imply that exposure to methacrylates may induce cross-reactivity to acrylates, whereas exposure to acrylates usually does not lead to cross-allergy to methacrylates. Screening for triethyleneglycol diacrylate (TREGDA) in the baseline series was found to be useful, as 3 of 8 patients with diagnosed occupational acrylate allergy might have been missed without the screening. A short screening series of four allergens, EGDMA, DEGDA, 2-HPMA and pentaerythritol triacrylate (PETA), would have screened 93% of our 66 patients; each of the remaining 5 patients reacted to different acrylic monomer(s). © 2010 John Wiley & Sons A/S.

Visible Light Crosslinking of Methacrylated Hyaluronan Hydrogels for Injectable Tissue Repair

PubMed Central

Fenn, Spencer L.; Oldinski, Rachael A.

2015-01-01

Tissue engineering hydrogels are primarily cured in situ using ultraviolet (UV) radiation which limits the use of hydrogels as drug or cell carriers. Visible green light activated crosslinking systems are presented as a safe alternative to UV photocrosslinked hydrogels, without compromising material properties such as viscosity and stiffness. The objective of this study was to fabricate and characterize photocrosslinked hydrogels with well-regulated gelation kinetics and mechanical properties for the repair or replacement of soft tissue. An anhydrous methacrylation of hyaluronan (HA) was performed to control the degree of modification (DOM) of HA, verified by 1H-NMR spectroscopy. UV activated crosslinking was compared to visible green light activated crosslinking. While the different photocrosslinking techniques resulted in varied crosslinking times, comparable mechanical properties of UV and green light activated crosslinked hydrogels were achieved using each photocrosslinking method by adjusting time of light exposure. Methacrylated HA (HA-MA) hydrogels of varying molecular weight, DOM and concentration exhibited compressive moduli ranging from 1 kPa to 116 kPa, for UV crosslinking, and 3 kPa to 146 kPa, for green light crosslinking. HA-MA molecular weight and concentration were found to significantly influence moduli values. HA-MA hydrogels did not exhibit any significant cytotoxic affects towards human mesenchymal stem cells. Green light activated crosslinking systems are presented as a viable method to form natural-based hydrogels in situ. PMID:26097172

Fluid management in roll-to-roll nanoimprint lithography

NASA Astrophysics Data System (ADS)

Jain, A.; Bonnecaze, R. T.

2013-06-01

The key process parameters of UV roll-to-roll nanoimprint lithography are identified from an analysis of the fluid, curing, and peeling dynamics. The process includes merging of droplets of imprint material, curing of the imprint material from a viscous liquid to elastic solid resist, and pattern replication and detachment of the resist from template. The time and distances on the web or rigid substrate over which these processes occur are determined as function of the physical properties of the uncured liquid, the cured solid, and the roller configuration. The upper convected Maxwell equation is used to model the viscoelastic liquid and to calculate the force on the substrate and the torque on the roller. The available exposure time is found to be the rate limiting parameter and it is O(√Rho /uo), where R is the radius of the roller, ho is minimum gap between the roller and web, and uo is the velocity of the web. The residual layer thickness of the resist should be larger than the gap between the roller and the substrate to ensure complete feature filling and optimal pattern replication. For lower residual layer thickness, the droplets may not merge to form a continuous film for pattern transfer.

Fabrication de structures tridimensionnelles de nanocomposites polymeres charges de nanotubes de carbone a simple paroi

NASA Astrophysics Data System (ADS)

