Surface functionalization of polyamide fiber via dopamine polymerization

NASA Astrophysics Data System (ADS)

Kuang, Xiao-Hui; Guan, Jin-Ping; Tang, Ren-Cheng; Chen, Guo-Qiang

2017-09-01

The oxidative polymerization of dopamine for the functional surface modification of textile fibers has drawn great attention. In this work, the functionalization of polyamide fiber via dopamine polymerization was studied with the aim of the fabrication of hydrophilic and antistatic surface. The conditions of dopamine application were first discussed in the absence of specific oxidants in terms of the apparent color depth of polyamide fiber. Dopamine concentration, pH and time were found to exert great impact on color depth. The highest color depth was achieved at pH 8.5. In the process of modification, polydopamine was deposited onto the surface of polyamide fiber. The modified polyamide fiber displayed a yellowish brown color with excellent wash and light color fastness, and exhibited good hydrophilic, UV protection and antistatic effects. A disadvantage of the present approach was the slow rate of dopamine polymerization and functionalization.

Synthesis of pyrrole-imidazole polyamide oligomers based on a copper-catalyzed cross-coupling strategy.

PubMed

Shiga, Naoki; Takayanagi, Shihori; Muramoto, Risa; Murakami, Tasuku; Qin, Rui; Suzuki, Yuta; Shinohara, Ken-Ichi; Kaneda, Atsushi; Nemoto, Tetsuhiro

2017-05-15

Pyrrole-imidazole (Py-Im) polyamides are useful tools for chemical biology and medicinal chemistry studies due to their unique binding properties to the minor groove of DNA. We developed a novel method of synthesizing Py-Im polyamide oligomers based on a Cu-catalyzed cross-coupling strategy. All four patterns of dimer fragments could be synthesized using a Cu-catalyzed Ullmann-type cross-coupling with easily prepared monomer units. Moreover, we demonstrated that pyrrole dimer, trimer, and tetramer building blocks for Py-Im polyamide synthesis were accessible by combining site selective iodination of the pyrrole/pyrrole coupling adduct. Copyright © 2017 Elsevier Ltd. All rights reserved.

Resistance of polyamide-6 against long time effects of various media at various temperatures

NASA Technical Reports Server (NTRS)

Debski, W.; Przylecka, M.

1988-01-01

During the first phase of tempering of polyamide-6, there are temporary changes which are apparently related to the lamella structure of the material. Test specimens at high temperature show that the mechanical properties of polyamide-6 are changed permanently, and mostly at 80 C. From the results of density tests and X-ray analysis, it follows that these changes depend on environmental influences and differ in gaseous and liquid media. The results of the test specimens of the mechanical properties as a function of temperature and the medium give information about the practical applications of polyamide-6.

Analysis of Wear Behavior of Graphene OXIDE — Polyamide Gears for Engineering Applications

NASA Astrophysics Data System (ADS)

Rajamani, Geetha; Paulraj, Jawahar; Krishnan, Kanny

Recent advances in polymer nanocomposites open a wide range of applications in various industrial sectors. Due to their high potential properties, these materials are replacing the usage of metals for many heavier components in automobile industries. In this experimental work, the tribological performance of Graphene oxide (GO) — Polyamide is investigated against pristine polyamide by fabricating gears for the usage in engineering applications. A gear test rig was developed in-house for analysis to study the specific wear rate and temperature gradient at different conditions of load and speeds. The wear resistance of the polyamide gears with the addition of 0.03wt.% of graphene oxide is better than the pristine polyamide gears and the specific wear rate is reduced significantly. The reduced specific wear rate of these polymer nanocomposite gears is attributed to the superior properties of graphene oxide such as High specific surface area, good adhesion properties and enhanced glass transition temperatures. The GO nanocomposite gear seems to be a potential alternative against conventional gears for engineering applications. Finally, the wear mechanisms and the potential of GO-based polyamide nanocomposite gears were proposed tentatively in the development of transmission gears for engineering applications.

Flame and acid resistant polymide fibers

NASA Technical Reports Server (NTRS)

Stringham, R. S.; Toy, M. S.

1977-01-01

Economical process improves flame resistance and resistance to acids of polyamide fibers, without modifying colors of mechanical properties. Process improves general safety of garments and other items made from polyamide fibers and makes them suitable for applications requiring exposure to oxygen-rich atmosphere or corrosive acids. Halo-olefins are added to surface of fibers by photoadditon in sealed chamber. Process could be used with films and other forms of polyamide.

Synthesis and Characterization of Thianthrene-Based Polyamides

DTIC Science & Technology

1994-07-15

pyrrolidinone using triphenyl phosphite and pyridine. The fused-ring thianthrene-based polyamides were more soluble than analogous poly(thloether amide)s...pyrrolidinone using triphonyl phosphite and pyridine. The fused-ring thianthrene-based polyamides were more soluble than analogous poly(thloether amide)s...sodium hydroxide, and triphenyl phosphite (TPP) was vacuum distilled. UCI and CaCI2 were dried at 180 OC for 48 hours under vacuum. 4,4’-Oxydianiline

Influence of structural variation on nuclear localization of DNA-binding polyamide-fluorophore conjugates.

PubMed

Edelson, Benjamin S; Best, Timothy P; Olenyuk, Bogdan; Nickols, Nicholas G; Doss, Raymond M; Foister, Shane; Heckel, Alexander; Dervan, Peter B

2004-01-01

A pivotal step forward in chemical approaches to controlling gene expression is the development of sequence-specific DNA-binding molecules that can enter live cells and traffic to nuclei unaided. DNA-binding polyamides are a class of programmable, sequence-specific small molecules that have been shown to influence a wide variety of protein-DNA interactions. We have synthesized over 100 polyamide-fluorophore conjugates and assayed their nuclear uptake profiles in 13 mammalian cell lines. The compiled dataset, comprising 1300 entries, establishes a benchmark for the nuclear localization of polyamide-dye conjugates. Compounds in this series were chosen to provide systematic variation in several structural variables, including dye composition and placement, molecular weight, charge, ordering of the aromatic and aliphatic amino-acid building blocks and overall shape. Nuclear uptake does not appear to be correlated with polyamide molecular weight or with the number of imidazole residues, although the positions of imidazole residues affect nuclear access properties significantly. Generally negative determinants for nuclear access include the presence of a beta-Ala-tail residue and the lack of a cationic alkyl amine moiety, whereas the presence of an acetylated 2,4-diaminobutyric acid-turn is a positive factor for nuclear localization. We discuss implications of these data on the design of polyamide-dye conjugates for use in biological systems.

Sugar-Based Polyamides: Self-Organization in Strong Polar Organic Solvents.

PubMed

Rosu, Cornelia; Russo, Paul S; Daly, William H; Cueto, Rafael; Pople, John A; Laine, Roger A; Negulescu, Ioan I

2015-09-14

Periodic patterns resembling spirals were observed to form spontaneously upon unassisted cooling of d-glucaric acid- and d-galactaric acid-based polyamide solutions in N-methyl-N-morpholine oxide (NMMO) monohydrate. Similar observations were made in d-galactaric acid-based polyamide/ionic liquid (IL) solutions. The morphologies were investigated by optical, polarized light and confocal microscopy assays to reveal pattern details. Differential scanning calorimetry was used to monitor solution thermal behavior. Small- and wide-angle X-ray scattering data reflected the complex and heterogeneous nature of the self-organized patterns. Factors such as concentration and temperature were found to influence spiral dimensions and geometry. The distance between rings followed a first-order exponential decay as a function of polymer concentration. Fourier-Transform Infrared Microspectroscopy analysis of spirals pointed to H-bonding between the solvent and the pendant hydroxyl groups of the glucose units from the polymer backbone. Tests on self-organization into spirals of ketal-protected d-galactaric acid polyamides in NMMO monohydrate confirmed the importance of the monosaccharide's pendant free hydroxyl groups on the formation of these patterns. Rheology performed on d-galactaric-based polyamides at high concentration in NMMO monohydrate solution revealed the optimum conditions necessary to process these materials as fibers by spinning. The self-organization of these sugar-based polyamides mimics certain biological materials.

Mechanical properties of injection-molded thermoplastic denture base resins.

PubMed

Hamanaka, Ippei; Takahashi, Yutaka; Shimizu, Hiroshi

2011-03-01

To investigate the mechanical properties of injection-molded thermoplastic denture base resins. Four injection-molded thermoplastic resins (two polyamides, one polyethylene terephthalate, one polycarbonate) and, as a control, a conventional heat-polymerized polymethyl methacrylate (PMMA), were used in this study. The flexural strength at the proportional limit (FS-PL), the elastic modulus, and the Charpy impact strength of the denture base resins were measured according to International Organization for Standardization (ISO) 1567 and ISO 1567:1999/Amd 1:2003. The descending order of the FS-PL was: conventional PMMA > polyethylene terephthalate, polycarbonate > two polyamides. The descending order of the elastic moduli was: conventional PMMA > polycarbonate > polyethylene terephthalate > two polyamides. The descending order of the Charpy impact strength was: polyamide (Nylon PACM12) > polycarbonate > polyamide (Nylon 12), polyethylene terephthalate > conventional PMMA. All of the injection-molded thermoplastic resins had significantly lower FS-PL, lower elastic moduli, and higher or similar impact strength compared to the conventional PMMA. The polyamide denture base resins had low FS-PL and low elastic moduli; one of them possessed very high impact strength, and the other had low impact strength. The polyethylene terephthalate denture base resin showed a moderately high FS-PL, moderate elastic modulus, and low impact strength. The polycarbonate denture base resin had a moderately high FS-PL, moderately high elastic modulus, and moderate impact strength.

Allosteric analysis of glucocorticoid receptor-DNA interface induced by cyclic Py-Im polyamide: a molecular dynamics simulation study.

PubMed

Wang, Yaru; Ma, Na; Wang, Yan; Chen, Guangju

2012-01-01

It has been extensively developed in recent years that cell-permeable small molecules, such as polyamide, can be programmed to disrupt transcription factor-DNA interfaces and can silence aberrant gene expression. For example, cyclic pyrrole-imidazole polyamide that competes with glucocorticoid receptor (GR) for binding to glucocorticoid response elements could be expected to affect the DNA dependent binding by interfering with the protein-DNA interface. However, how such small molecules affect the transcription factor-DNA interfaces and gene regulatory pathways through DNA structure distortion is not fully understood so far. In the present work, we have constructed some models, especially the ternary model of polyamides+DNA+GR DNA-binding domain (GRDBD) dimer, and carried out molecular dynamics simulations and free energy calculations for them to address how polyamide molecules disrupt the GRDBD and DNA interface when polyamide and protein bind at the same sites on opposite grooves of DNA. We found that the cyclic polyamide binding in minor groove of DNA can induce a large structural perturbation of DNA, i.e. a >4 Å widening of the DNA minor groove and a compression of the major groove by more than 4 Å as compared with the DNA molecule in the GRDBD dimer+DNA complex. Further investigations for the ternary system of polyamides+DNA+GRDBD dimer and the binary system of allosteric DNA+GRDBD dimer revealed that the compression of DNA major groove surface causes GRDBD to move away from the DNA major groove with the initial average distance of ∼4 Å to the final average distance of ∼10 Å during 40 ns simulation course. Therefore, this study straightforward explores how small molecule targeting specific sites in the DNA minor groove disrupts the transcription factor-DNA interface in DNA major groove, and consequently modulates gene expression.

Effect of Membrane Permeability on Inflammation and Arterial Stiffness: A Randomized Trial

PubMed Central

Cheng, Yuk Lun; Leung, Chi Bon; Szeto, Cheuk Chun; Chow, Kai Ming; Kwan, Bonnie Ching-Ha; Ng, Esther Siu-Chun; Fok, Queenie Wing-Yi; Poon, Yuet Ling; Yu, Alex Wai-Yin

2010-01-01

Background and objectives: Both larger molecule removal and dialyzer biocompatibility have been implicated in the high-flux hemodialysis (HD)-associated favorable outcome. In an attempt to delineate the effect of membrane permeability, we performed a randomized, crossover study to compare the inflammatory biomarkers, lipid profile, and aortic pulse wave velocity (PWV) of two dialyzers that are composed of identical membranes but with different flux characteristics. Design, setting, participants, & measurements: Stable patients who had anuria and were on low-flux polysulfone membrane were randomly allocated either to HD with high-flux polyamide membrane (group A; 22 patients) or to HD with low-flux polyamide membrane (group B; 24 patients) for 24 weeks, then they were started on 24 weeks of the alternative HD treatment. Apart from the dialyzer, the dialysis prescription remained unchanged. Results: Nineteen patients from group A and 23 patients from group B completed the study. Predialysis β2-microglobulin levels decreased significantly when using the high-flux polyamide membrane. No difference between membranes was observed for serum albumin, high-sensitivity C-reactive protein, fibrinogen, IL-6, triglycerides, HDL cholesterol, LDL cholesterol, and lipoprotein(a) during the study. A significant increase in aortic PWV, a marker of aortic stiffness, was noted after patients switched from high-flux to low-flux polyamide membranes. Similarly, the rate of change in aortic PWV was significantly decreased with the use of the high-flux polyamide membrane. Conclusions: Our findings suggest that dialysis with polyamide membranes with different flux characteristics did not modify the inflammatory indices and lipid profile in stable HD patients; however, a seemingly beneficial effect on aortic stiffness was noted for patients who were maintained on high-flux polyamide membrane. PMID:20203165

Research on mechanical properties of carbon fiber /polyamide reinforced PP composites

NASA Astrophysics Data System (ADS)

Chen, Xinghui; Yu, Qiang; Liu, Lixia; Ji, Wenhua; Yang, Li; Fan, Dongli

2017-10-01

The polyamide composites reinforced by carbon fiber/polypropylene are produced by injection molding processing. The flow abilities and mechanical properties of the CF/PA/PP composite materials are studied by the fusion index instrument and the universal testing machine. The results show that with the content of carbon fiber/polyamide increase, the impact breaking strength and the tensile property of the composite materials increase, which is instructive to the actual injection production of polypropylene products.

An aqueous fluorescent sensor for Pb2+ based on phenothiazine-polyamide.

PubMed

Xie, Yadian; Li, Han; Liu, Xingliang; Wang, Zhaoqian; Lv, Haitang; Cao, Jianfang; Zhang, Chao; Jia, Qiangqiang; Han, Aixia

2018-04-30

A sensitive and selective fluorescent sensor for Pb 2+ ion based on phenothiazine-polyamide was built (named sensor PP). Due to introducing of four diethanolamine groups to polyamide, this sensor was totally water soluble. PP could detect Pb 2+ ion within 1 min in the presence of other metal ions in aqueous solution, the detect limit was 9.11 × 10 -8  M. Copyright © 2018 Elsevier B.V. All rights reserved.

Synthesis and DNA binding properties of 1-(3-aminopropyl)-imidazole-containing triamide f-Im*PyIm: a novel diamino polyamide designed to target 5'-ACGCGT-3'.

PubMed

Satam, Vijay; Babu, Balaji; Porte, Alexander; Savagian, Mia; Lee, Megan; Smeltzer, Thomas; Liu, Yang; Ramos, Joseph; Wilson, W David; Lin, Shicai; Kiakos, Kostantinos; Hartley, John A; Lee, Moses

2012-09-15

A novel diamino/dicationic polyamide f-Im(*)PyIm (5) that contains an orthogonally positioned aminopropyl chain on an imidazole (Im(*)) moiety was designed to target 5'-ACGCGT-3'. The DNA binding properties of the diamino polyamide 5, determined by CD, ΔT(M), DNase I footprinting, SPR, and ITC studies, were compared with those of its monoamino/monocationic counterpart f-ImPyIm (1) and its diamino/dicationic isomer f-ImPy(*)Im (2), which has the aminopropyl group attached to the central pyrrole unit (Py(*)). The results gave evidence for the minor groove binding and selectivity of polyamide 5 for the cognate sequence 5'-ACGCGT-3', and with strong affinity (K(eq)=2.3×10(7) M(-1)). However, the binding affinities varied according to the order: f-ImPy(*)Im (2)>f-ImPyIm (1)≥f-Im(*)PyIm (5) confirming that the second amino group can improve affinity, but its position within the polyamide can affect affinity. Copyright © 2012 Elsevier Ltd. All rights reserved.

21 CFR 177.2450 - Polyamide-imide resins.

Code of Federal Regulations, 2014 CFR

2014-04-01

... polyamide-imide resins are derived from the condensation reaction of substantially equimolar parts of.... 31957-38-7) derived from the condensation reaction of equimolar parts of benzoyl chloride-3,4...

Poly-phenylated diamines and their use as polycondensation monomers in the synthesis of polyamide, poly(amide-imide), and polyimide polymers

NASA Technical Reports Server (NTRS)

Harris, Frank W. (Inventor)

1992-01-01

New polyphenylated polynuclear aromatic diamines, such as 1,3-bis[4-aminophenyl]-2,3,5-triphenylbenzene, a process for their manufacture and their use as polycondensation components for the manufacture of polyamide, polyamide-imide and polyimide polymers are described. The polymers obtained with the aromatic diamines according to the invention are readily soluble, rigid-rod polymers and are distinguished by outstanding modulus, tensile compression strength, energy absorption, coefficient of expansion and electrical properties.

Functional group quantification of polymer nanomembranes with soft x-rays

NASA Astrophysics Data System (ADS)

Sunday, Daniel F.; Chan, Edwin P.; Orski, Sara V.; Nieuwendaal, Ryan C.; Stafford, Christopher M.

2018-03-01

Polyamide nanomembranes are at the heart of water desalination, a process which plays a critical role in clean water production. Improving their efficiency requires a better understanding of the relationship between chemistry, network structure, and performance but few techniques afford compositional information in ultrathin films (<100 nm). Here, we leverage resonant soft x-ray reflectivity, a measurement that is sensitive to the specific chemical bonds in organic materials, to quantify the functional group concentration in these polyamides. We first employ reference materials to establish quantitative relationships between changes in the optical constants and functional group density, and then use the results to evaluate the functional group concentrations of polyamide nanomembranes. We demonstrate that the difference in the amide carbonyl and carboxylic acid group concentrations can be used to calculate the crosslink density, which is shown to vary significantly across three different polyamide chemistries. A clear relationship is established between the functional group density and the permselectivity (α ), indicating that more densely crosslinked materials result in a higher α of the nanomembranes. Finally, measurements on a polyamide/poly(acrylic acid) bilayer demonstrate the ability of this approach to quantify depth-dependent functional group concentrations in thin films.

Flame-resistant textiles

NASA Technical Reports Server (NTRS)

Fogg, L. C.; Stringham, R. S.; Toy, M. S.

1980-01-01

Flame resistance treatment for acid resistant polyamide fibers involving photoaddition of fluorocarbons to surface has been scaled up to treat 10 yards of commercial width (41 in.) fabric. Process may be applicable to other low cost polyamides, polyesters, and textiles.

Crosslinking of aromatic polyamides via pendant propargyl groups

NASA Technical Reports Server (NTRS)

St.clair, A. K.; St.clair, T. L.; Barrick, J. D.; Campbell, F. J.

1980-01-01

Methods for crosslinking N-methyl substituted aromatic polyamides were investigated in an effort to improve the applicability of these polymers as matrix resins for Kavlar trademark fiber composites. High molecular weight polymers were prepared from isophthaloyl dichloride and 4,4'- bis(methylamino)diphenylmethane with varying proportions of the N,N'bispropargyl diamine incorporated as a crosslinking agent. The propargylcontaining diamines were crosslinked thermally and characterized by infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. Attempts were also made to crosslink polyamide films by exposure to ultraviolet light, electron beam, and gamma radiation.

DNA sequence selectivity of hairpin polyamide turn units

PubMed Central

Farkas, Michelle E.; Li, Benjamin C.; Dose, Christian; Dervan, Peter B.

2011-01-01

A class of hairpin polyamides linked by 3,4-diaminobutyric acid, resulting in a β-amine residue at the turn unit, showed improved binding affinities relative to their α-amino-γ-turn analogs for particular sequences. We incorporated β-amino-γ-turns in six-ring polyamides and determined whether there are any sequence preferences under the turn unit by quantitative footprinting titrations. Although there was an energetic penalty for G·C and C·G base pairs, we found little preference for T·A over A·T at the β-amino-γ-turn position. Fluorine and hydroxyl substituted α-amino-γ-turns were synthesized for comparison. Their binding affinities and specificities in the context of six-ring polyamides demonstrated overall diminished affinity and no additional specificity at the turn position. We anticipate that this study will be a baseline for further investigation of the turn subunit as a recognition element for the DNA minor groove. PMID:19349175

Poly-dimethylsiloxane derivates side chains effect on syntan functionalized Polyamide fabric

NASA Astrophysics Data System (ADS)

Migani, V.; Weiss, H.; Massafra, M. R.; Merlo, A.; Colleoni, C.; Rosace, G.

2011-02-01

Poly-dimethylsiloxane (PDMS) polymers finishing of Polyamide-6,6 (PA66) fabrics involves ionic interactions between reactive groups on the PDMS polymers and the ones of the textile fabric. Such interactions could be strengthened by a pretreatment with a fixing agent to promote either ion-ion and H-bonding and ion-dipole forces. These forces could contribute towards the building of substantial PDMS-PA66 systems and the achieving of better adhesion properties to fabrics. Four different silicone polymers based on PDMS were applied on a synthetic tanning agent (syntan) finished Polyamide-6,6 fabric under acid conditions. Soxhlet extraction method and ATR FT-IR technique were used to investigate the application conditions. The finishing parameters such as pH and temperature together with fastness, mechanical and performance properties of the treated samples were studied and related to PDMS side chains effect on syntan functionalized Polyamide fabric.

Synthesis and Properties of Cross-Linked Polyamide Aerogels

NASA Technical Reports Server (NTRS)

Williams, Jarrod C.; Meador, Mary Ann; McCorkle, Linda

2015-01-01

We report the first synthesis of cross-linked polyamide aerogels through step growth polymerization using a combination of diamines, diacid chloride and triacid chloride. Polyamide oligomers endcapped with amines are prepared as stable solutions in N-methylpyrrolidinone from several different diamine precursors and 1,3-benzenedicarbonyl dichloride. Addition of 1,3,5-benzenetricarbonyl trichloride yields gels which form in under five minutes according to the scheme shown. Solvent exchange of the gels into ethanol, followed by drying using supercritical CO2 extraction gives colorless aerogels with densities around 0.1 to 0.2 gcm3. Thicker monolithes of the polyamide aerogels are stiff and strong, while thin films of certain formulations are highly flexible, durable, and even translucent. These materials may have use as insulation for deployable space structures, rovers, habitats or extravehicular activity suits as well as in many terrestrial applications. Strucure property relationships of the aerogels, including surface area, mechanical properties, and thermal conductivity will be discussed.

Fragrance release from the surface of branched poly (amide)s.

PubMed

Aulenta, Francesca; Drew, Michael G B; Foster, Alison; Hayes, Wayne; Rannard, Steven; Thornthwaite, David W; Youngs, Tristan G A

2005-01-31

Enzymes are powerful tools in organic synthesis that are able to catalyse a wide variety of selective chemical transformations under mild and environmentally friendly conditions. Enzymes such as the lipases have also found applications in the synthesis and degradation of polymeric materials. However, the use of these natural catalysts in the synthesis and the post-synthetic modification of dendrimers and hyperbranched molecules is an application of chemistry yet to be explored extensively. In this study the use of two hydrolytic enzymes, a lipase from Candida cylindracea and a cutinase from Fusarium solani pisii, were investigated in the selective cleavage of ester groups situated on the peripheral layer of two families of branched polyamides. These branched polyamides were conjugated to simple fragrances citronellol and L-menthol via ester linkages. Hydrolysis of the ester linkage between the fragrances and the branched polyamide support was carried out in aqueous buffered systems at slightly basic pH values under the optimum operative conditions for the enzymes used. These preliminary qualitative investigations revealed that partial cleavage of the ester functionalities from the branched polyamide support had occurred. However, the ability of the enzymes to interact with the substrates decreased considerably as the branching density, the rigidity of the structure and the bulkiness of the polyamide-fragrance conjugates increased.

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.

Effect of fiber content on flexural properties of glass fiber-reinforced polyamide-6 prepared by injection molding.

PubMed

Nagakura, Manamu; Tanimoto, Yasuhiro; Nishiyama, Norihiro

2017-07-26

The use of non-metal clasp denture (NMCD) materials may seriously affect the remaining tissues because of the low rigidity of NMCD materials such as polyamides. The purpose of this study was to develop a high-rigidity glass fiber-reinforced thermoplastic (GFRTP) composed of E-glass fiber and polyamide-6 for NMCDs using an injection molding. The reinforcing effects of fiber on the flexural properties of GFRTPs were investigated using glass fiber content ranging from 0 to 50 mass%. Three-point bending tests indicated that the flexural strength and elastic modulus of a GFRTP with a fiber content of 50 mass% were 5.4 and 4.7 times higher than those of unreinforced polyamide-6, respectively. The result showed that the physical characteristics of GFRTPs were greatly improved by increasing the fiber content, and the beneficial effects of fiber reinforcement were evident. The findings suggest that the injection-molded GFRTPs are adaptable to NMCDs because of their excellent mechanical properties.

Swelling and morphology of the skin layer of polyamide composite membranes: an atomic force microscopy study.

PubMed

Freger, Viatcheslav

2004-06-01

The paper introduces a new methodology for studying polyamide composite membranes for reverse osmosis (RO) and nanofiltration (NF) in liquid environments. The methodology is based on atomic force microscopy of the active layer, which had been separated from the support and placed on a solid substrate. The approach was employed to determine the thickness, interfacial morphology, and dimensional changes in solution (swelling) of polyamide films. The face (active) and back (facing the support) surfaces of the RO films appeared morphologically similar, in agreement with the recently proposed model of skin formation. Measured thickness and swelling data in conjunction with the intrinsic permeability of the membranes suggest that the selective barrier in RO membrane constitutes only a fraction of the polyamide skin, whereas NF membranes behave as nearly uniform films. For NF membranes, there was reasonable correlation between the changes in the swelling and in the permeability of the membrane and the salinity and pH of the feed.

Laser surface treatment of polyamide and NiTi alloy and the effects on mesenchymal stem cell response

NASA Astrophysics Data System (ADS)

Waugh, D. G.; Lawrence, J.; Shukla, P.; Chan, C.; Hussain, I.; Man, H. C.; Smith, G. C.

2015-07-01

Mesenchymal stem cells (MSCs) are known to play important roles in development, post-natal growth, repair, and regeneration of mesenchymal tissues. What is more, surface treatments are widely reported to affect the biomimetic nature of materials. This paper will detail, discuss and compare laser surface treatment of polyamide (Polyamide 6,6), using a 60 W CO2 laser, and NiTi alloy, using a 100 W fiber laser, and the effects of these treatments on mesenchymal stem cell response. The surface morphology and composition of the polyamide and NiTi alloy were studied by scanning electron microscopy (SEM) and X-ray photoemission spectroscopy (XPS), respectively. MSC cell morphology cell counting and viability measurements were done by employing a haemocytometer and MTT colorimetric assay. The success of enhanced adhesion and spreading of the MSCs on each of the laser surface treated samples, when compared to as-received samples, is evidenced in this work.

Crystallization behavior of polyamide-6 microcellular nanocomposites

Treesearch

Mingjun Yuan; Lih-Sheng Turng; Shaoqin Gong; Andreas Winardi

2004-09-01

The crystallization behaviors of polyamide-6 (PA-6) and its nanocomposites undergoing the microcellular injection molding process are studied using Transmission Electron Microscopy (TEM), X-ray Diffractometer (XRD), Polarized Optical Microscopy (POM), and Differential Scanning Calorimetry (DSC). The relationships among the morphology, the mechanical property of the...

3D morphological characterization of the polyamide active layer of RO and NF membranes using TEM and soft X-ray scattering

NASA Astrophysics Data System (ADS)

Culp, Tyler; Paul, Mou; Roy, Abhishek; Rosenberg, Steve; Behr, Michael; Kumar, Manish; Gomez, Enrique; Penn State Team; Dow Team

Polyamide-based thin-film composite (TFC) membranes used for reverse osmosis (RO) and nanofiltration (NF) separation processes are at the forefront of water desalination and purification technologies due to their high salt rejection, high energy efficiency, and ease of operation. Nevertheless, in spite of the benefits of RO and NF membranes, many open questions about the internal nanostructure of the membrane active layer remain, such as the dispersion and distribution of acid functional groups. We demonstrate that resonant soft X-ray scattering (RSOXS), where the X-ray energy is tuned to absorption edges of the constituent materials, is a powerful tool to examine the microstructure of the polyamide layer. In conjunction with complementary techniques such as transmission electron microscopy (TEM), where tomography is used to obtain a 3D reconstruction of the polyamide active layer, the effect of cross-linking can be quantified in 3D for a systematic series of membranes. This relationship can then be applied to a series of commercially available RO and NF membranes where the effect of polyamide cross-linking on their respective structure and water transport properties can be evaluated. The combination of RSOXS with traditional characterization tools provides a strategy for linking the chemical structure to the morphology and water transport properties of RO and NF membranes.

Phosphorus Moieties Make Polymers Less Flammable

NASA Technical Reports Server (NTRS)

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

1992-01-01

Phosphorus incorporated into epoxies and polyamides via curing agent. According to report, use of 1-(di(2-chloroethoxyphosphinyl)methyl)-2,4- and -2,6-diaminobenzene (DCEPD) as curing agent for epoxies and polyamides makes these polymers more fire-retardant than corresponding polymers made with standard curing agents not containing phosphorus.

21 CFR 878.5020 - Nonabsorbable polyamide surgical suture.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Nonabsorbable polyamide surgical suture. 878.5020 Section 878.5020 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.5020 Nonabsorbable...

21 CFR 878.5020 - Nonabsorbable polyamide surgical suture.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Nonabsorbable polyamide surgical suture. 878.5020 Section 878.5020 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.5020 Nonabsorbable...

21 CFR 878.5020 - Nonabsorbable polyamide surgical suture.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Nonabsorbable polyamide surgical suture. 878.5020 Section 878.5020 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.5020 Nonabsorbable...

21 CFR 878.5020 - Nonabsorbable polyamide surgical suture.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Nonabsorbable polyamide surgical suture. 878.5020 Section 878.5020 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.5020 Nonabsorbable...

UV excimer laser and low temperature plasma treatments of polyamide materials

NASA Astrophysics Data System (ADS)

Yip, Yiu Wan Joanne

Polyamides have found widespread application in various industrial sectors, for example, they are used in apparel, home furnishings and similar uses. However, the requirements for high quality performance products are continually increasing and these promote a variety of surface treatments for polymer modification. UV excimer laser and low temperature plasma treatments are ideally suited for polyamide modification because they can change the physical and chemical properties of the material without affecting its bulk features. This project aimed to study the modification of polyamides by UV excimer laser irradiation and low temperature plasma treatment. The morphological changes in the resulting samples were analysed by scanning electron microscopy (SEM) and tapping mode atomic force microscopy (TM-AFM). The chemical modifications were studied by x-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and chemical force microscopy (CFM). Change in degree of crystallinity was examined by differential scanning calorimetry (DSC). After high-fluence laser irradiation, topographical results showed that ripples of micrometer size form on the fibre surface. By contrast, sub-micrometer size structures form on the polyamide surface when the applied laser energy is well below its ablation threshold. After high-fluence laser irradiation, chemical studies showed that the surface oxygen content of polyamide is reduced. A reverse result is obtained with low-fluence treatment. The DSC result showed no significant change in degree of crystallinity in either high-fluence or low-fluence treated samples. The same modifications in polyamide surfaces were studied after low temperature plasma treatment with oxygen, argon or tetrafluoromethane gas. The most significant result was that the surface oxygen content of polyamide increased after oxygen and argon plasma treatments. Both treatments induced many hydroxyl (-OH) and carboxylic acid (-COOH) functional groups, which increased water absorption. However, after tetrafluoromethane plasma treatment it was found that the -CF, -CF2 and -CF3 groups were introduced to the polyamide surface and this enhanced the hydrophobicity of the fabric. Suggested explanations are given of the mechanisms that produce the structure of the polyamide after the processes of laser irradiation (both high- and low-fluence) and plasma treatment. The fundamental approach used in modelling was considered the temperature profile of the material during the treatment. The development of high-fluence induced structures was caused by elevated temperatures in the subsurface volume and preexisting stress caused by fiber extrusion. The structure formation under LF laser irradiation was determined by thermal effect accompanied by the optical phenomenon of interference. Ripple structures formed by plasma were closely related to physical or chemical etching. Possible applications of plasma and laser technologies in the textile and clothing industries are considered. Oxygen plasma seems to be the best candidate to improve the wettability of the fabric, while tetrafluoromethane plasma can be applied to produce a water repellent surface. Surface treatments including CF4 plasma, high-fluence and low-fluence laser treatments produce a deeper color in disperse dyed fabrics using the same amount of dyestuff as chemicals like leveling agents and dyestuff can be reduced during the textile manufacturing process. UV laser and low temperature plasma modification processes are promising techniques for polymer/fabric surface modification and have industrial potential as they are environmentally friendly dry processes which do not involve any solvents.

Prediction of mechanical property loss in polyamide during immersion in sea water

NASA Astrophysics Data System (ADS)

Le Gac, Pierre Yves; Arhant, Mael; Le Gall, Maelenn; Burtin, Christian; Davies, Peter

2016-05-01

It is well known that the water absorption in polyamide leads to a large reduction in the mechanical properties of the polymer, which is induced by the plasticization of the amorphous phase. However, predicting such a loss in a marine environment is not straightforward, especially when thick samples are considered. This study presents a modeling study of the water absorption in polyamide 6 based on the free volume theory. Using this modeling coupled with a description of the stress yield changes with Tg, it is possible to predict the long term behavior of thick samples when immersed in sea water. Reliability of the prediction is checked by a comparison with experimental results.

21 CFR 878.5020 - Nonabsorbable polyamide surgical suture.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Nonabsorbable polyamide surgical suture. 878.5020 Section 878.5020 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... Industry and FDA.” See § 878.1(e) for the availability of this guidance document. [56 FR 24685, May 31...

Thermodynamic factors in partitioning and rejection of organic compounds by polyamide composite membranes.

PubMed

Ben-David, Adi; Oren, Yoram; Freger, Viatcheslav

2006-11-15

The paper analyzes the mechanism of partitioning and rejection of organic solutes by polyamide membranes for reverse osmosis and nanofiltration. The partitioning of homologous series of alcohols and polyols, in which polarity changes with size in opposite ways, was measured using attenuated total reflection IR spectroscopy. The results show that the partitioning of polyols monotonously decreases with size, whereas for alcohols it is not monotonous and slightly decreases for small C1-C3 alcohols followed by a sharp increase for larger alcohols. These results may be explained by assuming a heterogeneous structure of polyamide comprising a hydrophobic polyamide matrix and a polar internal aqueous phase. The partitioning data could consistently explain the results of rejection in standard filtration experiments. They clearly demonstrate that high/low partitioning may play a significant role in achieving a low/high rejection of organics. In particular, this points to the need to account for the partitioning effect while using molecular probes such as polyols or sugars for estimating the effective "pore" size or molecular weight cutoff of a membrane and for choosing/developing organic-rejecting membranes.

Effects of reuse and bleach/formaldehyde reprocessing on polysulfone and polyamide hemodialyzers.

PubMed

Cornelius, Rena M; McClung, W Glenn; Barre, Paul; Esguerra, Fe; Brash, John L

2002-01-01

The surface features, morphology, and blood interactions of fibers from pristine, bleach/formaldehyde reprocessed, and reused Fresenius Polysulfone High Flux (Hemoflow F80B) hemodialyzers and Gambro Polyflux 21S Polyamide hemodialyzers have been studied. SEM images of fibers from both hemodialyzer types revealed a dense skin layer on the inner surface and a relatively thick porous layer on the outer surface. The 21S polyamide support layer consisted of interconnected highly porous structures. Environmental scanning electron microscopy and atomic force microscopy images of both membrane types showed alterations in morphology due to reprocessing and reuse; however the changes were more marked for the 21S polyamide dialyzers. Fluorescence microscopy images showed only minimal fluorescence associated with the fibers after patient use and reprocessing, suggesting that blood derived deposits were removed by processing. The protein layers formed on pristine and reused hemodialyzer membranes during clinical use were studied using SDS-PAGE and immunoblotting. Before bleach/formaldehyde treatment, protein layers of considerable amount and complexity were found on the blood side of singly and multiply used dialyzers. Proteins adsorbed on the dialysate side were predominantly in the molecular mass region below 30 kDa. However, some higher molecular mass proteins were detected on the dialysate side of the 21 S polyamide dialyzers. Very little protein was detected on dialyzers that were treated with bleach/formaldehyde after dialysis, regardless of whether they had been used/reprocessed once or 12 times.

Oxygen transport as a structure probe for heterogeneous polymeric systems

NASA Astrophysics Data System (ADS)

Hu, Yushan

Although permeability of small molecules is often measured as an important performance property, deeper analysis of the transport characteristics provides insight into polymer structure, especially if used in combination with other characterization techniques. Transport of small gas molecules senses the permeable amorphous structure and probes the nature of free volume. This work focuses on oxygen transport, supplemented with other methods of physical analysis, as a probe for: (1) the nature of free volume and crystalline morphology in the crystallized glassy state, (2) the nature of free volume and hierarchical structure in liquid crystalline polymers, and (3) the role of dispersed polyamide phase geometry on oxygen barrier properties of poly(ethylene terephthalate) (PET)/polyamide blends. In the first part, the improvement in oxygen-barrier properties of glassy polyesters by crystallization was examined. Examples included poly(ethylene naphthalate) (PEN), and a copolymer based on PET in which 55 mol% terephthalate was replaced with 4,4'-bibenzoate. Explanation of the unexpectedly high solubility of crystallized PEN required a two-phase transport model consisting of an impermeable crystalline phase of constant density and a permeable amorphous phase of variable density. The resulting relationship between oxygen solubility and amorphous phase density was consistent with free volume concepts of gas sorption. In the second part, oxygen barrier properties of liquid crystalline (LC) polyesters based on poly(diethylene glycol 4,4'-bibenzoate) (PDEGBB) were studied. This study extended the 2-phase transport model for oxygen transport of non-LC crystalline polymers to a smectic LCP. It was possible to systematically vary the solid state structure of (PDEGBB) from LC glass to crystallized LC glass. The results were consistent with a liquid crystalline state intermediate between the permeable amorphous glass and the impermeable 3-dimensional crystal. In this interpretation, LC order naturally led to inherently low gas solubility. In the third part, improvement of gas-barrier properties of poly(ethylene terephthalate) (PET) by blending with an aromatic polyamide, either poly(m-xylylene adipamide) (MXD6) or a copolyamide based on MXD6 in which 12 mol% adipamide was replaced with isophthalamide (MXD6-12I), was studied. Aromatic polyamides provided higher barrier than aliphatic polyamides, and unlike aliphatic polyamides, the aromatic polyamides retained high barrier under conditions of high humidity, making them more suitable for beverage packaging applications. (Abstract shortened by UMI.)

Fire resistant polyamide based on 1-(diorganooxyphosphonyl)methyl-2,4- and -2,6diamino benzene

NASA Technical Reports Server (NTRS)

Mikroyannidis, J. A. (Inventor); Kourtides, D. A. (Inventor)

1986-01-01

1-(Diorganooxyphosphonyl)methyl2,4- and-2,6diamino benzenes are reacted with polyacylhalides and optionally comonomers to produce polyamides which have desirable heat and fire resistance properties. These polymers are used to form fibers and fabrics where fire resistance properties are important, e.g., aircraft equipment and structures.

Synthesis of mouse centromere-targeted polyamides and physico-chemical studies of their interaction with the target double-stranded DNA.

PubMed

Nozeret, Karine; Bonan, Marc; Yarmoluk, Serguiy M; Novopashina, Darya S; Boutorine, Alexandre S

2015-09-01

Synthetic minor groove-binding pyrrole-imidazole polyamides labeled by fluorophores are promising candidates for fluorescence imaging of double-stranded DNA in isolated chromosomes or fixed and living cells. We synthesized nine hairpin and two head-to-head tandem polyamides targeting repeated sequences from mouse major satellites. Their interaction with synthetic target dsDNA has been studied by physico-chemical methods in vitro before and after coupling to various fluorophores. Great variability in affinities and fluorescence properties reveals a conclusion that these properties do not only rely on recognition rules, but also on other known and unknown structural factors. Individual testing of each probe is needed before cellular applications. Copyright © 2015 Elsevier Ltd. All rights reserved.

Polyimide/metal composite films via in situ decomposition of inorganic additives - Soluble polyimide versus polyimide precursor

NASA Technical Reports Server (NTRS)

Rancourt, J. D.; Porta, G. M.; Moyer, E. S.; Madeleine, D. G.; Taylor, L. T.

1988-01-01

Polyimide-metal oxide (Co3O4 or CuO) composite films have been prepared via in situ thermal decomposition of cobalt (II) chloride or bis(trifluoroacetylacetonato)copper(II). A soluble polyimide (XU-218) and its corresponding prepolymer (polyamide acid) were individually employed as the reaction matrix. The resulting composites exhibited a greater metal oxide concentration at the air interface with polyamide acid as the reaction matrix. The water of imidization that is released during the concurrent polyamide acid cure and additive decomposition is believed to promote metal migration and oxide formation. In contrast, XU-218 doped with either HAuCl4.3H2O or AgNO3 yields surface gold or silver when thermolyzed (300 C).

Development of programmable small DNA-binding molecules with epigenetic activity for induction of core pluripotency genes.

PubMed

Pandian, Ganesh N; Ohtsuki, Akimichi; Bando, Toshikazu; Sato, Shinsuke; Hashiya, Kaori; Sugiyama, Hiroshi

2012-04-15

Epigenetic modifications that govern the gene expression are often overlooked with the design of artificial genetic switches. N-Methylpyrrole-N-methylimidazole (PI) hairpin polyamides are programmable small DNA binding molecules that have been studied in the context of gene regulation. Recently, we synthesized a library of compounds by conjugating PI polyamides with SAHA, a chromatin-modifier. Among these novel compounds, PI polyamide-SAHA conjugate 1 was shown to epigenetically activate pluripotency genes in mouse embryonic fibroblasts. Here, we report the synthesis of the derivatives of conjugate 1 and demonstrate that these epigenetically active molecules could be developed to improve the induction of pluripotency factors. Copyright © 2012 Elsevier Ltd. All rights reserved.

Effect of surface treatment methods on the shear bond strength of auto-polymerized resin to thermoplastic denture base polymer.

PubMed

Koodaryan, Roodabeh; Hafezeqoran, Ali

2016-12-01

Polyamide polymers do not provide sufficient bond strength to auto-polymerized resins for repairing fractured denture or replacing dislodged denture teeth. Limited treatment methods have been developed to improve the bond strength between auto-polymerized reline resins and polyamide denture base materials. The objective of the present study was to evaluate the effect of surface modification by acetic acid on surface characteristics and bond strength of reline resin to polyamide denture base. 84 polyamide specimens were divided into three surface treatment groups (n=28): control (N), silica-coated (S), and acid-treated (A). Two different auto-polymerized reline resins GC and Triplex resins were bonded to the samples (subgroups T and G, respectively, n=14). The specimens were subjected to shear bond strength test after they were stored in distilled water for 1 week and thermo-cycled for 5000 cycles. Data were analyzed with independent t-test, two-way analysis of variance (ANOVA), and Tukey's post hoc multiple comparison test (α=.05). The bond strength values of A and S were significantly higher than those of N ( P <.001 for both). However, statistically significant difference was not observed between group A and group S. According to the independent Student's t-test, the shear bond strength values of AT were significantly higher than those of AG ( P <.001). The surface treatment of polyamide denture base materials with acetic acid may be an efficient and cost-effective method for increasing the shear bond strength to auto-polymerized reline resin.

Water-assisted compounding of cellulose nanocrystals into polyamide 6 for use as a nucleating agent for microcellular foaming

Treesearch

Jun Peng; Philip J. Walsh; Ronald C. Sabo; Lih-Sheng Turng; Craig M. Clemons

2016-01-01

Cellulose nanocrystals (CNCs) are a biorenewable filler and can be an excellent nucleating agent for the development of microcellular foamed polymeric nanocomposites. However, their relatively low degradation temperature limits their use with engineering resins like polyamide 6 (PA6) in typical melt processing techniques such as injection molding, compounding, and...

Applications of polyamide/cellulose fiber/wollastonite composites for microcellular injection molding

Treesearch

Herman Winata; Lih-Sheng Turng; Daniel F. Caulfield; Tom Kuster; Rick Spindler; Rod Jacobson

2003-01-01

In this study, a cellulose-fiber-reinforced Polyamide-6 (PA-6) composite, a hybrid composite (PA-6/cellulose/Wollastonite), and the neat PA-6 resin were injection molded into ASTM test–bar samples with conventional and microcellular injection molding. The impact and tensile strengths of molded samples were measured and the Scanning Electron Microscopy (SEM) images were...

Water reclamation during drinking water treatments using polyamide nanofiltration membranes on a pilot scale.

PubMed

Kukučka, Miroslav; Kukučka, Nikoleta; Habuda-Stanić, Mirna

2016-09-01

The aim of this study was to investigate the performances of polyamide nanofiltration membranes during water reclamation. The study was conducted using nanofiltration concentrates obtained from two different nanofiltration drinking water treatment plants placed in the northern part of Serbia (Kikinda and Zrenjanin). Used nanofiltration concentrates contained high concentrations of arsenic (45 and 451 μg/L) and natural organic matter (43.1 and 224.40 mgKMnO4/L). Performances of polyamide nanofiltration membranes during water reclamation were investigated under various fluxes and transmembrane pressures in order to obtain drinking water from nanofiltration concentrates and, therefore, reduce the amount of produced concentrates and minimize the waste that has to be discharged in the environment. Applied polyamide nanofiltration membranes showed better removal efficiency during water reclamation when the concentrate with higher content of arsenic and natural organic matter was used while the obtained permeates were in accordance with European regulations. This study showed that total concentrate yield can be reduced to ~5 % of the optimum flux value, in both experiments. The obtained result for concentrate yield under the optimum flux presents considerable amount of reclaimed drinking water and valuable reduced quantity of produced wastewater.

Interaction of fluorescently labeled pyrrole-imidazole polyamide probes with fixed and living murine and human cells.

PubMed

Nozeret, Karine; Loll, François; Cardoso, Gildas Mouta; Escudé, Christophe; Boutorine, Alexandre S

2018-06-01

Pericentromeric heterochromatin plays important roles in controlling gene expression and cellular differentiation. Fluorescent pyrrole-imidazole polyamides targeting murine pericentromeric DNA (major satellites) can be used for the visualization of pericentromeric heterochromatin foci in live mouse cells. New derivatives targeting human repeated DNA sequences (α-satellites) were synthesized and their interaction with target DNA was characterized. The possibility to use major satellite and α -satellite binding polyamides as tools for staining pericentromeric heterochromatin was further investigated in fixed and living mouse and human cells. The staining that was previously observed using the mouse model was further characterized and optimized, but remained limited regarding the fluorophores that can be used. The promising results regarding the staining in the mouse model could not be extended to the human model. Experiments performed in human cells showed chromosomal DNA staining without selectivity. Factors limiting the use of fluorescent polyamides, in particular probe aggregation in the cytoplasm, were investigated. Results are discussed with regards to structure and affinity of probes, density of target sites and chromatin accessibility in both models. Copyright © 2018 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.

Polyamide nanocapsules and nano-emulsions containing Parsol® MCX and Parsol® 1789: in vitro release, ex vivo skin penetration and photo-stability studies.

PubMed

Hanno, Ibrahim; Anselmi, Cecilia; Bouchemal, Kawthar

2012-02-01

To prepare polyamide nanocapsules for skin photo-protection, encapsulating α-tocopherol, Parsol®MCX (ethylhexyl methoxycinnamate) and/or Parsol®1789 (butyl methoxydibenzoylmethane). Nanocapsules were obtained by combining spontaneous emulsification and interfacial polycondensation reaction between sebacoyl chloride and diethylenetriamine. Nano-emulsions used as control were obtained by the same process without monomers. The influence of carrier on release rate was studied in vitro with a membrane-free model. Epidermal penetration of encapsulated sunscreens was ex vivo evaluated using Franz diffusion cells. Ability of encapsulated sunscreens to improve photo-stability was verified by comparing percentage of degradation after UV radiation exposure. Sunscreen-containing nanocapsules (260-400 nm) were successfully prepared; yield of encapsulation was >98%. Parsol®MCX and Parsol®1789 encapsulation led to decreased release rate by up to 60% in comparison with nano-emulsion and allowed minimum penetration through pig ear epidermis. Presence of polyamide shell protected encapsulated sunscreen filters from photo-degradation without affecting their activity. Encapsulation of Parsol®MCX and Parsol®1789 into oil-core of polyamide nanocapsules allowed protection from photo-degradation, controlled release from nanocapsules, and limited penetration through pig ear epidermis.

Synthesis and Thermal and Photo Behaviors of New Polyamide/Organocaly Nanocomposites Containing Para Phenylenediacrylic Moiety

NASA Astrophysics Data System (ADS)

Faghihi, Khalil; Soleimani, Masoumeh; Shabanian, Meisam; Abootalebi, Ashraf Sadat

2011-06-01

New type of aromatic polyamide/montmorillonite nanocomposites were produced using solution process in N-methyl-2-pyrolidone. Amide chains were synthesized from 4,4'-diaminodiphenyl sulfone and p-phenylenediacrylic acid in N-methyl-2-pyrolidone. The resulting nanocomposite films containing 5-15 mass % of organoclay were characterized for FT-IR, scanning electronmicroscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), optical transparency and water absorption measurements. The distribution of organoclay and nanostructure of the composites were investigated by (XRD) and SEM analyses. Thermogravimetric analysis indicated an increase in thermal stability of nanocomposites as compared to pristine polyamide. The percentage optical transparency and water absorption of these hybrids was found to be much reduced upon the addition of modified layered silicate indicating decreased permeability.

Recognition by nonaromatic and stereochemical subunit-containing polyamides of the four Watson-Crick base pairs in the DNA minor groove.

PubMed

Zhang, Hong-Fei; Wu, Yan-Ling; Jiang, Shi-Kun; Wang, Pu; Sugiyama, Hiroshi; Chen, Xing-Lai; Zhang, Wen; Ji, Yan-Juan; Guo, Chuan-Xin

2012-06-18

In order to develop an optimal subunit as a T-recognition element in hairpin polyamides, 15 novel chirality-modified polyamides containing (R)-α,β-diaminopropionic acid ((R) β α-NH 2), (S)-α,β-diaminopropionic acid ((S) β α-NH 2), (1R,3S)-3-aminocyclopentanecarboxylic acid ((RS) Cp), (1S,3R)-3-amino-cyclopentanecarboxylic acid ((RS) Cp), (1R,3R)-3-aminocyclopentanecarboxylic acid ((RR) Cp) and (1S,3S)-3-amino-cyclopentanecarboxylic acid ((SS) Cp) residues were synthesized. Their binding characteristics to DNA sequences 5'-TGCNCAT-3'/3'-ACGN'GTA-5' (N⋅N'=A⋅T, T⋅A, G⋅C and C⋅G) were systemically studied by surface plasmon resonance (SPR) and molecular simulation (MSim) techniques. SPR showed that polyamide 4, AcIm-(S) β α-NH 2-ImPy-γ-ImPy-β-Py-βDp (β/(S) β α-NH 2 pair), bound to a DNA sequence containing a core binding site of 5'-TGCACAT-3' with a dissociation equilibrium constant (K(D) ) of 4.5×10(-8)  m. This was a tenfold improvement in specificity over 5'-TGCTCAT-3' (K(D) =4.5×10(-7)  M). MSim studies supported the SPR results. More importantly, for the first time, we found that chiral 3-aminocyclopentanecarboxylic acids in polyamides can be employed as base readers with only a small decrease in binding affinity to DNA. In particular, SPR showed that polyamide 9 ((RR) Cp/β pair) had a 15-fold binding preference for 5'-TGCTCAT-3' over 5'-TGCACAT-3'. A large difference in standard free energy change for A⋅T over T⋅A was determined (ΔΔG(o) =5.9 kJ mol(-1) ), as was a twofold decrease in interaction energy by MSim. Moreover, a 1:1 stoichiometry (9 to 5'-TGCTCAT-3'/3'-ACGAGTA-5') was shown by MSim to be optimal for the chiral five-membered cycle to fit the minor groove. Collectively, the study suggests that the (S)-α-amino-β-aminopropionic acid and (1R,3R)-3-aminocyclopentanecarboxylic acid can serve as a T-recognition element, and the stereochemistry and the nature of these subunits significantly influence binding properties in these recognition events. Subunit (1R,3R)-3-aminocyclopentanecarboxylic acid broadens our scope to design novel polyamides. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Double-Layer Surface Modification of Polyamide Denture Base Material by Functionalized Sol-Gel Based Silica for Adhesion Improvement.

PubMed

Hafezeqoran, Ali; Koodaryan, Roodabeh

2017-09-21

Limited surface treatments have been proposed to improve the bond strength between autopolymerizing resin and polyamide denture base materials. Still, the bond strength of autopolymerizing resins to nylon polymer is not strong enough to repair the fractured denture effectively. This study aimed to introduce a novel method to improve the adhesion of autopolymerizing resin to polyamide polymer by a double layer deposition of sol-gel silica and N-2-(aminoethyl)-3-aminopropyltrimethoxysilane (AE-APTMS). The silica sol was synthesized by acid-catalyzed hydrolysis of tetraethylorthosilicate (TEOS) as silica precursors. Polyamide specimens were dipped in TEOS-derived sol (TS group, n = 28), and exposed to ultraviolet (UV) light under O 2 flow for 30 minutes. UV-treated specimens were immersed in AE-APTMS solution and left for 24 hours at room temperature. The other specimens were either immersed in AE-APTMS solution (AP group, n = 28) or left untreated (NT group, n = 28). Surface characterization was investigated by fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM). Two autopolymerizing resins (subgroups G and T, n = 14) were bonded to the specimens, thermocycled, and then tested for shear bond strength with a universal testing machine. Data were analyzed with one-way ANOVA followed by Tukey's HSD (α = 0.05). FTIR spectra of treated surfaces confirmed the chemical modification and appearance of functional groups on the polymer. One-way ANOVA revealed significant differences in shear bond strength among the study groups. Tukey's HSD showed that TS T and TS G groups had significantly higher shear bond strength than control groups (p = 0.001 and p < 0.001, respectively). Moreover, bond strength values of AP T were statistically significant compared to controls (p = 0.017). Amino functionalized TEOS-derived silica coating is a simple and cost-effective method for improving the bond strength between the autopolymerizing resin and polyamide denture base. Amino-functionalized silica coating could represent a more applicable and convenient option for improving the repair strength of autopolymerizing resin to polyamide polymer. © 2017 by the American College of Prosthodontists.

Two Dimensional Polyamides Prepared From Unsaturated Carboxylic Acids And Amines.

DOEpatents

McDonald, William F.; Huang, Zhi Heng; Wright, Stacy C.; Danzig, Morris; Taylor, Andrew C.

2002-07-17

A polyamide and a process for preparing the polyamide are disclosed. The process comprises reacting in a reaction mixture a monomer selected from unsaturated carboxylic acids, esters of unsaturated carboxylic acids, anhydrides of unsaturated carboxylic acids, and mixtures thereof, and a first amine to form an intermediate reaction product in the reaction mixture, wherein the first amine is selected from RR.sub.1 NH, RNH.sub.2, RR.sub.1 NH.sub.2.sup.+, RNH.sub.3.sup.+ and mixtures thereof, wherein R and R.sub.1 can be the same or different and each contain between about 1 and 50 carbon atoms and are optionally substituted with heteroatoms oxygen, nitrogen, sulfur, and phosphorus and combinations thereof, and reacting the intermediate reaction product and a second amine to form a polyamide, wherein the second amine is selected from R.sub.2 R.sub.3 NH, R.sub.2 NH.sub.2, R.sub.2 R.sub.3 NH.sub.2.sup.+, R.sub.2 NH.sub.3.sup.+ and mixtures thereof wherein R.sub.2 and R.sub.3 can be the same or different and each contain between about 1 and 50 carbon atoms and are optionally substituted with heteroatoms oxygen, nitrogen, sulfur, and phosphorus and combinations thereof, wherein multiple of the R, R.sub.1, R.sub.2, and R.sub.3 are in vertically aligned spaced relationship along a backbone formed by the polyamide. In one version of the invention, the monomer is selected from maleic anhydride, maleic acid esters, and mixtures thereof. In another version of the invention, the first amine is an alkylamine, such as tetradecylamine, and the second amine is a polyalkylene polyamine, such as pentaethylenehexamine. In yet another version of the invention, the first amine and the second amine are olefinic or acetylenic amines, such as the reaction products of an alkyldiamine and an acetylenic carboxylic acid. The first amine and the second amine may be the same or different depending on the desired polyamide polymer structure.

Friction and wear performance of some thermoplastic polymers and polymer composites against unsaturated polyester

NASA Astrophysics Data System (ADS)

Unal, H.; Mimaroglu, A.; Arda, T.

2006-09-01

Wear experiments have been carried out with a range of unfilled and filled engineering thermoplastic polymers sliding against a 15% glass fibre reinforced unsaturated polyester polymer under 20, 40 and 60 N loads and 0.5 m/s sliding speed. Pin materials used in this experimental investigation are polyamide 66 (PA 66), poly-ether-ether-ketone (PEEK) and aliphatic polyketone (APK), glass fibre reinforced polyamide 46 (PA 46 + 30% GFR), glass fibre reinforced polytetrafluoroethylene (PTFE + 17% GFR), glass fibre reinforced poly-ether-ether-ketone (PEEK + 20% GFR), glass fibre reinforced poly-phylene-sulfide (PPS + 30% GFR), polytetrafluoroethylene filled polyamide 66 (PA 66 + 10% PTFE) and bronze filled pofytetrafluoroethylene (PTFE + 25% bronze) engineering polymers. The disc material is a 15% glass fibre reinforced unsaturated polyester thermoset polymer produced by Bulk Moulding Compound (BMC). Sliding wear tests were carried out on a pin-on-disc apparatus under 0.5 m/s sliding speed and load values of 20, 40 and 60 N. The results showed that the highest specific wear rate is for PPS + 30% GFR with a value of 1 × 10 -11 m 2/N and the lowest wear rate is for PTFE + 17% GFR with a value of 9.41 × 10 -15 m 2/N. For the materials and test conditions of this investigation, apart from polyamide 66 and PA 46 + 30% GFR polymers, the coefficient of friction and specific wear rates are not significantly affected by the change in load value. For polyamide 66 and PA 46 + 30% GFR polymers the coefficient of friction and specific wear rates vary linearly with the variation in load values.

Extending the language of DNA molecular recognition by polyamides: unexpected influence of imidazole and pyrrole arrangement on binding affinity and specificity.

PubMed

Buchmueller, Karen L; Staples, Andrew M; Howard, Cameron M; Horick, Sarah M; Uthe, Peter B; Le, N Minh; Cox, Kari K; Nguyen, Binh; Pacheco, Kimberly A O; Wilson, W David; Lee, Moses

2005-01-19

Pyrrole (Py) and imidazole (Im) polyamides can be designed to target specific DNA sequences. The effect that the pyrrole and imidazole arrangement, plus DNA sequence, have on sequence specificity and binding affinity has been investigated using DNA melting (DeltaT(M)), circular dichroism (CD), and surface plasmon resonance (SPR) studies. SPR results obtained from a complete set of triheterocyclic polyamides show a dramatic difference in the affinity of f-ImPyIm for its cognate DNA (K(eq) = 1.9 x 10(8) M(-1)) and f-PyPyIm for its cognate DNA (K(eq) = 5.9 x 10(5) M(-1)), which could not have been anticipated prior to characterization of these compounds. Moreover, f-ImPyIm has a 10-fold greater affinity for CGCG than distamycin A has for its cognate, AATT. To understand this difference, the triamide dimers are divided into two structural groupings: central and terminal pairings. The four possible central pairings show decreasing selectivity and affinity for their respective cognate sequences: -ImPy > -PyPy- > -PyIm- approximately -ImIm-. These results extend the language of current design motifs for polyamide sequence recognition to include the use of "words" for recognizing two adjacent base pairs, rather than "letters" for binding to single base pairs. Thus, polyamides designed to target Watson-Crick base pairs should utilize the strength of -ImPy- and -PyPy- central pairings. The f/Im and f/Py terminal groups yielded no advantage for their respective C/G or T/A base pairs. The exception is with the -ImPy- central pairing, for which f/Im has a 10-fold greater affinity for C/G than f/Py has for T/A.

Study of ionizing radiation on the properties of polyamide 6 with fiberglass reinforcement

NASA Astrophysics Data System (ADS)

Pinto, Clovis; Silva, Leonardo G. Andrade e.

2007-11-01

The use of polymers reinforced with fiberglass is becoming more and more common in the switches for household industries. These compounds perform a good tension resistance to the impact and the humidity absorption being used at the present time and also are in the automobile industry in parts underneath the hood, especially in the radiator frames. The aim of this work is to study the effect of ionizing radiation on the properties of polyamide 6 with fiberglass reinforcement and undergone to different irradiation doses. Samples were prepared and irradiated on JOB 188 accelerator with an electron beam energy of 1.5 MeV in air with different doses and a dose rate of 27.99 kGy/h. Afterward, the properties of the non-irradiated and irradiated polyamide 6 with fiberglass reinforcement were evaluated.

Heat resistant protective hand covering

NASA Technical Reports Server (NTRS)

Sidman, K. R.; Arons, I. J. (Inventor)

1984-01-01

The heat resistant, protective glove is made up of first and second shell sections which define a palm side and a backside, respectively. The first shell section is made of a twill wave fabric of a temperature-resistant aromatic polyamide fiber. The second shell section is made of a knitted fabric of a temperature-resistant aromatic polyamide fiber. The first and second shell sections are secured to one another, e.g., by sewing, to provide the desired glove configuration and an opening for insertion of the wearer's hand. The protective glove also includes a first liner section which is secured to and overlies the inner surface of the first shell section and is made of a felt fabric of a temperature-resistant aromatic polyamide fiber and has a flame resistant, elastomenic coating on the surface facing and overlying the inner surface of the first shell section.

Comparison of Three Different Methods for Pile Integrity Testing on a Cylindrical Homogeneous Polyamide Specimen

NASA Astrophysics Data System (ADS)

Lugovtsova, Y. D.; Soldatov, A. I.

2016-01-01

Three different methods for pile integrity testing are proposed to compare on a cylindrical homogeneous polyamide specimen. The methods are low strain pile integrity testing, multichannel pile integrity testing and testing with a shaker system. Since the low strain pile integrity testing is well-established and standardized method, the results from it are used as a reference for other two methods.

Partitioning of Alkali Metal Salts and Boric Acid from Aqueous Phase into the Polyamide Active Layers of Reverse Osmosis Membranes.

PubMed

Wang, Jingbo; Kingsbury, Ryan S; Perry, Lamar A; Coronell, Orlando

2017-02-21

The partition coefficient of solutes into the polyamide active layer of reverse osmosis (RO) membranes is one of the three membrane properties (together with solute diffusion coefficient and active layer thickness) that determine solute permeation. However, no well-established method exists to measure solute partition coefficients into polyamide active layers. Further, the few studies that measured partition coefficients for inorganic salts report values significantly higher than one (∼3-8), which is contrary to expectations from Donnan theory and the observed high rejection of salts. As such, we developed a benchtop method to determine solute partition coefficients into the polyamide active layers of RO membranes. The method uses a quartz crystal microbalance (QCM) to measure the change in the mass of the active layer caused by the uptake of the partitioned solutes. The method was evaluated using several inorganic salts (alkali metal salts of chloride) and a weak acid of common concern in water desalination (boric acid). All partition coefficients were found to be lower than 1, in general agreement with expectations from Donnan theory. Results reported in this study advance the fundamental understanding of contaminant transport through RO membranes, and can be used in future studies to decouple the contributions of contaminant partitioning and diffusion to contaminant permeation.

Inhibition of human osteosarcoma cell migration and invasion by a gene silencer, pyrrole-imidazole polyamide, targeted at the human MMP9 NF-κB binding site.

PubMed

Kojima, Toshio; Wang, Xiaofei; Fujiwara, Kyoko; Osaka, Shunzo; Yoshida, Yukihiro; Osaka, Eiji; Taniguchi, Masashi; Ueno, Takahiro; Fukuda, Noboru; Soma, Masayoshi; Tokuhashi, Yasuaki; Nagase, Hiroki

2014-01-01

Osteosarcoma is one of the most prevalent bone tumors, occurring mostly in adolescence. However, no noticeable progress has been achieved in developing new therapeutic agents for this disease. Matrix metalloproteinase 9 (MMP9), a type IV collagenase, is a known anticancer target and is overexpressed in osteosarcomas. MMPs can degrade components of the extracellular matrix and are known to be involved in tumor invasion and metastasis. In the present study, we designed and synthesized a pyrrole-imidazole polyamide (HN.49), a gene-silencing agent that specifically targets the nuclear factor-kappa B (NF-κB) binding site of the human MMP9 promoter. We then examined the effect of HN.49 on the enzyme activity of MMP9 and the migration activity of osteosarcoma cells in vitro. It was clearly shown that HN.49 polyamide reduced the expression level of MMP9 mRNA and the enzymatic activity of MMP-9 in SaOS-2 cells. Moreover, HN.49 polyamide inhibited migration and invasion by SaOS-2 cells in in vitro wound-closure and matrigel-invasion assays. These results indicate that HN.49 may be a potential therapeutic agent for inhibiting the invasion and metastasis of osteosarcoma.

Energetic basis for selective recognition of T*G mismatched base pairs in DNA by imidazole-rich polyamides.

PubMed

Lacy, Eilyn R; Nguyen, Binh; Le, Minh; Cox, Kari K; OHare, Caroline; Hartley, John A; Lee, Moses; Wilson, W David

2004-01-01

To complement available structure and binding results and to develop a detailed understanding of the basis for selective molecular recognition of T.G mismatches in DNA by imidazole containing polyamides, a full thermodynamic profile for formation of the T.G-polyamide complex has been determined. The amide-linked heterocycles f-ImImIm and f-PyImIm (where f is formamido group, Im is imidazole and Py is pyrrole) were studied by using biosensor-surface plasmon resonance (SPR) and isothermal titration calorimetry (ITC) with a T.G mismatch containing DNA hairpin duplex and a similar DNA with only Watson-Crick base pairs. Large negative binding enthalpies for all of the polyamide-DNA complexes indicate that the interactions are enthalpically driven. SPR results show slower complex formation and stronger binding of f-ImImIm to the T.G than to the match site. The thermodynamic analysis indicates that the enhanced binding to the T.G site is the result of better entropic contributions. Negative heat capacity changes for the complex are correlated with calculated solvent accessible surface area changes and indicate hydrophobic contributions to complex formation. DNase I footprinting analysis in a long DNA sequence provided supporting evidence that f-ImImIm binds selectively to T.G mismatch sites.

Processing for maximizing the level of crystallinity in linear aromatic polyimides

NASA Technical Reports Server (NTRS)

St.clair, Terry L. (Inventor)

1991-01-01

The process of the present invention includes first treating a polyamide acid (such as LARC-TPI polyamide acid) in an amide-containing solvent (such as N-methyl pyrrolidone) with an aprotic organic base (such as triethylamine), followed by dehydrating with an organic dehydrating agent (such as acetic anhydride). The level of crystallinity in the linear aromatic polyimide so produced is maximized without any degradation in the molecular weight thereof.

Developments in Signature Process Control

NASA Astrophysics Data System (ADS)

Keller, L. B.; Dominski, Marty

1993-01-01

Developments in the adaptive process control technique known as Signature Process Control for Advanced Composites (SPCC) are described. This computer control method for autoclave processing of composites was used to develop an optimum cure cycle for AFR 700B polyamide and for an experimental poly-isoimide. An improved process cycle was developed for Avimid N polyamide. The potential for extending the SPCC technique to pre-preg quality control, press modeling, pultrusion and RTM is briefly discussed.

Microchemical Systems and Their Applications Workshop Held on 16-18 June 1999 in Reston, Virginia

DTIC Science & Technology

2000-03-29

USABLE BY- PRODUCT HYDROGEN, BUT COST OF THE PT COATED CERAMIC TUBES IS HIGH, HEAT TRANSFER EFFICIENCY IS LIMITED, AND THE RISK ASSOCIATED WITH...Monolith reactor Monolith Catalyst A Gas mixture i quartz tube T 1 Radiation Shields GC / analysis 3M Monolith Catalysts *-v.V...polyamide. MicroChannel patterned laminates are fabricated from polyamide while microfin -patterned laminates are fabricated from copper. In addition to

Semipermeable polymers and method for producing same

DOEpatents

Buschmann, Wayne E [Boulder, CO

2012-04-03

A polyamide membrane comprising reaction product of an anhydrous solution comprising an anhydrous solvent, at least one polyfunctional secondary amine and a pre-polymer deposition catalyst; and an anhydrous, organic solvent solution comprising a polyfunctional aromatic amine-reactive reactant comprising one ring. A composite semipermeable membrane comprising the polyamide membrane on a porous support. A method of making a composite semipermeable membrane by coating a porous support with an anhydrous solution comprising an anhydrous solvent, a polyfunctional secondary amine and a pre-polymer deposition catalyst, to form an activated pre-polymer layer on the porous support and contacting the activated pre-polymer layer with an anhydrous, organic solvent solution comprising a polyfunctional amine-reactive reactant to interfacially condense the amine-reactive reactant with the polyfunctional secondary amine, thereby forming a cross-linked, interfacial polyamide layer on the porous support. A method of impregnating a composite semipermeable membrane with nanoparticles selected from heavy metals and/or oxides of heavy metals.

