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1

Recent Advances in Thermoplastic Puncture-Healing Polymers  

NASA Technical Reports Server (NTRS)

Self-healing materials provide a route for enhanced damage tolerance in materials for aerospace applications. In particular, puncture-healing upon impact has the potential to mitigate significant damage caused by high velocity micrometeoroid impacts. This type of material also has the potential to improve damage tolerance in load bearing structures to enhance vehicle health and aircraft durability. The materials being studied are those capable of instantaneous puncture healing, providing a mechanism for mechanical property retention in lightweight structures. These systems have demonstrated healing capability following penetration of fast moving projectiles -- velocities that range from 9 mm bullets shot from a gun (approx.330 m/sec) to close to micrometeoroid debris velocities of 4800 m/sec. In this presentation, we report on a suite of polymeric materials possessing this characteristic. Figure 1 illustrates the puncture healing concept. Puncture healing in these materials is dependent upon how the combination of a polymer's viscoelastic properties responds to the energy input resulting from the puncture event. Projectile penetration increases the temperature in the vicinity of the impact. Self-healing behavior occurs following puncture, whereby energy must be transferred to the material during impact both elastically and inelastically, thus establishing two requirements for puncture healing to occur: a.) The need for the puncture event to produce a local melt state in the polymer material and b.) The molten material has to have sufficient melt elasticity to snap back and close the hole. 1,2 Previous ballistic testing studies revealed that Surlyn materials warmed up to a temperature approx.98 C during projectile puncture (3 C higher than it s melting temperature). 1,2 The temperature increase produces a localized flow state and the melt elasticity to snap back thus sealing the hole. Table 1 lists the commercially polymers studied here, together with their physical properties. The polymers were selected based on chemical structure, tensile strengths, tensile moduli, glass transition temperature, melting temperatures, and impact strength. The thermal properties of the polymers were characterized by Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA). Mechanical properties were assessed by a Sintech 2W instron according to ASTM D1708 or D638 at crosshead speeds of 5.08 cm/min. 7.6 cm x 7.6 cm panels of the different materials were prepared and ballistic testing was performed at various temperatures. The panels were shot with a .223 caliber semiautomatic rifle from a distance of 23 meters at various temperatures. Chronographs were used to measure initial and final bullet velocity. Temperatures at the site of impact were measured using a FLIR ThermaCAM S60 thermal camera. A Vision Research model Phantom 9 high speed video camera was used to capture high speed video footage of ballistics testing.

Gordon, K. L.; Working, D. C.; Wise, K. E.; Bogert, P. B.; Britton, S. M.; Topping, C.C.; Smith, J. Y.; Siochi, E. J.

2009-01-01

2

Recent Advances in Thermoplastic Puncture-Healing Polymers  

NASA Technical Reports Server (NTRS)

The motivation for this work is to develop self-healing polymeric materials to enable damage tolerant systems, and to tailor puncture healing for use temperatures and applications. This will be a benefit in environments and conditions where access for manual repair is limited or impossible, or where damage may not be detected.

Bogert, Philip B.; Working, Dennis C.; Wise, Kristopher E.; Smith, Janice Y.; Topping, Crystal C.; Britton, Sean M.; Bagby, Paul R.; Siochi, Emilie J.

2010-01-01

3

Bonding thermoplastic polymers  

DOEpatents

We demonstrate a new method for joining patterned thermoplastic parts into layered structures. The method takes advantage of case-II permeant diffusion to generate dimensionally controlled, activated bonding layers at the surfaces being joined. It is capable of producing bonds characterized by cohesive failure while preserving the fidelity of patterned features in the bonding surfaces. This approach is uniquely suited to production of microfluidic multilayer structures, as it allows the bond-forming interface between plastic parts to be precisely manipulated at micrometer length scales. The bond enhancing procedure is easily integrated in standard process flows and requires no specialized equipment.

Wallow, Thomas I. (Fremont, CA); Hunter, Marion C. (Livermore, CA); Krafcik, Karen Lee (Livermore, CA); Morales, Alfredo M. (Livermore, CA); Simmons, Blake A. (San Francisco, CA); Domeier, Linda A. (Danville, CA)

2008-06-24

4

Miscibility studies of engineering thermoplastic polymer blends  

Microsoft Academic Search

Engineering thermoplastic polymer blends constitute a large part of polymer consumption. To optimize the design of such blends, a great deal of attention has been focused on predicting and characterizing the miscibility of these blends. In this thesis, both experimental and molecular dynamics (MD) simulation methods have been used to address miscibility of three kinds of engineering thermoplastic polymer blends.

Mingzong Zhang

2005-01-01

5

Modification of road bitumens with thermoplastic polymers  

Microsoft Academic Search

Polymer modified bitumens were prepared by blending bitumens with different thermoplastic polymers (SBS, SEBS, EVA and EBA). The fundamental properties (e.g. morphology, rheology and ageing) of the modified binders were studied using fluorescence microscopy, dynamic mechanical analysis, creep test (bending beam rheometer), and gel permeation chromatography. The results indicated that the morphology and rheological properties of the modified binders were

Xiaohu Lu; Ulf Isacsson

2000-01-01

6

Method of forming a foamed thermoplastic polymer  

DOEpatents

A solid thermoplastic polymer is immersed in an immersant solution comprising a compatible carrier solvent and an infusant solution containing an incompatible liquid blowing agent for a time sufficient for the immersant solution to infuse into the polymer. The carrier solvent is then selectively extracted, preferably by a solvent exchange process in which the immersant solution is gradually diluted with and replaced by the infusant solution, so as to selectively leave behind the infustant solution permanently entrapped in the polymer. The polymer is then heated to volatilize the blowing agent and expand the polymer into a foamed state.

Duchane, D.V.; Cash, D.L.

1984-11-21

7

Dynamically cured thermoplastic olefin polymers  

Microsoft Academic Search

A thermoplastic composition is described comprising a polyolefin resin, a first rubber component selected from the group consisting of polyisobutylene, and ethylene propylene copolymer (EPM) and EPDM and a second rubber component selected from the group consisting of halogenated butyl rubber and polychoroprene, the second rubber component being cured utilizing a curative other than a peroxide, which is a vulcanizing

D. R. Hazelton; R. C. Puydak; D. A. Booth

1986-01-01

8

Thermoplastic polymers for improved fire safety  

NASA Technical Reports Server (NTRS)

The thermochemical and flammability characteristics of some typical thermoplastic materials currently in use and others being considered for use in aircraft interiors are described. The properties studied included (1) thermomechanical properties such as glass transition and melt temperature, (2) changes in polymer enthalpy by differential scanning calorimetry, (3) thermogravimetric analysis in anaerobic and oxidative environments, (4) oxygen index, (5) smoke evolution, (6) relative toxicity of the volatile products of pyrolysis, and (7) selected physical properties. The generic polymers that were evaluated included: acrylonitrile butadiene styrene, bisphenol A polycarbonate, 9,9 bis (4-hydroxyphenyl) fluorene polycarbonatepoly (dimethyl siloxane) block polymer, phenolphthalein bisphenol A polycarbonate, phenolphthalein polycarbonate, polyether sulfone, polyphenylene oxide, polyphenylene sulfide, polyaryl sulfone, chlorinated polyvinyl chloride homopolymer, polyvinyl fluoride, and polyvinylidene fluoride. Processing parameters, including molding characteristics of some of the advanced polymers, are described. Test results and relative ranking of some of the flammability, smoke, and toxicity properties are presented.

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

1976-01-01

9

Improved adhesion for thermoplastic polymers using oxyfluorination  

NASA Astrophysics Data System (ADS)

Industrial applications of thermoplastic polymers are often limited by their poor adhesion properties. In this work the effect of surface oxyfluorination on the adhesion properties was investigated for polyethylene (PE), polyoxymethylene (POM), polybutylene terephthalate (PBT) and polyamide 6 (PA6). The adhesive joint strength was quantified using lap-shear tests. These results were correlated with the changes in the chemical composition of the surface, determined by X-ray photoelectron spectroscopy (XPS), in the surface free energy, measured by the contact angle method, and in the topography, using white-light confocal microscopy. The adhesive strength is strongly improved for all four polymers, but the degree of this increase depends on the polymer type. The surface free energy shows a similar trend for all four polymers. A high surface free energy exceeding 50 mN/m was observed after oxy-fluorination, whereby the polar component was strongly predominant. Surface topography measurements show no significant increase of the surface roughness. So the effect of oxyfluorination results primarily in increased wettability and polarity, due to changes of the chemical composition of the surface. XPS measurements confirm the integration of fluorine and oxygen groups in the polymer chain, which correlates with the increased polarity.

Achereiner, F.; Münstedt, H.; Zeiler, T.

2008-03-01

10

Microscale patterning of thermoplastic polymer surfaces by selective solvent swelling.  

PubMed

A new method for the fabrication of microscale features in thermoplastic substrates is presented. Unlike traditional thermoplastic microfabrication techniques, in which bulk polymer is displaced from the substrate by machining or embossing, a unique process termed orogenic microfabrication has been developed in which selected regions of a thermoplastic surface are raised from the substrate by an irreversible solvent swelling mechanism. The orogenic technique allows thermoplastic surfaces to be patterned using a variety of masking methods, resulting in three-dimensional features that would be difficult to achieve through traditional microfabrication methods. Using cyclic olefin copolymer as a model thermoplastic material, several variations of this process are described to realize growth heights ranging from several nanometers to tens of micrometers, with patterning techniques include direct photoresist masking, patterned UV/ozone surface passivation, elastomeric stamping, and noncontact spotting. Orogenic microfabrication is also demonstrated by direct inkjet printing as a facile photolithography-free masking method for rapid desktop thermoplastic microfabrication. PMID:22900539

Rahmanian, Omid; Chen, Chien-Fu; DeVoe, Don L

2012-09-01

11

Microscale Patterning of Thermoplastic Polymer Surfaces by Selective Solvent Swelling  

PubMed Central

A new method for the fabrication of microscale features in thermoplastic substrates is presented. Unlike traditional thermoplastic microfabrication techniques, in which bulk polymer is displaced from the substrate by machining or embossing, a unique process termed orogenic microfabrication has been developed in which selected regions of a thermoplastic surface are raised from the substrate by an irreversible solvent swelling mechanism. The orogenic technique allows thermoplastic surfaces to be patterned using a variety of masking methods, resulting in three-dimensional features that would be difficult to achieve through traditional microfabrication methods. Using cyclic olefin copolymer as a model thermoplastic material, several variations of this process are described to realize growth heights ranging from several nanometers to tens of microns, with patterning techniques include direct photoresist masking, patterned UV/ozone surface passivation, elastomeric stamping, and noncontact spotting. Orogenic microfabrication is also demonstrated by direct inkjet printing as a facile photolithography-free masking method for rapid desktop thermoplastic microfabrication.

Rahmanian, Omid; Chen, Chien-Fu; DeVoe, Don L.

2012-01-01

12

Novel polymer blends with thermoplastic starch  

NASA Astrophysics Data System (ADS)

A new class of polymers known as "bioplastics" has emerged and is expanding rapidly. This class consists of polymers that are either bio-based or biodegradable, or both. Among these, polysaccharides, namely starch, are of great interest for several reasons. By gelatinizing starch via plasticizers, it can be processed in the same way as thermoplastic polymers with conventional processing equipment. Hence, these bio-based and biodegradable plastics, with their low source and refinery costs, as well as relatively easy processability, have made them ideal candidates for incorporation into various current plastic products. Four different plasticizers have been chosen here for gelatinization of thermoplastic starch (TPS): glycerol, sorbitol, diglycerol and polyglycerol, with the latter two being used for the first time in such a process. Two methodological categories are used. The first involves a calorimetric method (Differential Scanning Calorimetry) as well as optical microscopy; these are "static" methods where no shear is applied A wide range of starch/water/plasticizer compositions were prepared to explore the gelatinization regime for each plasticizer. The onset and conclusion gelatinization temperatures for sorbitol and glycerol were found to be in the same vicinity, while diglycerol and polyglycerol showed significantly higher transition temperatures. The higher molecular weight and viscosity of polyglycerol allow this transition to occur at an even higher temperature than with diglycerol. This is due to the increase in molecular weight and viscosity of the two new plasticizers, as well as their significant decrease in water solubility. It is demonstrated that the water/plasticizer ratio has a pronounced effect on gelatinization temperatures. When plasticizer content was held constant and water content was increased, it was found that the gelatinization temperature decreased for all the plasticizers. Meanwhile, when the water content was held constant and the plasticizer content was increased, the gelatinization temperature increased for glycerol, sorbitol and diglycerol, but it moved in the opposite direction in the case of polyglycerol. The gelatinization temperature variation for glycerol, sorbitol and diglycerol caused by changing water and plasticizer content indicates that water is the primary agent causing granular swell and plasticization in the gelatinization process. Due to the high molecular weight and viscosity, as well as the low hydroxyl group density (~ one --OH per two carbon) and borderline solubility of polyglycerol in water, it is believed that water-aided penetration of the plasticizer among the crystalline structure of starch molecules is significantly decelerated. So it is proposed that in the case of low-water solubility of the plasticizers, gelatinization temperature is determined more by the total amount of the plasticizer and water, rather than the water/plasticizer ratio. Increasing the miscibility of polyglycerol in water by increasing the temperature of the initial slurry, results in a return of the system to the typical thermal dependence of gelatinization with plasticizer/water ratio. Secondly, the gelatinization of starch under "dynamic conditions" was studied. In this case, a constant shear is applied to the slurry, along with a temperature ramp to induce gelatinization. This is, in fact, a rheological technique that heats up the slurry, while a mechanical shear is applied throughout. The reason for using this method is that in the plastic industry, thermoplastic starch is produced via processes involving shear such as extrusion, but, to date, there has not yet been a thorough study on the effect of pure shear on the gelatinization process. Glycerol, diglycerol and sorbitol were subjected to different dynamic gelatinization treatments in a couette flow system, and the results were compared with static gelatinization. Applying shear showed virtually no effect on the onset gelatinization temperature. However, the conclusion temperature was remarkably reduced

Taghizadeh, Ata

13

Thermodynamics of deformation for thermoplastic polymers  

SciTech Connect

The post-yielding behavior of some common thermoplastics was examined in uniaxial tension to determine if these materials were ideally plastic from a thermodynamic viewpoint. Various polyethylenes, poly(methyl methacrylate) and polycarbonate, polyarylate and polysulfone based on bisphenol A were studied. Thermodynamic measurements were made during deformation using a novel isothermal deformation calorimeter capable of measuring the work and heat of deformation. Thermodynamically ideal plasticity was not observed for any of the polymers examined. The polyethylenes stored approximately 30% of the input work as a latent internal energy change while this value was 40-50% for the amorphous glasses. Differential-scanning-calorimetry results for the deformed polyethylenes indicated that the heats of transition were less for the drawn samples than for the isotropic samples. This result was primarily due to the stored deformation energy and was not necessarily indicative of a change in crystallinity. Additional experiments were performed to determine the mechanism of deformation energy storage and to ascertain the implications of this stored energy in engineering applications.

Adams, G.W.

1987-01-01

14

Blends of a Thermotropic Liquid Crytalline Polymer and Some Thermoplastics. Compatibilizing and Production of Polymer Blends.  

National Technical Information Service (NTIS)

A polyester type totally aromatic thermotropic liquid crystalline polymer (LCP) was melt blended with various thermoplastics and the blends were injection molded. LCP acted as a reinforcement in the matrix polymers and also improved dimensional and therma...

M. Heino J. V. Seppaelae J. Ahlgren A. Harlin

1990-01-01

15

High temperature drilling fluids based on sulfonated thermoplastic polymers  

SciTech Connect

An oil-based drilling mud is described which consists of: (a) a hydrocarbon oil; (b) about 1 to about 10 parts by weight of water per 100 parts by weight of the hydrocarbon oil; (c) about 20 to about 50 lb/bbl of at least one emulsifier; (d) weighting material necessary to achieve the desired density; and (e) about 0.25 to about 4.0 lb/bbl of a water insoluble and oil insoluble neutralized sulfonated thermoplastic polymer having a molecular weight as measured by GPC of about 5,000 to about 500,000, the water insoluble and oil insoluble neutralized sulfonated thermoplastic polymer having about 5 to about 100 meq. of sulfonate groups per 100 grams of the neutralized sulfonated thermoplastic polymer. The water insoluble and oil insoluble sulfonated thermoplastic is derived from a polymer selected from the group consisting of polystyrene, poly-t-butyl-styrene, polychlorostyrene, poly-alpha methyl styrene, polyvinyl toluene and co- or terpolymers of styrene and acrylonitrile, methyl methacrylate and butadiene.