Laberge Lebel, Louis

There is currently a worldwide effort for advances in micro and nanotechnologies due to their high potential for technological applications in fields such as microelectromechanical systems (MEMS), organic electronics and structural microstructures for aerospace. In these applications, carbon nanotube/polymer nanocomposites represent interesting material options compared to conventional resins for their enhanced mechanical and electrical properties. However, several significant scientific and technological challenges must first be overcome in order to rapidly and cost-effectively fabricate nanocomposite-based microdevices. Fabrication techniques have emerged for fabricating one- of two-dimensional (1D/2D) nanocomposite structures but few techniques are available for three-dimensional (3D) nanocomposite structures. The overall objective of this thesis is the development of a manufacturing technique allowing the fabrication of 3D structures of single-walled carbon nanotube (C-SWNT)/polymer nanocomposite. This thesis reports the development of a direct-write fabrication technique that greatly extends the fabrication space for 3D carbon nanotube/polymer nanocomposite structures. The UV-assisted direct-write (UV-DW) technique employs the robotically-controlled micro-extrusion of a nanocomposite filament combined with a UV exposure that follows the extrusion point. Upon curing, the increased rigidity of the extruded filament enables the creation of multi-directional shapes along the trajectory of the extrusion point. The C-SWNT material is produced by laser ablation of a graphite target and purified using a nitric acid reflux. The as-grown and purified material is characterized under transmission electron microscopy and Raman spectroscopy. The purification procedure successfully graphed carboxylic groups on the surface of the C-SWNTs, shown by X-ray photoelectron spectroscopies. An incorporation procedure in the polymer is developed involving a non-covalent functionalization of the nanotubes by zinc protoporphyrin IX molecule and high shear mixing using a three-roll mill. The incorporation of the C-SWNTs into the resin led to an increase of the viscosity and the apparition of a shear thinning behaviour, characterized by capillary viscometry. The nanocomposite UV-curing behavior is characterized under differential scanning calorimetry coupled with a UV source. A further adjustment of the shear thinning behavior using fumed silica enabled the UV-DW fabrication of microbeams. Mechanical characterization reveals significant increase in both strength (by ˜64%) and modulus (by more than 15 times). These mechanical enhancements are attributed to both the covalent and the non-covalent functionalizations of the C-SWNTs. Nanocomposite spring networks composed of three micro-coils fabricated using the UV-DW technique are mechanically tested under compression and show a rigidity of ˜11.5 mN/mm. A micro-coil is also deposited between two uneven electrodes and a 10-6 S/cm electrical conductivity is measured. Nanocomposite scaffold structures are also deposited using the UV-DW technique. This thesis also reports the fabrication of 3D micro structured beams reinforced with the C-SWNT/polymer nanocomposite by using an approach based on the infiltration of 3D microfluidic networks. The 3D microfluidic network is first fabricated by the direct-write assembly method, which consists of the robotized deposition of fugitive ink filaments on an epoxy substrate, forming a 3D micro structured scaffold. After encapsulating the 3D micro-scaffold structure with an epoxy resin, the fugitive ink is liquefied and removed, resulting in a 3D network of interconnected microchannels. This microfluidic network is then infiltrated by the C-SWNT/polyurethane nanocomposite and subsequently cured. The final samples consist of rectangular beams having a complex 3D-skeleton structure of C-SWNT/polyrner nanocomposite fibers, adapted to offer better performance under flexural solicitation. Dynamic mechanical analysis in flexion show an increase of 12.5% in the storage modulus under 35°C compared to the resin infiltrated beams. The manufacturing techniques demonstrated here, i.e. UV assisted direct writing and the infiltration of 3D microfluidic networks, open new prospects for the achievement of 3D reinforced micro structures that could find application in organic electronics, MEMS, sensor, tissue engineering scaffolds and aerospace.

Allergic contact dermatitis to acrylates in disposable blue diathermy pads.

PubMed Central

Sidhu, S. K.; Shaw, S.

1999-01-01

We report 2 cases of elicitation of allergic contact dermatitis to acrylates from disposable blue diathermy pads used on patients who underwent routine surgery. Their reactions were severe, and took approximately 5 weeks to resolve. Both patients gave a prior history of finger tip dermatitis following the use of artificial sculptured acrylic nails, which is a common, but poorly reported, cause of acrylate allergy. Patch testing subsequently confirmed allergies to multiple acrylates present in both the conducting gel of disposable blue diathermy pads, and artificial sculptured acrylic nails. We advocate careful history taking prior to surgery to avoid unnecessary exposure to acrylates in patients already sensitized. Images Figure 1 Figure 2 PMID:10364952

Acrylic acid removal by acrylic acid utilizing bacteria from acrylonitrile-butadiene-styrene resin manufactured wastewater treatment system.

PubMed

Wang, C C; Lee, C M

2006-01-01

The aim of this study is to isolate the acrylic acid utilizing bacteria from the ABS resin manufactured wastewater treatment system. The bacteria should have the ability to remove acrylic acid and tolerate the acrylonitrile and acrylamide toxicity. The aim is also to understand the performance of isolated pure strain for treating different initial acrylic acid concentrations from synthetic wastewater. The results are: twenty strains were isolated from the ABS resin manufactured wastewater treatment system and twelve of them could utilize 600 mg/l acrylic acid for growth. Seven of twelve strains could tolerate the acrylonitrile and acrylamide toxicity, when the concentration was below 300 mg/l. Bacillus thuringiensis was one of the seven strains and the optimum growth temperature was 32 degrees C. Bacillus thuringiensis could utilize acrylic acid for growth, when the initial acrylic acid concentration was below 1,690.4 mg/l. Besides this, when the initial acrylic acid concentration was below 606.8 mg/l, the acrylic acid removal efficiency exceeded 96.3%. Bacillus thuringiensis could tolerate 295.7 mg/l acrylamide and 198.4 mg/l acrylonitrile toxicity but could not tolerate 297.3 mg/l epsilon-caprolactam.

Acrylate and methacrylate contact allergy and allergic contact disease: a 13-year review.