A novel aryl acylamidase from Nocardia farcinica hydrolyses polyamide.

PubMed

Heumann, Sonja; Eberl, Anita; Fischer-Colbrie, Gudrun; Pobeheim, Herbert; Kaufmann, Franz; Ribitsch, Doris; Cavaco-Paulo, Artur; Guebitz, Georg M

2009-03-01

An alkali stable polyamidase was isolated from a new strain of Nocardia farcinica. The enzyme consists of four subunits with a total molecular weight of 190 kDa. The polyamidase cleaved amide and ester bonds of water insoluble model substrates like adipic acid bishexylamide and bis(benzoyloxyethyl)terephthalate and hydrolyzed different soluble amides to the corresponding acid. Treatment of polyamide 6 with this amidase led to an increased hydrophilicity based on rising height and tensiometry measurements and evidence of surface hydrolysis of polyamide 6 is shown. In addition to amidase activity, the enzyme showed activity on p-nitrophenylbutyrate. On hexanoamide the amidase exhibited a K(m) value of 5.5 mM compared to 0.07 mM for p-nitroacetanilide. The polyamidase belongs to the amidase signature family and is closely related to aryl acylamidases from different strains/species of Nocardia and to the 6-aminohexanoate-cyclic dimer hydrolase (EI) from Arthrobacter sp. KI72.

New Polymer Materials for the Laser Sintering Process: Polypropylene and Others

NASA Astrophysics Data System (ADS)

Wegner, Andreas

Laser sintering of polymers gets more and more importance for small series production. However, there is only a little number of materials available for the process. In most cases parts are build up using polyamide 12 or polyamide 11. Reasons for that are high prices, a restricted availability, poor mechanical part properties or an insufficient understanding of the processing of other materials. These problems result from the complex processing conditions in laser sintering with high requirements on the material's characteristics. Within this area, at the chair for manufacturing technology fundamental knowledge was established. Aim of the presented study was to qualify different polymers for the laser sintering process. Polyethylene, polypropylene, polyamide 6, polyoxymethylene as well as polybutylene terephthalate were analyzed. Within the study problems of qualifying new materials are discussed using some examples. Furthermore, the processing conditions as well as mechanical properties of a new polypropylene compound are shown considering also different laser sintering machines.

Optical and Thermal Behaviors of Polyamide-Layered Silicate Nanocomposites Based on 4,4'-Azodibenzoic Acid by Solution Intercalation Technique

NASA Astrophysics Data System (ADS)

Faghihi, Khalil; Shabanian, Meisam

2011-04-01

Two new samples of polyamide-montmorillonite reinforced nanocomposites based on 4,4'-azodibenzoic acid were prepared by a convenient solution intercalation technique. Polyamide (PA) 4 as a source of polymer matrix was synthesized by the direct polycondensation reaction of 4,4'-azodibenzoic acid 2 with 4,4'-diamino diphenyl sulfone 3 in the presence of triphenyl phosphate (TPP), CaCl2, pyridine and N-methyl-2-pyrrolidone (NMP). Morphology and structure of the resulting PA-nanocomposite films 4a and 4b with 10 and 20% silicate particles were characterized by FTIR spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effect of clay dispersion and the interaction between clay and polymeric chains on the properties of nanocomposite films were investigated by using Uv-vis spectroscopy, thermogravimetric analysis (TGA) and water uptake measurements.

Antimocrobial Polymer

DOEpatents

McDonald, William F.; Huang, Zhi-Heng; Wright, Stacy C.

2005-09-06

A polymeric composition having antimicrobial properties and a process for rendering the surface of a substrate antimicrobial are disclosed. The composition comprises a crosslinked chemical combination of (i) a polymer having amino group-containing side chains along a backbone forming the polymer, (ii) an antimicrobial agent selected from quaternary ammonium compounds, gentian violet compounds, substituted or unsubstituted phenols, biguanide compounds, iodine compounds, and mixtures thereof, and (iii) a crosslinking agent containing functional groups capable of reacting with the amino groups. In one embodiment, the polymer is a polyamide formed from a maleic anhydride or maleic acid ester monomer and alkylamines thereby producing a polyamide having amino substituted alkyl chains on one side of the polyamide backbone; the crosslinking agent is a phosphine having the general formula (A)3P wherein A is hydroxyalkyl; and the antimicrobial agent is chlorhexidine, dimethylchlorophenol, cetyl pyridinium chloride, gentian violet, triclosan, thymol, iodine, and mixtures thereof.

Antimicrobial Polymer

DOEpatents

McDonald, William F.; Wright, Stacy C.; Taylor, Andrew C.

2004-09-28

A polymeric composition having antimicrobial properties and a process for rendering the surface of a substrate antimicrobial are disclosed. The polymeric composition comprises a crosslinked chemical combination of (i) a polymer having amino group-containing side chains along a backbone forming the polymer, (ii) an antimicrobial agent selected from metals, metal alloys, metal salts, metal complexes and mixtures thereof, and (iii) a crosslinking agent containing functional groups capable of reacting with the amino groups. In one example embodiment, the polymer is a polyamide formed from a maleic anhydride or maleic acid ester monomer and alkylamines thereby producing a polyamide having amino substituted alkyl chains on one side of the polyamide backbone; the crosslinking agent is a phosphine having the general formula (A).sub.3 P wherein A is hydroxyalkyl; and the metallic antimicrobial agent is selected from chelated silver ions, silver metal, chelated copper ions, copper metal, chelated zinc ions, zinc metal and mixtures thereof.

Isolation and identification of arctiin and arctigenin in leaves of burdock (Arctium lappa L.) by polyamide column chromatography in combination with HPLC-ESI/MS.

PubMed

Liu, Shiming; Chen, Kaoshan; Schliemann, Willibald; Strack, Dieter

2005-01-01

A simple method involving polyamide column chromatography in combination with HPLC-PAD and HPLC-ESI/MS for isolating and identifying two kinds of lignans, arctiin and arctigenin, in the leaves of burdock (Arctium lappa L.) has been established. After extraction of burdock leaves with 80% methanol, the aqueous phase of crude extracts was partitioned between water and chloroform and the aqueous phase was fractionated on a polyamide glass column. The fraction, eluting with 100% methanol, was concentrated and gave a white precipitate at 4 degrees C from which two main compounds were purified by semi-preparative HPLC. In comparison with the UV and ESI-MS spectra and the HPLC retention time of authentic standards, the compounds were determined to be arctiin and arctigenin. The extraction/separation technique was validated using an internal standard method.

Polyamide desalination membrane characterization and surface modification to enhance fouling resistance.

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

Sharma, Mukul M.; Freeman, Benny D.; Van Wagner, Elizabeth M.

2010-08-01

The market for polyamide desalination membranes is expected to continue to grow during the coming decades. Purification of alternative water sources will also be necessary to meet growing water demands. Purification of produced water, a byproduct of oil and gas production, is of interest due to its dual potential to provide water for beneficial use as well as to reduce wastewater disposal costs. However, current polyamide membranes are prone to fouling, which decreases water flux and shortens membrane lifetime. This research explored surface modification using poly(ethylene glycol) diglycidyl ether (PEGDE) to improve the fouling resistance of commercial polyamide membranes. Characterizationmore » of commercial polyamide membrane performance was a necessary first step before undertaking surface modification studies. Membrane performance was found to be sensitive to crossflow testing conditions. Concentration polarization and feed pH strongly influenced NaCl rejection, and the use of continuous feed filtration led to higher water flux and lower NaCl rejection than was observed for similar tests performed using unfiltered feed. Two commercial polyamide membranes, including one reverse osmosis and one nanofiltration membrane, were modified by grafting PEGDE to their surfaces. Two different PEG molecular weights (200 and 1000) and treatment concentrations (1% (w/w) and 15% (w/w)) were studied. Water flux decreased and NaCl rejection increased with PEGDE graft density ({micro}g/cm{sup 2}), although the largest changes were observed for low PEGDE graft densities. Surface properties including hydrophilicity, roughness and charge were minimally affected by surface modification. The fouling resistance of modified and unmodified membranes was compared in crossflow filtration studies using model foulant solutions consisting of either a charged surfactant or an oil in water emulsion containing n-decane and a charged surfactant. Several PEGDE-modified membranes demonstrated improved fouling resistance compared to unmodified membranes of similar initial water flux, possibly due to steric hindrance imparted by the PEG chains. Fouling resistance was higher for membranes modified with higher molecular weight PEG. Fouling was more extensive for feeds containing the cationic surfactant, potentially due to electrostatic attraction with the negatively charged membranes. However, fouling was also observed in the presence of the anionic surfactant, indicating hydrodynamic forces are also responsible for fouling.« less

Polyester-Based (Bio)degradable Polymers as Environmentally Friendly Materials for Sustainable Development

PubMed Central

Rydz, Joanna; Sikorska, Wanda; Kyulavska, Mariya; Christova, Darinka

2014-01-01

This review focuses on the polyesters such as polylactide and polyhydroxyalkonoates, as well as polyamides produced from renewable resources, which are currently among the most promising (bio)degradable polymers. Synthetic pathways, favourable properties and utilisation (most important applications) of these attractive polymer families are outlined. Environmental impact and in particular (bio)degradation of aliphatic polyesters, polyamides and related copolymer structures are described in view of the potential applications in various fields. PMID:25551604

The influence of cosmic radiation on the properties of different polymers

NASA Astrophysics Data System (ADS)

Major, Andrea Adamne; Boja, David

2017-10-01

During our research we investigated the influence of cosmic radiation on the properties of different polymers. Polypropylene, polyamide 6.6 and polycarbonate were used as raw materials. Test pieces were injection molded. The test pieces were "flying" at different heights (on Earth, at 5500 m, at 12000 m). Thermal properties were investigated: DSC and TGA. We found that cosmic relay influences change in the thermal properties of polypropylene, polyamide 6.6 and polycarbonate.

The effect of cycling deflection on the injection-molded thermoplastic denture base resins.

PubMed

Hamanaka, Ippei; Iwamoto, Misa; Lassila, Lippo Vj; Vallittu, Pekka K; Shimizu, Hiroshi; Takahashi, Yutaka

2016-01-01

The aim of this study was to evaluate the effect of cycling deflection on the flexural behavior of injection-molded thermoplastic resins. Six injection-molded thermoplastic resins (two polyamides, two polyesters, one polycarbonate, one polymethyl methacrylate) and, as a control, a conventional heat-polymerized denture based polymer of polymethyl methacrylate (PMMA) were used in this study. The cyclic constant magnitude (1.0 mm) of 5000 cycles was applied using a universal testing machine to demonstrate plasticization of the polymer. Loading was carried out in water at 23ºC with eight specimens per group (n = 8). Cycling load (N) and deformation (mm) were measured. Force required to deflect the specimens during the first loading cycle and final loading cycle was statistically significantly different (p < 0.05) with one polyamide based polymer (Valplast) and PMMA based polymers (Acrytone and Acron). The other polyamide based polymer (LucitoneFRS), polyester based polymers (EstheShot and EstheShotBright) and polycarbonate based polymer (ReigningN) did not show significant differences (p > 0.05). None of the materials fractured during the loading test. One polyamide based polymer (Valplast) displayed the highest deformation and PMMA based polymers (Acrytone and Acron) exhibited the second highest deformation among the denture base materials. It can be concluded that there were considerable differences in the flexural behavior of denture base polymers. This may contribute to the fatigue resistance of the materials.

Effect of addition of plants-derived polyamide 11 elastomer on the mechanical and tribological properties of hemp fiber reinforced polyamide 1010 composites

NASA Astrophysics Data System (ADS)

Mukaida, Jun; Nishitani, Yosuke; Kitano, Takeshi

2015-05-01

For the purpose of developing the new engineering materials such as structural materials and tribomaterials based on all plants-derived materials, the effect of the addition of plant-derived polyamide 11 Elastomer (PA11E) on the mechanical and tribological properties of hemp fiber(HF) reinforced polyamide 1010 (HF/PA1010) composites was investigated. PA1010 and PA11E (except the polyether groups used as soft segment) were made from plant-derived castor oil. Hemp fiber was surface-treated by two types of treatment: alkali treatment by NaOH solution and surface treatment by ureido silane coupling agent. HF/PA1010/PA11E ternary composites were extruded by a twin screw extruder and injection-molded. Their mechanical properties such as tensile, bending, Izod impact and tribological properties by ring-on-plate type sliding wear testing were evaluated. The effect of the addition of PA11E on the mechanical and tribological properties of HF/PA1010 composite differed for each property. Izod impact strength and specific wear rate improved with the addition of PA11E although tensile strength, modulus, and friction coefficient decreased with PA11E. It follows from these results that it may be possible to develop the new engineering materials with sufficient balance between mechanical and tribological properties.

Polyamide thermosets

DOEpatents

Benicewicz, B.C.; Hoyt, A.E.

1993-03-30

The present invention provides (1) curable polyamide monomers represented by the formula: R[sup 1]-A[sup 1]-B[sup 1]-A[sup 2]-B[sup 2]-A[sup 3]-R[sup 2] where R[sup 1] and R[sup 2] are radicals selected from the group consisting of maleimide, substituted maleimide, nadimide, substituted nadimide, ethynyl, and (C(R[sup 3])[sub 2])[sub 2] where R[sup 3] is hydrogen with the proviso that the two carbon atoms of (C(R[sup 3])[sub 2])[sub 2] are bound on the aromatic ring of A[sup 1] or A[sup 3] to adjacent carbon atoms, A[sup 1] and A[sup 3] are 1,4-phenylene and the same where said group contains one or more substituents selected from the group consisting of halo, e.g., fluoro, chloro, bromo, or iodo, nitro, lower alkyl, e.g., methyl, ethyl, and propyl, lower alkoxy, e.g., methoxy, ethoxy, or propoxy, and fluoroalkyl or fluoroalkoxy, e.g., trifluoromethyl, pentafluoroethyl and the like, A[sup 2] is selected from the group consisting of 1,4-phenylene, 4,4[prime]-biphenyl, 2,6-naphthylene and the same where said groups contain one or more substituents selected from the group consisting of halo, e.g., fluoro, chloro, bromo, or iodo, nitro, lower alkyl, e.g., methyl, ethyl, and propyl, lower alkoxy, e.g., methoxy, ethoxy, or propoxy, and fluoroalkyl or fluoroalkoxy, e.g., trifluoromethyl, pentafluoroethyl and the like, and B[sup 1] and B[sup 2] are selected from the group consisting of -C(O)-N(H)- and -N(H)-C(O)-, (2) thermoset polyamide compositions comprised of cured segments derived from monomers represented by the formula: R[sup 1]-A[sup 1]-B[sup 1]-A[sup 2]-B[sup 2]-A[sup 3]-R[sup 2] as described above, and curable blends of at least two of the polyamide monomers and (3) processes of preparing the curable polyamide monomers.

Polyamide thermosets

DOEpatents

Benicewicz, Brian C.; Hoyt, Andrea E.

1993-01-01

The present invention provides (1) curable polyamide monomers represented by the formula: R.sup.1 -A.sup.1 -B.sup.1 -A.sup.2 -B.sup.2 -A.sup.3 -R.sup.2 where R.sup.1 and R.sup.2 are radicals selected from the group consisting of maleimide, substituted maleimide, nadimide, substituted nadimide, ethynyl, and (C(R.sup.3).sub.2).sub.2 where R.sup.3 is hydrogen with the proviso that the two carbon atoms of (C(R.sup.3).sub.2).sub.2 are bound on the aromatic ring of A.sup.1 or A.sup.3 to adjacent carbon atoms, A.sup.1 and A.sup.3 are 1,4-phenylene and the same where said group contains one or more substituents selected from the group consisting of halo, e.g., fluoro, chloro, bromo, or iodo, nitro, lower alkyl, e.g., methyl, ethyl, and propyl, lower alkoxy, e.g., methoxy, ethoxy, or propoxy, and fluoroalkyl or fluoroalkoxy, e.g., trifluoromethyl, pentafluoroethyl and the like, A.sup.2 is selected from the group consisting of 1,4-phenylene, 4,4'-biphenyl, 2,6-naphthylene and the same where said groups contain one or more substitutents selected from the group consisting of halo, e.g., fluoro, chloro, bromo, or iodo, nitro, lower alkyl, e.g., methyl, ethyl, and propyl, lower alkoxy, e.g., methoxy, ethoxy, or propoxy, and fluoroalkyl or fluoroalkoxy, e.g., trifluoromethyl, pentafluoroethyl and the like, and B.sup.1 and B.sup.2 are selected from the group consisting of --C(O)--N(H)-- and --N(H)--C(O)--, (2) thermoset polyamide compositions comprised of cured segments derived from monomers represented by the formula: R.sup.1 -A.sup.1 -B.sup.1 -A.sup.2 -B.sup.2 -A.sup.3 -R.sup.2 as described above, and curable blends of at least two of the polyamide monomers and (4) processes of preparing the curable polyamide monomers.

Polyamide thermosets

DOEpatents

Benicewicz, Brian C.; Hoyt, Andrea E.

1994-01-01

The present invention provides (1) curable polyamide monomers represented by the formula: R.sup.1 --A.sup.1 --B.sup.1 --A.sup.2 --B.sup.2 --A.sup.3 --R.sup.2 where R.sup.1 and R.sup.2 are radicals selected from the group consisting of maleimide, substituted maleimide, nadimide, substituted nadimide, ethynyl, and (C(R.sup.3).sub.2).sub.2 where R.sub.3 is hydrogen with the proviso that the two carbon atoms of (C(R.sup.3).sub.2).sub.2 are bound on the aromatic ring of A.sup.1 or A.sup.3 to adjacent carbon atoms, A.sup.1 and A.sup.3 are 1,4-phenylene and the same where said group contains one or more substituents selected from the group consisting of halo, e.g., fluoro, chloro, bromo, or iodo, nitro, lower alkyl, e.g., methyl, ethyl, and propyl, lower alkoxy, e.g., methoxy, ethoxy, or propoxy, and fluoroalkyl or fluoroalkoxy, e.g., trifluoromethyl, pentafluoroethyl and the like, A.sup.2 is selected from the group consisting of 1,4-phenylene, 4,4'-biphenyl, 2,6-naphthylene and the same where said groups contain one or more substituents selected from the group consisting of halo, e.g., fluoro, chloro, bromo, or iodo, nitro, lower alkyl, e.g., methyl, ethyl, and propyl, lower alkoxy, e.g., methoxy, ethoxy, or propoxy, and fluoroalkyl or fluoroalkoxy, e.g., trifluoromethyl, pentafluoroethyl and the like, and B.sup.1 and B.sup.2 are selected from the group consisting of --C(O)--N(H)-- and --N(H)--C(O)--, (2) thermoset polyamide compositions comprised of cured segments derived from monomers represented by the formula: R.sup.1 --A.sup.1 --B.sup.1 --A.sup.2 --B.sup.2 --A.sup.3 --R.sup.2 as described above, and curable blends of at least two of the polyamide monomers and (4) processes of preparing the curable polyamide monomers.

Experimental comparison of manufacturing techniques of toughened and nanoreinforced polyamides

NASA Astrophysics Data System (ADS)

Siengchin, S.; Bergmann, C.; Dangtungee, R.

2011-11-01

Composites consisting of polyamide-6 (PA-6), nitrile rubber (NBR), and sodium fluorohectorite (FH) or alumina silicate (Sungloss; SG) were produced by different techniques with latex precompounding. Their tensile and thermomechanical properties were determined by using tensile tests and a dynamic-mechanical analysis, performed at various temperatures. The PA-6/NBR composite systems produced by the direct melt compounding outperformed those obtained by using the masterbatch technique with respect to the strength and ductility, but the latter ones had a higher storage modulus.

Removal of bisphenol A (BPA) from water by various nanofiltration (NF) and reverse osmosis (RO) membranes.

PubMed

Yüksel, Suna; Kabay, Nalan; Yüksel, Mithat

2013-12-15

The removal of an endocrine disrupting compound, bisphenol A (BPA), from model solutions by selected nanofiltration (NF) and reverse osmosis (RO) membranes was studied. The commercially available membranes NF 90, NF 270, XLE BWRO, BW 30 (Dow FilmTech), CE BWRO and AD SWRO (GE Osmonics) were used to compare their performances for BPA removal. The water permeability coefficients, rejection of BPA and permeate flux values were calculated for all membranes used. No significant changes in their BPA removal were observed for all tight polyamide based NF and RO membranes tested except for loose NF 270 membrane. The polyamide based membranes exhibited much better performance than cellulose acetate membrane for BPA removal. Almost a complete rejection (≥ 98%) for BPA was obtained with three polyamide based RO membranes (BW 30, XLE BWRO and AD SWRO). But cellulose acetate based CE BWRO membrane offered a low and variable (10-40%) rejection for BPA. Copyright © 2013 Elsevier B.V. All rights reserved.

Synthesis and investigation of antimicrobial activity and spectrophotometric and dyeing properties of some novel azo disperse dyes based on naphthalimides.

PubMed

Shaki, Hanieh; Gharanjig, Kamaladin; Khosravi, Alireza

2015-01-01

A series of novel disperse dyes containing azo group were synthesized through a diazotization and coupling process. The 4-amino-N-2-aminomethylpyridine-1,8-naphthalimide was diazotized by nitrosylsulphuric acid and coupled with various aromatic amines such as N,N-diethylaniline, N,N-dihydroxyethylaniline, 8-hydroxyquinoline, and 2-methylindole. Chemical structures of the synthesized dyes were characterized by Fourier transform infrared (FTIR), differential scanning calorimetry (DSC), proton nuclear magnetic resonance ((1) H NMR), carbon nuclear magnetic resonance ((13) C NMR), elemental analysis, and ultraviolet-visible (UV-visible) spectroscopy. The spectrophotometric data of all dyes were evaluated in various solvents with different polarity. Eventually, the dyes were applied on polyamide fabrics in order to investigate their dyeing properties. The fastness properties of the dyed fabrics such as wash, light, and rubbing fastness degrees were measured by standard methods. Moreover, the color gamut of the synthesized dyes was measured on polyamide fabrics. Results indicated that some of the synthesized dyes were able to dye polyamide fabrics with deep shades. They had very good wash and rubbing fastness degrees and moderate-to-good light fastness on polyamide fabrics. The antibacterial and antifungal activities of the synthesized dyes were evaluated in soluble state and on the dyed fabrics. The results indicated that dye 2 containing N,N-dihydroxyethylaniline as coupler had the highest activity against all the bacteria and fungi used. © 2015 American Institute of Chemical Engineers.

Novel Organic Phototransistor-Based Nonvolatile Memory Integrated with UV-Sensing/Green-Emissive Aggregation Enhanced Emission (AEE)-Active Aromatic Polyamide Electret Layer.

PubMed

Cheng, Shun-Wen; Han, Ting; Huang, Teng-Yung; Chang Chien, Yu-Hsin; Liu, Cheng-Liang; Tang, Ben Zhong; Liou, Guey-Sheng

2018-05-30

A novel aggregation enhanced emission (AEE)-active polyamide TPA-CN-TPE with a high photoluminesence characteristic was successfully synthesized by the direct polymerization of 4-cyanotriphenyl diamine (TPA-CN) and tetraphenylethene (TPE)-containing dicarboxylic acid. The obtained luminescent polyamide plays a significant role as the polymer electret layer in organic field-effect transistors (OFETs)-type memory. The strong green emission of TPA-CN-TPE under ultraviolet (UV) irradiation can be directly absorbed by the pentacene channel, displaying a light-induced programming and voltage-driven erasing organic phototransistor-based nonvolatile memory. Memory window can be effectively manipulated between the programming and erasing states by applying UV light illumination and electrical field, respectively. The photoinduced memory behavior can be maintained for over 10 4 s between these two states with an on/off ratio of 10 4 , and the memory switching can be steadily operated for many cycles. With high photoresponsivity ( R) and photosensitivity ( S), this organic phototransistor integrated with AEE-active polyamide electret layer could serve as an excellent candidate for UV photodetectors in optical applications. For comparison, an AEE-inactive aromatic polyimide TPA-PIS electret with much weaker solid-state emission was also applied in the same OFETs device architecture, but this device did not show any UV-sensitive and UV-induced memory characteristics, which further confirmed the significance of the light-emitting capability of the electret layer.

DNA mobility modifier

DOEpatents

Barron, Annelise

2002-01-01

Polyamides comprising at least one hydrophilic C.sub.1 -C.sub.10 hydrocarbyl substituent on an amide nitrogen atom, and methods for producing and using the same is provided. In particular, polyamides of the formula: ##STR1## and methods for using the same for altering the ratio of charge/translational frictional drag of binding polymers to allow electrophoretic separation of polynucleotides or analogs thereof in a non-sieving liquid medium is provided, where a, q, L.sup.1, P.sup.1, Q.sup.1, R, R.sup.1, R.sup.10 and R.sup.11 are those described herein.

DNA mobility modifier

DOEpatents

Barron, Annelise E.

2004-04-20

Polyamides comprising at least one hydrophilic C.sub.1 -C.sub.10 hydrocarbyl substituent on an amide nitrogen atom, and methods for producing and using the same is provided. In particular, polyamides of the formula: ##STR1## and methods for using the same for altering the ratio of charge/translational frictional drag of binding polymers to allow electrophoretic separation of polynucleotides or analogs thereof in a non-sieving liquid medium is provided, where a, q, L.sup.1, P.sup.1, Q.sup.1, R, R.sup.1, R.sup.10 and R.sup.11 are those described herein.

Synthesis and characterization of new polyamides derived from alanine and valine derivatives

PubMed Central

2012-01-01

Background Many efforts have been recently devoted to design, investigate and synthesize biocompatible, biodegradable polymers for applications in medicine for either the fabrication of biodegradable devices or as drug delivery systems. Many of them consist of condensation of polymers having incorporated peptide linkages susceptible to enzymatic cleavage. Polyamides (PAs) containing α-amino acid residues such as L-leucine, L-alanine and L-phenylalanine have been reported as biodegradable materials. Furthermore, polyamides (PAs) derived from C10 and C14 dicarboxylic acids and amide-diamines derived from 1,6-hexanediamine or 1,12-dodecanediamine and L-phenylalanine, L-valyl-L-phenylalanine or L-phenylalanyl-L-valine residues have been reported as biocompatible polymers. We have previously described the synthesis and thermal properties of a new type of polyamides-containing amino acids based on eight new symmetric meta-oriented protected diamines derived from coupling of amino acids namely; Fomc-glycine, Fmoc-alanine, Fomc-valine and Fomc-leucine with m-phenylene diamine or 2,6-diaminopyridine. Results revealed that incorporation of pyridine onto the polymeric backbone of all series decreases the thermal stability. Here we describe another family of polyamides based on benzene dicarboxylic acid, pyridine dicarboxylic acid, and α-amino acid linked to benzidine and 4,4′-oxydianiline to study the effect of the dicarboxylic acid as well as the amino acids on the nature and thermal stability of the polymers. Results We report here the preparation of a new type of polyamides based on benzene dicarboxylic acid, pyridine dicarboxylic acid, and α-amino acid linked to benzidine and 4,4′-oxydianiline to study the effect of the dicarboxylic acid as well as the amino acids on the nature and thermal stability of polymers. The thermal properties of the polymers were evaluated by different techniques. Results revealed that structure-thermal property correlation based on changing the dicarboxylic acid monomer or the diamine monomer demonstrated an interesting connection between a single change (changing the dicarboxylic acids in each series while the diamine is fixed) and thermal properties. The newly prepared polymers may possess biodegradability and thus may find some applications as novel biomaterials. Conclusions The thermal properties of the new type of polyamides based on benzene dicarboxylic acid, pyridine dicarboxylic acid, and α-amino acid (alanine and valine) linked to benzidine and 4,4′-oxydianiline were evaluated by thermal gravimetric (TG), differential thermal gravimetric (DTG) and differential thermal analysis (DTA) techniques. Results revealed that the structure-thermal property correlation based on changing the dicarboxylic acid monomer or the diamine monomer demonstrated an interesting connection between a single change (changing the dicarboxylic acids in each series while the diamine is fixed) and thermal properties. In addition, pyridine-containing polymers exhibited semicrystalline characteristic with melting temperature, Tm. where none of the valine-containing polymers showed a melting and crystallization peak indicating that the polymers were amorphous. This is expected since L-valine side chain can inhibit close packing and eliminate crystallization. The newly prepared polymers may possess biodegradability and thus may find some applications as novel biomaterials. PMID:23122321

Knowledge-Based Elastic Potentials for Docking Drugs or Proteins with Nucleic Acids

PubMed Central

Ge, Wei; Schneider, Bohdan; Olson, Wilma K.

2005-01-01

Elastic ellipsoidal functions defined by the observed hydration patterns around the DNA bases provide a new basis for measuring the recognition of ligands in the grooves of double-helical structures. Here a set of knowledge-based potentials suitable for quantitative description of such behavior is extracted from the observed positions of water molecules and amino acid atoms that form hydrogen bonds with the nitrogenous bases in high resolution crystal structures. Energies based on the displacement of hydrogen-bonding sites on drugs in DNA-crystal complexes relative to the preferred locations of water binding around the heterocyclic bases are low, pointing to the reliability of the potentials and the apparent displacement of water molecules by drug atoms in these structures. The validity of the energy functions has been further examined in a series of sequence substitution studies based on the structures of DNA bound to polyamides that have been designed to recognize the minor-groove edges of Watson-Crick basepairs. The higher energies of binding to incorrect sequences superimposed (without conformational adjustment or displacement of polyamide ligands) on observed high resolution structures confirm the hypothesis that the drug subunits associate with specific DNA bases. The knowledge-based functions also account satisfactorily for the measured free energies of DNA-polyamide association in solution and the observed sites of polyamide binding on nucleosomal DNA. The computations are generally consistent with mechanisms by which minor-groove binding ligands are thought to recognize DNA basepairs. The calculations suggest that the asymmetric distributions of hydrogen-bond-forming atoms on the minor-groove edge of the basepairs may underlie ligand discrimination of G·C from C·G pairs, in addition to the commonly believed role of steric hindrance. The analysis of polyamide-bound nucleosomal structures reveals other discrepancies in the expected chemical design, including unexpected contacts to DNA and modified basepair targets of some ligands. The ellipsoidal potentials thus appear promising as a mathematical tool for the study of drug- and protein-DNA interactions and for gaining new insights into DNA-binding mechanisms. PMID:15501936

Bacterial Colonization and Tissue Compatibility of Denture Base Resins.

PubMed

Olms, Constanze; Yahiaoui-Doktor, Maryam; Remmerbach, Torsten W; Stingu, Catalina Suzana

2018-06-15

Currently, there is minimal clinical data regarding biofilm composition on the surface of denture bases and the clinical tissue compatibility. Therefore, the aim of this experimental study was to compare the bacterial colonization and the tissue compatibility of a hypoallergenic polyamide with a frequently used PMMA resin tested intraorally in a randomized split-mouth design. Test specimens made of polyamide ( n = 10) and PMMA ( n = 10) were attached over a molar band appliance in oral cavity of 10 subjects. A cytological smear test was done from palatal mucosa at baseline and after four weeks. The monolayers were inspected for micronuclei. After four weeks in situ, the appliance was removed. The test specimens were immediately cultivated on non-selective and selective nutrient media. All growing colonies were identified using VITEK-MS. The anonymized results were analyzed descriptively. A total of 110 different bacterial species could be isolated, including putative pathogens. An average of 17.8 different bacterial species grew on the PMMA specimens, and 17.3 on the polyamide specimens. The highest number of different bacterial species was n = 24, found on a PMMA specimen. On the two specimens, a similar bacterial distribution was observed. Micronuclei, as a marker for genotoxic potential of dental materials, were not detected. This study indicates that the composition of bacterial biofilm developed on these resins after four weeks is not influenced by the type of resin itself. The two materials showed no cytological differences. This investigation suggests that polyamide and PMMA are suitable for clinical use as denture base material.

In Vitro Tensile Strength Study on Suturing Technique and Material.

PubMed

González-Barnadas, Albert; Camps-Font, Octavi; Espanya-Grifoll, Dunia; España-Tost, Antoni; Figueiredo, Rui; Valmaseda-Castellón, Eduard

2017-06-01

Suture technique and materials are important in preventing complications such as wound dehiscences. The purpose of this study was to determine the tensile strength of different suturing techniques, comparing several materials with different diameters. One hundred sixty sutures were performed using silk, e-PTFE, and 2 types of polyamide (monofilament and Supramid). Ten simple, 10 horizontal mattress, and 10 combinations of the two stitches were performed with 4-0 gauge of each material. Additionally, 10 simple sutures were performed with the 5-0 gauge of each material. The maximum tensile force resisted by each suture was recorded. When 5 mm of traction was applied, the polyamide monofilament resisted significantly better without untying or breaking compared with Supramid or silk, while the e-PTFE was superior to all the others. However, the force when e-PTFE 4-0 sutures untied or broke was lower than for either type of polyamide. The combined technique withstood a significantly higher tensile force before unknotting or breaking than did the simple and mattress stitches. The 5-0 gauges of silk and both types of polyamide showed lower tensile strengths than the 4-0 materials. Among the 5-0 sutures, Supramid showed a higher tensile strength than silk. The combined suture technique possessed greater tensile strength than did a simple or a horizontal mattress suture, and e-PTFE 4-0 withstood more traction without untying or breaking than did all the other materials, although at a lower tensile force. With the exception of e-PTFE, 4-0 sutures had greater tensile strength than did 5-0 sutures.

Simultaneous separation and purification of chlorogenic acid, epicatechin, hyperoside and phlorizin from thinned young Qinguan apples by successive use of polyethylene and polyamide resins.

PubMed

Sun, Lijun; Liu, Dongjie; Sun, Jiaojiao; Yang, Xingbin; Fu, Minghai; Guo, Yurong

2017-09-01

The method for separating and purifying chlorogenic acid (CA), epicatechin (EC), hyperoside (HY) and phlorizin (PH) simutaneously from young Qinguan apples by successive use of X-5 and polyamide resins has been developed in this study. The order of adsorption capacities of X-5 for the four phenolics was PH>HY>EC>CA, and the adsorption equilibriums of the four phenolics onto X-5 resin conformed to Langmuir isotherms preferentially. The adsorption kinetics of EC and CA onto X-5 conformed to the pseudo-first-order model, while that of HY and PH accorded with the pseudo-second-order model. Interestingly, the values of equilibrium adsorption capacities (Q e ) calculated in the preferential kinetics models were closer to that of theoretical maximum adsorption capacities (Q 0 ) calculated by Langmuir isotherms. Through dynamic adsorption and desorption using X-5 and polyamide resins with ethanol solution as strippant, CA, EC, HY and PH were obtained with purities of 96.21%, 95.34%, 95.36% and 97.36%, respectively. Copyright © 2017 Elsevier Ltd. All rights reserved.

Morphology and transport in biodegradable polymer compositions based on poly(3-hydroxybutyrate) and polyamide 54C

NASA Astrophysics Data System (ADS)

Zhul'Kina, A. L.; Ivantsova, E. L.; Filatova, A. G.; Kosenko, R. Yu.; Gumargalieva, K. Z.; Iordanskii, A. L.

2009-05-01

Complex investigation of the equilibrium sorption of water, diffusive transport of antiseptic, and morphology of mixed compositions based on polyoxybutirate and polyamide resin 54C has been performed to develop and analyze new biodegradable polymer compositions for controlled release of medicinal substances. Samples of mixtures were prepared by two methods: pressing under pressure and solvent evaporation from a polymer solution. The samples were compared and their morphology was analyzed by scanning electron microscopy. It is shown that the component ratio in the obtained mixtures affects their morphological, transport, and sorption characteristics.

Polyamide membranes with nanoscale Turing structures for water purification

NASA Astrophysics Data System (ADS)

Tan, Zhe; Chen, Shengfu; Peng, Xinsheng; Zhang, Lin; Gao, Congjie

2018-05-01

The emergence of Turing structures is of fundamental importance, and designing these structures and developing their applications have practical effects in chemistry and biology. We use a facile route based on interfacial polymerization to generate Turing-type polyamide membranes for water purification. Manipulation of shapes by control of reaction conditions enabled the creation of membranes with bubble or tube structures. These membranes exhibit excellent water-salt separation performance that surpasses the upper-bound line of traditional desalination membranes. Furthermore, we show the existence of high water permeability sites in the Turing structures, where water transport through the membranes is enhanced.

Morphology and transport in biodegradable polymer compositions based on poly(3-hydroxybutyrate) and polyamide 54C

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

Zhul'kina, A. L.; Ivantsova, E. L.; Filatova, A. G.

2009-05-15

Complex investigation of the equilibrium sorption of water, diffusive transport of antiseptic, and morphology of mixed compositions based on polyoxybutirate and polyamide resin 54C has been performed to develop and analyze new biodegradable polymer compositions for controlled release of medicinal substances. Samples of mixtures were prepared by two methods: pressing under pressure and solvent evaporation from a polymer solution. The samples were compared and their morphology was analyzed by scanning electron microscopy. It is shown that the component ratio in the obtained mixtures affects their morphological, transport, and sorption characteristics.

Effect of food characteristics, storage conditions, and electron beam irradiation on active agent release from polyamide-coated LDPE films.

PubMed

Han, J; Castell-Perez, M E; Moreira, R G

2008-03-01

We investigated the effect of electron beam irradiation, storage conditions, and model food pH on the release characteristics of trans-cinnamaldehyde incorporated into polyamide-coated low-density polyethylene (LDPE) films. Active agent release rate on irradiated films (up to 20.0 kGy) decreased by 69% compared with the nonirradiated controls, from 0.252 to 0.086 microg/mL/h. Storage temperature (4, 21, and 35 degrees C) and pH (4, 7, and 10) of the food simulant solutions (10% aqueous ethanol) affected the release rate of trans-cinnamaldehyde. As expected, antimicrobial release rate decreased to 0.013 microg/mL/h at the refrigerated temperature (4 degrees C) compared to the higher temperatures (0.029 and 0.035 microg/mL/h at 21 and 35 degrees C). The fastest release rate occurred when exposed to the acidic food simulant solution (pH 4). In aqueous solution, trans-cinnamaldehyde was highly unstable to ionizing radiation, with loss in concentration from 24.50 to 1.36 microg/mL after exposure to 2.0 kGy. Fourier transform infrared (FTIR) analysis revealed that exposure to ionizing radiation up to 10.0 kGy did not affect the structural conformation of LDPE/polyamide films and the trans-cinnamaldehyde in the films, though it induced changes in the functional group of trans-cinnamaldehyde when dose increased up to 20.0 kGy. Studies with a radiation-stable compound (naphthalene) showed that ionizing radiation induced the crosslinking in polymer networks of LDPE/polyamide film and caused slow and gradual release of the compound. This study demonstrated that irradiation serves as a controlling factor for release of active compounds, with potential applications in the development of antimicrobial packaging systems.

Geometric and mechanical evaluation of 3D-printing materials for skull base anatomical education and endoscopic surgery simulation - A first step to create reliable customized simulators.

PubMed

Favier, Valentin; Zemiti, Nabil; Caravaca Mora, Oscar; Subsol, Gérard; Captier, Guillaume; Lebrun, Renaud; Crampette, Louis; Mondain, Michel; Gilles, Benjamin

2017-01-01

Endoscopic skull base surgery allows minimal invasive therapy through the nostrils to treat infectious or tumorous diseases. Surgical and anatomical education in this field is limited by the lack of validated training models in terms of geometric and mechanical accuracy. We choose to evaluate several consumer-grade materials to create a patient-specific 3D-printed skull base model for anatomical learning and surgical training. Four 3D-printed consumer-grade materials were compared to human cadaver bone: calcium sulfate hemihydrate (named Multicolor), polyamide, resin and polycarbonate. We compared the geometric accuracy, forces required to break thin walls of materials and forces required during drilling. All materials had an acceptable global geometric accuracy (from 0.083mm to 0.203mm of global error). Local accuracy was better in polycarbonate (0.09mm) and polyamide (0.15mm) than in Multicolor (0.90mm) and resin (0.86mm). Resin and polyamide thin walls were not broken at 200N. Forces needed to break Multicolor thin walls were 1.6-3.5 times higher than in bone. For polycarbonate, forces applied were 1.6-2.5 times higher. Polycarbonate had a mode of fracture similar to the cadaver bone. Forces applied on materials during drilling followed a normal distribution except for the polyamide which was melted. Energy spent during drilling was respectively 1.6 and 2.6 times higher on bone than on PC and Multicolor. Polycarbonate is a good substitute of human cadaver bone for skull base surgery simulation. Thanks to short lead times and reasonable production costs, patient-specific 3D printed models can be used in clinical practice for pre-operative training, improving patient safety.

Recognition of T·G mismatched base pairs in DNA by stacked imidazole-containing polyamides: surface plasmon resonance and circular dichroism studies

PubMed Central

Lacy, Eilyn R.; Cox, Kari K.; Wilson, W. David; Lee, Moses

2002-01-01

An imidazole-containing polyamide trimer, f-ImImIm, where f is a formamido group, was recently found using NMR methods to recognize T·G mismatched base pairs. In order to characterize in detail the T·G recognition affinity and specificity of imidazole-containing polyamides, f-ImIm, f-ImImIm and f-PyImIm were synthesized. The kinetics and thermodynamics for the polyamides binding to Watson–Crick and mismatched (containing one or two T·G, A·G or G·G mismatched base pairs) hairpin oligonucleotides were determined by surface plasmon resonance and circular dichroism (CD) methods. f-ImImIm binds significantly more strongly to the T·G mismatch-containing oligonucleotides than to the sequences with other mismatched or with Watson–Crick base pairs. Compared with the Watson–Crick CCGG sequence, f-ImImIm associates more slowly with DNAs containing T·G mismatches in place of one or two C·G base pairs and, more importantly, the dissociation rate from the T·G oligonucleotides is very slow (small kd). These results clearly demonstrate the binding selectivity and enhanced affinity of side-by-side imidazole/imidazole pairings for T·G mismatches and show that the affinity and specificity increase arise from much lower kd values with the T·G mismatched duplexes. CD titration studies of f-ImImIm complexes with T·G mismatched sequences produce strong induced bands at ∼330 nm with clear isodichroic points, in support of a single minor groove complex. CD DNA bands suggest that the complexes remain in the B conformation. PMID:11937638

Polyamide microcapsules containing jojoba oil prepared by inter-facial polymerization.

PubMed

Persico, P; Carfagna, C; Danicher, L; Frere, Y

2005-08-01

Jojoba oil containing polyamide microcapsules having diameter of approximately 5 microm were prepared by inter-facial polycondensation by direct method (oil-in-water). Qualitative effects of both the formulation and the process parameters on microcapsules characteristics were investigated by SEM observations. Morphological analysis showed the dependence of the external membrane compactness on the chemical nature of the water-soluble polyamine and the oil-soluble acid polychloride: 1,6-hexamethylenediamine (HMDA) and terephthaloyl dichloride (TDC) were found to favour the production of smooth and dense surfaces. The use of ultrasonic irradiations during the dispersion step to get a further reduction of microcapsules size was also evaluated.

Surface nano-structure of polyamide 6 film by hydrothermal treatment

NASA Astrophysics Data System (ADS)

Wang, Xiaosong; Wang, Zhiliang; Liang, Songmiao; Jin, Yan; Lotz, Bernard; Yang, Shuguang

2018-06-01

Polyamide 6 (PA 6) melts and dissolves in super-heated water when T > 160 °C. Commercial PA 6 films were treated in super-heated water at 140 °C < T < 160 °C, i.e. below melting. Morphology, thermal behavior, mechanical properties, oxygen permeability and transparency of the film before and after hydrothermal treatment are investigated. After hydrothermal treatment, the melting temperature, crystallinity, elongation at break and toughness increase, whereas the strength decreases. The transparency and oxygen permeability decrease slightly. More interestingly, the hydrothermal treatment generates on the film surface a nano-structured layer 100 nm thick, which greatly improves adhesion and printing performance.

Efficient conversion of polyamides to ω-hydroxyalkanoic acids: a new method for chemical recycling of waste plastics.

PubMed

Kamimura, Akio; Ikeda, Kosuke; Suzuki, Shuzo; Kato, Kazunari; Akinari, Yugo; Sugimoto, Tsunemi; Kashiwagi, Kohichi; Kaiso, Kouji; Matsumoto, Hiroshi; Yoshimoto, Makoto

2014-09-01

An efficient transformation of polyamides to ω-hydroxy alkanoic acids was achieved. Treatment of nylon-12 with supercritical MeOH in the presence of glycolic acid gave methyl ω-hydroxydodecanoate in 85% yield and the alcohol/alkene selectivity in the product was enhanced to up to 9.5:1. The use of (18)O-enriched acetic acid for the reaction successfully introduced an (18)O atom at the alcoholic OH group in the product. This strategy may provide a new and economical solution for the chemical recycling of waste plastics. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fire resistant films for aircraft applications

NASA Technical Reports Server (NTRS)

Kourtides, D. A.

1983-01-01

Alternative sandwich panel decorative films were investigated as replacements for the polyvinyl fluoride currently used in aircraft interiors. Candidate films were studied for flammability, smoke emission, toxic gas emission, flame spread, and suitability as a printing surface for the decorative acrylic ink system. Several of the candidate films tested were flame modified polyvinyl fluoride, polyvinylidene fluoride, polyimide, polyamide, polysulfone, polyphenylsulfone, polyethersulfone, polybenzimidazole, polycarbonate, polyparabanic acid, polyphosphazene, polyetheretherketon, and polyester. The films were evaluated as pure films only, films silk-screened with an acrylic ink, and films adhered to a phenolic fiberglass substrate. Films which exhibited the highest fire resistant properties included PEEK polyetheretherketon, Aramid polyamide, and ISO-BPE polyester.

Investigations on injection molded, glass-fiber reinforced polyamide 6 integral foams using breathing mold technology

NASA Astrophysics Data System (ADS)

Roch, A.; Kehret, L.; Huber, T.; Henning, F.; Elsner, P.

2015-05-01

Investigations on PA6-GF50 integral foams have been carried out using different material systems: longfiber- and shortfiber-reinforced PA6 as well as unreinforced PA6 as a reference material. Both chemical and physical blowing agents were applied. Breathing mold technology (decompression of the mold) was selected for the foaming process. The integral foam design, which can be conceived as a sandwich structure, helps to save material in the neutral axis area and maintains a distance between load-bearing, unfoamed skin layers. For all test series an initial mold gap of 2.5 mm was chosen and the same amount of material was injected. In order to realize different density reductions, the mold opening stroke was varied. The experiments showed that, at a constant mass per unit area, integral polyamide 6 foams have a significantly higher bending stiffness than compact components, due to their higher area moment of inertia after foaming. At a constant surface weight the bending stiffness in these experiments could be increased by up to 600 %. Both shortfiber- and longfiber-reinforced polyamide 6 showed an increase in energy absorption during foaming.

Structure-properties relationships of novel poly(carbonate-co-amide) segmented copolymers with polyamide-6 as hard segments and polycarbonate as soft segments

NASA Astrophysics Data System (ADS)

Yang, Yunyun; Kong, Weibo; Yuan, Ye; Zhou, Changlin; Cai, Xufu

2018-04-01

Novel poly(carbonate-co-amide) (PCA) block copolymers are prepared with polycarbonate diol (PCD) as soft segments, polyamide-6 (PA6) as hard segments and 4,4'-diphenylmethane diisocyanate (MDI) as coupling agent through reactive processing. The reactive processing strategy is eco-friendly and resolve the incompatibility between polyamide segments and PCD segments in preparation processing. The chemical structure, crystalline properties, thermal properties, mechanical properties and water resistance were extensively studied by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Differential scanning calorimetry (DSC), Thermal gravity analysis (TGA), Dynamic mechanical analysis (DMA), tensile testing, water contact angle and water absorption, respectively. The as-prepared PCAs exhibit obvious microphase separation between the crystalline hard PA6 phase and amorphous PCD soft segments. Meanwhile, PCAs showed outstanding mechanical with the maximum tensile strength of 46.3 MPa and elongation at break of 909%. The contact angle and water absorption results indicate that PCAs demonstrate outstanding water resistance even though possess the hydrophilic surfaces. The TGA measurements prove that the thermal stability of PCA can satisfy the requirement of multiple-processing without decomposition.

Blends of polyester ionomers with polar polymers: Interactions, reactions, and compatibilization

NASA Astrophysics Data System (ADS)

Boykin, Timothy Lamar

The compatibility of amorphous and semicrystalline polyester ionomers with various polar polymers (i.e., polyesters and polyamides) has been investigated for their potential use as minor component compatibilizers. The degree of compatibility (i.e., ranging from incompatible to miscible) between the polyester ionomers and the polar polymers was determined by evaluating the effect of blend composition on the melting behavior and phase behavior of binary blends. In addition, the origin of compatibility and/or incompatibility for each of the binary blends (i.e., polyamide/ionomer and polyester/ionomer) was determined by evaluating blends prepared by both solution and melt mixed methods. Subsequent to investigation of the binary blends, the effect of polyester ionomer addition on the compatibility of polyamide/polyester blends was investigated by evaluating the mechanical properties and phase morphology of ionomer compatibilized polyamide/polyester blends. Polyester ionomers (amorphous and semicrystalline) were shown to exhibit a high degree of compatibility (even miscibility) with polyamides, such as nylon 6,6 (N66). Compatibility was attributed to specific interactions between the metal counterion of the polyester ionomer and the amide groups of N66. The degree of compatibility (or miscibility) was shown to be dependent on the counterion type of the ionomer, with the highest degree exhibited by blends containing the divalent form of the polyester ionomers. Although polyester ionomers were shown to exhibit incompatibility with both poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT), increasing the time of melt processing significantly enhanced the compatibility of the polyester ionomers with both PET and PBT. The observed enhancement in compatibility was attributed to ester-ester interchange between the polyester blend components, which was confirmed by NMR spectroscopy. The addition of polyester ionomers as a minor component compatibilizer (i.e., 2 to 5 wt%) resulted in significant enhancement in the impact strength and a dramatic improvement in the tensile properties compared to uncompatibilized blends of nylon 6,6 (N66) with poly(butylene terephthalate) (PBT). This behavior was attributed to an increase in the interfacial adhesion between the phase-separated domains due to strong interactions between the polyester ionomer and N66. The placement of the ionomer compatibilizer at the N66/PBT interface was facilitated by pre-extrusion of the polyester ionomer with PBT, prior to extrusion with N66.

Effects of electron beam irradiation on polyamide 12 with fiberglass reinforcement

NASA Astrophysics Data System (ADS)

Jeun, Joon-Pyo; Shin, Bum-Sik; Kim, Hyun-Bin; Nho, Young-Chang; Kang, Phil-Hyun

2010-06-01

In the present study, the effects of electron beam irradiation of polyamide 12 (PA12) with fiberglass reinforcement on the thermal and wear properties were investigated. Electron beam irradiation of PA 12 was carried out over a range of irradiation doses (100-600 kGy) in air. The gel formation in the presence of a curing agent was dependent on the radiation doses. The thermal properties of irradiated PA 12 were studied in the temperature region 50-250° C to observe the changes in the melting point with radiation dose. The dimensional stability was significantly increased by electron beam irradiation and the related crosslinking of the PA 12.

Pyrrole-Imidazole Polyamides: Manual Solid-Phase Synthesis.

PubMed

Pauff, Steven M; Fallows, Andrew J; Mackay, Simon P; Su, Wu; Cullis, Paul M; Burley, Glenn A

2015-12-01

Pyrrole-imidazole polyamides (PAs) are a family of DNA-binding peptides that bind in the minor groove of double-stranded DNA (dsDNA) in a sequence-selective, programmable fashion. This protocol describes a detailed manual procedure for the solid-phase synthesis of this family of compounds. The protocol entails solution-phase synthesis of the Boc-protected pyrrole (Py) and imidazole (Im) carboxylic acid building blocks. This unit also describes the importance of choosing the appropriate condensing agent to form the amide linkages between each building block. Finally, a monomeric coupling protocol and a fragment-based approach are described that delivers PAs in 13% to 30% yield in 8 days. Copyright © 2015 John Wiley & Sons, Inc.

Crystalline structures, thermal properties and crystallizing mechanism of polyamide 6 nanotubes in confined space

NASA Astrophysics Data System (ADS)

Li, Xiaoru; Peng, Zhi; Yang, Chao; Han, Ping; Song, Guojun; Cong, Longliang

2016-09-01

The polyamide 6 (PA6) nanotubes were prepared by infiltrating the anodic aluminum oxide templates with polymer solution. Crystalline regions in the nanotube walls were detected by high-resolution transmission electron microscopy (HRTEM). X-ray diffraction (XRD), Fast Fourier Transform (FFT) and differential scanning calorimetry (DSC) techniques were employed to investigate crystallization, crystal faces and thermodynamics. It was found that the crystals were transformed from α-form in bulk to γ-form in nanotubes. It was made a detailed analysis in this article. Moreover, schematic diagram for the crystallizing mechanism of PA6 nanotubes was given to explain PA6 molecules how to crystallize in the nano-pores.

Synthesis of lipase-catalysed silicone-polyesters and silicone-polyamides at elevated temperatures.

PubMed

Frampton, Mark B; Zelisko, Paul M

2013-10-18

More and more enzymes are being explored as alternatives to conventional catalysts in chemical reactions. To utilize these biocatalysts to their fullest, it is incumbent on researchers to gain a complete understanding of the reaction conditions that particular enzymes will tolerate. To this end siloxane-containing polyesters and polyamides have been produced via N435-mediated catalysis at temperatures well above the normal denaturation temperature for free CalB. Low molecular weight disiloxane-based acceptors release the enzyme from its acylated state with equal proficiency while longer chain siloxanes favours polyester synthesis. The thermal tolerance of the enzyme catalyst is increased using longer chain diesters and generally more hydrophobic substrates.

Effects of electron beam irradiation on polyamide 12 with fiberglass reinforcement

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

Jeun, Joon-Pyo; Shin, Bum-Sik; Kim, Hyun-Bin

2010-06-02

In the present study, the effects of electron beam irradiation of polyamide 12 (PA12) with fiberglass reinforcement on the thermal and wear properties were investigated. Electron beam irradiation of PA 12 was carried out over a range of irradiation doses (100-600 kGy) in air. The gel formation in the presence of a curing agent was dependent on the radiation doses. The thermal properties of irradiated PA 12 were studied in the temperature region 50-250 deg. C to observe the changes in the melting point with radiation dose. The dimensional stability was significantly increased by electron beam irradiation and the relatedmore » crosslinking of the PA 12.« less

An HRE-Binding Py-Im Polyamide Impairs Hypoxic Signaling in Tumors.

PubMed

Szablowski, Jerzy O; Raskatov, Jevgenij A; Dervan, Peter B

2016-04-01

Hypoxic gene expression contributes to the pathogenesis of many diseases, including organ fibrosis, age-related macular degeneration, and cancer. Hypoxia-inducible factor-1 (HIF1), a transcription factor central to the hypoxic gene expression, mediates multiple processes including neovascularization, cancer metastasis, and cell survival. Pyrrole-imidazole polyamide 1: has been shown to inhibit HIF1-mediated gene expression in cell culture but its activity in vivo was unknown. This study reports activity of polyamide 1: in subcutaneous tumors capable of mounting a hypoxic response and showing neovascularization. We show that 1: distributes into subcutaneous tumor xenografts and normal tissues, reduces the expression of proangiogenic and prometastatic factors, inhibits the formation of new tumor blood vessels, and suppresses tumor growth. Tumors treated with 1: show no increase in HIF1α and have reduced ability to adapt to the hypoxic conditions, as evidenced by increased apoptosis in HIF1α-positive regions and the increased proximity of necrotic regions to vasculature. Overall, these results show that a molecule designed to block the transcriptional activity of HIF1 has potent antitumor activity in vivo, consistent with partial inhibition of the tumor hypoxic response. Mol Cancer Ther; 15(4); 608-17. ©2015 AACR. ©2015 American Association for Cancer Research.

Surface modification of thin film composite membrane by nanoporous titanate nanoparticles for improving combined organic and inorganic antifouling properties.

PubMed

Emadzadeh, D; Ghanbari, M; Lau, W J; Rahbari-Sisakht, M; Rana, D; Matsuura, T; Kruczek, B; Ismail, A F

2017-06-01

In this study, nanoporous titanate (NT) nanoparticle synthesized by the solvothermal method was used to modify polyamide layer of thin film composite membranes with the aim of improving membrane resistances against organic and inorganic fouling. Thin film nanocomposite membranes (NMs) were synthesized by adding mNTs (modified nanoparticles) into polyamide selective layer followed by characterization using different analytical instruments. The results of XPS and XRD confirmed the presence of mNTs in the polyamide layer of NMs, while FESEM, AFM, zeta potential and contact angle measurement further supported the changes in physical and chemical properties of the membrane surface upon mNTs incorporation. Results of fouling showed that NM1 (the membrane incorporated with 0.01w/v% mNTs) always demonstrated lower degree of flux decline compared to the control membrane when membranes were tested with organic, inorganic and multicomponent synthesized water, brackish water or seawater. Besides showing greater antifouling resistance, the NM also displayed significantly higher water flux compared to the control M membrane. The findings of this work confirmed the positive impact of mNTs in improving the properties of NM with respect to fouling mitigation and flux improvement. Copyright © 2017. Published by Elsevier B.V.

Intumescent formulations based on lignin and phosphinates for the bio-based textiles

NASA Astrophysics Data System (ADS)

Mandlekar, N.; Cayla, A.; Rault, F.; Giraud, S.; Salaün, F.; Malucelli, G.; Guan, J.

2017-10-01

This study investigates new intumescent formulations based on lignin and phosphinates to improve the flame retardant properties of Polyamide 11, while preserving the bio-based characteristics of this latter. Lignin has the advantage of being a bio-based compound and can be effectively used as carbon source for the design of intumescent systems in combination with other flame retardant additives. Metal phosphinates belong to a novel class of phosphorus flame retardants. Despite their increasing use, there is lack of scientific understanding as far as their fire retardancy mechanism is considered, especially in char forming polymeric materials. In this context, Polyamide 11 was melt blended with lignin and metal phosphinates. The possibility of melt spinning the prepared blends were assessed through melt flow index (MFI) tests; thermogravimetric (TG) analyses and cone calorimetry tests were exploited for investigating the thermal stability and the combustion behaviour of the obtained products, respectively. MFI results indicate that some formulations are suitable for melt spinning processes to generate flame retardant multifilament. Furthermore, the combination of lignin and phosphinates provides charring properties to polyamide 11. Finally, cone calorimetry data confirmed that the designed intumescent formulations could remarkably reduce PHRR through formation of protective char layer, hence slowing down the combustion process.

Relationship between performance deterioration of a polyamide reverse osmosis membrane used in a seawater desalination plant and changes in its physicochemical properties.

PubMed

Suzuki, Tasuma; Tanaka, Ryohei; Tahara, Marina; Isamu, Yuya; Niinae, Masakazu; Lin, Lin; Wang, Jingbo; Luh, Jeanne; Coronell, Orlando

2016-09-01

While it is known that the performance of reverse osmosis membranes is dependent on their physicochemical properties, the existing literature studying membranes used in treatment facilities generally focuses on foulant layers or performance changes due to fouling, not on the performance and physicochemical changes that occur to the membranes themselves. In this study, the performance and physicochemical properties of a polyamide reverse osmosis membrane used for three years in a seawater desalination plant were compared to those of a corresponding unused membrane. The relationship between performance changes during long-term use and changes in physicochemical properties was evaluated. The results showed that membrane performance deterioration (i.e., reduced water flux, reduced contaminant rejection, and increased fouling propensity) occurred as a result of membrane use in the desalination facility, and that the main physicochemical changes responsible for performance deterioration were reduction in PVA coating coverage and bromine uptake by polyamide. The latter was likely promoted by oxidant residual in the membrane feed water. Our findings indicate that the optimization of membrane materials and processes towards maximizing the stability of the PVA coating and ensuring complete removal of oxidants in feed waters would minimize membrane performance deterioration in water purification facilities. Copyright © 2016 Elsevier Ltd. All rights reserved.

Controllable Electrochromic Polyamide Film and Device Produced by Facile Ultrasonic Spray-coating.

PubMed

Liu, Huan-Shen; Chang, Wei-Chieh; Chou, Chin-Yen; Pan, Bo-Cheng; Chou, Yi-Shan; Liou, Guey-Sheng; Liu, Cheng-Liang

2017-09-20

Thermally stable TPA-OMe polyamide films with high transmittance modulation in response to applied potential are formed by facile ultrasonic spray-coating. Four processing conditions (Film A, Film B, Film C and Film D) through tuning both solution concentrations and deposition temperatures can be utilized for the formation of wet and dry deposited films with two film thickness intervals. The electrochromic results show that the dry deposited rough films at higher deposition temperature generally reveal a faster electrochromic response, lower charge requirements (Q) and less conspicuous color changes (smaller optical density change (ΔOD) and lightness change (ΔL*)) during the oxidation process as compared to the wet deposited smooth films at lower deposition temperature. Moreover, thicker electrochromic films from increased solution concentration exhibit more obvious changes between coloration and bleaching transition. All these four polyamide films display colorless-to-turquoise electrochromic switching with good redox stability. The large scale patterned electrochromic film and its application for assembled device (10 × 10 cm 2 in size) are also produced and reversibly operated for color changes. These represent a major solution-processing technique produced by ultrasonic spray-coating method towards scalable and cost-effective production, allowing more freedoms to facilitate the designed electrochromic devices as required.

Exploring the influence of radiation crosslinking on high-performance hydrogenated acrylonitrile butadiene rubber and polyamide 12 based blends with special reference to heat and oil resistance

NASA Astrophysics Data System (ADS)

Mohammed Reffai, Syed Ismail Syed; Chatterjee, Tuhin; Naskar, Kinsuk

2018-07-01

This paper reports the heat and oil resistant hydrogenated acrylonitrile butadiene rubber (HNBR)/Polyamide 12 (PA12) blends prepared by electron beam irradiation. Electron beam irradiated blends are characterized by processing behaviour like thermoplastic at elevated temperature and performance properties of vulcanized rubber at ambient temperature. In the present work, a new class of blends based on Hydrogenated acrylonitrile butadiene rubber (HNBR) and polyamide (PA12) has been developed. The blends are cured with different radiation dosage at a fixed blend ratio (70:30) of (HNBR/PA12). The blend having the 75 kGy shows the highest level of mechanical properties as well as superior thermal stability. Dynamic mechanical analysis (DMA) also demonstrates the tanδ values of all the blends are lower and the storage modules are higher for HE-75 kGy blend system compared to other blend system. Heat aging, oil aging, oil swelling and cross-link density study have also been carried out in details to understand the performance behaviour of these blends at service condition (150 °C). These blends are considered to find potential application in automotive sector especially for automotive under-the-hood-applications.

Amide Link Scission in the Polyamide Active Layers of Thin-Film Composite Membranes upon Exposure to Free Chlorine: Kinetics and Mechanisms.

PubMed

Powell, Joshua; Luh, Jeanne; Coronell, Orlando

2015-10-20

The volume-averaged amide link scission in the aromatic polyamide active layer of a reverse osmosis membrane upon exposure to free chlorine was quantified at a variety of free chlorine exposure times, concentrations, and pH and rinsing conditions. The results showed that (i) hydroxyl ions are needed for scission to occur, (ii) hydroxide-induced amide link scission is a strong function of exposure to hypochlorous acid, (iii) the ratio between amide links broken and chlorine atoms taken up increased with the chlorination pH and reached a maximum of ∼25%, (iv) polyamide disintegration occurs when high free chlorine concentrations, alkaline conditions, and high exposure times are combined, (v) amide link scission promotes further chlorine uptake, and (vi) scission at the membrane surface is unrepresentative of volume-averaged scission in the active layer. Our observations are consistent with previously proposed mechanisms describing amide link scission as a result of the hydrolysis of the N-chlorinated amidic N-C bond due to nucleophilic attack by hydroxyl ions. This study increases the understanding of the physicochemical changes that could occur for membranes in treatment plants using chlorine as an upstream disinfectant and the extent and rate at which those changes would occur.

Energetic basis for selective recognition of T·G mismatched base pairs in DNA by imidazole-rich polyamides

PubMed Central

Lacy, Eilyn R.; Nguyen, Binh; Le, Minh; Cox, Kari K.; O'Hare, Caroline; Hartley, John A.; Lee, Moses; Wilson, W. David

2004-01-01

To complement available structure and binding results and to develop a detailed understanding of the basis for selective molecular recognition of T·G mismatches in DNA by imidazole containing polyamides, a full thermodynamic profile for formation of the T·G–polyamide complex has been determined. The amide-linked heterocycles f-ImImIm and f-PyImIm (where f is formamido group, Im is imidazole and Py is pyrrole) were studied by using biosensor-surface plasmon resonance (SPR) and isothermal titration calorimetry (ITC) with a T·G mismatch containing DNA hairpin duplex and a similar DNA with only Watson–Crick base pairs. Large negative binding enthalpies for all of the polyamide–DNA complexes indicate that the interactions are enthalpically driven. SPR results show slower complex formation and stronger binding of f-ImImIm to the T·G than to the match site. The thermodynamic analysis indicates that the enhanced binding to the T·G site is the result of better entropic contributions. Negative heat capacity changes for the complex are correlated with calculated solvent accessible surface area changes and indicate hydrophobic contributions to complex formation. DNase I footprinting analysis in a long DNA sequence provided supporting evidence that f-ImImIm binds selectively to T·G mismatch sites. PMID:15064359

[Radiation load on the skin using a silicone-coated polyamide wound dressing during photon and electron radiotherapy].

PubMed

Thilmann, C; Adamietz, I A; Ramm, U; Mose, S; Saran, F; Böttcher, H D

1996-05-01

Silicone-coated polyamide wound dressing is frequently used for the supportive treatment in patients with radiation induced skin lesions. The use of this kind of dressing during radiotherapy with high energy beams shifts the dose built-up effect towards the skin surface. Thus the dose delivered to the skin increases. The present work quantifies changes of the skin dose by a commercial silicon-coated polyamide wound dressing. The dependence on the beam quality and on different treatment techniques is investigated. Measurements were performed with photon (60Co, 6 MV, 42 MV) and electron (7 MeV, 20 MeV, 40 MeV) beams using thin LiF thermoluminescence dosimeters (TLD) in a perspex phantom. The beams were directed perpendicularly to the phantom surface. For 60Co and 6 MV photon beams the skin dose was evaluated in vivo at different beam arrangements and at a given reference dose. For 60Co, 6 MV and 42 MV photon beams wound dressing caused a dose increase on the surface of the perspex phantom by a factor of 1.65, 1.39 and 1.33 respectively. Using oblique or rotational techniques for 60Co and 6 MV photon irradiation the wound dressing increased the skin dose but less compared to perpendicular beam direction. For electron beams the skin dose is relatively high (from 84% to 92%) and an increase by a dressing has no clinical relevance (factor 1.03 to 1.05). The silicone-coated polyamide wound dressing causes no relevant skin dose increase during radiation treatment with electron beams and can be left on the skin during irradiation. During radiation treatment with photon beams like 60Co and 6 MV the protective procedure should be adapted to skin changes, in case of strong skin reactions a removal during the time of irradiation should be considered.

Geometric and mechanical evaluation of 3D-printing materials for skull base anatomical education and endoscopic surgery simulation – A first step to create reliable customized simulators

PubMed Central

Zemiti, Nabil; Caravaca Mora, Oscar; Subsol, Gérard; Captier, Guillaume; Lebrun, Renaud; Crampette, Louis; Mondain, Michel; Gilles, Benjamin

2017-01-01

Introduction Endoscopic skull base surgery allows minimal invasive therapy through the nostrils to treat infectious or tumorous diseases. Surgical and anatomical education in this field is limited by the lack of validated training models in terms of geometric and mechanical accuracy. We choose to evaluate several consumer-grade materials to create a patient-specific 3D-printed skull base model for anatomical learning and surgical training. Methods Four 3D-printed consumer-grade materials were compared to human cadaver bone: calcium sulfate hemihydrate (named Multicolor), polyamide, resin and polycarbonate. We compared the geometric accuracy, forces required to break thin walls of materials and forces required during drilling. Results All materials had an acceptable global geometric accuracy (from 0.083mm to 0.203mm of global error). Local accuracy was better in polycarbonate (0.09mm) and polyamide (0.15mm) than in Multicolor (0.90mm) and resin (0.86mm). Resin and polyamide thin walls were not broken at 200N. Forces needed to break Multicolor thin walls were 1.6–3.5 times higher than in bone. For polycarbonate, forces applied were 1.6–2.5 times higher. Polycarbonate had a mode of fracture similar to the cadaver bone. Forces applied on materials during drilling followed a normal distribution except for the polyamide which was melted. Energy spent during drilling was respectively 1.6 and 2.6 times higher on bone than on PC and Multicolor. Conclusion Polycarbonate is a good substitute of human cadaver bone for skull base surgery simulation. Thanks to short lead times and reasonable production costs, patient-specific 3D printed models can be used in clinical practice for pre-operative training, improving patient safety. PMID:29252993

Highly Porous, Rigid-Rod Polyamide Aerogels with Superior Mechanical Properties and Unusually High Thermal Conductivity.