Walker, T.O.; Peiffer, D.G.; Lundberg, R.D.

1986-04-01

16

TOPICAL REVIEW: Review on micro molding of thermoplastic polymers  

Microsoft Academic Search

Molding of micro components from thermoplastic polymers has become a routinely used industrial production process. This paper describes both the more than 30-year-old history and the present state of development and applications. Hot embossing, injection molding, reaction injection molding, injection compression molding, thermoforming, and various types of tool fabrication are introduced and their advantages and drawbacks are discussed. In addition,

M. Heckele; W. K. Schomburg

2004-01-01

17

Puncture-Healing Properties of Carbon Nanotube-Filled Ionomers  

NASA Technical Reports Server (NTRS)

Ionomers are polymers that contain ionic groups in relatively low concentrations along the polymer backbone. These ionic groups, in the presence of oppositely charged ions, form aggregates that lead to novel physical properties of the polymer. React-A-Seal(trademark) and Surlyn(trademark) are poly(ethylene-co-methacrylic acid) (EMAA) ionomer-based materials and Nucrel(trademark) is the EMAA acid copolymer neutralized to produce Surlyn(trademark). React-A-Seal(trademark), Surlyn(trademark), and Nucrel(trademark) recover into their original shapes following a high impact puncture at velocities ranging from 300 to 1200 ft/s ('self-healing'). This self-healing process may be of great benefit in space applications where structures are exposed to matter impacts. A thermal IR camera indicated a temperature increase to 98 C for Nucrel(trademark) 925, Surlyn(trademark) 8940, React-A-Seal(trademark), and Surlyn(trademark) 8920 after initial penetration. To understand and generalize the observed phenomena, questions concerning the mechanism of the puncture resealing must be answered. One suggestion is that the elastic character of the melt created by the puncture drives the self-healing. This inference is based on the observed temperature rise of approx. 3 C above the melting temperature of the samples (approx. 95 C) during the impact. With the expectation of gaining additional insight into the self-healing phenomenon, a thermodynamic and viscoelastic investigation was conducted using primarily DSC and DMA. Surlyn(trademark) and React-A-Seal(trademark) showed the characteristic order-disorder transition at approx. 52 C that has been reported in literature. Master curves were constructed from the creep isotherms for the four EMAA samples. An aging study was performed to investigate the irreproducibility and "tailing effect" observed in the creep data. The aging study indicated that, with increased aging time and temperature, changes in the polyethylene matrix lead to complexities in morphology resulting in changes in the magnitude and shape of the creep curves.

Ward, Thomas C.

2003-01-01

18

Magnetron sputtered titanium nitride thin films on thermoplastic polymers  

Microsoft Academic Search

Enhancing the durability of thermoplastic polymers is desirable for improved wear resistance (rubbing, scratching, impact) of plastics in particle sensitive environments. In this investigation poly(butylene terephthalate) (PBT), poly(amide)6.6 (PA) and poly(carbonate) (PC) were chosen as substrate material. The selected coating material was titanium nitride (Ti–N), which is known as wear resistant coating in various applications like drilling and for other

E. Lugscheider; S. Bärwulf; M. Riester; H. Hilgers

1999-01-01

19

Thermoplastic polymers surfaces for Dip-Pen Nanolithography of oligonucleotides  

NASA Astrophysics Data System (ADS)

Different thermoplastic polymers were spin-coated to prepare smooth surfaces for the direct deposition of end-group modified oligonucleotides by Dip-Pen Nanolithography. A study of the diffusion process was done in order to investigate the dependence of calibration coefficient and quality of deposited features on environmental parameters (temperature, relative humidity) and ink's molecular weight and functionality. The optimization of the process parameters led to the realization of high quality and density nanoarrays on plastics.

Suriano, Raffaella; Biella, Serena; Cesura, Federico; Levi, Marinella; Turri, Stefano

2013-05-01

20

Thermochemical characterization of some thermally stable thermoplastic and thermoset polymers  

NASA Technical Reports Server (NTRS)

The thermochemical and flammability properties of some thermally stable polymers considered for use in aircraft interiors are described. The properties studied include: (1) thermomechanical properties such as glass transition and melt temperature; (2) dynamic thermogravimetric analysis in anaerobic environment; (3) flammability properties such as oxygen index, flame spread, and smoke evolution; and (4) selected physical properties. The thermoplastic polymers evaluated include polyphenylene sulfide, polyaryl sulfone, 9,9-bis(4-hydroxyphenyl)-fluorene polycarbonate-poly(dimethylsiloxane) and polyether sulfone. The thermoset polymers evaluated include epoxy, bismaleimide, a modified phenolic, and polyaromatic melamine resin. These resins were primarily used in the fabrication of glass-reinforced prepregs for the construction of experimental panels. Test results and relative rankings of some of the flammability parameters are presented, and the relationship of the molecular structure, char yield, and flammability properties of these polymers are discussed.

Kourtides, D. A.; Gilwee, W. J., Jr.; Parker, J. A.

1979-01-01

21

Morphology development in epoxy\\/polymer systems: thermosetting epoxy micro particles with a thermoplastic shell  

Microsoft Academic Search

A novel method based on phase inversion and inter-boundary reaction in a reactive system comprising a thermoplastic phenoxy and a thermosetting epoxy has been proposed to design micro epoxy particles with a thermoplastic polymer shell. Due to the hydroxyl group in phenoxy, inter-domain reactions were found to lead to a chemical link between the polymer and the epoxy network. As

Eamor M. Woo; H. Kun Hseih

1998-01-01

22

Determination of carbon fiber adhesion to thermoplastic polymers using the single fiber/matrix tensile test  

NASA Technical Reports Server (NTRS)

The single fiber adhesion shear test has been adapted to testing the adhesion between carbon fiber and thermoplastic polymers. Tests of three thermoplastics, polycarbonate, polyphenylene oxide and polyetherimide indicate the shear adhesion strength is significantly less than of an epoxy polymer to the same carbon fiber.

Bascom, W. D.; Cordner, L. W.; Hinkley, J. L.; Johnston, N. J.

1986-01-01

23

Mechanical properties of a new thermoplastic polymer orthodontic archwire.  

PubMed

A new thermoplastic polymer for orthodontic applications was obtained and extruded into wires with round and rectangular cross sections. We evaluated the potential of new aesthetic archwire: tensile, three point bending, friction and stress relaxation behaviour, and formability characteristics were assessed. Stresses delivered were generally slightly lower than typical beta-titanium and nickel-titanium archwires. The polymer wire has good instantaneous mechanical properties; tensile stress decayed about 2% over 2h depending on the initial stress relaxation for up to 120h. High formability allowed shape bending similar to that associated with stainless steel wires. The friction coefficients were lower than the metallic conventional archwires improving the slipping with the brackets. This new polymer could be a good candidate for aesthetic orthodontic archwires. PMID:25063084

Varela, Juan Carlos; Velo, Marcos; Espinar, Eduardo; Llamas, Jose Maria; Rúperez, Elisa; Manero, Jose Maria; Javier Gil, F

2014-09-01

24

Tough, high performance, addition-type thermoplastic polymers  

NASA Technical Reports Server (NTRS)

A tough, high performance polyimide is provided by reacting a triple bond conjugated with an aromatic ring in a bisethynyl compound with the active double bond in a compound containing a double bond activated toward the formation of a Diels-Adler type adduct, especially a bismaleimide, a biscitraconimide, or a benzoquinone, or mixtures thereof. Addition curing of this product produces a high linear polymeric structure and heat treating the highly linear polymeric structure produces a thermally stable aromatic addition-type thermoplastic polyimide, which finds utility in the preparation of molding compounds, adhesive compositions, and polymer matrix composites.

Pater, Ruth H. (inventor)

1992-01-01

25

The use of thermoplastic elastomers as polymer processing aids in processing of linear low density polyethylene  

Microsoft Academic Search

Commercially available thermoplastic elastomers based on block copolymers of diisocyanates and polyols and based on silicones\\u000a have been reported by Kulikov et al. (2004 and 2006) to delay sharkskin in extrusion of Linear Low Density Polyethylene. In\\u000a this work thermoplastic elastomers have been used as polymer processing additives in blown film extrusion of Linear Low Density\\u000a Polyethylene. When a thermoplastic

M. Müller; O. Kulikov; K. Hornung; M. H. Wagner

2010-01-01

26

Generation of Continuous Liquid Crystalline Polymer Reinforcements in Thermoplastics by a Novel Blending Process.  

National Technical Information Service (NTIS)

The focus of this work was to investigate the potential of enhancing the mechanical properties of thermoplastic resins, with an emphasis on those which are considered commodity resins, by blending with liquid crystalline polymers (LCPs). There is an inher...

A. Datta A. M. Sukhadia D. G. Baird

1991-01-01

27

Analysis of thermoplastic polyimide + polymer liquid crystal blends  

NASA Astrophysics Data System (ADS)

Thermoplastic polyimides (TPIs) exhibit high glass transition temperatures (Tsbgs), which make them useful in high performance applications. Amorphous and semicrystalline TPIs show sub-Tsbg relaxations, which can aid in improving strength characteristics through energy absorption. The alpha relaxation of both types of TPIs indicates a cooperative nature. The semicrystalline TPI shows thermo-irreversible cold crystallization phenomenon. The polymer liquid crystal (PLC) used in the blends is thermotropic and with longitudinal molecular structure. The small heat capacity change (Delta Csb{p}) associated with the glass transition indicates the PLC to be rigid rod in nature. The PLC shows a small endotherm associated with the melting. The addition of PLC to the semicrystalline TPI does not significantly affect the Tsbg or the melting point (Tsbm). The cold crystallization temperature (Tsbc) increases with the addition of the PLC, indicating channeling phenomenon. The addition of PLC also causes a negative deviation of the Delta Csb{p}, which is another evidence for channeling. The TPI, PLC and their blends show high thermal stability. The semicrystalline TPI absorbs moisture; this effect decreases with the addition of the PLC. The absorbed moisture does not show any effect on the degradation. The addition of PLC beyond 30 wt.% does not result in an improvement of properties. The amorphous TPI + PLC blends also show the negative deviation of Delta Csb{p} from linearity with composition. The addition of PLC causes a decrease in the thermal conductivity in the transverse direction to the PLC orientation. The thermomechanical analysis indicates isotropic expansivity for the amorphous TPI and a small anisotropy for the semicrystalline TPI. The PLC shows large anisotropy in expansivity. Even 5 wt.% concentration of PLC in the blend induces considerable anisotropy in the expansivity. Thus, blends show controllable expansivity through PLC concentration. Amorphous TPI + PLC blends also show excellent film formability. The amorphous TPI blends show good potential for applications requiring high thermal stability, controlled expansivity and good film formability.

Gopalanarayanan, Bhaskar

28

Initiation of shape-memory effect by inductive heating of magnetic nanoparticles in thermoplastic polymers  

Microsoft Academic Search

In shape-memory polymers, changes in shape are mostly induced by heating, and exceeding a specific switching temperature, Tswitch. If polymers cannot be warmed up by heat transfer using a hot liquid or gaseous medium, noncontact triggering will be required. In this article, the magnetically induced shape-memory effect of composites from magnetic nanoparticles and thermoplastic shape-memory polymers is introduced. A polyetherurethane

R. Mohr; K. Kratz; T. Weigel; M. Lucka-Gabor; M. Moneke; A. Lendlein

2006-01-01

29

Process property studies of melt blown thermoplastic polyurethane polymers  

NASA Astrophysics Data System (ADS)

The primary goal of this research was to determine optimum processing conditions to produce commercially acceptable melt blown (MB) thermoplastic polyurethane (TPU) webs. The 6-inch MB line and the 20-inch wide Accurate Products MB pilot line at the Textiles and Nonwovens Development Center (TANDEC), The University of Tennessee, Knoxville, were utilized for this study. The MB TPU trials were performed in four different phases: Phase 1 focused on the envelope of the MB operating conditions for different TPU polymers; Phase 2 focused on the production of commercially acceptable MB TPU webs; Phase 3 focused on the optimization of the processing conditions of MB TPU webs, and the determination of the significant relationships between processing parameters and web properties utilizing statistical analyses; Based on the first three phases, a more extensive study of fiber and web formation in the MB TPU process was made and a multi liner regression model for the MB TPU process versus properties was also developed in Phase 4. In conclusion, the basic MB process was fundamentally valid for the MB TPU process; however, the MB process was more complicated for TPU than PP, because web structures and properties of MB TPUs are very sensitive to MB process conditions: Furthermore, different TPU grades responded very differently to MB processing and exhibited different web structure and properties. In Phase 3 and Phase 4, small fiber diameters of less than 5mum were produced from TPU237, TPU245 and TPU280 pellets, and the mechanical strengths of MB TPU webs including the tensile strength, tear strength, abrasion resistance and tensile elongation were notably good. In addition, the statistical model showed useful interaction regarding trends for processing parameters versus properties of MB TPU webs. Die and air temperature showed multicollinearity problems and fiber diameter was notably affected by air flow rate, throughput and die/air temperature. It was also shown that most of the MB TPU web properties including mechanical strength, air permeability and fiber diameters were affected by air velocity and die temperature.

Lee, Youn Eung

30

Corrosion protection of carbon steel with thermoplastic coatings and alkyd resins containing polyaniline as conductive polymer  

Microsoft Academic Search

Protection against corrosion was evaluated for specimens of carbon steel coated with conventional thermoplastic polymers as a blend of poly(methyl methacrylate) with poly(butylmethacrlylate), phenoxy resin and a poly(vinyl chloride-co-vinyl acetate) 90\\/10 copolymer and compared with an alkyd resin containing 0.2, 0.4 and 0.6% (w\\/w) of polyaniline, a conductive polymer extensively investigated for its ability to protect metals against aqueous corrosion.

José Ignacio Iribarren Laco; Francisco Cadena Villota; Francisco Liesa Mestres

2005-01-01

31

Rapid, cost-efficient fabrication of microfluidic reactors in thermoplastic polymers by combining photolithography and hot embossing.  

PubMed

We report a cost-efficient and easy to implement process for fabricating microfluidic reactors in thermoplastic materials. The method includes (i) the fabrication of an imprint template (master), which consists of a photoresist deposited on a metal plate; (ii) the thermoembossing of the reactor features into polymer sheets; (iii) the activation of the embossed and planar thermoplastic surfaces; and (iv) the low-temperature bonding of these surfaces. The generality of the method is established by fabricating microfluidic reactors with a complex geometry in a range of thermoplastic polymers, including cycloolefin, polycarbonate, and UV-transparent acrylic polymers and by the multiple, high-fidelity use of the master. PMID:20126695

Greener, Jesse; Li, Wei; Ren, Judy; Voicu, Dan; Pakharenko, Viktoriya; Tang, Tian; Kumacheva, Eugenia

2010-02-21

32

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

NASA Astrophysics Data System (ADS)

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.