PubMed

Spencer, Ashley; Gazzani, Paul; Thompson, Donna A

2016-09-01

(Meth)acrylates are important causes of contact allergy and allergic contact disease, such as dermatitis and stomatitis, with new and emerging sources resulting in changing clinical presentations. To identify the (meth)acrylates that most commonly cause allergic contact disease, highlight their usefulness for screening, and examine their relationship with occupational and clinical data. A retrospective review of results from patch tests performed between July 2002 and September 2015, in one tertiary Cutaneous Allergy Unit, was performed A series of 28 (meth)acrylates was applied to 475 patients. Results were positive in 52 cases, with occupational sources being identified in 24. Industrial exposures and acrylic nails were responsible for 13 and 10 cases, respectively, with wound dressings being implicated in 7. We found that four individual (meth)acrylates (2-hydroxyethyl acrylate, 2-hydroxypropyl methacrylate, bisphenol A glycerolate dimethacrylate, and ethyl acrylate), if used as a screening tool, could have identified 47 (90.4%) of our positive cases. Our 13-year experience indicates a changing landscape of (meth)acrylate contact allergy and allergic contact disease, with an observed shift in exposures away from manufacturing and towards acrylic nail sources. Wound dressings are highlighted as emerging sources of sensitization. Larger studies are required to establish the sensitivity and specificity of the four (meth)acrylates proposed for potential screening. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Large Acrylic Spherical Windows In Hyperbaric Underwater Photography

NASA Astrophysics Data System (ADS)

Lones, Joe J.; Stachiw, Jerry D.

1983-10-01

Both acrylic plastic and glass are common materials for hyperbaric optical windows. Although glass continues to be used occasionally for small windows, virtually all large viewports are made of acrylic. It is easy to uderstand the wide use of acrylic when comparing design properties of this plastic with those of glass, and glass windows are relatively more difficult to fabricate and use. in addition there are published guides for the design and fabrication of acrylic windows to be used in the hyperbaric environment of hydrospace. Although these procedures for fabricating the acrylic windows are somewhat involved, the results are extremely reliable. Acrylic viewports are now fabricated to very large sizes for manned observation or optical quality instrumen tation as illustrated by the numerous acrylic submersible vehicle hulls for hu, an occupancy currently in operation and a 3600 large optical window recently developed for the Walt Disney Circle Vision under-water camera housing.

Mitigation and control of the overcuring effect in mask projection micro-stereolithography

NASA Astrophysics Data System (ADS)

O'Neill, Paul F.; Kent, Nigel; Brabazon, Dermot

2017-10-01

Mask Projection micro-Stereolithography (MPμSL) is an additive manufacturing technique capable of producing solid parts with micron-scale resolution from a vat of photocurable liquid polymer resin. Although the physical mechanism remains the same, the process differs from traditional laser-galvanometer based stereolithography (SL) in its use of a dynamic mask UV projector, or digital light processor (DLP), which cures each location within each 3D layer at the same time. One area where MPµSL has garnered considerable attention is in the field of microfluidics and Lab-on-a-Chip, where complex multistep microfabrication techniques adopted from the semiconductor industry are still widely used, and where MPµSL offers the ability to fabricate completely encapsulated fluidic channels in a single step and at low cost [1-3]. However, a significant obstacle exists in the prevention of channel blockage due to overcuring of the polymer resin [4, 5]. Overcuring can be attributed to the so-called `back side effect' [2] which occurs during the build process as light from successive layers penetrates into the resin to a depth greater than the layer thickness. This effect is most prevalent in channels or features oriented horizontally (in a parallel plane to that of the build platform). Currently there are two main approaches in controlling the cure depth; 1. the chemical approach, which involves doping the resin material with a chemical light absorber [6-8]; and 2. by improving the system's hardware and optical elements to improve the homogeneity of the light dosage and control the cure depth [9]. Here we investigate a third approach through modification of the 3D CAD file prior to printing to mitigate for UV light leakage from successive build layers. Although used here in conjunction with the MPμSL technique, this approach can be applied to a range of SL techniques to improve printer resolution and enable production of internal features with higher dimensional accuracy.

Synthesis of ceramic-based porous gradient structures for applications in energy conversion and related fields

NASA Astrophysics Data System (ADS)

Graule, Thomas; Ozog, Paulina; Durif, Caroline; Wilkens-Heinecke, Judit; Kata, Dariusz

2016-06-01

Porous, graded ceramic structures are of high relevance in the field of energy conversion as well as in catalysis, and additionally in filtration technology and in biomedical applications. Among different technologies for the tailored design for such structures we demonstrate here a new environmental friendly UV curing-based concept to prepare laminated structures with pore sizes ranging from a few microns up to 50 microns in diameter and with porosities ranging from 10% up to 75 vol.% porosity.

Effect of joining the sectioned implant-supported prosthesis on the peri-implant strain generated in simulated mandibular model.