PubMed

Williams, Jarrod C; Nguyen, Baochau N; McCorkle, Linda; Scheiman, Daniel; Griffin, Justin S; Steiner, Stephen A; Meador, Mary Ann B

2017-01-18

We report here the fabrication of polyamide aerogels composed of poly-p-phenylene-terephthalamide, the same backbone chemistry as DuPont's Kevlar. The all-para-substituted polymers gel without the use of cross-linker and maintain their shape during processing-an improvement over the meta-substituted cross-linked polyamide aerogels reported previously. Solutions containing calcium chloride (CaCl 2 ) and para-phenylenediamine (pPDA) in N-methylpyrrolidinone (NMP) at low temperature are reacted with terephthaloyl chloride (TPC). Polymerization proceeds over the course of 5 min resulting in gelation. Removal of the reaction solvent via solvent exchange followed by extraction with supercritical carbon dioxide provides aerogels with densities ranging from 0.1 to 0.3 g/cm 3 , depending on the concentration of calcium chloride, the formulated number of repeat units, n, and the concentration of polymer in the reaction mixture. These variables were assessed in a statistical experimental study to understand their effects on the properties of the aerogels. Aerogels made using at least 30 wt % CaCl 2 had the best strength when compared to aerogels of similar density. Furthermore, aerogels made using 30 wt % CaCl 2 exhibited the lowest shrinkage when aged at elevated temperatures. Notably, whereas most aerogel materials are highly insulating (thermal conductivities of 10-30 mW/m K), the polyamide aerogels produced here exhibit remarkably high thermal conductivities (50-80 mW/(m K)) at the same densities as other inorganic and polymer aerogels. These high thermal conductivities are attributed to efficient phonon transport by the rigid-rod polymer backbone. In conjunction with their low cost, ease of fabrication with respect to other polymer aerogels, low densities, and high mass-normalized strength and stiffness properties, these aerogels are uniquely valuable for applications such as lightweighting in consumer electronics, automobiles, and aerospace where weight reduction is desirable but trapping of heat may be undesirable-applications where other polymer aerogels have to date otherwise been unsuitable-creating new opportunities for commercialization of aerogels.

Comparison of aged polyamide powders for selective laser sintering

NASA Astrophysics Data System (ADS)

Martínez, A.; Ibáñez, A.; Sánchez, A.; León, M. A.

2012-04-01

Selective Laser Sintering (SLS) is an additive manufacturing technology in which a three-dimensional object is manufactured layer by layer by melting powder materials with heat generated from a CO2 laser. However, a disadvantage of sintered materials is that the unsintered powder material during the process can be reused only a limited number of cycles, as during the heating phase in the sintering chamber the material remains at a temperature near the fusion point for a certain period of time and lose properties. This work shows the study of two polyamides (PA12)-based powders used in SLS with the aim of understanding the modification of their properties mainly with the temperature and the time at which they are exposed during the processing.

Photo and Thermal Behavior of New Reinforced Polyamide-nanocomposite Montmorillonite on 2,3-Pyrazin Dicarboxylic Acid

NASA Astrophysics Data System (ADS)

Faghihi, Khalil; Samiei, Mojtaba; Hajibeygi, Mohsen

2012-06-01

Two new samples of reinforce polyamidemontmorillonite nanocomposites were synthesized by a convenient solution intercalation technique. Polyamide (PA) 3 as a source of polymer matrix was synthesized by the direct polycondensation reaction of pyrazine 2,3-dicarboxylic acid 1 with 4,4'-diamino diphenyl ether 2 in the presence of triphenyl phosphite (TPP), CaCl2, pyridine and N-methyl-2-pyrrolidone (NMP). The resulting nanocomposite films were characterized by Fourier transform infrared spectra (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The results showed that organo-modified clay was dispersed homogeneously in PA matrix. TGA indicated an enhancement of thermal stability of new nanocomposites compared with the pure polymer.

Correlation between water absorption and mechanical properties of polyamide 6 filled with layered double hydroxides (LDH)

NASA Astrophysics Data System (ADS)

Botan, R.; Pinheiro, I. F.; Ferreira, F. V.; Lona, L. M. F.

2018-06-01

Polyamide 6 (PA6)/layered double hydroxide (LDH) nanocomposites were prepared by in situ polymerization with different amount (1, 2, 3 wt%) and type (Zn/Cr-L and Zn/Cr-P) of LDHs. The thermal and mechanical properties and water absorption capacity of PA6/LDH nanocomposites were investigated and have shown that the addition of LDHs increases the crystallinity of the polymer and improves their mechanical properties, while decreases the water absorption capacity due to a barrier effect of LDHs. A correlation between mechanical properties and water absorption capacity was observed and discussed. This study provides new strategies for tuning PA6-based nanocomposite properties, leading a progress in the development on the advanced polymer materials.

Modification of thin-film polyamide membrane with multi-walled carbon nanotubes by interfacial polymerization

NASA Astrophysics Data System (ADS)

Al-Hobaib, Abdullah S.; Al-Sheetan, Kh. M.; Shaik, Mohammed Rafi; Al-Suhybani, M. S.

2017-12-01

Polyamide thin-film composite (TFC) was fabricated on polysulfone (PS-20) base by interfacial polymerization of aqueous m-phenylenediamine (MPD) solution and 1,3,5-benzenetricarbonyl trichloride (TMC) in hexane organic solution. Multi-wall carbon nanotubes (MWCNT) were carboxylated by heating MWCNT powder in a mixture of HNO3 and H2SO4 (1:3 v/v) at 70 °C under constant sonication for different periods. Polyamide nanocomposites were prepared by incorporating MWCNT and the carboxylated MWCNT (MWCNT-COOH) at different concentrations (0.001-0.009 wt%). The developed composites were analyzed by Fourier transform infrared spectroscopy-attenuated total reflection, scanning electron microscopy, transmission electron microscopy, contact angle measurement, determination of salt rejection and water permeate flux capabilities. The surface morphological studies displayed that the amalgamation of MWCNT considerably changed the surface properties of modified membranes. The surface hydrophilicity was increased as observed in the enhancement in water flux and pure water permeance, due to the presence of hydrophilic nanotubes. Salt rejection was obtained between 94 and 99% and varied water flux values for TFC-reference membrane, pristine-MWCNT in MPD, pristine-MWCNT in TMC and MWCNT-COOH in MPD were 20.5, 38, 40 and 43 L/m2h. The water flux and salt rejection performances revealed that the MWCNT-COOH membrane was superior membrane as compared to the other prepared membranes.

A novel method based on selective laser sintering for preparing high-performance carbon fibres/polyamide12/epoxy ternary composites

NASA Astrophysics Data System (ADS)

Zhu, Wei; Yan, Chunze; Shi, Yunsong; Wen, Shifeng; Liu, Jie; Wei, Qingsong; Shi, Yusheng

2016-09-01

A novel method based on selective laser sintering (SLS) process is proposed for the first time to prepare complex and high-performance carbon fibres/polyamide12/epoxy (CF/PA12/EP) ternary composites. The procedures are briefly described as follows: prepare polyamide12 (PA12) coated carbon fibre (CF) composite powder; build porous green parts by SLS; infiltrate the green parts with high-performance thermosetting epoxy (EP) resin; and finally cure the resin at high temperature. The obtained composites are a ternary composite system consisting of the matrix of novolac EP resin, the reinforcement of CFs and the transition thin layer of PA12 with a thickness of 595 nm. The SEM images and micro-CT analysis prove that the ternary system is a three-dimensional co-continuous structure and the reinforcement of CFs are well dispersed in the matrix of EP with the volume fraction of 31%. Mechanical tests show that the composites fabricated by this method yield an ultimate tensile strength of 101.03 MPa and a flexural strength of 153.43 MPa, which are higher than those of most of the previously reported SLS materials. Therefore, the process proposed in this paper shows great potential for manufacturing complex, lightweight and high-performance CF reinforced composite components in aerospace, automotive industries and other areas.

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

Elsasser, Brigitta M.; Schoenen, Iris; Fels, Gregor

Candida antarctica lipase B (CALB) efficiently catalyzes the ring-opening polymerization of lactones to high molecular weight products in good yield. In contrast, an efficient enzymatic synthesis of polyamides has so far not been described in the literature. This obvious difference in enzyme catalysis is the subject of our comparative study of the initial steps of a CALB catalyzed ring-opening polymerization of ε- caprolactone and ε-caprolactam. We have applied docking tools to generate the reactant state complex and performed quantum mechanical/molecular mechanical (QM/MM) calculations at the density functional theory (DFT) PBE0 level of theory to simulate the acylation of Ser105 bymore » the lactone and the lactam, respectively, via the corresponding first tetrahedral intermediates. We could identify a decisive difference in the accessibility of the two substrates in the ring-opening to the respective acyl enzyme complex as the attack of ε-caprolactam is hindered because of an energetically disfavored proton transfer during this part of the catalytic reaction while ε-caprolactone is perfectly processed along the widely accepted pathway using the catalytic triade of Ser105, His224, and Asp187. Since the generation of an acylated Ser105 species is the crucial step of the polymerization procedure, our results give an explanation for the unsatisfactory enzymatic polyamide formation and opens up new possibilities for targeted rational catalyst redesign in hope of an experimentally useful CALB catalyzed polyamide synthesis.« less

An efficient preparative procedure for main flavonoids from the peel of Trichosanthes kirilowii Maxim. using polyamide resin followed by semi-preparative high performance liquid chromatography.

PubMed

Li, Aifeng; Sun, Ailing; Liu, Renmin; Zhang, Yongqing; Cui, Jichun

2014-08-15

In this study, a simple and efficient preparative procedure was developed for preparation of seven flavonoids from the peel of Trichosanthes kirilowii Maxim. using polyamide resin followed by semi-preparative high performance liquid chromatography (SPHPLC). First, the ethyl acetate fraction from the peel of T. kirilowii Maxim. obtained "prefractionation" using polyamide resin, which yielded two subfractions. And then the two subfractions were isolated by SPHPLC with an isocratic elution of methanol-water. Finally, seven known flavonoids were purified from 35 g of ethyl acetate extract including quercetin-3-O-[α-l-rhamnose (1→2)-β-d-glucopyranosyl]-5-O-β-d-glucopyranoside (19 mg), quercetin-3-O-rutinoside (24 mg), apigenin-7-O-β-d-glucopyranoside (10mg), diosmetin-7-O-β-d-glucopyranoside (45 mg), luteolin (21 mg), apigenin (15 mg), and diosmetin (56 mg). The purities of the compounds were determined by HPLC and the chemical structures were confirmed by UV and NMR analysis. In the present study, a simple, effective, and rapid procedure was established for preparative separation of multiple components from the peel of T. kirilowii Maxim. Furthermore, it was scalable and economical, so it was a promising basis for large-scale preparation of flavonoids from other plant extracts. Copyright © 2014. Published by Elsevier B.V.

Humidity affects the performance of von Frey monofilaments.

PubMed

Werner, M U; Rotbøll-Nielsen, P; Ellehuus-Hilmersson, C

2011-05-01

Assessment of tactile and nociceptive thresholds of the skin with calibrated polyamide monofilaments is an established testing method both in animal and in human research. It is known that changes in relative humidity may affect the physical properties of the monofilaments. As this effect has only been studied in very small diameter monofilaments, used in neonatal research, we therefore studied complete sets of polyamide monofilaments. The effects were studied in a controlled climate chamber during six incremental changes in relative humidity from 20% to 79% (22-24°C). Following 24 h of equilibration at each humidity level, calibration with a precision scale was performed. A highly significant linear correlation between the natural logarithm (In) of the bending force and the von Frey number was observed at all humidity levels (r(2)>0.99, P<0.0001). An inverse linear relationship between relative humidity and In of the bending force for each monofilament was found (r(2)=0.95, P<0.0001). One percent increase in relative humidity corresponded to a 1-4% relative decrease in numerical bending force, depending on the diameter of the monofilament. A significant linear relationship was observed between the coefficient of variation and the relative humidity (r(2)=0.87, P<0.001). The data indicate that the hygroscopic properties of polyamide monofilaments must be taken into account for their reliable use in quantitative sensory testing.

Atomistic Model for the Polyamide Formation from β-Lactam Catalyzed by Candida Antarctica Lipase B

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

Baum, Iris; Elsasser, Brigitta M.; Schwab, Leendert

2011-04-01

Candida antarctica lipase B (CALB) is an established biocatalyst for a variety of transesterification, amidation, and polymerization reactions. In contrast to polyesters, polyamides are not yet generally accessible via enzymatic polymerization. In this regard, an enzyme-catalyzed ring-opening polymerization of {beta}-lactam (2-azetidinone) using CALB is the first example of an enzymatic polyamide formation yielding unbranched poly({beta}-alanine), nylon 3. The performance of this polymerization, however, is poor, considering the maximum chain length of 18 monomer units with an average length of 8, and the molecular basis of the reaction so far is not understood. We have employed molecular modeling techniques using dockingmore » tools, molecular dynamics, and QM/MM procedures to gain insight into the mechanistic details of the various reaction steps involved. As a result, we propose a catalytic cycle for the oligomerization of {beta}-lactam that rationalizes the activation of the monomer, the chain elongation by additional {beta}-lactam molecules, and the termination of the polymer chain. In addition, the processes leading to a premature chain termination are studied. Particularly, the QM/MM calculation enables an atomistic description of all eight steps involved in the catalytic cycle, which features an in situ-generated {beta}-alanine as the elongating monomer and which is compatible with the experimental findings.« less

A novel method based on selective laser sintering for preparing high-performance carbon fibres/polyamide12/epoxy ternary composites

PubMed Central

Zhu, Wei; Yan, Chunze; Shi, Yunsong; Wen, Shifeng; Liu, Jie; Wei, Qingsong; Shi, Yusheng

2016-01-01

A novel method based on selective laser sintering (SLS) process is proposed for the first time to prepare complex and high-performance carbon fibres/polyamide12/epoxy (CF/PA12/EP) ternary composites. The procedures are briefly described as follows: prepare polyamide12 (PA12) coated carbon fibre (CF) composite powder; build porous green parts by SLS; infiltrate the green parts with high-performance thermosetting epoxy (EP) resin; and finally cure the resin at high temperature. The obtained composites are a ternary composite system consisting of the matrix of novolac EP resin, the reinforcement of CFs and the transition thin layer of PA12 with a thickness of 595 nm. The SEM images and micro-CT analysis prove that the ternary system is a three-dimensional co-continuous structure and the reinforcement of CFs are well dispersed in the matrix of EP with the volume fraction of 31%. Mechanical tests show that the composites fabricated by this method yield an ultimate tensile strength of 101.03 MPa and a flexural strength of 153.43 MPa, which are higher than those of most of the previously reported SLS materials. Therefore, the process proposed in this paper shows great potential for manufacturing complex, lightweight and high-performance CF reinforced composite components in aerospace, automotive industries and other areas. PMID:27650254

Fabrication of semi-aromatic polyamide/spherical mesoporous silica nanocomposite reverse osmosis membrane with superior permeability

NASA Astrophysics Data System (ADS)

Li, Qiang; Yu, Hui; Wu, Feiyang; Song, Jie; Pan, Xianhui; Zhang, Meng

2016-02-01

Semi-aromatic polyamide (SAP)/spherical mesoporous silica nanocomposite reverse osmosis (RO) membrane was successfully fabricated using m-phenylene diamine aqueous solution and cyclohexane-1,3,5-tricarbonyl chloride/mesoporous-silica-sphere (MSS) organic solution as main raw materials. The experimental suggests that the microstructures and surface features are significantly different from those of the contrast samples (the full- and semi-aromatic polyamide membranes), including the surface morphology, polymer framework structure, surface charge density, hydrophilicity, and the thickness of barrier layer. It was observed that many MSSs with ca. 1.5 nm of pore size are evenly embedded on the surface of the fabricated SAP/MSS RO membrane. Furthermore, the separation performance testing results indicate that the permeabilities range from 62.53 to 72.73 L/m2 h with the increase of the introduced MSSs from 0.02 to 0.08 w/v % under 1.5 MPa operating pressure and 2000 mg/L NaCl solution, which is obviously better than the contrast samples. Simultaneously, their salt rejections can be still maintained at a comparable level (94.78-91.46%). The excellent separation performance of the nanocomposite RO membrane is closely related to the higher-freedom-degree semi-aromatic framework, the incorporation of MSSs, the improved surface hydrophilicity, the thinner barrier layer, and the enhanced surface negative charge density.

Synthesis and Properties of Cross-Linked Polyamide Aerogels

NASA Technical Reports Server (NTRS)

Williams, Jarrod; Meador, Mary Ann; McCorkle, Linda

2014-01-01

We report our ongoing research on polyamide aerogels made by step growth polymerization using a combination of terephthaloyl chloride, isophthaloyl chloride and m-phenylenediamine. Crosslinking of the amine capped polymer chains with 1,3,5-benzenetricarbonyl trichloride causes gelation in as little as two to five minutes. Removing the reaction solvent is accomplished through solvent exchange, followed by drying using supercritical CO2 extraction to give colorless aerogels with densities ranging from 0.07 to 0.33 grams per cubic centimeter and surface areas as high as 440 square meters per gram. Statistical experimental design methodology has been utilized to investigate dependence of properties of these aerogels, such as density, compressive modulus, and surface area, on changes in fabrication parameters including formulated number of amide oligomer repeat units (n-value), acid chloride (meta, para or combination), and solids concentration of solution used for gelation. For example, the density of these materials was found to be dependent on the acid chloride type and the solids concentration, but n was not a significant variable. However, surface area was significantly influenced by all three parameters. The polyamide aerogels represent a potential cost savings over previously reported polyimide aerogels, since monomers are all inexpensive and commercially available. Surface area and density were both highest when 100 terephthaloyl chloride was used but a combination of 5 solid concentration, 100 terephthaloyl chloride and n of 20 gave the best combination of properties.

Bulk chlorine uptake by polyamide active layers of thin-film composite membranes upon exposure to free chlorine-kinetics, mechanisms, and modeling.

PubMed

Powell, Joshua; Luh, Jeanne; Coronell, Orlando

2014-01-01

We studied the volume-averaged chlorine (Cl) uptake into the bulk region of the aromatic polyamide active layer of a reverse osmosis membrane upon exposure to free chlorine. Volume-averaged measurements were obtained using Rutherford backscattering spectrometry with samples prepared at a range of free chlorine concentrations, exposure times, and mixing, rinsing, and pH conditions. Our volume-averaged measurements complement previous studies that have quantified Cl uptake at the active layer surface (top ≈ 7 nm) and advance the mechanistic understanding of Cl uptake by aromatic polyamide active layers. Our results show that surface Cl uptake is representative of and underestimates volume-averaged Cl uptake under acidic conditions and alkaline conditions, respectively. Our results also support that (i) under acidic conditions, N-chlorination followed by Orton rearrangement is the dominant Cl uptake mechanism with N-chlorination as the rate-limiting step; (ii) under alkaline conditions, N-chlorination and dechlorination of N-chlorinated amide links by hydroxyl ion are the two dominant processes; and (iii) under neutral pH conditions, the rates of N-chlorination and Orton rearrangement are comparable. We propose a kinetic model that satisfactorily describes Cl uptake under acidic and alkaline conditions, with the largest discrepancies between model and experiment occurring under alkaline conditions at relatively high chlorine exposures.

Separation and purification of epigallocatechin-3-gallate (EGCG) from green tea using combined macroporous resin and polyamide column chromatography.

PubMed

Jin, Xin; Liu, Mingyan; Chen, Zaixing; Mao, Ruikun; Xiao, Qinghuan; Gao, Hua; Wei, Minjie

2015-10-01

Epigallocatechin-3-gallate (EGCG) is a major bioactive ingredient of green tea that produces beneficial neuroprotective effects. In this paper, to optimize the EGCG enrichment, thirteen macroporous resins with different chemical and physical properties were systemically evaluated. Among the thirteen tested resins, the H-bond resin HPD826 exhibited best adsorption/desorption capabilities and desorption ratio, as well as weakest affinity for caffeine. The absorption of EGCG on the HPD826 resin followed the pseudo-second-order kinetics and Langmuir isotherm model. The separation parameters of EGCG were optimized by dynamic adsorption/desorption experiments with the HPD826 resin column. Under the optimal condition, the content of EGCG in the 30% ethanol eluent increased by 5.8-fold from 7.7% to 44.6%, with the recovery yield of 72.1%. After further purification on a polyamide column, EGCG with 74.8% purity was obtained in the 40-50% ethanol fraction with a recovery rate of 88.4%. In addition, EGCG with 95.1% purity could be easily obtained after one-step crystallization in distilled water. Our study suggests that the combined macroporous resin and polyamide column chromatography is a simple method for large-scale separation and purification of EGCG from natural plants for food and pharmaceutical applications. Copyright © 2015 Elsevier B.V. All rights reserved.

49 CFR 178.33b-5 - Material.

Code of Federal Regulations, 2010 CFR

2010-10-01

... of polyethylene terephthalate (PET), polyethylene napthalate (PEN), polyamide (Nylon) or a blend of PET, PEN, ethyl vinyl alcohol (EVOH) and/or Nylon. (b) Material with seams, cracks, laminations or...

Absorbing TiOx thin film enabling laser welding of polyurethane membranes and polyamide fibers

PubMed Central

Amberg, Martin; Haag, Alexander; Storchenegger, Raphael; Rupper, Patrick; Lehmeier, Frederike; Rossi, René M; Hegemann, Dirk

2015-01-01

We report on the optical properties of thin titanium suboxide (TiOx) films for applications in laser transmission welding of polymers. Non-absorbing fibers were coated with TiOx coatings by reactive magnetron sputtering. Plasma process parameters influencing the chemical composition and morphology of the deposited thin films were investigated in order to optimize their absorption properties. Optical absorption spectroscopy showed that the oxygen content of the TiOx coatings is the main parameter influencing the optical absorbance. Overtreatment (high power plasma input) of the fiber surface leads to high surface roughness and loss of mechanical stability of the fiber. The study shows that thin substoichiometric TiOx films enable the welding of very thin polyurethane membranes and polyamide fibers with improved adhesion properties. PMID:27877837

Absorbing TiOx thin film enabling laser welding of polyurethane membranes and polyamide fibers

NASA Astrophysics Data System (ADS)

Amberg, Martin; Haag, Alexander; Storchenegger, Raphael; Rupper, Patrick; Lehmeier, Frederike; Rossi, René M.; Hegemann, Dirk

2015-10-01

We report on the optical properties of thin titanium suboxide (TiOx) films for applications in laser transmission welding of polymers. Non-absorbing fibers were coated with TiOx coatings by reactive magnetron sputtering. Plasma process parameters influencing the chemical composition and morphology of the deposited thin films were investigated in order to optimize their absorption properties. Optical absorption spectroscopy showed that the oxygen content of the TiOx coatings is the main parameter influencing the optical absorbance. Overtreatment (high power plasma input) of the fiber surface leads to high surface roughness and loss of mechanical stability of the fiber. The study shows that thin substoichiometric TiOx films enable the welding of very thin polyurethane membranes and polyamide fibers with improved adhesion properties.

Absorbing TiO x thin film enabling laser welding of polyurethane membranes and polyamide fibers.

PubMed

Amberg, Martin; Haag, Alexander; Storchenegger, Raphael; Rupper, Patrick; Lehmeier, Frederike; Rossi, René M; Hegemann, Dirk

2015-10-01

We report on the optical properties of thin titanium suboxide (TiO x ) films for applications in laser transmission welding of polymers. Non-absorbing fibers were coated with TiO x coatings by reactive magnetron sputtering. Plasma process parameters influencing the chemical composition and morphology of the deposited thin films were investigated in order to optimize their absorption properties. Optical absorption spectroscopy showed that the oxygen content of the TiO x coatings is the main parameter influencing the optical absorbance. Overtreatment (high power plasma input) of the fiber surface leads to high surface roughness and loss of mechanical stability of the fiber. The study shows that thin substoichiometric TiO x films enable the welding of very thin polyurethane membranes and polyamide fibers with improved adhesion properties.

Polyamide nanofiltration membranes to remove aniline in aqueous solutions.

PubMed

Hidalgo, A M; León, G; Gómez, M; Murcia, M D; Bernal, M D; Ortega, S

2014-01-01

Aniline is commonly used in a number of industrial processes. It is known to be a harmful and persistent pollutant and its presence in wastewater requires treatment before disposal. In this paper, the effectiveness of nanofiltration (NF) to remove aniline from aqueous solutions is studied in a flat membrane test module using two thin-layer composite membranes of polyamide (NF97 and NF99HF). The influence of different operational variables (applied pressure, feed concentration and pH) on the removal of aniline from synthetic aqueous solutions was analysed. The experimental NF results are compared with results previously obtained by reverse osmosis. Based on this comparative study, the effective order for aniline rejection is: HR98PP > NF97 > DESAL3B > SEPA-MS05 > NF99HF.

High-performance multi-functional reverse osmosis membranes obtained by carbon nanotube·polyamide nanocomposite

PubMed Central

Inukai, Shigeki; Cruz-Silva, Rodolfo; Ortiz-Medina, Josue; Morelos-Gomez, Aaron; Takeuchi, Kenji; Hayashi, Takuya; Tanioka, Akihiko; Araki, Takumi; Tejima, Syogo; Noguchi, Toru; Terrones, Mauricio; Endo, Morinobu

2015-01-01

Clean water obtained by desalinating sea water or by purifying wastewater, constitutes a major technological objective in the so-called water century. In this work, a high-performance reverse osmosis (RO) composite thin membrane using multi-walled carbon nanotubes (MWCNT) and aromatic polyamide (PA), was successfully prepared by interfacial polymerization. The effect of MWCNT on the chlorine resistance, antifouling and desalination performances of the nanocomposite membranes were studied. We found that a suitable amount of MWCNT in PA, 15.5 wt.%, not only improves the membrane performance in terms of flow and antifouling, but also inhibits the chlorine degradation on these membranes. Therefore, the present results clearly establish a solid foundation towards more efficient large-scale water desalination and other water treatment processes. PMID:26333385

Selective Laser Sintering of Nano Al2O3 Infused Polyamide

PubMed Central

Warnakula, Anthony; Singamneni, Sarat

2017-01-01

Nano Al2O3 polyamide composites are evaluated for processing by selective laser sintering. A thermal characterization of the polymer composite powders allowed us to establish the possible initial settings. Initial experiments are conducted to identify the most suitable combinations of process parameters. Based on the results of the initial trials, more promising ranges of different process parameters could be identified. The post sintering characterization showed evidence of sufficient inter-particle sintering and intra-layer coalescence. While the inter-particle coalescence gradually improved, the porosity levels slightly decreased with increasing laser power. The nano-filler particles tend to agglomerate around the beads along the solid tracks, possibly due to Van der Walls forces. The tensile stress results showed an almost linear increase with increasing nano-filler content. PMID:28773220

Simple Microwave-Assisted Synthesis of Amphiphilic Carbon Quantum Dots from A3/B2 Polyamidation Monomer Set.

PubMed

Choi, Yujin; Jo, Seongho; Chae, Ari; Kim, Young Kwang; Park, Jeong Eun; Lim, Donggun; Park, Sung Young; In, Insik

2017-08-23

Highly fluorescent and amphiphilic carbon quantum dots (CQDs) were prepared by microwave-assisted pyrolysis of citric acid and 4,7,10-trioxa-1,13-tridecanediamine (TTDDA), which functioned as an A 3 and B 2 polyamidation type monomer set. Gram quantities of fluorescent CQDs were easily obtained within 5 min of microwave heating using a household microwave oven. Because of the dual role of TTDDA, both as a constituting monomer and as a surface passivation agent, TTDDA-based CQDs showed a high fluorescence quantum yield of 29% and amphiphilic solubility in various polar and nonpolar solvents. These properties enable the wide application of TTDDA-based CQDs as nontoxic bioimaging agents, nanofillers for polymer composites, and down-converting layers for enhancing the efficiency of Si solar cells.

Composite impact strength improvement through a fiber/matrix interphase

NASA Technical Reports Server (NTRS)

Cavano, P. J.; Winters, W. E.

1975-01-01

Research was conducted to improve the impact strength and toughness of fiber/resin composites by means of a fiber coating interphase. Graphite fiber/epoxy resin composites were fabricated with four different fiber coating systems introduced in a matrix-fiber interphase. Two graphite fibers, a high strength and a high modulus type, were studied with the following coating systems: chemical vapor deposited boron, electroless nickel, a polyamide-imide resin and a thermoplastic polysulfone resin. Evaluation methods included the following tests: Izod, flexure, shear fracture toughness, longitudinal and transverse tensile, and transverse and longitudinal compression. No desirable changes could be effected with the high strength fiber, but significant improvements in impact performance were observed with the polyamide-imide resin coated high modulus fiber with no loss in composite modulus.

21 CFR 177.2450 - Polyamide-imide resins.

Code of Federal Regulations, 2011 CFR

2011-04-01

... than 500 parts per million. Residual monomers are determined by gas chromatography (the gas chromatography method titled “Amide-Imide Polymer Analysis—Analysis of Monomer Content,” is incorporated by...

Tetrakis-amido high flux membranes

DOEpatents

McCray, S.B.

1989-10-24

Composite RO membranes of a microporous polymeric support and a polyamide reaction product of a tetrakis-aminomethyl compound and a polyacylhalide are disclosed, said membranes exhibiting high flux and good chlorine resistance.

Tetrakis-amido high flux membranes

DOEpatents

McCray, Scott B.

1989-01-01

Composite RO membranes of a microporous polymeric support and a polyamide reaction product of a tetrakis-aminomethyl compound and a polyacylhalide are disclosed, said membranes exhibiting high flux and good chlorine resistance.

Rheological characteristics of pulp-fibre-reinforced polyamide composite

NASA Astrophysics Data System (ADS)

Cherizol, Robenson

Recently, there has been increasing interest in utilizing pulp-fibre-reinforced, higher-melting-temperature engineering thermoplastics, such as polyamide 11 and polyamide 6 in the automotive, aerospace and construction industries. Moreover, the rheological characteristics of those composites were not fully investigated in relation to processing approaches and pulp-fibre aspect ratio. Two processing approaches were used in this thesis: the extrusion compounding process and the Brabender mixer technique using inorganic salt lithium chloride (LiCl). The fibre-length distribution and content, and the densities of the PA11 and modified bio-based PA11 after compounding, were investigated and found to coincide with the final properties of the resultant composites. The effects of fibre content, fibre aspect ratio, and fibre length on rheological properties were studied. The rheological properties of high-yield-pulp (HYP) -reinforced bio-based Polyamide 11 (PA11) composite (HYP/PA11) were experimentally investigated using a capillary rheometer. Experimental test results showed a steep decrease in shear viscosity with increasing shear rate; this melt-flow characteristic corresponds to shear-thinning behavior in HYP/PA11. The morphological properties of HYP/PA11 composite were examined using SEM: no fibre pullout was observed. This was due to the presence of the hydrogen bond, which created excellent compatibility between high-yield pulp fibre and bio-based Nylon 11. The viscoelastic characteristics of biocomposites derived from natural-fibre-reinforced thermoplastic polymers and of predictive models were reviewed to understand their rheological behavior. Novel predicted multiphase rheological-model-based polymer, fibre, and interphasial phases were developed. Rheological characteristics of the composite components influenced the development of resultant microstructures; this in turn affected the mechanical characteristics of a multiphase composite. Experimental and theoretical test results of HYP/PA11 showed a steep decrease in apparent viscosity with increasing shear rate; this melt-flow characteristic corresponds to shear-thinning behavior in HYP/PA11.The nonlinear mathematical model to predict the rheological behavior of HYP/PA11was validated experimentally at 200?C and 5000S-1 shear rate.

Solvent-based and solvent-free characterization of low solubility and low molecular weight polyamides by mass spectrometry: a complementary approach.

PubMed

Barrère, Caroline; Hubert-Roux, Marie; Lange, Catherine M; Rejaibi, Majed; Kebir, Nasreddine; Désilles, Nicolas; Lecamp, Laurence; Burel, Fabrice; Loutelier-Bourhis, Corinne

2012-06-15

Polyamides (PA) belong to the most used classes of polymers because of their attractive chemical and mechanical properties. In order to monitor original PA design, it is essential to develop analytical methods for the characterization of these compounds that are mostly insoluble in usual solvents. A low molecular weight polyamide (PA11), synthesized with a chain limiter, has been used as a model compound and characterized by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). In the solvent-based approach, specific solvents for PA, i.e. trifluoroacetic acid (TFA) and hexafluoroisopropanol (HFIP), were tested. Solvent-based sample preparation methods, dried-droplet and thin layer, were optimized through the choice of matrix and salt. Solvent-based (thin layer) and solvent-free methods were then compared for this low solubility polymer. Ultra-high-performance liquid chromatography/electrospray ionization (UHPLC/ESI)-TOF-MS analyses were then used to confirm elemental compositions through accurate mass measurement. Sodium iodide (NaI) and 2,5-dihydroxybenzoic acid (2,5-DHB) are, respectively, the best cationizing agent and matrix. The dried-droplet sample preparation method led to inhomogeneous deposits, but the thin-layer method could overcome this problem. Moreover, the solvent-free approach was the easiest and safest sample preparation method giving equivalent results to solvent-based methods. Linear as well as cyclic oligomers were observed. Although the PA molecular weights obtained by MALDI-TOF-MS were lower than those obtained by (1)H NMR and acido-basic titration, this technique allowed us to determine the presence of cyclic and linear species, not differentiated by the other techniques. TFA was shown to induce modification of linear oligomers that permitted cyclic and linear oligomers to be clearly highlighted in spectra. Optimal sample preparation conditions were determined for the MALDI-TOF-MS analysis of PA11, a model of polyamide analogues. The advantages of the solvent-free and solvent-based approaches were shown. Molecular weight determination using MALDI was discussed. Copyright © 2012 John Wiley & Sons, Ltd.

Control of multiwall carbon nanotubes dispersion in polyamide6 matrix: An assessment through electrical conductivity

NASA Astrophysics Data System (ADS)

Kodgire, Pravin V.; Bhattacharyya, Arup R.; Bose, Suryasarathi; Gupta, Nitin; Kulkarni, Ajit R.; Misra, Ashok

2006-12-01

The homogeneous dispersion of carbon nanotubes (CNT) remains a hindrance in exploiting the exceptional properties associated with CNT in polymer/CNT composites. Here we present for the first time the key role of sodium salt of 6-aminohexanoic acid (Na-AHA) in assisting debundling the multiwall carbon nanotubes (MWNT) through specific interactions leading to homogeneous dispersion within polyamide6 (PA6) matrix during melt-mixing. The composite fabricated via this route exhibits low electrical percolation threshold of 0.5 wt% at room temperature, the lowest reported value in this system so far. FTIR and Raman spectroscopy reveal the existence of 'cation-π' interaction between Na-AHA and MWNT. The phenomenon of reactive coupling between amine functionality of Na-AHA and acid end group of PA6 during melt-mixing is also established.

Deciphering the genomic targets of alkylating polyamide conjugates using high-throughput sequencing

PubMed Central

Chandran, Anandhakumar; Syed, Junetha; Taylor, Rhys D.; Kashiwazaki, Gengo; Sato, Shinsuke; Hashiya, Kaori; Bando, Toshikazu; Sugiyama, Hiroshi

2016-01-01

Chemically engineered small molecules targeting specific genomic sequences play an important role in drug development research. Pyrrole-imidazole polyamides (PIPs) are a group of molecules that can bind to the DNA minor-groove and can be engineered to target specific sequences. Their biological effects rely primarily on their selective DNA binding. However, the binding mechanism of PIPs at the chromatinized genome level is poorly understood. Herein, we report a method using high-throughput sequencing to identify the DNA-alkylating sites of PIP-indole-seco-CBI conjugates. High-throughput sequencing analysis of conjugate 2 showed highly similar DNA-alkylating sites on synthetic oligos (histone-free DNA) and on human genomes (chromatinized DNA context). To our knowledge, this is the first report identifying alkylation sites across genomic DNA by alkylating PIP conjugates using high-throughput sequencing. PMID:27098039

DNA sequence-selective C8-linked pyrrolobenzodiazepine-heterocyclic polyamide conjugates show anti-tubercular-specific activities.

PubMed

Brucoli, Federico; Guzman, Juan D; Basher, Mohammad A; Evangelopoulos, Dimitrios; McMahon, Eleanor; Munshi, Tulika; McHugh, Timothy D; Fox, Keith R; Bhakta, Sanjib

2016-12-01

New chemotherapeutic agents with novel mechanisms of action are in urgent need to combat the tuberculosis pandemic. A library of 12 C8-linked pyrrolo[2,1-c][1,4]benzodiazepine (PBD)-heterocyclic polyamide conjugates (1-12) was evaluated for anti-tubercular activity and DNA sequence selectivity. The PBD conjugates were screened against slow-growing Mycobacterium bovis Bacillus Calmette-Guérin and M. tuberculosis H 37 Rv, and fast-growing Escherichia coli, Pseudomonas putida and Rhodococcus sp. RHA1 bacteria. DNase I footprinting and DNA thermal denaturation experiments were used to determine the molecules' DNA recognition properties. The PBD conjugates were highly selective for the mycobacterial strains and exhibited significant growth inhibitory activity against the pathogenic M. tuberculosis H 37 Rv, with compound 4 showing MIC values (MIC=0.08 mg l -1 ) similar to those of rifampin and isoniazid. DNase I footprinting results showed that the PBD conjugates with three heterocyclic moieties had enhanced sequence selectivity and produced larger footprints, with distinct cleavage patterns compared with the two-heterocyclic chain PBD conjugates. DNA melting experiments indicated a covalent binding of the PBD conjugates to two AT-rich DNA-duplexes containing either a central GGATCC or GTATAC sequence, and showed that the polyamide chains affect the interactions of the molecules with DNA. The PBD-C8 conjugates tested in this study have a remarkable anti-mycobacterial activity and can be further developed as DNA-targeted anti-tubercular drugs.

A novel TFC forward osmosis (FO) membrane supported by polyimide (PI) microporous nanofiber membrane

NASA Astrophysics Data System (ADS)

Chi, Xiang-Yu; Zhang, Ping-Yun; Guo, Xue-Jiao; Xu, Zhen-Liang

2018-01-01

A novel interfacial polymerization (IP) procedure on polyimide (PI) microporous nanofiber membrane support with mean pore size 1.27 μm was reported. Using m-phenylenediamine (MPD) as aqueous phase monomer, trimesoyl chloride (TMC) as organic phase monomer, ethanol as aqueous phase co-solvent, thin-film composite (TFC) forward osmosis (FO) membrane was fabricated by two IP procedures. The first IP procedure with the unconventional order (ie, the membrane was immersed in the TMC organic phase first, then in the co-solvent ethanol-water MPD aqueous phase) was used to diminish the pore size of PI microporous nanofiber membrane support for the formation of the polyamide layer. The secondary IP procedure was employed to form the relatively dense polyamide layer with conventional order (ie, the membrane was immersed in the co-solvent ethanol-water MPD aqueous phase first, then in the TMC organic phase). The experimental results showed that higher ethanol concentration led to the relatively higher pure water permeability in RO process and osmotic water flux in FO process, whereas NaCl rejection in RO process decreased and reverse salt flux increased. The specific salt flux (Js/Jv) of TFC FO PI nanofiber membrane (PIN-2-4) could be as low as 0.095 g/L in FO mode. These results could be attributed to influence of the addition of ethanol into aqueous phase on the surface morphology, hydrophilicity and polyamide layer structure.

[Preparation of poly(methyl acrylate) microfluidic chips surface-modified by hyperbranched polyamide ester and their application in the separation of biomolecules].

PubMed

Liu, Bing; Lin, Donge; Xu, Lin; Lei, Yanhui; Bo, Qianglong; Shou, Chongqi

2012-05-01

The surface of poly (methyl acrylate) (PMMA) microfluidic chips were modified using hyperbranched polyamide ester via chemical bonding. The contact angles of the modified chips were measured. The surface morphology was observed by scanning electron microscope (SEM) and stereo microscope. The results showed that the surface of the modified chips was coated by a dense, uniform, continuous, hydrophilic layer of hyperbranched polyamide ester. The hydrophilic of the chip surface was markedly improved. The contact angle of the chips modified decreased from 89.9 degrees to 29.5 degrees. The electro osmotic flow (EOF) in the modified microchannel was lower than that in the unmodified microchannel. Adenosine and L-lysine were detected and separated via the modified PMMA microfluidic chips. Compared with unmodified chips, the modified chips successfully separated the two biomolecules. The detection peaks were clear and sharp. The separation efficiencies of adenosine and L-lysine were 8.44 x 10(4) plates/m and 9.82 x 10(4) plates/m respectively, and the resolutions (Rs) was 5.31. The column efficiencies and resolutions of the modified chips were much higher than those of the unmodified chips. It was also observed that the modified chips possessed good reproducibility of migration time. This research may provide a new and effective method to improve the hydrophilicity of the PMMA surface and the application of PMMA microfluidic chips in the determination of trace biomolecules.

The Antibacterial Polyamide 6-ZnO Hierarchical Nanofibers Fabricated by Atomic Layer Deposition and Hydrothermal Growth

NASA Astrophysics Data System (ADS)

Wang, Zhengduo; Zhang, Li; Liu, Zhongwei; Sang, Lijun; Yang, Lizhen; Chen, Qiang

2017-06-01

In this paper, we report the combination of atomic layer deposition (ALD) with hydrothermal techniques to deposit ZnO on electrospun polyamide 6 (PA 6) nanofiber (NF) surface in the purpose of antibacterial application. The micro- and nanostructures of the hierarchical fibers are characterized by field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), and scanning transmission electron microscopy (STEM). We find that NFs can grow into "water lily"- and "caterpillar"-like shapes, which depend on the number of ALD cycles and the hydrothermal reaction period. It is believed that the thickness of ZnO seed layer by ALD process and the period in hydrothermal reaction have the same importance in crystalline growth and hierarchical fiber formation. The tests of antibacterial activity demonstrate that the ZnO/PA 6 core-shell composite fabricated by the combination of ALD with hydrothermal are markedly efficient in suppressing bacteria survivorship.

Investigation of electrically conducting yarns for use in textile actuators

NASA Astrophysics Data System (ADS)

Martinez, Jose G.; Richter, Klaus; Persson, Nils-Krister; Jager, Edwin W. H.

2018-07-01

Textile actuators are an emerging technology to develop biomimetic actuators with synergetic actuation. They are composed of a passive fabric coated with an electroactive polymer providing with mechanical motion. Here we used different conducting yarns (polyamide + carbon, silicon + carbon, polyamide + silver coated, cellulose + carbon, polyester + 2 × INOX 50 μm, polyester + 2 × Cu/Sn and polyester + gold coated) to develop such textile actuators. It was possible to coat them through direct electrochemical methods, which should provide with an easier and more cost-effective fabrication process. The conductivity and the electrochemical properties of the yarns were sufficient to allow the electropolymerization of the conducting polymer polypyrrole on the yarns. The electropolymerization was carried out and both the linear and angular the actuation of the yarns was investigated. These yarns may be incorporated into textile actuators for assistive prosthetic devices easier and cheaper to get and at the same time with good mechanical performance are envisaged.

Antithrombogenic Polymer Coating.

DOEpatents

Huang, Zhi Heng; McDonald, William F.; Wright, Stacy C.; Taylor, Andrew C.

2003-01-21

An article having a non-thrombogenic surface and a process for making the article are disclosed. The article is formed by (i) coating a polymeric substrate with a crosslinked chemical combination of a polymer having at least two amino substituted side chains, a crosslinking agent containing at least two crosslinking functional groups which react with amino groups on the polymer, and a linking agent containing a first functional group which reacts with a third functional group of the crosslinking agent, and (ii) contacting the coating on the substrate with an antithrombogenic agent which covalently bonds to a second functional group of the linking agent. In one example embodiment, the polymer is a polyamide having amino substituted alkyl chains on one side of the polyamide backbone, the crosslinking agent is a phosphine having the general formula (A).sub.3 P wherein A is hydroxyalkyl, the linking agent is a polyhydrazide and the antithrombogenic agent is heparin.

Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR FT-IR) Mapping Coupled with Multivariate Curve Resolution (MCR) for Studying the Miscibility of Chlorobutyl Rubber/Polyamide-12 Blends.

PubMed

Tang, Yongjiao; Jing, Nan; Zhang, Pudun

2015-11-01

A series of chlorobutyl rubber/polyamide-12 (CIIR/PA-12) blends compatibilized by different amounts of maleic anhydride (MAH) grafted polypropylene (PP-g-MAH) were investigated by attenuated total reflection Fourier transform infrared spectroscopy (ATR FT-IR) mapping. Multivariate curve resolution (MCR) was used to process the FT-IR images. Both the spectra of pure components in the blends and their concentration distributions in a micro-region were acquired. Our results demonstrated that the blend with 15 parts per hundred rubber PP-g-MAH showed the best miscibility. An amide interphase and an imide interphase were inferred by analyzing the spectra of MCR component 3 of the blends with and without PP-g-MAH, respectively. Correspondingly, two different compatibilizing mechanisms were proposed for these blends.

Colorimetric Humidity Sensors Based on Electrospun Polyamide/CoCl2 Nanofibrous Membranes.

PubMed

You, Ming-Hao; Yan, Xu; Zhang, Jun; Wang, Xiao-Xiong; He, Xiao-Xiao; Yu, Miao; Ning, Xin; Long, Yun-Ze

2017-12-01

Humidity indicators based on composite polyamide 66/cobalt chloride (PA66/CoCl 2 ) nanofibrous membranes (NFMs) were successfully fabricated by electrospinning. A series of NFMs with various weight percentage of CoCl 2 to PA66 were prepared, and their humidity sensitivity based on color changing and quartz crystal microbalance (QCM) were studied. Due to the color change property of cobalt chloride, the as-spun composite NFMs show obviously macroscopic color change from blue to pink as relative humidity (RH) increasing from 12.4 to 97.2%. Moreover, the QCM detection showed a linear dependence on the RH changing and exhibited short response/recovery time (less than 65.4 s/11 s), small hysteresis (less than 11%), good reproducibility, and stability. Owing to the above double sensitive mechanism on RH, the PA66/CoCl 2 composite NFM may show great potential applications from meticulous to coarse.

Processing and Mechanical Properties of Macro Polyamide Fiber Reinforced Concrete

PubMed Central

Jeon, Joong Kyu; Kim, WooSeok; Jeon, Chan Ki; Kim, Jin Cheol

2014-01-01

This study developed a macro-sized polyamide (PA) fiber for concrete reinforcement and investigated the influence of the PA fiber on flexural responses in accordance with ASTM standards. PA fibers are advantageous compared to steel fibers that are corrosive and gravitated. The macro-sized PA fiber significantly improved concrete ductility and toughness. Unlike steel fibers, the PA fibers produced two peak bending strengths. The first-peaks occurred near 0.005 mm of deflection and decreased up to 0.5 mm of deflection. Then the bending strength increased up to second-peaks until the deflections reached between 1.0 and 1.5 mm. The averaged flexural responses revealed that PA fiber content did not significantly influence flexural responses before L/600, but had significant influence thereafter. Toughness performance levels were also determined, and the results indicated more than Level II at L/600 and Level IV at others. PMID:28788265

Processing and Mechanical Properties of Macro Polyamide Fiber Reinforced Concrete.

PubMed

Jeon, Joong Kyu; Kim, WooSeok; Jeon, Chan Ki; Kim, Jin Cheol

2014-11-26

This study developed a macro-sized polyamide (PA) fiber for concrete reinforcement and investigated the influence of the PA fiber on flexural responses in accordance with ASTM standards. PA fibers are advantageous compared to steel fibers that are corrosive and gravitated. The macro-sized PA fiber significantly improved concrete ductility and toughness. Unlike steel fibers, the PA fibers produced two peak bending strengths. The first-peaks occurred near 0.005 mm of deflection and decreased up to 0.5 mm of deflection. Then the bending strength increased up to second-peaks until the deflections reached between 1.0 and 1.5 mm. The averaged flexural responses revealed that PA fiber content did not significantly influence flexural responses before L /600, but had significant influence thereafter. Toughness performance levels were also determined, and the results indicated more than Level II at L /600 and Level IV at others.

Removal of Manganese from Solution using Polyamide Membrane

NASA Astrophysics Data System (ADS)

Mathaba, M.; Sithole, N.; Mashifana, T.

2018-03-01

The work demonstrates the performance of polyamide membrane in the removal of manganese ions from single salt aqueous solution simulating real acid mine drainage. The membrane was tested using a dead-end filtration cell with manganese sulphate was used to prepare a feed solution. The membrane flux and metal rejection was evaluated. Effect of operating parameters such as pH, initial feed concentration and pressure on membrane performance was investigated. The pressure was varied between 10 and 15 bar and it was observed that increasing the pressure increases the membrane flux. Acidic pH conditions contributed to the removal of the contaminate as Mn2+ ions are freely at low pH. The percentage rejection was found to be 63.5 to 77.6 % as concentration is increased from 290 ppm to 321 ppm for a feed solution. The membrane showed satisfactory results in removing metal ions from solution.

Low Velocity Impact Behavior of Glass Filled Fiber-Reinforced Thermoplastic Engine Components

PubMed Central

Mouti, Zakaria; Westwood, Keith; Kayvantash, Kambiz; Njuguna, James

2010-01-01

This paper concerns automotive parts located underneath the engine and in particular the engine oil pan. Classically made of stamped steel or cast aluminum, new developments have allowed the manufacture oil pans with polyamide 66 reinforced by 35% weight of short glass fiber. However, polyamides have some limitations and the most significant is their response to localized impact loading. The nature of the impact considered here is of a typical stone collected from the road and projected into the oil pan.  Low velocity impact investigations were carried out using a gas gun and drop weight tower.  The study shows that the design of the oil pan has a significant contribution in the shock absorption. In addition to the material properties, the geometry and the ribbing both cleverly combined, increase the impact resistance of the component significantly. Areas of oil pan design improvement have been identified and conclusions drawn.

Colorimetric Humidity Sensors Based on Electrospun Polyamide/CoCl2 Nanofibrous Membranes

NASA Astrophysics Data System (ADS)

You, Ming-Hao; Yan, Xu; Zhang, Jun; Wang, Xiao-Xiong; He, Xiao-Xiao; Yu, Miao; Ning, Xin; Long, Yun-Ze

2017-05-01

Humidity indicators based on composite polyamide 66/cobalt chloride (PA66/CoCl2) nanofibrous membranes (NFMs) were successfully fabricated by electrospinning. A series of NFMs with various weight percentage of CoCl2 to PA66 were prepared, and their humidity sensitivity based on color changing and quartz crystal microbalance (QCM) were studied. Due to the color change property of cobalt chloride, the as-spun composite NFMs show obviously macroscopic color change from blue to pink as relative humidity (RH) increasing from 12.4 to 97.2%. Moreover, the QCM detection showed a linear dependence on the RH changing and exhibited short response/recovery time (less than 65.4 s/11 s), small hysteresis (less than 11%), good reproducibility, and stability. Owing to the above double sensitive mechanism on RH, the PA66/CoCl2 composite NFM may show great potential applications from meticulous to coarse.

Structure and Properties of Melt-spun Bio-based Polyamide/Eu(TTA)3Phen Composite fibers

NASA Astrophysics Data System (ADS)

Li, Yunye; Lou, Pengfei; Jia, Qingxiu

2018-02-01

In this paper, the bio-based polyamide (PA ) was melt polymerized from four bio-based monomers. Composites of the bio-based PA and europium complex Eu(TTA)3Phen were prepared through solution mixing using N, N-Dimethylformamide (DMF) and formic acid as the mixed solvent, and then composite fibers were obtained by melt spinning method. The structure and properties of the melt-spun composite fibers were characterized by FTIR and SEM. The results indicated that the Eu(TTA)3Phen complex, with the average diameter below 300 nm, was homogeneously dispersed in the PA matrix. FTIR spectra indicated that the coordination bond between carbonyl of BDIS and Eu(TTA)3Phen complex formed, which was also confirmed by the mechanical properties. The initial modulus and breaking strength of these fibers can arrived at 2.5GPa and 0.3GPa, respectively.

Analysis of linear and cyclic oligomers in polyamide-6 without sample preparation by liquid chromatography using the sandwich injection method. II. Methods of detection and quantification and overall long-term performance.

PubMed

Mengerink, Y; Peters, R; Kerkhoff, M; Hellenbrand, J; Omloo, H; Andrien, J; Vestjens, M; van der Wal, S

2000-05-05

By separating the first six linear and cyclic oligomers of polyamide-6 on a reversed-phase high-performance liquid chromatographic system after sandwich injection, quantitative determination of these oligomers becomes feasible. Low-wavelength UV detection of the different oligomers and selective post-column reaction detection of the linear oligomers with o-phthalic dicarboxaldehyde (OPA) and 3-mercaptopropionic acid (3-MPA) are discussed. A general methodology for quantification of oligomers in polymers was developed. It is demonstrated that the empirically determined group-equivalent absorption coefficients and quench factors are a convenient way of quantifying linear and cyclic oligomers of nylon-6. The overall long-term performance of the method was studied by monitoring a reference sample and the calibration factors of the linear and cyclic oligomers.

Fiber optic strain measurements using an optically-active polymer

NASA Astrophysics Data System (ADS)

Buckley, Leonard J.; Neumeister, Gary C.

1992-03-01

A study encompassing the use of an optically-active polymer as the strain-sensing medium in an organic matrix composite was performed. Several compounds were synthesized for use as the inner cladding material for silica fiber-optic cores. These materials include a diacetylene containing polyamide. It is possible to dynamically modify the optical properties of these materials through changes in applied strain or temperature. By doing so the characteristic absorption in the visible is reversibly shifted to a higher energy state. The polymer-coated fiber-optic cores were initially studied in epoxy resin. Additionally, one of the polyamide/diacetylene polymers was studied in a spin-fiber form consisting of 15 micron filaments assembled in multifilament tows. The most promising configuration and materials were then investigated further by embedding in graphite/epoxy composite laminates. In each case the shift in the visible absorption peak was monitored as a function of applied mechanical strain.

Combining metabolic engineering and electrocatalysis: Application to the production of polyamides from sugar

DOE PAGES

Suastegui, Miguel; Matthiesen, John E.; Carraher, Jack M.; ...

2016-01-14

Here, biorefineries aim to convert biomass into a spectrum of products ranging from biofuels to specialty chemicals. To achieve economically sustainable conversion, it is crucial to streamline the catalytic and downstream processing steps. In this work, a route that combines bio- and electrocatalysis to convert glucose into bio-based unsaturated nylon-6,6 is reported. An engineered strain of Saccharomyces cerevisiae was used as the initial biocatalyst for the conversion of glucose into muconic acid, with the highest reported muconic acid titer of 559.5 mg L –1 in yeast. Without any separation, muconic acid was further electrocatalytically hydrogenated to 3-hexenedioic acid in 94more » % yield despite the presence of biogenic impurities. Bio-based unsaturated nylon-6,6 (unsaturated polyamide-6,6) was finally obtained by polymerization of 3-hexenedioic acid with hexamethylenediamine.« less

Modelling poly(p-phenylene teraphthalamide) at Extreme Tensile Loading using Reactive Potentials

NASA Astrophysics Data System (ADS)

Yilmaz, Dundar

2015-03-01

Aromatic polyamides classified as rigid-rod polymers due to orientation of their monomers. Because of their excellent mechanical and thermal properties, aramids are widely used in the industry. For example DuPont's brand Kevlar, for its commercial aromatic polyamide polymer, due to wide usage of this polymer in ballistic applications, habitually used as a nickname for bulletproof vests. In order to engineer these ballistic fabrics, material properties of aramid fibers should be studied. In this work we focused on the poly(p-phenylene teraphthalamide) PPTA fiber, known as brand name Kevlar. We employed Reactive potentials to simulate PPTA polymer under tensile loading. We first simulated both amorphous and crystalline phases of PPTA. We also introduced defects with varying densities. We further analysed the recorded atomic positions data to understand how tensile load distributed and failure mechanisms at extreme tensile loads. This work supported by TUBITAK under Grant No: 113F358.

Preparation of tea catechins using polyamide.

PubMed

Ye, Jian-Hui; Wang, Liu-Xiang; Chen, Hao; Dong, Jun-Jie; Lu, Jian-Liang; Zheng, Xin-Qiang; Wu, Ming-Yan; Liang, Yue-Rong

2011-02-01

An adsorption separation method using Polyamide-6 (PA) as an adsorbent was developed to separate catechins from green tea extract. The adsorption capacity of total catechins for PA was 193.128 mg g⁻¹ with an adsorption selectivity coefficient K(A)(B) of total catechins over caffeine 21.717, which was better than macroporous resin model HPD 600. The Langmuir model and the pseudo-second order mode were primely fitted to describe its equilibrium data and adsorption kinetics, respectively. PA column separation by two-step elution using water and 80% (v/v) aqueous ethanol was established to prepare catechins complex which contained 670.808 mg g⁻¹ total catechins and 1.828 mg g⁻¹ caffeine. It is considered that PA was a promising adsorbent for selective isolation of catechins. Copyright © 2010 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

An on-line coupling of nanofibrous extraction with column-switching high performance liquid chromatography - A case study on the determination of bisphenol A in environmental water samples.

PubMed

Háková, Martina; Chocholoušová Havlíková, Lucie; Chvojka, Jiří; Solich, Petr; Šatínský, Dalibor

2018-02-01

Polyamide 6 nanofiber polymers were used as modern sorbents for on-line solid phase extraction (SPE) coupled with liquid chromatography. The on-line SPE system was tested for the determination of bisphenol A in river water samples. Polyamide nanofibers were prepared using needleless electrospinning, inserted into a mini-column cartridge (5 × 4.6mm) and coupled with HPLC. The effect of column packing and the amount of polyamide 6 on extraction efficiency was tested and the packing process was optimized. The proposed method was performed using a 50-µL sample injection followed by an on-line nanofibrous extraction procedure. The influence of the washing mobile phase on the retention of bisphenol A during the extraction procedure was evaluated. Ascentis ® Express C18 (10cm × 4.6mm) core-shell column was used as an analytical column. Fluorescence detection wavelengths (λ ex = 225nm and λ em = 320nm) were used for identification and quantification of Bisphenol A in river waters. The linearity was tested in the range from 2 to 500µgL -1 (using nine calibration points). The limits of detection and quantification were 0.6 and 2µgL -1 , respectively. The developed method was successfully used for the determination of bisphenol A in various samples of river waters in the Czech Republic (The Ohře, Labe, Nisa, Úpa, and Opava Rivers). Copyright © 2017 Elsevier B.V. All rights reserved.

3D-Printed Craniosynostosis Model: New Simulation Surgical Tool.

PubMed

Ghizoni, Enrico; de Souza, João Paulo Sant Ana Santos; Raposo-Amaral, Cassio Eduardo; Denadai, Rafael; de Aquino, Humberto Belém; Raposo-Amaral, Cesar Augusto; Joaquim, Andrei Fernandes; Tedeschi, Helder; Bernardes, Luís Fernando; Jardini, André Luiz

2018-01-01

Craniosynostosis is a complex disease once it involves deep anatomic perception, and a minor mistake during surgery can be fatal. The objective of this report is to present novel 3-dimensional-printed polyamide craniosynostosis models that can improve the understanding and treatment complex pathologies. The software InVesalius was used for segmentation of the anatomy image (from 3 patients between 6 and 9 months old). Afterward, the file was transferred to a 3-dimensional printing system and, with the use of an infrared laser, slices of powder PA 2200 were consecutively added to build a polyamide model of cranial bone. The 3 craniosynostosis models allowed fronto-orbital advancement, Pi procedure, and posterior distraction in the operating room environment. All aspects of the craniofacial anatomy could be shown on the models, as well as the most common craniosynostosis pathologic variations (sphenoid wing elevation, shallow orbits, jugular foramen stenosis). Another advantage of our model is its low cost, about 100 U.S. dollars or even less when several models are produced. Simulation is becoming an essential part of medical education for surgical training and for improving surgical safety with adequate planning. This new polyamide craniosynostosis model allowed the surgeons to have realistic tactile feedback on manipulating a child's bone and permitted execution of the main procedures for anatomic correction. It is a low-cost model. Therefore our model is an excellent option for training purposes and is potentially a new important tool to improve the quality of the management of patients with craniosynostosis. Copyright © 2017 Elsevier Inc. All rights reserved.

40 CFR 63.522 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-07-01

... Hazardous Air Pollutants for Epoxy Resins Production and Non-Nylon Polyamides Production § 63.522... that are related to the production of BLR or WSR, including process vents, storage tanks, wastewater... process involving the bulk movement of material through sequential manufacturing steps. Mass, temperature...

Compounds containing meta-biphenylenedioxy moieties and polymers therefrom

NASA Technical Reports Server (NTRS)

St.clair, Terry L. (Inventor); Pratt, John Richard (Inventor)

1993-01-01

Two monomers containing meta-biphenylenedioxy moieties were prepared. One monomer, a diamine, is used to prepare polyimide, polyamide, and epoxy polymers. The other monomer, a dianhydride, was used to prepare polyimide polymers. These polymers are used to make films, coatings, and selective membranes.

MODELING OF MULTICOMPONENT PERVAPORATION FOR REMOVAL OF VOLATILE ORGANIC COMPOUNDS FROM WATER

EPA Science Inventory

A resistance-in-series model was used to study the pervaporation of multiple volatile organic compounds (VOCs)-water mixtures. Permeation experiments were carried out for four membranes: poly(dimethylsiloxane) (PDMS), polyether-block-polyamides (PEBA), polyurethane (PUR) and sil...

Preparation and Characterization of Thin-Film Composite Membrane with Nanowire-Modified Support for Forward Osmosis Process

PubMed Central

Low, Ze-Xian; Liu, Qi; Shamsaei, Ezzatollah; Zhang, Xiwang; Wang, Huanting

2015-01-01

Internal concentration polarization (ICP) in forward osmosis (FO) process is a characteristic problem for asymmetric thin-film composite (TFC) FO membrane which leads to lower water flux. To mitigate the ICP effect, modification of the substrates’ properties has been one of the most effective methods. A new polyethersulfone-based ultrafiltration membrane with increased surface porosity and high water flux was recently produced by incorporating Zn2GeO4 nanowires. The composite membrane was used as a substrate for the fabrication of TFC FO membrane, by coating a thin layer of polyamide on top of the substrate. The substrate and the nanowires were characterized by a range of techniques such as SEM, XRD, and contact angle goniometry. The water permeability and molecular weight cut-offs (MWCO) of the substrate; and the FO performance of the TFC membrane were also determined. The Zn2GeO4-modified membrane showed ~45% increase in water permeability and NaCl salt rejection of 80% under RO mode. In FO mode, the ratio of water flux to reverse solute flux was also improved. However, lower FO flux was obtained which could be due to ICP. The result shows that Zn2GO4 nanowire may be used as a modifier to the substrate to improve the quality of the polyamide layer on the substrate to improve the flux and selectivity, but not as effective in reducing ICP. This work demonstrates that the incorporation of nanomaterials to the membrane substrate may be an alternative approach to improve the formation of polyamide skin layer to achieve better FO performance. PMID:25803239

Effect of acidic aqueous solution on chemical and physical properties of polyamide NF membranes

NASA Astrophysics Data System (ADS)

Jun, Byung-Moon; Kim, Su Hwan; Kwak, Sang Kyu; Kwon, Young-Nam

2018-06-01

This work was systematically investigated the effects of acidic aqueous solution (15 wt% sulfuric acid as model wastewater from smelting process) on the physical and chemical properties of commercially available nanofiltration (NF) polyamide membranes, using piperazine (PIP)-based NE40/70 membranes and m-phenylene diamine (MPD)-based NE90 membrane. Surface properties of the membranes were studied before and after exposure to strong acid using various analytical tools: Scanning Electron Microscopy (SEM), Attenuated Total Reflectance-Fourier Transform Infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), contact angle analyzer, and electrophoretic light scattering spectrophotometer. The characterization and permeation results showed piperazine-based NE40/70 membranes have relatively lower acid-resistance than MPD-based NE90 membrane. Furthermore, density functional theory (DFT) calculation was also conducted to reveal the different acid-tolerances between the piperazine-based and MPD-based polyamide membranes. The easiest protonation was found to be the protonation of oxygen in piperazine-based monomer, and the N-protonation of the monomer had the lowest energy barrier in the rate determining step (RDS). The calculations were well compatible with the surface characterization results. In addition, the energy barrier in RDS is highly correlated with the twist angle (τD), which determines the delocalization of electrons between the carbonyl πCO bond and nitrogen lone pair, and the tendency of the twist angle was also maintained in longer molecules (dimer and trimer). This study clearly explained why the semi-aromatic membrane (NE40/70) is chemically less stable than the aromatic membrane (NE90) given the surface characterizations and DFT calculation results.

ENVIRONMENTAL TECHNOLOGY VERIFICATION REPORT--EVERMORE PAINTS AND COATINGS INC. FORMULA 5 COATING

EPA Science Inventory

This report is of a test of the pollution prevention capabilities of a polyamide-epoxy-silicone modified paint coating. It was analyzed for volatile organic emissions, hazardous air pollutants, film thickness, gloss, appearance, MEK rub resistance, abrasion resistance and other ...

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.

Synthesis and Characterization of Partial Biobased Furan Polyamides

DTIC Science & Technology

2014-02-01

Approved for public release; distribution is unlimited. NOTICES Disclaimers The...Weapons and Materials Research Directorate, ARL Approved for public release; distribution is unlimited...ii REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704-0188 Public reporting burden for this collection of information is estimated to average

Polyimides containing meta-biphenylenedioxy moieties and articles prepared therefrom

NASA Technical Reports Server (NTRS)

St.clair, Terry L. (Inventor); Pratt, Richard (Inventor)

1995-01-01

Two monomers containing meta-biphenylenedioxy moieties were prepared. One monomer, a diamine, is used to prepare polyimide, polyamide, and epoxy polymers. The other monomer, a dianhydride, was used to prepared polyimide polymers. These polymers are used to make films, coatings, and selective membranes.

Fabrication and characterization of drug-loaded nano-hydroxyapatite/polyamide 66 scaffolds modified with carbon nanotubes and silk fibroin

PubMed Central

Yao, Meng-Zhu; Huang-Fu, Ming-Yi; Liu, Hui-Na; Wang, Xia-Rong; Sheng, Xiaoxia; Gao, Jian-Qing

2016-01-01

Nano-hydroxyapatite/polyamide 66 (nHA/PA66) porous scaffolds were fabricated by a phase inversion method. Carbon nanotubes (CNTs) and silk fibroin (SF) were used to modify the surface of the nHA/PA66 scaffolds by freeze-drying and cross-linking. Dexamethasone was absorbed to the CNTs to promote the osteogenic differentiation of bone mesenchymal stem cells (BMSCs). The cell viability of BMSCs was investigated by changing the concentration of the CNT dispersion, and the most biocompatible scaffold was selected. In addition, the morphology and mechanical property of the scaffolds were investigated. The results showed that the nHA/PA66 scaffolds modified with CNTs and SF met the requirements of bone tissue engineering scaffolds. The dexamethasone-loaded CNT/SF-nHA/PA66 composite scaffold promoted the osteogenic differentiation of BMSCs, and the drug-loaded scaffolds are expected to function as effective bone tissue engineering scaffolds. PMID:27920525

A Process for Preparing 1,3-Diamino-5-Pentafluorosulfanylbenzene and Polymers Therefrom

NASA Technical Reports Server (NTRS)

St.clair, Anne K. (Inventor); St.clair, Terry L. (Inventor); Thrasher, Joseph S. (Inventor)

1991-01-01

Diamines have shown their utility in the formation of many polymers. Examples of these polymers include polyimides, polyamides, and epoxies. The properties of these polymers are often dependent on the diamine which is used to make the polymer. By the present invention, a process was developed to make a diamine containing pentafluorosulfanylbenzene moiety. This process involves two steps: the preparation of a dinitro precursor and the reduction of the dinitro compound to form the diamine. This diamine was then reacted with various dianhydrides, diacidchlorides, and epoxy resins to yield the corresponding polyimide, polyamide, and epoxy polymers. These polymers were then used to make films, a wire coating enamel, and a semi-permeable membrane. The novelty of this invention resides in the process to make the diamine. Traditionally, dinitro compounds are reduced with hydrazine or a catalyst such as palladium on charcoal. The catalyst which is used in this invention is platinum oxide. When this catalyst is used, it makes it possible to form a polymer-grade diamine.