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

2006-09-01

33

Spall fracture characterization of thermosetting and thermoplastic polymer matrix composite plates  

Microsoft Academic Search

So-called spall fractures (through-the-thickness tensile impact fractures) in simple uniaxial strain were examined for typical glass fiber reinforced thermosetting and thermoplastic polymer composite plates. An exploding foil technique was used to accelerate thin flyer plates towards composite plates to generate spall fractures. For thermosetting polyester composites, different fiber surface treatments were applied to study the effects of interfacial strengths on

Nobuo Takeda; Haruo Komatsu; Kiyoshi Takahashi

1993-01-01

34

Optical emission spectroscopy studies of titanium nitride sputtering on thermoplastic polymers  

Microsoft Academic Search

A magnetron sputter ion plating (MSIP) 13.56MHz r.f. discharge for titanium nitride (TiN) deposition on thermoplastic polymers was studied by means of optical emission spectroscopy (OES). In this work poly(butylene terephthalate) (PBT) and poly(amide)6.6 (PA) were chosen as substrate materials. Argon sputter etch depth profiling and investigation of the chemical composition by means of X-ray photoelectron spectroscopy (XPS) showed high

M. Neuhäuser; S. Bärwulf; H. Hilgers; E. Lugscheider; M. Riester

1999-01-01

35

Thermodynamics of water sorption in high performance glassy thermoplastic polymers  

PubMed Central

Sorption thermodynamics of water in two glassy polymers, polyetherimide (PEI) and polyetheretherketone (PEEK), is investigated by coupling gravimetry and on line FTIR spectroscopy in order to gather information on the total amount of sorbed water as well as on the different species of water molecules absorbed within the polymers, addressing the issue of cross- and self-interactions occurring in the polymer/water systems. Water sorption isotherms have been determined at temperatures ranging from 30 to 70°C while FTIR spectroscopy has been performed only at 30°C. The experimental analysis provided information on the groups present on the polymer backbones involved in hydrogen bonding interactions with absorbed water molecules. Moreover, it also supplied qualitative indications about the different “populations” of water molecules present within the PEEK and a quantitative assessment of these “populations” in the case of PEI. The results of the experimental analysis have been interpreted using an equation of state theory based on a compressible lattice fluid model for the Gibbs energy of the polymer-water mixture, developed by extending to the case of out of equilibrium glassy polymers a previous model intended for equilibrium rubbery polymers. The model accounts for the non-equilibrium nature of glassy polymers as well as for mean field and for hydrogen bonding interactions, providing a satisfactory quantitative interpretation of the experimental data.

Scherillo, Giuseppe; Petretta, Mauro; Galizia, Michele; La Manna, Pietro; Musto, Pellegrino; Mensitieri, Giuseppe

2014-01-01

36

Morphology of sputtered titanium nitride thin films on thermoplastic polymers  

Microsoft Academic Search

The morphology of titanium nitride (TiN) thin films on poly(butylene terephthalate) and polyamide-6,6 was studied. The thin films were deposited on the polymer substrates by magnetron sputter ion plating (MSIP) with a thickness of about 1.5?m. The morphology of the coatings was visualized by scanning electron microscopy. The influence of the polymer substrates on the deposition process and the morphology

M. Riester; S. Bärwulf; E. Lugscheider; H. Hilgers

1999-01-01

37

Turning Renewable Resources into Recyclable Polymer: Development of Lignin-Based Thermoplastic  

SciTech Connect

Productive uses of lignin, the third most abundant natural polymer, have been sought for decades. One especially attractive possibility is that of developing value-added products including thermoplastics based on lignin. This possibility warrants special attention due to growth of the modern biofuel industries. However, the polydisperse molecular weight and hyper-branched structure of lignin has hindered the creation of high-performance biopolymers. Here, we report the preparation and characterization of novel lignin-based, partially carbon-neutral thermoplastics. We first altered the molecular weight of lignin, either by fractionation with methanol, or by formaldehyde crosslinking. A crosslinking of lignin increases the molecular weight, exhibiting Mn = 31000 g/mol, whereas that of native lignin is 1840 g/mol. Tuning the molecular weight of lignin enabled successful preparation of novel lignin-derived thermoplastics, when coupled with telechelic polybutadiene soft-segments at proper feed ratios. Characteristic to thermoplastic rubbers, free-standing films of the resulting copolymers exhibit two-phase morphology and associated relaxations in the dynamic mechanical loss spectrum. To our knowledge this article is the first report to demonstrate phase immiscibility, melt-processibility, and biphasic morphology of soft and hard segments in a lignin-based copolymer for all feed ratios of two macromolecular components. The use of higher molecular weight lignin enhanced the resulting shear modulus due to efficient network formation of telechelic polybutadiene bridges. The storage modulus in the rubbery plateau region increased with increasing lignin content. The successful synthesis of novel lignin-based thermoplastics will open a new pathway to biomass utilization and will help conserve petrochemicals.

Saito, Tomonori [ORNL; Brown, Rebecca H [ORNL; Hunt, Marcus A [ORNL; Pickel, Deanna L [ORNL; Pickel, Joseph M [ORNL; Messman, Jamie M [ORNL; Baker, Frederick S [ORNL; Keller, Martin [ORNL; Naskar, Amit K [ORNL

2012-01-01

38

Review of modern techniques to generate antireflective properties on thermoplastic polymers  

NASA Astrophysics Data System (ADS)

Modern optical applications need solutions for providing polymer surfaces with antireflective properties. The problems involved in coating comprise thermal limitations, incompatible mechanical properties of coating and substrate materials, and interaction between polymers and plasma. As an alternative for coating, antireflective properties on polymers can also be obtained by hot embossing or by ion etching of surface structures. My objective is to provide the criteria for choosing suitable deposition or structuring methods based on an understanding of plasma-, radiation-, and ion-induced surface phenomena; material compatibility; mechanical and environmental performance; and cost issues. The potential to produce antireflective interference coatings is documented for plasma-enhanced physical- and chemical-vapor-deposition methods, including modern hybrid techniques, as well as for solgel wet-chemical processes. The review about state-of-the-art coatings focuses on the thermoplastic acrylic, polycarbonate, and cycloolefin polymers.

Schulz, Ulrike

2006-03-01

39

RHEOLOGICAL PROPERTIES & MOLECULAR WEIGHT DISTRIBUTIONS OF FOUR PERFLUORINATED THERMOPLASTIC POLYMERS  

SciTech Connect

Dynamic viscosity measurements and molecular weight estimates have been made on four commercial, amorphous fluoropolymers with glass transitions (Tg) above 100 C: Teflon AF 1600, Hyflon AD 60, Cytop A and Cytop M. These polymers are of interest as binders for the insensitive high explosive 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) because of their high density and Tg above ambient, but within a suitable processing range of TATB. As part of this effort, the rheological properties and molecular weight distributions of these polymers were evaluated.

Hoffman, D M; Shields, A L

2009-02-24

40

Thermoplastic polymer patterning without residual layer by advanced nanoimprinting schemes  

NASA Astrophysics Data System (ADS)

Nanoimprinting is a fast-growing technique for nanoscale patterning. One of the remaining issues in nanoimprinting is the removal of the residual layer after nanoimprinting. Traditionally the residual layer is removed by an oxygen reactive-ion etching (RIE) step. The need for a vacuum environment and dedicated equipment in this step lowers the throughput and increases the cost of the nanoimprinting process. It also prevents the possibility of patterning isolated functional polymers because oxygen RIE destroys the functional materials. In this work, novel nanoimprinting schemes are developed to nondestructively remove the residual layer in thermal nanoimprinting by solvent developing and dewetting. Combined with a transfer-bonding technique, three-dimensional polymer scaffolds are achieved. The techniques developed here eliminate the RIE step in thermal nanoimprinting and are compatible with roller nanoimprinting for large-scale patterning of polymer micro- or nanostructures. The technique also opens up new applications for nanoimprinting in patterning isolated conjugated polymers for organic electronic devices and circuits.

Park, Hyunsoo; Cheng, Xing

2009-06-01

41

Biomedical application of commercial polymers and novel polyisobutylene-based thermoplastic elastomers for soft tissue replacement.  

PubMed

Novel polyisobutylene-based thermoplastic elastomers are introduced as prospective implant materials for soft tissue replacement and reconstruction. In comparison, poly(ethylene terephthalate) (PET), poly(tetrafluoroethylene) (PTFE), polypropylene (PP), polyurethanes (PU), and silicones are outlined from well-established implant history as being relatively inert and biocompatible biomaterials for soft tissue replacement, especially in vascular grafts and breast implants. Some general considerations for the design and development of polymers for soft tissue replacement are reviewed from the viewpoint of material science and engineering, with special attention to synthetic materials used in vascular grafts and breast implants. PMID:15244424

Puskas, Judit E; Chen, Yaohong

2004-01-01

42

[Studies on the mechanical properties of thermoplastic polymer resin materials for medical outside fixation].  

PubMed

Temperature scanning tests and uniaxial tensile tests at room temperature under different strain rates for three kinds of existing low-temperature outside fixed thermoplastic medical polymer resin materials (A, B and C) were conducted on dynamic mechanical analyzer and micro material testing machine to contrast their mechanical properties. It is shown that the glass transition temperatures of these three materials are all around 65 degrees C, but material C has the widest range of shaping temperature. Stress-strain responses of the three materials are rate-dependent and material C shows better plasticity. PMID:22826942

Chen, Jie; Zhang, Shubao; Chen, Xu

2012-06-01

43

Selecting and designing with the right thermoplastic polymer for your microfluidic chip: a close look into cyclo-olefin polymer  

NASA Astrophysics Data System (ADS)

Engineers who are developing microfluidic devices and bioMEMs for life science applications have many aspects to consider when selecting the proper base materials for constructing a device. While glass and polydimethylsiloxane (PDMS) are the staple materials for proof-of-concept and prototype chip fabrication, they are not a feasible solution for commercial production due to their slow, labor-intensive production rate. Alternatively, a molded or extruded thermoplastic solution can deliver the precision, consistency, and high volume capability required for commercial scale production. Traditional thermoplastics, such as polymethylmethacrylate (PMMA), polycarbonate (PC), and polystyrene (PS), are well known by development engineers in the bioscience community; however, cyclo-olefin polymer (COP), a relative newcomer in the world of plastics, is gaining increasing attention for use in microfluidic devices due to its unique balance of key properties compared to conventional thermoplastics. In this paper, we provide a comprehensive look at the properties which make COP an excellent candidate for providing the flow cell support and reagent storage functions in microfluidic assays. We also explore the processing attributes and capabilities of COP resin and film which are crucial for manufacturing high-performance microfluidic devices.

Nevitt, Mark

2013-03-01

44

Universal hydrophilic coating of thermoplastic polymers currently used in microfluidics.  

PubMed

A number of materials used to fabricate disposable microfluidic devices are hydrophobic in nature with water contact angles on their surface ranging from 80° to over 100°. This characteristic makes them unsuitable for a number of microfluidic applications. Both the wettability and analyte adsorption parameters are highly dependent on the surface hydrophobicity. In this article, we propose a general method to coat the surface of five materials: polydimethylsiloxane (PDMS), cyclic olefin copolymer (COC), polyethylene terephthalate (PET), polycarbonate (PC), and polytetrafluoroethylene (PTFE). This fast and robust process, which is easily implementable in any laboratory including microfabrication clean room facilities, was devised by combining gas-phase and wet chemical modification processes. Two different coatings that improve the surface hydrophilicity were prepared via the "dip and rinse" approach by immersing the plasma oxidized materials into an aqueous solution of two different poly(dimethylacrylamide) copolymers incorporating a silane moiety and functionalized with either N-acryloyloxysuccinimide (NAS) (poly(DMA-NAS-MAPS) or glycidyl methacrylate (GMA) (poly(DMA-GMA-MAPS). The coating formation was confirmed by contact angle (CA) analysis comparing the variation of CAs of uncoated and coated surfaces subjected to different aging treatments. The antifouling character of the polymer was demonstrated by fluorescence and interferometric detection of proteins adsorbed on the surafce. This method is of great interest in microfluidics due to its broad applicability to a number of materials with varying chemical compositions. PMID:24037663

Zilio, Caterina; Sola, Laura; Damin, Francesco; Faggioni, Lucia; Chiari, Marcella

2014-02-01

45

Casein and soybean protein-based thermoplastics and composites as alternative biodegradable polymers for biomedical applications.  

PubMed

This work reports on the development and characterization of novel meltable polymers and composites based on casein and soybean proteins. The effects of inert (Al(2)O(3)) and bioactive (tricalcium phosphate) ceramic reinforcements over the mechanical performance, water absorption, and bioactivity behavior of the injection-molded thermoplastics were examined. It was possible to obtain materials and composites with a range of mechanical properties, which might allow for their application in the biomedical field. The incorporation of tricalcium phosphate into the soybean thermoplastic decreased its mechanical properties but lead to the nucleation of a bioactive calcium-phosphate film on their surface when immersed in a simulated body fluid solution. When compounded with 1% of a zirconate coupling agent, the nucleation and growth of the bioactive films on the surface of the referred to composites was accelerated. The materials degradation was studied for ageing periods up to 60 days in an isotonic saline solution. Both water uptake and weight loss were monitored as a function of the immersion time. After 1 month of immersion, the materials showed signal of chemical degradation, presenting weight losses up to 30%. However, further improvement on the mechanical performance and the enhancement of the hydrolytic stability of those materials will be highly necessary for applications in the biomedical field. PMID:12635155

Vaz, C M; Fossen, M; van Tuil, R F; de Graaf, L A; Reis, R L; Cunha, A M

2003-04-01

46

Initiation of shape-memory effect by inductive heating of magnetic nanoparticles in thermoplastic polymers  

NASA Astrophysics Data System (ADS)

In shape-memory polymers, changes in shape are mostly induced by heating, and exceeding a specific switching temperature, Tswitch. If polymers cannot be warmed up by heat transfer using a hot liquid or gaseous medium, noncontact triggering will be required. In this article, the magnetically induced shape-memory effect of composites from magnetic nanoparticles and thermoplastic shape-memory polymers is introduced. A polyetherurethane (TFX) and a biodegradable multiblock copolymer (PDC) with poly(p-dioxanone) as hard segment and poly(-caprolactone) as soft segment were investigated as matrix component. Nanoparticles consisting of an iron(III)oxide core in a silica matrix could be processed into both polymers. A homogeneous particle distribution in TFX could be shown. Compounds have suitable elastic and thermal properties for the shape-memory functionalization. Temporary shapes of TFX compounds were obtained by elongating at increased temperature and subsequent cooling under constant stress. Cold-drawing of PDC compounds at 25°C resulted in temporary fixation of the mechanical deformation by 50-60%. The shape-memory effect of both composite systems could be induced by inductive heating in an alternating magnetic field (f = 258 kHz; H = 30 kA·m-1). The maximum temperatures achievable by inductive heating in a specific magnetic field depend on sample geometry and nanoparticle content. Shape recovery rates of composites resulting from magnetic triggering are comparable to those obtained by increasing the environmental temperature. nanocomposite | shape-memory polymer | stimuli-sensitive polymer


Mohr, R.; Kratz, K.; Weigel, T.; Lucka-Gabor, M.; Moneke, M.; Lendlein, A.

2006-03-01

47

Hemocompatibility of Inorganic Physical Vapor Deposition (PVD) Coatings on Thermoplastic Polyurethane Polymers.  

PubMed

Biocompatibility improvements for blood contacting materials are of increasing interest for implanted devices and interventional tools. The current study focuses on inorganic (titanium, titanium nitride, titanium oxide) as well as diamond-like carbon (DLC) coating materials on polymer surfaces (thermoplastic polyurethane), deposited by magnetron sputtering und pulsed laser deposition at room temperature. DLC was used pure (a-C:H) as well as doped with silicon, titanium, and nitrogen + titanium (a-C:H:Si, a-C:H:Ti, a-C:H:N:Ti). In-vitro testing of the hemocompatibility requires mandatory dynamic test conditions to simulate in-vivo conditions, e.g., realized by a cone-and-plate analyzer. In such tests, titanium- and nitrogen-doped DLC and titanium nitride were found to be optimally anti-thrombotic and better than state-of-the-art polyurethane polymers. This is mainly due to the low tendency to platelet microparticle formation, a high content of remaining platelets in the whole blood after testing and low concentration of platelet activation and aggregation markers. Comparing this result to shear-flow induced cell motility tests with e.g., Dictostelium discoideum cell model organism reveals similar tendencies for the investigated materials. PMID:24955532

Lackner, Juergen M; Waldhauser, Wolfgang; Hartmann, Paul; Bruckert, Franz; Weidenhaupt, Marianne; Major, Roman; Sanak, Marek; Wiesinger, Martin; Heim, Daniel

2012-01-01

48

Hemocompatibility of Inorganic Physical Vapor Deposition (PVD) Coatings on Thermoplastic Polyurethane Polymers  

PubMed Central

Biocompatibility improvements for blood contacting materials are of increasing interest for implanted devices and interventional tools. The current study focuses on inorganic (titanium, titanium nitride, titanium oxide) as well as diamond-like carbon (DLC) coating materials on polymer surfaces (thermoplastic polyurethane), deposited by magnetron sputtering und pulsed laser deposition at room temperature. DLC was used pure (a-C:H) as well as doped with silicon, titanium, and nitrogen + titanium (a-C:H:Si, a-C:H:Ti, a-C:H:N:Ti). In-vitro testing of the hemocompatibility requires mandatory dynamic test conditions to simulate in-vivo conditions, e.g., realized by a cone-and-plate analyzer. In such tests, titanium- and nitrogen-doped DLC and titanium nitride were found to be optimally anti-thrombotic and better than state-of-the-art polyurethane polymers. This is mainly due to the low tendency to platelet microparticle formation, a high content of remaining platelets in the whole blood after testing and low concentration of platelet activation and aggregation markers. Comparing this result to shear-flow induced cell motility tests with e.g., Dictostelium discoideum cell model organism reveals similar tendencies for the investigated materials.