PubMed

Singh, Ipsha; Nair, K Chandrasekharan; Shetty, Jayakar

2017-01-01

The aim of this study is to evaluate the strain developed in simulated mandibular model before and after the joining of an implant-supported screw-retained prosthesis by different joining techniques, namely, arc welding, laser welding, and soldering. A specimen simulating a mandibular edentulous ridge was fabricated in heat-cured acrylic resin. 4-mm holes were drilled in the following tooth positions; 36, 33, 43, 46. Implant analogs were placed in the holes. University of California, Los Angeles, abutment was attached to the implant fixture. Eight strain gauges were attached to the acrylic resin model. Six similar models were made. Implant-supported screw-retained fixed prosthesis was fabricated in nickel-chromium alloy. A load of 400 N was applied on the prosthesis using universal testing machine. Resultant strain was measured in each strain gauge. All the prostheses were sectioned at the area between 36 and 33, 33 and 43, and 43 and 46 using 35 micrometer carborundum disc, and strain was measured in each strain gauge after applying a load of 400 N on the prosthesis. Specimens were joined by arc welding, soldering, and laser welding. After joining, a load of 400 N was applied on each prosthesis and the resultant strain was measured in each strain gauge. Highest mean strain values were recorded before sectioning of the prostheses (889.9 microstrains). Lowest mean strain values were recorded after sectioning the prosthesis and before reuniting it (225.0 microstrains). Sectioning and reuniting the long-span implant prosthesis was found to be a significant factor in influencing the peri-implant strain.

High-refractive index polyacrylates based on quinolinone-structures for intraocular lenses

NASA Astrophysics Data System (ADS)

Dams, Christian; Helmstetter, Simon; Hampp, Norbert

2017-02-01

Intraocular lenses (IOL) have experienced an expanding application over the last decades. Not only they can be used to cure cataract caused blindness, but they are also appointed to ease visual impairments (e.g. -18 - 10 dioptre or astigmatism).[1] These phake IOL require materials with very high refractive indices due to the limited space at the implanting position in the eye of the patient. This enables less invasive operations and such with smaller incisions.[2] Quinolinone derivates, like carbostyril, are currently known from drug design and as a main structural component of several antibiotics.[3] Although they show high refractive indices and good dispersions they have not yet been used in materials for ophthalmic applications. We synthesized and characterized novel high refractive index polymers containing quinolinones as the main refractive unit of the structure.[4] We showed that it was possible to build quinolinone polymers with high refractive indices up to 1.685 at 589 nm. Using this material it would theoretically be possible to reduce the lens thickness of an IOL to under 40 percent compared to a commercial hydrogel lens with a refractive index of 1.470. We also used the synthesized quinolinone acrylates to create hydrophobic copolymers with improved physical properties and high transmission in the visible spectral range. Besides the good lightfastness these copolymers also showed very low tendencies of glistening. In conclusion quinolinones show attractive performances for the usage as a component in acrylic copolymers. If the requirements for IOL keep rising in the coming years these monomers could be used to boost the refractive index of ophthalmic polymer compositions.

Hydroxyapatite implants with designed internal architecture.

PubMed

Chu, T M; Halloran, J W; Hollister, S J; Feinberg, S E

2001-06-01

Porous hydroxyapatite (HA) has been used as a bone graft material in the clinics for decades. Traditionally, the pores in these HAs are either obtained from the coralline exoskeletal patterns or from the embedded organic particles in the starting HA powder. Both processes offer very limited control on the pore structure. A new method for manufacturing porous HA with designed pore channels has been developed. This method is essentially a lost-mold technique with negative molds made with Stereolithography and a highly loaded curable HA suspension as the ceramic carrier. Implants with designed channels and connection patterns were first generated from a Computer-Aided-Design (CAD) software and Computer Tomography (CT) data. The negative images of the designs were used to build the molds on a stereolithography apparatus with epoxy resins. A 40 vol% HA suspension in propoxylated neopentyl glycol diacrylate (PNPGDA) and iso-bornyl acrylate (IBA) was formulated. HA suspension was cast into the epoxy molds and cured into solid at 85 degrees C. The molds and acrylate binders were removed by pyrolysis, followed by HA green body sintering. With this method, implants with six different channel designs were built successfully and the designed channels were reproduced in the sintered HA implants. The channels created in the sintered HA implants were between 366 microm and 968 microm in diameter with standard deviations of 50 microm or less. The porosity created by the channels were between 26% and 52%. The results show that HA implants with designed connection pattern and well controlled channel size can be built with the technique developed in this study. Copyright 2001 Kluwer Academic Publishers

Marginal Accuracy and Internal Fit of Dental Copings Fabricated by Modern Additive and Subtractive Digital Technologies.