Chemiluminescence and reactivity of the composites based on blends of polypropylene and polyamide

NASA Astrophysics Data System (ADS)

Vorontsov, N. V.; Popov, A. A.; Margolin, A. L.

2017-12-01

The effect of the composition of blends based on isotactic polypropylene (PP) and aliphatic polyamide 6/66-4 (PA) on the rate of photo-oxidation of their mixtures in air at room temperature has been studied. The decay of photoinduced chemiluminescence was studied to determine the kinetics of peroxyl radical termination in composites and the rate constants of this process depending on the composition of the mixtures. In the presence of PA, the rate of photo-oxidation of mixtures is much higher than the rates of photo-oxidation of separately taken components, PP and PA. Thus, the kinetics of photo-oxidation of mixtures differs from the simple sum of photo-oxidation kinetics of PP and PA, which should be expected in the absence of chemical and physical interaction of the components of the mixture. A decrease in the rate constants due to PA additives indicates a decrease in the mobility of molecules in the composites and explains the observed increase in photo-oxidation of mixtures.

Photo-triggered release in polyamide nanosized capsules

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

Marturano, V.; Ambrogi, V.; Cerruti, P.

2014-05-15

In this work, nanosized capsules based on a lightly cross-linked polyamide containing azobenzene moieties in the main chain were synthesized by miniemulsion interfacial polymerization. The obtained nanocapsules were loaded either with toluene or with the fluorescent probe coumarin-6 as a core. Diameters of the nanocapsules were in the 100-900 nm range, depending on the selected emulsion conditions. The morphology and shape of the samples were observed by TEM and SEM while the emulsion droplets and nanocapsules size was measured by DLS. Under continuous UV irradiation the polymer underwent E-Z photoisomerization allowing the release of the encapsulated material. Variation in diametermore » of the nanocapsules with the time of UV irradiation was detected through DLS analysis. 10-30% growth was observed, depending on the sample. The kinetics of release of coumarin-6 was followed by spectrofluorimetry in ethanol. In absence of irradiation, the fluorescence intensity appeared to be constant over time, while it increased when the sample was irradiated with 360 nm UV light.« less

The Reach of Linear Protein-DNA Dimerizers

PubMed Central

Stafford, Ryan L.; Dervan, Peter B.

2008-01-01

A protein-DNA dimerizer constructed from a DNA-binding pyrrole-imidazole polyamide and the peptide FYPWMK facilitates binding of the natural transcription factor Exd to an adjacent DNA site. Previous dimerizers have been constructed with the peptide attached to an internal pyrrole monomer in an overall branched oligomer. Linear oligomers constructed by attaching the peptide to the polyamide C-terminus expand the range of protein-DNA dimerization to six additional DNA sites. Replacing the FYPWMK hexapeptide with a WM dipeptide, which was previously functional in branched compounds, does not lead to a functional linear dimerizer. Instead, inserting an additional lysine generates a minimal, linear WMK tripeptide conjugate that maintains the activity of the larger FYPWMK dimerizers in a single DNA-binding site orientation. These studies provide insight into the importance of linker length and composition, binding site spacing and orientation, and the protein-binding domain content that are important for the optimization of protein DNA-dimerizers suitable for biological experiments. PMID:17949089

Interfacial Interaction in Anodic Aluminum Oxide Templates Modifies Morphology, Surface Area, and Crystallization of Polyamide-6 Nanofibers.

PubMed

Xue, Junhui; Xu, Yizhuang; Jin, Zhaoxia

2016-03-08

Here, we demonstrated that, when the precipitation process of polyamide-6 (PA6) solution happens in cylindrical channels of an anodized aluminum oxide membrane (AAO), interface interactions between a solid surface, solvent, non-solvent, and PA6 will influence the obtained polymer nanostructures, resulting in complex morphologies, increased surface area, and crystallization changes. With the enhancing interaction of PA6 and the AAO surface, the morphology of PA6 nanostructures changes from solid nanofibers, mesoporous, to bamboo-like, while at the same time, metastable γ-phase domains increase in these PA6 nanostructures. Brunauer-Emmett-Teller (BET) surface areas of solid, bamboo-like, and mesoporous PA6 nanofibers rise from 16, 20.9, to 25 m(2)/g. This study shows that interfacial interaction in AAO template fabrication can be used in manipulating the morphology and crystallization of one-dimensional polymer nanostructures. It also provides us a simple and novel method to create porous PA6 nanofibers with a large surface area.

Single-Walled Carbon Nanotube Film Supported Nanofiltration Membrane with a Nearly 10 nm Thick Polyamide Selective Layer for High-Flux and High-Rejection Desalination.

PubMed

Zhu, Yuzhang; Xie, Wei; Gao, Shoujian; Zhang, Feng; Zhang, Wenbin; Liu, Zhaoyang; Jin, Jian

2016-09-01

Fabricating nanofiltration (NF) membranes with high permeating flux and simultaneous high rejection rate for desalination is rather significant and highly desired. A new avenue is reported in this work to design NF membrane by using polydopamine wrapped single-walled carbon nanotube (PD/SWCNTs) ultrathin film as support layer instead of the use of traditional polymer-based underlying layers. Thanks to the high porosity, smooth surface, and more importantly optimal hydrophilic surface of PD/SWCNTs film, a defect-free polyamide selective layer for NF membrane with thickness of as thin as 12 nm is achieved. The obtained NF membrane exhibits an extremely high performance with a permeating flux of 32 L m -2 h -1 bar -1 and a rejection rate of 95.9% to divalent ions. This value is two to five times higher than the traditional NF membranes with similar rejection rate. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Numerical simulation of fiber interaction in short-fiber injection-molded composite using different cavity geometries

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

Thi, Thanh Binh Nguyen, E-mail: nttbinh@kit.ac.jp; Yokoyama, Atsushi, E-mail: yokoyama@kit.ac.jp; Hamanaka, Senji

The theoretical fiber-interaction model for calculating the fiber orientation in the injection molded short fiber/thermoplastic composite parts was proposed. The proposed model included the fiber dynamics simulation in order to obtain an equation of the global interaction coefficient and accurate estimate of the fiber interacts at all orientation states. The steps to derive the equation for this coefficient in short fiber suspension as a function of the fiber aspect ratio, volume fraction and general shear rate are delineated. Simultaneously, the high-resolution 3D X-ray computed tomography system XVA-160α was used to observe fiber distribution of short-glass-fiber-reinforced polyamide specimens using different cavitymore » geometries. The fiber orientation tensor components are then calculated. Experimental orientation measurements of short-glass-fiber-reinforced polyamide is used to check the ability of present theory for predicting orientation. The experiments and predictions show a quantitative agreement and confirm the basic understanding of fiber orientation in injection-molded composites.« less

Effect of surface treatments on physicomechanical, stain-resist, and UV protection properties of wool fabrics

NASA Astrophysics Data System (ADS)

Hassan, Mohammad M.; Leighs, Samuel J.

2017-10-01

The surface of wool fabrics is frequently modified to make them shrink-resistant, water repellent and also to improve their handle properties. In this work, we investigated the effect of common surface modification treatments on fabric stain-resistance, hydrophilicity and UV absorption performance. The surface of wool fabrics was modified by chlorination and also by reacting the chlorinated wool fabrics with a polyamide, a fibre-reactive amino-functional siloxane and a fluorocarbon polymer. The surface of the various treated fabrics was characterised by ATR-FTIR, contact angle measurement and scanning electron microscopy. The effect of surface modification on the tensile strength, surface hydrophilicity, stain-resistance, and UV absorption capacity of the fabric was investigated. It was found that all the treatments except the treatment with the amino-functional siloxane polymer slightly improved the tensile strength of the fabric. The chlorination treatment and the treatment with the polyamide resin made the fabric hydrophilic, and fluorocarbon and silicone resin treatment made the fabric hydrophobic.

Construction of flame retardant coating on polyamide 6.6 via UV grafting of phosphorylated chitosan and sol-gel process of organo-silane.

PubMed

Kundu, Chanchal Kumar; Wang, Xin; Hou, Yanbei; Hu, Yuan

2018-02-01

Phosphorylated chitosan (PCS) was synthesized and grafted onto the surface of polyamide 6.6 (PA 6.6) fabrics via UV-induced grafting polymerization in order to improve the flame retardant properties. Subsequently, PCS grafted PA 6.6 fabrics were modified by (3-aminopropyl) triethoxysilane (APTES) through sol-gel process in order to form a cross-linking coating. The results obtained from the vertical burning test indicated that only the PCS grafted and simultaneously sol-gel treated fabrics could stop the melt dripping. A maximum reduction (30%) in the peak heat release rate was achieved for the PA6.6-PCS-4W-SG fabric sample. The optimal flame retardant effect was achieved for the PA6.6 fabrics treated by PCS and APTES simultaneously, which was attributed to the joint effect of thermal shielding exerted by the silica and char-forming effect derived from PCS. Copyright © 2017 Elsevier Ltd. All rights reserved.

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.

Preparative separation and purification of rosmarinic acid from perilla seed meal via combined column chromatography.

PubMed

Tang, Weizhuo; Sun, Baoshan; Zhao, Yuqing

2014-02-01

In this study, the preparative separation and purification of rosmarinic acid (RA) from perilla seed meal (PSM), which is a by-product of edible oil production, was achieved using combined column chromatography over macroporous and polyamide resins. To optimize the RA enrichment process, the performance and separation characteristics of nine selected macroporous resins with different chemical and physical properties were investigated. SP825 resin was the most effective: the content of RA increased from 0.27% in the original extract to 16.58% in the 50% ethanol fraction (a 61.4-fold increase). During further purification treatment on polyamide resin, 90.23% pure RA could be obtained in the 70% ethanol fraction. RA with a higher purity (>95%) could also be easily obtained using one crystallization operation. The proposed method is simple, easily operated, cost-effective, and environmentally friendly and is suitable for both large-scale RA production and waste management. Copyright © 2013 Elsevier B.V. All rights reserved.

Preparation and Properties of a Novel Microcrystalline Cellulose-Filled Composites Based on Polyamide 6/High-Density Polyethylene

PubMed Central

Xu, Shihua; Yi, Shunmin; He, Jun; Wang, Haigang; Fang, Yiqun; Wang, Qingwen

2017-01-01

In the present study, lithium chloride (LiCl) was utilized as a modifier to reduce the melting point of polyamide 6 (PA6), and then 15 wt % microcrystalline cellulose (MCC) was compounded with low melting point PA6/high-density polyethylene (HDPE) by hot pressing. Crystallization analysis revealed that as little as 3 wt % LiCl transformed the crystallographic forms of PA6 from semi-crystalline to an amorphous state (melting point: 220 °C to none), which sharply reduced the processing temperature of the composites. LiCl improved the mechanical properties of the composites, as evidenced by the fact that the impact strength of the composites was increased by 90%. HDPE increased the impact strength of PA6/MCC composites. In addition, morphological analysis revealed that incorporation of LiCl and maleic anhydride grafted high-density polyethylene (MAPE) improved the interfacial adhesion. LiCl increased the glass transition temperature of the composites (the maximum is 72.6 °C). PMID:28773169

Numerical simulation of fiber interaction in short-fiber injection-molded composite using different cavity geometries

NASA Astrophysics Data System (ADS)

Thi, Thanh Binh Nguyen; Yokoyama, Atsushi; Hamanaka, Senji; Yamashita, Katsuhisa; Nonomura, Chisato

2016-03-01

The theoretical fiber-interaction model for calculating the fiber orientation in the injection molded short fiber/thermoplastic composite parts was proposed. The proposed model included the fiber dynamics simulation in order to obtain an equation of the global interaction coefficient and accurate estimate of the fiber interacts at all orientation states. The steps to derive the equation for this coefficient in short fiber suspension as a function of the fiber aspect ratio, volume fraction and general shear rate are delineated. Simultaneously, the high-resolution 3D X-ray computed tomography system XVA-160α was used to observe fiber distribution of short-glass-fiber-reinforced polyamide specimens using different cavity geometries. The fiber orientation tensor components are then calculated. Experimental orientation measurements of short-glass-fiber-reinforced polyamide is used to check the ability of present theory for predicting orientation. The experiments and predictions show a quantitative agreement and confirm the basic understanding of fiber orientation in injection-molded composites.

Evaluation of two different epidural catheters in clinical practice. narrowing down the incidence of paresthesia!

PubMed

Bouman, E A C; Gramke, H F; Wetzel, N; Vanderbroeck, T H T; Bruinsma, R; Theunissen, M; Kerkkamp, H E M; Marcus, M A E

2007-01-01

Although epidural anesthesia is considered safe, several complications may occur during puncture and insertion of a catheter. Incidences of paresthesia vary between 0.2 and 56%. A prospective, open, cohort-controlled pilot study was conducted in 188 patients, ASA I-III, age 19-87 years, scheduled for elective surgery and epidural anesthesia. We evaluated a 20 G polyamide (standard) catheter and a 20 G combined polyurethane-polyamide (new) catheter. Spontaneous reactions upon catheter-insertion, paresthesia on questioning, inadvertent dural or intravascular puncture, and reasons for early catheter removal were recorded. The incidence of paresthesia reported spontaneously was 21.3% with the standard catheter and 16.7% with the new catheter. Systematically asking for paresthesia almost doubled the paraesthesia rate. Intravascular cannulation occurred in 5%. No accidental dural punctures occurred. An overall incidence of 13.3% of technical problems led to early catheter removal. The new catheter was at least equivalent to the standard regarding epidural success rate and safety : rate of paresthesia, intravascular and dural cannulation.

Comparison of biofouling mechanisms between cellulose triacetate (CTA) and thin-film composite (TFC) polyamide forward osmosis membranes in osmotic membrane bioreactors.

PubMed

Wang, Xinhua; Zhao, Yanxiao; Yuan, Bo; Wang, Zhiwei; Li, Xiufen; Ren, Yueping

2016-02-01

There are two types of popular forward osmosis (FO) membrane materials applied for researches on FO process, cellulose triacetate (CTA) and thin film composite (TFC) polyamide. However, performance and fouling mechanisms of commercial TFC FO membrane in osmotic membrane bioreactors (OMBRs) are still unknown. In current study, its biofouling behaviors in OMBRs were investigated and further compared to the CTA FO membrane. The results indicated that β-D-glucopyranose polysaccharides and microorganisms accounted for approximately 77% of total biovolume on the CTA FO membrane while β-D-glucopyranose polysaccharides (biovolume ratio of 81.1%) were the only dominant biofoulants on the TFC FO membrane. The analyses on the biofouling structure implied that a tighter biofouling layer with a larger biovolume was formed on the CTA FO membrane. The differences in biofouling behaviors including biofoulants composition and biofouling structure between CTA and TFC FO membranes were attributed to different membrane surface properties. Copyright © 2015 Elsevier Ltd. All rights reserved.

Polyamide 6-LiCl nanofibrous membrane as low-temperature regenerative desiccant with improved stability.

PubMed

Jiang, Fengjing; Dai, Li; Yao, Ye

2018-05-04

Polyamide 6-LiCl (PA 6-LiCl) electrospun nanofibrous membranes (NFMs) have been successfully prepared as novel solid desiccant materials. The PA 6 NFM with 20% LiCl mass ratio had a sorption capacity of 1.8 g g -1 at 25 °C and 95% relative humidity, which was 4 times more than that of silica gels. The desorption isobars of the NFMs indicated that over 85% of sorbed water in the NFMs can be desorbed at about 50 °C, and the low regeneration temperature made it promising as an energy-saving desiccant material. The experimental results manifested that the sorption/desorption kinetics of the NFMs better fit the pseudo-second order model. According to scanning electron microscope images and the cycle experiment, the NFMs were also found to possess notably improved stability against moisture and could be recycled with little degradation of performance, which confirmed the practicability of the new desiccant membranes.

The uptake of macroplastic & microplastic by demersal & pelagic fish in the Northeast Atlantic around Scotland.

PubMed

Murphy, Fionn; Russell, Marie; Ewins, Ciaran; Quinn, Brian

2017-09-15

This study reports plastic ingestion in various fish found from coastal and offshore sites in Scottish marine waters. Coastal samples consisted of three demersal flatfish species (n=128) collected from the East and West coasts of Scotland. Offshore samples consisted of 5 pelagic species and 4 demersal species (n=84) collected from the Northeast Atlantic. From the coastal fish sampled, 47.7% of the gastrointestinal tracts contained macroplastic and microplastic. Of the 84 pelagic and demersal offshore fish, only 2 (2.4%) individuals from different species had ingested plastic identified as a clear polystyrene fibre and a black polyamide fibre. The average number of plastic items found per fish from all locations that had ingested plastic was 1.8 (±1.7) with polyamide (65.3%), polyethylene terephthalate (14.4%) and acrylic (14.4%) being the three most commonly found plastics. This study adds to the existing data on macroplastic and microplastic ingestion in fish species. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

Ultrafiltration and endotoxin removal from dialysis fluids.

PubMed

Di Felice, A; Cappelli, G; Facchini, F; Tetta, C; Cornia, F; Aimo, G; Lusvarghi, E

1993-06-01

Biocompatibility in hemodialysis is now regarded as a multifactorial problem and dialysate represents a main risk. Pyrogenic fractions mostly coming from gram-negative bacteria easily pass through dialysis membrane, either by backdiffusion or by backfiltration, and induce blood cell activation. To demonstrate the long-term efficiency of a 2 m2 polyamide ultrafilter in producing a pyrogen free solution, we used an experimental circuit ultrafiltering for 240 hours (500 ml/min) a bicarbonate dialysate contaminated (5 to 48 EU/ml) by a Pseudomonas aeruginosa filtrate. The efficiency was monitored by LAL-test and IL-1 PBMC so to detect not only lipid A containing endotoxins but also other cytokines inducing bacterial fractions. At the post-ultrafilter sampling port the LAL-test was < 0.005 to 0.034 EU/ml; IL-1 PBMC was below the detection limit (20 pg/ml) being 27 to 63 pg/ml at the pre-ultrafilter level. Polyamide ultrafiltration represents an efficient system to obtain an endotoxin-free dialysate and a single filter works up to 240 hours.

Polyamide 6-LiCl nanofibrous membrane as low-temperature regenerative desiccant with improved stability

NASA Astrophysics Data System (ADS)

Jiang, Fengjing; Dai, Li; Yao, Ye

2018-05-01

Polyamide 6-LiCl (PA 6-LiCl) electrospun nanofibrous membranes (NFMs) have been successfully prepared as novel solid desiccant materials. The PA 6 NFM with 20% LiCl mass ratio had a sorption capacity of 1.8 g g-1 at 25 °C and 95% relative humidity, which was 4 times more than that of silica gels. The desorption isobars of the NFMs indicated that over 85% of sorbed water in the NFMs can be desorbed at about 50 °C, and the low regeneration temperature made it promising as an energy-saving desiccant material. The experimental results manifested that the sorption/desorption kinetics of the NFMs better fit the pseudo-second order model. According to scanning electron microscope images and the cycle experiment, the NFMs were also found to possess notably improved stability against moisture and could be recycled with little degradation of performance, which confirmed the practicability of the new desiccant membranes.

The Structure-Property Relationship of Poly(amide-imide)/Organoclay Nanocomposites

NASA Astrophysics Data System (ADS)

Faghihi, Khalil; Soleimani, Masoumeh; Shabanian, Meisam; Abootalebi, Ashraf Sadateh

2011-06-01

Surface treated montmorillonite (MMT) was used to prepare nanocomposites with poly(amide-imide) (PAI) 5 by solution intercalation technique with various percent of organoclay (5-15 mass %). Surface modification of the MMT was performed with Cloisite 20A for ample compatibilization with the PAI matrix. The PAI 5 chains were produced through polycondensation of 4,4-diamino diphenyl sulfone 4 with N-trimellitylimido-L-alanine 3 in a medium consisting of triphenyl phosphite, N-methyl-2-pyrolidone (NMP), pyridine and calcium chloride. The PAI-Nanocomposites morphology and clay dispersion were investigated by X-ray diffraction (XRD) and Scanning electron microscopy (SEM). The effect of clay dispersion and the interaction between clay and PAI chains on the properties of PAI-Nanocomposites films were investigated by using UV-Vis spectroscopy, thermogravimetric analysis (TGA) and water uptake measurements. Thermal stability of nanocomposites increased relative to the neat polyamide with increasing organoclay content but water uptake of these materials decreased as compared to the neat polyamide indicating reduced permeability.

Quantitative measurement of carbon nanotubes released from their composites by thermal carbon analysis

NASA Astrophysics Data System (ADS)

Ogura, I.; Kotake, M.; Ata, S.; Honda, K.

2017-06-01

The release of free carbon nanotubes (CNTs) and CNTs partly embedded in matrix debris into the air may occur during mechanical and abrasion processes involving CNT composites. Since the harmful effects of CNT-matrix mixtures have not yet been fully evaluated, it is considered that any exposure to CNTs, including CNT-matrix mixtures, should be measured and controlled. Thermal carbon analysis, such as Method 5040 of the National Institute for Occupational Safety and Health, is one of the most reliable quantitative methods for measuring CNTs in the air. However, when CNTs are released together with polymer matrices, this technique may be inapplicable. In this study, we evaluated the potential for using thermal carbon analysis to determine CNTs in the presence of polymer matrices. Our results showed that thermal carbon analysis was potentially capable of determining CNTs in distinction from polyamide 12, polybutylene terephthalate, polypropylene, and polyoxymethylene. However, it was difficult to determine CNTs in the presence of polyethylene terephthalate, polycarbonate, polyetheretherketone, or polyamide 6.

Heat resistant protective hand covering

NASA Technical Reports Server (NTRS)

Tschirch, R. P.; Sidman, K. R.; Arons, I. J. (Inventor)

1984-01-01

A heat-resistant aromatic polyamide fiber is described. The outer surface of the shell is coated with a fire-resistant elastomer and liner. Generally conforming and secured to the shell and disposed inwardly of the shell, the liner is made of a felt fabric of temperature-resistant aromatic polymide fiber.

METHOD OF USING AND MANUFACTURING PLASTIC EQUIVALENT TO ORGANIC MATERIALS

DOEpatents

Shonka, F.R.; Rose, J.E.; Failla, G.

1961-10-24

Compositions of matter that have the radiation response of animal muscle tissue, bone, or air were prepared. These compositions are composed of specific proportions of three or more of the following constituents: polyethylene plastic, polyamide plastic, oil furnace black, silica, and calcium fluoride. (AEC)

A comparison of relative toxicity rankings by some small-scale laboratory tests

NASA Technical Reports Server (NTRS)

Hilado, C. J.; Cumming, H. J.

1977-01-01

Small-scale laboratory tests for fire toxicity, suitable for use in the average laboratory hood, are needed for screening and ranking materials on the basis of relative toxicity. The performance of wool, cotton, and aromatic polyamide under several test procedures is presented.

Soft container for explosive nuts

NASA Technical Reports Server (NTRS)

Glenn, D. C.; Drummond, W. E.; Miller, G.

1981-01-01

Flexible fabric fits over variety of assembly shapes to contain debris produced by detonations or safety tests. Bag material is woven multifilament polyamide or aramid. Belt loops hold bag to clamp. Ring supports explosive nut structure and detonator wires, and after nut is mounted, bag and clamp are slipped over ring and fastened.

Chlorine-resistant composite membranes with high organic rejection

DOEpatents

McCray, Scott B.; Friesen, Dwayne T.; Barss, Robert P.; Nelson, Leslie D.

1996-01-01

A method for making a chlorine-resistant composite polyamide membrane having high organic rejection, the essential step of which comprises treating a conventional composite membrane with an acyl halide. The novel membrane is especially suitable for the treatment of water containing chlorine or lower molecular weight organic compounds.

Chemical treatment makes aromatic polyamide fabric fireproof in oxygen atmosphere

NASA Technical Reports Server (NTRS)

Cardwell, R. O.; Holsten, J. R.; Rives, J. W.

1970-01-01

Organic fabric is reacted first with vapors of a phosphorus oxychloride, phosphorus oxybromide solution and then with bromine vapor, after neutralization it is flameproof in pure oxygen atmosphere. Soaking the fabric with mixture of ammonium polyphosphates increases flame resistance, but the polyphosphates are leached out during laundering.

Study of injection molded microcellular polyamide-6 nanocomposites

Treesearch

Mingjun Yuan; Lih-Sheng Turng; Shaoqin Gong; Daniel Caulfield; Chris Hunt; Rick Spindler

2004-01-01

This study aims to explore the processing benefits and property improvements of combining nanocomposites with microcellular injection molding. The microcellular nanocomposite processing was performed on an injection-molding machine equipped with a commercially available supercritical fluid (SCF) system. The molded samples produced based on the Design of Experiments (...

Heat Transfer Measurements for a Film Cooled Turbine Vane Cascade

DTIC Science & Technology

2008-05-01

were made of 0.75 in (1.91 cm) thick clear acrylic. The test vanes were made by rapid prototyping technique of a Duraform polyamide sintering material...conditions using the following definition: pVc hSt ρ = (4) We acquired pressure survey measurements under steady state conditions. Total pressure

76 FR 19767 - Agency Information Collection Activities; Submission to OMB for Review and Approval; Comment...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-08

... Activities; Submission to OMB for Review and Approval; Comment Request; NESHAP for Epoxy Resin and Non- Nylon....gov . Title: NESHAP for Epoxy Resin and Non-Nylon Polyamide Production (Renewal). ICR Numbers: EPA ICR.... Abstract: The National Emission Standards for Hazardous Air Pollutants (NESHAP) for Epoxy Resin and Non...

21 CFR 177.2450 - Polyamide-imide resins.

Code of Federal Regulations, 2010 CFR

2010-04-01

... Determination as set forth in the “Official Methods of Analysis of the Association of Official Analytical... chromatography method titled “Amide-Imide Polymer Analysis—Analysis of Monomer Content,” is incorporated by... of films of 1 mil uniform thickness after coating and heat curing at 600 °F for 15 minutes on...

21 CFR 177.2600 - Rubber articles intended for repeated use.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Rubber articles intended for repeated use. 177... sanction or approval. (3) Substances that by regulation in parts 170 through 189 of this chapter may be... omega-laurolactam and adipic acid with poly(tetramethylene ether glycol). The polyamide and polyether...

40 CFR 63.524 - Standards for wet strength resins manufacturers.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 9 2011-07-01 2011-07-01 false Standards for wet strength resins... Polyamides Production § 63.524 Standards for wet strength resins manufacturers. (a) Owners or operators of... strength resins produced; or (2) Comply with the requirements of subpart H of this part to control...

40 CFR 63.524 - Standards for wet strength resins manufacturers.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 9 2010-07-01 2010-07-01 false Standards for wet strength resins... Polyamides Production § 63.524 Standards for wet strength resins manufacturers. (a) Owners or operators of... strength resins produced; or (2) Comply with the requirements of subpart H of this part to control...

Precise Measurement of Refractive Index and Absorption Coefficient of Near Millimeter Wave and Far Infrared Materials.

DTIC Science & Technology

1987-06-01

polyethylene. The plexiglass is a polymethyl methacrylate and the acrylic is a polymethacrylate . The polyamide(nylon) is made with adipic acid and hexamethylene...are made with acrylic acid . It was not sur- prizing to see both exhibiting similar absorption characteristics atleast 30 times higher than

Applications of nanocomposites and woodfiber plastics for microcellular injection molding

Treesearch

Lih-Sheng Turng; Mingjun Yuan; Hrishikesh Kharbas; Herman Winata; Daniel F. Caulfield

2003-01-01

The paper reviews the processing advantages and challenges of microcellular injection molding and presents recent research results on applications of nanocomposites and woodfiber-plastic composites as well as new process develop for the microcellular injection molding process. In particular, two types of polyamide (PA-6) neat resins and their filled counterparts, such...

Optical, thermal and combustion properties of self-colored polyamide nanocomposites reinforced with azo dye surface modified ZnO nanoparticles

NASA Astrophysics Data System (ADS)

Hajibeygi, Mohsen; Shabanian, Meisam; Omidi-Ghallemohamadi, Mehrdad; Khonakdar, Hossein Ali

2017-09-01

New self-colored aromatic-polyamide (PA) nanocomposites containing azo and naphthalene chromophores were prepared with azo-dye surface-modified ZnO nanoparticles (SMZnO) using solution method in dimethylformamide. The X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) results showed the uniform distribution for ZnO nanoparticles in the PA matrix. The UV-vis spectra of PA/ZnO nanocomposites (PANC) showed a blue shift as well as reduction in absorbance intensities and the photoluminescence studies revealed that the increasing intensities of the violet emission in SMZnO loading. From thermo gravimetric analysis (TGA), the temperature at 10% mass loss (T10) increased from 291.8 °C to 387.6 °C for PANC containing 8 mass% of SMZnO, as well as the char yield enhanced significantly, which was about 23.5% higher than the neat PA. The peak heat release rate resulted from microscale combustion calorimeter (MCC), by 8 mass% loading of SMZnO, decreased about 56.9% lower than the neat PA.

New polyvinyl chloride (PVC) nanocomposite consisting of aromatic polyamide and chitosan modified ZnO nanoparticles with enhanced thermal stability, low heat release rate and improved mechanical properties

NASA Astrophysics Data System (ADS)

Hajibeygi, Mohsen; Maleki, Mahdiye; Shabanian, Meisam; Ducos, Franck; Vahabi, Henri

2018-05-01

New ternary nanocomposite systems containing polylvinyl chloride (PVC), chitosan modified ZnO (CMZN) nanoparticles and new synthesized polyamide (PA) were designed and prepared by solution casting method. As a potential reinforcement, CMZN was used in PVC system combined with and without PA. Morphology, mechanical, thermal and combustion properties of the all PVC systems were studied. In the presence of the CMZN, PA showed a synergistic effect on improvement of the all investigated properties of PVC. The 5 mass% loss temperature (T5) was increased from 195 °C to 243 °C in PVC/CMZN-PA nanocomposite containing 1 mass% of each PA and CMZN (PZP 2). The peak of heat release rate was decreased from 131 W/g for PVC to 104 W/g for PVC/CMZN-PA nanocomposite containing 3 mass% of each PA and CMZN (PZP 6). According to the tensile tests, compared to the neat PVC, the tensile strength was increased from 35.4 to 53.4 MPa for PZP 6.

Triclosan-immobilized polyamide thin film composite membranes with enhanced biofouling resistance

NASA Astrophysics Data System (ADS)

Park, Sang-Hee; Hwang, Seon Oh; Kim, Taek-Seung; Cho, Arah; Kwon, Soon Jin; Kim, Kyoung Taek; Park, Hee-Deung; Lee, Jung-Hyun

2018-06-01

We report on a strategy to improve biofouling resistance of a polyamide (PA) thin-film composite (TFC) reverse osmosis (RO) membrane via chemically immobilizing triclosan (TC), known as a common organic biocide, on its surface. To facilitate covalent attachment of TC on the membrane surface, TC was functionalized with amine moiety to prepare aminopropyl TC. Then, the TC-immobilized TFC (TFC-TC) membranes were fabricated through a one-step amide formation reaction between amine groups of aminopropyl TC and acyl chloride groups present on the PA membrane surface, which was confirmed by high-resolution XPS. Strong stability of the immobilized TC was also confirmed by a hydraulic washing test. Although the TFC-TC membrane showed slightly reduced separation performance compared to the pristine control, it still maintained a satisfactory RO performance level. Importantly, the TFC-TC membrane exhibited excellent antibacterial activity against both gram negative (E. coli and P. aeruginosa) and gram positive (S. aureus) bacteria along with greatly enhanced resistance to biofilm formation. Our immobilization approach offers a robust and relatively benign strategy to control biofouling of functional surfaces, films and membranes.

Investigation of the Brill transition in nylon 6,6 by Raman, THz-Raman, and two-dimensional correlation spectroscopy.

PubMed

Bertoldo Menezes, D; Reyer, A; Musso, M

2018-02-05

The Brill transition is a phase transition process in polyamides related with structural changes between the hydrogen bonds of the lateral functional groups (CO) and (NH). In this study, we have used the potential of Raman spectroscopy for exploring this phase transition in polyamide 6,6 (nylon 6,6), due to the sensitivity of this spectroscopic technique to small intermolecular changes affecting vibrational properties of relevant functional groups. During a step by step heating and cooling process of the sample we collected Raman spectra allowing us from two-dimensional Raman correlation spectroscopy to identify which spectral regions suffered the largest influence during the Brill transition, and from Terahertz Stokes and anti-Stokes Raman spectroscopy to obtain complementary information, e.g. on the temperature of the sample. This allowed us to grasp signatures of the Brill transition from peak parameters of vibrational modes associated with (CC) skeletal stretches and (CNH) bending, and to verify the Brill transition temperature at around 160°C, as well as the reversibility of this phase transition. Copyright © 2017 Elsevier B.V. All rights reserved.

Composite Properties of Polyimide Resins Made From "Salt-Like" Solution Precursors

NASA Technical Reports Server (NTRS)

Cano, Roberto J.; Weiser, Erik S.; SaintClair, Terry L.; Echigo, Yoshiaki; Kaneshiro, Hisayasu

1997-01-01

Recent work in high temperature materials at NASA Langley Research Center (LaRC (trademark)) have led to the development of new polyimide resin systems with very attractive properties. The majority of the work done with these resin systems has concentrated on determining engineering mechanical properties of composites prepared from a poly(amide acid) precursor. Three NASA Langley-developed polyimide matrix resins, LaRC (trademark) -IA, LaRC (trademark) -IAX, and LaRC (trademark) -8515, were produced via a salt-like process developed by Unitika Ltd. The 'salt-like' solutions (sixty-five percent solids in NMP) were prepregged onto Hexcel IM7 carbon fiber using the NASA LaRC Multipurpose Tape Machine. Process parameters were determined and composite panels fabricated. Mechanical properties are presented for these three intermediate modulus carbon fiber/polyimide matrix composites and compared to existing data on the same polyimide resin systems and IM7 carbon fiber manufactured via poly(amide acid) solutions (thirty-five percent solids in NMP). This work studies the effects of varying the synthetic route on the processing and mechanical properties of polyimide composites.

FTIR and molecular mechanics studies of H-bonds in aliphatic polyurethane and polyamide-66 model molecules.

PubMed

Wang, Guoqing; Zhang, Chunxia; Guo, Xiaohe; Ren, Zhiyong

2008-02-01

Model aliphatic polyurethane (APU) hard segment based on 1,6-hexamethylene diisocyanate (HDI) and 1,4-butanediol (BDO) were prepared. FTIR and molecular mechanics (MM) simulation were used to conduct the systematic studies on APU and polyamide-66 (PA-66) whose sole difference lies in the alkoxyl oxygen. It was found that the introduction of the alkoxyl not only increases the conformations in APU, makes it a possible H-bond acceptor, but also weakens the H-bond between NH and O=C in APU. There are two conformers stably existed in APU with lowest energy, leading to eight H-bond complexes based on NH as donor and (1) O=C as acceptor, and another two complexes based on (2) alkoxyl O and (3) urethane N as acceptors, whereas there is only one stable conformer in PA-66, leading to one H-bond complex. One predominant H-bond complex has been found in APU with probability of about 95%. The simulated results are consistent with the nuNH and nuC=O band shifting in FTIR.

FTIR and molecular mechanics studies of H-bonds in aliphatic polyurethane and polyamide-66 model molecules

NASA Astrophysics Data System (ADS)

Wang, Guoqing; Zhang, Chunxia; Guo, Xiaohe; Ren, Zhiyong

2008-02-01

Model aliphatic polyurethane (APU) hard segment based on 1,6-hexamethylene diisocyanate (HDI) and 1,4-butanediol (BDO) were prepared. FTIR and molecular mechanics (MM) simulation were used to conduct the systematic studies on APU and polyamide-66 (PA-66) whose sole difference lies in the alkoxyl oxygen. It was found that the introduction of the alkoxyl not only increases the conformations in APU, makes it a possible H-bond acceptor, but also weakens the H-bond between NH and O dbnd C in APU. There are two conformers stably existed in APU with lowest energy, leading to eight H-bond complexes based on NH as donor and (1) O dbnd C as acceptor, and another two complexes based on (2) alkoxyl O and (3) urethane N as acceptors, whereas there is only one stable conformer in PA-66, leading to one H-bond complex. One predominant H-bond complex has been found in APU with probability of about 95%. The simulated results are consistent with the νNH and νC dbnd O band shifting in FTIR.

G-Quadruplex Induction by the Hairpin Pyrrole-Imidazole Polyamide Dimer.

PubMed

Obata, Shunsuke; Asamitsu, Sefan; Hashiya, Kaori; Bando, Toshikazu; Sugiyama, Hiroshi

2018-02-06

The G-quadruplex (G4) is one type of higher-order structure of nucleic acids and is thought to play important roles in various biological events such as regulation of transcription and inhibition of DNA replication. Pyrrole-imidazole polyamides (PIPs) are programmable small molecules that can sequence-specifically bind with high affinity to the minor groove of double-stranded DNA (dsDNA). Herein, we designed head-to-head hairpin PIP dimers and their target dsDNA in a model G4-forming sequence. Using an electrophoresis mobility shift assay and transcription arrest assay, we found that PIP dimers could induce the structural change to G4 DNA from dsDNA through the recognition by one PIP dimer molecule of two duplex-binding sites flanking both ends of the G4-forming sequence. This induction ability was dependent on linker length. This is the first study to induce G4 formation using PIPs, which are known to be dsDNA binders. The results reported here suggest that selective G4 induction in native sequences may be achieved with PIP dimers by applying the same design strategy.

Generation of conductivity through transfer charge properties, for polyesters and polyamides with characteristic functional groups

NASA Astrophysics Data System (ADS)

Gonzalez, Carmen; Tagle, Luis Hernan; Terraza, Claudio A.; Barriga, Andres; Cabrera, A. L.; Volkmann, Ulrich G.

2011-03-01

Electro-optic properties of σ -conjugated polymers, as polysilylene; are associated with electron conjugation in the silicon atom, which allows a significant delocalization of electrons along of the chain. Thus, the conductivity is intimately connected to the mobility of charge carriers, which in turn depends on the structure and morphology of the system. We report the characterization of polyesters (PEFs) and polyamides (PAFs). Film thicknesses were obtained by ellipsometry. The vibration frequencies of the groups were determined by FT-IR and corroborated by Raman spectroscopy. Structural information was obtained from X-Ray diffraction (XRD). The structural and surface morphology were studied by scanning electron microscope (SEM). Electrical conductivity of the polymers was measured before and after exposure to iodine vapor, for films of different thicknesses. Morphological differentiation was studied by energy dispersive microscopy (EDX), showing a regular distribution of iodine within the polymer. Preliminary conductivity measurements showed adverse effects when oxidation of the polymer films is induced These effects are related to a certain grade of disorder within the system

Influence of electron beam irradiation on mechanical and thermal properties of polypropylene/polyamide blend

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

Nakamura, Shigeya, E-mail: shi-nakamura@hitachi-chem.co.jp; Tokumitsu, Katsuhisa

The effects of electron beam irradiation on the mechanical and thermal properties of polypropylene (PP) and polyamide6 (PA6) blends-with talc 20 wt% as filler, SEBS-g-MAH as compatibilizer, and triallyl isocyanurate as crosslinking agent-were investigated. Although the tensile and flexural moduli and strengths of the PP/PA6 blends with talc, SEBS-g-MAH, and TAIC could be increased by the application of electron beam irradiation, the impact strength was decreased. Ddifferential scanning calorimetryer measurements showed that the melting temperatures of all PP/PA6 blends were decreased with increases in the electron beam irradiationdose. From dynamic mechanical analyzer results, a storage modulus curve in the plateaumore » region was observed only in the PP/PA6 blends with talc, SEBS-g-MAH, and TAIC; the storage modulus increased with increasing electron beam irradiation dose, indicating that the three-dimensional network developed gradually in the more amorphous PA6. As a result, the most significant improvement observed in heat distortion tests under high load (1.8 MPa) occurred at 200 kGy.« less

Effect of Silane Coupling Agent on Tribological Properties of Hemp Fiber-Reinforced Plant-Derived Polyamide 1010 Biomass Composites

PubMed Central

Kajiyama, Tetsuto; Yamanaka, Toshiyuki

2017-01-01

We have studied the effects of silane coupling agents used for the surface treatment of fiber on the tribological properties of hemp fiber (HF) reinforced plant-derived polyamide 1010 (PA1010) biomass composites. Hemp fibers were surface-treated by two surface treatment methods: (a) alkali treatment by sodium hydroxide solution and (b) surface treatment by silane coupling agents. Three types of silane coupling agents, namely aminosilane, epoxysilane and ureidosilane were used. These HF/PA1010 biomass composites were extruded using a twin extruder, and injection-molded. The mechanical and tribological properties were evaluated by the ring-on-plate type sliding wear test. It was found that tribological properties of HF/PA1010 biomass composites improved with the surface treatment by the silane coupling agent. This may be attributed to the change in the mode of friction and wear mechanism by the interfacial adhesion between fiber and matrix polymer according to the type of silane coupling agent used. In particular, the ureidosilane coupling agent showed the best improvement effect for the tribological properties of these biomass composites in this study. PMID:28872624

Semicrystalline polyamide engineering thermoplastics based on the renewable monomer, 1,9-nonane diamine: Thermal properties and water absorption

DOE PAGES

Kugel, Alex; He, Jie; Samanta, Satyabrata; ...

2012-08-27

Here, a series of poly(1,9-nonamethylene adipamide-co-1,9-nonamethylene terephthalamide) copolymers were produced using melt polymerization and the thermal properties, crystal structure, and moisture uptake characterized. The results confirmed that the copolymers exhibit isomorphism. As expected, glass transition temperature and the apparent melting temperature increased with increasing terephthalmide content. Using the difference in the apparent melting temperature to the crystallization temperature as a measure of relative crystallization rate, it was observed that crystallization rate decreased as the terephthalamide content of the copolymer was increased from 0 to 50 mole percent but then sharply increased when increased beyond 50 mole percent. This behavior maymore » be the result of extensive inter- and intramolecular interactions in the melt associated with terephthalmide units in the polymer chain that nucleate crystallization upon cooling below the equilibrium melting temperature. Comparing the thermal properties of copolymers possessing an excess of terephthalmide units to the commodity polyamide Nylon 6,6, it is believed that these copolymers may have utility as partially renewable engineering thermoplastics.« less

Compositional and functional dynamics of dried papaya as affected by storage time and packaging material.

PubMed

Udomkun, Patchimaporn; Nagle, Marcus; Argyropoulos, Dimitrios; Mahayothee, Busarakorn; Latif, Sajid; Müller, Joachim

2016-04-01

Papaya has been identified as a valuable source of nutrients and antioxidants, which are beneficial for human health. To preserve the nutritional properties after drying, appropriate storage specifications should be considered. This study aimed to investigate the quality and stability of air-dried papaya in terms of quality dynamics and behavior of bio-active compounds during storage for up to 9 months in two packaging materials: aluminum laminated polyethylene and polyamide/polyethylene. Samples with moisture content (MC) of 0.1328 g g(-1) and water activity (aw) of 0.5 were stored at 30 °C and relative humidity (RH) of 40-50%. The MC, aw, degree of browning (DB) and 5-hydroxymethylfurfural (HMF) content were found to notably increase as storage progressed. On the contrary, there was a significant decrease in antioxidant capacity (DPPH, FRAP and ABTS), total phenolic (TP) and ascorbic acid (AA) contents. Packaging in aluminum laminated polyethylene under ambient conditions was found to better preserve bio-active compounds and retard increases in MC, aw and DB, when compared to polyamide/polyethylene. Copyright © 2015 Elsevier Ltd. All rights reserved.

Chlorine-Resistant Polyamide Reverse Osmosis Membrane with Monitorable and Regenerative Sacrificial Layers.

PubMed

Huang, Hai; Lin, Saisai; Zhang, Lin; Hou, Li'an

2017-03-22

Improving chlorine stability is a high priority for aromatic polyamide (PA) reverse osmosis (RO) membranes especially in long-term desalination. In this Research Article, PA RO membranes of sustainable chlorine resistance was synthesized. Glycylglycine (Gly) was grafted onto the membrane surface as a regenerative chlorine sacrificial layer, and the zeta-potential was used to monitor the membrane performance and to conduct timely regeneration operations for chlorinated Gly. The Gly-grafted PA membrane exhibited ameliorative chlorine resistance in which the N-H moiety of glycylglycine served as sacrificial pendants against chlorine attacks. Cyclic chlorination experiments, combined with FT-IR and XPS analysis, were carried out to characterize the membrane. Results indicated that the resulting N-halamines could be fast regenerated by a simple alkaline reduction step (pH 10). A synchronous relationship between the zeta-potential and the chlorination extent of the sacrificial layer was observed. This indicated that the zeta-potential can be used as an on-site sensor to conduct a timely regeneration operation. The intrinsic mechanism of the surface sacrificial process was also studied.

Polyamide 6/chitosan nanofibers as support for the immobilization of Trametes versicolor laccase for the elimination of endocrine disrupting chemicals.

PubMed

Maryšková, Milena; Ardao, Inés; García-González, Carlos A; Martinová, Lenka; Rotková, Jana; Ševců, Alena

2016-07-01

In recent years, there has been an increase in efforts to improve wastewater treatment as the concentration of dangerous pollutants, such as endocrine disrupting chemicals, in wastewater increases. These compounds, which mimic the effect of hormones, have a negative impact on human health and are not easily removed from water. One way to effectively eliminate these pollutants is to use enzymatically activated materials. In this study, we report on the use of laccase from the white rot fungus Trametes versicolor immobilized onto polyamide 6/chitosan (PA6/CHIT) nanofibers modified using two different spacers (bovine serum albumin and hexamethylenediamine). We then tested the ability of the PA6/CHIT-laccase biocatalysts to eliminate a mixture containing 50μM of two endocrine disrupting chemicals: bisphenol A and 17α-ethinylestradiol. The PA6/CHIT nanofiber matrix used in this study not only proved to be a suitable carrier for immobilized and modified laccase but was also efficient in the removal of a mixture of endocrine disrupting chemicals in three treatment cycles. Copyright © 2016 Elsevier Inc. All rights reserved.

Effect of modification of isotactic polypropylene by additives of polyamide 6/66 on structural characteristics of composites

NASA Astrophysics Data System (ADS)

Vorontsov, N. V.; Popov, A. A.; Margolin, A. L.

2017-12-01

Changes in the supramolecular structure of polymer composites based on isotactic polypropylene (PP) and polyamide 6/66 (PA) are studied depending on the PP : PA ratio. Temperatures and enthalpies of melting and crystallization of both PP and PA and their composites are determined depending on the composition of the mixtures. It was shown that the initial melting point of a composite does not change with increasing PA content in the blends. The crystallization temperature of the mixtures is shown to increase with the addition of PA and becomes much higher than the crystallization temperatures of both PP and PA. The observed effect can be due to a strong interaction between the PP and PA molecules, thus decreasing the molecular mobility and increasing the crystallization temperature. The crystallization and melting of PP-PA mixtures are found to proceed at the close temperatures, although the crystallization and melting temperatures of pure PP and pure PA differ widely. The melting and crystallization enthalpies decrease with increasing PA concentration in the mixtures, which indicates a decrease in the degree of crystallinity of the composite.

Thin-Film Nanocomposite Membrane with the Minimum Amount of MOF by the Langmuir-Schaefer Technique for Nanofiltration.

PubMed

Navarro, Marta; Benito, Javier; Paseta, Lorena; Gascón, Ignacio; Coronas, Joaquín; Téllez, Carlos

2018-01-10

An innovative procedure for positioning a monolayer of hydrophilic metal organic framework (MOF) MIL-101(Cr) (MIL, Materials of Institute Lavoisier) nanoparticles (NPs) in thin-film nanocomposite (TFN) membranes has been implemented by transferring a Langmuir-Schaefer (LS) film of the MOF in between the polyamide thin layer at the top and the cross-linked asymmetric polyimide (P84) support at the bottom. The presence and layout of the LS-MIL-101(Cr) monolayer in the TFN membrane was confirmed by scanning transmission electron microscopy imaging with a high-angle annular dark-field detector images and X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, electron energy loss spectroscopy, and atomic force microscopy analyses. This methodology requires the smallest amount of MOF reported to date, 3.8 μg cm -2 , and promotes the formation of a defect-free ultrathin MOF film. Although conventional TFN membranes tend to show MOF agglomerates that could contribute to the formation of unselective defects, LS-TFN membranes, characterized by a homogeneous and continuous MOF coating, exhibit an optimal membrane performance, without a significant decrease in selectivity. Outstanding methanol permeances, one of the best results reported to date, of 10.1 ± 0.5 L m -2 h -1 bar -1 when filtering sunset yellow and of 9.5 ± 2.1 L m -2 h -1 bar -1 when filtering rose bengal have been achieved in LS-TFN membranes with a rejection higher than 90% in all cases. Methanol permeates through the polyamide and the LS-MIL-101(Cr) monolayer, greatly enhanced by the MOF pore system, in comparison to thin-film composite and conventional TFN membranes (7.5 ± 0.7 and 7.7 ± 1.1 L m -2 h -1 bar -1 when filtering sunset yellow), respectively, in which polyamide areas free of MOF NPs are present.

Polyamide/titania hollow nanofibers prepared by core-shell electrospinning as a microextractive phase in a fabricated sandwiched format microfluidic device.

PubMed

Rezvani, Omid; Hedeshi, Mahin Hashemi; Bagheri, Habib

2017-12-15

In this study, a low-cost microfluidic device from polymethyl methacrylate was fabricated by laser engraving technique. The device is consisted of a central chip unit with an aligned microchannel. Both sides of the engraved microchannel were sandwiched by two synthesized sheets from polyamide/titania (PA/TiO 2 ) hollow nanofibers as extractive phases. The inlet and outlet of the device were connected to the polyether ether ketone tubes, while a peristaltic pump was used to deliver both sample and desorbing solvent through the microchannel. The recorded scanning electron microscopy images from the surface of the synthesized PA/TiO 2 nanofibers, exhibit a good degree of homogeneity and porosity throughout their structures. Also, the presence of titanium was indicated by the energy dispersive X-ray analysis, while the recorded Fourier transform infrared spectra confirmed their chemical structures. The addition of titania in the composition of polyamide nanofibers, not only improved the mechanical stability of the extractive phase but also enhanced its extraction capability. The major parameters associated with the extraction performance were studied and eventually the method was validated by the use of a gas chromatography-mass spectrometry. The limits of detection for the selected triazines were between 0.01 and 0.03ngmL -1 , while the limits of quantification ranged from 0.04 to 0.1ngmL -1 . In addition, the interday and intraday reproducibility (RSD%) were lower than 6.6% (n=3). The calibration graph for atrazine was linear in the range of 0.2-50ngmL -1 while two linear ranges for ametryn and terbutryn (0.1-10 and 20-500ngmL -1 ) were achieved. Relative recoveries were between 89 and 98% with the regression coefficient range of 0.9969-0.9991. Copyright © 2017 Elsevier B.V. All rights reserved.

Culture of human anulus fibrosus cells on polyamide nanofibers: extracellular matrix production.

PubMed

Gruber, Helen E; Hoelscher, Gretchen; Ingram, Jane A; Hanley, Edward N

2009-01-01

Studies were approved by the authors' Human Subjects Institutional Review Board. Human anulus cells were tested for growth and extracellular matrix (ECM) production in vitro. To investigate cell attachment, cell proliferation, and ECM production of human intervertebral disc anulus cells seeded onto randomly oriented electrospun polyamide nanofibers. Because nanofibrillar matrices have the potential to promote microenvironments, which may mimic in vivo conditions and resemble connective tissue, their utilization opens new avenues for cell-based tissue engineering applications for disc cells. Anulus cells were isolated from 4 cervical spine surgical disc specimens, expanded, and seeded into either routine plastic culture (control) or a nanofiber surface of randomly oriented electrospun polyamide nanofibers (Ultra-Web-coated culture dish, Corning) with a positive charge or without a charge. Cells were cultured for 9 days, digital images captured, cells harvested, embedded in paraffin, and examined for production of extracellular matrix (ECM). Additional anulus cultures were tested to quantitatively assess total proteoglycan production and cell proliferation under control or nanofiber cultures. Cells attached well and exhibited cell extensions within the nanofiber layers; cells on the charged nanofiber surface deposited greater amounts of chondroitin sulfate than of type II collagen than cells cultured on the uncharged nanofiber surface. Results showed that culture of anulus cells on nanofibers was permissive for secretion and assembly of type II collagen and chondroitin sulfate. Significantly greater total proteoglycan formation was present after culture on the nanofiber with added charge conditions {control, 0.6116 microg/mL +/- 0.186 [4] [mean +/- sem(n)] vs. 1.201 +/- 0.2509 [4], P < 0.05}. Cell proliferation, however, did not differ among treatment groups. Culture of anulus cells on nanofibers was found to be permissive for secretion and assembly of type II collagen and chondroitin sulfate, and culture on nanofibers with added charge significantly increased total proteoglycan production. These novel findings point to the need for further examination of nanofibrillar 3D culture of anulus cells for tissue engineering applications.

40 CFR Table 1 to Subpart W of... - General Provisions Applicability to Subpart W

Code of Federal Regulations, 2010 CFR

2010-07-01

... Subpart W 1 Table 1 to Subpart W of Part 63 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Polyamides Production Pt. 63, Subpt. W, Table 1 Table 1 to Subpart W of Part 63—General Provisions Applicability to Subpart W Reference Applies to subpart W BLR WSR WSR alternative standard, and BLR equipment...

Regulatory assessment with regulatory flexibility analysis and paperwork reduction act analysis : draft regulatory evaluation : Notice of Proposed Rulemaking -- Pipeline Safety : Polyamide-11 (PA-11) plastic pipe design pressures

DOT National Transportation Integrated Search

2007-06-01

The Pipeline and Hazardous Materials Safety Administration (PHMSA) is proposing changes to the Federal pipeline safety regulations in 49 CFR Part 192, which cover the transportation of natural gas by pipeline. Specifically, PHMSA is proposing to chan...

Speedy Acquisition of Surface-Contamination Samples

NASA Technical Reports Server (NTRS)

Puleo, J. R.; Kirschner, L. E.

1982-01-01

Biological contamination of large-area surfaces can be determined quickly, inexpensively, and accurately with the aid of a polyester bonded cloth. Cloth is highly effective in removing microbes from a surface and releasing them for biological assay. In releasing contaminants, polyester bonded cloth was found to be superior to other commercial cleanroom cloths, including spun-bound polyamid cloths and cellulose cloths.

Military Handbook: General Guidelines for Electronic Equipment

DTIC Science & Technology

1995-04-28

Epoxy- resin PoLyricinoteates Lubricants Polyvinyl chloride Metamine- formaldehyde Polyvinyl chloride-acetate Organic potysuLphides Potyvinyt fluoride...Phenol- formaldehyde Rubbers, natural and synthetic Polydichlorostyrene Urea - formaldehyde 1/Literature shows that under certain conditions polyamides may...Electrical, Synthetic- Resin Composition, Non-Rigid MIL-T-713 Twine, Fibrous: Impregnated , Lacing and Tying MIL-I-3158 Insulation Tape, Electrical Glass

Diamines and polyimides containing pendent ethynyl groups

NASA Technical Reports Server (NTRS)

Hergenrother, Paul M. (Inventor); Jensen, Brian J. (Inventor)

1994-01-01

Diamines containing pendent ethynyl and substituted ethynyl groups are synthesized. These diamines are reacted with dianhydrides to form polyamide acids, which are chemically or thermally cyclodehydrated to form polyimides and copolyimides with pendent ethynyl groups. Upon heating, the pendent ethynyl groups react to form crosslinked resins that are useful as adhesives, composite matrices, coatings, moldings, and films.

High-Performance Synthetic Fibers for Composites

DTIC Science & Technology

1992-04-01

under evaluation today include polyether ether ketone , polyamide, 23 polyamideimide, polyimide, polysulfone, and polyphenylene sulfide. Epoxy resins...shrinkage under intense neutron radiation . This attribute, together with other properties of high-temperature strength, toughness, and low nuclear...and (2) liquid or solid resins cross-linked with other esters in chopped-fiber and mineral-filled molding compounds. Polyether ether ketone (PEEK) A

Robust Membranes for Sustainable Wastewater Treatment by Forward Osmosis in FOBs

DTIC Science & Technology

2017-05-09

the Department of Defense Strategic Environmental Research and Development Program (SERDP). The publication of this report does not indicate...CT 06511 9. SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S) Strategic Environmental Research and...strategies, in-situ fabrication and post -fabrication membrane modification. In-situ fabrication modification involves fabrication of a polyamide selective

Development of a Meso-Scale Material Model for Ballistic Fabric and Its Use in Flexible-Armor Protection Systems

DTIC Science & Technology

2010-02-01

s mobility. Early materials used included leather , silk, metal chain mail, and metal plates. Replacement of metal with a nylon (poly-amide) fabric...tests of flexible-fabric armor, and as shown by Tan et al. (Ref 24) in a series of postimpact fabric-inspection studies, play an important role in

Novel Particulate Air-Filtration Media: Market Survey

DTIC Science & Technology

2013-02-01

efficiencies up to 99.999% (0.001% penetration) using two solid-state laser photometers to measure aerosol concentration levels up and downstream of...MN) Tetratex, Ultra-Web, Spider-Web, Dura-Life, Fiber-Web, and Syntek XP DuPont (Wilmington, DE) Spunbond Polypropylene , Nomex KD, and Hybrid...nanofiber technology. The meltblown textiles can be manufactured using polypropylene , polyamides, polylactic acid and biodegradable polymers

Low temperature processing of ultra-pure cellulose fibers into nylon 6 and other thermoplastics

Treesearch

Rod Jacobson; Dan Caulfield; Karl Sears; John Underwood

2002-01-01

The objective of this research was to develop a stable process for compound ultra-pure cellulose fibers into polyamides. This has been a difficult procedure and has taken years of trial and error to understand the viscosity shear heating effects associated with compounding cellulose into high-melting point engineering thermoplastics. The evolution of the low...

Isolation and quantification of oligomeric pyranoanthocyanin-flavanol pigments from red wines by combination of column chromatographic techniques.

PubMed

He, Jingren; Santos-Buelga, Celestino; Mateus, Nuno; de Freitas, Victor

2006-11-17

A combination of column chromatography on Toyopearl gel HW-40 (S) and polyamide resin has been developed for the preparative isolation and further determination of pyranoanthocyanins of oligomeric nature formed after reaction between anthocyanins and different flavanols in a complex wine matrix. Polyamide chromatography was found to be exceptionally useful to separate oligomeric pyanoanthocyanins from other classes of wine flavonoids and polymerized pigments into an advanced state of purity for further identification and quantification by HPLC-diode array detector coupled with electrospray ionization mass spectrometry (HPLC-DAD/ESI-MS). Fractionation on Toyopearl gel chromatography allowed the separation of pyranoanthocyanins bearing the same flavanols (catechin, epicatechin and procyanidin dimers) but with different anthocyanin moieties (either acylated or non-acylated in the glucose residue) in order to allow further isolation of individual oligomeric pigments on C18 chromatography. A quantitative procedure for analyzing the major pyranoanthocyanin-flavanol derivatives in different aged wines is proposed for the first time. Results obtained showed good reproducibility and recovery regarding sample pretreatment and quantitative method for all analyzed oligomeric pyranoanthocyanins. The combination of these two chromatographic separations is likely to be applicable to the preparative isolation of other anthocyanin-derived pigments.

Hybrid joining of polyamide and hydrogenated acrylonitrile butadiene rubber through heat-resistant functional layer of silane coupling agent

NASA Astrophysics Data System (ADS)

Sang, Jing; Sato, Riku; Aisawa, Sumio; Hirahara, Hidetoshi; Mori, Kunio

2017-08-01

A simple, direct adhesion method was developed to join polyamide (PA6) to hydrogenated acrylonitrile butadiene rubber (HNBR) by grafting a functional layer of a silane coupling agent on plasma functionalized PA6 surfaces. The functional layer of the silane coupling agent was prepared using a self-assembly method, which greatly improved the heat resistance of PA6 from 153 °C up to 325 °C and the resulting PA6/HNBR joints showed excellent adhesion properties with cohesive failure between PA6 and HNBR. X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and nanoscale infrared microscopy and chemical imaging (Nano-IR, AFM-IR) were employed to characterize the surfaces and interfaces. The Nano-IR analysis method was employed for the first time to analyze the chemical structures of the adhesion interfaces between different materials and to establish the interface formation mechanism. This study is of significant value for interface research and the study of adhesion between resins and rubbers. There is a promising future for heat-resistant functional layers on resin surfaces, with potential application in fuel hose composite materials for the automotive and aeronautical industries.

Polymer powders for selective laser sintering (SLS)

NASA Astrophysics Data System (ADS)

Schmid, Manfred; Amado, Antonio; Wegener, Konrad

2015-05-01

Selective Laser Sintering (SLS) is close to be accepted as a production technique (Additive Manufacturing). However, one problem limiting employment of SLS for additive manufacturing in a wide-ranging industrial scope is the narrow variety of applicable polymers. The commonly applied SLS powder to date is polyamide 12 (PA 12). PA 12 or ccompounds of PA 12 (dry blends) are approximately 90 % of complete industrial consumption. The remaining small quantity is distributed on polyamide 11 (PA11) and some other `exotic' polymers (TPU, PEBA, P(E)EK). Industry is awaiting commodity polymers like polypropylene (PP) or polyethylene (PE) crucial to open new market segments. But several approaches launching those polymers failed. But what are the reasons for the difficulties in developing new SLS powders? The contribution is to answer this and highlights the combination of intrinsic and extrinsic polymer properties necessary to generate a polymer powder promising for SLS application. Particle shape, powder distribution, thermal, rheological and optical requirements must be considered and only a particularly controlled property combination leads to successful SLS implementation. Thermal behavior, particle shape and -distribution is discussed in detail, although the other properties can't be disregarded for providing new commercially successful SLS powder finally.

Fluorescent detection of C-reactive protein using polyamide beads

NASA Astrophysics Data System (ADS)

Jagadeesh, Shreesha; Chen, Lu; Aitchison, Stewart

2016-03-01

Bacterial infection causes Sepsis which is one of the leading cause of mortality in hospitals. This infection can be quantified from blood plasma using C - reactive protein (CRP). A quick diagnosis at the patient's location through Point-of- Care (POC) testing could give doctors the confidence to prescribe antibiotics. In this paper, the development and testing of a bead-based procedure for CRP quantification is described. The size of the beads enable them to be trapped in wells without the need for magnetic methods of immobilization. Large (1.5 mm diameter) Polyamide nylon beads were used as the substrate for capturing CRP from pure analyte samples. The beads captured CRP either directly through adsorption or indirectly by having specific capture antibodies on their surface. Both methods used fluorescent imaging techniques to quantify the protein. The amount of CRP needed to give a sufficient fluorescent signal through direct capture method was found suitable for identifying bacterial causes of infection. Similarly, viral infections could be quantified by the more sensitive indirect capture method. This bead-based assay can be potentially integrated as a disposable cartridge in a POC device due to its passive nature and the small quantities needed.

A review on polyamide thin film nanocomposite (TFN) membranes: History, applications, challenges and approaches.

PubMed

Lau, W J; Gray, Stephen; Matsuura, T; Emadzadeh, D; Chen, J Paul; Ismail, A F

2015-09-01

This review focuses on the development of polyamide (PA) thin film nanocomposite (TFN) membranes for various aqueous media-based separation processes such as nanofiltration, reverse osmosis and forward osmosis since the concept of TFN was introduced in year 2007. Although the total number of published TFN articles falls far short of the articles of the well-known thin film composite (TFC) membranes, its growth rate is significant, particularly since 2012. Generally, by incorporating an appropriate amount of nanofiller into a thin selective PA layer of a composite membrane, one could produce TFN membranes with enhanced separation characteristics as compared to the conventional TFC membrane. For certain cases, the resulting TFN membranes demonstrate not only excellent antifouling resistance and/or greater antibacterial effect, but also possibly overcome the trade-off effect between water permeability and solute selectivity. Furthermore, this review attempts to give the readers insights into the difficulties of incorporating inorganic nanomaterials into the organic PA layer whose thickness usually falls in a range of several-hundred nanometers. It is also intended to show new possible approaches to overcome these challenges in TFN membrane fabrication. Copyright © 2015 Elsevier Ltd. All rights reserved.

Interactions of Organics within Hydrated Selective Layer of Reverse Osmosis Desalination Membrane: A Combined Experimental and Computational Study.

PubMed

Ghoufi, Aziz; Dražević, Emil; Szymczyk, Anthony

2017-03-07

In this work we have examined a computational approach in predicting the interactions between uncharged organic solutes and polyamide membranes. We used three model organic molecules with identical molecular weights (100.1 g/mol), 4-aminopiperidine, 3,3-dimethyl-2-butanone (pinacolone) and methylisobutyl ketone for which we obtained experimental data on partitioning, diffusion and separation on a typical seawater reverse osmosis (RO) membrane. The interaction energy between the solutes and the membrane phase (fully aromatic polyamide) was computed from molecular dynamics (MD) simulations and the resulting sequence was found to correlate well with the experimental rejections and sorption data. Sorption of the different organic solutes within the membrane skin layer determined from attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) nicely agreed with interaction energies computed from molecular simulations. Qualitative information about solute diffusivity inside the membrane was also extracted from MD simulations while ATR-FTIR experiments indicated strongly hindered diffusion with diffusion coefficients in the membrane about 10 -15 m 2 /s. The computational approach presented here could be a first step toward predicting rejections trends of, for example, hormones and pharmaceuticals by RO dense membranes.

Comparison of mechanical properties for polyamide 12 composite-based biomaterials fabricated by fused filament fabrication and injection molding

NASA Astrophysics Data System (ADS)

Rahim, Tuan Noraihan Azila Tuan; Abdullah, Abdul Manaf; Akil, Hazizan Md; Mohamad, Dasmawati

2016-12-01

The emergence of 3D printing technology known as fused filament fabrication (FFF) has offered the possibility of producing an anatomically accurate, patient specific implant with more affordable prices. The only weakness of this technology is related to incompatibility and lack of properties of current material to be applied in biomedical. Therefore, this study aims to develop a new, polymer composite-based biomaterial that exhibits a high processability using FFF technique, strong enough and shows acceptable biocompatibility, and safe for biomedical use. Polyamide 12 (PA12), which meets all these requirements was incorporated with two bioceramic fillers, zirconia and hydroxyapatite in order to improve the mechanical and bioactivity properties. The obtained mechanical properties were compared with injection-molded specimens and also a commercial biomedical product, HAPEXTM which is composed of hydroxyapatite and polyethylene. The yield strength and modulus of the PA12 composites increased steadily with increasing filler loading. Although the strength of printed PA12 composites were reduced compared with injection molded specimen, but still higher than HAPEXTM material. The higher surface roughness obtained by printed PA12 was expected to enhance the cell adhesion and provide better implant fixation.

Investigating the Moisture Content of Polyamide 6 by Raman-Microscopy and Multivariate Data Analysis

NASA Astrophysics Data System (ADS)

Lechner, Tobias; Noack, Kristina; Thöne, Manuel; Amend, Philipp; Schmidt, Michael; Will, Stefan

Thermal malleability of thermoplastics results in a high product diversity in various industry sectors. However, industrial applications require a constant and high component quality. Hence, material processing such as laser welding has to consider that, e.g., the moisture content of thermoplastics influences the mechanical properties such as the tensile strength. Moreover, water evaporates during laser welding and can form pores and defects. Thus, there is a large need for non-invasive material inspection before processing. To that end, we developed a methodology based on Raman-microscopy and multivariate data analysis (MVD) to determine the moisture content of polyamide (MCP). Further, the impact of the MCP on the mechanical properties was verified. For samples with a defined variation of the MCP, xyz-Raman-scans were carried out and analysed using MVD. For reference purposes, the samples were weighted and tensile tests were performed. An evaluation by means of partial least squares regression analysis (PLSR) resulted in a prediction of the MCP with a correlation coefficient >98%. Consequently, Raman-microscopy shows large potential for developing new techniques for inspection and quality control of plastics before processing. Dedicated to Professor Alfred Leipertz on the occasion of his 70th birthday.

Aggregation and Gelation of Aromatic Polyamides with Parallel and Anti-parallel Alignment of Molecular Dipole Along the Backbone

NASA Astrophysics Data System (ADS)

Zhu, Dan; Shang, Jing; Ye, Xiaodong; Shen, Jian

2016-12-01

The understanding of macromolecular structures and interactions is important but difficult, due to the facts that a macromolecules are of versatile conformations and aggregate states, which vary with environmental conditions and histories. In this work two polyamides with parallel or anti-parallel dipoles along the linear backbone, named as ABAB (parallel) and AABB (anti-parallel) have been studied. By using a combination of methods, the phase behaviors of the polymers during the aggregate and gelation, i.e., the forming or dissociation processes of nuclei and fibril, cluster of fibrils, and cluster-cluster aggregation have been revealed. Such abundant phase behaviors are dominated by the inter-chain interactions, including dispersion, polarity and hydrogen bonding, and correlatd with the solubility parameters of solvents, the temperature, and the polymer concentration. The results of X-ray diffraction and fast-mode dielectric relaxation indicate that AABB possesses more rigid conformation than ABAB, and because of that AABB aggregates are of long fibers while ABAB is of hairy fibril clusters, the gelation concentration in toluene is 1 w/v% for AABB, lower than the 3 w/v% for ABAB.