Lackner, Juergen M.; Waldhauser, Wolfgang; Hartmann, Paul; Bruckert, Franz; Weidenhaupt, Marianne; Major, Roman; Sanak, Marek; Wiesinger, Martin; Heim, Daniel

2012-01-01

49

Study of Double-Side Ultrasonic Embossing for Fabrication of Microstructures on Thermoplastic Polymer Substrates  

PubMed Central

Double-side replication of polymer substrates is beneficial to the design and the fabrication of 3-demensional devices. The ultrasonic embossing method is a promising, high efficiency and low cost replication method for thermoplastic substrates. It is convenient to apply silicon molds in ultrasonic embossing, because microstructures can be easily fabricated on silicon wafers with etching techniques. To reduce the risk of damaging to silicon molds and to improve the replication uniformity on both sides of the polymer substrates, thermal assisted ultrasonic embossing method was proposed and tested. The processing parameters for the replication of polymethyl methacrylate (PMMA), including ultrasonic amplitude, ultrasonic force, ultrasonic time, and thermal assisted temperature were studied using orthogonal array experiments. The influences of the substrate thickness, pattern style and density were also investigated. The experiment results show that the principal parameters for the upper and lower surface replication are ultrasonic amplitude and thermal assisted temperature, respectively. As to the replication uniformity on both sides, the ultrasonic force has the maximal influence. Using the optimized parameters, the replication rate reached 97.5% on both sides of the PMMA substrate, and the cycle time was less than 50 s.

Luo, Yi; Yan, Xu; Qi, Na; Wang, Xiaodong; Wang, Liangjiang

2013-01-01

50

Membrane consisting of polyquaternary amine ion exchange polymer network interpenetrating the chains of thermoplastic matrix polymer  

NASA Technical Reports Server (NTRS)

An ion exchange membrane was formed from a solution containing dissolved matrix polymer and a set of monomers which are capable of reacting to form a polyquaternary ion exchange material; for example vinyl pyride and a dihalo hydrocarbon. After casting solution and evaporation of the volatile component's, a relatively strong ion exchange membrane was obtained which is capable of removing anions, such as nitrate or chromate from water. The ion exchange polymer forms an interpenetrating network with the chains of the matrix polymer.

Rembaum, A.; Wallace, C. J. (inventors)

1978-01-01

51

Towards tunable sensitivity of electrical property to strain for conductive polymer composites based on thermoplastic elastomer.  

PubMed

The use of conductive polymer composites (CPCs) as strain sensors has been widely investigated and various resistivity-strain sensitivities are desirable for different applications. In this study, the use of mixed carbon fillers and functionalized carbon nanotubes was demonstrated to be vital for preparing thermoplastic polyurethane (TPU)-based strain sensors with tunable sensitivity. To understand the strain sensing behavior, we carried out scanning electron microscopy (SEM), Raman spectroscopy, wide-angle X-ray diffraction (WAXD), mechanical test, and rheology-electrical measurement. Hybrid fillers of multi-walled carbon nanotubes (MWNTs) and carbon black (CB) could reduce the entanglement in conductive network structure, thus increase the resistivity-strain sensitivity. Furthermore, incorporation of additional functionalized MWNTs in the CPCs could enhance the interfacial interaction between nanofillers and TPU, leading to further increase in sensitivity. Through such a simple method, strain sensors could be efficiently fabricated with large strain-sensing capability (strain as large as 200%) and a wide range of strain sensitivity (gauge factor ranging from 5 to 140238). Finally, the exponential revolution of resistive response to strain was fitted with a model based on tunneling theory by Simmons. It was observed that the change in tunneling distance and the number of conductive pathways could be accelerated significantly by adjusting conductive network structure and interfacial interaction. This study provides a guideline for the preparation of high-performance CPC strain sensors with a large range of resistivity-strain sensitivity. PMID:23713404

Lin, Lin; Liu, Siyao; Zhang, Qi; Li, Xiaoyu; Ji, Mizhi; Deng, Hua; Fu, Qiang

2013-06-26

52

Modeling and Simulation of the Flow of a Thermoplastic Polymer during Filling of a Cylindrical Micro-Cavity  

NASA Astrophysics Data System (ADS)

This work is related to experiments and modelling concerning viscous polymer flow such as cyclo-olefin polymer (COP) and cyco-olefin copolymer (COC) arising in the hot embossing process in order to understand and predict the filling of microcavities. The simulation results are obtained for axisymmetric geometries. The filling time and the dimensions of polymer with the rheological and experimental process parameters are obtained. From the variations of the radius characterizing the squeeze flow of the polymers between plates with or without cavities, it is possible to relate the rheological properties (fluidity index, consistency, melt flow index and viscosity) to the aptitude of the polymers to reproduce the geometrical shape and surface asperities of a microstructured mould. The flow imposed to the polymeric material in shear or elongational mode was correlated to the rheological approach. This approach allows to better understand the compression of thermoplastic disks as well as the filling mechanism of cylindrical cavities while providing a predictive approach for the of embossing pressure during the process.

Sahli, M.; Gelin, J. C.; Malek, C. Khan; Roques-Carmes, C.

2007-05-01

53

Impact Properties of the Polymer Blend of Polypropylene and Thermoplastic Elastomer  

Microsoft Academic Search

Improvement of the impact strength with little sacrifice of the modulus for polypropylene (PP) blends was investigated by blending PP with isoprene-styrene block copolymers (ISR-A, B, C, and D) and ethylene-propylene random copolymer as thermoplastic elastomers. Neither of the blends whose flexural modulus ranged from 1530 MPa, that of PP, to 1400 MPa showed a significant improvement of the notched

Mitsuhiro Shibata; Zhu Xiaochuan; Ryutoku Yosomiya

1998-01-01

54

Welding methods for joining thermoplastic polymers for the hermetic enclosure of medical devices  

Microsoft Academic Search

New high performance polymers have been developed that challenge traditional encapsulation materials for permanent active medical implants. The gold standard for hermetic encapsulation for implants is a titanium enclosure which is sealed using laser welding. Polymers may be an alternative encapsulation material. Although many polymers are biocompatible, and permeability of polymers may be reduced to acceptable levels, the ability to

Negin Amanat; Natalie L. James; David R. McKenzie

2010-01-01

55

Melt Mixing as Method to Disperse Carbon Nanotubes into Thermoplastic Polymers  

Microsoft Academic Search

This paper presents melt mixed composites where two ways of introducing nanotubes in polymer matrices were used. In the first case, commercially available masterbatches of nanotube\\/polymer composites are used as the starting materials that are diluted by the pure polymer in a subsequent melt mixing process (masterbatch dilution method) while in the other case nanotubes are directly incorporated into the

Petra Pötschke; Arup R. Bhattacharyya; Andreas Janke; Sven Pegel; Albrecht Leonhardt; Christine Täschner; Manfred Ritschel; Siegmar Roth; Björn Hornbostel; Jiri Cech

2005-01-01

56

Composition of the interface region of sputtered titanium nitride thin films on thermoplastic polymers  

Microsoft Academic Search

The interface of poly(butylene terephthalate) (PBT) and sputtered titanium nitride (TiN) thin films was studied. The thin films were deposited by magnetron sputter ion plating (MSIP) onto the polymer. The interface analysis was performed after the deposition process, in which a layer of approximately 60nm of titanium nitride was formed on the polymer. The influence of the plasma pretreatment parameters:

M. Riester; S. Bärwulf; E. Lugscheider; H. Hilgers

1999-01-01

57

Preparation of Thermoplastic X-ray Masks for Medical Applications  

Microsoft Academic Search

The objective of this thesis was to study the appropriate polymer for preparation of thermoplastic masks for medical applications. The commercial thermoplastic mask was characterized by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The results indicated that the type of polymer being used is polycaprolactone. The tensile strength, hardness and impact strength of the commercial thermoplastic mask

Jindarat Pimsamarn

58

Processable Aromatic Polyimide Thermoplastic Blends  

NASA Technical Reports Server (NTRS)

Method developed for preparing readily-processable thermoplastic polyimides by blending linear, high-molecular-weight, polyimic acid solutions in ether solvents with ultrafine, semicrystalline, thermoplastic polyimide powders. Slurries formed used to make prepregs. Consolidation of prepregs into finsihed composites characterized by excellent melt flow during processing. Applied to film, fiber, fabric, metal, polymer, or composite surfaces. Used to make various stable slurries from which prepregs prepared.

Baucom, Robert M; Johnston, Norman J.; St. Clair, Terry L.; Nelson, James B.; Gleason, John R.; Proctor, K. Mason

1988-01-01

59

Thermoplastic Electronic Packaging: Low Cost - High Versatility  

Microsoft Academic Search

Thermoplastics have started to gain acceptance in some of the more challenging areas of advanced packaging, including MEMS, where lower cost, cavity style packages are required. Thermoplastics, like LCP, PPS and PEEK, can withstand exposure to over 300oC thus assuring lead-free solder capability. Many polymers offer superior moisture resistance, can be formed into micro-precision packages in just seconds, and are

Ken Gilleo; RI Rita Mohanty; Gerald Pham-Van-Diep; Dennis Jones

60

Surface characterization in composite and titanium bonding: Carbon fiber surface treatments for improved adhesion to thermoplastic polymers  

NASA Technical Reports Server (NTRS)

The effect of anodization in NaOH, H2SO4, and amine salts on the surface chemistry of carbon fibers was examined by X-ray photoelectron spectroscopy (XPS). The surfaces of carbon fibers after anodization in NaOH and H2SO4 were examined by scanning transmission electron microscopy (STEM), angular dependent XPS, UV absorption spectroscopy of the anodization bath, secondary ion mass spectrometry, and polar/dispersive surface energy analysis. Hercules AS-4, Dexter Hysol XAS, and Union Carbide T-300 fibers were examined by STEM, angular dependent XPS, and breaking strength measurement before and after commercial surface treatment. Oxygen and nitrogen were added to the fiber surfaces by anodization in amine salts. Analysis of the plasmon peak in the carbon 1s signal indicated that H2SO4 anodization affected the morphological structure of the carbon fiber surface. The work of adhesion of carbon fibers to thermoplastic resins was calculated using the geometric mean relationship. A correlation was observed between the dispersive component of the work of adhesion and the interfacial adhesion.

Devilbiss, T. A.; Wightman, J. P.

1987-01-01

61

Electrostatic prepregging of thermoplastic matrices  

NASA Technical Reports Server (NTRS)

Thermoplastic towpregs of PEEK/AS-4, PEEK/S-2 glass and LaRC-TPI/AS-4, produced by electrostatic deposition of charged and fluidized polymer powders on spread continuous fiber tows, are described. Processing parameters for combining PEEK 150 powder with unsized 3k AS-4 carbon fiber are presented. The experimental results for PEEK 150/AS-4 reveal that electrostatic fluidized bed coating may be an economically attractive process for producing towpreg.

Muzzy, John D.; Varughese, Babu; Thammongkol, Vivan; Tincher, Wayne

1989-01-01

62

Fabrication and characterization of a foamed polylactic acid (PLA)/ thermoplastic polyurethane (TPU) shape memory polymer (SMP) blend for biomedical and clinical applications  

NASA Astrophysics Data System (ADS)

Shape memory polymers (SMP) are a class of stimuli-responsive materials that are able to respond to external stimulus such as heat by altering their shape. Bio-compatible SMPs have a number of advantages over static materials and are being studied extensively for biomedical and clinical applications (such as tissue stents and scaffolds). A previous study has demonstrated that the bio-compatible polymer blend of polylactic acid (PLA)/ thermoplastic polyurethane (TPU) (50/50 and 70/30) exhibit good shape memory properties. In this study, the mechanical and thermo-mechanical (shape memory) properties of TPU/PLA SMP blends were characterized; the compositions studied were 80/20, 65/35, and 50/50 TPU/PLA. In addition, porous TPU/PLA SMP blends were fabricated with a gas-foaming technique; and the morphology of the porous structure of these SMPs foams were characterized with scanning electron microscopy (SEM). The TPU/PLA bio-compatible SMP blend was fabricated with melt-blending and compression molding. The glass transition temperature (Tg) of the SMP blends was determined with a differential scanning calorimeter (DSC). The mechanical properties studied were the stress-strain behavior, tensile strength, and elastic modulus; and the thermomechanical (or shape memory) properties studied were the shape fixity rate (Rf), shape recovery rate (Rr), response time, and the effect of recovery temperature on Rr. The porous 80/20 PLA/TPU SMP blend was found to have the highest tensile strength, toughness and percentage extension, as well as the lowest density and uniform pore structure in the micron and submicron scale. The porous 80/20 TPU/PLA SMP blend may be further developed for specific biomedical and clinical applications where a combination of tensile strength, toughness, and low density are required.

Song, Janice J.; Srivastava, Ijya; Kowalski, Jennifer; Naguib, Hani E.

2014-03-01

63

A thermoplastic copolyimide  

NASA Technical Reports Server (NTRS)

A copolyimide, STPI/LARC, was prepared from the reaction of 3,3'4,4'-benzophenonetetracarboxylic dianhydride (BTDA), equimolar quantities of m-phenylenediamine and 4,4'-oxydianiline, and a small amount of phthalic anhydride to control the molecular weight. The processability and adhesive properties of STPI/LARC were compared to those of a commercially available form of LARC-TPI. LARC-TPI, a thermoplastic polyimide, from the reaction of BTDA and 3,3'-diaminobenzophenone, had previously shown promise as a high temperature structural adhesive. Lap shear specimens were fabricated using adhesive tape prepared from each of the two polymers. Lap shear tests were performed at room temperature, 177 C, and 204 C before and after exposure to a 72-hour water-boil and to aging at 204 C.

Progar, D. J.; St. Clair, T. L.

1985-01-01

64

Thermoplastic-carbon fiber hybrid yarn  

NASA Technical Reports Server (NTRS)

Efforts were directed to develop processing methods to make carbon fiber/thermoplastic fiber preforms that are easy to handle and drapeable, and to consolidate them into low void content laminates. The objectives were attained with the development of the hybrid yarn concept; whereby, thermoplastic fiber can be intimately intermixed with carbon fiber into a hybrid yarn. This was demonstrated with the intermixing of Celion 3000 with a Celanese liquid crystal polymer fiber, polybutylene terepthalate fiber, or polyetheretherketone fiber. The intermixing of the thermoplastic matrix fiber and the reinforcing carbon fiber gives a preform that can be easily fabricated into laminates with low void content. Mechanical properties of the laminates were not optimized; however, initial results indicated properties typical of a thermoplastic/carbon fiber composites prepared by more conventional methods.

Ketterer, M. E.

1984-01-01

65

Poly(2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylenevinylene) conjugated polymer domains in a thermoplastic polyurethane matrix  

NASA Astrophysics Data System (ADS)

Self-sustained and spin-casting films formed from blends of poly(2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylenevinylene) (MEH-PPV) conjugated polymer and thermoplastic poly-urethane (TPU) at different concentrations have been investigated. Scanning electron microscopy images of self-sustained films show the formation of circularlike domains of MEH-PPV in the TPU matrix, characterizing the blend material as heterogeneous. The circularlike domains in the spin-casting films were also observed by electric force microscopy (EFM) and by atomic force microscopy. The EFM, in particular, has allowed the differentiation of the MEH-PPV domains from the TPU matrix due to the electrical properties of the conjugated polymer. The MEH-PPV domains in the spin-casting films are much smaller in size than in the case of self-sustained films. The glass transition temperatures for the TPU and for the self-sustained blended films were obtained by temperature modulated differential scanning calorimetry. A very small variation in the glass transition temperature (Tg) has been observed for the blends. This fact further corroborates that MEH-PPV and TPU form immiscible blends. Intermolecular interactions between the MEH-PPV and the TPU materials were proposed to occur at the interfaces of the domains. These interfacial interactions have not affected the Raman modes, which pointed out that they are relatively weak interactions. The formation of small conjugation segments of the MEH-PPV molecules due to these interfacial interactions with the TPU molecules at the interfaces of the domains was assigned to be responsible by the appearance of a large tail and clear shoulders to the high energy side of the photoluminescence (PL) spectra of self-sustained samples. This was also assigned to be responsible by the blueshift observed in the PL spectra of spin-casting films. The redshift of the pure electronic transition peak and the first vibronic band (which presents an inhomogeneous broadening) were observed in the self-sustained blended films and were related, respectively, to the increase of the internal intermolecular and intramolecular interactions due to the conformational disorder of the MEH-PPV molecules imposed by the casting spread technique.