PubMed

Nelson, Neha; K S, Jyothi; Sunny, Kiran

2017-03-01

The margins of copings for crowns and retainers of fixed partial dentures affect the progress of microleakage and dental caries. Failures occur due to altered fit which is also influenced by the method of fabrication. An in-vitro study was conducted to determine among the cast base metal, copy milled zirconia, computer aided designing computer aided machining/manufacturing zirconia and direct metal laser sintered copings which showed best marginal accuracy and internal fit. Forty extracted maxillary premolars were mounted on an acrylic model and reduced occlusally using a milling machine up to a final tooth height of 4 mm from the cementoenamel junction. Axial reduction was accomplished on a surveyor and a chamfer finish line was given. The impressions and dies were made for fabrication of copings which were luted on the prepared teeth under standardized loading, embedded in self-cure acrylic resin, sectioned and observed using scanning electron microscope for internal gap and marginal accuracy. The copings fabricated using direct metal laser sintering technique exhibited best marginal accuracy and internal fit. Comparison of mean between the four groups by ANOVA and post-hoc Tukey HSD tests showed a statistically significant difference between all the groups (p⟨0.05). It was concluded that the copings fabricated using direct metal laser sintering technique exhibited best marginal accuracy and internal fit. Additive digital technologies such as direct metal laser sintering could be cost-effective for the clinician, minimize failures related to fit and increase longevity of teeth and prostheses. Copyright© 2017 Dennis Barber Ltd.

A comparative evaluation of polymerization stress data obtained with four different mechanical testing systems.

PubMed

Gonçalves, Flávia; Boaro, Leticia C; Ferracane, Jack L; Braga, Roberto R

2012-06-01

The null hypothesis was that mechanical testing systems used to determine polymerization stress (σ(pol)) would rank a series of composites similarly. Two series of composites were tested in the following systems: universal testing machine (UTM) using glass rods as bonding substrate, UTM/acrylic rods, "low compliance device", and single cantilever device ("Bioman"). One series had five experimental composites containing BisGMA:TEGDMA in equimolar concentrations and 60, 65, 70, 75 or 80 wt% of filler. The other series had five commercial composites: Filtek Z250 (3M ESPE), Filtek A110 (3M ESPE), Tetric Ceram (Ivoclar), Heliomolar (Ivoclar) and Point 4 (Kerr). Specimen geometry, dimensions and curing conditions were similar in all systems. σ(pol) was monitored for 10 min. Volumetric shrinkage (VS) was measured in a mercury dilatometer and elastic modulus (E) was determined by three-point bending. Shrinkage rate was used as a measure of reaction kinetics. ANOVA/Tukey test was performed for each variable, separately for each series. For the experimental composites, σ(pol) decreased with filler content in all systems, following the variation in VS. For commercial materials, σ(pol) did not vary in the UTM/acrylic system and showed very few similarities in rankings in the others tests system. Also, no clear relationships were observed between σ(pol) and VS or E. The testing systems showed a good agreement for the experimental composites, but very few similarities for the commercial composites. Therefore, comparison of polymerization stress results from different devices must be done carefully. Copyright © 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Effect of fabrication pressure on the fatigue performance of Cemex XL acrylic bone cement.

PubMed

Lewis, Gladius; Janna, S I

2004-01-01

During a cemented arthroplasty, the prepared polymerizing dough of acrylic bone cement is subjected to pressurization in a number of ways; first, during delivery into the freshly prepared bone bed, second, during packing in that bed (either digitally or with the aid of a mechanical device), and, third, during the insertion of the prosthesis. Only a few studies have reported on the influence of the level of pressurization experienced during these events (which, depending on the cementing technique used, has been put at between 8 and 273 kPa) on various properties of the cement. That was the focus of the present study, in which the fully reversed tension-compression (+/-15 MPa; 5 Hz) fatigue lives (expressed as number of cycles to fracture, N(f)) of rectangular cross-sectioned "dog-bone" specimens (Type V, per ASTM D 638) fabricated from Cemex XL cement, at pressure applied continuously to the cement dough during curing in the specimen mold, p=75,150, and 300 kPa, were determined. The N(f) results were analyzed using the linearized transformation of the three-parameter Weibull relationship to obtain estimates of the Weibull mean, N(WM), which was taken to be the index of fatigue performance of the specimen set. Over the range of p studied, N(WM) increased as p increased (for example, from 329,118 cycles when p was 75 kPa to 388,496 cycles when p was 300 kPa); however, the increase was not significant over any pair of p increment steps (Mann-Whitney U-test; alpha<0.05).

Three-dimensional printing fiber reinforced hydrogel composites.

PubMed

Bakarich, Shannon E; Gorkin, Robert; in het Panhuis, Marc; Spinks, Geoffrey M

2014-09-24

An additive manufacturing process that combines digital modeling and 3D printing was used to prepare fiber reinforced hydrogels in a single-step process. The composite materials were fabricated by selectively pattering a combination of alginate/acrylamide gel precursor solution and an epoxy based UV-curable adhesive (Emax 904 Gel-SC) with an extrusion printer. UV irradiation was used to cure the two inks into a single composite material. Spatial control of fiber distribution within the digital models allowed for the fabrication of a series of materials with a spectrum of swelling behavior and mechanical properties with physical characteristics ranging from soft and wet to hard and dry. A comparison with the "rule of mixtures" was used to show that the swollen composite materials adhere to standard composite theory. A prototype meniscus cartilage was prepared to illustrate the potential application in bioengineering.