Surface Roughness Optimization of Polyamide-6/Nanoclay Nanocomposites Using Artificial Neural Network: Genetic Algorithm Approach

PubMed Central

Moghri, Mehdi; Omidi, Mostafa; Farahnakian, Masoud

2014-01-01

During the past decade, polymer nanocomposites attracted considerable investment in research and development worldwide. One of the key factors that affect the quality of polymer nanocomposite products in machining is surface roughness. To obtain high quality products and reduce machining costs it is very important to determine the optimal machining conditions so as to achieve enhanced machining performance. The objective of this paper is to develop a predictive model using a combined design of experiments and artificial intelligence approach for optimization of surface roughness in milling of polyamide-6 (PA-6) nanocomposites. A surface roughness predictive model was developed in terms of milling parameters (spindle speed and feed rate) and nanoclay (NC) content using artificial neural network (ANN). As the present study deals with relatively small number of data obtained from full factorial design, application of genetic algorithm (GA) for ANN training is thought to be an appropriate approach for the purpose of developing accurate and robust ANN model. In the optimization phase, a GA is considered in conjunction with the explicit nonlinear function derived from the ANN to determine the optimal milling parameters for minimization of surface roughness for each PA-6 nanocomposite. PMID:24578636

Tribological and Mechanical Behaviors of Polyamide 6/Glass Fiber Composite Filled with Various Solid Lubricants

PubMed Central

Li, Duxin; Xie, Ying; Li, Wenjuan; You, Yilan; Deng, Xin

2013-01-01

The effects of polytetrafluoroethylene (PTFE), graphite, ultrahigh molecular weight polyethylene (UHMWPE), and their compounds on mechanical and tribological properties of glass-fiber-reinforced polyamide 6 (PA6/GF) were studied. The polymeric materials were blended using twin-screw extruder and subsequently injection molded for test samples. Mechanical properties were investigated in terms of hardness, tensile strength, and impact strength. Friction and wear experiments were run under ambient conditions at a rotating speed of 200 rpm and load of 100 N. The morphologies of the worn surfaces were also observed with scanning electron microscope. The results showed that graphite could increase the tensile strength of PA6/GF-15 composite, but the material became soft. Graphite/UHMWPE complex solid lubricants were effective in increasing the already high impact strength of PA6/GF-15 composite. 5% PTFE gave the maximum reduction in the coefficient of friction. However, PTFE/UHMWPE complex solid lubricants were the best choice for improving both friction and wear behaviors due to the lower friction coefficient and mass wear rate. Moreover, the worn surface of PA6 composites revealed that adhesive wear, abrasive wear, and fatigue wear occurred in this study. PMID:23766687

Initial adhesive screening of novel polyamide-imides and their copolymers

NASA Technical Reports Server (NTRS)

Progar, Donald J.; Dezern, James F.

1988-01-01

Continued interest by the research community in thermally stable, tough, high temperature adhesives has resulted in the investigation by Langley Research Center of two linear aromatic polyamide-imide (PAI) homopolymers and two linear aromatic PAI copolymers. The homopolymers were made with either 3,3'=DABA or 4,4'-DABA and BTDA. The two polymers were prepared with a monomer ratio of 0.75 DABP:0.25 DABA:1.00 BTDA. These aromatic PAIs possess high thermal stability because of intermolecular hydrogen bonding and chain stiffness. Lap shear strength (LSS) was the main criteria used to evaluate the polymers as adhesives. LSS of bonded Ti-6Al-4V was determined at room temperature (RT), 177, 204 and 232 C. The glass transition temperature and the type of bond failure were also determined. The best LSS values of the four adhesive systems investigated were obtained with the PAI copolymer identified in the report as LARC-TPI (25 percent 3,3'-DABA); however, it did not produce LSSs nearly as high as LARC-TPI. The poor flow properties observed appear to be due to a combination of high molecular weight and the increased interchain electronic interactions associated with the amide group.

Comparative Variable Temperature Studies of Polyamide II with a Benchtop Fourier Transform and a Miniature Handheld Near-Infrared Spectrometer Using 2D-COS and PCMW-2D Analysis.

PubMed

Unger, Miriam; Pfeifer, Frank; Siesler, Heinz W

2016-07-01

The main objective of this communication is to compare the performance of a miniaturized handheld near-infrared (NIR) spectrometer with a benchtop Fourier transform near-infrared (FT-NIR) spectrometer. Generally, NIR spectroscopy is an extremely powerful analytical tool to study hydrogen-bonding changes of amide functionalities in solid and liquid materials and therefore variable temperature NIR measurements of polyamide II (PAII) have been selected as a case study. The information content of the measurement data has been further enhanced by exploiting the potential of two-dimensional correlation spectroscopy (2D-COS) and the perturbation correlation moving window two-dimensional (PCMW2D) evaluation technique. The data provide valuable insights not only into the changes of the hydrogen-bonding structure and the recrystallization of the hydrocarbon segments of the investigated PAII but also in their sequential order. Furthermore, it has been demonstrated that the 2D-COS and PCMW2D results derived from the spectra measured with the miniaturized NIR instrument are equivalent to the information extracted from the data obtained with the high-performance FT-NIR instrument. © The Author(s) 2016.

Picosecond laser ablation of polyamide electrospun nanofibers

NASA Astrophysics Data System (ADS)

Götze, Marco; Krimig, Olaf; Kürbitz, Tobias; Henning, Sven; Heilmann, Andreas; Hillrichs, Georg

2017-02-01

Electrospun nanofibers mats have a great potential in tissue engineering and regenerative medicine. Their high porosity and enormous volume to surface ratio stimulate the growth and adhesion of mammalian cells and serve as a stable support structure. These suitable properties can be further optimized by structuring of the nanofibers. Ultrashort pulsed lasers can be used for modifying of the electrospun nanofibers without significant heat exposure. It seems also possible to generate very fine cuts from the fiber mats. In this study, polyamide electrospun nanofibers samples were processed with picosecond UV-laser irradiation (λ = 355 nm, τ = 15 ps). The samples were processed in dry, wet and immersed condition. To optimize cutting and structuring of nanofiber tissue flakes, the influence of different laser parameters on line widths, edge quality, heat-affected zone (HAZ) and the contamination of the fibers by ablated particles (debris) were examined. One additional aim was the minimization of the flake size. It was possible to generate nanofiber flakes in the sub-millimeter range. The quality of the nanofiber flakes could be improved by ablation near the ablation threshold of the material. For cutting under wet conditions shrinking of the flakes has to be taken into account.

Preparation and characterizations of flame retardant polyamide 66 fiber

NASA Astrophysics Data System (ADS)

Li, Y. Y.; Liu, K.; Xiao, R.

2017-06-01

The polyamide 66 (PA66) is one of the most important thermoplastic materials, but it has the drawback of flammability. So the flame retardant PA66 was prepared by condensation polymerization using nylon salt and DOPO-based flame retardant in this paper. Then the flame retardant PA66 fiber was manufactured via melt spinning. The properties of flame retardant PA66 and flame retardant PA66 fiber were investigated by relative viscosity, differential scanning calorimetry (DSC), tensile test, vertical burning test (UL94) and limiting oxygen index (LOI) test. Although the loading of the DOPO-based flame retardant decreased the molecular weight, the melting temperature, the crystallinity and the mechanical properties of flame retardant PA66, the flame retardancy properties improved. The flame retardant PA66 loaded with 5.5 wt% of DOPO-based flame retardant can achieve a UL94 V-0 rating with a LOI value of 32.9%. The tenacity at break decreased from 4.51 cN·dtex-1 for PA66 fiber to 2.82 cN·dtex-1 for flame retardant PA66 fiber which still satisfied the requirements for fabrics. The flame retardant PA66 fiber expanded the application of PA66 materials which had a broad developing prospect.

Development of a Cold Sterilant for Field Medical Use.

DTIC Science & Technology

1996-11-01

Dental Devices Using STERIS 20C at Use Dilution and Manual Soak Technique .............. 1086 Akron Rubber Development Laboratory Report 32918...simulated reuse protocol with lot P-2 of 25 months of age , a number of positives (i.e. sterilization failures) were noted, in particular for the...Ethylene propylene ELASTOMERS Brass Ethylene propylene diene Ethylene propylene diene ( EPDM ) ( EPDM ) Brass 360 Polyamide RTV 133 Nickel-plated Cooper

Material Selection Guide Derived from Material - Chemical Compatibility Database: Feasibility Based on Database and Predictive Model Evaluation

DTIC Science & Technology

1992-09-01

PI) 297 S S S S 15 Polyamideimide (PAI) 297 S S S S 14 Polyamide 6:6 (PA 6:6) 297 S S S S 35 Perfluoroakloxyethylene ( PFA ) 297 S S S S 42 Phenol...Procedures for the Measurement of Vapor Sorption Followed by Desorption and Comparisons with Polymer Cohesion Parameter and Polymer Coil Expansion Values

A study of the toxicology of pyrolysis gases from synthetic polymers

NASA Technical Reports Server (NTRS)

Young, W.; Hilado, C. J.; Kourtides, D. A.; Parker, J. A.

1976-01-01

An apparatus and procedure for evaluating the toxicity of pyrolysis gases from synthetic polymers are described. In each test, four Swiss albino mice are exposed in a 5-liter chamber to the gases from materials pyrolyzed at 700 C. The apparatus is simple in design, easy to clean, inexpensive and gives reproducible results. Data on several fluorine-containing and polyamide polymers are presented.

Observation and modeling of mixing-layer development in HED blast-wave-driven shear flow

NASA Astrophysics Data System (ADS)

di Stefano, Carlos

2013-10-01

This talk describes work exploring the sensitivity to initial conditions of hydrodynamic mixing-layer growth due to shear flow in the high-energy-density regime. This work features an approach in two parts, experimental and theoretical. First, an experiment, conducted at the OMEGA-60 laser facility, seeks to measure the development of such a mixing layer. This is accomplished by placing a layer of low-density (initially of either 0.05 or 0.1 g/cm3, to vary the system's Atwood number) carbon foam against a layer of higher-density (initially 1.4 g/cm3) polyamide-imide that has been machined to a nominally-flat surface at its interface with the foam. Inherent roughness of this surface's finish is precisely measured and varied from piece to piece. Ten simultaneous OMEGA beams, comprising a 4.5 kJ, 1-ns pulse focused to a roughly 1-mm-diameter spot, irradiate a thin polycarbonate ablator, driving a blast wave into the foam, parallel to its interface with the polyamide-imide. The ablator is framed by a gold washer, such that the blast wave is driven only into the foam, and not into the polyamide-imide. The subsequent forward motion of the shocked foam creates the desired shear effect, and the system is imaged by X-ray radiography 35 ns after the beginning of the driving laser pulse. Second, a simulation is performed, intending to replicate the flow observed in the experiment as closely as possible. Using the resulting simulated flow parameters, an analytical model can be used to predict the evolution of the mixing layer, as well as track the motion of the fluid in the experiment prior to the snapshot seen in the radiograph. The ability of the model to predict growth of the mixing layer under the various conditions observed in the experiment is then examined. This work is funded by the Predictive Sciences Academic Alliances Program in NNSA-ASC via grant DEFC52- 08NA28616, by the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas, grant number DE-NA0001840, and by the National Laser Use.

Ethynyl-Containing Aromatic Polyamide Resin.

DTIC Science & Technology

1988-06-21

added over two hours at 130"-150" C. and the final 17 polymer, e.g., an alcohol such as methanol, thereby ml was added over two hours at 150*-160* C...2,5A.(phayIbyly) 4,4’. Oxyd n flne 0.30 (b) 2W0 295 (c) etahaloyl chinde IV 2.S-bi(pmykihynyl) 4.,V-pbmyieue- 0.51 19 222 250 (c) tewephd loyl chloride

Fiber Reinforcement of Gun Propellants

DTIC Science & Technology

1982-06-02

finish, glass Keviar 1.5 mm Aromatic polyamide, DuPont Kevlar 29 Pulp Type 1979 Kynol 0.9 mm Cross linked amorphous phenolic polymer, 1Iarbison...meniscus even appears to indicate repulsion. Also, single fibers were dipped into molten TNT, with results shown in Fig. 6. Kevlar was the fiber type...slowly cooled, while observations were made. Figure 7 depicts the results of one such experiment. Again, Kevlar was used. The droplet shown resulted

Reconstruction of gas distribution pipelines in MOZG in Poland using PE and PA pipes

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

Borowicz, W.; Podziemski, T.; Kramek, E.

1996-12-31

MOZG--Warsaw Regional Gas Distribution Company was established in 1856. Now it is one of six gas distribution companies in Poland. Due to steadily increasing safety demands, some of the pipelines will need reconstruction. The majority of the substandard piping is located in urban areas. The company wanted to gain experiences in applying reconstruction technologies using two different plastic materials polyethylene and polyamide. They also wanted to assess the technical and economic practicalities of performing relining processes. A PE project--large diameter polyethylene relining (450 mm) conducted in Warsaw in 1994/95 and PA projects--relining using polyamide pipes, projects conducted in Radom andmore » in Warsaw during 1993 and 1994 are the most interesting and representative for this kind of works. Thanks to the experience obtained whilst carrying out these projects, reconstruction of old gas pipelines has become routine. Now they often use polyethylene relining of smaller diameters and they continue both construction and reconstruction of gas network using PA pipes. This paper presents the accumulated knowledge showing the advantages and disadvantages of applied methods. It describes project design and implementation with details and reports on the necessary preparation work, on site job organization and the most common problems arising during the construction works.« less

Isolation of PCR quality microbial community DNA from heavily contaminated environments.

PubMed

Gunawardana, Manjula; Chang, Simon; Jimenez, Abraham; Holland-Moritz, Daniel; Holland-Moritz, Hannah; La Val, Taylor P; Lund, Craig; Mullen, Madeline; Olsen, John; Sztain, Terra A; Yoo, Jennifer; Moss, John A; Baum, Marc M

2014-07-01

Asphalts, biochemically degraded oil, contain persistent, water-soluble compounds that pose a significant challenge to the isolation of PCR quality DNA. The adaptation of existing DNA purification protocols and commercial kits proved unsuccessful at overcoming this hurdle. Treatment of aqueous asphalt extracts with a polyamide resin afforded genomic microbial DNA templates that could readily be amplified by PCR. Physicochemically distinct asphalt samples from five natural oil seeps successfully generated the expected 291 bp amplicons targeting a region of the 16S rRNA gene, illustrating the robustness of the method. DNA recovery yields were in the 50-80% range depending on how the asphalt sample was seeded with exogenous DNA. The scope of the new method was expanded to include soil with high humic acid content. DNA from soil samples spiked with a range of humic acid concentrations was extracted with a commercial kit followed by treatment with the polyamide resin. The additional step significantly improved the purity of the DNA templates, especially at high humic acid concentrations, based on qPCR analysis of the bacterial 16S rRNA genes. The new method has the advantages of being inexpensive, simple, and rapid and should provide a valuable addition to protocols in the field of petroleum and soil microbiology. Copyright © 2014 Elsevier B.V. All rights reserved.

Electrochemical mineral scale prevention and removal on electrically conducting carbon nanotube--polyamide reverse osmosis membranes.

PubMed

Duan, Wenyan; Dudchenko, Alexander; Mende, Elizabeth; Flyer, Celeste; Zhu, Xiaobo; Jassby, David

2014-05-01

The electrochemical prevention and removal of CaSO4 and CaCO3 mineral scales on electrically conducting carbon nanotube - polyamide reverse osmosis membrane was investigated. Different electrical potentials were applied to the membrane surface while filtering model scaling solutions with high saturation indices. Scaling progression was monitored through flux measurements. CaCO3 scale was efficiently removed from the membrane surface through the intermittent application of a 2.5 V potential to the membrane surface, when the membrane acted as an anode. Water oxidation at the anode, which led to proton formation, resulted in the dissolution of deposited CaCO3 crystals. CaSO4 scale formation was significantly retarded through the continuous application of 1.5 V DC to the membrane surface, when the membrane was operated as an anode. The continuous application of a sufficient electrical potential to the membrane surface leads to the formation of a thick layer of counter-ions along the membrane surface that pushed CaSO4 crystal formation away from the membrane surface, allowing the formed crystals to be carried away by the cross-flow. We developed a simple model, based on a modified Poisson-Boltzmann equation, which qualitatively explained our observed experimental results.

Morphological, rheological and mechanical characterization of polypropylene nanocomposite blends.

PubMed

Rosales, C; Contreras, V; Matos, M; Perera, R; Villarreal, N; García-López, D; Pastor, J M

2008-04-01

In the present work, the effectiveness of styrene/ethylene-butylene/styrene rubbers grafted with maleic anhydride (MA) and a metallocene polyethylene (mPE) as toughening materials in binary and ternary blends with polypropylene and its nanocomposite as continuous phases was evaluated in terms of transmission electron microscopy (TEM), scanning electron microscopy (SEM), oscillatory shear flow and dynamic mechanical thermal analysis (DMA). The flexural modulus and heat distortion temperature values were determined as well. A metallocene polyethylene and a polyamide-6 were used as dispersed phases in these binary and ternary blends produced via melt blending in a corotating twin-screw extruder. Results showed that the compatibilized blends prepared without clay are tougher than those prepared with the nanocomposite of PP as the matrix phase and no significant changes in shear viscosity, melt elasticity, flexural or storage moduli and heat distortion temperature values were observed between them. However, the binary blend with a nanocomposite of PP as matrix and metallocene polyethylene phase exhibited better toughness, lower shear viscosity, flexural modulus, and heat distortion temperature values than that prepared with polyamide-6 as dispersed phase. These results are related to the degree of clay dispersion in the PP and to the type of morphology developed in the different blends.

Organometallic exposure dependence on organic–inorganic hybrid material formation in polyethylene terephthalate and polyamide 6 polymer fibers

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

Akyildiz, Halil I.; Jur, Jesse S., E-mail: jsjur@ncsu.edu

2015-03-15

The effect of exposure conditions and surface area on hybrid material formation during sequential vapor infiltrations of trimethylaluminum (TMA) into polyamide 6 (PA6) and polyethylene terephthalate (PET) fibers is investigated. Mass gain of the fabric samples after infiltration was examined to elucidate the reaction extent with increasing number of sequential TMA single exposures, defined as the times for a TMA dose and a hold period. An interdependent relationship between dosing time and holding time on the hybrid material formation is observed for TMA exposure PET, exhibited as a linear trend between the mass gain and total exposure (dose time ×more » hold time × number of sequential exposures). Deviation from this linear relationship is only observed under very long dose or hold times. In comparison, amount of hybrid material formed during sequential exposures to PA6 fibers is found to be highly dependent on amount of TMA dosed. Increasing the surface area of the fiber by altering its cross-sectional dimension is shown to have little on the reaction behavior but does allow for improved diffusion of the TMA into the fiber. This work allows for the projection of exposure parameters necessary for future high-throughput hybrid modifications to polymer materials.« less

Engineered soy oils for new value added applications

NASA Astrophysics Data System (ADS)

Tran, Phuong T.

Soybean oil is an abundant annually renewable resource. It is composed of triglycerides with long chain saturated and unsaturated fatty acids. The presence of unsaturated fatty acids allows for chemical modification to introduce new functionalities to soybean oil. A portfolio of chemically modified soy oil with suitable functional groups has been designed and engineered to serve as the starting material in applications such as polyamides, polyesters, polyurethanes, composites, and lubricants. Anhydride, hydroxyl, and silicone functionalities were introduced to soy oil. Anhydride functionality was introduced using a single-step free radical initiated process, and the chemically modified soy oils were evaluated for potential applications as a composite and lubricant. Hydroxyl functionalities were introduced in a single-step catalytic ozonolysis process recently developed in our labs, which proceeds rapidly and efficiently at room temperature without solvent. The transformed soy oil was used to successfully prepare bio-lubricants with good thermal/oxidative stability and bio-plastics such as polyamides, polyesters, and polyurethanes. A new class of organic-inorganic hybrid materials was prepared by curing vinyltrimethoxysilane functionalized soy oil. This hybrid material could have potential as biobased sealant through a moisture initiated room temperature cure. These new classes of soy-based materials are competitive both in cost and performance to petroleum based materials, but offer the advantage of being biobased.

Plasma-mediated grafting of poly(ethylene glycol) on polyamide and polyester surfaces and evaluation of antifouling ability of modified substrates.

PubMed

Dong, Baiyan; Jiang, Hongquan; Manolache, Sorin; Wong, Amy C Lee; Denes, Ferencz S

2007-06-19

A simple cold plasma technique was developed to functionalize the surfaces of polyamide (PA) and polyester (PET) for the grafting of polyethylene glycol (PEG) with the aim of reducing biofilm formation. The surfaces of PA and PET were treated with silicon tetrachloride (SiCl4) plasma, and PEG was grafted onto plasma-functionalized substrates (PA-PEG, PET-PEG). Different molecular weights of PEG and grafting times were tested to obtain optimal surface coverage by PEG as monitored by electron spectroscopy for chemical analysis (ESCA). The presence of a predominant C-O peak on the PEG-modified substrates indicated that the grafting was successful. Data from hydroxyl group derivatization and water contact angle measurement also indicated the presence of PEG after grafting. The PEG-grafted PA and PET under optimal conditions had similar chemical composition and hydrophilicity; however, different morphology changes were observed after grafting. Both PA-PEG and PET-PEG surfaces developed under optimal plasma conditions showed about 96% reduction in biofilm formation by Listeria monocytogenes compared with that of the corresponding unmodified substrates. This plasma functionalization method provided an efficient way to graft PEG onto PA and PET surfaces. Because of the high reactivity of Si-Cl species, this method could potentially be applied to other polymeric materials.

Chromate content versus particle size for aircraft paints.

PubMed

LaPuma, Peter T; Rhodes, Brian S

2002-12-01

Many industries rely on the corrosion inhibiting properties of chromate-containing primer paints to protect metal from oxidation. However, chromate contains hexavalent chromium (Cr(6+)), a known human carcinogen. The concentration of Cr(6+) as a function of paint particle size has important implications to worker health and environmental release from paint facilities. This research examines Cr(6+) content as a function of particle size for three types of aircraft primer paints: solvent-based epoxy-polyamide, water-based epoxy-polyamide, and solvent-based polyurethane. Cascade impactors were used to collect and separate paint particles based on their aerodynamic diameter, from 0.7 to 34.1 microm. The mass of the dry paint collected at each stage was determined and an atomic absorption spectrometer was used to analyze for Cr(6+) content. For all three paints, particles less than 7.0 microm contained disproportionately less Cr(6+) per mass of dry paint than larger particles, and the Cr(6+)concentration decreased substantially as particle size decreased. The smallest particles, 0.7 to 1.0 microm, contained approximately 10% of the Cr(6+) content, per mass of dry paint, compared to particles larger than 7.0 microm. The paint gun settings of air to paint ratio was found to have no influence on the Cr(6+) bias.

Reinforced nanohydroxyapatite/polyamide66 scaffolds by chitosan coating for bone tissue engineering.

PubMed

Huang, Di; Zuo, Yi; Zou, Qin; Wang, Yanying; Gao, Shibo; Wang, Xiaoyan; Liu, Haohuai; Li, Yubao

2012-01-01

High porosity of scaffold is always accompanied by poor mechanical property; the aim of this study was to enhance the strength and modulus of the highly porous scaffold of nanohydroxyapatite/polyamide66 (n-HA/PA66) by coating chitosan (CS) and to investigate the effect of CS content on the scaffold physical properties and cytological properties. The results show that CS coating can reinforce the scaffold effectively. The compress modulus and strength of the CS coated n-HA/PA66 scaffolds are improved to 32.71 and 2.38 MPa, respectively, being about six times and five times of those of the uncoated scaffolds. Meanwhile, the scaffolds still exhibit a highly interconnected porous structure and the porosity is approximate about 78%, slightly lower than the value (84%) of uncoated scaffold. The cytological properties of scaffolds were also studied in vitro by cocultured with osteoblast-like MG63 cells. The cytological experiments demonstrate that the reinforced scaffolds display favorable cytocompatibility and have no significant difference with the uncoated n-HA/PA66 scaffolds. The CS reinforced n-HA/PA66 scaffolds can meet the basic mechanical requirement of bone tissue engineering scaffold, presenting a potential for biomedical application in bone reconstruction and repair. Copyright © 2011 Wiley Periodicals, Inc.

Water Diffusion Mechanism in Carbon Nanotube and Polyamide Nanocomposite Reverse Osmosis Membranes: A Possible Percolation-Hopping Mechanism

NASA Astrophysics Data System (ADS)

Araki, Takumi; Cruz-Silva, Rodolfo; Tejima, Syogo; Ortiz-Medina, Josue; Morelos-Gomez, Aaron; Takeuchi, Kenji; Hayashi, Takuya; Terrones, Mauricio; Endo, Morinobu

2018-02-01

This paper is a contribution to the Physical Review Applied collection in memory of Mildred S. Dresselhaus. The mechanism of water diffusion across reverse osmosis nanocomposite membranes made of carbon nanotubes (CNTs) and aromatic polyamide is not completely understood despite its high potential for desalination applications. While most of the groups have proposed that superflow inside the CNT might positively impact the water flow across membranes, here we show theoretical evidence that this is not likely the case in composite membranes because CNTs are usually oriented parallel to the membrane surface, not to mention that sometimes the nanotube cores are occluded. Instead, we propose an oriented diffusion mechanism that explains the high water permeation by decreasing the diffusion path of water molecules across the membranes, even in the presence of CNTs that behave as impermeable objects. Finally, we provide a comprehensive description of the molecular dynamics occurring in water desalination membranes by considering the bond polarizability caused by dynamic charge transfer and explore the use of molecular-dynamics-derived stochastic diffusion simulations. The proposed water diffusion mechanism offers an alternative and most likely explanation for the high permeation phenomena observed in CNTs and PA nanocomposite membranes, and its understanding can be helpful to design the next generation of reverse osmosis desalination membranes.

Effects of DMSO and glycerol additives on the property of polyamide reverse osmosis membrane.

PubMed

Wu, Fengjing; Liu, Xiaojuan; Au, Chaktong

2016-10-01

The polyamide reverse osmosis (RO) membranes were prepared through interfacial polymerization of m-phenylenediamine (MPD) and trimesoyl chloride (TMC). The use of dimethyl sulfoxide (DMSO) and glycerol as additives for the formation of thin-film composite (TFC) was investigated. We studied the effect of DMSO and glycerol addition on membrane property and RO performance. Microscopic morphology was examined by atomic force microscopy and scanning electron microscopy. The surface hydrophilicity was characterized on the basis of water contact angle and surface solid-liquid interfacial free energy (-ΔG SL ). Water flux and salt rejection ability of the membranes prepared with or without the additives were evaluated by cross-flow RO tests. The results reveal that the addition of DMSO and glycerol strongly influences the property of the TFC RO membrane. Compared to the MPD/TMC membrane fabricated without DMSO and glycerol, the MPD/TMC/DMSO/glycerol membrane has a rougher surface and is more hydrophilic, showing smaller water contact angle and larger -ΔG SL value. Without decrease in salt rejection ability, the MPD/TMC/DMSO/glycerol membrane shows water flux significantly larger than that of the MPD/TMC membrane. The unique property of the MPD/TMC/DMSO/glycerol membrane is attributed to the cooperative effect of DMSO and glycerol on membrane structure during the interfacial polymerization process.

A Comparison of Water Diffusion in Polymer Based Fuel Cell and Reverse Osmosis Membrane Materials

NASA Astrophysics Data System (ADS)

Soles, Christopher; Frieberg, Bradley; Tarver, Jacob; Tyagi, Madhusudan; Jeong, Cheol; Chan, Edwin; Stafford, Christopher

Hydrated polymer membranes are critical in both fuel cells and water filtration and desalination. In both of these applications the membrane function (selectively transporting or separating ions) is coupled with the transport of water through the membrane. There is a significant need to understand the nature by which the water and ions distribute and move through these membranes. This presentation compares the transport mechanisms in in an ion containing block copolymer alkaline fuel cell membrane with that of a polyamide membrane that is used as the active layer in a reverse osmosis water desalination membrane. Small angle neutron scattering measurements are used to locally probe how water swells the different materials and quantitatively describe the distribution of water within the membrane microstructures. Quasielastic neutron scattering measurements are then used to separate the polymer dynamics of the host membranes from the dynamics of the water inside the membranes. This reveals that water moves at least an order of magnitude slower through the ion containing fuel cell membrane materials, consistent with a solution-diffusion model, while the water in the polyamide membranes moves faster, consistent with a pore-flow diffusion mechanism. These insights will be discussed in terms of a coupling of the water and polymer dynamics and design cues for high performance membrane materials.

Facile Modification of Reverse Osmosis Membranes by Surfactant-Assisted Acrylate Grafting for Enhanced Selectivity.

PubMed

Baransi-Karkaby, Katie; Bass, Maria; Levchenko, Stanislav; Eitan, Shahar; Freger, Viatcheslav

2017-02-21

The top polyamide layer of composite reverse osmosis (RO) membranes has a fascinatingly complex structure, yet nanoscale nonuniformities inherently present in polyamide layer may reduce selectivity, e.g., for boron rejection. This study examines improving selectivity by in situ "caulking" such nonuniformities using concentration polarization-enhanced graft-polymerization with a surfactant added to the reactive solution. The surfactant appears to enhance both polarization (via monomer solubilization in surfactant micelles) and adherence of graft-polymer to the membrane surface, which facilitates grafting and reduces monomer consumption. The effect of surfactant was particularly notable for a hydrophobic monomer glycidyl methacrylate combined with a nonionic surfactant Triton X-100. With Triton added at an optimal level, close to critical micellization concentration (CMC), monomer gets solubilized and highly concentrated within micelles, which results in a significantly increased degree of grafting and uniformity of the coating compared to a procedure with no surfactant added. Notably, no improvement was obtained for an anionic surfactant SDS or the cationic surfactant DTAB, in which cases the high CMC of surfactant precludes high monomer concentration within micelles. The modification procedure was also up-scalable to membranes elements and resulted in elements with permeability comparable to commercial brackish water RO elements with superior boric acid rejection.

Permeability and selectivity of reverse osmosis membranes: correlation to swelling revisited.

PubMed

Dražević, Emil; Košutić, Krešimir; Freger, Viatcheslav

2014-02-01

Membrane swelling governs both rejection of solutes and permeability of polymeric membranes, however very few data have been available on swelling in water of salt-rejecting reverse osmosis (RO) membranes. This study assesses swelling, thickness and their relation to water permeability for four commercial polyamide (PA) RO membranes (SWC4+, ESPA1, XLE and BW30) using atomic force microscopy (AFM) and attenuated total reflection Fourier transform IR spectroscopy (ATR-FTIR). ATR-FTIR offered a significantly improved estimate of the actual barrier thickness of PA, given AFM is biased by porosity ("fluffy parts") or wiggling of the active layer or presence of a coating layer. Thus obtained intrinsic permeability (permeability times thickness) and selectivity of aromatic polyamides plotted versus swelling falls well on a general trend, along with previously reported data on several common materials showing RO and NF selectivity. The observed general trend may be rationalized by viewing the polymers as a random composite medium containing molecularly small pores. The results suggest that the combination of a rigid low dielectric matrix, limiting the pore size, with multiple hydrophilic H-bonding sites may be a common feature of RO/NF membranes, allowing both high permeability and selectivity. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

Approaches to evaluating weathering effects on release of ...

EPA Pesticide Factsheets

Increased production and use of engineered nanomaterials (ENMs) over the past decade has increased the potential for the transport and release of these materials into the environment. Here we present results of two separate studies designed to simulate the effects of weathering on the potential release of multiwalled carbon nanotubes (MWCNTs) from polyamide or epoxy composites, and nanosilica from composites with low-density polyethylene (LOPE) with added pro-oxidant. With these weathering-resistant ENMs, the release was primarily driven by degradation of the polymer matrix. The MWCNT-polymer composites were investigated in a pilot inter-laboratory study to simulate the effects of weathering on the potential release of multiwalled carbon nanotubes (MWCNTs) from their composites with two polymers. Wafers of MWCNTs in epoxy and polyamide nanocomposi tes were exposed in four laboratories in the US and Europe under carefully controlled conditions to cycles of simulated sunlight and rainfall over a 2000-hour period. Particles released upon submersion of the weathered wafers in the leaching fluid described in EPA Method 1311 were analyzed by Transmission Electron Microscopy (TEM), Inductively Coupled Plasma- Mass Spectrometry (ICP-MS), and Ultraviolet-Visible Spectroscopy (UV-Vis). Rates ofrelease of MWCNTS determined by ICP-MS (Co associatedwith MWCNTS) and UY-Vis agreed within a factor of two. Other weathering studies of nanosilica-LDPE composites were conducted usi

Self-interrupted synthesis of sterically hindered aliphatic polyamide dendrimers

PubMed Central

Jishkariani, Davit; Timsina, Yam N.; Grama, Silvia; Gillani, Syeda S.; Divar, Masoumeh; Yadavalli, Srujana S.; Moussodia, Ralph-Olivier; Leowanawat, Pawaret; Berrios Camacho, Angely M.; Walter, Ricardo; Goulian, Mark; Klein, Michael L.; Percec, Virgil

2017-01-01

2,2-Bis(azidomethyl)propionic acid was prepared in four steps and 85% yield from the commercially available 2,2-bis(hydroxymethyl)propionic acid and used as the starting building block for the divergent, convergent, and double-stage convergent–divergent iterative methods for the synthesis of dendrimers and dendrons containing ethylenediamine (EDA), piperazine (PPZ), and methyl 2,2-bis(aminomethyl)propionate (COOMe) cores. These cores have the same multiplicity but different conformations. A diversity of synthetic methods were used for the synthesis of dendrimers and dendrons. Regardless of the method used, a self-interruption of the synthesis was observed at generation 4 for the dendrimer with an EDA core and at generation 5 for the one with a PPZ core, whereas for the COOMe core, self-interruption was observed at generation 6 dendron, which is equivalent to generation 5 dendrimer. Molecular modeling and molecular-dynamics simulations demonstrated that the observed self-interruption is determined by the backfolding of the azide groups at the periphery of the dendrimer. The latter conformation inhibits completely the heterogeneous hydrogenation of the azide groups catalyzed by 10% Pd/carbon as well as homogeneous hydrogenation by the Staudinger method. These self-terminated polyamide dendrimers are enzymatically and hydrolytically stable and also exhibit antimicrobial activity. Thus, these nanoscale constructs open avenues for biomedical applications. PMID:28270599

A Novel Approach Toward Fabrication of High Performance Thin Film Composite Polyamide Membranes.

PubMed

Khorshidi, Behnam; Thundat, Thomas; Fleck, Brian A; Sadrzadeh, Mohtada

2016-02-29

A practical method is reported to enhance water permeability of thin film composite (TFC) polyamide (PA) membranes by decreasing the thickness of the selective PA layer. The composite membranes were prepared by interfacial polymerization (IP) reaction between meta-phenylene diamine (MPD)-aqueous and trimesoyl chloride (TMC)-organic solvents at the surface of polyethersulfone (PES) microporous support. Several PA TFC membranes were prepared at different temperatures of the organic solution ranging from -20 °C to 50 °C. The physico-chemical and morphological properties of the synthesized membranes were carefully characterized using serval analytical techniques. The results confirmed that the TFC membranes, synthesized at sub-zero temperatures of organic solution, had thinner and smoother PA layer with a greater degree of cross-linking and wettability compared to the PA films prepared at 50 °C. We demonstrated that reducing the temperature of organic solution effectively decreased the thickness of the PA active layer and thus enhanced water permeation through the membranes. The most water permeable membrane was prepared at -20 °C and exhibited nine times higher water flux compared to the membrane synthesized at room temperature. The method proposed in this report can be effectively applied for energy- and cost-efficient development of high performance nanofiltration and reverse osmosis membranes.

Fabrication Of Carbon-Boron Reinforced Dry Polymer Matrix Composite Tape

NASA Technical Reports Server (NTRS)

Belvin, Harry L.; Cano, Roberto J.; Treasure, Monte; Shahood, Thomas W.

1999-01-01

Future generation aerospace vehicles will require specialized hybrid material forms for component structure fabrication. For this reason, high temperature composite prepregs in both dry and wet forms are being developed at NASA Langley Research Center (LaRC). In an attempt to improve compressive properties of carbon fiber reinforced composites, a hybrid carbon-boron tape was developed and used to fabricate composite laminates which were subsequently cut into flexural and compression specimens and tested. The hybrid material, given the designation HYCARB, was fabricated by modifying a previously developed process for the manufacture of dry polymer matrix composite (PMC) tape at LaRC. In this work, boron fibers were processed with IM7/LaRC(TradeMark)IAX poly(amide acid) solution-coated prepreg to form a dry hybrid tape for Automated Tow Placement (ATP). Boron fibers were encapsulated between two (2) layers of reduced volatile, low fiber areal weight poly(amide acid) solution-coated prepreg. The hybrid prepreg was then fully imidized and consolidated into a dry tape suitable for ATP. The fabrication of a hybrid boron material form for tow placement aids in the reduction of the overall manufacturing cost of boron reinforced composites, while realizing the improved compression strengths. Composite specimens were press-molded from the hybrid material and exhibited excellent mechanical properties.

Exposure assessment through realistic laboratory simulation of a soccer stadium fire.

PubMed

van Belle, N J C; van Putten, E M; de Groot, A C; Meeussen, V J A; Banus, S

2010-10-01

On Sunday April 13, 2008 a fire broke out on a grandstand in the Euroborg soccer stadium in Groningen The Netherlands. The polyamide chairs on the grandstand were set on fire and supporters were exposed to the emitted smoke which induced mild health effects. The Dutch government was concerned about potential health risks that such fires could have to exposed fans. Especially the exposure to toxic fumes was considered a risk because prior research has proven that large amounts of chemical compounds are emitted during the burning of chemical substances such as polyamide. Among these emitted compounds are HCN, CO, NO(x), NH(3) and volatile organic compounds. To study if supporters were exposed to hazardous chemical compounds we designed a laboratory controlled replica of a part of the grandstand of the Euroborg stadium to perform fire-experiments. This simulation of the fire under controlled circumstances proved that a wide variety of chemicals were emitted. Especially the emission of CO and NO(x) were high, but also the emission of formaldehyde might be toxicologically relevant. The emission of HCN and NH(3) were less than expected. Exposure assessment suggests that the exposure to NO(x) is the main health risk for the supporters that were present at the Euroborg fire. Copyright © 2010 Elsevier Ltd. All rights reserved.

Improved separation and antifouling properties of thin-film composite nanofiltration membrane by the incorporation of cGO

NASA Astrophysics Data System (ADS)

Li, Hongbin; Shi, Wenying; Du, Qiyun; Zhou, Rong; Zhang, Haixia; Qin, Xiaohong

2017-06-01

Poly(piperazine amide) composite nanofiltration (NF) membranes were modified through the incorporation of carboxylated graphene oxide (cGO) in the polyamide layer during the interfacial polymerization (IP) process on the polysulfone (PSF)/nonwoven fabric (NWF) ultrafiltration (UF) substrate membrane surface. The composition and morphology of the prepared NF membrane surface were determined by means of ATR-FTIR, SEM-EDX and AFM. The effects of cGO contents on membrane hydrophilicity, separation performance and antifouling properties were investigated through Water Contact Angle (WCA) analysis, the permeance and three-cycle fouling measurements. The growth model of cGO-incorporated polyamide thin-film was proposed. Compared to the original NF membranes, the surface hydrophilicity, water permeability, salt rejection and antifouling properties of the cGO-incorporated NF membrane had all improved. When cGO content was 100 ppm, the MgSO4 rejection of composite NF membrane reached a maximum value of 99.2% meanwhile membrane obtained an obvious enhanced water flux (81.6 L m-2 h-1, at 0.7 MPa) which was nearly three times compared to the virginal NF membrane. The cGO-incorporated NF membrane showed an excellent selectivity of MgSO4 and NaCl with the rejection ratio of MgSO4/NaCl of approximately 8.0.

Durability Characteristics Analysis of Plastic Worm Wheel with Glass Fiber Reinforced Polyamide.

PubMed

Kim, Gun-Hee; Lee, Jeong-Won; Seo, Tae-Il

2013-05-10

Plastic worm wheel is widely used in the vehicle manufacturing field because it is favorable for weight lightening, vibration and noise reduction, as well as corrosion resistance. However, it is very difficult for general plastics to secure the mechanical properties that are required for vehicle gears. If the plastic resin is reinforced by glass fiber in the fabrication process of plastic worm wheel, it is possible to achieve the mechanical properties of metallic material levels. In this study, the mechanical characteristic analysis of the glass-reinforced plastic worm wheel, according to the contents of glass fiber, is performed by analytic and experimental methods. In the case of the glass fiber-reinforced resin, the orientation and contents of glass fibers can influence the mechanical properties. For the characteristic prediction of plastic worm wheel, computer-aided engineering (CAE) analysis processes such as structural and injection molding analysis were executed with the polyamide resin reinforcement glass fiber (25 wt %, 50 wt %). The injection mold for fabricating the prototype plastic worm wheel was designed and made to reflect the CAE analysis results. Finally, the durability of prototype plastic worm wheel fabricated by the injection molding process was evaluated by the experimental method and the characteristics according to the glass fiber contents.

Durability Characteristics Analysis of Plastic Worm Wheel with Glass Fiber Reinforced Polyamide

PubMed Central

Kim, Gun-Hee; Lee, Jeong-Won; Seo, Tae-Il

2013-01-01

Plastic worm wheel is widely used in the vehicle manufacturing field because it is favorable for weight lightening, vibration and noise reduction, as well as corrosion resistance. However, it is very difficult for general plastics to secure the mechanical properties that are required for vehicle gears. If the plastic resin is reinforced by glass fiber in the fabrication process of plastic worm wheel, it is possible to achieve the mechanical properties of metallic material levels. In this study, the mechanical characteristic analysis of the glass-reinforced plastic worm wheel, according to the contents of glass fiber, is performed by analytic and experimental methods. In the case of the glass fiber-reinforced resin, the orientation and contents of glass fibers can influence the mechanical properties. For the characteristic prediction of plastic worm wheel, computer-aided engineering (CAE) analysis processes such as structural and injection molding analysis were executed with the polyamide resin reinforcement glass fiber (25 wt %, 50 wt %). The injection mold for fabricating the prototype plastic worm wheel was designed and made to reflect the CAE analysis results. Finally, the durability of prototype plastic worm wheel fabricated by the injection molding process was evaluated by the experimental method and the characteristics according to the glass fiber contents. PMID:28809248

Effects of packaging materials on storage quality of peanut kernels

PubMed Central

Fu, Xiaoji; Xing, Shengping; Xiong, Huiwei; Min, Hua; Zhu, Xuejing; He, Jialin; Mu, Honglei

2018-01-01

In order to obtain optimum packaging materials for peanut kernels, the effects of four types of packaging materials on peanut storage quality (coat color, acid value, germination rate, relative damage, and prevention of aflatoxin contamination) were examined. The results showed that packaging materials had a major influence on peanut storage quality indexes. The color of the peanut seed coat packaged in the polyester/aluminum/polyamide/polyethylene (PET/AL/PA/PE) composite film bag did not change significantly during the storage period. Color deterioration was slower with polyamide/polyethylene (PA/PE) packaging materials than with polyethylene (PE) film bags and was slower in PE bags than in the woven bags. The use of PET/AL/PA/PE and PA/PE bags maintained peanut quality and freshness for more than one year and both package types resulted in better germination rates. There were significant differences between the four types of packaging materials in terms of controlling insect pests. The peanuts packaged in the highly permeable woven bags suffered serious invasion from insect pests, while both PET/AL/PA/PE and PA/PE bags effectively prevented insect infection. Peanuts stored in PET/AL/PA/PE and PA/PE bags were also better at preventing and controlling aflatoxin contamination. PMID:29518085

Aerospace Plane Technology, Research and Development Efforts in Europe

DTIC Science & Technology

1991-07-25

to conventional titanium alloys. Moreover, ti- aluminide has one-half the weight of the material previously used at these high temperatures. Real Gas...for the engine’s blades , turbine blisk (a turbine disk with integral blades ), Page 44 GAO/NSIAID-91-194 Aerospace Plane Technology Chapter 3 European...X-30 fuselage section from silicon carbide-reinforced titanium and manufactured an X-30 fuel tank from a graphite-polyamide composite. Although

The use of a standardized gray reference card in dental photography to correct the effects of five commonly used diffusers on the color of 40 extracted human teeth.

PubMed

Hein, Sascha; Zangl, Michael

2016-01-01

The aim of this in vitro study was to investigate the color changes of human teeth caused by five different diffuser materials commonly used in dental photography, as well as software influence, and to confirm whether the use of a standardized gray reference card is effective in correcting these color changes during digital postproduction. Forty extracted human teeth were obtained from a specialized oral surgery practice in Cham, Germany. Five commonly used diffuser materials were chosen to be investigated, which included: polyethylene (PET), White Frost photographic paper, LumiQuest polyamide (nylon) material, 80 gsm white printing paper, and 3M linear polarizing filter sheet used for cross polarization. A digital single-lens reflex camera (Canon EOS 5D MKII) was used, together with a twin flash suitable for macrophotography (Canon MT-24EX Macro Twin Lite). Images were tethered into Adobe Lightroom CC using the RAW format. A standardized gray reference card (WhiBal, Michael Tapes Design) was used for exposure calibration and white balancing. Classic Color Me- ter software (Ricci Adams, version 1.6 (122)) was used to obtain CIE L*a*b* values of the specimens before and after white balancing and exposure correction. All diffusers caused visually perceivable color changes on the extracted teeth: White Frost (ΔE* 1.24; sd 0.47), 80 gsm printing paper (ΔE* 2.94; sd 0.35), LumiQuest polyamide (ΔE* 3.68; sd 0.54), PET (ΔE* 6.55; sd 0.41), and 3M linear polarizing filter sheet (ΔE* 7.58; sd 1.00). The use of a standardized gray reference card (WhiBal) could correct these values below the visually perceivable threshold: White Frost (ΔE* 0.58; sd 0.36), 80 gsm printing paper (ΔE* 0.93; sd 0.54), LumiQuest polyamide (ΔE* 0.66; sd 0.58), PET (ΔE* 0.59; sd 0.33), and 3M linear polarizing filter sheet (ΔE* 0.53; sd 0.42). The use of a standardized gray reference card with specified CIE L*a*b* values should be considered when diffusers are used in dental photography in order to reveal the color of preoperative situations (ie, shade documentation) and document postoperative results accurately.

Extinguishing agent for combustible metal fires

DOEpatents

Riley, John F.; Stauffer, Edgar Eugene

1976-10-12

A low chloride extinguishing agent for combustible metal fires comprising from substantially 75 to substantially 94 weight percent of sodium carbonate as the basic fire extinguishing material, from substantially 1 to substantially 5 weight percent of a water-repellent agent such as a metal stearate, from substantially 2 to substantially 10 weight percent of a flow promoting agent such as attapulgus clay, and from substantially 3 to substantially 15 weight percent of a polyamide resin as a crusting agent.

Trifluoromethyl-substituted polymers

NASA Technical Reports Server (NTRS)

1993-01-01

Current work sponsored by the grant at Southwest Texas State University is directed toward the synthesis and characterization of: (1) N-alkylated polyamides derived from o-fluorinated diacids; (2) highly fluorinated polyethers; (3) polyesters derived from 2-hydroxy-2-propyl substituted arenes and/or 2,5-difluoroterephthalic acid; and (4) silicon-containing fluoropolymers. Work during the period from 1 July to 31 Dec. 1993 focused primarily on items 3 and 4 and on the development of a phosphorus containing modification of '12F-PEK.'

Molecular Weight Measurement of Biobased Furan Polyamides via Non-Aqueous Potentiometric Titration

DTIC Science & Technology

2013-06-01

electromagnetic fields, all titrations were completed in a chemical hood, which acted as a Faraday cage (a shield used to blocks external static and...while using DMF as a solvent. Additionally, no Faraday cage was used in the experimental setup, so the titrations were conducted inside the chemical...monomer was becoming more soluble in glacial acetic acid and the amount of chlorobenzene had less of an effect on the solution properties (i.e

Demonstration of Multifunctional DNBM Corrosion Inhibitors in Protective Coatings for Naval Air/Weapon Systems

DTIC Science & Technology

1993-12-01

Evaluation of Increased Payloads 6 3.2 Microencapsulation Scale-up of Pilot DNBM 10 4 SURFACE TREATMENT OF MICROCAPSULES 11 4.1 Fumed Silica Additions to... Microencapsulated DNBM b. Fumed-Silica Mixed Microcapsules C. Solvent-Extracted Silanized Microcapsules Fig. 8 SEM Photomicrographs of Pilot-DNBM... Microcapsules 18 NAWCADWAR-94128-60 Section 5 FORMULATION AND TEST OF 100% DNBM AND MICROENCAPSULATED DNBM IN EPOXY-POLYAMIDE PRIMER At the start of the

Thermal Expansion Measurements of Polymer Matrix Composites and Syntactics

DTIC Science & Technology

1992-04-01

828 (Shell Chemical) epoxy combined with 50.0 PBW EPON® V-40 polyamide curing agent (Shell Chemical) and Owens Corning (E-780) polyester combined 1...with 24 oz. woven roving with an Owens Corning 463 finish. " A 3 x 1, S-2 glass with 27 oz. woven roving with an Owens Corning 933 finish, nominally...wet polyester resin ( Owens Corning E-780) and subsequently processing the composites using the standard vacuum bag cure cycle for this polyester

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

Polyamide as an efficient sorbent for simultaneous interface-free determination of three Sudan dyes in saffron and urine using high-performance liquid chromatography-ultra violet detection.

PubMed

Saeidi, Iman; Barfi, Behruz; Payrovi, Moazameh; Feizy, Javid; Sheibani, Hojat A; Miri, Mina; Ghollasi Moud, Farahnaz

2015-01-01

With polyamide (PA) as an efficient sorbent for solid phase extraction (SPE) of Sudan dyes II, III and Red 7B from saffron and urine, their determination by HPLC was performed. The optimum conditions for SPE were achieved using 7 mL methanol/water (1:9, v/v, pH 7) as the washing solvent and 3 mL tetrahydrofuran for elution. Good clean-up and high (above 90%) recoveries were observed for all the analytes. The optimized mobile phase composition for HPLC analysis of these compounds was methanol-water (70:30, v/v). The SPE parameters, such as the maximum loading capacity and breakthrough volume, were also determined for each analyte. The limits of detection (LODs), limits of quantification (LOQs), linear ranges and recoveries for the analytes were 4.6-6.6 microg/L, 13.0-19.8 microg/L, 13.0-5000 microg/L (r2>0.99) and 92.5%-113.4%, respectively. The precisions (RSDs) of the overall analytical procedure, estimated by five replicate measurements for Sudan II, III and Red 7B in saffron and urine samples were 2.3%, 1.8% and 3.6%, respectively. The developed method is simple and successful in the application to the determination of Sudan dyes in saffron and urine samples with HPLC coupled with UV detection.

Microbiological destruction of composite polymeric materials in soils

NASA Astrophysics Data System (ADS)

Legonkova, O. A.; Selitskaya, O. V.

2009-01-01

Representatives of the same species of microscopic fungi developed on composite materials with similar polymeric matrices independently from the type of soils, in which the incubation was performed. Trichoderma harzianum, Penicillium auranthiogriseum, and Clonostachys solani were isolated from the samples of polyurethane. Fusarium solani, Clonostachys rosea, and Trichoderma harzianum predominated on the surface of ultrathene samples. Ulocladium botrytis, Penicillium auranthiogriseum, and Fusarium solani predominated in the variants with polyamide. Trichoderma harzianum, Penicillium chrysogenum, Aspergillus ochraceus, and Acremonium strictum were isolated from Lentex-based composite materials. Mucor circinelloides, Trichoderma harzianum, and Penicillium auranthiogriseum were isolated from composite materials based on polyvinyl alcohol. Electron microscopy demonstrated changes in the structure of polymer surface (loosening and an increase in porosity) under the impact of fungi. The physicochemical properties of polymers, including their strength, also changed. The following substances were identified as primary products of the destruction of composite materials: stearic acid for polyurethane-based materials; imide of dithiocarbonic acid and 1-nonadecen in variants with ultrathene; and tetraaminopyrimidine and isocyanatodecan in variants with polyamide. N,N-dimethyldodecan amide, 2-methyloximundecanon and 2-nonacosane were identified for composites on the base of Lentex A4-1. Allyl methyl sulfide and imide of dithiocarbonic acid were found in variants with the samples of composites based on polyvinyl alcohol. The identified primary products of the destruction of composite materials belong to nontoxic compounds.

The emissions of monoaromatic hydrocarbons from small polymeric toys placed in chocolate food products.

PubMed

Marć, Mariusz; Formela, Krzysztof; Klein, Marek; Namieśnik, Jacek; Zabiegała, Bożena

2015-10-15

The article presents findings on the emissions of selected monoaromatic hydrocarbons from children's toys placed in chocolate food products. The emission test system involved the application of a new type of microscale stationary emission chamber, μ-CTE™ 250. In order to determine the type of the applied polymer in the manufacture of the tested toys, Fourier transform infrared spectroscopy and thermogravimetric analysis coupled with differential scanning calorimetry were used. It was found that the tested toy components or the whole toys (figurines) are made of two main types of polymers: polyamide and acrylonitrile-butadiene-styrene copolymer. Total number of studied small polymeric toys was 52. The average emissions of selected monoaromatic hydrocarbons from studied toys made of polyamide were as follows: benzene: 0.45 ± 0.33 ng/g; toluene: 3.3 ± 2.6 ng/g; ethylbenzene: 1.4 ± 1.4 ng/g; p,m-xylene: 2.5 ± 4.5 ng/g; and styrene: 8.2 ± 9.9 ng/g. In the case of studied toys made of acrylonitrile-butadiene-styrene copolymer the average emissions of benzene, toluene, ethylbeznene, p,m-xylene and styrene were: 0.31 ± 0.29 ng/g; 2.5 ± 1.4 ng/g; 4.6 ± 8.9 ng/g; 1.4 ± 1.1 ng/g; and 36 ± 44 ng/g, respectively. Copyright © 2015. Published by Elsevier B.V.

Fluorescent probes for nucleic Acid visualization in fixed and live cells.

PubMed

Boutorine, Alexandre S; Novopashina, Darya S; Krasheninina, Olga A; Nozeret, Karine; Venyaminova, Alya G

2013-12-11

This review analyses the literature concerning non-fluorescent and fluorescent probes for nucleic acid imaging in fixed and living cells from the point of view of their suitability for imaging intracellular native RNA and DNA. Attention is mainly paid to fluorescent probes for fluorescence microscopy imaging. Requirements for the target-binding part and the fluorophore making up the probe are formulated. In the case of native double-stranded DNA, structure-specific and sequence-specific probes are discussed. Among the latest, three classes of dsDNA-targeting molecules are described: (i) sequence-specific peptides and proteins; (ii) triplex-forming oligonucleotides and (iii) polyamide oligo(N-methylpyrrole/N-methylimidazole) minor groove binders. Polyamides seem to be the most promising targeting agents for fluorescent probe design, however, some technical problems remain to be solved, such as the relatively low sequence specificity and the high background fluorescence inside the cells. Several examples of fluorescent probe applications for DNA imaging in fixed and living cells are cited. In the case of intracellular RNA, only modified oligonucleotides can provide such sequence-specific imaging. Several approaches for designing fluorescent probes are considered: linear fluorescent probes based on modified oligonucleotide analogs, molecular beacons, binary fluorescent probes and template-directed reactions with fluorescence probe formation, FRET donor-acceptor pairs, pyrene excimers, aptamers and others. The suitability of all these methods for living cell applications is discussed.

In Vitro and In Vivo Evaluations of Nano-Hydroxyapatite/Polyamide 66/Glass Fibre (n-HA/PA66/GF) as a Novel Bioactive Bone Screw

PubMed Central

Su, Bao; Peng, Xiaohua; Jiang, Dianming; Wu, Jun; Qiao, Bo; Li, Weichao; Qi, Xiaotong

2013-01-01

In this study, we prepared nano-hydroxyapatite/polyamide 66/glass fibre (n-HA/PA66/GF) bioactive bone screws. The microstructure, morphology and coating of the screws were characterised, and the adhesion, proliferation and viability of MC3T3-E1 cells on n-HA/PA66/GF scaffolds were determined using scanning electron microscope, CCK-8 assays and cellular immunofluorescence analysis. The results confirmed that n-HA/PA66/GF scaffolds were biocompatible and had no negative effect on MC3T3-E1 cells in vitro. To investigate the in vivo biocompatibility, internal fixation properties and osteogenesis of the bioactive screws, both n-HA/PA66/GF screws and metallic screws were used to repair intercondylar femur fractures in dogs. General photography, CT examination, micro-CT examination, histological staining and biomechanical assays were performed at 4, 8, 12 and 24 weeks after operation. The n-HA/PA66/GF screws exhibited good biocompatibility, high mechanical strength and extensive osteogenesis in the host bone. Moreover, 24 weeks after implantation, the maximum push-out load of the bioactive screws was greater than that of the metallic screws. As shown by their good cytocompatibility, excellent biomechanical strength and fast formation and ingrowth of new bone, n-HA/PA66/GF screws are thus suitable for orthopaedic clinical applications. PMID:23861888

The surface characteristics of hyperbranched polyamide modified corncob and its adsorption property for Cr(VI)

NASA Astrophysics Data System (ADS)

Lin, Hai; Han, Shaoke; Dong, Yingbo; He, Yinhai

2017-08-01

A low-cost anion adsorbent for Cr(VI) effectively removing was synthesized by hyperbranched polyamide modified corncob (HPMC). Samples were characterized by Brunauer-Emmett-Teller (BET) surface area analysis, field-emission scanning electron microscopy (FE-SEM) with energy-dispersive X-ray spectroscopy, Fourier transform infrared (FTIR) and zeta potential analysis. Kinetics, isotherms and thermodynamics studies of HPMC for Cr(VI) adsorption were investigated in batch static experiments, in the temperature range of 25-45 °C, pH = 2.0. Results showed that the adsorption was rapid and stable, with the uptake capacity higher than 80% after 30 min. Adsorption behavior and rate-controlling mechanisms were analyzed using three kinetic models (pseudo-first order, pseudo-second order, intra-particle kinetic model). Kinetic studies showed that the adsorption of HPMC to Cr(VI) relied the pseudo-second-order model, and controlled both by the intra-particle diffusion and film diffusion. Equilibrium data was tested by Langmuir and Freundlich adsorption isotherm models. Langmuir model was more suitable to indicate a homogeneous distribution of active sites on HPMC and monolayer adsorption. The maximum adsorption capacity from the Langmuir model, qmax, was 131.6 mg/g at pH 2.0 and 45 °C for HPMC. Thermodynamic parameters revealed spontaneous and endothermic nature of the Cr(VI) adsorption onto HPMC.

Long-term results of anterior cervical corpectomy and fusion with nano-hydroxyapatite/polyamide 66 strut for cervical spondylotic myelopathy

NASA Astrophysics Data System (ADS)

Zhang, Yuan; Deng, Xu; Jiang, Dianming; Luo, Xiaoji; Tang, Ke; Zhao, Zenghui; Zhong, Weiyang; Lei, Tao; Quan, Zhengxue

2016-05-01

To assess the long-term clinical and radiographic outcomes of anterior cervical corpectomy and fusion (ACCF) with a neotype nano-hydroxyapatite/polyamide 66 (n-HA/PA66) strut in the treatment of cervical spondylotic myelopathy (CSM). Fifty patients with CSM who underwent 1- or 2-level ACCF with n-HA/PA66 struts were retrospectively investigated. With a mean follow-up of 79.6 months, the overall mean JOA score, VAS and cervical alignment were improved significantly. At last follow-up, the fusion rate was 98%, and the subsidence rate of the n-HA/PA66 strut was 8%. The “radiolucent gap” at the interface between the n-HA/PA66 strut and the vertebra was further noted to evaluate the osteoconductivity and osseointegration of the strut, and the incidence of it was 62% at the last follow-up. Three patients suffered symptomatic adjacent segment degeneration (ASD). No significant difference was detected in the outcomes between 1- and 2-level corpectomy at follow-ups. In conclusion, the satisfactory outcomes in this study indicated that the n-HA/PA66 strut was an effective graft for cervical reconstruction. Moreover, the osteoconductivity and osseointegration of the strut is still need to be optimized for future clinical application owing to the notably presence of “radiolucent gap” in present study.

Nanofiltration of Mine Water: Impact of Feed pH and Membrane Charge on Resource Recovery and Water Discharge

PubMed Central

Mullett, Mark; Fornarelli, Roberta; Ralph, David

2014-01-01

Two nanofiltration membranes, a Dow NF 270 polyamide thin film and a TriSep TS 80 polyamide thin film, were investigated for their retention of ionic species when filtering mine influenced water streams at a range of acidic pH values. The functional iso-electric point of the membranes, characterized by changes in retention over a small pH range, were examined by filtering solutions of sodium sulphate. Both membranes showed changes in retention at pH 3, suggesting a zero net charge on the membranes at this pH. Copper mine drainage and synthetic solutions of mine influenced water were filtered using the same membranes. These solutions were characterized by pH values within 2 and 5, thus crossing the iso-electric point of both membranes. Retention of cations was maximized when the feed solution pH was less than the iso-electric point of the membrane. In these conditions, the membrane has a net positive charge, reducing the transmission rate of cations. From the recoveries of a range of cations, the suitability of nanofiltration was discussed relative to the compliance with mine water discharge criteria and the recovery of valuable commodity metals. The nanofiltration process was demonstrated to offer advantages in metal recovery from mine waste streams, concomitantly enabling discharge criteria for the filtrate disposal to be met. PMID:24957170

Efficient and reusable polyamide-56 nanofiber/nets membrane with bimodal structures for air filtration.

PubMed

Liu, Bowen; Zhang, Shichao; Wang, Xueli; Yu, Jianyong; Ding, Bin

2015-11-01

Nanofibrous media that both possess high airborne particle interception efficiency and robust air permeability would have broad technological implications for areas ranging from individual protection and industrial security to environmental governance; however, creating such filtration media has proved extremely challenging. Here we report a strategy to construct the bio-based polyamide-56 nanofiber/nets (PA-56 NFN) membranes with bimodal structures for effective air filtration via one-step electrospinning/netting. The PA-56 membranes are composed of completely covered two-dimensional (2D) ultrathin (∼20 nm) nanonets which are optimized by facilely regulating the solution concentration, and the bonded scaffold fibers constructed cavity structures which are synchronously created by using the CH3COOH inspiration. With integrated properties of small aperture, high porosity, and bonded scaffold, the resulting PA-56 NFN membranes exhibit high filtration efficiency of 99.995%, low pressure drop of 111 Pa, combined with large dust holding capacity of 49 g/m(2) and dust-cleaning regeneration ability, for filtrating ultrafine airborne particles in the most safe manner involving sieving principle and surface filtration. The successful synthesis of PA-56 NFN medium would not only make it a promising candidate for air filtration, but also provide new insights into the design and development of nanonet-based bimodal structures for various applications. Copyright © 2015 Elsevier Inc. All rights reserved.

Antibacterial chitosan coating on nano-hydroxyapatite/polyamide66 porous bone scaffold for drug delivery.

PubMed

Huang, Di; Zuo, Yi; Zou, Qin; Zhang, Li; Li, Jidong; Cheng, Lin; Shen, Juan; Li, Yubao

2011-01-01

This study describes a new drug-loaded coating scaffold applied in infection therapy during bone regeneration. Chitosan (CS) containing antibacterial berberine was coated on a nano-hydroxyapatite/polyamide66 (n-HA/PA66) scaffold to realize bone regeneration together with antimicrobial properties. The porous scaffold was fabricated using the phase-inversion method with a porosity of about 84% and macropore size of 400-600 μm. The morphology, mechanical properties and drug-release behavior were investigated at different ratios of chitosan to berberine. The results show that the elastic modulus and compressive strength of the coated scaffolds were improved to 35.4 MPa and 1.7 MPa, respectively, about 7 times and 3 times higher than the uncoated scaffolds. After a burst release of berberine within the first 3 h in PBS solution, a continuous berberine release can last 150 h, which is highly dependent on the coating concentration and suitable for antibacterial requirement of orthopaedic surgery. The bactericidal test confirms a strong antibiotic effect of the delivery system and the minimum inhibitory concentration of the drug is 0.02 mg/ml. Moreover, in vitro biological evaluation demonstrates that the coating scaffolds act as a good matrix for MG63 adhesion, crawl, growth and proliferation, suggesting that the antibacterial delivery system has no cytotoxicity. We expect the drug-delivery system to have a potential application in bone regeneration or defect repair.

Microplastics Reduce Short-Term Effects of Environmental Contaminants. Part I: Effects of Bisphenol A on Freshwater Zooplankton Are Lower in Presence of Polyamide Particles.

PubMed

Rehse, Saskia; Kloas, Werner; Zarfl, Christiane

2018-02-06

Abstract : Microplastics can have direct physical effects on organisms in freshwater systems, and are considered as vectors for absorbed environmental pollutants. It is still under discussion if microplastics are relevant pollutant vectors for uptake into aquatic organisms in comparison to further uptake pathways, e.g., via water or sediment particles. We analyzed how the presence of microplastics (polyamide particles, PA) modifies acute effects of the environmental pollutant bisphenol A (BPA) on freshwater zooplankton ( Daphnia magna ). Daphnids were exposed to PA particles and BPA alone, before combining them in the next step with one concentration of PA and varying concentrations of BPA. The PA particles themselves did not induce negative effects, while the effects of BPA alone followed a typical dose-dependent manner. Sorption of BPA to PA particles prior to exposure led to a reduction of BPA in the aqueous phase. The combination of BPA and PA led to decreased immobilization, although PA particles loaded with BPA were ingested by the daphnids. Calculations based on physiochemistry and equilibrium assumptions indicated lower BPA body burden of daphnids in the presence of PA particles. These results confirm model-based studies, and show that investigated microplastic concentrations are negligible for the overall pollutant uptake of daphnids with water as additional uptake pathway.

Permeability of uncharged organic molecules in reverse osmosis desalination membranes.

PubMed

Dražević, Emil; Košutić, Krešimir; Svalina, Marin; Catalano, Jacopo

2017-06-01

Reverse osmosis (RO) membranes are primarily designed for removal of salts i.e. for desalination of brackish and seawater, but they have also found applications in removal of organic molecules. While it is clear that steric exclusion is the dominant removal mechanism, the fundamental explanation for how and why the separation occurs remains elusive. Until recently there was no strong microscopic evidences elucidating the structure of the active polyamide layers of RO membranes, and thus they have been conceived as "black boxes"; or as an array of straight capillaries with a distribution of radii; or as polymers with a small amount of polymer free domains. The knowledge of diffusion and sorption coefficients is a prerequisite for understanding the intrinsic permeability of any organic solute in any polymer. At the same time, it is technically challenging to accurately measure these two fundamental parameters in very thin (20-300 nm) water-swollen active layers. In this work we have measured partition and diffusion coefficients and RO permeabilities of ten organic solutes in water-swollen active layers of two types of RO membranes, low (SWC4+) and high flux (XLE). We deduced from our results and recent microscopic studies that the solute flux of organic molecules in polyamide layer of RO membranes occurs in two domains, dense polymer (the key barrier layer) and the water filled domains. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effect of polyamide 6 on the morphology and electrical conductivity of carbon black-filled polypropylene composites

NASA Astrophysics Data System (ADS)

Zhang, Xuewei; Liu, Jiang; Wang, Yi; Wu, Wei

2017-12-01

Carbon black (CB)-filled polypropylene (PP) with surface resistivity between 106 and 109 Ω sq-1 is the ideal antistatic plastic material in the electronics and electric industry. However, a large amount of CB may have an adverse effect on the mechanical properties and processing performance of the material, thus an improved ternary system is developed. Blends of CB-filled PP and polyamide 6 (PA6) have been prepared by melt blending in order to obtain electrically conductive polymer composites with a low electrical percolation threshold based on the concept of double percolation. The morphological developments of these composites were studied by scanning electron microscopy. The results showed that CB particles were selectively dispersed in PA6 phases due to the good interaction and interfacial adhesion between CB and PA6. At the same CB loadings, the surface resistivity of PP/PA6/CB composite was smaller than that of PP/CB composite system, which indicated the better conductivity in the former composite. The increasing amount of PA6 in the composites changed the morphology from a typical sea-island morphology to a co-continuous morphology. What is more, with 8 wt% of CB and PP/PA6 phase ratio of 70/30 in which the PP and PA6 phases formed a co-continuous structure, the electrical conductivity of the composite peaked at 2.01 × 105 Ω sq-1.

Electroencephalographic study showing that tactile stimulation by fabrics of different qualities elicit graded event-related potentials.