Patrício, Patrícia S. O.; Silva, Glaura G.; de Oliveira, Flávio A. C.; Righi, Ariete; Neves, Bernardo R. A.; Cury, Luiz A.

2007-02-01

66

Effect of annealing history on free volume in thermoplastics  

NASA Technical Reports Server (NTRS)

Two different types of thermoplastic glassy polymers have been investigated for the effects of thermal annealing on their free volumes. It has been observed that free volumes in glassy polymers decrease asymptotically to a steady level after about four thermal anneals lasting for 24 hours at a temperature about 50 C below their glass transition temperatures. These results indicate that composites incorporating properly annealed thermoplastic matrices may not experience any additional internal stresses due to subsequent thermal excursions experienced while in service.

Singh, J. J.; St.clair, T. L.

1986-01-01

67

Rolling Friction of Polymeric Materials. II. Thermoplastics  

Microsoft Academic Search

The results of rolling friction studies of several thermoplastics provide additional evidence for the correlation of such friction with dynamic mechanical losses in polymeric materials. Among the polymers discussed are polymethyl methacrylate, polytetrafluoroethylene, polyethylene, nylon, polyvinyl chloride, polyvinyl acetate, and polystyrene. The effects of spin and other deviations from pure rolling are demonstrated for polymethyl methacrylate, polytetrafluoroethylene, and nylon by

D. G. Flom

1961-01-01

68

Silicon-Phthalocyanine-Siloxane Polymers.  

National Technical Information Service (NTIS)

The invention pertains generally to inorganic polymer synthesis, and in particular to highly thermally stable silicon containing thermoplastic polymers. A number of modified siloxane polymers have been prepared. Although polymers based on poly(dimethyl si...

K. J. Wynne J. Davidson

1978-01-01

69

Nucleation in Microcellular Thermoplastic Foams  

NASA Astrophysics Data System (ADS)

Amorphous, thermoplastic polymers are foamed using inert gases such as carbon dioxide or nitrogen to create a microcellular foam. The small cell size, smaller than critical flaws already present in most polymers, allows the microcellular foam to retain some critical mechanical properties present in the bulk material. Microcellular foams with a cell density greater than 10^8 cells/cm^3 and an average cell size of order 10 microns or less, have been succesfully produced in amorphous polymers such as polystyrene, poly(methyl methacrylate) and polycarbonate. Current processing methods make it difficult to achieve a high cell nucleation density. In an effort to control the cell nucleation density, heterogeneous nucleation sites, both solid particle sites and in the form of block copolymer micelles, have been added to polystyrene samples. Batch experiments using carbon dioxide gas reveal anomalous trends in nucleation behavior that can not be explained by the classical nucleation theory, prompting further inquiry into its validity.

Spitael, Pieter; Macosko, Christopher W.

2000-03-01

70

Thermoplastic coating of carbon fibers  

NASA Technical Reports Server (NTRS)

A continuous powder coating system was developed for coating carbon fiber with LaRC-TPI (Langley Research Center-Thermoplastic Polyimide), a high-temperature thermoplastic polymide invented by NASA-Langley. The coating line developed used a pneumatic fiber spreader to separate the individual fibers. The polymer was applied within a recirculating powder coating chamber then melted using a combination of direct electrical resistance and convective heating to make it adhere to the fiber tow. The tension and speed of the line were controlled with a dancer arm and an electrically driven fiber wind-up and wind-off. The effects of heating during the coating process on the flexibility of the prepreg produced were investigated. The uniformity with which the fiber tow could be coated with polymer also was examined. Composite specimens were fabricated from the prepreg and tested to determine optimum process conditions. The study showed that a very uniform and flexible prepeg with up to 50 percent by volume polymer could be produced with this powder coating system. The coating line minimized powder loss and produced prepeg in lengths of up to 300 m. The fiber spreading was found to have a major effect on the coating uniformity and flexibility. Though test results showed low composite tensile strengths, analysis of fracture surfaces under scanning electron microscope indicated that fiber/matrix adhesion was adequate.

Edie, D. D.; Lickfield, G. C.; Allen, L. E.; Mccollum, J. R.

1989-01-01

71

Thermoplastic coated carbon fibers for textile preforms  

NASA Technical Reports Server (NTRS)

A continuous process for producing prepreg from carbon fiber and thermoplastic matrix is described. After the tow has been spread using a pneumatic device, the process utilizes a fluidized bed to apply thermoplastic powder to the bundle. Finally, direct electrical heating of the coated fiber tow melts the polymer on the individual fibers, creating a uniform and extremely flexible prepreg. The efficiency of the process was evaluated during initial trials in which a thermoplastic polyimide, LaRC-TPI, was applied to T-300, 3K (3000 filament) carbon fiber tow. The physical properties of unidirectional composite specimens fabricated from this prepreg were measured, and the matrix uniformity and void content of the samples was determined. The results of these evaluations are detailed and discussed.

Allen, L. E.; Edie, D. D.; Lickfield, G. C.; Mccollum, J. R.

1988-01-01

72

An investigation of physical properties of thermoplastic polyimides  

NASA Technical Reports Server (NTRS)

Thermoplastic polyimides are a class of promising high temperature polymers for aerospace applications. NASA-developed LARC-TPI is a prominent member of this family of polymers. Its physical characteristics have been measured as a function of its curing schedule. The results and their possible interpretations are discussed.

Singh, Jag J.; Stoakley, Diane M.

1987-01-01

73

PVD coating for optical applications on temperature-resistant thermoplastics  

NASA Astrophysics Data System (ADS)

The performance of the high temperature resistant polymers Pleximid, APEC and Ultrason as substrate materials in plasma-assisted physical vapor deposition processes was studied and compared with well-known thermoplastics for optical applications. Different effects of UV irradiation and plasma exposure on the polymers' optical features, surface energy and adhesion properties for oxide layers, typically used for interference multilayer coatings, are shown.

Munzert, Peter; Schulz, Ulrike; Kaiser, Norbert

2004-02-01

74

VARTM & RTM Processing of PBT & PA Thermoplastic Composites.  

National Technical Information Service (NTIS)

Vacuum assisted resin transfer molding (VARTM) and resin transfer molding (RTM) processes have been successfully developed to enable infusion of thermoplastic pre-polymers into glass and carbon fiber performs at temperatures up to 210 deg C. The pre-polym...

P. J. Mallon M. A. Dweib S. Ziaee A. Chatterjee J. W. Gillespie

2002-01-01

75

Antimicrobial thermoplastic materials for biomedical applications prepared by melt processing  

NASA Astrophysics Data System (ADS)

In this work thermoplastic polymers with antimicrobial properties were prepared by incorporating an antibiotic, i.e., ciprofloxacin (CFX), by melt processing. Two different polymers were used as matrices, i.e., polypropylene (PP) and poly(lactid acid) (PLA) and different concentrations of CFX have been incorporated. The antimicrobial properties, the release kinetic and the mechanical performances of the prepared materials were evaluated.

Botta, L.; Scaffaro, R.; Ceraulo, M.; Gallo, G.

2014-05-01

76

Organic Polymers Modified with Inorganic Polyhedra.  

National Technical Information Service (NTIS)

Nanostructured composites of thermoplastics and inorganic clusters have been developed by incorporating polyhedral oligomeric silsesquioxane (POSS) macromers into organic polymers. These hybrid inorganic/organic thermoplastics based on styrenes, acrylics,...

T. S. Haddad B. D. Viers

2002-01-01

77

The relative fire resistance of select thermoplastic materials. [for aircraft interiors  

NASA Technical Reports Server (NTRS)

The relative thermal stability, flammability, and related thermochemical properties of some thermoplastic materials currently used in aircraft interiors as well as of some candidate thermoplastics were investigated. Currently used materials that were evaluated include acrylonitrile butadiene styrene, bisphenol A polycarbonate, polyphenylene oxide, and polyvinyl fluoride. Candidate thermoplastic materials evaluated include: 9,9-bis(4-hydroxyphenyl)fluorene polycarbonate-poly(dimethylsiloxane) block polymer, chlorinated polyvinylchloride homopolymer, phenolphthalein polycarbonate, polyethersulfone, polyphenylene sulfide, polyarylsulfone, and polyvinylidene fluoride.

Kourtides, D. A.; Parker, J. A.

1978-01-01

78

High performance LDPE\\/thermoplastic starch blends: a sustainable alternative to pure polyethylene  

Microsoft Academic Search

Thermoplastic starch (TPS), as opposed to dry starch, is capable of flow and hence when mixed with other synthetic polymers can behave in a manner similar to conventional polymer–polymer blends. This paper presents an approach to preparing polyethylene\\/thermoplastic starch blends with unique properties. A one-step combined twin-screw\\/single screw extrusion setup is used to carry out the melt–melt mixing of the

F. J Rodriguez-Gonzalez; B. A Ramsay; B. D Favis

2003-01-01

79

Advanced Thermoplastic Resins, Phase 1.  

National Technical Information Service (NTIS)

Eight thermoplastic polyimide resin systems were evaluated as composite matrix materials. Two resins were selected for more extensive mechanical testing and both were versions of LaRC-TPI (Langley Research Center - Thermoplastic Polyimide). One resin was ...

C. L. Hendricks S. G. Hill A. Falcone N. T. Gerken

1991-01-01

80

Graphite Fiber Reinforced Thermoplastic Resins.  

National Technical Information Service (NTIS)

The results of a program designed to optimize the fabrication procedures for graphite thermoplastic composites are described. The properties of the composites as a function of temperature were measured and graphite thermoplastic fan exit guide vanes were ...

R. C. Navak

1977-01-01

81

Pen microfluidics: rapid desktop manufacturing of sealed thermoplastic microchannels  

PubMed Central

A unique technique for the rapid fabrication of thermoplastic microfluidic chips is described. The method enables the realization of fully-sealed microchannels in around one hour while requiring only minimal infrastructure by taking advantage of a solvent swelling mechanism that allows raised features to be patterned on the surface of homogeneous thermoplastic materials. Patterning is achieved without photolithography by simply drawing the desired microchannel pattern onto the polymer surface using a suitable ink as a masking layer, either manually or under robotic control, followed by timed exposure to solvent vapor to yield a desired depth for the masked channel features. The channels are then permanently sealed through solvent bonding of the microchannel chip to a mating thermoplastic substrate. The process is demonstrated using cyclic olefin copolymer as a thermoplastic material, with fully operational microfluidic devices fabricated following a true desktop manufacturing model suitable for rapid prototyping.

Rahmanian, Omid

2013-01-01

82

Pen microfluidics: rapid desktop manufacturing of sealed thermoplastic microchannels.  

PubMed

A unique technique for the rapid fabrication of thermoplastic microfluidic chips is described. The method enables the realization of fully-sealed microchannels in around one hour while requiring only minimal infrastructure by taking advantage of a solvent swelling mechanism that allows raised features to be patterned on the surface of homogeneous thermoplastic materials. Patterning is achieved without photolithography by simply drawing the desired microchannel pattern onto the polymer surface using a suitable ink as a masking layer, either manually or under robotic control, followed by timed exposure to solvent vapor to yield a desired depth for the masked channel features. The channels are then permanently sealed through solvent bonding of the microchannel chip to a mating thermoplastic substrate. The process is demonstrated using cyclic olefin copolymer as a thermoplastic material, with fully operational microfluidic devices fabricated following a true desktop manufacturing model suitable for rapid prototyping. PMID:23344819

Rahmanian, Omid; DeVoe, Don L

2013-03-21

83

Pultrusion process development of a graphite reinforced polyetherimide thermoplastic composite  

NASA Technical Reports Server (NTRS)

High performance thermoplastic polymers do not contain reactants and solvents able to react with a pultrusion die to yield polymerization; consolidation is therefore performed with a rigid or a boardy prepreg, and consolidation must occur with polymers whose viscosities are of the order of 1 million centipoises or more. Die temperatures are typically above 400 C, by comparison with the 150-200 C encountered in thermosets. A methodical approach is presented here for the development of a pultrusion process suitable for polyetherimide and other engineering thermoplastics, employing SEM, DSC, TGA, and ultrasonic C-scanning.

Wilson, Maywood L.; Buckley, John D.; Dickerson, George E.; Johnson, Gary S.; Taylor, Edward C.; Covington, Edward W.

1989-01-01

84

LARC-I-TPI: A New Thermoplastic Polyimide  

NASA Technical Reports Server (NTRS)

"LARC-I-TPI" denotes improved version of LARC-TPI class of thermoplastic polyimides: high-performance polymers developed for manufacture of strong, lightweight aircraft structures. Melt-flow and adhesive properties of new polymers make them attractive for use as matrix resins for composites, molding powders, adhesives, and coating films. Less toxic, improved LARC-I-TPI polymers formulated without 3, 3'-diaminobenzophenone, which is mutagenic and commercially unavailable.

St. Clair, Terry L.; Progar, Donald J.; Pratt, J. Richard

1990-01-01

85

Welds in thermoplastic composite materials  

Microsoft Academic Search

Welding methods are reviewed that can be effectively used for joining of thermoplastic composites and continuous-fiber thermoplastics. Attention is given to the use of ultrasonic, vibration, hot-plate, resistance, and induction welding techniques. The welding techniques are shown to provide complementary weld qualities for the range of thermoplastic materials that are of interest to industrial and technological applications.

N. S. Taylor

1990-01-01

86

Welds in thermoplastic composite materials  

NASA Astrophysics Data System (ADS)

Welding methods are reviewed that can be effectively used for joining of thermoplastic composites and continuous-fiber thermoplastics. Attention is given to the use of ultrasonic, vibration, hot-plate, resistance, and induction welding techniques. The welding techniques are shown to provide complementary weld qualities for the range of thermoplastic materials that are of interest to industrial and technological applications.

Taylor, N. S.

87

Evaluation of the thermoplasticity of different gutta-percha cones and Resilon.  

PubMed

The goal of this study was to evaluate the thermoplasticity of conventional and thermoplastic gutta-percha and Resilon, a polyester polymer-based material. Specimens with standardised dimensions were made from the following materials: conventional and thermoplastic gutta-percha (Dentsply), conventional and thermoplastic gutta-percha (Endopoints) and Resilon. After 24 h, the specimens were placed in water at 70 degrees C for 60 s, and thereafter positioned between two glass slabs. Each set was compressed by a 5-kg weight. Digital images of the specimens before and after compression were obtained and analysed. The thermoplasticity of each material was confirmed by the difference between final and initial areas of each sample. The data were analysed statistically by anova and Tukey's test at a 5% significance level. Resilon had the highest thermoplasticity means (P < 0.05). Among the gutta-percha cones, Endopoints TP (thermoplastic) presented the highest thermoplasticity means and differed significantly from the other commercial brands (P < 0.05). Resilon had good thermoplasticity, endorsing its use as a thermoplastic root canal filling material. PMID:17461837

Tanomaru-Filho, Mário; Silveira, Geraldine Faccio; Tanomaru, Juliane Maria Guerreiro; Bier, Carlos Alexandre Souza

2007-04-01

88

Thermoplastic Elastomer LOVA Binders.  

National Technical Information Service (NTIS)

The following thermoplastic elastomers (TPE) have been synthesized, characterized, and some of them submitted to DOD laboratories for evaluation: multiblock poly(acetal) poly(urethanes), where the poly(acetals) are poly(1,3,6trioxocane derivatives) and (1...