Development of (acrylic acid/ polyethylene glycol)-zinc oxide mucoadhesive nanocomposites for buccal administration of propranolol HCl

NASA Astrophysics Data System (ADS)

Mahmoud, Ghada A.; Ali, Amr El-Hag; Raafat, Amany I.; Badawy, Nagwa A.; Elshahawy, Mai. F.

2018-06-01

A series of mucoadhesive nanocomposites with self disinfection properties composed of acrylic acid, polyethylene glycol and ZnO nanoparticles (AAc/PEG)-ZnO were developed for localized buccal Propranolol HCl delivery. γ-irradiation as a clean tool for graft copolymerization process was used for the preparation of (AAc/PEG) hydrogels. In suite precipitation technique was used for ZnO nanoparticles immobilization within (AAc/PEG) hydrogels. The developed (AAc/PEG)-ZnO nanocomposites were characterized by X-ray diffraction (XRD), UV-Vis spectrophotometer, energy dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM) to confirm the success of ZnO nanoparticles formation within the (AAc/PEG) matrices. The presence of ZnO nanoparticles improves the thermal stability as indicated using thermogravimetric analysis (TGA). The mucoadhesion characteristics such as hydration degree, surface pH, and mucoadhesive strength were evaluated in artificial saliva solution. The self disinfection property of the developed (AAc/PEG)-ZnO nanocomposites was investigated by examining their resistance to pathogenic microorganisms such as Staphylococcus aureus, Bacillus subtilis, and Escherichia coli using disc diffusion method. The release of Propranolol -HCl drug in artificial saliva was found to obey a non-Fickian diffusion mechanism. The obtained results suggests that (AAc/PEG)-ZnO nanocomposites could be used as mucoadhesive carrier for buccal drug delivery with efficient antibacterial properties.

Development of nitroxide radicals-containing polymer for scavenging reactive oxygen species from cigarette smoke

NASA Astrophysics Data System (ADS)

Yoshitomi, Toru; Kuramochi, Kazuhiro; Binh Vong, Long; Nagasaki, Yukio

2014-06-01

We developed a nitroxide radicals-containing polymer (NRP), which is composed of poly(4-methylstyrene) possessing nitroxide radicals as a side chain via amine linkage, to scavenge reactive oxygen species (ROS) from cigarette smoke. In this study, the NRP was coated onto cigarette filters and its ROS-scavenging activity from streaming cigarette smoke was evaluated. The intensity of electron spin resonance signals of the NRP in the filter decreased after exposure to cigarette smoke, indicating consumption of nitroxide radicals. To evaluate the ROS-scavenging activity of the NRP-coated filter, the amount of peroxy radicals in an extract of cigarette smoke was measured using UV-visible spectrophotometry and 1,1-diphenyl-2-picrylhydrazyl (DPPH). The absorbance of DPPH at 517 nm decreased with exposure to cigarette smoke. When NRP-coated filters were used, the decrease in the absorbance of DPPH was prevented. In contrast, both poly[4-(cyclohexylamino)methylstyrene]- and poly(acrylic acid)-coated filters, which have no nitroxide radical, did not show any effect, indicating that the nitroxide radicals in the NRP scavenge the ROS in cigarette smoke. As a result, the extract of cigarette smoke passed through the NRP-coated filter has a lower cellular toxicity than smoke passed through poly[4-(cyclohexylamino)methylstyrene]- and poly(acrylic acid)-coated filters. Accordingly, NRP is a promising material for ROS scavenging from cigarette smoke.

Coupled adsorption-photocatalytic degradation of crystal violet under sunlight using chemically synthesized grafted sodium alginate/ZnO/graphene oxide composite.

PubMed

Mohamed, S K; Hegazy, Sh H; Abdelwahab, N A; Ramadan, A M

2018-03-01

This research aimed to synthesize natural polymer nanocomposite and employ it for coupled adsorption- photocatalytic degradation of crystal violet. Sodium alginate-g-poly (acrylic acid-co-cinnamic acid) and its composites with ZnO nanorods and graphene oxide sheets were synthesized and characterized using FT-IR, XRD, SEM, HR-TEM and DR/UV-vis spectroscopy. The adsorption efficiency of samples for crystal violet has been studied in the dark. The effect of different parameters as pH, initial dye concentration, contact time and temperature on the adsorption efficiency of the synthesized sample has been examined. Kinetics studies showed that the adsorption of all samples was well described by the pseudo-second-order model and the equilibrium adsorption results fitted Freundlich model. The maximum adsorption capacity achieved at pH 5.0 was 13.85 mg g -1 . Thermodynamic studies exhibited that the adsorption is spontaneous, endothermic in nature and leads to higher entropy. Coupled adsorption-photocatalytic degradation studies under sunlight showed an enhancement in the removal efficiency by 10%. In the case of sodium alginate-g-poly (acrylic acid-co-cinnamic acid)/ZnO/graphene oxide composite, the removal efficiency after 5 h under sunlight was 94% versus 84% in the dark. Copyright © 2017 Elsevier B.V. All rights reserved.