PubMed

Hoefer, D; Handel, M; Müller, K-M; Hammer, T R

2016-11-01

Neurophysiologic data on reactions of the human brain towards tactile stimuli evoked by fabrics moved on the skin are scarce. Furthermore, evaluation of fabrics' pleasantness using questionnaires suffers subjective biases. That is why we used a 64-channel electroencephalography (EEG) to objectively evaluate real-time brain reactions to fabric-skin interactions. Tactile stimuli were triggered by selected fabrics of different qualities, i.e. modal/polyamide single jersey, cotton double rib and a jute fabric, applied hidden to either the palm or forearm of 24 subjects via a custom-made fabric-to-skin applicator called SOFIA. One-way anova analysis was carried out to verify the EEG data. The modal/polyamide fabric applied to the forearm and palm led to slightly stronger emotional valence scores in the brain than the conventional or baseline fabric. Furthermore, the single jersey elicits significant higher event-related potential (ERP) signals in all subjects when applied to the forearm, suggesting less distraction and better cognitive resources during the fabric/skin interaction. The brain thus reacts with instantaneous ERP to tactile stimulation of fabrics and is able to discriminate different qualities via implicit preferences. The test procedure described here may be a tool to evaluate the fabric feel with the exclusion of subjective biases. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Robust fabrication of thin film polyamide-TiO2 nanocomposite membranes with enhanced thermal stability and anti-biofouling propensity.

PubMed

Khorshidi, Behnam; Biswas, Ishita; Ghosh, Tanushree; Thundat, Thomas; Sadrzadeh, Mohtada

2018-01-15

The development of nano-enabled composite materials has led to a paradigm shift in the manufacture of high-performance nanocomposite membranes with enhanced permeation, thermo-mechanical, and antibacterial properties. The major challenges to the successful incorporation of nanoparticles (NPs) to polymer films are the severe aggregation of the NPs and the weak compatibility of NPs with polymers. These two phenomena lead to the formation of non-selective voids at the interface of the polymer and NPs, which adversely affect the separation performance of the membrane. To overcome these challenges, we have developed a new method for the fabrication of robust TFN reverse osmosis membranes. This approach relies on the simultaneous synthesis and surface functionalization of TiO 2 NPs in an organic solvent (heptane) via biphasic solvothermal reaction. The resulting stable suspension of the TiO 2 NPs in heptane was then utilized in the interfacial (in-situ) polymerization reaction where the NPs were entrapped within the matrix of the polyamide (PA) membrane. TiO 2 NPs of 10 nm were effectively incorporated into the thin PA layer and improved the thermal stability and anti-biofouling properties of the resulting TFN membranes. These features make our synthesized membranes potential candidates for applications where the treatment of high-temperature streams containing biomaterials is desirable.

Preparation of polyamide nanocapsules of Aloe vera L. delivery with in vivo studies.

PubMed

Esmaeili, Akbar; Ebrahimzadeh, Maryam

2015-04-01

Aloe vera is the oldest medicinal plant ever known and the most applied medicinal plant worldwide. The purpose of this study was to prepare polyamide nanocapsules containing A. vera L. by an emulsion diffusion technique with in vivo studies. Diethyletriamine (DETA) was used as the encapsulating polymer with acetone ethyl acetate and dimethyl sulfoxide (DMSO) as the organic solvents and Tween and gelatin in water as the stabilizers. Sebacoyl chloride (SC) monomer, A. vera L. extract, and olive oil were mixed with the acetone and then water containing DETA monomer was added to the solution using a magnetic stirrer. Finally, the acetone was removed under vacuum, and nanocapsules were obtained using a freeze drier. This study showed that the size of the nanocapsule depends on a variety of factors such as the ratio of polymer to oil, the concentration of polymers, and the plant extract. The first sample is without surfactant and the size of nanocapsules in the sample is 115 nm. By adding surfactant, nanocapsules size was reduced to 96 nm. Nanocapsules containing A. vera were administered to rats and the effects were compared with a normal control group. The results showed that in the A. vera group, the effect is higher. The nanocapsules were identified by scanning electron microscopy (SEM), zeta potential sizer (ZPS), and Fourier-transform infrared spectroscopy (FT-IR).

Biosynthesis and physicochemical characterization of a bacterial polysaccharide/polyamide blend, applied for microfluidics study in porous media.

PubMed

Bajestani, Maryam Ijadi; Mousavi, Seyyed Mohammad; Jafari, Arezou; Shojaosadati, Seyed Abbas

2017-03-01

Screening among some new isolated bacteria from oily samples, which were capable of producing extracellular polymeric substances (EPSs), one was selected and identified as Bacillus sonorensis. An efficient micro-total analysis approach was carried out to assay the produced EPSs by this bacterium. Sucrose and yeast concentrations as carbon and nitrogen sources, respectively, sodium salt concentration and initial pH were selected to be the variables in experimental design. Production of EPS in optimal condition was increased by 5.3 times. Further EPS purification was carried out to identify the biopolymers. The bacteria produced high molecular weight biopolymers with a number average molecular weight (M̅n) of 9.1×10 6 g/mol determined by gel permeation chromatography (GPC). Biopolymer characterization demonstrated the biosynthesis of both polysaccharides and polyamides by the bacteria. For the biopolymer blend, thermal properties and morphological characteristics were studied using simultaneous differential scanning calorimetric and thermal gravimetric analyses (DSC/TGA) and field emission scanning electron microscope (FESEM) analyses. Finally, the biopolymer blend was injected into an oil saturated glass micro model to study the enhancement of oil recovery by biopolymer flooding in contrast with water flooding. It was found that oil recovery increased by 36%, from 23% using water flooding to 59% for biopolymer injection. Copyright © 2016 Elsevier B.V. All rights reserved.

Microplastics Reduce Short-Term Effects of Environmental Contaminants. Part I: Effects of Bisphenol A on Freshwater Zooplankton Are Lower in Presence of Polyamide Particles

PubMed Central

Rehse, Saskia; Kloas, Werner; Zarfl, Christiane

2018-01-01

Microplastics can have direct physical effects on organisms in freshwater systems, and are considered as vectors for absorbed environmental pollutants. It is still under discussion if microplastics are relevant pollutant vectors for uptake into aquatic organisms in comparison to further uptake pathways, e.g., via water or sediment particles. We analyzed how the presence of microplastics (polyamide particles, PA) modifies acute effects of the environmental pollutant bisphenol A (BPA) on freshwater zooplankton (Daphnia magna). Daphnids were exposed to PA particles and BPA alone, before combining them in the next step with one concentration of PA and varying concentrations of BPA. The PA particles themselves did not induce negative effects, while the effects of BPA alone followed a typical dose-dependent manner. Sorption of BPA to PA particles prior to exposure led to a reduction of BPA in the aqueous phase. The combination of BPA and PA led to decreased immobilization, although PA particles loaded with BPA were ingested by the daphnids. Calculations based on physiochemistry and equilibrium assumptions indicated lower BPA body burden of daphnids in the presence of PA particles. These results confirm model-based studies, and show that investigated microplastic concentrations are negligible for the overall pollutant uptake of daphnids with water as additional uptake pathway. PMID:29415519

A Controlled Design of Ripple-Like Polyamide-6 Nanofiber/Nets Membrane for High-Efficiency Air Filter.

PubMed

Zhang, Shichao; Liu, Hui; Zuo, Fenglei; Yin, Xia; Yu, Jianyong; Ding, Bin

2017-03-01

The filtration capacity of fibrous media for airborne particles is restricted by their thick diameter, low porosity, and limited frontal area. The ability to solve this problem would have broad technological implications for various air filtration applications; despite many past efforts, it remains a great challenge to achieve. Herein, a facile and scalable strategy to fabricate the ripple-like polyamide-6 nanofiber/nets (PA-6 NF/N) air filter via combining electrospinning/netting technique with receiving substrate design is demonstrated. This proposed approach allows the scaffold filaments to orderly embed into 2D PA-6 nanonets layer with Steiner-tree structures and nanoscale diameter of ≈20 nm, resulting in the ripple-like membrane with extremely small pore size, highly porous structure, and hugely extended frontal surface, by facilely adjusting its pleat span and pleat pitch. These unique structural advantages enable the ripple-like PA-6 NF/N filter to filtrate the ultrafine particles with high removal efficiency of 99.996%, low air resistance of 95 Pa, and robust quality factor of >0.11 Pa -1 ; using its superlight weight of 0.9 g m -2 and physical sieving manner. This approach has the potentialities to give rise to a novel generation of filter media displaying enhanced filtration capacity for various applications thanks to their nanoscale features and designed macrostructures. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

[Isolation and characterization of polyphenols in seed of Litchi chinensis].

PubMed

Yan, Ren-Liang; Liu, Zhi-Gang

2009-04-01

To study the chemical constituents of polyphenols in seed of Litchi chinensis. The seeds of Litchi chinensis were extracted by 65% ethanol, then the compounds were separated by repeated silica gel, polyamide and preparative TLC. The structures of polyphones isolated were identified by analysis of their spectral datas and chemical properties. Four polyphones compounds were isolated as protocatechuic aldehyde (I), protocatechuic acid (II), daucosterol (III) and (-) -epicatichin (IV). Compounds I , III and IV are isolated from this plant for the first time.

[Study on the chemical constituents of flavones from corn silk].

PubMed

Zhang, Hui-en; Xu, De-ping

2007-02-01

The three flavones were isolated from water extracts of corn silk by chromatography on macroporous resin, polyamide, ODS and Sephadex LH-20. Three compounds were identified as formononetin (7-hydroxy-4'-methoxyisoflavone) ( I ) ,2"-O-alpha-L-rham-nosyl-6-C-( 3-deoxyglucosyl) -3 '-methoxyluteolin( II ) ,2"-O-alpha-L-rhamnosyl-6-C-( 6-deoxy-ax-5-methyl-xylo-hexos-4-ulosyl) -3'-methoxyluteolin( II ). Compounds ( I ) and ( II ) were isolated from the corn silk for the first time.

Corrosion Control through a Better Understanding of the Metallic Substrate/Organic Coating/Interface

DTIC Science & Technology

1986-01-31

epoxy polyamide on all remaining steel. Panels were aged for a minimum of 10 days in a desiccator prior to testing. Delamination experiments were...determine the heats of polymer adsorption per mole of polymer. The heats of polymer adsorption per site are important parameters for understanding the...measured, the E and C parameters . the acidic surface sites were determined: for silica, CA - 1.16 ± O.0, and E^ - 43 ± 0.1; for rutile, CA - 1.02 ± 0.03 and

Real-Time Ballistic Impact Deformation and Strain Measurements of Transparent TROGAMID Polyamides

DTIC Science & Technology

2011-09-01

Pandya, S.; Hosein, N.; Sacks, M. S.; Hwang, N. H. C. Bioprosthetic Hear Valve Leaflet Motion Monitored by Dual Camera Stereo Photogrammetry. J...TROGAMID CX-7323 against a 0.22-cal. FSP at velocities of 167 and 350 m/s (the white spot is indicative of a discontinuity due to fracture ...against a 0.22-cal. FSP at velocities of 167 and 350 m/s (the white spot is indicative of a discontinuity due to fracture ). 6 Figure 6. Plots of

One-Piece Leak-Proof Battery

DOEpatents

Verhoog, Roelof

1999-03-23

The casing of a leak-proof one-piece battery is made of a material comprising a mixture of at least a matrix based on polypropylene and an alloy of a polyamide and a polypropylene. The ratio of the matrix to the alloy is in the range 0.5 to 6 by weight. The alloy forms elongate arborescent inclusions in the matrix such that, on average, the largest dimension of a segment of the arborescence is at least twenty times the smallest dimension of the segment.

[Determination of ampelopsin and myricetin in Ampelopsis cantoniensis].

PubMed

Chen, Z; Wang, M; Cai, P; Chen, X

1997-01-01

Ampelopsis cantoniensis (Hook. et Arn.) Planch. is a Chinese herbal medicine rich in flavonoids. A method to determine flavonoids in the herbal was studied. After the herbal was extracted in hot water, Ampelopsin and myricetin in the extract were separated by polyamide column with eluent of ethanol-water and measured by spectrophotometry. As results, 100 g of the dry herbal contains 25.2 g of ampelopsin (RSD = 1.7%, recovery = 97.0%) and 1.77 g of myricetin (RSD = 3.3%, recovery = 103%).

The Effect of Substrate Contaminates on the Life of Epoxy Coatings Submerged in Sea Water

DTIC Science & Technology

1991-03-01

contaminants: coal tar, SovaPon, Mare Island and Aquapon . Aquapon is a clear (unpigmented) polyamide epoxy coating. While Aquapon is not normally used for...pigmented coatings. It was found that the Aquapon and coal tar coatings performed similarly, and blistered to the same extent, at the contamination levels...used in the test program. The Sovapon and Mare Island coatings were slightly more resistive to blistering when compared to Aquapon or coal tar but they

Adsorption of antibiotics on microplastics.

PubMed

Li, Jia; Zhang, Kaina; Zhang, Hua

2018-06-01

Microplastics and antibiotics are two classes of emerging contaminants with proposed negative impacts to aqueous ecosystems. Adsorption of antibiotics on microplastics may result in their long-range transport and may cause compound combination effects. In this study, we investigated the adsorption of 5 antibiotics [sulfadiazine (SDZ), amoxicillin (AMX), tetracycline (TC), ciprofloxacin (CIP), and trimethoprim (TMP)] on 5 types of microplastics [polyethylene (PE), polystyrene (PS), polypropylene (PP), polyamide (PA), and polyvinyl chloride (PVC)] in the freshwater and seawater systems. Scanning Electron Microscope (SEM) and X-ray diffractometer (XRD) analysis revealed that microplastics have different surface characterizes and various degrees of crystalline. Adsorption isotherms demonstrated that PA had the strongest adsorption capacity for antibiotics with distribution coefficient (K d ) values ranged from 7.36 ± 0.257 to 756 ± 48.0 L kg -1 in the freshwater system, which can be attributed to its porous structure and hydrogen bonding. Relatively low adsorption capacity was observed on other four microplastics. The adsorption amounts of 5 antibiotics on PS, PE, PP, and PVC decreased in the order of CIP > AMX > TMP > SDZ > TC with K f correlated positively with octanol-water partition coefficients (Log K ow ). Comparing to freshwater system, adsorption capacity in seawater decreased significantly and no adsorption was observed for CIP and AMX. Our results indicated that commonly observed polyamide particles can serve as a carrier of antibiotics in the aquatic environment. Copyright © 2018 Elsevier Ltd. All rights reserved.

Bone plate composed of a ternary nano-hydroxyapatite/polyamide 66/glass fiber composite: biomechanical properties and biocompatibility

PubMed Central

Qiao, Bo; Li, Jidong; Zhu, Qingmao; Guo, Shuquan; Qi, Xiaotong; Li, Weichao; Wu, Jun; Liu, Yang; Jiang, Dianming

2014-01-01

An ideal bone plate for internal fixation of bone fractures should have good biomechanical properties and biocompatibility. In this study, we prepared a new nondegradable bone plate composed of a ternary nano-hydroxyapatite/polyamide 66/glass fiber (n-HA/PA66/GF) composite. A breakage area on the n-HA/PA66/GF plate surface was characterized by scanning electron microscopy. Its mechanical properties were investigated using bone-plate constructs and biocompatibility was evaluated in vitro using bone marrow-derived mesenchymal stem cells. The results confirmed that adhesion between the n-HA/PA66 matrix and the glass fibers was strong, with only a few fibers pulled out at the site of breakage. Fractures fixed by the n-HA/PA66/GF plate showed lower stiffness and had satisfactory strength compared with rigid fixation using a titanium plate. Moreover, the results with regard to mesenchymal stem cell morphology, MTT assay, Alizarin Red S staining, enzyme-linked immunosorbent assay, and reverse transcription polymerase chain reaction for alkaline phosphatase and osteocalcin showed that the n-HA/PA66/GF composite was suitable for attachment and proliferation of mesenchymal stem cells, and did not have a negative influence on matrix mineralization or osteogenic differentiation of mesenchymal stem cells. These observations indicate that the n-HA/PA66/GF plate has good biomechanical properties and biocompatibility, and may be considered a new option for internal fixation in orthopedic surgery. PMID:24669191

Bone plate composed of a ternary nano-hydroxyapatite/polyamide 66/glass fiber composite: biomechanical properties and biocompatibility.

PubMed

Qiao, Bo; Li, Jidong; Zhu, Qingmao; Guo, Shuquan; Qi, Xiaotong; Li, Weichao; Wu, Jun; Liu, Yang; Jiang, Dianming

2014-01-01

An ideal bone plate for internal fixation of bone fractures should have good biomechanical properties and biocompatibility. In this study, we prepared a new nondegradable bone plate composed of a ternary nano-hydroxyapatite/polyamide 66/glass fiber (n-HA/PA66/GF) composite. A breakage area on the n-HA/PA66/GF plate surface was characterized by scanning electron microscopy. Its mechanical properties were investigated using bone-plate constructs and biocompatibility was evaluated in vitro using bone marrow-derived mesenchymal stem cells. The results confirmed that adhesion between the n-HA/PA66 matrix and the glass fibers was strong, with only a few fibers pulled out at the site of breakage. Fractures fixed by the n-HA/PA66/GF plate showed lower stiffness and had satisfactory strength compared with rigid fixation using a titanium plate. Moreover, the results with regard to mesenchymal stem cell morphology, MTT assay, Alizarin Red S staining, enzyme-linked immunosorbent assay, and reverse transcription polymerase chain reaction for alkaline phosphatase and osteocalcin showed that the n-HA/PA66/GF composite was suitable for attachment and proliferation of mesenchymal stem cells, and did not have a negative influence on matrix mineralization or osteogenic differentiation of mesenchymal stem cells. These observations indicate that the n-HA/PA66/GF plate has good biomechanical properties and biocompatibility, and may be considered a new option for internal fixation in orthopedic surgery.

Effect of denture cleansers on color stability, surface roughness, and hardness of different denture base resins

PubMed Central

Porwal, Anand; Khandelwal, Meenakshi; Punia, Vikas; Sharma, Vivek

2017-01-01

Aim: The purpose of this study was to evaluate the effect of different denture cleansers on the color stability, surface hardness, and roughness of different denture base resins. Materials and Methods: Three denture base resin materials (conventional heat cure resin, high impact resin, and polyamide denture base resin) were immersed for 180 days in commercially available two denture cleansers (sodium perborate and sodium hypochlorite). Color, surface roughness, and hardness were measured for each sample before and after immersion procedure. Statistical Analysis: One-way analysis of variance and Tukey's post hoc honestly significant difference test were used to evaluate color, surface roughness, and hardness data before and after immersion in denture cleanser (α =0.05). Results: All denture base resins tested exhibited a change in color, surface roughness, and hardness to some degree in both denture cleansers. Polyamides resin immersed in sodium perborate showed a maximum change in color after immersion for 180 days. Conventional heat cure resin immersed in sodium hypochlorite showed a maximum change in surface roughness and conventional heat cure immersed in sodium perborate showed a maximum change in hardness. Conclusion: Color changes of all denture base resins were within the clinically accepted range for color difference. Surface roughness change of conventional heat cure resin was not within the clinically accepted range of surface roughness. The choice of denture cleanser for different denture base resins should be based on the chemistry of resin and cleanser, denture cleanser concentration, and duration of immersion. PMID:28216847

Quantitative Detection of Small Molecule/DNA Complexes Employing a Force-Based and Label-Free DNA-Microarray

PubMed Central

Ho, Dominik; Dose, Christian; Albrecht, Christian H.; Severin, Philip; Falter, Katja; Dervan, Peter B.; Gaub, Hermann E.

2009-01-01

Force-based ligand detection is a promising method to characterize molecular complexes label-free at physiological conditions. Because conventional implementations of this technique, e.g., based on atomic force microscopy or optical traps, are low-throughput and require extremely sensitive and sophisticated equipment, this approach has to date found only limited application. We present a low-cost, chip-based assay, which combines high-throughput force-based detection of dsDNA·ligand interactions with the ease of fluorescence detection. Within the comparative unbinding force assay, many duplicates of a target DNA duplex are probed against a defined reference DNA duplex each. The fractions of broken target and reference DNA duplexes are determined via fluorescence. With this assay, we investigated the DNA binding behavior of artificial pyrrole-imidazole polyamides. These small compounds can be programmed to target specific dsDNA sequences and distinguish between D- and L-DNA. We found that titration with polyamides specific for a binding motif, which is present in the target DNA duplex and not in the reference DNA duplex, reliably resulted in a shift toward larger fractions of broken reference bonds. From the concentration dependence nanomolar to picomolar dissociation constants of dsDNA·ligand complexes were determined, agreeing well with prior quantitative DNAase footprinting experiments. This finding corroborates that the forced unbinding of dsDNA in presence of a ligand is a nonequilibrium process that produces a snapshot of the equilibrium distribution between dsDNA and dsDNA·ligand complexes. PMID:19486688

Fabrication and Characterization of Carbon Fiber-Reinforced Nano-Hydroxyapatite/Polyamide46 Biocomposite for Bone Substitute.

PubMed

Deng, Zhennan; Han, Hongjuan; Yang, Jingyuan; Li, Yuanyuan; Du, Shengnan; Ma, Jianfeng

2017-05-24

BACKGROUND Ideal bone repair material should be of good biocompatibility and high bioactivity. Besides, their mechanical properties should be equivalent to those of natural bone. The objective of this study was to fabricate a novel biocomposite suitable for load-bearing bone defect repair. MATERIAL AND METHODS A novel biocomposite composed of carbon fiber, hydroxyapatite and polyamide46 (CF/HA/PA46) was fabricated, and its mechanical performances and preliminary cell responses were evaluated to explore its feasibility for load-bearing bone defect repair. RESULTS The resultant CF/HA/PA46 biocomposite showed a bending strength of 159-223 MPa, a tensile strength of 127-199 MPa and a tensile modulus of 7.7-10.8 GPa, when the CF content was 5-20% (mass fraction) in biocomposite. The MG63 cells, showing an osteogenic phenotype, were well adhered and spread on the surface of the CF/HA/PA46 biocomposite. Moreover, the cells vitality and differentiation on the CF/HA/PA46 biocomposite surface were obviously increased during the culture time and there was no significant difference between the CF/HA/PA46 biocomposite and HA/PA (as control) at all the experimental time (P>0.05). CONCLUSIONS The addition of CF into HA/PA46 composite manifest improved the mechanical performances and showed favorable effects on biocompatibility of MG63 cells. The obtained biocomposite has high potential for bone repair in load-bearing sites.

Influence of Nanomaterial Compatibilization Strategies on Polyamide Nanocomposites Properties and Nanomaterial Release during the Use Phase.

PubMed

Fernández-Rosas, Elisabet; Vilar, Gemma; Janer, Gemma; González-Gálvez, David; Puntes, Victor; Jamier, Vincent; Aubouy, Laurent; Vázquez-Campos, Socorro

2016-03-01

The incorporation of small amounts of nanofillers in polymeric matrices has enabled new applications in several industrial sectors. The nanofiller dispersion can be improved by modifying the nanomaterial (NM) surface or predispersing the NMs to enhance compatibility. This study evaluates the effect of these compatibilization strategies on migration/release of the nanofiller and transformation of polyamide-6 (PA6), a thermoplastic polymer widely used in industry during simulated outdoors use. Two nanocomposites (NCs) containing SiO2 nanoparticles (NPs) with different surface properties and two multiwalled carbon nanotube (MWCNT) NCs obtained by different addition methods were produced and characterized, before and after accelerated wet aging conditions. Octyl-modified SiO2 NPs, though initially more aggregated than uncoated SiO2 NPs, reduced PA6 hydrolysis and, consequently, NM release. Although no clear differences in dispersion were observed between the two types of MWCNT NCs (masterbatch vs direct addition) after manufacture, the use of the MWCNT masterbatch reduced PA6 degradation during aging, preventing MWCNT accumulation on the surface and further release or potential exposure by direct contact. The amounts of NM released were lower for MWCNTs (36 and 108 mg/m(2)) than for SiO2 NPs (167 and 730 mg/m(2)), being lower in those samples where the NC was designed to improve the nanofiller-matrix interaction. Hence, this study shows that optimal compatibilization between NM and matrix can improve NC performance, reducing polymer degradation and exposure and/or release of the nanofiller.

Preparative isolation and purification of four flavonoids from the petals of Nelumbo nucifera by high-speed counter-current chromatography.

PubMed

Xingfeng, Guo; Daijie, Wang; Wenjuan, Duan; Jinhua, Du; Xiao, Wang

2010-01-01

Flavonoids, the primary constituents of the petals of Nelumbo nucifera, are known to have antioxidant properties and antibacterial bioactivities. However, efficient methods for the preparative isolation and purification of flavonoids from this plant are not currently available. To develop an efficient method for the preparative isolation and purification of flavonoids from the petals of N. nucifera by high-speed counter-current chromatography (HSCCC). Following an initial clean-up step on a polyamide column, HSCCC was utilised to separate and purify flavonoids. Purities and identities of the isolated compounds were established by HPLC-PAD, ESI-MS, (1)H-NMR and (13)C-NMR. The separation was performed using a two-phase solvent system composed of ethyl acetate-methanol-water-acetic acid (4 : 1 : 5 : 0.1, by volume), in which the upper phase was used as the stationary phase and the lower phase was used as the mobile phase at a flow-rate of 1.0 mL/min in the head-to-tail elution mode. Ultimately, 5.0 mg syringetin-3-O-beta-d-glucoside, 6.5 mg quercetin-3-O-beta-d-glucoside, 12.8 mg isorhamnetin-3-O-beta-d-glucoside and 32.5 mg kaempferol-3-O-beta-d-glucoside were obtained from 125 mg crude sample. The combination of HSCCC with a polyamide column is an efficient method for the preparative separation and purification of flavonoids from the petals of N. nucifera. (c) 2009 John Wiley & Sons, Ltd.

Fabrication and Characterization of Carbon Fiber-Reinforced Nano-Hydroxyapatite/Polyamide46 Biocomposite for Bone Substitute

PubMed Central

Deng, Zhennan; Han, Hongjuan; Yang, Jingyuan; Li, Yuanyuan; Du, Shengnan; Ma, Jianfeng

2017-01-01

Background Ideal bone repair material should be of good biocompatibility and high bioactivity. Besides, their mechanical properties should be equivalent to those of natural bone. The objective of this study was to fabricate a novel biocomposite suitable for load-bearing bone defect repair. Material/Methods A novel biocomposite composed of carbon fiber, hydroxyapatite and polyamide46 (CF/HA/PA46) was fabricated, and its mechanical performances and preliminary cell responses were evaluated to explore its feasibility for load-bearing bone defect repair. Results The resultant CF/HA/PA46 biocomposite showed a bending strength of 159–223 MPa, a tensile strength of 127–199 MPa and a tensile modulus of 7.7–10.8 GPa, when the CF content was 5–20% (mass fraction) in biocomposite. The MG63 cells, showing an osteogenic phenotype, were well adhered and spread on the surface of the CF/HA/PA46 biocomposite. Moreover, the cells vitality and differentiation on the CF/HA/PA46 biocomposite surface were obviously increased during the culture time and there was no significant difference between the CF/HA/PA46 biocomposite and HA/PA (as control) at all the experimental time (P>0.05). Conclusions The addition of CF into HA/PA46 composite manifest improved the mechanical performances and showed favorable effects on biocompatibility of MG63 cells. The obtained biocomposite has high potential for bone repair in load-bearing sites. PMID:28536416

Effects of thermal cycling on surface roughness, hardness and flexural strength of polymethylmethacrylate and polyamide denture base resins.

PubMed

Ayaz, Elif Aydoğan; Bağış, Bora; Turgut, Sedanur

2015-10-16

The purpose of this study was to evaluate the effects of thermal cycling on the surface roughness, hardness and flexural strength of denture resins. Polyamide (PA; Deflex and Valplast) and polymethylmethacrylate (PMMA; QC-20 and Acron MC) denture materials were selected. A total of 180 specimens were fabricated and then divided into 3 groups. The first group (group 1) acted as a control and was not thermocycled. The second group (group 2) was subjected to thermocycling for 10,000 cycles in artificial saliva and 5,000 cycles in distilled water. The last group (group 3) was thermocycled for 20,000 cycles in artificial saliva and 10,000 cycles in distilled water. The surface roughness were measured with a profilometer. The hardness of the resins were measured with a Vickers Hardness Tester using a 100-gf load. The flexural strength test was performed using the universal test machine with a crosshead speed of 5 mm/min. Data were analyzed using statistical software. The results of the measurements in the 3 different tests were analyzed by Kruskal-Wallis test with Bonferroni correction. Multiple comparisons were made by Conover and Wilcoxon tests. There was a significant difference between the PMMA and PA groups in terms of surface roughness, hardness and transverse strength before and after thermal cycling (p<0.001). Thermal cycling did not change the surface roughness, hardness and flexural strength values of either the PMMA or PA group (p>0.001).

Tribological properties of nanosized calcium carbonate filled polyamide 66 nanocomposites

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

Itagaki, Kaito; Nishitani, Yosuke; Kitano, Takeshi

For the purpose of developing high performance tribomaterials for mechanical sliding parts such as gears, bearings and so on, nanosized calcium carbonate (nano-CaCO{sub 3}) filled polyamide 66 (PA66) nanocomposites were investigated. The nano-CaCO{sub 3} was a kind of precipitated (colloid typed) CaCO{sub 3}, and its average particle size was 40, 80 and 150 nm. Surface treatment was performed by fatty acid on the nano-CaCO{sub 3} and its volume fraction in the nanocomposite was varied from 1 to 20vol.%. These nanocomposites were melt-mixed by a twin screw extruder and injection-molded. Tribological properties were measured by two types of sliding wear testers suchmore » as ring-on-plate type and ball-on-plate type one under dry condition. The counterface, worn surface and wear debris were observed by digital microscope and scanning electron microscope. It was found that the nano-CaCO{sub 3} has a good effect on the tribological properties, although the effect on the frictional coefficient and specific wear rate is differed by the volume fraction and the type of sliding wear modes. This is attributed to the change of wear mechanisms, which is the change of form of the transfer films on the counterface and the size of wear debris. It follows from these results that PA66/nano-CaCO{sub 3} nanocomposites may be possible to be the high performance tribomaterials.« less

Electromechanical properties of polyamide/lycra fabric treated with PEDOT:PSS

NASA Astrophysics Data System (ADS)

Tadesse, M. G.; Mengistie, D. A.; Loghin, C.; Chen, Y.; Wang, L.; Catalin, D.; Müller, C.; Nierstrasz, V.

2017-10-01

One of the challenges in smart textiles is to develop suitable multifunctional materials that can address simultaneously several characteristics such as durability, stretchability, lightweight, and conductivity. Conductive polymers which showed success in different technological fields like polymer solar cells and light emitting diodes are promising in many smart textile applications. In this work, we treated a common polyamide/lycra knitted fabric with PEDOT:PSS for stretchable e-textiles. PEDOT:PSS, with DMSO as a conductivity enhancer and different ratios of water-based polyurethane dispersions as a binder, was applied to the fabric with simple immersion and coating applications. The effect of different application methods and binder ratio on the surface resistance of the fabric was monitored with four point probe electrical surface resistance measurement systems. Samples prepared by immersion technique are more uniform and have higher conductivity than those prepared by a coating technique. SEM images showed that PEDOT:PSS is incorporated into the structure in the immersion method while in the coating it is majorly present on the surface of the fabric. The tensile measurement showed that the acidic PEDOT:PSS and polyurethane dispersion coating has no adverse effect on the tensile strength of the fabric. The coated samples can be stretched up to 700% while still reasonably conductive. The resistance increases only by a small amount when samples were stretched cyclically by stretching 100%. Generally, samples prepared by the immersion method maintained better conductivity while stretching than those by a coating method. The washing fastness of the samples was also assessed.

Time dependent voiding mechanisms in polyamide 6 submitted to high stress triaxiality: experimental characterisation and finite element modelling

NASA Astrophysics Data System (ADS)

Selles, Nathan; King, Andrew; Proudhon, Henry; Saintier, Nicolas; Laiarinandrasana, Lucien

2017-08-01

Double notched round bars made of semi-crystalline polymer polyamide 6 (PA6) were submitted to monotonic tensile and creep tests. The two notches had a root radius of 0.45 mm, which imposes a multiaxial stress state and a state of high triaxiality in the net (minimal) section of the specimens. Tests were carried out until the failure occurred from one of the notches. The other one, unbroken but deformed under steady strain rate or steady load, was inspected using the Synchrotron Radiation Computed Tomography (SRCT) technique. These 3D through thickness inspections allowed the study of microstructural evolution at the peak stress for the monotonic tensile test and at the beginning of the tertiary creep for the creep tests. Cavitation features were assessed with a micrometre resolution within the notched region. Spatial distributions of void volume fraction ( Vf) and void morphology were studied. Voiding mechanisms were similar under steady strain rates and steady loads. The maximum values of Vf were located between the axis of revolution of the specimens and the notch surface and voids were considered as flat cylinders with a circular basis perpendicular to the loading direction. A model, based on porous plasticity, was used to simulate the mechanical response of this PA6 material under high stress triaxiality. Both macroscopic behaviour (loading curves) and voiding micro-mechanisms (radial distributions of void volume fraction) were accurately predicted using finite element simulations.

Preparation of Polyamide-6 Submicrometer-Sized Spheres by In Situ Polymerization.

PubMed

Zhao, Xingke; Xia, Housheng; Fu, Xubing; Duan, Jianping; Yang, Guisheng

2015-11-01

Polyamide-6 (PA6) submicron-sized spheres are prepared by two steps: (1) anionic ring-opening polymerization of ε-caprolactam in the presence of poly(ethylene glycol)-block-poly-(propylene glycol)-block-poly(ethylene glycol)(PEG-b-PPG-b-PEG) and (2) separation of PA6 spheres by dissolving PEG-b-PPG-b-PEG from the prepared blends. The PA6 microspheres obtained are regular spherical, with diameter ranging from 200 nm to 2 μm and narrow size distribution, as confirmed by scanning electron microscopy. By comparison with PA6/PS and PA6/PEG systems, it is denominated that the PEG blocks in PEG-b-PPG-b-PEG can effectively reduce the surface tension of PA6 droplets and further decrease the diameter of the PA6 microspheres. The PPG block in PEG-b-PPG-b-PEG can prevent the PA6 droplets coalescing with each other, and isolated spherical particles can be obtained finally. The phase inversion of the PA6/PEG-b-PPG-b-PEG blends occurs at very low PEG-b-PPG-b-PEG content; the PEG-b-PPG-b-PEG phase can be removed by water easily. The whole experiment can be finished in a short time (approximately in half an hour) without using any organic solvents; it is an efficient strategy for the preparation of submicron-sized PA6 microspheres. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Double dielectric barrier (DBD) plasma-assisted deposition of chemical stabilized nanoparticles on polyamide 6,6 and polyester fabrics

NASA Astrophysics Data System (ADS)

Ribeiro, A. I.; Modic, M.; Cvelbar, U.; Dinescu, G.; Mitu, B.; Nikiforov, A.; Leys, C.; Kuchakova, I.; Vanneste, M.; Heyse, P.; De Vrieze, M.; Carneiro, N.; Souto, A. P.; Zille, A.

2017-10-01

The development of new multifunctional textiles containing nanoparticles (NPs) has a special interest in several applications for pharmaceutical and medical products. Cu, Zn and Ag are the most promising antimicrobial NPs, exhibiting strong antibacterial activities. However, most of antimicrobial textiles coated with NPs are not able to perform a controlled release of NPs because of the high degree of aggregation. The aim of this study is to assess the effect of NPs stabilizers such as citrate, alginate and polyvinyl alcohol (PVA) in Cu, Zn and Ag NPs dispersions. The obtained dispersions were used to develop a new class of antibacterial NPs coatings onto polyamide 6,6 (PA66) and polyester fabrics (PES) by Double Dielectric Barrier (DBD) plasma discharge. Dynamic light scattering (DLS) was used to evaluate the best dispersing agent in terms of size, polydispersity index and zeta potential. Coating efficiency was evaluated by SEM, XPS and FTIR. The washing fastness of the coatings developed was also tested. The results show that the best dispersions were obtained using 2.5% of citrate for ZnO, 5% Alginate for Cu and 2.5% alginate for Ag NPs. SEM, XPS and FTIR analysis shows that DBD is an efficient deposition technique only for Ag and Cu NPs and that better perform in PA66 than PES fabric. The DBD deposition in air display similar results in term of NPS deposition of usually more efficient plasma jets using carrier gas such as N2 and Ar.

Molecular recognition of DNA base pairs by the formamido/pyrrole and formamido/imidazole pairings in stacked polyamides.

PubMed

Buchmueller, Karen L; Staples, Andrew M; Uthe, Peter B; Howard, Cameron M; Pacheco, Kimberly A O; Cox, Kari K; Henry, James A; Bailey, Suzanna L; Horick, Sarah M; Nguyen, Binh; Wilson, W David; Lee, Moses

2005-01-01

Polyamides containing an N-terminal formamido (f) group bind to the minor groove of DNA as staggered, antiparallel dimers in a sequence-specific manner. The formamido group increases the affinity and binding site size, and it promotes the molecules to stack in a staggered fashion thereby pairing itself with either a pyrrole (Py) or an imidazole (Im). There has not been a systematic study on the DNA recognition properties of the f/Py and f/Im terminal pairings. These pairings were analyzed here in the context of f-ImPyPy, f-ImPyIm, f-PyPyPy and f-PyPyIm, which contain the central pairing modes, -ImPy- and -PyPy-. The specificity of these triamides towards symmetrical recognition sites allowed for the f/Py and f/Im terminal pairings to be directly compared by SPR, CD and DeltaT (M) experiments. The f/Py pairing, when placed next to the -ImPy- or -PyPy- central pairings, prefers A/T and T/A base pairs to G/C base pairs, suggesting that f/Py has similar DNA recognition specificity to Py/Py. With -ImPy- central pairings, f/Im prefers C/G base pairs (>10 times) to the other Watson-Crick base pairs; therefore, f/Im behaves like the Py/Im pair. However, the f/Im pairing is not selective for the C/G base pair when placed next to the -PyPy- central pairings.

Effect of polyamide 6 on the morphology and electrical conductivity of carbon black-filled polypropylene composites

PubMed Central

Zhang, Xuewei; Liu, Jiang; Wang, Yi

2017-01-01

Carbon black (CB)-filled polypropylene (PP) with surface resistivity between 106 and 109 Ω sq−1 is the ideal antistatic plastic material in the electronics and electric industry. However, a large amount of CB may have an adverse effect on the mechanical properties and processing performance of the material, thus an improved ternary system is developed. Blends of CB-filled PP and polyamide 6 (PA6) have been prepared by melt blending in order to obtain electrically conductive polymer composites with a low electrical percolation threshold based on the concept of double percolation. The morphological developments of these composites were studied by scanning electron microscopy. The results showed that CB particles were selectively dispersed in PA6 phases due to the good interaction and interfacial adhesion between CB and PA6. At the same CB loadings, the surface resistivity of PP/PA6/CB composite was smaller than that of PP/CB composite system, which indicated the better conductivity in the former composite. The increasing amount of PA6 in the composites changed the morphology from a typical sea–island morphology to a co-continuous morphology. What is more, with 8 wt% of CB and PP/PA6 phase ratio of 70/30 in which the PP and PA6 phases formed a co-continuous structure, the electrical conductivity of the composite peaked at 2.01 × 105 Ω sq−1. PMID:29308223

3D-printing of undisturbed soil imaged by X-ray

NASA Astrophysics Data System (ADS)

Bacher, Matthias; Koestel, John; Schwen, Andreas

2014-05-01

The unique pore structures in Soils are altered easily by water flow. Each sample has a different morphology and the results of repetitions vary as well. Soil macropores in 3D-printed durable material avoid erosion and have a known morphology. Therefore potential and limitations of reproducing an undisturbed soil sample by 3D-printing was evaluated. We scanned an undisturbed soil column of Ultuna clay soil with a diameter of 7 cm by micro X-ray computer tomography at a resolution of 51 micron. A subsample cube of 2.03 cm length with connected macropores was cut out from this 3D-image and printed in five different materials by a 3D-printing service provider. The materials were ABS, Alumide, High Detail Resin, Polyamide and Prime Grey. The five print-outs of the subsample were tested on their hydraulic conductivity by using the falling head method. The hydrophobicity was tested by an adapted sessile drop method. To determine the morphology of the print-outs and compare it to the real soil also the print-outs were scanned by X-ray. The images were analysed with the open source program ImageJ. The five 3D-image print-outs copied from the subsample of the soil column were compared by means of their macropore network connectivity, porosity, surface volume, tortuosity and skeleton. The comparison of pore morphology between the real soil and the print-outs showed that Polyamide reproduced the soil macropore structure best while Alumide print-out was the least detailed. Only the largest macropore was represented in all five print-outs. Printing residual material or printing aid material remained in and clogged the pores of all print-out materials apart from Prime Grey. Therefore infiltration was blocked in these print-outs and the materials are not suitable even though the 3D-printed pore shapes were well reproduced. All of the investigated materials were insoluble. The sessile drop method showed angles between 53 and 85 degrees. Prime Grey had the fastest flow rate; the other conducting materials had slow or non-reproducible flow rates. Since only Prime Grey was able to print-out the largest macropore in a discontinuous way, the morphological differences between the five print-outs were not evaluated. Each material has its limitations but only Prime Greys morphology was sufficiently printed and no clogging with residual material occurred. Polyamide and High Detail Resin had clogged pores but were matching the soil's macropore morphology better but further research on removal of residual material blocking pores is needed before they are useable.

Acoustic emission analysis: A test method for metal joints bonded by adhesives

NASA Technical Reports Server (NTRS)

Brockmann, W.; Fischer, T.

1978-01-01

Acoustic emission analysis is applied to study adhesive joints which had been subjected to mechanical and climatic stresses, taking into account conditions which make results applicable to adhesive joints used in aerospace technology. Specimens consisting of the alloy AlMgSi0.5 were used together with a phenolic resin adhesive, an epoxy resin modified with a polyamide, and an epoxy resin modified with a nitrile. Results show that the acoustic emission analysis provides valuable information concerning the behavior of adhesive joints under load and climatic stresses.

Extraction of organic acids by ion-pair formation with tri-n-octylamine. Part 7. Comparison of methods for extraction of synthetic dyes from yogurt.

PubMed

Puttemans, M L; de Voogt, M; Dryon, L; Massart, D

1985-01-01

Synthetic dyes were extracted from yogurt by different methods, but all methods had in common a liberation of dyes from the food followed by ion-pair formation with tri-n-octylamine. Extraction with pH 5.5 phosphate buffer gave high recoveries for 5 of the 7 dyes investigated and was relatively fast. Precipitation of proteins followed by polyamide adsorption and desorption gave high yields for all the dyes but was tedious and long.

Fire Management/Suppression Systems/Concepts Relating to Aircraft Cabin Fire Safety.

DTIC Science & Technology

1982-07-01

polyamide- cm; cell size, cm; paper honeycomb; paper honeycomb; density, kg/cm 3 ; filler 2.413;0.31; 48.06; 2.413;0.31; 48.06; no core filler no core...0 4’ 14 ~ 1 4 44 N4 El4 (36M -11 - 0 0 N4 8A 0o N. 0 04 0n 0m C,0 0 44 . . 000040 -t 0 0 880 -8 ,0 04 0 C, 0 C4 4-0 OD -CD0C, m. g G - C4 A - 40 a

Development of flame resistant treatment for nomex fibrous structures

NASA Technical Reports Server (NTRS)

Toy, M. S.

1978-01-01

Technology which renders aramid fibrous structures flame resistant through chemical modification was developed. The project scaled up flame resistant treatment from laboratory fabric swatches of a few inches to efficiently producing ten yards of commercial width (41 inches) aromatic polyamide. The radiation intensity problem of the processor was resolved. Further improvement of the processor cooling system was recommended for two reasons: (1) To advance current technology of flame proofing Nomex fabric to higher oxygen enriched atmospheres; and (2) To adapt the processor for direct applicability to low cost commercial fabrics.

Gas separation membranes

DOEpatents

Schell, William J.

1979-01-01

A dry, fabric supported, polymeric gas separation membrane, such as cellulose acetate, is prepared by casting a solution of the polymer onto a shrinkable fabric preferably formed of synthetic polymers such as polyester or polyamide filaments before washing, stretching or calendering (so called griege goods). The supported membrane is then subjected to gelling, annealing, and drying by solvent exchange. During the processing steps, both the fabric support and the membrane shrink a preselected, controlled amount which prevents curling, wrinkling or cracking of the membrane in flat form or when spirally wound into a gas separation element.

Tribological properties of epoxy composite materials for marine and river transport

NASA Astrophysics Data System (ADS)

Buketov, A. V.; Maruschak, P. O.; Brailo, N. V.; Akimov, A. V.; Kobelnik, O. S.; Panin, S. V.

2016-11-01

Tribological properties of epoxy composites filled with thermoplastics and dispersed particles under sea water environment were analyzed. It has been revealed that the composition, sliding friction conditions, as well as the marine environment, substantially affect the tribological properties of the materials. The improvement of tribological properties of epoxycomposite thermosetting plastics after their filling with thermoplastic polyamide PA-6 granules under friction in sea water environment has been proved. The recommendations on applying the developed material in friction parts for marine and river transport were formulated.

Development of Carbon Nanotube-Polyamide Nanocomposite-based Stir Bar Sorptive Extraction Coupled to HPLC-UV Applying Response Surface Methodology for the Analysis of Bisphenol A in Aqueous Samples.

PubMed

Ayazi, Z; Matin, A A

2016-11-01

A novel nanocomposite based on reinforcing of multiwalled carbon nanotubes in polyamide (PA) was prepared by solvent exchange method as stir bar coating. The morphology and surface characteristic of PA and CNT/PA coated stir bars were investigated using scanning electron microscopy. The stir bar coated by CNT/PA nanocomposite was used as an extraction device for stir bar sorptive extraction of bisphenol A from aqueous samples followed by high performance liquid chromatography-UV detection. The effect of CNTs doping level and oxidation of CNTs on the extraction capability of the coating was investigated. Response surface methodology applying central composite design was used for modeling and optimization of important factors influencing the extraction and desorption processes including extraction time, salt and methanol content, desorption solvent, its volume and desorption time. Limit of detection and linear dynamic range of the method were 0.3 ng mL -1 and 1-10 ng mL -1 , respectively. The method precision (RSD%) with four replicate determinations was 4.9% for distilled water at the concentration level of 10 ng mL -1 The obtained RSD% for reproducibility of stir bars was 7.4%. The developed method was successfully applied to the bottled mineral water samples, while the relative recoveries (RR%) were obtained to be in the range of 92.0-101.9%. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Corona plasma modification of polyamide 66 for the design of textile delivery systems for cosmetic therapy

NASA Astrophysics Data System (ADS)

Labay, C.; Canal, J. M.; Navarro, A.; Canal, C.

2014-10-01

Cosmetic and medical applications of technical textiles are a research expanding field. One of the added values of these new materials would be that they are suitable to contain and release active ingredients in a controlled manner. The influence of the initial state of the surface of polyamide 6.6 (PA66) fibers on the wetting properties of the fibers as well as on the incorporation of caffeine on the fibers and on its release kinetics from the fibers has been investigated. Comparison between industrially-finished PA66 fabrics and laboratory washed fabrics has been done to carry out this study. Furthermore, surface modification of the PA66 fibers by low temperature plasma has been studied regarding the modification of the physical, chemical and topographical properties of the textile fibers. Corona plasma treatment has been investigated to achieve surface modification in the first nanometers of polymer fibers surface in order to modulate the incorporation and the release of caffeine. It has been demonstrated that both initial state of the PA66 surface and prior plasma treatment of the PA66 fibers before the active principle incorporation condition caffeine release kinetics from the textile fibers. The final release percentage increases linearly with the C-O and Cdbnd O functional groups incorporated by plasma on the surface. It has also been established that the release amounts of caffeine achieved after 8 h from the PA66 fabric are in the same order of magnitude than topical doses of commercial gel-based formulations.

Effects of hypochlorous acid exposure on the rejection of salt, polyethylene glycols, boron and arsenic(V) by nanofiltration and reverse osmosis membranes.

PubMed

Do, Van Thanh; Tang, Chuyang Y; Reinhard, Martin; Leckie, James O

2012-10-15

The separation layer of polyamide-based (PA) thin film composite (TFC) membranes can be modified by active chlorine species. The PA-TFC membranes, NF90, BW30 and NF270, were exposed to different concentrations of sodium hypochlorite (NaOCl) at pH 5 for 24 h. Elemental composition obtained from X-ray Photoelectron Spectroscopy (XPS) showed that the chlorine content in the PA layer increased with the chlorine concentrations. Treatment of membranes with 10 ppm Cl increased the membrane hydrophilicity. By contrast, when treated with 1000 ppm Cl or more, the membranes became less hydrophilic. Water permeability values for all 3 membrane types declined with increased chlorine concentrations. Filtration of polyethylene glycols (PEGs) with molecular weights of 200, 400 and 600 Daltons (Da) was performed to investigate the influence of chlorine treatment on membrane molecular weight cut off (MWCO) and rejection by size exclusion. Treatment with 10 and 100 ppm Cl lowered the MWCO while treatment with higher concentrations increased the MWCO. All chlorinated membranes experienced higher NaCl rejection compared to virgin ones. The performance of NF90 was tested with respect to the rejection of inorganic contaminants including boron (H(3)BO(3)) and arsenic (H(2)AsO(4)(-)). The boron rejection results paralleled PEG rejection whereas those for arsenic followed NaCl rejection patterns. The changes in membrane performance due to chlorine treatment were explained in terms of competing mechanisms: membrane tightening, bond cleavage by N-chlorination and chlorination promoted polyamide hydrolysis. Copyright © 2012 Elsevier Ltd. All rights reserved.

Rheological changes of polyamide 12 under oscillatory shear

NASA Astrophysics Data System (ADS)

Mielicki, C.; Gronhoff, B.; Wortberg, J.

2014-05-01

Changes in material properties as well as process deviation prevent Laser Sintering (LS) technology from manufacturing of quality assured parts in a series production. In this context, the viscosity of Polyamide 12 (PA12) is assumed to possess the most significant influence, as it determines the sintering velocity, the resistance towards melt formation and the bonding strength of sintered layers. Moreover, the viscosity is directly related to the structure of the molten polymer. In particular, it has been recently reported that LS process conditions lead to structural changes of PA12 affecting viscosity and coalescence of adjacent polymer particles, i.e. melt formation significantly. Structural change of PA12 was understood as a post condensation. Its influence on viscosity was described by a time and temperature depending rheological model whereas time dependence was considered by a novel structural change shift factor which was derived from melt volume rate data. In combination with process data that was recorded using online thermal imaging, the model is suitable to control the viscosity (processability of the material) as result of material and process properties. However, as soon as laser energy is exposed to the powder bed PA12 undergoes a phase transition from solid to molten state. Above the melting point, structural change is expected to occur faster due to a higher kinetic energy and free volume of the molten polymer. Oscillatory shear results were used to study the influence of aging time and for validation of the novel structural change shift factor and its model parameters which were calibrated based on LS processing condition.

Reduction-Degradable Polymeric Micelles Decorated with PArg for Improving Anticancer Drug Delivery Efficacy.

PubMed

Cui, Yani; Sui, Junhui; He, Mengmeng; Xu, Zhiyi; Sun, Yong; Liang, Jie; Fan, Yujiang; Zhang, Xingdong

2016-01-27

In this study, five kinds of reduction-degradable polyamide amine-g-polyethylene glycol/polyarginine (PAA-g-PEG/PArg) micelles with different proportions of hydrophilic and hydrophobic segments were synthesized as novel drug delivery vehicles. Polyarginine not only acted as a hydrophilic segment but also possessed a cell-penetrating function to carry out a rapid transduction into target cells. Polyamide amine-g-polyethylene glycol (PAA-g-PEG) was prepared for comparison. The characterization and antitumor effect of the DOX-incorporated PAA-g-PEG/PArg cationic polymeric micelles were investigated in vitro and in vivo. The cytotoxicity experiments demonstrated that the PAA-g-PEG/PArg micelles have good biocompatibility. Compared with DOX-incorporated PAA-g-PEG micelles, the DOX-incorporated PAA-g-PEG/PArg micelles were more efficiently internalized into human hepatocellular carcinoma (HepG2) cells and more rapidly released DOX into the cytoplasm to inhibit cell proliferation. In the 4T1-bearing nude mouse tumor models, the DOX-incorporated PAA-g-PEG/PArg micelles could efficiently accumulate in the tumor site and had a longer accumulation time and more significant aggregation concentration than those of PAA-g-PEG micelles. Meanwhile, it excellently inhibited the solid tumor growth and extended the survival period of the tumor-bearing Balb/c mice. These results could be attributed to their appropriate nanosize and the cell-penetrating peculiarity of polyarginine as a surface layer. The PAA-g-PEG/PArg polymeric micelles as a safe and high efficiency drug delivery system were expected to be a promising delivery carrier that targeted hydrophobic chemotherapy drugs to tumors and significantly enhanced antitumor effects.

Spray- and spin-assisted layer-by-layer assembly of copper nanoparticles on thin-film composite reverse osmosis membrane for biofouling mitigation.

PubMed

Ma, Wen; Soroush, Adel; Van Anh Luong, Tran; Brennan, Gregory; Rahaman, Md Saifur; Asadishad, Bahareh; Tufenkji, Nathalie

2016-08-01

Copper nanoparticles (CuNPs) have long been considered as highly effective biocides; however, the lack of suitable methods for loading CuNPs onto polymeric membranes is recognized as being one of the primary reasons for the limited research concerning their application in membrane industries. A highly efficient spray- and spin-assisted layer-by-layer (SSLbL) method was developed to functionalize the TFC polyamide RO membranes with controllable loading of CuNPs for biofouling control. The SSLbL method was able to produce a uniform bilayer of polyethyleneimine-coated CuNPs and poly(acrylic) acid in less than 1 min, which is far more efficient than the traditional dipping approach (25-60 min). The successful loading of CuNPs onto the membrane surface was confirmed by XPS analysis. Increasing the number of bilayers from 2 to 10 led to an increased quantity of CuNPs on the membrane surface, from 1.75 to 23.7 μg cm(-2). Multi-layer coating exhibited minor impact on the membrane water permeation flux (13.3% reduction) while retaining the original salt rejection ability. Both static bacterial inactivation and cross-flow filtration tests demonstrated that CuNPs could significantly improve anti-biofouling property of a polyamide membrane and effectively inhibit the permeate flux reduction caused by bacterial deposition on the membrane surface. Once depleted, CuNPs can also be potentially regenerated on the membrane surface via the same SSLbL method. Copyright © 2016 Elsevier Ltd. All rights reserved.

Integration of a Spectral Domain Optical Coherence Tomography System into a Surgical Microscope for Intraoperative Imaging

PubMed Central

Ehlers, Justis P.; Tao, Yuankai K.; Farsiu, Sina; Maldonado, Ramiro; Izatt, Joseph A.

2011-01-01

Purpose. To demonstrate an operating microscope-mounted spectral domain optical coherence tomography (MMOCT) system for human retinal and model surgery imaging. Methods. A prototype MMOCT system was developed to interface directly with an ophthalmic surgical microscope, to allow SDOCT imaging during surgical viewing. Nonoperative MMOCT imaging was performed in an Institutional Review Board–approved protocol in four healthy volunteers. The effect of surgical instrument materials on MMOCT imaging was evaluated while performing retinal surface, intraretinal, and subretinal maneuvers in cadaveric porcine eyes. The instruments included forceps, metallic and polyamide subretinal needles, and soft silicone-tipped instruments, with and without diamond dusting. Results. High-resolution images of the human retina were successfully obtained with the MMOCT system. The optical properties of surgical instruments affected the visualization of the instrument and the underlying retina. Metallic instruments (e.g., forceps and needles) showed high reflectivity with total shadowing below the instrument. Polyamide material had a moderate reflectivity with subtotal shadowing. Silicone instrumentation showed moderate reflectivity with minimal shadowing. Summed voxel projection MMOCT images provided clear visualization of the instruments, whereas the B-scans from the volume revealed details of the interactions between the tissues and the instrumentation (e.g., subretinal space cannulation, retinal elevation, or retinal holes). Conclusions. High-quality retinal imaging is feasible with an MMOCT system. Intraoperative imaging with model eyes provides high-resolution depth information including visualization of the instrument and intraoperative tissue manipulation. This study demonstrates a key component of an interactive platform that could provide enhanced information for the vitreoretinal surgeon. PMID:21282565

Rheology at the Interface and the Role of the Interphase in Reactive Functionalized Multilayer Polymers in Coextrusion Process

NASA Astrophysics Data System (ADS)

Lamnawar, Khalid; Maazouz, Abderrahim

2008-07-01

Coextrusion technologies are commonly used to produce multilayered composite sheets or films for a large range of applications from food packaging to optics. The contrast of rheological properties between layers can lead to interfacial instabilities during flow. Important theoretical and experimental advances regarding the stability of compatible and incompatible polymers have, during the last decades, been made using a mechanical approach. However, few research efforts have been dedicated to the physicochemical affinity between the neighboring layers. The present study deals with the influence of this affinity on interfacial instabilities for functionalized incompatible polymers. Polyamide (PA6)/polyethylene grafted with glycidyl methacrylate (PE-GMA) was used as a reactive system and PE/PA6 as a non reactive one. Two grades of polyamide (PA6) were used in order to change the viscosity and elasticity ratios between PE (or PE-GMA) and PA6. It was experimentally confirmed, in this case, that weak disturbance can be predicted by considering an interphase of non-zero thickness (corresponding to an interdiffusion/reaction zone) instead of a purely geometrical interface between the two reactive layers. According to the rheological investigations from previous work which the interphase effect can be probed, an experimental strategy was here formulated to optimize the process by listing the parameters that controlled the stability of the reactive multilayer flows. Hence, based on this analysis, guidelines for a stable coextrusion of reactive functionalized polymers can be provided coupling the classical parameters (viscosity, elasticity and layer ratios) and the physicochemical affinity at the polymer/polymer interface.

Integration of a spectral domain optical coherence tomography system into a surgical microscope for intraoperative imaging.

PubMed

Ehlers, Justis P; Tao, Yuankai K; Farsiu, Sina; Maldonado, Ramiro; Izatt, Joseph A; Toth, Cynthia A

2011-05-16

To demonstrate an operating microscope-mounted spectral domain optical coherence tomography (MMOCT) system for human retinal and model surgery imaging. A prototype MMOCT system was developed to interface directly with an ophthalmic surgical microscope, to allow SDOCT imaging during surgical viewing. Nonoperative MMOCT imaging was performed in an Institutional Review Board-approved protocol in four healthy volunteers. The effect of surgical instrument materials on MMOCT imaging was evaluated while performing retinal surface, intraretinal, and subretinal maneuvers in cadaveric porcine eyes. The instruments included forceps, metallic and polyamide subretinal needles, and soft silicone-tipped instruments, with and without diamond dusting. High-resolution images of the human retina were successfully obtained with the MMOCT system. The optical properties of surgical instruments affected the visualization of the instrument and the underlying retina. Metallic instruments (e.g., forceps and needles) showed high reflectivity with total shadowing below the instrument. Polyamide material had a moderate reflectivity with subtotal shadowing. Silicone instrumentation showed moderate reflectivity with minimal shadowing. Summed voxel projection MMOCT images provided clear visualization of the instruments, whereas the B-scans from the volume revealed details of the interactions between the tissues and the instrumentation (e.g., subretinal space cannulation, retinal elevation, or retinal holes). High-quality retinal imaging is feasible with an MMOCT system. Intraoperative imaging with model eyes provides high-resolution depth information including visualization of the instrument and intraoperative tissue manipulation. This study demonstrates a key component of an interactive platform that could provide enhanced information for the vitreoretinal surgeon.

Surface modification of polyamide reverse osmosis membrane with organic-inorganic hybrid material for antifouling

NASA Astrophysics Data System (ADS)

Zhang, Yang; Wan, Ying; Pan, Guoyuan; Yan, Hao; Yao, Xuerong; Shi, Hongwei; Tang, Yujing; Wei, Xiangrong; Liu, Yiqun

2018-03-01

A series of thin-film composite reverse osmosis membranes based on polyamide have been modified by coating the polyvinyl alcohol and 3-mercaptopropyltriethoxysilane aqueous solution prepared by a sol-gel process on the membrane surface, followed by thermal crosslinking treatment. In order to improve the hydrophilicity of the modified TFC membranes, the membranes were then immersed into H2O2 aqueous solution to convert -SH into -SO3H. The resulting TFC membranes were characterized by SEM, AFM, ATR-FTIR, streaming potential, XPS as well as static contact angle. After surface modification with the organic-inorganic hybrid material, the TFC membranes show increased NaCl rejection and decreased water flux with increasing 3-mercaptopropyltrimethoxysilane content in coating solution. The optimal modification membrane (PA-SMPTES-0.8) exhibits a NaCl rejection of 99.29%, higher than that (97.20%) of the virgin PA membrane, and a comparable water flux to virgin PA membrane (41.7 L/m2 h vs 47.9 L/m2 h). More importantly, PA-SMPTES-0.8 membrane shows much more improved fouling resistance to BSA than virgin PA and PVA modified PA (PA-PVA-1.0) membranes. PA-SMPTES-0.8 membrane loses about 13% of the initial flux after BSA fouling for 12 h, which is lower than that of virgin PA and PA-PVA-1.0 membranes (42% and 18%). Furthermore, the flux recovery of PA-SMPTES-0.8 membrane reaches 94% after cleaning. Thus the TFC membranes modified by this organic-inorganic hybrid technology show potential applications as antifouling RO membrane for desalination and purification.

Fabrication of polyamide thin-film nanocomposite membranes with enhanced surface charge for nitrate ion removal from water resources.

PubMed

Ghaee, A; Zerafat, M M; Askari, P; Sabbaghi, S; Sadatnia, B

2017-03-01

Exclusion due to membrane surface charge is considered as one of the main separation mechanisms occurring in charged membranes, which can be varied through various approaches to affect membrane rejection performance. In this study, thin-film composite (TFC) polyamide (PA) membranes were fabricated via interfacial polymerization of m-phenylenediamine (m-PDA) and 2,4-diaminobenzene sulfonic acid with trimesoyl chloride (TMC) on a polysulfone sub-layer. The ability of the prepared membrane to remove nitrate ions from water resources has been investigated. In order to improve membrane permeability, zeolite-PA thin film nanocomposite (TFN) membranes were fabricated by incorporating natural zeolite nanoparticles obtained through ball milling of an Iranian natural zeolite powder in the interfacial polymerization process. The size, morphology and specific surface area of the as-obtained nanozeolite were characterized using particle size analysis, FE-SEM and BET. The functional groups, morphology and surface charge of the membrane were characterized using ATR-FTIR, SEM and zeta potential analyses. Also, field-emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDS) were used to determine the distribution of nanozeolite in TFN membranes. The influence of zeolite addition to surface roughness was accessed by atomic force microscopy. The performance of TFC and TFN membranes was evaluated in terms of pure water flux and nitrate rejection. The results showed that in case of sulfonated diamine, nitrate ions rejection was enhanced from 63% to 85% which could be attributed to surface charge enhancement. TFN permeability was almost doubled by the addition of nanozeolite.

Water sorption and solubility of polyamide denture base materials

PubMed Central

Nguyen, Long G.; Kopperud, Hilde M.; Øilo, Marit

2017-01-01

Abstract Purpose: Some patients experience adverse reactions to poly(methyl methacrylate)-based (PMMA) dentures. Polyamide (PA) as an alternative to PMMA has, however, not been well documented with regard to water sorption and water solubility. The aim of this in vitro study was to measure water sorption and water solubility of two PA materials compared with PMMA, and to evaluate the major components released from the PA materials and the effect on hardness of the materials. Methods: Ten discs (40.0 mm diameter, 2.0 mm thick) of each material (PA: Valplast and Breflex; PMMA: SR Ivocap HIP) were prepared according to manufacturers’ recommendations. The specimens were tested for water sorption and water solubility, according to a modification of ISO 20795-1:2008. Released substances were analysed by gas chromatography/mass spectrometry (GC/MS). Results: There were statistically significant differences among the materials regarding water sorption, water solubility and time to water saturation. Breflex had the highest water sorption (30.4 μg/mm3), followed by PMMA-material (25.8 μg/mm3) and Valplast (13.6 μg/mm3). Both PA materials had statistically significant lower water solubility than the PMMA. Both PA had a net increase in weight. Analysis by GC/MS identified release of the compound 12-aminododecanolactam from the material Valplast. No release was found from the Breflex material. Conclusions: The PA denture materials show differences in water sorption and solubility, but within the limits of the standard requirements. The PA showed a net increase in weight after long-term water sorption. The clinical implications of the findings are not elucidated. PMID:28642931

Sensor development for in situ detection of concentration polarization and fouling of reverse osmosis membranes

NASA Astrophysics Data System (ADS)

Detrich, Kahlil T.; Goulbourne, Nakhiah C.

2009-03-01

The purpose of this research is to evaluate three polymer electroding techniques in developing a novel in situ sensor for an RO system using the electrical response of a thin film composite sensor. Electrical impedance spectroscopy (EIS) was used to measure the sensor response when exposed to sodium chloride solutions with concentrations from 0.1 M to 0.8 M in both single and double bath configurations. An insulated carbon grease sensor was mechanically stable while a composite Direct Assembly Process (DAP) sensor was fragile upon hydration. Scanning electron microscopy results from an impregnation-reduction technique showed gold nanoparticles were deposited most effectively when presoaked in a potassium hydroxide solution and on an uncoated membrane; surface resistances remained too high for sensor implementation. Through thickness carbon grease sensors showed a transient response to changes in concentration, and no meaningful concentration sensitivity was noted for the time scales over which EIS measurements were taken. Surface carbon grease electrodes attached to the polyamide thin film were not sensitive to concentration. The impedance spectra indicated the carbon grease sensor was unable to detect changes in concentration in double bath experiments when implemented with the polyamide surface exposed to salt solutions. DAP sensors lacked a consistent response to changes in concentration too. A reverse double bath experiment with the polysulfone layer exposed to a constant concentration exhibited a transient impedance response similar to through thickness carbon grease sensors in a single bath at constant concentration. These results suggest that the microporous polysulfone layer is responsible for sensor response to concentration.

Graphene oxide-silica nanohybrids as fillers for PA6 based nanocomposites

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

Maio, A.; Fucarino, R.; Khatibi, R.

Graphene oxide (GO) was prepared by oxidation of graphite flakes by a mixture of H{sub 2}SO{sub 4}/H{sub 3}PO{sub 4} and KMnO{sub 4} based on Marcano's method. Two different masterbatches containing GO (33.3%) and polyamide-6 (PA6) (66.7%) were prepared both via solvent casting in formic acid and by melt mixing in a mini-extruder (Haake). The two masterbatches were then used to prepare PA6-based nanocomposites with a content of 2% in GO. For comparison, a nanocomposite by direct mixing of PA6 and GO (2%) and PA6/graphite nanocomposites were prepared, too. The oxidation of graphite into GO was assessed by X-ray diffraction (XRD),more » Micro-Raman spectroscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) analyses. All these techniques demonstrated the effectiveness of the graphite modification, since the results put into evidence that, after the acid treatment, interlayer distance, oxygen content and defects increased. SEM micrographs carried out on the nanocomposites, showed GO layers totally surrounded by polyamide-6, this feature is likely due to the strong interaction between the hydrophilic moieties located both on GO and on PA6. On the contrary, no interactions were observed when graphite was used as filler. Mechanical characterization, carried out by tensile and dynamic-mechanical tests, marked an improvement of the mechanical properties observed. Photoluminescence and EPR measurements were carried out onto nanoparticles and nanocomposites to study the nature of the interactions and to assess the possibility to use this class of materials as semiconductors or optical sensors.« less

Comparison of wear between occlusal splint materials and resin composite materials.

PubMed

Reyes-Sevilla, M; Kuijs, R H; Werner, A; Kleverlaan, C J; Lobbezoo, F

2018-07-01

Tooth wear in bruxing patients often results in a need for treatment with composite restorations. In some cases, bruxing patients receive an occlusal splint as a protective means as well. However, the wear between these opposing materials has not been investigated yet. The aim of this in vitro study was to assess the wear of different splint materials against resin composite materials. A two-body wear test was conducted using the ACTA wear machine. The materials selected for this study were three composites used for direct restorations (Filtek Z250, CLEARFIL AP-X, and Filtek Supreme XT) and four occlusal splints materials, viz. a polyamide resin (ThermoSens) an conventional (hand-processed), milled and printed polymethylmethacrylate (PMMA). As antagonistic materials, stainless steel, Filtek Supreme XT and CLEARFIL AP-X were used. The wear rate of the seven materials was determined after 200 000 cycles, using a profilometry. The rates were analysed using two-way ANOVA and post hoc Tukey's tests. The wear rates were significantly higher for the conventional and milled PMMA materials than for all other materials (P < .001). The wear rates of printed PMMA and the polyamide resin were comparable to composite wear rates. The antagonist materials have minor or no influence on the amount of wear of the various splint materials (P < .001). In conclusion, different splint materials yielded different wear rates for all antagonist materials tested. Keeping in mind that this study is an experimental in vitro study, this finding enables practitioners to choose the splint material necessary according to their patients' needs. © 2018 John Wiley & Sons Ltd.