J. C. Chien

1991-01-01

89

Preparation and characterization of magnetic thermoplastic-based nanocomposites  

NASA Astrophysics Data System (ADS)

We developed a facile method for the preparation of magnetic nanocomposites based on the popular thermoplastic, acrylonitrile butadiene styrene (ABS). The nanocomposites were produced by liquid blending of ABS and Ni nanorods (NRs), followed by solvent evaporation. The characterizations showed that the nanocomposites were magnetic and Ni NRs were uniformly distributed in polymer matrix.

Thu, T. V.; Takamura, T.; Tsetserukou, D.; Sandhu, A.

2014-02-01

90

Fully integrated single-walled carbon nanotube thermoplastic composites  

Microsoft Academic Search

The development of composites of single-walled carbon nanotubes (SWNTs) with thermoplastics requires methods for good dispersion and achieving good interaction between SWNTs and the matrix. This thesis presents a new method to achieve good dispersion by a preliminary treatment called incipient wetting. The SWNTs dispersed in a solvent are mixed with polymer particles and deposited over them as the solvent

Fernando J. Rodriguez-Macias

2004-01-01

91

Thermoplastic Polyurethane-Encapsulated Melamine Phosphate Flame Retardant Polyoxymethylene  

Microsoft Academic Search

Due to its “unzipping” degradation mode and poor compatibility with most other flame retardants, polyoxymethylene (POM) is the most difficult flame-retarded polymer among macromolecular materials. In this project, we took advantage of thermoplastic polyurethane (TPU) resin, which possesses good compatibility with POM, serving as an encapsulation layer, and the carrier resin of the nitrogen-phosphorus composite flame retardant melamine phosphate to

Yuan Liu; MeiFang Liu; Daiyi Xie; Qi Wang

2008-01-01

92

Advanced Polymer Components. Volume 1.  

National Technical Information Service (NTIS)

The Advanced Polymer Components initiative began in December 1989. The initial purpose of the program was to explore advanced engineering polymers for use as rocket propulsion components. As research progressed it became apparent that advanced thermoplast...

J. Rusek

1995-01-01

93

Advanced Polymer Components. Volume 2.  

National Technical Information Service (NTIS)

The Advanced Polymer Components Initiative began in December l989. The initial purpose of the program was to explore advanced engineering polymers for use as rocket propulsion components. As research progressed it became apparent that advanced thermoplast...

J. Rusek

1995-01-01

94

Fabrication of the Thermoplastic Microfluidic Channels  

PubMed Central

In our lab, we have successfully isolated nucleic acids directly from microliter and submicroliter volumes of human blood, urine and stool using polymer/nanoparticle composite microscale lysis and solid phase extraction columns. The recovered samples are concentrated, small volume samples that are PCRable, without any additional cleanup. Here, we demonstrate how to fabricate thermoplastic microfluidic chips using hot embossing and heat sealing. Then, we demonstrate how to use in situ light directed surface grafting and polymerization through the sealed chip to form the composite solid phase columns. We demonstrate grafting and polymerization of a carbon nanotube/polymer composite column for bacterial cell lysis. We then show the lysis process followed by solid phase extraction of nucleic acids from the sample on chip using a silica/polymer composite column. The attached protocols contain detailed instructions on how to make both lysis and solid phase extraction columns.

Bhattacharyya, Arpita; Kulinski, Dominika; Klapperich, Catherine

2008-01-01

95

Thermoplastic composite matrices with improved solvent resistance  

NASA Technical Reports Server (NTRS)

In order to improve solvent resistance of aromatic thermoplastic polymers, ethynyl-terminated aromatic sulfone polymers (ETS), sulfone/ester polymers (SEPE) containing pendent ethynyl groups, and phenoxy resin containing pendent ethynyl groups are synthesized. Cured polysulfones and phenoxy resins containing ethynyl groups on the ends or pendent on the molecules exhibited systematic behavior in solvent resistance, film flexibility, and toughness as a function of crosslink density. The film and composite properties of a cured solvent-resistant ETS were better than those of a commercially available solvent sensitive polysulfone. The study was part of a NASA program to better understand the trade-offs between solvent resistance, processability and mechanical properties which may be useful in designing composite structures for aerospace vehicles.

Hergenrother, P. M.; Jensen, B. J.; Havens, S. J.

1984-01-01

96

Synthesis of thermoplastic polyurethane nanocomposites of reactive nanoclay by bulk polymerization methods  

Microsoft Academic Search

This paper reports synthesis and characterization of thermoplastic polyurethane nanocomposites of reactive silicate clays. Pre-polymer (method I) and chain-extended polymer molecules (method II) with residual –NCO groups participated in tethering reactions with clay during clay–polymer mixing. It was found that both clay–polymer reactions and shear stress of mixing are responsible for clay exfoliation. In method I, more clay-tethered polymer chains

Asim Pattanayak; Sadhan C. Jana

2005-01-01

97

Thermoplastic polyurethane toughened polyacetal blends  

Microsoft Academic Search

Polyacetal\\/thermoplastic polyurethane blends at four different polyacetal wt% of 90, 80, 70 and 60 were made using a twin screw extruder. Mechanical, morphological and rheological properties of these blends were determined. The addition of thermoplastic polyurethane (TPU) to polyacetal produces a decrease of tensile and flexural strength of the blend material as the TPU wt% increases. The notched impact strength

K Palanivelu; S Balakrishnan; P Rengasamy

2000-01-01

98

Thermoplastic film prevents proppant flowback  

Microsoft Academic Search

Thermoplastic film added to proppants is effective and economical for preventing proppant flowback after an hydraulic fracturing treatment. Most other methods, such as resin-coated proppant and fiber, for controlling proppant flowback have drawbacks that added to treatment costs by requiring long downtime, costly additives, or frequent equipment replacement. Thermoplastic film does not react chemically with fracturing fluids. After the proppant

P. D. Nguyen; J. D. Weaver; M. A. Parker; D. G. King

1996-01-01

99

The crystallization of tough thermoplastic resins in the presence of carbon fibers  

NASA Technical Reports Server (NTRS)

The crystallization kinetics of the thermoplastic resins poly(phenylene sulfide) (PPS) and poly(aryl-ether-ether-ketone) (PEEK) in the presence and in the abscence of carbon fibers was studied. How carbon fiber surfaces in composites affect the crystallization of tough thermoplastic polymers that may serve as matrix resins were determined. The crystallization kinetics of such substances can provide useful information about the crystallization mechanisms and, thus, indicate if the presence of carbon fibers cause any changes in such mechanisms.

Theil, M. H.

1986-01-01

100

Kinetics of adhesive contact formation between thermoplastic melts and solid surfaces: Effect on bond strength  

Microsoft Academic Search

Formation of an adhesive contact between a polymer melt (or solution) and reinforcing fibers is considered from the viewpoint of kinetics. A two-stage model of this process has been proposed, and an expression for the interfacial bond strength as a function of time and temperature is derived. Experimental data on bond strength in adhesive joints between thermoplastic polymers and reinforcing

E. Pisanova; S. Zhandarov; K. Schneider

1999-01-01

101

Graphite Fiber Reinforced Thermoplastic Resins.  

National Technical Information Service (NTIS)

This report describes the results of a program designed to optimize the fabrication procedures for graphite/thermoplastic composites, measure the properties of the composites as a function of temperature and finally, to fabricate and test graphite/thermop...

R. C. Novak K. Bowles

1977-01-01

102

Epoxy Thermoplastic Traffic Marking Material.  

National Technical Information Service (NTIS)

This Implementation Package summarizes the result of an effort to develop a more durable traffic marking material-Epoxy Thermoplastic (ETP). The report includes background information on the development of ETP, a discussion of the field tests and evaluati...

C. W. Niessner

1982-01-01

103

Graphite Fiber Reinforced Thermoplastic Resins.  

National Technical Information Service (NTIS)

Mechanical properties of neat resin samples and graphite fiber reinforced samples of thermoplastic resins were characterized with particular emphasis directed to the effects of environmental exposure (humidity, temperature and ultraviolet radiation). Tens...

R. C. Novak

1975-01-01

104

Synthesis and characterization of thermoplastic polyphenoxyquinoxalines  

NASA Astrophysics Data System (ADS)

This research was divided into two main parts. In the first part, a new facile route to relatively inexpensive thermoplastic polyphenoxyquinoxalines was developed. The synthetic route involves the aromatic nucleophilic substitution reaction of bisphenols with 2,3-dichloroquinoxaline. The dichloro monomer was prepared in two steps. In the first step, oxalic acid was condensed with o-phenylenediamine to give 2,3-dihydroxyquinoxaline. In the second step, 2,3-dihydroxyquinoxaline was treated with thionyl chloride to give 2,3-dichloroquinoxaline. This monomer was successfully polymerized with bisphenol-A, bisphenol-S, hexafluorobisphenol-A and 9,9-bis(4-hydroxyphenyl)fluorenone. Hydroquinone and biphenol, however, can not be polymerized to high molecular weight polymers because of the premature precipitation of crystalline oligomers. The glass transition temperatures of the high molecular weight polymers prepared from a series of bisphenols range from 191 °C to 279 °C, and their thermal decomposition temperatures are around 500 °C. The polymers are soluble in a wide range of solvents and can be solution-cast into thin films that are colorless and transparent. The polymers have tensile strengths ranging from 61 to 107 MPa, and tensile moduli ranging from 3.5 to 2.3 GPa. The synthesis of polymer obtained from 2,3-dichloroquinoxaline and bisphenol-A was scaled up to afford 500 g of material. This polymer is a thermoplastic with a melt-viscosity less than 1000 Pa.s. at 300 °C. The notched Izod impact strength of injection-molded samples of this polymer is 40.7 J/m. In the second part of this research, the synthetic method has been modified to allow the preparation of quinoxaline containing polyimides. Thus, 2,3-dichloroquinoxaline was treated either with p-nitrophenol followed by reduction of nitro groups, or with p-aminophenols to directly obtain the desired 2,3-(4-aminophenoxy)quinoxaline. This diamine was polymerized with 3,3',4,4'-biphenyldianhydride, 4,4'-oxydiphthalic anhydride and 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride. The polymerizations were carried out by the two step method. The poly(amic acid) intermediates were thermally imidized. Although they have high molecular weights judged by their inherent viscosities ranging from 0.51 to 1.01, thin films of all these polyimides were brittle. The glass transition temperatures of the polyimides range from 259 °C to 282 °C with thermal decomposition temperatures around 550 °C. The polyimide obtained from 2,3-(4-aminophenoxy)quinoxaline and 3,3',4,4'-biphenyldianhydride was found to be semi-crystalline.

Erdem, Haci Bayram

105

Azobenzene-Containing Thermoplastic Elastomers: Coupling Mechanical and Optical Effects  

Microsoft Academic Search

Thermoplastic elastomers of a styrene-butadiene-styrene (SBS) triblock copolymer containing grafts of an azobenzene side-chain liquid crystalline polymer were prepared by polymerization of an azobenzene acrylate monomer in solutions with dissolved SBS. Stretching thin films at room temperature induces long-range orientation of the azobenzene mesogenic groups along the strain direction. Upon irradiation with polarized or unpolarized UV light at 360 nm,

Shuying Bai; Yue Zhao

2001-01-01

106

Interfacial stress transfer in an aramid reinforced thermoplastic elastomer  

Microsoft Academic Search

The interfacial micromechanics of Twaron 2200 aramid fibers in an engineering thermoplastic elastomer (Pebax 7033, polyether\\u000a amide block co-polymer) has been investigated by determining the distribution of interfacial shear stress along fibers in\\u000a single-fiber model composites using Raman spectroscopy. The effects of various fiber surface treatments on the interfacial\\u000a shear stress and fragmentation of the aramid fibers are discussed. The

A. B. Coffey; C. M. O’Bradaigh; R. J. Young

2007-01-01

107

Low temperature properties of engineering thermoplastics  

SciTech Connect

There are currently a wide variety of engineering thermoplastics available for a multitude of applications. Because of present market requirements, there has been a limited demand for test results of the physical properties of these materials at low temperatures. Several potential applications exist, however, and as a result, several engineering thermoplastic samples were tested at {minus}40 and {minus}56.6{degrees}C. Although not all these tests followed the procedures specified by the American Society of Testing and Materials precisely, the data represent comparative data that can be utilized for further design efforts. The evaluations included tensile testing, compressive properties, and Izod impact testing. Several materials with varied glass loadings were studied to determine the low temperature tendencies these molding compounds would exhibit. Some of the resins examined were: polyetheretherketone (PEEK), polytherimide (PEI), polyphenylene sulfide (PPS), polyethersulfone (PES), polyphthlamide (PPA), and a liquid crystal polymer (Vectra A130). In all cases, no detrimental effect was discerned over this temperature range; the study also indicated that improvements in the physical properties could be expected.

Kaye, C.J.

1991-01-01

108

Review of methods for fusion bonding thermoplastic composites  

SciTech Connect

Bonding of thermoplastic composites is a critical step in the manufacture of aerospace structures. The objective of this project is to investigate different methods for fusion bonding thermoplastic composites quickly, with a good bond strength, and without warping and deconsolidation. This is best accomplished by heating and melting the thermoplastic on the bond surface only, and then pressing the parts together for a fusion bond. For this purpose, a variety of surface heating techniques were examined for bonding of PEEK and J Polymer composites. These included: resistance heating, infrared heating, induction heating, dielectric/microwave heating, and ultrasonic welding. In resistance heating, a single prepreg ply was placed between the composites and heated by passing electric current through the graphite fibers. With induction heating, a single ply of nickel coated graphite fibers was placed between the composites and heated. Ultrasonic welding was done by molding thermoplastic-only energy directors into the composites; the ultrasonic vibration melted these energy directors thereby fusion bonding the parts. 20 references.

Benatar, A.; Gutowski, T.G.

1987-02-01

109

Graft polymerization of native chicken feathers for thermoplastic applications.  

PubMed

Inexpensive and biodegradable thermoplastics were developed through graft polymerization of native chicken feather with methyl acrylate as a potential substitute for petroleum products. Poultry feathers are available in large quantities at a low price. However, natural chicken feathers have poor thermoplasticity, cannot be used to develop thermoplastic products, have very limited industrial applications, and are often considered as solid wastes. In this research, the effects of graft polymerization conditions, such as molar ratio of NaHSO(3) to K(2)S(2)O(8), initiator and monomer concentrations, pH, temperature and time of polymerization, on grafting parameters, that is, the conversion of monomer to polymer, grafting percentage, and grafting efficiency were evaluated. Methyl acrylate was found to be successfully grafted onto functional groups on the surfaces of the chicken feathers, and optimal graft polymerization conditions were also obtained. The feather-g-poly(methyl acrylate) developed showed good thermoplasticity, and feather films had substantially higher tensile properties than soy protein isolate and starch acetate films. PMID:21302951

Jin, Enqi; Reddy, Narendra; Zhu, Zhifeng; Yang, Yiqi

2011-03-01

110

Characterization of thermoplastic polyimide NEW-TPI  

NASA Technical Reports Server (NTRS)

Thermal and rheological properties of a commercial thermoplastic polyimide, NEW-TPI, were characterized. The as-received material possesses initially a transient crystallite form with a bimodal distribution in peak melting temperatures. After the meltings of the initial crystallite structures, the sample can be recrystallized by various thermal treatments. A bimodal or single-modal melting peak distribution is formed for annealing temperatures below or above 360 C, respectively. The recrystallized crystallinities are all transient in nature. The polymers are unable to be recrystallized after being subjected to elevated temperature annealing above 450 C. The recrystallization mechanism was postulated, and a simple kinetics model was found to describe the behavior satisfactorily under conditions of prolonged thermal annealing.

Hou, T. H.; Reddy, R. M.

1991-01-01

111

Thermoplastic polyimide NEW-TPI (trademark)  

NASA Technical Reports Server (NTRS)

Thermal and rheological properties of a commercial thermoplastic polyimide, NEW-TPI (trademark), were characterized. The as-received material possesses initially a transient crystallite form with a bimodal distribution in peak melting temperatures. After the melting of the initial crystallite structure, the sample can be recrystallized by various thermal treatments. A bimodal or single modal melting peak distribution is formed for annealing temperatures below or above 360 C, respectively. The recrystallized crystallinities are all transient in nature. The polymers are unable to be recrystallized after being subjected to elevated temperature annealing above 450 C. The recrystallization mechanism was postulated, and a simple kinetics model was found to describe the behavior rather satisfactory under the conditions of prolonged thermal annealing. Rheological measurements made in the linear viscoelastic range support the evidence observed in the thermal analysis. Furthermore, the measurements sustain the manufacturer's recommended processing window of 400 to 420 C for this material.