A hydrogel-mediated scalable strategy toward core-shell polyaniline/poly(acrylic acid)-modified carbon nanotube hybrids as efficient electrodes for supercapacitor applications

NASA Astrophysics Data System (ADS)

Liu, Qingqing; Bai, Zhengyu; Fan, Jingbiao; Sun, Zhipeng; Mi, Hongyu; Zhang, Qing; Qiu, Jieshan

2018-04-01

Structural failure of polyaniline (PANI) stemmed from repeated swelling-shrinkage during Faradic process represents an imminent issue hindering the real application of this material for advanced energy storage. Herein, we explore a clean and facile hydrogel-mediated layer-by-layer strategy to conformally coat a layer of oriented PANI nanofibers on multi-walled carbon nanotubes (MWCNTs) where a layer of UV-polymerized poly(acrylic acid) (PAA) hydrogel is first formed in between as electrodes for supercapacitors. Such an intriguing core-shell tri-component structure perfectly alleviates the drawbacks of PANI as well as combines the advantages of MWCNTs. Especially, the hydrogel used increases the adhesion between PANI and MWCNTs, buffers the structural variation of PANI during cycling, and provide extra driving force accelerating electrolyte penetration throughout active materials. Therefore, the well-intergrown hybrids (PANI/P-MWCNT) display high electrochemical performance as compared to PANI and PANI/MWCNT, i.e., an improved capacitance of 612.5 F g-1 at 0.5 A g-1, and excellent cycling behavior of 81.5% capacitance retention at 5 A g-1 over 1500 cycles. Also, the maximum energy density of the PANI/P-MWCNT based symmetric configuration reaches 8.2 Wh kg-1. Significantly, such a hydrogel-bridged design concept may find the important application for the synthesis of competitive candidates for energy storage.

Waterborne Polymeric Films.

DTIC Science & Technology

1979-12-01

resin types: 1) acrylic latex, 2) acrylic solution polymer, 3) epoxy emulsions, 4) polyurethane, 5) butadiene elastomeric latex, 6) polyester/ alkyd , 7...emulsions and the class of polyester/ alkyd resins were evaluated only as network, crosslinked films. -53- j z I, ACRYLIC SOLUTIONLATEX URE THANE ACRYLIC ...amount of "plasticizing" monomer such as ethyl acrylate . 2.3.1.3 Aqueous Polyester Alkyd Resins As indicated in section 2.2.7 of this report,

Engineering single-molecule, nanoscale, and microscale bio-functional materials via click chemistry

NASA Astrophysics Data System (ADS)

Daniele, Michael Angelo-Anthony

To expand the design envelope and supplement the materials library available to biomaterials scientists, the copper(I)-catalyzed azide-alkyne cycloaddition (CuCAAC) was explored as a route to design, synthesize and characterize bio-functional small-molecules, nanoparticles, and microfibers. In each engineered system, the use of click chemistry provided facile, bio-orthogonal control for materials synthesis; moreover, the results provided a methodology and more complete, fundamental understanding of the use of click chemistry as a tool for the synergy of biotechnology, polymer and materials science. Fluorophores with well-defined photophysical characteristics (ranging from UV to NIR fluorescence) were used as building blocks for small-molecule, fluorescent biosensors. Fluorophores were paired to exhibit fluorescence resonant energy transfer (FRET) and used to probe the metabolic activity of carbazole 1,9a-dioxygenase (CARDO). The FRET pair exhibited a significant variation in PL response with exposure to the lysate of Pseudomonas resinovorans CA10, an organism which can degrade variants of both the donor and acceptor fluorophores. Nanoparticle systems were modified via CuCAAC chemistry to carry affinity tags for CARDO and were subsequently utilized for affinity based bioseparation of CARDO from crude cell lysate. The enzymes were baited with an azide-modified carbazolyl-moiety attached to a poly(propargyl acrylate) nanoparticle. Magnetic nanocluster systems were also modified via CuCAAC chemistry to carry fluorescent imaging tags. The iron-oxide nanoclusters were coated with poly(acrylic acid-co-propargyl acrylate) to provide a clickable surface. Ultimately, alternate Cu-free click chemistries were utilized to produce biohybrid microfibers. The biohybrid microfibers were synthesized under benign photopolymerization conditions inside a microchannel, allowing the encapsulation of viable bacteria. By adjusting pre-polymer solutions and laminar flow rates within the microchannel, the morphology, hydration, and thermal properties of the fibers were easily tuned. The methodology produced hydrogel fibers that sustained viable cells as demonstrated by the encapsulation and subsequent proliferation of Bacillus cereus and Escherichia coli communities.