Water sorption and solubility of polyamide denture base materials.

PubMed

Nguyen, Long G; Kopperud, Hilde M; Øilo, Marit

2017-01-01

Purpose: Some patients experience adverse reactions to poly(methyl methacrylate)-based (PMMA) dentures. Polyamide (PA) as an alternative to PMMA has, however, not been well documented with regard to water sorption and water solubility. The aim of this in vitro study was to measure water sorption and water solubility of two PA materials compared with PMMA, and to evaluate the major components released from the PA materials and the effect on hardness of the materials. Methods: Ten discs (40.0 mm diameter, 2.0 mm thick) of each material (PA: Valplast and Breflex; PMMA: SR Ivocap HIP) were prepared according to manufacturers' recommendations. The specimens were tested for water sorption and water solubility, according to a modification of ISO 20795-1:2008. Released substances were analysed by gas chromatography/mass spectrometry (GC/MS). Results: There were statistically significant differences among the materials regarding water sorption, water solubility and time to water saturation. Breflex had the highest water sorption (30.4 μg/mm 3 ), followed by PMMA-material (25.8 μg/mm 3 ) and Valplast (13.6 μg/mm 3 ). Both PA materials had statistically significant lower water solubility than the PMMA. Both PA had a net increase in weight. Analysis by GC/MS identified release of the compound 12-aminododecanolactam from the material Valplast. No release was found from the Breflex material. Conclusions: The PA denture materials show differences in water sorption and solubility, but within the limits of the standard requirements. The PA showed a net increase in weight after long-term water sorption. The clinical implications of the findings are not elucidated.

Crystallization of Polymers in Confined Environments: Structural Development of Semi-crystalline Polymer-Layered Silicate Nanocomposites

NASA Astrophysics Data System (ADS)

Vaia, Richard A.; Lincoln, Derek M.; Wang, Zhi-Gang; Hsiao, Benjamin S.; Krishnamoorti, Ramanan

2000-03-01

Over the last decade, the utility of ultrafine dispersions of inorganic nanoparticles to enhance polymer performance and function as precursors to form self-passivating / self-healing inorganic coatings on the polymer surface has been established. Before developing the fundamental structure-property relationships though, a detailed understanding of processing / morphology relationships is necessary. As with other multiphase systems exhibiting nano (1-100 nm) and meso (100-500 nm) order (such as biopolymers, block-copolymers, colloidal suspensions, liquid crystals), physical properties ranging from toughness to optical clarity are determined by morphology on various length scales which in turn arise from processing history. This is anticipated to be especially important for blends containing two or more constituents with fundamental structural features on the nanoscale, such as crystal lamellae and aluminosilicate sheets. Small-angle x-ray scattering experiments with synchrotron radiation reveal the presence of ultra-long range (20-60 nm) mesoscopic ordering of the layered silicate in molten polyamide 6-layered silicate nanocomposites. This superstructure of these semi-rigid inorganic sheets provides a confined environment to examine the crystallization of polyamide 6 with traditional bulk characterization techniques. In addition to a change lamellae organization and lamellae size, the presence of the aluminosilicate layers and extent of interfacial interactions (end-tethered v. physiadsorbed chains) substantially alters the nucleation rate, growth kinetics and Brill transition of the crystal phase as revealed by isothermal crystallization experiments monitored in-situ with synchrotron radiation. These exfoliated nanocomposites provide new opportunities to investigate confined polymer crystallization as well as provide insight into the origin of various property enhancements in these systems.

Preparation and Characterization of Polyimide/Organoclay Nanocomposites

NASA Technical Reports Server (NTRS)

Delozier, D. M.; Orwoll, R. A.; Cahoon, J. F.; Johnston, N. J.; Smith, J. G., Jr.; Connell, J. W.

2002-01-01

Organically modified montmorrrillonite clay, containing a long chain aliphatic quarternary ammonium cation, was used to prepare polyimide/organoclay hybrids. Several approaches were examined in an attempt to achieve fully exfoliated nanocomposites. These included simple mixing of the clay in a pre-made high molecular weight poly(amide acid) solution; simple mixing followed by sonication of the organoclay/poly(amide acid) solutions; and the preparation of high molecular weight poly(amide acid)s in the presence of the organoclay dispersed in N-methyl-2-pyrrolidinone (NMP). The best results were obtained using the in-situ polymerization approach. The resulting nanocomposite films (both amide acid and imide), containing 3-8% by weight of organoclay, were characterized by differential scanning calorimetry (DSC), dynamic thermogravimetric analysis (TGA), transmission electron microscopy (TEM), X-ray diffraction (XRD), and thin film tensile properties. A significant degree of dispersion was observed in the nanocomposite films of the amide acid and the imide. After thermal treatment of amide acid films to effect imidization, in both air and nitrogen, the films were visually darker than control films without clay and the level of clay dispersion appeared to have decreased. In the latter case, the separation between the layers of the clay decreased to a spacing less than that present in the original organoclay. These observations suggest that thermal degradation of the aliphatic quarternary ammonium cation occurred likely during thermal treatment to effect imidization and solvent removal. These thermal degradation effects were less pronounced when thermal treatment was performed under nitrogen. The polyimide/organoclay hybrid films exhibited higher room temperature tensile moduli and lower strength and elongation to break than the control films.

Graphene oxide-silica nanohybrids as fillers for PA6 based nanocomposites

NASA Astrophysics Data System (ADS)

Maio, A.; Fucarino, R.; Khatibi, R.; Botta, L.; Rosselli, S.; Bruno, M.; Scaffaro, R.

2014-05-01

Graphene oxide (GO) was prepared by oxidation of graphite flakes by a mixture of H2SO4/H3PO4 and KMnO4 based on Marcano's method. Two different masterbatches containing GO (33.3%) and polyamide-6 (PA6) (66.7%) were prepared both via solvent casting in formic acid and by melt mixing in a mini-extruder (Haake). The two masterbatches were then used to prepare PA6-based nanocomposites with a content of 2% in GO. For comparison, a nanocomposite by direct mixing of PA6 and GO (2%) and PA6/graphite nanocomposites were prepared, too. The oxidation of graphite into GO was assessed by X-ray diffraction (XRD), Micro-Raman spectroscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) analyses. All these techniques demonstrated the effectiveness of the graphite modification, since the results put into evidence that, after the acid treatment, interlayer distance, oxygen content and defects increased. SEM micrographs carried out on the nanocomposites, showed GO layers totally surrounded by polyamide-6, this feature is likely due to the strong interaction between the hydrophilic moieties located both on GO and on PA6. On the contrary, no interactions were observed when graphite was used as filler. Mechanical characterization, carried out by tensile and dynamic-mechanical tests, marked an improvement of the mechanical properties observed. Photoluminescence and EPR measurements were carried out onto nanoparticles and nanocomposites to study the nature of the interactions and to assess the possibility to use this class of materials as semiconductors or optical sensors.

Molecular recognition of DNA base pairs by the formamido/pyrrole and formamido/imidazole pairings in stacked polyamides

PubMed Central

Buchmueller, Karen L.; Staples, Andrew M.; Uthe, Peter B.; Howard, Cameron M.; Pacheco, Kimberly A. O.; Cox, Kari K.; Henry, James A.; Bailey, Suzanna L.; Horick, Sarah M.; Nguyen, Binh; Wilson, W. David; Lee, Moses

2005-01-01

Polyamides containing an N-terminal formamido (f) group bind to the minor groove of DNA as staggered, antiparallel dimers in a sequence-specific manner. The formamido group increases the affinity and binding site size, and it promotes the molecules to stack in a staggered fashion thereby pairing itself with either a pyrrole (Py) or an imidazole (Im). There has not been a systematic study on the DNA recognition properties of the f/Py and f/Im terminal pairings. These pairings were analyzed here in the context of f-ImPyPy, f-ImPyIm, f-PyPyPy and f-PyPyIm, which contain the central pairing modes, –ImPy– and –PyPy–. The specificity of these triamides towards symmetrical recognition sites allowed for the f/Py and f/Im terminal pairings to be directly compared by SPR, CD and ΔTM experiments. The f/Py pairing, when placed next to the –ImPy– or –PyPy– central pairings, prefers A/T and T/A base pairs to G/C base pairs, suggesting that f/Py has similar DNA recognition specificity to Py/Py. With –ImPy– central pairings, f/Im prefers C/G base pairs (>10 times) to the other Watson–Crick base pairs; therefore, f/Im behaves like the Py/Im pair. However, the f/Im pairing is not selective for the C/G base pair when placed next to the –PyPy– central pairings. PMID:15703305

Effects of surface treatment of aluminium alloy 1050 on the adhesion and anticorrosion properties of the epoxy coating

NASA Astrophysics Data System (ADS)

Sharifi Golru, S.; Attar, M. M.; Ramezanzadeh, B.

2015-08-01

The objective of this work is to investigate the effects of zirconium-based (Zr) conversion coating on the adhesion properties and corrosion resistance of an epoxy/polyamide coating applied on the aluminium alloy 1050 (AA1050). Field emission scanning electron microscope (FE-SEM), energy dispersive X-ray spectrum (EDS), atomic force microscope (AFM) and contact angle measuring device were employed in order to characterize the surface characteristics of the Zr treated AA1050 samples. The epoxy/polyamide coating was applied on the untreated and Zr treated samples. The epoxy coating adhesion to the aluminium substrate was evaluated by pull-off test before and after 30 days immersion in 3.5% w/w NaCl solution. In addition, the electrochemical impedance spectroscopy (EIS) and salt spray tests were employed to characterize the corrosion protection properties of the epoxy coating applied on the AA1050 samples. Results revealed that the surface treatment of AA1050 by zirconium conversion coating resulted in the increase of surface free energy and surface roughness. The dry and recovery (adhesion strength after 30 days immersion in the 3.5 wt% NaCl solution) adhesion strengths of the coatings applied on the Zr treated aluminium samples were greater than untreated sample. In addition, the adhesion loss of the coating applied on the Zr treated aluminium substrate was lower than other samples. Also, the results obtained from EIS and salt spray test clearly revealed that the Zr conversion coating could enhance the corrosion protective performance of the epoxy coating significantly.

[Studies on chemical constituents from leaves and stems of Aconitum coreanum].

PubMed

Li, Yan; Liang, Shuai

2009-05-01

To study the chemical constituents in the leaves and stems of Aconitum coreanum. The isolation and purification of chemical constituents were carried out on silica gel and polyamide column chromatographic. Their structures were identified by physico-chemical properties and spectral analysis. Five compounds were obtained and their structures were identified as guan-fu base I (1), guan-fu base R (2), beta-sitosterol (3), D-mannitol (4), daucosterol (5). Compound 2 is a new compound. Compounds 1 and 3, 4 are isolated from the leaves and stems of A. coreanum for the first time.

Cardenolide glycosides from Elaeodendron australe var. integrifolium.

PubMed

Butler, Mark S; Towerzey, Leanne; Pham, Ngoc B; Hyde, Edward; Wadi, Sao Khemar; Guymer, Gordon P; Quinn, Ronald J

2014-02-01

Extracts from dried leaf and stems of Elaeodendron australe var. integrifolium (Celastraceae) collected in South East Queensland, Australia, were active in an assay that measured Ca(2+) driven expression of IL-2/luciferase designed to identify inhibitors of the ICRAC channel. Bioassay-guided isolation using C18 and polyamide column chromatography, HPLC (Phenyl and C18) and centrifugal partition chromatography (CPC) led to the isolation of digitoxigenin (1) and three cardenolide glycosides, glucoside 2, quinovoside 3 and the new natural product xyloside 4, as the active components with low nM activity in the reporter assay. Copyright © 2013 Elsevier Ltd. All rights reserved.

Mechanical recycling of continuous fiber-reinforced thermoplastic sheets

NASA Astrophysics Data System (ADS)

Moritzer, Elmar; Heiderich, Gilmar

2016-03-01

This contribution examines possible material recycling of offcuts generated during the production of continuous-fiber-reinforced composite sheets. These sheets consist of a polyamide 6 matrix and glass fiber fabric. In the initial step, the offcut is shredded to obtain particles; following that, the particles are processed in a twin-screw process to produce fiber-reinforced plastic pellets with varying fiber contents. These pellets are intended for use in injection molding processes as a substitution for new raw materials. This investigation centers on the mechanical properties which can be achieved with the recycled material after both the twin-screw process and injection molding.

Selective Laser Sintering of PA2200: Effects of print parameters on density, accuracy, and surface roughness

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

Bajric, Sendin

Additive manufacturing needs a broader selection of materials for part production. In order for the Los Alamos National Laboratory (LANL) to investigate new materials for selective laser sintering (SLS), this paper reviews research on the effect of print parameters on part density, accuracy, and surface roughness of polyamide 12 (PA12, PA2200). The literature review serves to enhance the understanding of how changing the laser powder, scan speed, etc. will affect the mechanical properties of a commercial powder. By doing so, this understanding will help the investigation of new materials for SLS.

[Iridoid glycosides from buds of Jasminum officinale L. var. grandiflorum].

PubMed

Zhao, Gui-qin; Yin, Zhi-feng; Liu, Yu-cui; Li, Hong-bo

2011-10-01

The study on the buds of Jasminum officinale L. var. grandiflorum was carried out to look for anti-HBV constituents. The isolation and purification were performed by HPLC and chromatography on silica gel, polyamide and Sephadex LH-20 column. The structures were elucidated on the basis of physicochemical properties and spectral analysis. Six iridoid glycosides were identified as jasgranoside B (1), 6-O-methy-catalpol (2), deacetyl asperulosidic acid (3), aucubin (4), 8-dehydroxy shanzhiside (5), and loganin (6). Jasgranoside B (1) is a new compound. Compounds 2-6 were isolated from Jasminum officinale L. var. grandiflorum for the first time.

Biofouling-resistant ceragenin-modified materials and structures for water treatment

DOEpatents

Hibbs, Michael; Altman, Susan J.; Jones, Howland D. T.; Savage, Paul B.

2013-09-10

This invention relates to methods for chemically grafting and attaching ceragenin molecules to polymer substrates; methods for synthesizing ceragenin-containing copolymers; methods for making ceragenin-modified water treatment membranes and spacers; and methods of treating contaminated water using ceragenin-modified treatment membranes and spacers. Ceragenins are synthetically produced antimicrobial peptide mimics that display broad-spectrum bactericidal activity. Alkene-functionalized ceragenins (e.g., acrylamide-functionalized ceragenins) can be attached to polyamide reverse osmosis membranes using amine-linking, amide-linking, UV-grafting, or silane-coating methods. In addition, silane-functionalized ceragenins can be directly attached to polymer surfaces that have free hydroxyls.

New composite thixotropic hydrogel composed of a polymer hydrogelator and a nanosheet

NASA Astrophysics Data System (ADS)

Ohsedo, Yutaka; Oono, Masashi; Saruhashi, Kowichiro; Watanabe, Hisayuki; Miyamoto, Nobuyoshi

2017-12-01

A composite gel composed of a water-soluble aromatic polyamide hydrogelator and the nanosheet Laponite®, a synthetic layered silicate, was produced and found to exhibit thixotropic behaviour. Whereas the composite gel contains the gelator at the same concentration as the molecular gel made by the gelator only, the composite gel becomes a softer thixotropic gel compared to the molecular gel made by the gelator only. The reason for this could be that bundles of polymer gelator may be loosened and the density of the polymer network increased in the presence of Laponite.

New composite thixotropic hydrogel composed of a polymer hydrogelator and a nanosheet

PubMed Central

Oono, Masashi; Saruhashi, Kowichiro; Watanabe, Hisayuki; Miyamoto, Nobuyoshi

2017-01-01

A composite gel composed of a water-soluble aromatic polyamide hydrogelator and the nanosheet Laponite®, a synthetic layered silicate, was produced and found to exhibit thixotropic behaviour. Whereas the composite gel contains the gelator at the same concentration as the molecular gel made by the gelator only, the composite gel becomes a softer thixotropic gel compared to the molecular gel made by the gelator only. The reason for this could be that bundles of polymer gelator may be loosened and the density of the polymer network increased in the presence of Laponite. PMID:29308249

Enhanced adhesion for LIGA microfabrication by using a buffer layer

DOEpatents

Bajikar, Sateesh S.; De Carlo, Francesco; Song, Joshua J.

2004-01-27

The present invention is an improvement on the LIGA microfabrication process wherein a buffer layer is applied to the upper or working surface of a substrate prior to the placement of a resist onto the surface of the substrate. The buffer layer is made from an inert low-Z material (low atomic weight), a material that absorbs secondary X-rays emissions from the substrate that are generated from the substrate upon exposure to a primary X-rays source. Suitable materials for the buffer layer include polyamides and polyimide. The preferred polyimide is synthesized form pyromellitic anhydride and oxydianiline (PMDA-ODA).

Autogenous electrolyte, non-pyrolytically produced solid capacitor structure

DOEpatents

Sharp, Donald J.; Armstrong, Pamela S.; Panitz, Janda Kirk G.

1998-01-01

A solid electrolytic capacitor having a solid electrolyte comprising manganese dioxide dispersed in an aromatic polyamide capable of further cure to form polyimide linkages, the solid electrolyte being disposed between a first electrode made of valve metal covered by an anodic oxide film and a second electrode opposite the first electrode. The electrolyte autogenously produces water, oxygen, and hydroxyl groups which act as healing substances and is not itself produced pyrolytically. Reduction of the manganese dioxide and the water molecules released by formation of imide linkages result in substantially improved self-healing of anodic dielectric layer defects.

Autogenous electrolyte, non-pyrolytically produced solid capacitor structure

DOEpatents

Sharp, D.J.; Armstrong, P.S.; Panitz, J.K.G.

1998-03-17

A solid electrolytic capacitor is described having a solid electrolyte comprising manganese dioxide dispersed in an aromatic polyamide capable of further cure to form polyimide linkages, the solid electrolyte being disposed between a first electrode made of valve metal covered by an anodic oxide film and a second electrode opposite the first electrode. The electrolyte autogenously produces water, oxygen, and hydroxyl groups which act as healing substances and is not itself produced pyrolytically. Reduction of the manganese dioxide and the water molecules released by formation of imide linkages result in substantially improved self-healing of anodic dielectric layer defects. 2 figs.

Self-discharge mechanism of sealed-type nickel/metal-hydride battery

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

Ikoma, Munehisa; Hoshina, Yasuko; Matsumoto, Isao

1996-06-01

Factors affecting the self-discharge rate of a nickel/metal-hydride (Ni-MH) battery, generally much higher than that of nickel/cadmium (Ni-Cd) battery, are investigated, and the self-discharge mechanism is discussed. Ammonia and amine participate in the shuttle reaction like nitrate ion in the Ni-Cd battery, resulting in acceleration of the self-discharge. When nonwoven fabric made of sulfonated-polypropylene is used as a separator instead of conventional polyamide separator, the self-discharge rate of the Ni-MH battery is strongly depressed, to the same level as that of Ni-Cd battery.

Pyrolysis-Gas Chromatography/Mass Spectrometry of Thermoplastic Polymers

DTIC Science & Technology

1988-04-01

e e- _.. d . %, % ." i WnU xu.U U W" V m Ifw V E IrWW W2’ V ~-.- , . . , S 3.3.5 Polyamide (Nylon 6, 6 T). The thermal degradation of aliphatic...POLYMERS * J.A. Hiltz - M.C. Bissonnette April 1988 Approved by L.J. Leggat Di7 5 tr/ecr;z v ;ion DISTRIBUTION APPROVED BY D /TO TECHNICAL MEMORANDUM 88...detection par spectrom6trie de masse et ionisation de flaime. Les r~sultats indiquent qu’un plastique inconnu peut Atre identifi6 d’apr& s ses produits

Enhanced adhesion for LIGA microfabrication by using a buffer layer

DOEpatents

Bajikar, Sateesh S.; De Carlo, Francesco; Song, Joshua J.

2001-01-01

The present invention is an improvement on the LIGA microfabrication process wherein a buffer layer is applied to the upper or working surface of a substrate prior to the placement of a resist onto the surface of the substrate. The buffer layer is made from an inert low-Z material (low atomic weight), a material that absorbs secondary X-rays emissions from the substrate that are generated from the substrate upon exposure to a primary X-rays source. Suitable materials for the buffer layer include polyamides and polyimide. The preferred polyimide is synthesized form pyromellitic anhydride and oxydianiline (PMDA-ODA).

The sensitivity of relative toxicity rankings by the USF/NASA test method to some test variables

NASA Technical Reports Server (NTRS)

Hilado, C. J.; Labossiere, L. A.; Leon, H. A.; Kourtides, D. A.; Parker, J. A.; Hsu, M.-T. S.

1976-01-01

Pyrolysis temperature and the distance between the source and sensor of effluents are two important variables in tests for relative toxicity. Modifications of the USF/NASA toxicity screening test method to increase the upper temperature limit of pyrolysis, reduce the distance between the sample and the test animals, and increase the chamber volume available for animal occupancy, did not significantly alter rankings of relative toxicity of four representative materials. The changes rendered some differences no longer significant, but did not reverse any rankings. The materials studied were cotton, wool, aromatic polyamide, and polybenzimidazole.

Adsorption of pharmaceuticals onto isolated polyamide active layer of NF/RO membranes.

PubMed

Liu, Yan-Ling; Wang, Xiao-Mao; Yang, Hong-Wei; Xie, Yuefeng F

2018-06-01

Adsorption of trace organic compounds (TrOCs) onto the membrane materials has a great impact on their rejection by nanofiltration (NF) and reverse osmosis (RO) membranes. This study aimed to investigate the difference in adsorption of various pharmaceuticals (PhACs) onto different NF/RO membranes and to demonstrate the necessity of isolating the polyamide (PA) active layer from the polysulfone (PS) support layer for adsorption characterization and quantification. Both the isolated PA layers and the PA+PS layers of NF90 and ESPA1 membranes were used to conduct static adsorption tests. Results showed that apparent differences existed between the PA layer and the PA+PS layer in the adsorption capacity of PhACs as well as the time necessary to reach the adsorption equilibrium. PhACs with different physicochemical properties could be adsorbed to different extents by the isolated PA layer, which was mainly attributed to electrostatic attraction/repulsion and hydrophobic interactions. The PA layer of ESPA1 exhibited apparently higher adsorption capacities for the positively charged PhACs and similar adsorption capacities for the neutral PhACs although it had significantly less total interfacial area (per unit membrane surface area) for adsorption compared to the PA layer of NF90. The higher affinity of the PA layer of ESPA1 for the PhACs could be due to its higher capacity of forming hydrogen bonds with PhACs resulted from the modified chemistry with more -OH groups. This study provides a novel approach to determining the TrOC adsorption onto the active layer of membranes for the ease of investigating adsorption mechanisms. Copyright © 2018 Elsevier Ltd. All rights reserved.

Modulation of DNA-Polyamide Interaction by β-alanine Substitutions: A Study of Positional Effects on Binding Affinity, Kinetics and Thermodynamics

PubMed Central

Wang, Shuo; Aston, Karl; Koeller, Kevin J.; Harris, G. Davis; Rath, Nigam P.

2014-01-01

Hairpin polyamides (PAs) are an important class of sequence-specific DNA minor groove binders, and frequently employ a flexible motif, β-alanine (β), to reduce the molecular rigidity to maintain the DNA recognition register. To better understand the diverse effects β can have on DNA-PA binding affinity, selectivity, and especially kinetics, which have rarely been reported, we have initiated a detailed study for an eight-heterocyclic hairpin PA and its β derivatives with their cognate and mutant sequences. With these derivatives, all internal pyrroles of the parent PA are systematically substituted with single or double βs. A set of complementary experiments have been conducted to evaluate the molecular interactions in detail: UV-melting, biosensor-surface plasmon resonance, circular dichroism and isothermal titration calorimetry. The β substitutions generally weaken the binding affinities of these PAs with cognate DNA, and have large and diverse influences on PA binding kinetics in a position- and number-dependent manner. The DNA base mutations have also shown positional effects on binding of a single PA. Besides the β substitutions, the monocationic Dp group [3-(dimethylamino) propylamine] in parent PA has been modified into a dicationic Ta group (3, 3'-Diamino-N-methyldipropylamine) to minimize the frequently observed PA aggregation with ITC experiments. The results clearly show that the Ta modification not only maintains the DNA binding mode and affinity of PA, but also significantly reduces PA aggregation and allows the complete thermodynamic signature of eight-ring hairpin PA to be determined for the first time. This combined set of results significantly extends our understanding of the energetic basis of specific DNA recognition by PAs. PMID:25141096

Simultaneous Binding of Hybrid Molecules Constructed with Dual DNA-Binding Components to a G-Quadruplex and Its Proximal Duplex.

PubMed

Asamitsu, Sefan; Obata, Shunsuke; Phan, Anh Tuân; Hashiya, Kaori; Bando, Toshikazu; Sugiyama, Hiroshi

2018-03-20

A G-quadruplex (quadruplex) is a nucleic acid secondary structure adopted by guanine-rich sequences and is considered to be relevant to various pharmacological and biological contexts. Although a number of researchers have endeavored to discover and develop quadruplex-interactive molecules, poor ligand designability originating from topological similarity of the skeleton of diverse quadruplexes has remained a bottleneck for gaining specificity for individual quadruplexes. This work reports on hybrid molecules that were constructed with dual DNA-binding components, a cyclic imidazole/lysine polyamide (cIKP), and a hairpin pyrrole/imidazole polyamide (hPIP), with the aim toward specific quadruplex targeting by reading out the local duplex DNA sequence adjacent to designated quadruplexes in the genome. By means of circular dichroism (CD), fluorescence resonance energy transfer (FRET), surface plasmon resonance (SPR), and NMR techniques, we showed the dual and simultaneous recognition of the respective segment via hybrid molecules, and the synergistic and mutual effect of each binding component that was appropriately linked on higher binding affinity and modest sequence specificity. Monitoring quadruplex and duplex imino protons of the quadruplex/duplex motif titrated with hybrid molecules clearly revealed distinct features of the binding of hybrid molecules to the respective segments upon their simultaneous recognition. A series of the systematic and detailed binding assays described here showed that the concept of simultaneous recognition of quadruplex and its proximal duplex by hybrid molecules constructed with the dual DNA-binding components may provide a new strategy for ligand design, enabling targeting of a large variety of designated quadruplexes at specific genome locations. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of multi-walled carbon nanotubes on rheological and physical properties of polyamide-based thermoplastic elastomers

NASA Astrophysics Data System (ADS)

Bae, Won-Sik; Kwon, Oh Joo; Kim, Byoung Chul; Chae, Dong Wook

2012-09-01

The polyamide-based thermoplastic elastomers (Pebax®) were melt compounded with multi-walled carbon nanotubes (MWNTs: 0.25˜5 wt%) and the variation of rheological and physical properties with MWNT contents was investigated. The crystallization temperature (Tc) of the nanocomposites with 0.5 wt% MWNTs was most increased by ca. 8oC, but it was decreased by further addition. In addition, the presence of MWNTs broadened the Tc peak with increasing nanotube contents. In contrast, the melting behavior was little influenced by the presence of MWNTs for all compositions. The incorporation of MWNTs increased the complex viscosity with MWNT contents and the abrupt increase was observed from 1 wt%. In addition, lower Newtonian flow region became disappearing with increasing MWNT contents, exhibiting notable shear thinning behavior from 1 wt% loading. Storage modulus was increased with MWNT contents in a similar manner to viscosity. Casson plot demonstrated a non-zero positive intercept for all the samples. In particular, the abrupt increase of yield stress was observed from 1 wt% loading. In the Cole-Cole plot, the nanocomposites gave a deviated curve from pure Pebax and the slope was decreased with increasing MWNT contents. The relaxation time calculated from viscoelastic parameters was increased with nanotube contents, but the increasing extents were reduced with increasing frequency. From 2 wt% MWNTs, the electrical conductivity was observed, indicating that the electrical percolation existed between 1.5 and 2 wt%. At 0.25 wt% loading the tensile strength was slightly increased, but it was gradually decreased by further addition. The introduction of MWNTs increased the tensile modulus with nanotube contents. In addition, ductile properties were reduced with increasing MWNT contents, resulting in low toughness.

Mechanical properties and cytocompatibility of carbon fibre reinforced nano-hydroxyapatite/polyamide66 ternary biocomposite.

PubMed

Zhang, Xuesong; Zhang, Yonggang; Zhang, Xuelian; Wang, Yan; Wang, Jiaqi; Lu, Ming; Li, Hong

2015-02-01

Fibre-reinforced composites with good strength and ductility as bone repair biomaterials have been attracting increasing attention in biomedical applications. In the present study, a novel ternary composite was prepared using carbon fibre (CF) to reinforce a nano-hydroxyapatite/polyamide66 composite (HA/PA). The interface and mechanical strength of the ternary composite (CF/HA/PA) were characterised. In addition, to assess the cytocompatibility, the composite was co-cultured with MG-63 cells, and the cell morphology, MTT, and ALP were tested. The results indicated that CFs were uniformly distributed in the HA/PA matrix with random orientation and that the CFs bonded well to the HA/PA matrix. The reinforced ternary composite exhibited a compressive strength of 116-212 MPa, a bending strength of 89-138 MPa, a tensile strength of 109-181 MPa, with the breaking elongation ratio of 6.2-9.1%, and a tensile modulus of 2.9-5.8 GPa, with the values varying with increasing CF content from 5 to 20 (mass fraction). The MG-63 cells of normal phenotype were well extended and spread onto the ternary composite surface. In addition, its proliferation and differentiation on the composite surface were significantly increased with time, indicating that the incorporation of CFs into HA/PA had little negative effects on MG-63 cells. The incorporation of CFs into a HA/PA66 composite improved the strength and ductility and introduced no negative effects on the cytocompatibility. Hence, the CF/HA/PA ternary composite has potential to be used as a bone repair materials and in fixation devices. Copyright © 2014 Elsevier Ltd. All rights reserved.

Correlation of Local Effects of DNA Sequence and Position of Beta-Alanine Inserts with Polyamide-DNA Complex Binding Affinities and Kinetics

PubMed Central

Wang, Shuo; Nanjunda, Rupesh; Aston, Karl; Bashkin, James K.; Wilson, W. David

2012-01-01

In order to better understand the effects of β-alanine (β) substitution and the number of heterocycles on DNA binding affinity and selectivity, the interactions of an eight-ring hairpin polyamide (PA) and two β derivatives as well as a six-heterocycle analog have been investigated with their cognate DNA sequence, 5′-TGGCTT-3′. Binding selectivity and the effects of β have been investigated with the cognate and five mutant DNAs. A set of powerful and complementary methods have been employed for both energetic and structural evaluations: UV-melting, biosensor-surface plasmon resonance, isothermal titration calorimetry, circular dichroism and a DNA ligation ladder global structure assay. The reduced number of heterocycles in the six-ring PA weakens the binding affinity; however, the smaller PA aggregates significantly less than the larger PAs, and allows us to obtain the binding thermodynamics. The PA-DNA binding enthalpy is large and negative with a large negative ΔCp, and is the primary driving component of the Gibbs free energy. The complete SPR binding results clearly show that β substitutions can substantially weaken the binding affinity of hairpin PAs in a position-dependent manner. More importantly, the changes in PA binding to the mutant DNAs further confirm the position-dependent effects on PA-DNA interaction affinity. Comparison of mutant DNA sequences also shows a different effect in recognition of T•A versus A•T base pairs. The effects of DNA mutations on binding of a single PA as well as the effects of the position of β substitution on binding tell a clear and very important story about sequence dependent binding of PAs to DNA. PMID:23167504

Reactive processing of textile-natural fiber reinforced anionic polyamide-6 composites

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

Kan, Ze; Chen, Peng; Liu, Zhengying

Nowadays natural fiber, used in reinforced composites, is widely concerned. However, no natural fiber reinforced reactive thermoplastic polymer grades had been prepared so far. Through our studies, it was demonstrated that there was a severe retardation and discoloration occurred in the reactive processing between anionic polyamide-6 (APA-6) and natural fiber, which result in incomplete polymerization when put together. In order to solve the problem, two methods were adopted in this paper, which are fiber pretreatment and usage of a new-style initiator called caprolactam magnesium bromide. The former is to remove sizing agent and impurities on the surface of fiber, andmore » the latter is to weaken the side reactions between APA-6 and natural fiber by the nature of its lower reactivity and weaker alkaline. In cooperation with both methods, the severe retardation and discoloration had been improved significantly, so that the polymerization of APA-6 in natural fiber was occurred smoothly. Following textile-natural fiber reinforced APA-6 composites with an average thickness of 2.5 mm and a fiber volume content of 50% was prepared by vacuum assisted resin transfer molding (VARTM). The soxhlet extraction, dilute solution viscometry and differential scanning calorimeter (DSC) measurements respectively suggested the degree of conversion, viscosity-average molar mass and crystallization of composites was up to 94%, 11.3×104 and 50%. Remarkable improvement of mechanical properties were achieved through dynamic mechanical analysis (DMA), tensile and three-point bending test. Favorable interfacial adhesion and wettability were revealed by scanning electron microscopy (SEM) observation. Therefore, all of the above good performance make this new-style and environmentally friendly composites have broad application prospects.« less

Properties of Cement Mortar by Use of Hot-Melt Polyamides as Substitute for Fine Aggregate

PubMed Central

Yuan, Xiongzhou; Xu, Weiting; Sun, Wei; Xing, Feng; Wang, Weilun

2015-01-01

This paper presents an experimental study on use of hot-melt polyamide (HMP) to prepare mortar specimens with improved crack healing and engineering properties. The role of HMP in the crack repairing of cement mortar subjected to several rounds of heat treatment was investigated. Compatibility between HMP and hydraulic cement was investigated through X-ray diffraction (XRD) and Fourier transform infrared spectra (FTIR) technology. Mortar specimens were prepared using standard cement mortar mixes with HMP at 1%, 3% and 5% (by volume) for fine aggregate substitute. After curing for 28 days, HMP specimens were subjected to heating at temperature of 160 °C for one, two, and three days and then natural cooling down to ambient temperature. Mechanical and durability properties of the heated HMP mortars were evaluated and compared with those of the corresponding mortars without heating. The microscopic observation of the interfacial transition zone (ITZ) of HMP mortar was conducted through environmental scanning electron microscopy (ESEM). Results reveal that incorporation of HMP improves the workability of the HMP/cement binder while leading to decrease in compressive strength and durability. The heated HMP mortars after exposure to heating for one, two, and three days exhibit no obvious change in compressive strength while presenting notable increase in flexural strength and durability compared with the corresponding mortars without heating. The XRD, FTIR and ESEM analyses indicate that no obvious chemical reaction occurs between HMP and hydraulic cement, and thus the self-repairing for interfacial micro-crack in HMP/cement composite system is ascribed to the physical adhesion of HMP to cement matrix rather than the chemical bonding between them.

Tensile strength decreases and perfusion pressure of 3-holed polyamide epidural catheters increases in long-term epidural infusion.

PubMed

Kim, Pascal; Meyer, Urs; Schüpfer, Guido; Rukwied, Roman; Konrad, Christoph; Gerber, Helmut

2011-01-01

Epidural analgesia is an established method for pain management. The failure rate is 8% to 12% due to technical difficulties (catheter dislocation and/or disconnection; partial or total catheter occlusion) and management. The mechanical properties of the catheters, like tensile strength and flow rate, may also be affected by the analgesic solution and/or the tissue environment. We investigated the tensile strength and perfusion pressure of new (n=20), perioperatively (n=30), and postoperatively (n=73) used epidural catheters (20-gauge, polyamide, closed tip, 3 side holes; Perifix [B. Braun]). To prevent dislocation, epidural catheters were taped (n=5) or fixed by suture (n=68) to the skin. After removal, mechanical properties were assessed by a tensile-testing machine (INSTRON 4500), and perfusion pressure was measured at flow rates of 10, 20, and 40 mL/h. All catheters demonstrated a 2-step force transmission. Initially, a minimal increase of length could be observed at 15 N followed by an elongation of several cm at additional forces (7 N). Breakage occurred in the control group at 23.5±1.5 N compared with 22.4±1.6 N in perioperative and 22.4±1.7 N in postoperative catheters (P<0.05). Duration of catheter use had no effect on tensile strength, whereas perfusion pressure at clinically used flow rates (10 mL/h) increased significantly from 19±1.3 to 44±72 mm Hg during long-term (≥7 days) epidural analgesia (P<0.05, analysis of variance). Fixation by suture had no influence on tensile strength or perfusion pressure. Epidural catheter use significantly increases the perfusion pressure and decreases the tensile strength. Copyright © 2011 by American Society of Regional Anesthesia and Pain Medicine

Degradation Analysis of Field-Exposed Photovoltaic Modules with Non-Fluoropolymer-Based Backsheets

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

Kempe, Michael D; Fairbrother, Andrew; Julien, Scott

The selection of polymeric materials utilized in photovoltaic (PV) modules has changed relatively little since the inception of the PV industry, with ethylene-vinyl acetate (EVA), polyethylene terephthalate (PET), and fluoropolymer-based laminates being the most widely adopted primary components of the encapsulant and backsheet materials. The backsheet must serve to electrically insulate the solar cells and protect them from the effects of weathering. Due to continued downward pressure on cost, other polymeric materials are being formulated to withstand outdoor exposure for use in backsheets to replace either the PET film, the fluoropoymer film, or both. Because of their relatively recent deployment,more » less is known about their reliability and if they are durable enough to fulfill the greater than or equal to 25 year warranties of current PV modules. This work presents a degradation analysis of field-exposed modules with polyamide- and polyester-based backsheets. Modules were exposed for up to five years in different geographic locations: USA (Maryland, Ohio), China, and Italy. Surface and cross-sectional analysis included visual inspection, colorimetry, glossimetry, and Fourier-transform infrared spectroscopy. Each module experienced different types of degradation depending on the exposure site, even for the same material and module brand. For instance, the polyamide-based backsheet experienced hairline cracking and greater yellowing and chemical changes in China (Changsu, humid subtropical climate), while in Italy (Rome, hot-summer Mediterranean climate) it underwent macroscopic cracking and greater losses in gloss. Spectroscopic studies have permitted identification of degradation products and changes in polymer structure over time. Comparisons are made to fielded modules with fluoropolymer-based backsheets, as well as backsheet materials in accelerated laboratory exposures. Implications for qualification testing and service life prediction of the non-fluoropolymer-based backsheets are discussed.« less

Degradation analysis of field-exposed photovoltaic modules with non-fluoropolymer-based backsheets

NASA Astrophysics Data System (ADS)

Fairbrother, Andrew; Julien, Scott; Wan, Kai-Tak; Ji, Liang; Boyce, Kenneth; Merzlic, Sebastien; Lefebvre, Amy; O'Brien, Greg; Wang, Yu; Bruckman, Laura; French, Roger; Kempe, Michael; Gu, Xiaohong

2017-08-01

The selection of polymeric materials utilized in photovoltaic (PV) modules has changed relatively little since the inception of the PV industry, with ethylene-vinyl acetate (EVA), polyethylene terephthalate (PET), and fluoropolymer-based laminates being the most widely adopted primary components of the encapsulant and backsheet materials. The backsheet must serve to electrically insulate the solar cells and protect them from the effects of weathering. Due to continued downward pressure on cost, other polymeric materials are being formulated to withstand outdoor exposure for use in backsheets to replace either the PET film, the fluoropoymer film, or both. Because of their relatively recent deployment, less is known about their reliability and if they are durable enough to fulfill the >=25 year warranties of current PV modules. This work presents a degradation analysis of field-exposed modules with polyamide- and polyester-based backsheets. Modules were exposed for up to five years in different geographic locations: USA (Maryland, Ohio), China, and Italy. Surface and cross-sectional analysis included visual inspection, colorimetry, glossimetry, and Fourier-transform infrared spectroscopy. Each module experienced different types of degradation depending on the exposure site, even for the same material and module brand. For instance, the polyamide-based backsheet experienced hairline cracking and greater yellowing and chemical changes in China (Changsu, humid subtropical climate), while in Italy (Rome, hot-summer Mediterranean climate) it underwent macroscopic cracking and greater losses in gloss. Spectroscopic studies have permitted identification of degradation products and changes in polymer structure over time. Comparisons are made to fielded modules with fluoropolymer-based backsheets, as well as backsheet materials in accelerated laboratory exposures. Implications for qualification testing and service life prediction of the non-fluoropolymer-based backsheets are discussed.

Dynamic perfusion bioreactor system for 3D culture of rat bone marrow mesenchymal stem cells on nanohydroxyapatite/polyamide 66 scaffold in vitro.

PubMed

Qian, Xu; Yuan, Fang; Zhimin, Zhu; Anchun, Mo

2013-08-01

The aim of the study was to investigate the biocompatibility and osteogenic effectiveness of the porous nanohydroxyapatite/polyamide 66 (n-HA/PA66) scaffold material that was cultured with the rat bone marrow mesenchymal stem cells (rBMSCs), under the static culture condition and the dynamic perfusion culture condition in vitro, and to investigate whether the 3D perfusion culture condition was better in provoking proliferation of rBMSCs than the 3D static culture condition. The Methyl thiazolyl tetrazolium (MTT) assay, alkaline phosphatase (ALP) activity assay, Osteocalcin (OCN) assay and scanning electron microscope (SEM) were used to observe the proliferation and differentiation of rBMSCs. The samples were respectively harvested at 1st, 3rd, 7th, 14th, and 21st days and effect comparisons were made between the two of the culture conditions. The results showed that values of MTT, ALP, and OCN were increased continuously and revealed a significant difference between the two culture conditions (p < 0.05). On the 14th day, SEM revealed calcified nodules 2-8 μm in diameter in the lamellar structure. Under the static culture condition, the pores were covered with the cells looking like a piece of blanket, but under the perfusion culture condition the cells were observed to have a 3D lamellar structure. In conclusion, the porous n-HA/PA66 scaffold material can be used as a good candidate material for the bone scaffold construction in the tissue engineering because of its excellent 3D structure, which can greatly improve the proliferation and differentiation of rBMSCs and make them proliferate and osteogenesis even better under the perfusion culture condition. Copyright © 2013 Wiley Periodicals, Inc.

Reactive processing of textile-natural fiber reinforced anionic polyamide-6 composites

NASA Astrophysics Data System (ADS)

Kan, Ze; Chen, Peng; Liu, Zhengying; Feng, Jianmin; Yang, Mingbo

2015-05-01

Nowadays natural fiber, used in reinforced composites, is widely concerned. However, no natural fiber reinforced reactive thermoplastic polymer grades had been prepared so far. Through our studies, it was demonstrated that there was a severe retardation and discoloration occurred in the reactive processing between anionic polyamide-6 (APA-6) and natural fiber, which result in incomplete polymerization when put together. In order to solve the problem, two methods were adopted in this paper, which are fiber pretreatment and usage of a new-style initiator called caprolactam magnesium bromide. The former is to remove sizing agent and impurities on the surface of fiber, and the latter is to weaken the side reactions between APA-6 and natural fiber by the nature of its lower reactivity and weaker alkaline. In cooperation with both methods, the severe retardation and discoloration had been improved significantly, so that the polymerization of APA-6 in natural fiber was occurred smoothly. Following textile-natural fiber reinforced APA-6 composites with an average thickness of 2.5 mm and a fiber volume content of 50% was prepared by vacuum assisted resin transfer molding (VARTM). The soxhlet extraction, dilute solution viscometry and differential scanning calorimeter (DSC) measurements respectively suggested the degree of conversion, viscosity-average molar mass and crystallization of composites was up to 94%, 11.3×104 and 50%. Remarkable improvement of mechanical properties were achieved through dynamic mechanical analysis (DMA), tensile and three-point bending test. Favorable interfacial adhesion and wettability were revealed by scanning electron microscopy (SEM) observation. Therefore, all of the above good performance make this new-style and environmentally friendly composites have broad application prospects.

Antibacterial activity of plastics coated with silver-doped organic-inorganic hybrid coatings prepared by sol-gel processes.

PubMed

Marini, M; De Niederhausern, S; Iseppi, R; Bondi, M; Sabia, C; Toselli, M; Pilati, F

2007-04-01

Silver-doped organic-inorganic hybrid coatings were prepared starting from tetraethoxysilane- and triethoxysilane-terminated poly(ethylene glycol)-block-polyethylene by the sol-gel process. They were applied as a thin layer (0.6-1.1 microm) to polyethylene (PE) and poly(vinyl chloride) (PVC) films and the antibacterial activity of the coated films was tested against Gram-negative (Escherichia coli ATCC 25922) and Gram-positive (Staphylococcus aureus ATCC 6538) bacteria. The effect of several factors (such as organic-inorganic ratio, type of catalyst, time of post-curing, silver ion concentration, etc.) was investigated. Measurements at different contact times showed a rapid decrease of the viable count for both tested strains. The highest antibacterial activity [more than 6 log reduction within 6 h starting from 106 colony-forming units (cfu) mL-1] was obtained for samples with an organic-inorganic weight ratio of 80:20 and 5 wt % silver salt with respect to the coating. For the coatings prepared by an acid-catalyzed process, a high level of permanence of the antibacterial activity of the coated films was demonstrated by repeatedly washing the samples in warm water or by immersion in physiological saline solution at 37 degrees C for 3 days. The release of silver ions per square meter of coating is very similar to that previously observed for polyamides filled with metallic silver nanoparticles; however, when compared on the basis of Ag content, the concentration of silver ions released from the coating is much higher than that released from 1 mm thick specimens of polyamide (PA) filled with silver nanoparticles. Transparency and good adhesion of the coating to PE and PVC plastic substrates without any previous surface treatment are further interesting features.

Ligase Detection Reaction for the Analysis of Point Mutations using Free Solution Conjugate Electrophoresis in a Polymer Microfluidic Device

PubMed Central

Sinville, Rondedrick; Coyne, Jennifer; Meagher, Robert J.; Cheng, Yu-Wei; Barany, Francis; Barron, Annelise; Soper, Steven A.

2010-01-01

We have developed a new method for the analysis of low abundant point mutations in genomic DNA using a combination of an allele-specific ligase detection reaction (LDR) with free-solution conjugate electrophoresis (FSCE) to generate and analyze the genetic products. FSCE eliminates the need for a polymer sieving matrix by conjugating chemically synthesized polyamide “drag-tags” onto the LDR primers. The additional drag of the charge-neutral drag-tag breaks the linear scaling of the charge-to-friction ratio of DNA and enables size-based separations of DNA in free solution using electrophoresis with no sieving matrix. We successfully demonstrate the conjugation of polyamide drag-tags onto a set of four LDR primers designed to probe the K-ras oncogene for mutations highly associated with colorectal cancer, the simultaneous generation of fluorescently-labeled LDR/drag-tagged (LDR-dt) products in a multiplexed, single-tube format with mutant:wild-type ratios as low as 1:100, respectively, and the single-base, high-resolution separation of all four LDR-dt products. Separations were conducted in free solution with no polymer network using both a commercial capillary array electrophoresis (CAE) system and a poly(methylmethacrylate), PMMA, microchip replicated via hot-embossing with only a Tris-based running buffer containing additives to suppress the electroosmotic flow (EOF). Typical analysis times for LDR-dt conjugates were 11 min using the CAE system and as low as 85 s for the PMMA microchips. With resolution comparable to traditional gel-based CAE, FSCE along with microchip electrophoresis decreased the separation time by more than a factor of 40. PMID:19053073

From zero to hero - production of bio-based nylon from renewable resources using engineered Corynebacterium glutamicum.

PubMed

Kind, Stefanie; Neubauer, Steffi; Becker, Judith; Yamamoto, Motonori; Völkert, Martin; Abendroth, Gregory von; Zelder, Oskar; Wittmann, Christoph

2014-09-01

Polyamides are important industrial polymers. Currently, they are produced exclusively from petrochemical monomers. Herein, we report the production of a novel bio-nylon, PA5.10 through an integration of biological and chemical approaches. First, systems metabolic engineering of Corynebacterium glutamicum was used to create an effective microbial cell factory for the production of diaminopentane as the polymer building block. In this way, a hyper-producer, with a high diaminopentane yield of 41% in shake flask culture, was generated. Subsequent fed-batch production of C. glutamicum DAP-16 allowed a molar yield of 50%, a productivity of 2.2gL(-1)h(-1), and a final titer of 88gL(-1). The streamlined producer accumulated diaminopentane without generating any by-products. Solvent extraction from alkalized broth and two-step distillation provided highly pure diaminopentane (99.8%), which was then directly accessible for poly-condensation. Chemical polymerization with sebacic acid, a ten-carbon dicarboxylic acid derived from castor plant oil, yielded the bio-nylon, PA5.10. In pure form and reinforced with glass fibers, the novel 100% bio-polyamide achieved an excellent melting temperature and the mechanical strength of the well-established petrochemical polymers, PA6 and PA6.6. It even outperformed the oil-based products in terms of having a 6% lower density. It thus holds high promise for applications in energy-friendly transportation. The demonstration of a novel route for generation of bio-based nylon from renewable sources opens the way to production of sustainable bio-polymers with enhanced material properties and represents a milestone in industrial production. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

Methods for attaching polymerizable ceragenins to water treatment membranes using amine and amide linkages

DOEpatents

Hibbs, Michael; Altman, Susan J.; Jones, Howland D.T.; Savage, Paul B.

2013-10-15

This invention relates to methods for chemically grafting and attaching ceragenin molecules to polymer substrates; methods for synthesizing ceragenin-containing copolymers; methods for making ceragenin-modified water treatment membranes and spacers; and methods of treating contaminated water using ceragenin-modified treatment membranes and spacers. Ceragenins are synthetically produced antimicrobial peptide mimics that display broad-spectrum bactericidal activity. Alkene-functionalized ceragenins (e.g., acrylamide-functionalized ceragenins) can be attached to polyamide reverse osmosis membranes using amine-linking, amide-linking, UV-grafting, or silane-coating methods. In addition, silane-functionalized ceragenins can be directly attached to polymer surfaces that have free hydroxyls.

Methods for attaching polymerizable ceragenins to water treatment membranes using silane linkages

DOEpatents

Hibbs, Michael; Altman, Susan J.; Jones, Howland D. T.; Savage, Paul B.

2013-09-10

This invention relates to methods for chemically grafting and attaching ceragenin molecules to polymer substrates; methods for synthesizing ceragenin-containing copolymers; methods for making ceragenin-modified water treatment membranes and spacers; and methods of treating contaminated water using ceragenin-modified treatment membranes and spacers. Ceragenins are synthetically produced antimicrobial peptide mimics that display broad-spectrum bactericidal activity. Alkene-functionalized ceragenins (e.g., acrylamide-functionalized ceragenins) can be attached to polyamide reverse osmosis membranes using amine-linking, amide-linking, UV-grafting, or silane-coating methods. In addition, silane-functionalized ceragenins can be directly attached to polymer surfaces that have free hydroxyls.

Molecular Level Coating of Metal Oxide Particles

NASA Technical Reports Server (NTRS)

McDaniel, Patricia R. (Inventor); St.Clair, Terry L. (Inventor)

2002-01-01

Polymer encapsulated metal oxide particles are prepared by combining a polyamide acid in a polar osmotic solvent with a metal alkoxide solution. The polymer was imidized and the metal oxide formed simultaneously in a refluxing organic solvent. The resulting polymer-metal oxide is an intimately mixed commingled blend, possessing, synergistic properties of both the polymer and preceramic metal oxide. The encapsulated metal oxide particles have multiple uses including, being useful in the production of skin lubricating creams, weather resistant paints, as a filler for paper. making ultraviolet light stable filled printing ink, being extruded into fibers or ribbons, and coatings for fibers used in the production of composite structural panels.

Adhesives and the ATS satellite. [construction of honeycomb panels

NASA Technical Reports Server (NTRS)

Hancock, F. E.

1972-01-01

Adhesives in the ATS satellite allow the designers to save weight, simplify design and fabrication and provide thermal and electrical conductivity or resistivity as required. The selections of adhesives are restricted to those few which can pass rigorous outgassing tests in order to avoid contaminating lenses and thermal control surfaces in space. An epoxy adhesive is used to construct the honeycomb panels which constitute most of the satellite's structure. General purpose epoxy adhesives hold doublers and standoffs in place and bond the truss to its fittings. Specialized adhesives include a high temperature resistant polyamide, a flexible polyurethane and filled epoxies which conduct heat or electricity.

[Current status of bio-based materials industry in China].

PubMed

Diao, Xiaoqian; Weng, Yunxuan; Huang, Zhigang; Yang, Nan; Wang, Xiyuan; Zhang, Min; Jin, Yujuan

2016-06-25

In recent years, bio-based materials are becoming a new dominant industry leading the scientific and technological innovation, and economic development of the world. We reviewed the new development of bio-based materials industry in China, analyzed the entire market of bio-based materials products comprehensively, and also stated the industry status of bio-based chemicals, such as lactic acid, 1,3-propanediol, and succinic acid; biodegradable bio-based polymers, such as co-polyester of diacid and diol, polylactic acid, carbon dioxide based copolymer, polyhydroxyalknoates, polycaprolactone, and thermoplastic bio-based plastics; non-biodegradable bio-based polymers, such as bio-based polyamide, polytrimethylene terephthalate, bio-based polyurethane, and bio-based fibers.

Molecular Level Coating for Metal Oxide Particles

NASA Technical Reports Server (NTRS)

McDaniel, Patricia R. (Inventor); Saint Clair, Terry L. (Inventor)

2000-01-01

Polymer encapsulated metal oxide particles are prepared by combining a polyamide acid in a polar aprotic solvent with a metal alkoxide solution. The polymer was imidized and the metal oxide formed simultaneously in a refluxing organic solvent. The resulting polymer-metal oxide is an intimately mixed commingled blend, possessing synergistic properties of both the polymer and preceramic metal oxide. The encapsulated metal oxide particles have multiple uses including, being useful in the production of skin lubricating creams, weather resistant paints, as a filler for paper, making ultraviolet light stable filled printing ink, being extruded into fibers or ribbons, and coatings for fibers used in the production of composite structural panels.

Effect of temperature and heating rate on apparent lethal concentrations of pyrolysis products

NASA Technical Reports Server (NTRS)

Hilado, C. J.; Solis, A. N.; Marcussen, W. H.; Furst, A.

1976-01-01

The apparent lethal concentrations for 50 percent of the test animals of the pyrolysis products from twelve polymeric materials were studied as a function of temperature and heating rate. The materials were polyethylene, nylon 6, ABS, polycarbonate, polyether sulfone, polyaryl sulfone, wool fabric, aromatic polyamide fabric, polychloroprene foam, polyvinyl fluoride film, Douglas fir, and red oak. The apparent lethal concentration values of most materials vary significantly with temperature and heating rate. The apparent lethal concentration values, based on weight of sample charged, appears to effectively integrate the thermophysical, thermochemical, and physiological responses from a known quantity of material under specified imposed conditions.

Examination for optimization of synchrotron radiation spectrum for the x ray depth lithography

NASA Astrophysics Data System (ADS)

Dany, Raimund

1992-06-01

The effect of reducing the vertical distribution of synchrotron radiation on its spectral distribution is examined through resin irradiation. The resulting filter effect is compared to that of absorption filters. Transmission coefficients of titanium, gold, and polyamide were calculated from linear absorption coefficients with the Beer law. The use of a diaphragm in X-ray depth lithography, which is the first step of the LIGA (Lithography Galvanoforming Molding) process, is discussed. A calorimetric device for determining the synchrotron radiation power and distribution was developed and tested. Measurements at the ELSA storage ring show a strong dependence of the vertical emittance on the electron current.

Morphology and kinetics of the formation of polyamide benzimidazole in N-methylpyrrolidone

NASA Astrophysics Data System (ADS)

Khanchich, O. A.; Larionov, V. B.; Biryukov, A. L.

2018-02-01

Polymerization-optical methods were used to study the supermolecular structure in the gelation of systems based on polyamidobenzimidazole (PABI) in N-methylpyrrolidone (N-MP) and the kinetics of phase transformations during polymer coagulation from a the solution. It was found that the use of N-MP leads to the appearance in the PABI-N-MP-H2O system of spherulites having a structure characteristic of LC structures. It is shown that the alternation of metastable structures upon gelation of the PABY - N-MP-H2O system is consistent with the appearance of the LC phase of the cholesteric type.

Building a resistance to ignition testing device for sunglasses and analysing data: a continuing study for sunglasses standards.

PubMed

Magri, Renan; Masili, Mauro; Duarte, Fernanda Oliveira; Ventura, Liliane

2017-09-21

Sunglasses popularity skyrocketed since its advent. The ongoing trend led to the creation of standards to protect consumers from injuries and secondary hazards due to spectacles use. In Brazil, the corresponding standard is NBR ISO 12312-1:2015 and since there is no mandatory testing, evaluating sunglasses performance provides an insight into compliance with the standard. In a continuing revision of sunglasses standards requirements, resistance to ignition is one of the concerns, since sunglasses should be protected from burning into flames at a pre-determined temperature, which may protect user of getting their sunglasses into flames if some, cigarette sparks reaches the spectacles, as an example. This paper describes the building of a resistance to ignition system and the results of 410 samples that have been tested accordingly to ISO 12312-1. The procedure is in accordance with the resistance to ignition test. It consists of heating a steel rod to 650 °C and pressing it against the sample surface for 5 s, with a force equivalent to the rod weight. For carrying out the assessments, we have build resistance to ignition testing system and assured the testing requirements of the standard. The apparatus has an electrical furnace with a temperature acquisition circuit and electronic control that maintains the temperature of the steel rod at 650 °C. A linear actuator was designed for the project to drive the steel rod vertically and pressing it against the sunglasses samples. The control system is composed by a Freescale development board FRDM-KL25Z with an ARM Cortex-M0 embedded. We have also provided a LabView PC interface for acquiring, displaying, and storing data as well as added a physical control panel to the equipment for performing the evaluations. We assessed 410 sunglasses frames at the built apparatus, where the 410 lenses came out to be in accordance with the guidelines provided by the ignition to resistance test. Out of the 410 tested frames, 50% were made of polyamide (nylon 12); 10% were made of polyamide (nylon 11, mamona oil); 5% were made of cellulose acetate; 15% were made of ABS and 20% were made of polycarbonate. Out of the 410 tested lenses, 80% were polycarbonate; 2% were polymethyl methacrylate (PMMA); 5% CR-39 (with polarizing filter inside); 12.8% polyamide; 0.2% glass. For all the 410 tested spectacles frames and lenses, none burst into flames or continued to melt at the end of the procedure, being in compliance with ISO 12312-1:2013. The evidences show that all the tested thermoplastic and thermosetting materials are exceptionally resistant to ignition and all samples assessed comply with the resistance to ignition test. The analysis of the sunglasses made herein assures that most of sunglasses currently available to population are made of safe material.

Numerical modeling and experimental validation of thermoplastic composites induction welding

NASA Astrophysics Data System (ADS)

Palmieri, Barbara; Nele, Luigi; Galise, Francesco

2018-05-01

In this work, a numerical simulation and experimental test of the induction welding of continuous fibre-reinforced thermoplastic composites (CFRTPCs) was provided. The thermoplastic Polyamide 66 (PA66) with carbon fiber fabric was used. Using a dedicated software (JMag Designer), the influence of the fundamental process parameters such as temperature, current and holding time was investigated. In order to validate the results of the simulations, and therefore the numerical model used, experimental tests were carried out, and the temperature values measured during the tests were compared with the aid of an optical pyrometer, with those provided by the numerical simulation. The mechanical properties of the welded joints were evaluated by single lap shear tests.

Development of novel catalytically active polymer-metal-nanocomposites based on activated foams and textile fibers.

PubMed

Domènech, Berta; Ziegler, Kharla K; Carrillo, Fernando; Muñoz, Maria; Muraviev, Dimitri N; Macanás, Jorge

2013-05-16

In this paper, we report the intermatrix synthesis of Ag nanoparticles in different polymeric matrices such as polyurethane foams and polyacrylonitrile or polyamide fibers. To apply this technique, the polymer must bear functional groups able to bind and retain the nanoparticle ion precursors while ions should diffuse through the matrix. Taking into account the nature of some of the chosen matrices, it was essential to try to activate the support material to obtain an acceptable value of ion exchange capacity. To evaluate the catalytic activity of the developed nanocomposites, a model catalytic reaction was carried out in batch experiments: the reduction of p-nitrophenol by sodium borohydride.

Characterization of cobalt(II) chloride-modified condensation polyimide films

NASA Technical Reports Server (NTRS)

Rancourt, J. D.; Taylor, L. T.

1988-01-01

The effect of solvent extraction on the properties of cobalt(II) chloride-modified polyimide films was investigated. Solvent-cast films were prepared from solutions of cobalt chloride in poly(amide acid)/N,N-dimethylacetamide (DMAc) and were subsequently dried and cured in static air, forced air, or inert gas ovens with controlled humidity. The films were extracted by either of the three processes (1) soaking in a tray with distilled water at room temperature, (2) soxhlett extraction with distilled water, or (3) soxhell extraction with DMAc. Extraction with DMAc was found to remove both cobalt and chlorine from the films and to slightly increase bulk thermal stability and both surface resistivity and electrical resistivity.

A facile method to prepare dual-functional membrane for efficient oil removal and in situ reversible mercury ions adsorption from wastewater

NASA Astrophysics Data System (ADS)

Zhang, Qingdong; Liu, Na; Cao, Yingze; Zhang, Weifeng; Wei, Yen; Feng, Lin; Jiang, Lei

2018-03-01

In this work, a novel thiol covered polyamide (nylon 66) microfiltration membrane was fabricated by combining mussel-inspired chemistry and coupling reaction, which owns excellent dual-function that can simultaneously remove oil from water efficiently and adsorb the mercury ions contained in the wastewater reversibly. Such membrane exhibited high oil/water separation efficiency, outstanding mercury adsorption ability, and good stability. Moreover, it can be regenerated in nitric acid solution, and maintain its good adsorption performance. The as-prepared membrane showed great potentials for water purification to reduce the heavy metal ion pollution and complicated industrial oily wastewater and living wastewater.

Programmable DNA scaffolds for spatially-ordered protein assembly

NASA Astrophysics Data System (ADS)

Chandrasekaran, Arun Richard

2016-02-01

Ever since the notion of using DNA as a material was realized, it has been employed in the construction of complex structures that facilitate the assembly of nanoparticles or macromolecules with nanometer-scale precision. Specifically, tiles fashioned from DNA strands and DNA origami sheets have been shown to be suitable as scaffolds for immobilizing proteins with excellent control over their spatial positioning. Supramolecular assembly of proteins into periodic arrays in one or more dimensions is one of the most challenging aspects in the design of scaffolds for biomolecular investigations and macromolecular crystallization. This review provides a brief overview of how various biomolecular interactions with high degree of specificity such as streptavidin-biotin, antigen-antibody, and aptamer-protein interactions have been used to fabricate linear and multidimensional assemblies of structurally intact and functional proteins. The use of DNA-binding proteins as adaptors, polyamide recognition on DNA scaffolds and oligonucleotide linkers for protein assembly are also discussed.Ever since the notion of using DNA as a material was realized, it has been employed in the construction of complex structures that facilitate the assembly of nanoparticles or macromolecules with nanometer-scale precision. Specifically, tiles fashioned from DNA strands and DNA origami sheets have been shown to be suitable as scaffolds for immobilizing proteins with excellent control over their spatial positioning. Supramolecular assembly of proteins into periodic arrays in one or more dimensions is one of the most challenging aspects in the design of scaffolds for biomolecular investigations and macromolecular crystallization. This review provides a brief overview of how various biomolecular interactions with high degree of specificity such as streptavidin-biotin, antigen-antibody, and aptamer-protein interactions have been used to fabricate linear and multidimensional assemblies of structurally intact and functional proteins. The use of DNA-binding proteins as adaptors, polyamide recognition on DNA scaffolds and oligonucleotide linkers for protein assembly are also discussed. Dedicated to my advisor Ned Seeman on the occasion of his 70th birthday.

Study of the Effect of Nanoparticles and Surface Morphology on Reverse Osmosis and Nanofiltration Membrane Productivity

PubMed Central

Fang, Yuming; Duranceau, Steven J.

2013-01-01

To evaluate the significance of reverse osmosis (RO) and nanofiltration (NF) surface morphology on membrane performance, productivity experiments were conducted using flat-sheet membranes and three different nanoparticles, which included SiO2, TiO2 and CeO2. In this study, the productivity rate was markedly influenced by membrane surface morphology. Atomic force microscopy (AFM) analysis of membrane surfaces revealed that the higher productivity decline rates associated with polyamide RO membranes as compared to that of a cellulose acetate NF membrane was due to the inherent ridge-and-valley morphology of the active layer. The unique polyamide active layer morphology was directly related to the surface roughness, and was found to contribute to particle accumulation in the valleys causing a higher flux decline than in smoother membranes. Extended RO productivity experiments using laboratory grade water and diluted pretreated seawater were conducted to compare the effect that different nanoparticles had on membrane active layers. Membrane flux decline was not affected by particle type when the feed water was laboratory grade water. On the other hand, membrane productivity was affected by particle type when pretreated diluted seawater served as feed water. It was found that CeO2 addition resulted in the least observable flux decline, followed by SiO2 and TiO2. A productivity simulation was conducted by fitting the monitored flux data into a cake growth rate model, where the model was modified using a finite difference method to incorporate surface thickness variation into the analysis. The ratio of cake growth term (k1) and particle back diffusion term (k2) was compared in between different RO and NF membranes. Results indicated that k2 was less significant for surfaces that exhibited a higher roughness. It was concluded that the valley areas of thin-film membrane surfaces have the ability to capture particles, limiting particle back diffusion. PMID:24956946

Influence of non-covalent modification of multiwalled carbon nanotubes on the crystallization behaviour of binary blends of polypropylene and polyamide 6.

PubMed

Mukhopadhyay, Nabaneeta; Panwar, Ajay S; Kumar, Gulshan; Samajdar, I; Bhattacharyya, Arup R

2015-02-14

Blends of polypropylene (PP) and polyamide 6 (PA6) with multiwalled carbon nanotubes (MWNTs) were prepared using different processing strategies in a twin-screw micro-compounder. The effect of MWNTs on the crystallization behaviour of the PP phase and the PA6 phase of the blend has been investigated through non-isothermal crystallization studies by differential scanning calorimetric analysis. Furthermore, the effect of the addition of the compatibilizer (PP-g-MA) and the modification of MWNTs (m-MWNTs) with a non-covalent organic modifier (Li-salt of 6 amino hexanoic acid, Li-AHA) has also been studied in context to the crystallization behaviour of the PP and PA6 phase in the blend. The crystallization studies have indicated a significant increase in bulk crystallization temperature of the PP phase in the blend in the presence of MWNTs. Moreover, the formation of 'trans-lamellar crystalline' structure consisting of PA6 'trans-crystalline lamellae' on MWNTs surface was facilitated in the case of blends prepared via 'protocol 2' as compared to the corresponding blends prepared via 'protocol 1'. Wide angle X-ray diffraction analysis has showed the existence of a β-polymorph of the PP phase due to incorporation of the PA6 phase in the blend. Addition of MWNTs in the blends has facilitated further β-crystalline structure formation of the PP phase. In the presence of m-MWNTs, a higher β-fraction was observed in the PP phase as compared to the blend with pristine MWNTs. Addition of PP-g-MA has suppressed the β-phase formation in the PP phase in the blend. X-ray bulk texture analysis revealed that incorporation of PA6 as well as pristine/modified MWNTs has influenced the extent of orientation of the PP chains towards specific crystalline planes in various blend compositions of PP and PA6.

Size and Aging Effects on Antimicrobial Efficiency of Silver Nanoparticles Coated on Polyamide Fabrics Activated by Atmospheric DBD Plasma.

PubMed

Zille, Andrea; Fernandes, Margarida M; Francesko, Antonio; Tzanov, Tzanko; Fernandes, Marta; Oliveira, Fernando R; Almeida, Luís; Amorim, Teresa; Carneiro, Noémia; Esteves, Maria F; Souto, António P

2015-07-01

This work studies the surface characteristics, antimicrobial activity, and aging effect of plasma-pretreated polyamide 6,6 (PA66) fabrics coated with silver nanoparticles (AgNPs), aiming to identify the optimum size of nanosilver exhibiting antibacterial properties suitable for the manufacture of hospital textiles. The release of bactericidal Ag(+) ions from a 10, 20, 40, 60, and 100 nm AgNPs-coated PA66 surface was a function of the particles' size, number, and aging. Plasma pretreatment promoted both ionic and covalent interactions between AgNPs and the formed oxygen species on the fibers, favoring the deposition of smaller-diameter AgNPs that consequently showed better immediate and durable antimicrobial effects against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria. Surprisingly, after 30 days of aging, a comparable bacterial growth inhibition was achieved for all of the fibers treated with AgNPs <100 nm in size. The Ag(+) in the coatings also favored the electrostatic stabilization of the plasma-induced functional groups on the PA66 surface, thereby retarding the aging process. At the same time, the size-related ratio (Ag(+)/Ag(0)) of the AgNPs between 40 and 60 nm allowed for the controlled release of Ag(+) rather than bulk silver. Overall, the results suggest that instead of reducing the size of the AgNPs, which is associated with higher toxicity, similar long-term effects can be achieved with larger NPs (40-60 nm), even in lower concentrations. Because the antimicrobial efficiency of AgNPs larger than 30 nm is mainly ruled by the release of Ag(+) over time and not by the size and number of the AgNPs, this parameter is crucial for the development of efficient antimicrobial coatings on plasma-treated surfaces and contributes to the safety and durability of clothing used in clinical settings.