Hou, Tan-Hung; Reddy, Rakasi M.

1990-01-01

112

Thermoplastic Ribbon-Ply Bonding Model  

NASA Technical Reports Server (NTRS)

The aim of the present work was to identify key variables in rapid weldbonding of thermoplastic tow (ribbon) and their relationship to matrix polymer properties and to ribbon microstructure. Theoretical models for viscosity, establishment of ply-ply contact, instantaneous (Velcro) bonding, molecular interdiffusion (healing), void growth suppression, and gap filling were reviewed and synthesized. Consideration of the theoretical bonding mechanisms and length scales and of the experimental weld/peel data allow the prediction of such quantities as the time and pressure required to achieve good contact between a ribbon and a flat substrate, the time dependence of bond strength, pressures needed to prevent void growth from dissolved moisture and conditions for filling gaps and smoothing overlaps.

Hinkley, Jeffrey A.; Marchello, Joseph M.; Messier, Bernadette C.

1996-01-01

113

A review of recent developments in joining high-performance thermoplastic composites  

NASA Astrophysics Data System (ADS)

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.

Cole, K. C.

1991-06-01

114

Thermoplastic tape compaction device  

DOEpatents

A device is disclosed for bonding a thermoplastic tape to a substrate to form a fully consolidated composite. This device has an endless chain associated with a frame so as to rotate in a plane that is perpendicular to a long dimension of the tape, the chain having pivotally connected chain links with each of the links carrying a flexible foot member that extends outwardly from the chain. A selected number of the foot members contact the tape, after the heating thereof, to cause the heated tape to bond to the substrate. The foot members are each a thin band of metal oriented transversely to the chain, with a flexibility and width and length to contact the tape so as to cause the tape to conform to the substrate to achieve consolidation of the tape and the substrate. A biased leaf-type spring within the frame bears against an inner surface of the chain to provide the compliant pressure necessary to bond the tape to the substrate. The chain is supported by sprockets on shafts rotatably supported in the frame and, in one embodiment, one of the shafts has a drive unit to produce rotation such that the foot members in contact with the tape move at the same speed as the tape. Cooling jets are positioned along the frame to cool the resultant consolidated composite. 5 figures.

Campbell, V.W.

1994-12-27

115

Thermoplastic tape compaction device  

DOEpatents

A device for bonding a thermoplastic tape to a substrate to form a fully consolidated composite. This device has an endless chain associated with a frame so as to rotate in a plane that is perpendicular to a long dimension of the tape, the chain having pivotally connected chain links with each of the links carrying a flexible foot member that extends outwardly from the chain. A selected number of the foot members contact the tape, after the heating thereof, to cause the heated tape to bond to the substrate. The foot members are each a thin band of metal oriented transversely to the chain, with a flexibility and width and length to contact the tape so as to cause the tape to conform to the substrate to achieve consolidation of the tape and the substrate. A biased leaf-type spring within the frame bears against an inner surface of the chain to provide the compliant pressure necessary to bond the tape to the substrate. The chain is supported by sprockets on shafts rotatably supported in the frame and, in one embodiment, one of the shafts has a drive unit to produce rotation such that the foot members in contact with the tape move at the same speed as the tape. Cooling jets are positioned along the frame to cool the resultant consolidated composite.

Campbell, Vincent W. (Oak Ridge, TN)

1994-01-01

116

Gelled composite electrolyte comprising thermoplastic polyurethane and poly(ethylene oxide) for lithium batteries  

Microsoft Academic Search

Composite polymer electrolyte films consisting of poly(ethylene glycol) based thermoplastic polyurethane blended with poly(ethylene oxide) (denoted as TPU(PEG)\\/PEO) incorporating LiClO4–PC have been prepared and their electrochemical properties were studied. The thermal analysis of the composite films were performed to demonstrate the miscibility of the polymer blend by using differential scanning calorimeter (DSC). TPU(PEG)\\/PEO based polymer electrolyte shows ionic conductivity of

Ten-Chin Wen; Wei-Chih Chen

2001-01-01

117

Graphite fiber reinforced thermoplastic resins  

NASA Technical Reports Server (NTRS)

The results of a program designed to optimize the fabrication procedures for graphite thermoplastic composites are described. The properties of the composites as a function of temperature were measured and graphite thermoplastic fan exit guide vanes were fabricated and tested. Three thermoplastics were included in the investigation: polysulfone, polyethersulfone, and polyarylsulfone. Type HMS graphite was used as the reinforcement. Bending fatigue tests of HMS graphite/polyethersulfone demonstrated a gradual shear failure mode which resulted in a loss of stiffness in the specimens. Preliminary curves were generated to show the loss in stiffness as a function of stress and number of cycles. Fan exit guide vanes of HMS graphite polyethersulfone were satisfactorily fabricated in the final phase of the program. These were found to have stiffness and better fatigue behavior than graphite epoxy vanes which were formerly bill of material.

Navak, R. C.

1977-01-01

118

Advanced thermoplastic resins, phase 1  

NASA Technical Reports Server (NTRS)

Eight thermoplastic polyimide resin systems were evaluated as composite matrix materials. Two resins were selected for more extensive mechanical testing and both were versions of LaRC-TPI (Langley Research Center - Thermoplastic Polyimide). One resin was made with LaRC-TPI and contained 2 weight percent of a di(amic acid) dopant as a melt flow aid. The second system was a 1:1 slurry of semicrystalline LaRC-TPI powder in a polyimidesulfone resin diglyme solution. The LaRC-TPI powder melts during processing and increases the melt flow of the resin. Testing included dynamic mechanical analysis, tension and compression testing, and compression-after-impact testing. The test results demonstrated that the LaRC-TPI resins have very good properties compared to other thermoplastics, and that they are promising matrix materials for advanced composite structures.

Hendricks, C. L.; Hill, S. G.; Falcone, A.; Gerken, N. T.

1991-01-01

119

Effects of thermoplastic resin content of anisotropic conductive films on the pressure cooker test reliability of anisotropic conductive film flip-chip assembly  

NASA Astrophysics Data System (ADS)

The flip-chip technology using anisotropic conductive films (ACFs) is gaining growing interest due to its technical advantages such as environmentally friendly, simpler, and lower cost processes. Electrical performances and reliability of ACF flip-chip assembly depend on thermomechanical properties of ACF polymer resins. In this paper, the changes in ACF resin morphology due to the phase separation of thermoplastics, and subsequent changes of physical and mechanical properties were investigated as a function of thermoplastic contents of ACF formulation. Furthermore, the pressure cooker test (PCT) reliability of ACF flip-chip assemblies with various thermoplastic contents was also investigated. As thermoplastic contents increased, coefficient of thermal expansion (CTE) of ACFs increased, and elastic modulus (E?) of ACFs decreased. In contrast, water absorption rate decreased as thermoplastic content increased. As a result, PCT reliability of ACF flip-chip assembly was improved adding up to 50 wt.% content of thermoplastic.

Hwang, J. W.; Yim, M. J.; Paik, K. W.

2005-11-01

120

Structure and thermoplasticity of coal  

SciTech Connect

Chapters cover: molecular structure and thermoplastic properties of coal; {sup 1}H-nmr study of relaxation mechanisms of coal aggregate; structural changes of coal macromolecules during softening; quantitative estimation of metaplsat in heat-treated coal by solvent extraction; effects of surface oxidation on thermoplastic properties of coal; analysis of dilatation and contraction of coal during carbonization; formation mechanisms of coke texture during resolidification; modified CPD model for coal devolatilization; mathematical modelling of coke mechanical structure; and simulating particulate dynamics in the carbonization process based on discrete element treatment.

Komaki, I.; Itagaki, S.; Miura, T. (eds.)

2004-07-01

121

SULFUR POLYMER ENCAPSULATION  

Microsoft Academic Search

Sulfur polymer cement (SPC) is a thermoplastic polymer consisting of 95 wt% elemental sulfur and 5 wt% organic modifiers to enhance long-term durability. SPC was originally developed by the U.S. Bureau of Mines as an alternative to hydraulic cement for construction applications. Previous attempts to use elemental sulfur as a construction material in the chemical industry failed due to premature

2001-01-01

122

Semi-Interpenetrating Polymer Network's of Polyimides: Fracture Toughness (Abstract Only).  

National Technical Information Service (NTIS)

The objective was to improve the fracture toughness of the PMR-15 thermosetting polyimide by co-dissolving LaRC-TPI, a thermoplastic polyimide. The co-solvation of a thermoplastic into a thermoset produces an interpenetration of the thermoplastic polymer ...

M. G. Hansen

1988-01-01

123

Process for Preparing a Tough, Soluble, Aromatic, Thermoplastic Copolyimide  

NASA Technical Reports Server (NTRS)

A process for preparing a tough, soluble, aromatic, thermoplastic copolyimide is provided. The process comprises the steps of (a) providing 4.4'-oxydiphthalic anhydride to 3,4,3',4'-biphenyltetracarboxylic dianhydride at a mole ratio ranging from about 25 mole percent to 75 mole percent to 75 mole percent to about 25 mole percent; (b) adding 3,4'-oxydianiline to form a mixture; (c) adding a polar aprotic or polar protic solvent to the mixture to form a solution having a percentage of solids capable of maintaining polymer solubility; (d) stirring the solution to allow it to react; (e) adding an azeotropic solvent to the solution and heating to remove water; (f) cooling the solution of step (e) to room temperature and recovering the tough, soluble, aromatic, thermoplastic copolyimide.

Bryant, Robert G. (Inventor)

1997-01-01

124

Reinforcing of thermoplastic polycarbonate and polysulfone with carbon fibers: Production and characteristics of UD-compound objects  

NASA Technical Reports Server (NTRS)

The production and characteristics of the carbon fiber reinforced thermoplastics polycarbonate and polysulfone are described. The production of prepregs from defined polymer solutions is emphasized along with methods of optimizing the production of compounds. The characteristics of unidirectionally reinforced thermoplastics, such as shear strength, bending strength, and impact resistance are compared with regard to fracture behavior, the influence of intermediate layers, and the behavior under cryogenic conditions and under slightly elevated temperatures. The problem of adhesion between high strength carbon fibers and thermoplastics is examined, taking into account the effect of moisture on the shear strength and the impact resistance.

Fitzer, E.; Jaeger, H.

1988-01-01

125

Fully integrated single-walled carbon nanotube thermoplastic composites  

NASA Astrophysics Data System (ADS)

The development of composites of single-walled carbon nanotubes (SWNTs) with thermoplastics requires methods for good dispersion and achieving good interaction between SWNTs and the matrix. This thesis presents a new method to achieve good dispersion by a preliminary treatment called incipient wetting. The SWNTs dispersed in a solvent are mixed with polymer particles and deposited over them as the solvent is evaporated to give an initial dispersion. Factors that make this more effective are: good wetting of the polymer by the solvent, swelling of the polymer, high surface area of the polymer. Swelling enhances the initial dispersion with some initial mixing. A high surface area is achieved using polymer powder. High shear mixing alone does not achieve the same uniform and repeatable level of dispersion that the combination with incipient wetting allows. The incipient wetting method was studied and applied to different polymers. The possibility of recovering SWNTs from thermoplastics by dissolving or burning away the matrix is an extension of this study. A new comprehensive approach to control the interface of thermoplastics with SWNTs is studied. This is based on achieving direct chemical bonding between polymer molecules and functional groups on oxidized open ends, sidewalls, or both, in the SWNTs. Different concepts and approaches to these "fully integrated nanotube composites" are discussed. The concepts have been applied to epoxies elsewhere and are tested here with nylon-6,6 as a model system. Nylon was synthesized by interfacial polymerization in the presence of SWNTs resulting in excellent dispersion in the composite without further processing. The essential requirement for good dispersion is that the SWNTs are well dispersed in the solvent. Interfacial polymerization opens the way to many types of polymer-SWNT composites. Tests of full integration of SWNTs with open ended nanotubes showed promising results and hints of integration but were limited by dispersion in the solvent. Fluorinated SWNTs were dispersed effectively with dichlorobenzene, another solvent may be better. There is no conclusive evidence of integration with F-SWNTs but they may react with the polymer chain with thermal post-processing.

Rodriguez-Macias, Fernando J.

126

A review of recent developments in joining high-performance thermoplastic composites  

Microsoft Academic Search

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

K. C. Cole

1991-01-01

127

Rapid, controllable and environmentally benign fabrication of thermoplastic nanofibers and applications  

Microsoft Academic Search

In situ fibrillar and lamellar hybrid morphology was found in various immiscible polymer blends prepared by melt ram extrusion of cellulose acetate butyrate (CAB)\\/Thermoplastics at a weight ratio of 80 to 20. The formation process was analyzed and proposed. The presence of the elongational flow field determines the formation of the fibrils, and the improvement of the mixing efficiency can

Dong Wang

2008-01-01

128

Finite Element Assisted Modelling of the Microscopic Impregnation Process in Thermoplastic Preforms  

Microsoft Academic Search

Fibre reinforced composite materials incorporating thermoplastic matrices are gaining increasing popularity in many industrial applications. One of the potential preforms for the manufacture of technical components is commingled yarn composed of reinforcement and matrix in fibre form. These are often employed in the pultrusion process. Another innovative preform consists of polymer powder preimpregnated sheath surrounding fibre bundles. To achieve adequate

S. M. Haffner; K. Friedrich; P. J. Hogg; J. J. C. Busfield

1998-01-01

129

Toughness properties and service performance of high temperature thermoplastics and their composites  

SciTech Connect

Correlations were made between the fracture toughness of a series of high temperature thermoplastics and the service performance of their composite counterparts. These Du Pont resin systems include polyimide based K-II, K-III, and N polymers, as well as polyamide based J-1 and J-2 polymers. The investigation covered a wide range of resin toughness values for the K-polymer family. The good toughness characteristics of these thermoplastic resins, represented by their high mode I plane-strain fracture toughness, is directly translated into the mode I interlaminar fracture toughness of their respective composite laminates. Improvement of the residual-compressive-strength after impact of the K-polymer based composites is achieved by increasing the neat-resin fracture toughness. 12 references.

Wedgewood, A.R.; Su, K.B.; Narin, J.A.

1988-02-01

130

Valveless diffuser micropumps fabricated using thermoplastic replication  

Microsoft Academic Search

This paper presents valve-less diffuser micropumps fabricated using thermoplastic replication. Thermoplastic replication is very suitable for a valve-less diffuser pump due to its simple planar geometry. Two different thermoplastic replication methods have been tested: hot embossing and injection molding. We use 0.1 and 0.2 mm deep precision-milled brass mold inserts and 20 and 80 ?m deep microelectroformed nickel mold inserts

Anders Olsson; Olle Larsson; Johan Holm; Lars Lundbladh; Ove Öhman; Göran Stemme

1998-01-01

131

Multiphase design of autonomic self-healing thermoplastic elastomers  

NASA Astrophysics Data System (ADS)

The development of polymers that can spontaneously repair themselves after mechanical damage would significantly improve the safety, lifetime, energy efficiency and environmental impact of man-made materials. Most approaches to self-healing materials require the input of external energy, healing agents, solvent or plasticizer. Despite intense research in this area, the synthesis of a stiff material with intrinsic self-healing ability remains a key challenge. Here, we show a design of multiphase supramolecular thermoplastic elastomers that combine high modulus and toughness with spontaneous healing capability. The designed hydrogen-bonding brush polymers self-assemble into a hard-soft microphase-separated system, combining the enhanced stiffness and toughness of nanocomposites with the self-healing capability of dynamic supramolecular assemblies. In contrast to previous self-healing polymers, this new system spontaneously self-heals as a single-component solid material at ambient conditions, without the need for any external stimulus, healing agent, plasticizer or solvent.