Direct metal transfer printing on flexible substrate for fabricating optics functional devices

NASA Astrophysics Data System (ADS)

Jiang, Yingjie; Zhou, Xiaohong; Zhang, Feng; Shi, Zhenwu; Chen, Linsen; Peng, Changsi

2015-11-01

New functional materials and devices based on metal patterns can be widely used in many new and expanding industries,such as flat panel displays, alternative energy,sensors and so on. In this paper, we introduce a new transfer printing method for fabricating metal optics functional devices. This method can directly transfer a metal pattern from a polyethylene terephthalate (PET)supported UV or polydimethylsiloxane (PDMS) pattern to another PET substrate. Purely taking advantage of the anaerobic UV curing adhesive (a-UV) on PET substrate, metal film can be easily peeled off from micro/nano-structured surface. As a result, metal film on the protrusion can be selectively transferred onto the target substrate, to make it the metal functional surface. But which on the bottom can not be transferred. This method provides low cost fabrication of metal thin film devices by avoiding high cost lithography process. Compared with conventional approach, this method can get more smooth rough edges and has wider tolerance range for the original master mold. Future developments and potential applications of this metal transfer method will be addressed.

Chromaticity and color saturation of ultraviolet irradiated poly(vinyl alcohol)-anthocyanin coatings

NASA Astrophysics Data System (ADS)

Mat Nor, N. A.; Aziz, N.; Mohd-Adnan, A. F.; Taha, R. M.; Arof, A. K.

2016-06-01

The purpose of this paper is to evaluate the chromaticity and color saturation of anthocyanin extraction from fruit pericarps of Ixora siamensis in a poly(vinyl alcohol) (PVA) matrix. The colored PVA matrix was exposed to UV-B irradiation for 93 days at UV intensity of 17.55 lux. Anthocyanin colorant has been extracted using methanol acidified with 0.5% trifluoroacetic acid (TFA). Different concentrations of ferulic acid (FA) (0, 1, 2, 3, 4 and 5 wt.%) have been added to the anthocyanin extractions before mixing with PVA to form a coating system. The PVA-anthocyanin-FA mixtures have been coated on glass slides and kept overnight in the dark for curing before exposure to UV-B irradiation. The FA-free sample undergoes more color degradation compared to samples containing FA. The coating with 2% FA has the most stable color with chromaticity of 41% and color saturation of 0.88 compared to other FA containing coats. The FA-free coat exhibits 29% chromaticity and color saturation of 0.38 at the end of the experiment.

Fast, Large-Area, Wide-Bandgap UV Photodetector for Cherenkov Light Detection

NASA Technical Reports Server (NTRS)

Wrbanek, John D.; Wrbanek, Susan Y.

2013-01-01

Due to limited resources available for power and space for payloads, miniaturizing and integrating instrumentation is a high priority for addressing the challenges of manned and unmanned deep space missions to high Earth orbit (HEO), near Earth objects (NEOs), Lunar and Martian orbits and surfaces, and outer planetary systems, as well as improvements to high-altitude aircraft safety. New, robust, and compact detectors allow future instrumentation packages more options in satisfying specific mission goals. A solid-state ultraviolet (UV) detector was developed with a theoretical fast response time and large detection area intended for application to Cherenkov detectors. The detector is based on the wide-bandgap semiconductor zinc oxide (ZnO), which in a bridge circuit can detect small, fast pulses of UV light like those required for Cherenkov detectors. The goal is to replace the role of photomultiplier tubes in Cherenkov detectors with these solid-state devices, saving on size, weight, and required power. For improving detection geometry, a spherical detector to measure high atomic number and energy (HZE) ions from any direction has been patented as part of a larger space radiation detector system. The detector will require the development of solid-state UV photodetectors fast enough (2 ns response time or better) to detect the shockwave of Cherenkov light emitted as the ions pass through a quartz, sapphire, or acrylic ball. The detector must be small enough to fit in the detector system structure, but have an active area large enough to capture enough Cherenkov light from the sphere. The detector is fabricated on bulk single-crystal undoped ZnO. Inter - digitated finger electrodes and contact pads are patterned via photolithography, and formed by sputtered metal of silver, platinum, or other high-conductivity metal.

40 CFR 721.8082 - Polyester polyurethane acrylate.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Polyester polyurethane acrylate. 721... Substances § 721.8082 Polyester polyurethane acrylate. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as polyester polyurethane acrylate...

40 CFR 721.8082 - Polyester polyurethane acrylate.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Polyester polyurethane acrylate. 721... Substances § 721.8082 Polyester polyurethane acrylate. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as polyester polyurethane acrylate...