Exploration of polyamide structure-property relationships by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

PubMed

Barrère, Caroline; Rejaibi, Majed; Curat, Aurélien; Hubert-Roux, Marie; Lavanant, Hélène; Afonso, Carlos; Kebir, Nasreddine; Desilles, Nicolas; Lecamp, Laurence; Burel, Fabrice; Loutelier-Bourhis, Corinne

2014-08-15

Polyamides (PA) are among the most used classes of polymers because of their attractive properties. Depending on the nature and proportion of the co-monomers used for their synthesis, they can exhibit a very large range of melting temperatures (Tm ). This study aims at the correlation of data from mass spectrometry (MS) with differential scanning calorimetry (DSC) and X-ray diffraction analyses to relate molecular structure to physical properties such as melting temperature, enthalpy change and crystallinity rate. Six different PA copolymers with molecular weights around 3500 g mol(-1) were synthesized with varying proportions of different co-monomers (amino-acid AB/di-amine AA/di-acid BB). Their melting temperature, enthalpy change and crystallinity rate were measured by DSC and X-ray diffraction. Their structural characterization was carried out by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Because of the poor solubility of PA, a solvent-free sample preparation strategy was used with 2,5-dihydroxybenzoic acid (2,5-DHB) as the matrix and sodium iodide as the cationizing agent. The different proportions of the repeating unit types led to the formation of PA with melting temperatures ranging from 115°C to 185°C. The structural characterization of these samples by MALDI-TOF-MS revealed a collection of different ion distributions with different sequences of repeating units (AA, BB; AB/AA, BB and AB) in different proportions according to the mixture of monomers used in the synthesis. The relative intensities of these ion distributions were related to sample complexity and structure. They were correlated to DSC and X-ray results, to explain the observed physical properties. The structural information obtained by MALDI-TOF-MS provided a better understanding of the variation of the PA melting temperature and established a structure-properties relationship. This work will allow future PA designs to be monitored. Copyright © 2014 John Wiley & Sons, Ltd.

Hesperetin-loaded lipid-core nanocapsules in polyamide: a new textile formulation for topical drug delivery

PubMed Central

Menezes, Paula dos Passos; Frank, Luiza Abrahão; Lima, Bruno dos Santos; de Carvalho, Yasmim Maria Barbosa Gomes; Serafini, Mairim Russo; Quintans-Júnior, Lucindo José; Pohlmann, Adriana Raffin; Guterres, Sílvia Stanisçuaski; Araújo, Adriano Antunes de Souza

2017-01-01

Chronic venous insufficiency is characterized by chronic reflux disorder of blood from the peripheral to the central vein, with subsequent venous hypertension and resulting changes in the skin. Traditionally, nonsurgical treatments relied on the use of compression therapy, and more recently a variety of flavonoids have been shown to have positive effects. There have also been developments of more effective drug delivery systems using various textiles and nanotechnology to provide new therapeutic options. Our objective was to use nanotechnology to develop a new formulation containing hesperetin (Hst), a substance not previously used in the treatment of chronic venous insufficiency, impregnated into textile fibers as a possible alternative treatment of venous diseases. We prepared the nanocapsules using the interfacial deposition of preformed polymer method with an Hst concentration of 0.5 mg/mL and then characterized the size and distribution of particles. To quantify the Hst in the samples, we developed an analytical method using high-performance liquid chromatography. Studies of encapsulation efficiency (98.81%±0.28%), microscopy, drug release (free-Hst: 104.96%±12.83%; lipid-core nanocapsule-Hst: 69.90%±1.33%), penetration/permeation, drug content (0.46±0.01 mg/mL) and the effect of washing the textile after drug impregnation were performed as part of the study. The results showed that nanoparticles of a suitable size and distribution with controlled release of the drug and penetration/permeation into the skin layers were achieved. Furthermore, it was established that polyamide was able to hold more of the drug, with a 2.54 times higher content than the cotton fiber; after one wash and after five washes, this relation was 2.80 times higher. In conclusion, this is a promising therapeutic alternative to be further studied in clinical trials. PMID:28352176

Fabrication of Polyimide-Matrix/Carbon and Boron-Fiber Tape

NASA Technical Reports Server (NTRS)

Belvin, Harry L.; Cano, Roberto J.; Treasure, Monte; Shahood, Thomas W.

2007-01-01

The term HYCARB denotes a hybrid composite of polyimide matrices reinforced with carbon and boron fibers. HYCARB and an improved process for fabricating dry HYCARB tapes have been invented in a continuing effort to develop lightweight, strong composite materials for aerospace vehicles. Like other composite tapes in this line of development, HYCARB tapes are intended to be used to build up laminated structures having possibly complex shapes by means of automated tow placement (ATP) - a process in which a computer-controlled multiaxis machine lays down prepreg tape or tows. The special significance of the present process for making dry HYCARB for ATP is that it contributes to the reduction of the overall cost of manufacturing boron-reinforced composite-material structures while making it possible to realize increased compression strengths. The present process for making HYCARB tapes incorporates a "wet to dry" process developed previously at Langley Research Center. In the "wet to dry" process, a flattened bundle of carbon fiber tows, pulled along a continuous production line between pairs of rollers, is impregnated with a solution of a poly(amide acid) in N-methyl-2-pyrrolidinone (NMP), then most of the NMP is removed by evaporation in hot air. In the present case, the polyamide acid is, more specifically, that of LaRC. IAX (or equivalent) thermoplastic polyimide, and the fibers are, more specifically, Manganite IM7 (or equivalent) polyacrylonitrile- based carbon filaments that have a diameter of 5.2 m and are supplied in 12,000-filament tows. The present process stands in contrast to a prior process in which HYCARB tape was made by pressing boron fibers into the face of a wet carbon-fiber/ poly(amide acid) prepreg tape . that is, a prepreg tape from which the NMP solvent had not been removed. In the present process, one or more layer(s) of side-by-side boron fibers are pressed between dry prepreg tapes that have been prepared by the aforementioned gwet to dry h process. The multilayer tape is then heated to imidize the matrix material and remove most of the remaining solvent, and is pressed to consolidate the multiple layers into a dense tape. For tests, specimens of HYCARB tapes and laminated composite panels made from HYCARB tape were prepared as follows: HYCARB tapes were fabricated as described above. Each panel was made by laying down ten layers of tape, containing, variously, one, two, or three boron-fiber plies and the remainder carbon- fiber-only plies (see figure). Each panel was made by laying down ten layers of tape. Each panel was then cured by heating to a temperature of 225 C for 15 minutes, then pressing at 200 psi (A1.4 MPa) while heating to 371 C, holding at 371 C for 1 hour, then continuing to hold pressure during cooling. Control specimens that were otherwise identical except that they did not contain boron fibers also were prepared. In room-temperature flexural tests, the HYCARB specimens performed comparably to the control specimens; in room-temperature, open-hole compression tests, the HYCARB specimens performed slightly better, by amounts that increased with boron content.

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

Kim, Sang-Woo; Seong, Dong Gi; Yi, Jin-Woo

In order to manufacture carbon fiber-reinforced polyamide-6 (PA-6) composite, we optimized the reactive processing system. The in-situ anionic ring-opening polymerization of ε-caprolactam was utilized with proper catalyst and initiator for PA-6 matrix. The mechanical properties such as tensile strength, inter-laminar shear strength and compressive strength of the produced carbon fiber-reinforced PA-6 composite were measured, which were compared with the corresponding scanning electron microscope (SEM) images to investigate the polymer properties as well as the interfacial interaction between fiber and polymer matrix. Furthermore, kinetics of in-situ anionic ring-opening polymerization of ε-caprolactam will be discussed in the viewpoint of increasing manufacturing speedmore » and interfacial bonding between PA-6 matrix and carbon fiber during polymerization.« less

Polymer membranes as separators for supercapacitors

NASA Astrophysics Data System (ADS)

Szubzda, Bronisław; Szmaja, Aleksandra; Ozimek, Mariusz; Mazurkiewicz, Sławomir

2014-12-01

The purpose of the studies described was to examine the influence of low-energy plasma modification of polyamide and polypropylene polymer nonwoven fabrics on the usable properties of supercapacitors when using these fabrics as the separator material. To achieve this goal the following investigations were carried out: testing the time required for electrolyte saturation of separators and the conductivity of the electrolyte contained in the separator, as well as electrochemical examinations of supercapacitor models in which the modified fabric separators were used. The tests conducted fully confirm the usability of this modification for cleaning the surface and improving the wettability of separators by the electrolyte, which in turn results in a significant decrease of the internal resistance of the supercapacitor, thus increasing the usable power of the device.

Improved photocatalytic degradation of Orange G using hybrid nanofibers

NASA Astrophysics Data System (ADS)

Ledwaba, Mpho; Masilela, Nkosiphile; Nyokong, Tebello; Antunes, Edith

2017-05-01

Functionalised electrospun polyamide-6 (PA-6) nanofibres incorporating gadolinium oxide nanoparticles conjugated to zinc tetracarboxyphenoxy phthalocyanine (ZnTCPPc) as the sensitizer were prepared for the photocatalytic degradation of Orange G. Fibres incorporating the phthalocyanine alone or a mixture of the nanoparticles and phthalocyanine were also generated. The singlet oxygen-generating ability of the sensitizer was shown to be maintained within the fibre mat, with the singlet oxygen quantum yields increasing upon incorporation of the magnetic nanoparticles. Consequently, the rate of the photodegradation of Orange G was observed to increase with an increase in singlet oxygen quantum yield. A reduction in the half-lives for the functionalised nanofibres was recorded in the presence of the magnetic nanoparticles, indicating an improvement in the efficiency of the degradation process.

Development of multi-layer plastic fuel tanks for Nissan research vehicle-II

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

Kurihara, Y.; Nakazawa, K.; Ohashi, K.

1987-01-01

Plastic fuel tanks are light in weight and rustproof, and have good design flexibility. For those currently in use, however, which are made of mono-layer high-density polyethylene, fuel permeability is too high to meet U.S. evaporative emission standards, which are stricter than those in Japan or the EEC. For minimize fuel permeation, the formation of a barrier layer of polyamide resin by multi-layer (three-resin five-layer) blow molding is considered more promising than sulphonation or fluorination treatment of the polyethylene resin. This paper describes the fuel permeation mechanism, then outlines the development of a multi-layer plastic fuel tank, and discusses itsmore » structural features and the development of resins.« less

Mutagenicity studies of urine and faecal samples from rats treated orally with the food colourings Brown FK and Red 2G.

PubMed

Edwards, C N; Combes, R D

1984-08-01

Urine and faecal extracts from rats given Brown FK or Red 2G orally (800 mg/kg body weight) were investigated for mutagenicity. Extracts were subjected to liquid fluctuation and plate incorporation assays with Salmonella typhimurium strains TA98 and TA100 in the presence and absence of liver microsomes and/or a beta-glucuronidase-sulphatase preparation. Urine from Red 2G-treated rats only exhibited direct activity when coloured fractions from polyamide-column concentrates were tested with TA100. All other urines, as well as aqueous and ether faecal extracts from animals receiving either colouring, were no more mutagenic than the respective control extracts obtained from the same animals prior to dosing.

Energy efficiency in nanoscale synthesis using nanosecond plasmas.

PubMed

Pai, David Z; Ken Ostrikov, Kostya; Kumar, Shailesh; Lacoste, Deanna A; Levchenko, Igor; Laux, Christophe O

2013-01-01

We report a nanoscale synthesis technique using nanosecond-duration plasma discharges. Voltage pulses 12.5 kV in amplitude and 40 ns in duration were applied repetitively at 30 kHz across molybdenum electrodes in open ambient air, generating a nanosecond spark discharge that synthesized well-defined MoO₃ nanoscale architectures (i.e. flakes, dots, walls, porous networks) upon polyamide and copper substrates. No nitrides were formed. The energy cost was as low as 75 eV per atom incorporated into a nanostructure, suggesting a dramatic reduction compared to other techniques using atmospheric pressure plasmas. These findings show that highly efficient synthesis at atmospheric pressure without catalysts or external substrate heating can be achieved in a simple fashion using nanosecond discharges.

An Automated High-Throughput System to Fractionate Plant Natural Products for Drug Discovery

PubMed Central

Tu, Ying; Jeffries, Cynthia; Ruan, Hong; Nelson, Cynthia; Smithson, David; Shelat, Anang A.; Brown, Kristin M.; Li, Xing-Cong; Hester, John P.; Smillie, Troy; Khan, Ikhlas A.; Walker, Larry; Guy, Kip; Yan, Bing

2010-01-01

The development of an automated, high-throughput fractionation procedure to prepare and analyze natural product libraries for drug discovery screening is described. Natural products obtained from plant materials worldwide were extracted and first prefractionated on polyamide solid-phase extraction cartridges to remove polyphenols, followed by high-throughput automated fractionation, drying, weighing, and reformatting for screening and storage. The analysis of fractions with UPLC coupled with MS, PDA and ELSD detectors provides information that facilitates characterization of compounds in active fractions. Screening of a portion of fractions yielded multiple assay-specific hits in several high-throughput cellular screening assays. This procedure modernizes the traditional natural product fractionation paradigm by seamlessly integrating automation, informatics, and multimodal analytical interrogation capabilities. PMID:20232897

Molecular dynamics study of a polymeric reverse osmosis membrane.

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

Harder, E.; Walters, D. E.; Bodnar, Y. D.

2009-07-30

Molecular dynamics (MD) simulations are used to investigate the properties of an atomic model of an aromatic polyamide reverse osmosis membrane. The monomers forming the polymeric membrane are cross-linked progressively on the basis of a heuristic distance criterion during MD simulations until the system interconnectivity reaches completion. Equilibrium MD simulations of the hydrated membrane are then used to determine the density and diffusivity of water within the membrane. Given a 3 MPa pressure differential and a 0.125 {micro}m width membrane, the simulated water flux is calculated to be 1.4 x 10{sup -6} m/s, which is in fair agreement with anmore » experimental flux measurement of 7.7 x 10{sup -6} m/s.« less

Polymer-Supported Raney Nickel Catalysts for Sustainable Reduction Reactions.

PubMed

Jiang, Haibin; Lu, Shuliang; Zhang, Xiaohong; Dai, Wei; Qiao, Jinliang

2016-06-25

Green is the future of chemistry. Catalysts with high selectivity are the key to green chemistry. Polymer-supported Raney catalysts have been found to have outstanding performance in the clean preparation of some chemicals. For example, a polyamide 6-supported Raney nickel catalyst provided a 100.0% conversion of n-butyraldehyde without producing any detectable n-butyl ether, the main byproduct in industry, and eliminated the two main byproducts (isopropyl ether and methyl-iso-butylcarbinol) in the hydrogenation of acetone to isopropanol. Meanwhile, a model for how the polymer support brought about the elimination of byproducts is proposed and confirmed. In this account the preparation and applications of polymer-supported Raney catalysts along with the corresponding models will be reviewed.

Fully electronic urine dipstick probe for combinatorial detection of inflammatory biomarkers

PubMed Central

Kamakoti, Vikramshankar; Kinnamon, David; Choi, Kang Hyeok; Jagannath, Badrinath; Prasad, Shalini

2018-01-01

Aim: An electrochemical urine dipstick probe biosensor has been demonstrated using molybdenum electrodes on nanoporous polyamide substrate for the quantitative detection of two inflammatory protein biomarkers, CRP and IL-6. Materials & methods: The electrode interface was characterized using ζ-potential and Fourier transform infrared spectroscopy. Detection of biomarkers was demonstrated by measuring impedance changes associated with the dose concentrations of the two biomarkers. A proof of feasibility of point-of-care implementation of the biosensor was demonstrated using a portable electronics platform. Results & conclusion: Limit of detection of 1 pg/ml was achieved for CRP and IL-6 in human urine and synthetic urine buffers. The developed portable hardware demonstrated close correlation with benchtop equipment results. PMID:29796304

Synthesis and development of low cost, high temperature N-arylene polybenzimidazole foam material

NASA Technical Reports Server (NTRS)

Harrison, E. S.

1975-01-01

Polymer (and foam) studies followed two basic routes: (1) formation of high molecular weight uncyclized polyamide followed by subsequent fusion and cyclodehydration to yield NABI (foam) and (2) polymer and foam formation by reaction of diphenyl esters (or anhydrides) with the tetramine. The latter route was found much more attractive since considerable versatility in both basic polymer structure and crosslinkability is achievable. Preliminary studies on BAB, phthalic anhydride (PA), and 3, 3 (prime), 4, 4(prime) benzo pheno netetracarboxylic acid dianhydride (BTDA) as crosslinked polymer precursors were conducted. Nonmelting rigid char forming foams with densities as low as 2.7 lb/cubic ft. were achieved. The program was successful in the preparation of a potentially low cost, low density, high char yield, high temperature foam material.

Imidazopyridine/Pyrrole and hydroxybenzimidazole/pyrrole pairs for DNA minor groove recognition.

PubMed

Renneberg, Dorte; Dervan, Peter B

2003-05-14

The DNA binding properties of fused heterocycles imidazo[4,5-b]pyridine (Ip) and hydroxybenzimidazole (Hz) paired with pyrrole (Py) in eight-ring hairpin polyamides are reported. The recognition profile of Ip/Py and Hz/Py pairs were compared to the five-membered ring pairs Im/Py and Hp/Py on a DNA restriction fragment at four 6-base pair recognition sites which vary at a single position 5'-TGTNTA-3', where N = G, C, T, A. The Ip/Py pair distinguishes G.C from C.G, T.A, and A.T, and the Hz/Py pair distinguishes T.A from A.T, G.C, and C.G, affording a new set of heterocycle pairs to target the four Watson-Crick base pairs in the minor groove of DNA.

Joining of aluminum sheet and glass fiber reinforced polymer using extruded pins

NASA Astrophysics Data System (ADS)

Conte, Romina; Buhl, Johannes; Ambrogio, Giuseppina; Bambach, Markus

2018-05-01

The present contribution proposes a new approach for joining sheet metal and fiber reinforced composites. The joining process draws upon a Friction Stir Forming (FSF) process, which is performed on the metal sheet to produce slender pins. These pins are used to pierce through the composite. Joining is complete by forming a locking head out of the part if the pin sticks out of the composite. Pins of different diameters and lengths were produced from EN AW-1050 material, which were joined to glass fiber reinforced polyamide-6. The strength of the joint has been experimentally tested in order to understand the effect of the process temperature on the pins strength and therefore on the joining. The results demonstrate the feasibility of this new technique, which uses no excess material.

Energy efficiency in nanoscale synthesis using nanosecond plasmas

PubMed Central

Pai, David Z.; (Ken) Ostrikov, Kostya; Kumar, Shailesh; Lacoste, Deanna A.; Levchenko, Igor; Laux, Christophe O.

2013-01-01

We report a nanoscale synthesis technique using nanosecond-duration plasma discharges. Voltage pulses 12.5 kV in amplitude and 40 ns in duration were applied repetitively at 30 kHz across molybdenum electrodes in open ambient air, generating a nanosecond spark discharge that synthesized well-defined MoO3 nanoscale architectures (i.e. flakes, dots, walls, porous networks) upon polyamide and copper substrates. No nitrides were formed. The energy cost was as low as 75 eV per atom incorporated into a nanostructure, suggesting a dramatic reduction compared to other techniques using atmospheric pressure plasmas. These findings show that highly efficient synthesis at atmospheric pressure without catalysts or external substrate heating can be achieved in a simple fashion using nanosecond discharges. PMID:23386976

Identification of novel antilipogenic agents targeting fatty acid biosynthesis through structure-based virtual screening.

PubMed

Soulère, Laurent; Alix, Pascaline M; Croze, Marine L; Soulage, Christophe O

2018-04-10

An Asinex Gold Platinium chemical library subset of 12 055 compounds was screened employing docking simulations in the active site of the human FAS KS domain. Among them, 13 compounds were further evaluated for their ability to inhibit fatty acid biosynthesis. Four compounds were found to be active in particular ASN05064661 and ASN05374526 with IC50 values of 6.6 and 10.5 μm, respectively. A binding mode study was further conducted with these two compounds structurally related to benzene sulfonamide and aromatic polyamide. This study showed that they fit tightly with the active site with several interactions, notably with the key residues Cys161, His293, and His331. © 2018 John Wiley & Sons A/S.

Ion-conducting membranes

DOEpatents

Masel, Richard L.; Chen, Qingmei; Liu, Zengcai; Kutz, Robert

2016-06-21

An ion conducting polymeric composition mixture comprises a copolymer of styrene and vinylbenzyl-R.sub.s. R.sub.s is selected from the group consisting of imidazoliums and pyridiniums. The composition contains 10%-90% by weight of vinylbenzyl-R.sub.s. The composition can further comprise a polyolefin comprising substituted polyolefins, a polymer comprising cyclic amine groups, a polymer comprising at least one of a phenylene group and a phenyl group, a polyamide, and/or the reaction product of a constituent having two carbon-carbon double bonds. The composition can be in the form of a membrane. In a preferred embodiment, the membrane is a Helper Membrane that increases the faradaic efficiency of an electrochemical cell into which the membrane is incorporated, and also allows product formation at lower voltages than in cells without the Helper Membrane.

Health hazards in the production and processing of some fibers, resins, and plastics in Bulgaria.

PubMed Central

Spassovski, M

1976-01-01

Results of the toxicological studies of working conditions, general and professional morbidity, and complex examinations carried out on workers engaged in the production of polyamides, polyacrylonitrile fibers, polyester fibers and poly (vinyl chloride) resin, urea-formaldehyde glue, glass fibre materials and polyurethane resins are given. An extremely high occupational hazard for workers in the production of poly (vinyl chloride) resin and porous materials from polyurethane resins and urea-formaldehyde glue has been established. Cases of vinyl chloride disease, poisoning from formaldehyde, isocyanates, and styrene were noted. Prophylactic measures were taken in Bulgaria to lessen the occupational hazard in the productions as set forth included limitation of the work day to 6 hr, free food, additional bonus and leave, and annual physical examinations of workers. PMID:1026405

Bio-based production of monomers and polymers by metabolically engineered microorganisms.

PubMed

Chung, Hannah; Yang, Jung Eun; Ha, Ji Yeon; Chae, Tong Un; Shin, Jae Ho; Gustavsson, Martin; Lee, Sang Yup

2015-12-01

Recent metabolic engineering strategies for bio-based production of monomers and polymers are reviewed. In the case of monomers, we describe strategies for producing polyamide precursors, namely diamines (putrescine, cadaverine, 1,6-diaminohexane), dicarboxylic acids (succinic, glutaric, adipic, and sebacic acids), and ω-amino acids (γ-aminobutyric, 5-aminovaleric, and 6-aminocaproic acids). Also, strategies for producing diols (monoethylene glycol, 1,3-propanediol, and 1,4-butanediol) and hydroxy acids (3-hydroxypropionic and 4-hydroxybutyric acids) used for polyesters are reviewed. Furthermore, we review strategies for producing aromatic monomers, including styrene, p-hydroxystyrene, p-hydroxybenzoic acid, and phenol, and propose pathways to aromatic polyurethane precursors. Finally, in vivo production of polyhydroxyalkanoates and recombinant structural proteins having interesting applications are showcased. Copyright © 2015 Elsevier Ltd. All rights reserved.

Thermochemical characterization of polymers for improved fire safety

NASA Technical Reports Server (NTRS)

Lerner, N. R.

1977-01-01

Apparatus has been constructed for studying the thermal decomposition of polymers as a function of temperature. Such data is needed to evaluate the toxic threat presented by polymeric materials under fire conditions such as the smoldering fire of the type that occurs in closed areas such as coat closets in which anaerobic decomposition of polymers occurs. The apparatus allows the products of thermal decomposition to be collected and analyzed by infrared spectrometry and mass spectrometry. Data obtained from dog hair, an aromatic polyamide, polyphenylene sulfide, and polybenzimidazole are presented. It was found that significant amounts of toxic gas were evolved from dog hair at temperatures as low as 250 C, while temperatures in excess of 500 C were necessary in order for the evolution of toxic gas from the aromatic polymers to become significant.

[Membrane technologies in medicine and ecology].

PubMed

Makarov, D A; Malyshev, V V; Kononova, S V

2010-01-01

The paper considers the state-of-the-art of membrane technologies, as applied to the needs of medicine and ecology, the major benefits of membranes for microfiltration and ultrafiltration, and perspectives for the application of new membranes based on new materials. A number of membranes based on aromatic polyamide imides (PAs) have been investigated using rotavirus models. Due to the good solubility of PAs in amide solvents, their based asymmetric membranes can be formed in one step, by applying a water setting bath. The one-stage procedure developed at the Institute of High Molecular Compounds, Russian Academy of Sciences, for the synthesis of aromatic PAs allows one to prepare polymers with required viscosity and strength characteristics. This gives rise to a membrane as porous films of digitiform morphology and asymmetric porous structure.

Polyamides based on the renewable monomer, 1,13-tridecane diamine I: synthesis and characterization of nylon 13,T

DOE PAGES

He, Jie; Samanta, Satyabrata; Selvakumar, Sermadurai; ...

2013-06-01

Nylon 13,T was successfully synthesized and chemical composition, thermal properties, crystal structure, and moisture absorption characterized. Melting temperature and glass transition temperature were determined to be 263 °C and 90 °C, respectively, while the equilibrium melting temperature was determined to be 289 °C. Characterization of the crystallization kinetics showed that nylon 13,T exhibits very fast crystallization compared to the industrially important nylons, nylon 6 and nylon 6,6. In addition, the moisture absorption of nylon 13,T was dramatically lower than nylon 6 and nylon 6,6 which is consistent with the much lower amide content of nylon 13,T. The crystal structure wasmore » determined to be pseudohexagonal.« less

Diagnostics of N2 Ar plasma mixture excited in a 13.56 MHz hollow cathode discharge system: application to remote plasma treatment of polyamide surface

NASA Astrophysics Data System (ADS)

Saloum, S.; Naddaf, M.; Alkhaled, B.

2008-02-01

N2-x% Ar plasma gas mixture, generated in a hollow cathode RF discharge system, has been characterized by both optical emission spectroscopy (OES) and double Langmuir probe, as a function of experimental parameters: total pressure (5-33 Pa), and different fractions of argon (7 <= x <= 80), at a constant applied RF power of 300 W. N2 dissociation degree has been investigated qualitatively by both the actinometry method and the ratio I_N/I_{N_2} of the atomic nitrogen line emission intensity at 672.3 nm to the vibrational band (0-0) of the N2 second positive system at 337.1 nm. Both methods showed that the increase in argon fraction enhances the dissociation of N2, with a maximum at x = 50 for the pressure of 5 Pa, although the two methods give two opposite trends as a function of total pressure. Spectroscopic measurements showed that the vibrational temperature of the N2 second positive system increases with both argon fraction and total pressure increase, it lies between 4900 and 12 300 K. Langmuir probe measurements showed that, in the remote zone, the electron temperature falls in the range 1.57-1.75 eV, the N_{2}^{+} density varies between 5 × 109 and 1.4 × 1010 cm-3 and that both the plasma ionization degree and electron temperature increase towards the source. In addition, the process of plasma-polyamide (PA) surface interaction, in the remote plasma zone, has been studied through OES analysis during plasma treatment of PA to monitor the possible emissions due to the polymer etching. An increase in atomic nitrogen line (672.3 nm) intensity is obtained, atomic carbon line (833.52 nm) and the band emission (0-0) from the CN (B 2Σ+-X 2Σ+) violet system were observed. The PA surface modification has been confirmed through the improvement of its hydrophilic character as the water contact angle measured after the plasma treatment significantly decreased.

Migration of plasticizers from poly(vinyl chloride) and multilayer infusion bags using selective extraction and GC-MS.

PubMed

Haned, Zohra; Moulay, Saad; Lacorte, Silvia

2018-04-12

Flexible poly(vinyl chloride) (PVC) is widely used in the pharmaceutical industry for the manufacture of medical devices (tubes, probes, bags, primary packaging, etc.). The objective of the present study was to develop a procedure to evaluate the migration potential of nine plastic additives in aqueous infusion bags (NaCl 0.9% and glucose 5%): five phthalates, one adipate, two alkylphenols, and benzophenone. Two types of materials were analyzed: (i) new and outdated plasticized PVC (containing 40% of diethylhexyl phthalate DEHP); and (ii) tri-laminate polyethylene-polyamide-polypropylene, a multilayer material presumably exempt from DEHP. In addition, we evaluated the migration of plasticizers from PVC raw materials (film and grain) under controlled conditions to compare the migration levels according to Regulation 2011/10. Solid phase extraction and liquid-liquid extraction with gas-chromatography coupled to mass spectrometry were used in all tests. The migration of DEHP in PVC grain exceeded the maximum regulated level of 5000 μg/kg, whereas the levels were much lower in films. In new PVC bags, DEHP was the only compound detected at 4.31 ± 0.5 μg/L in NaCl 0.9% and 4.29 ± 0.25 μg/L in glucose 5% serums, whereas the levels increased 10 times in three-year shelf-life bags. In multilayer bags, DEHP was not found but instead, two plasticizers were detected namely dibuthylphthalate (DBP) and diethylphthalate (DEP) at 0.7 ± 0.1 μg/L and 4.14 ± 0.6 μg/L, respectively. These plasticizers are not mentioned as additives allowed in materials intended for parenteral use (European Pharmacopoeia 8.0, 3.1.5. and 3.1.6.). Caprolactam was tentatively identified and could have stemmed from the polyamide of the multilayer composite. The levels of phthalates remained low but not negligible and might constitute a risk to public health in the case of reiterative infusions. Copyright © 2018. Published by Elsevier B.V.

Selective CO2 Sequestration with Monolithic Bimodal Micro/Macroporous Carbon Aerogels Derived from Stepwise Pyrolytic Decomposition of Polyamide-Polyimide-Polyurea Random Copolymers.

PubMed

Saeed, Adnan M; Rewatkar, Parwani M; Majedi Far, Hojat; Taghvaee, Tahereh; Donthula, Suraj; Mandal, Chandana; Sotiriou-Leventis, Chariklia; Leventis, Nicholas

2017-04-19

Polymeric aerogels (PA-xx) were synthesized via room-temperature reaction of an aromatic triisocyanate (tris(4-isocyanatophenyl) methane) with pyromellitic acid. Using solid-state CPMAS 13 C and 15 N NMR, it was found that the skeletal framework of PA-xx was a statistical copolymer of polyamide, polyurea, polyimide, and of the primary condensation product of the two reactants, a carbamic-anhydride adduct. Stepwise pyrolytic decomposition of those components yielded carbon aerogels with both open and closed microporosity. The open micropore surface area increased from <15 m 2 g -1 in PA-xx to 340 m 2 g -1 in the carbons. Next, reactive etching at 1,000 °C with CO 2 opened access to the closed pores and the micropore area increased by almost 4× to 1150 m 2 g -1 (out of 1750 m 2 g -1 of a total BET surface area). At 0 °C, etched carbon aerogels demonstrated a good balance of adsorption capacity for CO 2 (up to 4.9 mmol g -1 ), and selectivity toward other gases (via Henry's law). The selectivity for CO 2 versus H 2 (up to 928:1) is suitable for precombustion fuel purification. Relevant to postcombustion CO 2 capture and sequestration (CCS), the selectivity for CO 2 versus N 2 was in the 17:1 to 31:1 range. In addition to typical factors involved in gas sorption (kinetic diameters, quadrupole moments and polarizabilities of the adsorbates), it is also suggested that CO 2 is preferentially engaged by surface pyridinic and pyridonic N on carbon (identified with XPS) in an energy-neutral surface reaction. Relatively high uptake of CH 4 (2.16 mmol g -1 at 0 °C/1 bar) was attributed to its low polarizability, and that finding paves the way for further studies on adsorption of higher (i.e., more polarizable) hydrocarbons. Overall, high CO 2 selectivities, in combination with attractive CO 2 adsorption capacities, low monomer cost, and the innate physicochemical stability of carbon render the materials of this study reasonable candidates for further practical consideration.

Multifunctional cationic polyurethanes designed for non-viral cancer gene therapy.

PubMed

Cheng, Jian; Tang, Xin; Zhao, Jie; Shi, Ting; Zhao, Peng; Lin, Chao

2016-01-01

Nano-polyplexes from bioreducible cationic polymers have a massive promise for cancer gene therapy. However, the feasibility of cationic polyurethanes for non-viral gene therapy is so far not well studied. In this work, a linear cationic polyurethane containing disulfide bonds, urethane linkages and protonable tertiary amino groups was successfully generated by stepwise polycondensation reaction between 2,2'-dithiodiethanol bis(p-nitrophenyl carbonate) and 1,4-bis(3-aminopropyl)piperazine (BAP). We confirmed that the cationic polyurethane (denoted as PUBAP) displayed superior gene delivery properties to its cationic polyamide analogue, thus causing higher in vitro transfection efficiency in MCF-7 and SKOV-3 cells. Besides, further folate-PEGylation and hydrophobic deoxycholic acid (DCA) conjugation to amino-containing PUBAP can be conducted to afford multifunctional polyurethane gene delivery system. After optimization, folate-decorated nano-polyplexes from the PUBAP conjugated with 8 folate-PEG chains and 12 DCA residues exhibited superb colloidal stability under physiological conditions, and performed rapid uptake via folate receptor-mediated endocytosis, efficient intracellular gene release and nucleus translocation into SKOV-3 cells in vitro and in vivo. Importantly, PUBAP based polyplexes possess low cytotoxicity as a result of PUBAP biodegradability. Therefore, marked growth inhibition of SKOV-3 tumor xenografted in Balb/c nude mice was achieved with negligible side effects on the mouse health after intravenous administration of PUBAP based polyplexes with a therapeutic plasmid encoding for TNF-related apoptosis-inducing ligand. This work provides a new insight into biomedical application of bio-responsive polyurethanes for cancer therapy. In this study, we have confirmed that disulfide-based cationic polyurethane presents a new non-viral vector for gene transfer and cancer gene therapy. The significance of this work includes: (1) design and synthesis of a group of novel disulfide-based cationic polyurethane by non-isocyanate chemistry; (2) comparative study of transfection activity between cationic polyurethanes and cationic polyamides; (3) feasibility of bioreducible cationic polyurethanes for in vivo cancer gene therapy. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Evaluation of anterior cervical reconstruction with titanium mesh cages versus nano-hydroxyapatite/polyamide66 cages after 1- or 2-level corpectomy for multilevel cervical spondylotic myelopathy: a retrospective study of 117 patients.

PubMed

Zhang, Yuan; Quan, Zhengxue; Zhao, Zenghui; Luo, Xiaoji; Tang, Ke; Li, Jie; Zhou, Xu; Jiang, Dianming

2014-01-01

To retrospectively compare the efficacy of the titanium mesh cage (TMC) and the nano-hydroxyapatite/polyamide66 cage (n-HA/PA66 cage) for 1- or 2-level anterior cervical corpectomy and fusion (ACCF) to treat multilevel cervical spondylotic myelopathy (MCSM). A total of 117 consecutive patients with MCSM who underwent 1- or 2-level ACCF using a TMC or an n-HA/PA66 cage were studied retrospectively at a mean follow-up of 45.28 ± 12.83 months. The patients were divided into four groups according to the level of corpectomy (1- or 2-level corpectomy) and cage type used (TMC or n-HA/PA66 cage). Clinical and radiological parameters were used to evaluate outcomes. At the one-year follow-up, the fusion rate in the n-HA/PA66 group was higher, albeit non-significantly, than that in the TMC group for both 1- and 2-level ACCF, but the fusion rates of the procedures were almost equal at the final follow-up. The incidence of cage subsidence at the final follow-up was significantly higher in the TMC group than in the n-HA/PA66 group for the 1-level ACCF (24% vs. 4%, p = 0.01), and the difference was greater for the 2-level ACCF between the TMC group and the n-HA/PA66 group (38% vs. 5%, p = 0.01). Meanwhile, a much greater loss of fused height was observed in the TMC group compared with the n-HA/PA66 group for both the 1- and 2-level ACCF. All four groups demonstrated increases in C2-C7 Cobb angle and JOA scores and decreases in VAS at the final follow-up compared with preoperative values. The lower incidence of cage subsidence, better maintenance of the height of the fused segment and similar excellent bony fusion indicate that the n-HA/PA66 cage may be a superior alternative to the TMC for cervical reconstruction after cervical corpectomy, in particular for 2-level ACCF.

Process for the manufacture of low density bis-maleimide-carbon microballoon composites

NASA Technical Reports Server (NTRS)

Kourtides, Demetrius A. (Inventor); Parker, John A. (Inventor)

1980-01-01

A process for the preparation of composite laminate structures of glass cloth preimpregnated with polybismaleimide resin and adhered to a polybismaleimide-glass or aromatic polyamide paper honeycomb cell structure filled or partially filled with a syntactic foam consisting of a mixture of bismaleimide resin and carbon microballoons. The carbon microballoons are prepared by pyrolyzing phenolic microballoons and subsequently bonded using a 2% bismaleimide solution. The laminate structures are cured for two hours at 477.degree. K. and are adhered to the honeycomb bismaleimide adhesive using a pressure of 700 kN/m.sup.2 pressure at 450.degree. K. The laminate composite is then post-cured for two hours at 527.degree. K. to produce a composite laminate having a density in the range from about 95 kilograms per cubic meter to 130 kilograms per cubic meter.

Oxygen plasma resistant phosphine oxide containing imide/arylene copolymers

NASA Technical Reports Server (NTRS)

Jensen, Brian J.

1993-01-01

A series of oxygen plasma resistant imide/arylene ether copolymers were prepared by reacting anhydride-terminated poly(amide acids) and amine-terminated polyarylene ethers containing phosphine oxide units. Inherent viscosities for these copolymers ranged from 0.42 to 0.80 dL/g. After curing, the resulting copolymers had glass transition temperatures ranging from 224 C to 228 C. Solution cast films of the block copolymers were tough and flexible with tensile strength, tensile moduli, and elongation at break up to 16.1 ksi, 439 ksi, and 23 percent, respectively at 25 C and 9.1 ksi, 308 ksi and 97 percent, respectively at 150 C. The copolymers show a significant improvement in resistance to oxygen plasma when compared to the commercial polyimide Kapton. The imide/arylene ether copolymers containing phosphine oxide units are suitable as coatings, films, adhesives, and composite matrices.

New Fluorinated Polymers

NASA Technical Reports Server (NTRS)

Fitch, John W., III

1997-01-01

This report summarizes progress during 1996 in our research effort along with a description of additional results associated with a TAG supplement to this grant (items 2 and 5 below). Progress is reported in five areas: 1) Polyamides Derived from [(p-HOOCC6H4)](sub 2)C(CF3)X (X= -CF3, OCH3, Cl); 2) Phosphorus-containing '12F-PEK' - Effect of Systematic Replacement of [(p-FC6H4COC6H4)](sub 2)C[(CF3)](sub 2) Monomer by [(p-FC6H4)](sub 2)(C6H5)PO; 3) Poly(ether ketone)s Derived from [(p-FC6H4COC6H4)](sub 2)(C6H5)PO; 4) New CF3-containing Organosilane Monomers and; 5) New Monomers for 12F-PEK Analogues with Improved Processability and Solubility.

A review of recent developments in joining high-performance thermoplastic composites

NASA Astrophysics Data System (ADS)

Cole, K. C.

1991-06-01

There is currently a great deal of interest in the use of thermoplastic polymers as matrices in fiber reinforced composites for high performance applications, such as those encountered in the aerospace industry. These materials include polyether ether ketone (PEEK), polyphenylene sulphide (PPS), polyetherimide (PEI), polyamideimide (PAI), polyamides, polyimides, and polysulphones. A literature review is provided on the different ways of joining high performance thermoplastic composites by adhesive and fusion bonding. The discussion on adhesive bonding includes examination of the performance of specific adhesive/thermoplastic combinations and of techniques for the preparation of composite surfaces: abrasion, etching, flame, and plasma treatments. Thermoplastic composite welding techniques discussed in depth include the following: heated press welding, resistance welding, induction welding, and ultrasonic welding. Works which examine or compare applications for these bonding techniques are also reviewed.

Effect of solvent evaporation and coagulation on morphology development of asymmetric membranes

NASA Astrophysics Data System (ADS)

Chandrasekaran, Neelakandan; Kyu, Thein

2008-03-01

Miscibility behavior of blends of amorphous polyamide (PA) and polyvinylpyrrolidone (PVP) was studied in relation to membrane formation. Dimethylsulfoxide (DMSO) and water were used as solvent and non-solvent, respectively. Differential scanning calorimetry and cloud point measurements revealed that the binary PA/PVP blends as well as the ternary PA/PVP/DMSO system were completely miscible at all compositions. However, the addition of non-solvent (water) to this ternary system has led to phase separation. Visual turbidity study was used to establish a ternary liquid-liquid phase diagram of the PA-PVP/DMSO/water system. Scanning Electron Microscopy (SEM) showed the development of finger-like and sponge-like cross sectional morphologies during coagulation. Effects of polymer concentration, PA/PVP blend ratio, solvent/non-solvent quality, and evaporation time on the resulting membrane morphology will be discussed.

Multifaceted catalytic hydrogenation of amides via diverse activation of a sterically confined bipyridine-ruthenium framework.

PubMed

Miura, Takashi; Naruto, Masayuki; Toda, Katsuaki; Shimomura, Taiki; Saito, Susumu

2017-05-16

Amides are ubiquitous and abundant in nature and our society, but are very stable and reluctant to salt-free, catalytic chemical transformations. Through the activation of a "sterically confined bipyridine-ruthenium (Ru) framework (molecularly well-designed site to confine adsorbed H 2 in)" of a precatalyst, catalytic hydrogenation of formamides through polyamide is achieved under a wide range of reaction conditions. Both C=O bond and C-N bond cleavage of a lactam became also possible using a single precatalyst. That is, catalyst diversity is induced by activation and stepwise multiple hydrogenation of a single precatalyst when the conditions are varied. The versatile catalysts have different structures and different resting states for multifaceted amide hydrogenation, but the common structure produced upon reaction with H 2 , which catalyzes hydrogenation, seems to be "H-Ru-N-H."

Programmable genetic switches to control transcriptional machinery of pluripotency.

PubMed

Pandian, Ganesh N; Sugiyama, Hiroshi

2012-06-01

Transcriptional activators play a central role in the regulation of gene expression and have the ability to manipulate the specification of cell fate. Pluripotency is a transient state where a cell has the potential to develop into more than one type of mature cell. The induction of pluripotency in differentiated cells requires extensive chromatin reorganization regulated by core transcriptional machinery. Several small molecules have been shown to enhance the efficiency of somatic cell reprogramming into pluripotent stem cells. However, entirely chemical-based reprogramming remains elusive. Recently, we reported that selective DNA-binding hairpin pyrrole-imidazole polyamides conjugated with histone deacetylase inhibitor could mimic natural transcription factors and epigenetically activate certain pluripotency-associated genes. Here, we review the need to develop selective chromatin-modifying transcriptional activators for somatic genome reprogramming. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of ultrasonic energy on dyeing of polyamide (microfibre)/Lycra blends.

PubMed

Merdan, Nigar; Akalin, Mehmet; Kocak, Dilara; Usta, Ismail

2004-04-01

Although ultrasonic energy is widely used cleaning and degreasing of parts and assemblies in automotive and other industries, the use of ultrasonic energy in an industrial scale for textile washing is very new. This is due to the complexity of controlling the combination of chemical and mechanical effects, whereas with degreasing of machine parts only the mechanical effects is applied. The use of ultrasonic energy in dyeing PA/Lycra fabrics with reactive dyes has been studied spectrophotometrically in this work. PA/Lycra (85/15) blends have been dyed using conventional and ultrasonic dyeing techniques with three reactive dyes containing different chromophore and reactive groups. The dyeing carried out conventionally and by the use of ultrasonic techniques. The results were compared in terms of percentage exhaustion; total dye transferred to the washing bath after dyeing and the fastness properties.

Sustainability of Recycled ABS and PA6 by Banana Fiber Reinforcement: Thermal, Mechanical and Morphological Properties

NASA Astrophysics Data System (ADS)

Singh, Rupinder; Kumar, Ranvijay; Ranjan, Nishant

2018-01-01

In the present study efforts have been made to prepare functional prototypes with improved thermal, mechanical and morphological properties from polymeric waste for sustainability. The primary recycled acrylonitrile butadiene styrene (ABS) and polyamide 6 (PA6) has been selected as matrix material with bio-degradable and bio-compatible banana fibers (BF) as reinforcement. The blend (in form of feed stock filament wire) of ABS/PA6 and BF was prepared in house by conventional twin screw extrusion (TSE) process. Finally feed stock filament of ABS/PA6 reinforced with BF was put to run on open source fused deposition modelling based three dimensional printer (without any change in hardware/software of the system) for printing of functional prototypes with improved thermal/mechanical/morphological properties. The results are supported by photomicrographs, thermographs and mechanical testing.

Ion-conducting membranes

DOEpatents

Masel, Richard I.; Chen, Qingmei; Liu, Zengcai; Kutz, Robert

2017-02-28

An ion conducting polymeric composition mixture comprises a copolymer of styrene and vinylbenzyl-R.sub.s. R.sub.s is selected from the group consisting of imidazoliums, pyridiniums, pyrazoliums, pyrrolidiniums, pyrroliums, pyrimidiums, piperidiniums, indoliums, and triaziniums. The composition contains 10%-90% by weight of vinylbenzyl-R.sub.s. The composition can further comprise a polyolefin comprising substituted polyolefins, a polymer comprising cyclic amine groups, a polymer comprising at least one of a phenylene group and a phenyl group, a polyamide, and/or the reaction product of a constituent having two carbon-carbon double bonds. The composition can be in the form of a membrane. In a preferred embodiment, the membrane is a Helper Membrane that increases the faradaic efficiency of an electrochemical cell into which the membrane is incorporated, and also allows product formation at lower voltages than in cells without the Helper Membrane.

Antimicrobial and antitumor activity of platinum and palladium complexes of novel spherical aramides nanoparticles containing flexibilizing linkages: structure-property relationship.

PubMed

Elhusseiny, Amel F; Hassan, Hammed H A M

2013-02-15

Square planar Pd (II) and octahedral Pt (IV) complexes with novel spherical aramides nanoparticles containing flexible linkages ligands have been synthesized and characterized using analytical and spectral techniques. The synthesized complexes have been tested for their antimicrobial activity using Kirby-Bauer disc diffusion method. The antitumor activity has been performed using liver carcinoma (HEPG2), breast carcinoma (MCF7) and colon carcinoma (HCT 116) cell lines. Palladium complexes of polyamides containing sulfones showed the highest potency as antibacterial and antifungal agents. Platinum complexes containing sulfone and ether flexible linkages and chloro groups exhibited high potency as antitumor and antimicrobial agents. The uniform sizes of these nanomaterials could find biological uses such as immune assay and other medical purposes. Copyright © 2012 Elsevier B.V. All rights reserved.

[Dialysate and biocompatibility in hemodialysis].

PubMed

Berland, Y

1998-01-01

This article summarise the main data in the literature on the role of bacteriological contamination of the dialysate fluid in inflammatory reactions in hemodialysis. Pyrogenic substances of small molecular weight from Gram-negative bacteria grown in dialysate can pass across intact dialyzer membrane to stimulate cytokine production by peripheral blood mononuclear cells. Cellulosic hemodialysis membranes are more permeable to endotoxins than synthetic membranes. Polysulfone membranes and polyamide membranes are able to adsorb bacterial toxins on the dialysate side. The diffusive transfer of bacterial products across dialysis membrane from dialysate fluid was demonstrated. Transmembrane passage of cytokine-inducing bacterial products across reprocessed dialyzers is greater than across new dialyzers. Bacteriological contamination of the dialysate fluid is a problem which must be considered with much more care by nephrologists, especially as LAL test is unable to detect all the bacterial products which can contaminate the dialysate fluid.

Manufacturing the Gas Diffusion Layer for PEM Fuel Cell Using a Novel 3D Printing Technique and Critical Assessment of the Challenges Encountered

PubMed Central

Singamneni, Sarat; Ramos, Maximiano; Al-Jumaily, Ahmed M

2017-01-01

The conventional gas diffusion layer (GDL) of polymer electrolyte membrane (PEM) fuel cells incorporates a carbon-based substrate, which suffers from electrochemical oxidation as well as mechanical degradation, resulting in reduced durability and performance. In addition, it involves a complex manufacturing process to produce it. The proposed technique aims to resolve both these issues by an advanced 3D printing technique, namely selective laser sintering (SLS). In the proposed work, polyamide (PA) is used as the base powder and titanium metal powder is added at an optimised level to enhance the electrical conductivity, thermal, and mechanical properties. The application of selective laser sintering to fabricate a robust gas diffusion substrate for PEM fuel cell applications is quite novel and is attempted here for the first time. PMID:28773156

Manufacturing the Gas Diffusion Layer for PEM Fuel Cell Using a Novel 3D Printing Technique and Critical Assessment of the Challenges Encountered.

PubMed

Jayakumar, Arunkumar; Singamneni, Sarat; Ramos, Maximiano; Al-Jumaily, Ahmed M; Pethaiah, Sethu Sundar

2017-07-14

The conventional gas diffusion layer (GDL) of polymer electrolyte membrane (PEM) fuel cells incorporates a carbon-based substrate, which suffers from electrochemical oxidation as well as mechanical degradation, resulting in reduced durability and performance. In addition, it involves a complex manufacturing process to produce it. The proposed technique aims to resolve both these issues by an advanced 3D printing technique, namely selective laser sintering (SLS). In the proposed work, polyamide (PA) is used as the base powder and titanium metal powder is added at an optimised level to enhance the electrical conductivity, thermal, and mechanical properties. The application of selective laser sintering to fabricate a robust gas diffusion substrate for PEM fuel cell applications is quite novel and is attempted here for the first time.

Low density bismaleimide-carbon microballoon composites. [aircraft and submarine compartment safety

NASA Technical Reports Server (NTRS)

Kourtides, D. A.; Parker, J. A. (Inventor)

1978-01-01

A process is described for constructing for a composite laminate structure which exhibits a high resistance to heat and flame provides safer interior structures for aircraft and submarine compartments. Composite laminate structures are prepared by the bismaleimide resin preimpregnation of a fiberglass cloth to form a face sheet which is bonded with a bismaleimide hot melt adhesive to a porous core structure selected from the group consisting of polyamide paper and bismaleimide-glass fabric which is filled with carbon microballoons. The carbon microballoons are prepared by pyrolyzing phenolic micro-balloons in the presence of nitrogen. A slurry of the carbon microballoons is prepared to fill the porous core structure. The porous core structure and face sheet are bonded to provide panel structures exhibiting increased mechanical capacities and lower oxygen limit values and smoke density values.

A Combined Experimental and Numerical Approach to the Laser Joining of Hybrid Polymer - Metal Parts

NASA Astrophysics Data System (ADS)

Rodríguez-Vidal, E.; Lambarri, J.; Soriano, C.; Sanz, C.; Verhaeghe, G.

A two-step method for the joining of opaque polymer to metal is presented. Firstly, the metal is structured locally on a micro-scale level, to ensure adhesion with the polymeric counterpart. In a second step, the opposite side of the micro-structured metal is irradiated by means of a laser source. The heat thereby created is conducted by the metal and results in the melting of the polymer at the interface. The polymer thereby adheres to the metal and flows into the previously engraved structures, creating an additional mechanical interlock between the two materials. The welding parameters are fine-tuned with the assistance of a finite element model, to ensure the required interface temperature. The method is illustrated using a dual phase steel joined to a fiber-reinforced polyamide. The effect of different microstructures, in particular geometry and cavity aspect ratio, on the joint's tensile-shear mechanical performance is discussed.

Reductionist Approach in Peptide-Based Nanotechnology.

PubMed

Gazit, Ehud

2018-06-20

The formation of ordered nanostructures by molecular self-assembly of proteins and peptides represents one of the principal directions in nanotechnology. Indeed, polyamides provide superior features as materials with diverse physical properties. A reductionist approach allowed the identification of extremely short peptide sequences, as short as dipeptides, which could form well-ordered amyloid-like β-sheet-rich assemblies comparable to supramolecular structures made of much larger proteins. Some of the peptide assemblies show remarkable mechanical, optical, and electrical characteristics. Another direction of reductionism utilized a natural noncoded amino acid, α-aminoisobutryic acid, to form short superhelical assemblies. The use of this exceptional helix inducer motif allowed the fabrication of single heptad repeats used in various biointerfaces, including their use as surfactants and DNA-binding agents. Two additional directions of the reductionist approach include the use of peptide nucleic acids (PNAs) and coassembly techniques. The diversified accomplishments of the reductionist approach, as well as the exciting future advances it bears, are discussed.

High voltage insulation of bushing for HTS power equipment

NASA Astrophysics Data System (ADS)

Kim, Woo-Jin; Choi, Jae-Hyeong; Kim, Sang-Hyun

2012-12-01

For the operation of high temperature superconducting (HTS) power equipments, it is necessary to develop insulating materials and high voltage (HV) insulation technology at cryogenic temperature of bushing. Liquid nitrogen (LN2) is an attractive dielectric liquid. Also, the polymer insulating materials are expected to be used as solid materials such as glass fiber reinforced plastic (GFRP), polytetra-fluoroethylene (PTFE, Teflon), Silicon (Si) rubber, aromatic polyamide (Nomex), EPDM/Silicon alloy compound (EPDM/Si). In this paper, the surface flashover characteristics of various insulating materials in LN2 are studied. These results are studied at both AC and impulse voltage under a non-uniform field. The use of GFRP and Teflon as insulation body for HTS bushing should be much desirable. Especially, GFRP is excellent material not only surface flashover characteristics but also mechanical characteristics at cryogenic temperature. The surface flashover is most serious problem for the shed design in LN2 and operation of superconducting equipments.

Challenges in Laser Sintering of Melt-Processable Thermoset Imide Resin

NASA Technical Reports Server (NTRS)

Chuang, Kathy C.; Gornet, Timothy; Koerner, Hilmar

2016-01-01

Polymer Laser Sintering (LS) is an additive manufacturing technique that builds 3D models layer by layer using a laser to selectively melt cross sections in powdered polymeric materials, following sequential slices of the CAD model. LS generally uses thermoplastic polymeric powders, such as polyamides (i.e. Nylon), and the resultant 3D objects are often weaker in their strength compared to traditionally processed materials, due to the lack of polymer inter-chain connection in the z-direction. The objective of this project is to investigate the possibility of printing a melt-processable RTM370 imide resin powder terminated with reactive phenylethynyl groups by LS, followed by a postcure in order to promote additional crosslinking to achieve higher temperature (250-300 C) capability. A preliminary study to build tensile specimens by LS and the corresponding DSC and rheology study of RTM370 during LS process is presented.

Challenges in Laser Sintering of Thermoset Imide Resin

NASA Technical Reports Server (NTRS)

Chuang, Kathy C.; Gornet, Timothy; Koerner, Hilmar

2016-01-01

Polymer Laser Sintering (LS) is an additive manufacturing technique that builds 3D models layer by layer using a laser to selectively melt cross sections in powdered polymeric materials, following sequential slices of the CAD model. LS generally uses thermoplastic polymeric powders, such as polyamides (i.e. Nylon), and the resultant 3D objects are often weaker in their strength compared to traditionally processed materials, due to the lack of polymer inter-chain connection in the z-direction. The objective of this project is to investigate the possibility of printing a melt-processable RTM370 imide resin powder terminated with reactive phenylethynyl groups by LS, followed by a postcure in order to promote additional crosslinking to achieve higher temperature (250-300 C) capability. A preliminary study to build tensile specimens by LS and the corresponding DSC and rheology study of RTM370 during LS process is presented.

Tuning the dispersion of multiwall carbon nanotubes in co-continuous polymer blends: a generic approach

NASA Astrophysics Data System (ADS)

Bose, Suryasarathi; Bhattacharyya, Arup R.; Khare, Rupesh A.; Kulkarni, Ajit R.; Umasankar Patro, T.; Sivaraman, P.

2008-08-01

Melt-mixed blends of polyamide 6 and acrylonitrile-butadiene-styrene (PA6/ABS) with multiwall carbon nanotubes (MWNTs) were prepared with the intention to develop conducting composites. A generic strategy, namely specific interactions combined with reactive coupling, was adopted to facilitate and to retain the 'network-like' structure of MWNTs during melt-mixing. This was facilitated by the sodium salt of 6-amino hexanoic acid (Na-AHA) and certain phosphonium based modifiers, where it was envisaged that these modifiers would establish specific interactions (either 'cation-π' or 'π-π' ) with the 'π-electron' clouds of MWNTs, as well as restricting them in the PA6 phase of the blends via reactive coupling. This route eventually led to a remarkable increase in the electrical conductivity and dielectric constant in the blends with MWNTs. Raman, FTIR and TEM investigations further supported these observations.

Hermetically sealable package for hybrid solid-state electronic devices and the like

NASA Technical Reports Server (NTRS)

Miller, Wilson N. (Inventor); Gray, Ormal E. (Inventor)

1988-01-01

A light-weight, inexpensively fabricated, hermetically sealable, repairable package for small electronic or electromechanical units, having multiple connections, is described. A molded ring frame of polyamide-imide plastic (Torlon) is attached along one edge to a base plate formed of a highly heat conducting material, such as aluminum or copper. Bores are placed through a base plate within the area of the edge surface of ring frame which result in an attachment of the ring frame to the base plate during molding. Electrical leads are molded into the ring frame. The leads are L-shaped gold-plated copper wires imbedded within widened portions of the side wall of the ring frame. Within the plastic ring frame wall the leads are bent (typically, though not necessarily at 90 deg) so that they project into the interior volume of the ring frame for connection to the solid state devices.

Analytical assessment of woven fabrics under vertical stabbing - The role of protective clothing.

PubMed

Hejazi, Sayyed Mahdi; Kadivar, Nastaran; Sajjadi, Ali

2016-02-01

Knives are being used more commonly in street fights and muggings. Therefore, this work presents an analytical model for woven fabrics under vertical stabbing loads. The model is based on energy method and the fabric is assumed to be unidirectional comprised of N layers. Thus, the ultimate stab resistance of fabric was determined based on structural parameters of fabric and geometrical characteristics of blade. Moreover, protective clothing is nowadays considered as a strategic branch in technical textile industry. The main idea of the present work is improving the stab resistance of woven textiles by using metal coating method. In the final, a series of vertical stabbing tests were conducted on cotton, polyester and polyamide fabrics. Consequently, it was found that the model predicts with a good accuracy the ultimate stab resistance of the sample fabrics. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

The present situation of the irradiation application industry and irradiation facilities in Japan

NASA Astrophysics Data System (ADS)

Mizusawa, K.; Baba, T.

2003-08-01

The irradiation application industry and irradiation facilities in Japan have been making slow but steady progress for the past 2-3 years. Beside conventional applications, new ones such as carbon fibers and membrane filters have come into the market. There are a lot of new applications about to emerge. PE tubing, already is in the European market, is being evaluated by end users in Japan. Cleaning of dioxin in exhaust gas was successfully tested at a pilot plant. Cross-linked PTFE and polyamide are waiting customers' evaluations as an engineering plastic. Surface cross-linking of artificial polycarbonate teeth has yielded remarkable experimental results. Cross-linking of polycaprolactone will be useful for biodegradable products. Being aware of the future growth of irradiation industry, contract service providers opened new facilities or increased their capability. Beside in-house facilities, there are now three Co-60 facilities and nine EB facilities available for contract irradiation in Japan.

Development of flame resistant treatment for Nomex fibrous structures

NASA Technical Reports Server (NTRS)

Toy, M. S.

1977-01-01

Flame resistant fibrous materials for space shuttle application were developed through chemical modification of commercially available aromatic polyamide fibrous products. The new surface treatment was achieved in the laboratory by ultraviolet activation of the fabric in the presence of fluoroolefin monomers and a diluent gas. The monomers grafted under these conditions provide the improved properties of the fabric in flame resistance, chemical inertness, and nonwettability without the sacrifice of color or physical properties. The laboratory reaction vessel was scaled-up to a batch continuous process, which treats ten yards of the commercial width textiles. The treated commercial width Nomex (HT-10-41) from the scaled-up reactor is self-extinguishing in an oxygen-enriched environment, water-repellent, soft, silky, and improved in chemical resistance. Unlike most textile processes, the grafting unit operates under dry conditions and no chemical by-products have to be washed out of the finished product.

[Preface for special issue on bio-based materials (2016)].

PubMed

Weng, Yunxuan

2016-06-25

Bio-based materials are new materials or chemicals with renewable biomass as raw materials such as grain, legume, straw, bamboo and wood powder. This class of materials includes bio-based polymer, biobased fiber, glycotechnology products, biobased rubber and plastics produced by biomass thermoplastic processing and basic biobased chemicals, for instance, bio-alcohols, organic acids, alkanes, and alkenes, obtained by bio-synthesis, bio-processing and bio-refinery. Owing to its environmental friendly and resource conservation, bio-based materials are becoming a new dominant industry taking the lead in the world scientific and technological innovation and economic development. An overview of bio-based materials development is reported in this special issue, and the industrial status and research progress of the following aspects, including biobased fiber, polyhydroxyalkanoates, biodegradable mulching film, bio-based polyamide, protein based biomedical materials, bio-based polyurethane, and modification and processing of poly(lactic acid), are introduced.

Fiber Orientation Effects in Fused Filament Fabrication of Air-Cooled Heat Exchangers

NASA Astrophysics Data System (ADS)

Mulholland, T.; Goris, S.; Boxleitner, J.; Osswald, T. A.; Rudolph, N.

2018-03-01

Fused filament fabrication (FFF) is a type of additive manufacturing based on material extrusion that has long been considered a prototyping technology. However, the right application of material, process, and product can be used for manufacturing of end-use products, such as air-cooled heat exchangers made by adding fillers to the base polymer, enhancing the thermal conductivity. Fiber fillers lead to anisotropic thermal conductivity, which is governed by the process-induced fiber orientation. This article presents an experimental study on the microstructure-property relationship for carbon fiber-filled polyamide used in FFF. The fiber orientation is measured by micro-computed tomography, and the thermal conductivity of manufactured samples is measured. Although the thermal conductivity is raised by more than three times in the fiber orientation direction at a load of only 12 vol.%, the enhancement is low in the other directions, and this anisotropy, along with certain manufacturing restrictions, influences the final part performance.

Detection of chlorinated aromatic compounds

DOEpatents

Ekechukwu, A.A.

1996-02-06

A method for making a composition for measuring the concentration of chlorinated aromatic compounds in aqueous fluids, and an optical probe for use with the method are disclosed. The composition comprises a hydrophobic polymer matrix, preferably polyamide, with a fluorescent indicator uniformly dispersed therein. The indicator fluoresces in the presence of the chlorinated aromatic compounds with an intensity dependent on the concentration of these compounds in the fluid of interest, such as 8-amino-2-naphthalene sulfonate. The probe includes a hollow cylindrical housing that contains the composition in its distal end. The probe admits an aqueous fluid to the probe interior for exposure to the composition. An optical fiber transmits excitation light from a remote source to the composition while the indicator reacts with chlorinated aromatic compounds present in the fluid. The resulting fluorescence light signal is reflected to a second optical fiber that transmits the light to a spectrophotometer for analysis. 5 figs.

Relating Silica Scaling in Reverse Osmosis to Membrane Surface Properties.

PubMed

Tong, Tiezheng; Zhao, Song; Boo, Chanhee; Hashmi, Sara M; Elimelech, Menachem

2017-04-18

We investigated the relationship between membrane surface properties and silica scaling in reverse osmosis (RO). The effects of membrane hydrophilicity, free energy for heterogeneous nucleation, and surface charge on silica scaling were examined by comparing thin-film composite polyamide membranes grafted with a variety of polymers. Results show that the rate of silica scaling was independent of both membrane hydrophilicity and free energy for heterogeneous nucleation. In contrast, membrane surface charge demonstrated a strong correlation with the extent of silica scaling (R 2 > 0.95, p < 0.001). Positively charged membranes significantly facilitated silica scaling, whereas a more negative membrane surface charge led to reduced scaling. This observation suggests that deposition of negatively charged silica species on the membrane surface plays a critical role in silica scale formation. Our findings provide fundamental insights into the mechanisms governing silica scaling in reverse osmosis and highlight the potential of membrane surface modification as a strategy to reduce silica scaling.

Programmable DNA scaffolds for spatially-ordered protein assembly.

PubMed

Chandrasekaran, Arun Richard

2016-02-28

Ever since the notion of using DNA as a material was realized, it has been employed in the construction of complex structures that facilitate the assembly of nanoparticles or macromolecules with nanometer-scale precision. Specifically, tiles fashioned from DNA strands and DNA origami sheets have been shown to be suitable as scaffolds for immobilizing proteins with excellent control over their spatial positioning. Supramolecular assembly of proteins into periodic arrays in one or more dimensions is one of the most challenging aspects in the design of scaffolds for biomolecular investigations and macromolecular crystallization. This review provides a brief overview of how various biomolecular interactions with high degree of specificity such as streptavidin-biotin, antigen-antibody, and aptamer-protein interactions have been used to fabricate linear and multidimensional assemblies of structurally intact and functional proteins. The use of DNA-binding proteins as adaptors, polyamide recognition on DNA scaffolds and oligonucleotide linkers for protein assembly are also discussed.

Process for crosslinking and extending conjugated diene-containing polymers

NASA Technical Reports Server (NTRS)

Bell, Vernon L. (Inventor); Havens, Stephen J. (Inventor)

1977-01-01

A process using a Diels-Alder reaction which increases the molecular weight and/or crosslinks polymers by reacting the polymers with bisunsaturated dienophiles is developed. The polymer comprises at least 75% by weight based on the reaction product, has a molecular weight of at least 5000 and a plurality of conjugated 1,3-diene systems incorporated into the molecular structure. A dienophile reaction with the conjugated 1,3-diene of the polymer is at least 1% by weight based on the reaction product. Examples of the polymer include polyesters, polyamides, polyethers, polysulfones and copolymers. The bisunsaturated dienophiles may include bis-maleimides, bis maleic and bis tumaric esters and amides. This method for expanding the molecular weight chains of the polymers, preferable thermoplastics, is advantageous for processing or fabricating thermoplastics. A low molecular weight thermoplastic is converted to a high molecular weight plastic having improved strength and toughness for use in the completed end use article.

Combining aminocyanine dyes with polyamide dendrons: a promising strategy for imaging in the near-infrared region.

PubMed

Ornelas, Cátia; Lodescar, Rachelle; Durandin, Alexander; Canary, James W; Pennell, Ryan; Liebes, Leonard F; Weck, Marcus

2011-03-21

Cyanine dyes are known for their fluorescence in the near-IR (NIR) region, which is desirable for biological applications. We report the synthesis of a series of aminocyanine dyes containing terminal functional groups such as acid, azide, and cyclooctyne groups for further functionalization through, for example, click chemistry. These aminocyanine dyes can be attached to polyfunctional dendrons by copper-catalyzed azide alkyne cycloaddition (CuAAC), strain-promoted azide alkyne cycloaddition (SPAAC), peptide coupling, or direct S(NR)1 reactions. The resulting dendron-dye conjugates were obtained in high yields and displayed high chemical stability and photostability. The optical properties of the new compounds were studied by UV/Vis and fluorescence spectroscopy. All compounds show large Stokes shifts and strong fluorescence in the NIR region with high quantum yields, which are optimal properties for in vivo optical imaging. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ammonia Sensing Behaviors of TiO2-PANI/PA6 Composite Nanofibers

PubMed Central

Wang, Qingqing; Dong, Xianjun; Pang, Zengyuan; Du, Yuanzhi; Xia, Xin; Wei, Qufu; Huang, Fenglin

2012-01-01

Titanium dioxide-polyaniline/polyamide 6 (TiO2-PANI/PA6) composite nanofibers were prepared by in situ polymerization of aniline in the presence of PA6 nanofibers and a sputtering-deposition process with a high purity titanium sputtering target. TiO2-PANI/PA6 composite nanofibers and PANI/PA6 composite nanofibers were fabricated for ammonia gas sensing. The ammonia sensing behaviors of the sensors were examined at room temperature. All the results indicated that the ammonia sensing property of TiO2-PANI/PA6 composite nanofibers was superior to that of PANI/PA6 composite nanofibers. TiO2-PANI/PA6 composite nanofibers had good selectivity to ammonia. It was also found that the content of TiO2 had a great influence on both the morphology and the sensing property of TiO2-PANI/PA6 composite nanofibers. PMID:23235446