Chen, Yulin; Kushner, Aaron M.; Williams, Gregory A.; Guan, Zhibin

2012-06-01

132

Tough, Soluble, Aromatic, Thermoplastic Copolyimides  

NASA Technical Reports Server (NTRS)

Tough, soluble, aromatic, thermoplastic copolyimides were prepared by reacting 4,4'-oxydiphthalic anhydride, 3,4,3',4'-biphenyltetracarboxylic dianhydride and 3,4'-oxydianiline. These copolyimides were found to be soluble in common amide solvents such as N,N'-dimethyl acetamide, N-methylpyrrolidinone, and dimethylformamide allowing them to be applied as the fully imidized copolymer and to be used to prepare a wide range of articles.

Bryant, Robert G. (Inventor)

1998-01-01

133

Final Report: Interphase Analysis and Control in Fiber Reinforced Thermoplastic Composites  

SciTech Connect

This research program builds upon a multi-disciplinary effort in interphase analysis and control in thermoplastic matrix polymer matrix composites (PMC). The research investigates model systems deemed of interest by members of the Automotive Composites Consortium (ACC) as well as samples at the forefront of PMC process development (DRIFT and P4 technologies). Finally, the research investigates, based upon the fundamental understanding of the interphases created during the fabrication of thermoplastic PMCs, the role the interphase play in key bulk properties of interest to the automotive industry.

Jon J. Kellar; William M. Cross; Lidvin Kjerengtroen

2009-03-14

134

Mesoporous carbon nanofibers with a high surface area electrospun from thermoplastic polyvinylpyrrolidone  

NASA Astrophysics Data System (ADS)

Carbon nanofibers (CNFs) have been synthesized from thermoplastic polyvinylpyrrolidone (PVP) using electrospinning in combination with a novel three-step heat treatment process, which successfully stabilizes the fibrous morphology before carbonization that was proven to be difficult for thermoplastic polymers other than polyacrylonitrile (PAN). These CNFs are both mesoporous and microporous with high surface areas without subsequent activation, and thus overcome the limitations of PAN based CNFs, and are processed in an environmentally friendly and more cost effective manner. The effects of heat treatment parameters and precursor concentration on the morphologies and porous properties of CNFs have been investigated, and their application as anodes for lithium ion batteries has also been demonstrated.

Wang, Peiqi; Zhang, Dan; Ma, Feiyue; Ou, Yun; Chen, Qian Nataly; Xie, Shuhong; Li, Jiangyu

2012-10-01

135

Determination of adhesion between thermoplastic and liquid silicone rubbers in hard-soft-combinations via mechanical peeling test  

NASA Astrophysics Data System (ADS)

The production of hard-soft-combinations via multi injection molding gained more and more importance in the last years. This is attributed to different factors. One principle reason is that the use of two-component injection molding technique has many advantages such as cancelling subsequent and complex steps and shortening the process chain. Furthermore this technique allows the combination of the properties of the single components like the high stiffness of the hard component and the elastic properties of the soft component. Because of the incompatibility of some polymers the adhesion on the interface has to be determined. Thereby adhesion is not only influenced by the applied polymers, but also by the injection molding parameters and the characteristics of the mold. Besides already known combinations of thermoplastics with thermoplastic elastomers (TPE), there consists the possibility to apply liquid silicone rubber (LSR) as soft component. A thermoplastic/LSR combination gains in importance due to the specific advantages of LSR to TPE. The faintly adhesion between LSR and thermoplastics is currently one of the key challenges when dealing with those combinations. So it is coercively necessary to improve adhesion between the two components by adding an adhesion promoter. To determine the promoters influence, it is necessary to develop a suitable testing method to investigate e.g. the peel resistance. The current German standard "VDI Richtlinie 2019', which is actually only employed for thermoplastic/TPE combinations, can serve as a model to determine the adhesion of thermoplastic/LSR combinations.

Kühr, C.; Spörrer, A.; Altstädt, V.

2014-05-01

136

Method and apparatus for extruding thermoplastic material  

Microsoft Academic Search

A gear pump assisted screw conveyor extrusion system utilizing a cartridge heating device disposed axially within the screw and having the drives for the gear pump and the screw correlated in speed to create relatively little pressure in the thermoplastic material being extruded such that relatively little mechanical working thereof occurs. The thermoplastic material is melted in the screw conveyor

McKelvey

1985-01-01

137

Thermoplastic joining using solar energy concentrator  

Microsoft Academic Search

The harnessing of solar energy for processing thermoplastics using a solar concentrator is detailed. The application of this relatively new method is driven by manufacturing industry demands for simpler production methods and increased productivity when processing plastics and the need to achieve these goals in an enviromentally friendly way. This work investigates the feasibility of effectively joining thermoplastics such as

E. Siores

1997-01-01

138

Development of ecofriendly thermoplastics for automotive components  

Microsoft Academic Search

Use of natural fiber thermoplastic components in the automotive industry can provide the advantages of weight reduction, cost reduction and recyclability, in addition to eco-efficiency and renewability compared to synthetic conventional materials. Natural fibers have recently become attractive to automotive industry as an alternative reinforcement for glass fiber reinforced thermoplastics. The best way to increase the fuel efficiency with out

S. Jeyanthi; M. Purushothaman; J. Janci Rani

2011-01-01

139

Improved construction materials for polar regions using microcellular thermoplastic foams  

NASA Technical Reports Server (NTRS)

Microcellular polymer foams (MCF) are thermoplastic foams with very small cell diameters, less than 10 microns, and very large cell densities, 10(exp 9) to 10(exp 15) cells per cubic centimeter of unfoamed material. The concept of foaming polymers with microcellular voids was conceived to reduce the amount of material used for mass-produced items without compromising the mechanical properties. The reasoning behind this concept was that if voids smaller than the critical flaw size pre-existing in polymers were introduced into the matrix, they would not affect the overall strength of the product. MCF polycarbonate (PC), polystyrene (PS), and polyvinyl chloride (PVC) were examined to determine the effects of the microstructure towards the mechanical properties of the materials at room and arctic temperatures. Batch process parameters were discovered for these materials and foamed samples of three densities were produced for each material. To quantify the toughness and strength of these polymers, the tensile yield strength, tensile toughness, and impact resistance were measured at room and arctic temperatures. The feasibility of MCF polymers has been demonstrated by the consistent and repeatable MCF microstructures formed, but the improvements in the mechanical properties were not conclusive. Therefore the usefulness of the MCF polymers to replace other materials in arctic environments is questionable.

Cunningham, Daniel J.

1994-01-01

140

Polymers.  

ERIC Educational Resources Information Center

Presents an open-ended experiment which has students exploring polymer chemistry and reverse osmosis. This activity involves construction of a polymer membrane, use of it in a simple osmosis experiment, and application of its principles in solving a science-technology-society problem. (ML)

Tucker, David C.

1986-01-01

141

Thermoplastic film prevents proppant flowback  

SciTech Connect

Thermoplastic film added to proppants is effective and economical for preventing proppant flowback after an hydraulic fracturing treatment. Most other methods, such as resin-coated proppant and fiber, for controlling proppant flowback have drawbacks that added to treatment costs by requiring long downtime, costly additives, or frequent equipment replacement. Thermoplastic film does not react chemically with fracturing fluids. After the proppant is placed in the fracture, the film strips intertwine with the proppant grains or at higher temperatures, the strips become adhesive and shrink forming consolidated clusters that hold open the newly created fractures and prevent proppant from flowing back. The low cost of the film means that the strips can be used throughout the fracturing job or in selected stages. The strips are compatible with fracturing fluid chemistry, including breakers and crosslinkers, and can be used in wells with a wide range of bottom hole temperatures. The end result is a well that can be brought back on-line in a short time with little proppant flowback. This paper reviews the cost benefits and performance of these proppants.

Nguyen, P.D.; Weaver, J.D.; Parker, M.A.; King, D.G. [Halliburton Energy Services, Duncan, OK (United States)

1996-02-05

142

Joining of thermoplastic substrates by microwaves  

DOEpatents

A method for joining two or more items having surfaces of thermoplastic material includes the steps of depositing an electrically-conductive material upon the thermoplastic surface of at least one of the items, and then placing the other of the two items adjacent the one item so that the deposited material is in intimate contact with the surfaces of both the one and the other items. The deposited material and the thermoplastic surfaces contacted thereby are then exposed to microwave radiation so that the thermoplastic surfaces in contact with the deposited material melt, and then pressure is applied to the two items so that the melted thermoplastic surfaces fuse to one another. Upon discontinuance of the exposure to the microwave energy, and after permitting the thermoplastic surfaces to cool from the melted condition, the two items are joined together by the fused thermoplastic surfaces. The deposited material has a thickness which is preferably no greater than a skin depth, .delta..sub.s, which is related to the frequency of the microwave radiation and characteristics of the deposited material in accordance with an equation.

Paulauskas, Felix L. (Oak Ridge, TN); Meek, Thomas T. (Knoxville, TN)

1997-01-01

143

Assessment of relative flammability and thermochemical properties of some thermoplastic materials  

NASA Technical Reports Server (NTRS)

Thermomechanical properties, flammability, oxygen index, relative toxicity of pyrolysis effluents, and char yields were studied for 12 advanced polymers which are candidates for use in aircraft interiors as decorative films, compression- and injection-molded parts and thermoplastic parts. Polymers sampled included polyphenylene sulfide, 9,9 bis (4-hydroxyphenol) fluorene polycarbonate-poly (dimethylsiloxane), polyether sulfone, polyvinyl fluoride and polyvinylidene fluoride. Availability of these samples, whether in commercial form or in test quantities, is specified. An estimate of relative fire resistance for the materials was obtained; the five polymers listed above were found to be the most fire resistant of the 12 sampled.

Kourtides, D. A.; Parker, J. A.

1977-01-01

144

Injectable bioactive glass/biodegradable polymer composite for bone and cartilage reconstruction: concept and experimental outcome with thermoplastic composites of poly(epsilon-caprolactone-co-D,L-lactide) and bioactive glass S53P4.  

PubMed

Injectable composites (Glepron) of particulate bioactive glass S53P4 (BAG) and Poly(epsilon-caprolactone-co-D,L-lactide) as thermoplastic carrier matrix were investigated as bone fillers in cancellous and cartilagineous subchondral bone defects in rabbits. Composites were injected as viscous liquid or mouldable paste. The glass granules of the composites resulted in good osteoconductivity and bone bonding that occurred initially at the interface between the glass and the host bone. The bone bioactivity index (BBI) indicating bone contacts between BAG and bone, as well as the bone coverage index (BCI) indicating bone ongrowth, correlated with the amount of glass in the composites. The indices were highest with 70 wt % of BAG, granule size 90-315 microm and did not improve by the addition of sucrose as in situ porosity creating agent in the composite or by using smaller (<45 microm) glass granules. The percentage of new bone ingrowth into the composite with 70 wt % of BAG was 6-8% at 23 weeks. At the articular surface cartilage regeneration with chondroblasts and mature chondrocytes was often evident. The composites were osteoconductive and easy to handle with short setting time. They were biocompatible with low foreign body cellular reaction. Results indicate a suitable working concept as a filler bone substitute for subchondral cancellous bone defects. PMID:15516880

Aho, Allan J; Tirri, Teemu; Kukkonen, Juha; Strandberg, Niko; Rich, Jaana; Seppälä, Jukka; Yli-Urpo, Antti

2004-10-01

145

Thermoplastic matrix composite processing model  

NASA Technical Reports Server (NTRS)

The effects the processing parameters pressure, temperature, and time have on the quality of continuous graphite fiber reinforced thermoplastic matrix composites were quantitatively accessed by defining the extent to which intimate contact and bond formation has occurred at successive ply interfaces. Two models are presented predicting the extents to which the ply interfaces have achieved intimate contact and cohesive strength. The models are based on experimental observation of compression molded laminates and neat resin conditions, respectively. Identified as the mechanism explaining the phenomenon by which the plies bond to themselves is the theory of autohesion (or self diffusion). Theoretical predictions from the Reptation Theory between autohesive strength and contact time are used to explain the effects of the processing parameters on the observed experimental strengths. The application of a time-temperature relationship for autohesive strength predictions is evaluated. A viscoelastic compression molding model of a tow was developed to explain the phenomenon by which the prepreg ply interfaces develop intimate contact.

Dara, P. H.; Loos, A. C.

1985-01-01

146

Tough soluble aromatic thermoplastic copolyimides  

NASA Technical Reports Server (NTRS)

Tough, soluble, aromatic, thermoplastic copolyimides were prepared by reacting 4,4'-oxydiphthalic anhydride, 3,4,3',4'-biphenyltetracarboxylic dianhydride and 3,4'-oxydianiline. Alternatively, these copolyimides may be prepared by reacting 4,4'-oxydiphthalic anhydride with 3,4,3',4'-biphenyltetracarboxylic dianhydride and 3,4'-oxydiisocyanate. Also, the copolyimide may be prepared by reacting the corresponding tetra acid and ester precursors of 4,4'-oxydiphthalic anhydride and 3,4,3',4'-biphenyltetracarboxylic dianhydride with 3,4'-oxydianiline. These copolyimides were found to be soluble in common amide solvents such as N,N'-dimethyl acetamide, N-methylpyrrolidinone, and dimethylformamide allowing them to be applied as the fully imidized copolymer and to be used to prepare a wide range of articles.

Bryant, Robert G. (Inventor)

2000-01-01

147

Sulfur Mustard Penetration of Thermoplastic Elastomers.  

National Technical Information Service (NTIS)

Resistance to sulfur mustard (HD) penetration was investigated for two commercially available thermoplastic elastomers, Santoprene and Alcryn. To pass the Liquid Agent Vapour Penetration Test (LAVPT), Santoprene sheet needed to be at least 1.03 mm thick w...

P. Miller

2008-01-01

148

Process for preparing thermoplastic aromatic polyimides  

NASA Technical Reports Server (NTRS)

A method of preparing insoluble thermoplastic aromatic polyimides is described, having uniquely low softening temperatures by reacting, in a suitable solvent, an aromatic dianhydride, and a meta-substituted aromatic diamine.

Bell, V. L. (inventor)

1978-01-01

149

Interlaminar fracture toughness of thermoplastic composites  

NASA Technical Reports Server (NTRS)

Edge delamination tension and double cantilever beam tests were used to characterize the interlaminar fracture toughness of continuous graphite-fiber composites made from experimental thermoplastic polyimides and a model thermoplastic. Residual thermal stresses, known to be significant in materials processed at high temperatures, were included in the edge delamination calculations. In the model thermoplastic system (polycarbonate matrix), surface properties of the graphite fiber were shown to be significant. Critical strain energy release rates for two different fibers having similar nominal tensile properties differed by 30 to 60 percent. The reason for the difference is not clear. Interlaminar toughness values for the thermoplastic polyimide composites (LARC-TPI and polyimidesulfone) were 3 to 4 in-lb/sq in. Scanning electron micrographs of the EDT fracture surfaces suggest poor fiber/matrix bonding. Residual thermal stresses account for up to 32 percent of the strain energy release in composites made from these high-temperature resins.

Hinkley, J. A.; Johnston, N. J.; Obrien, T. K.

1988-01-01

150

Interlaminar fracture toughness of thermoplastic composites  

NASA Technical Reports Server (NTRS)

Edge delamination tension and double cantilever beam tests were used to characterize the interlaminar fracture toughness of continuous graphite-fiber composites made from experimental thermoplastic polyimides and a model thermoplastic. Residual thermal stresses, known to be significant in materials processed at high temperatures, were included in the edge delamination calculations. In the model thermoplastic system (polycarbonate matrix), surface properties of the graphite fiber were shown to be significant. Cricital strain energy release rates for two different fibers having similar nominal tensile properties differed by 30 to 60 percent. The reason for the difference is not clear. Interlaminar toughness values for the thermoplastic polyimide composites (LARC-TPI and polyimidesulfone) were 3 to 4 in-lb/sq in. Scanning electron micrographs of the EDT fracture surfaces suggest poor fiber/matrix bonding. Residual thermal stresses account for up to 32 percent of the strain energy release in composites made from these high-temperature resins.

Hinkley, Jeffrey A.; Johnston, Norman J.; O'Brien, T. Kevin

1989-01-01

151

Voltage control for corona charging thermoplastics  

NASA Technical Reports Server (NTRS)

Controlled voltage is accomplished by placing metal plate with hole in it near surface of film. During charging, thermoplastic will accumulate charge only until it reaches plate voltage; after that, all charge will be deflected to plate.

Mezrich, R. S.

1976-01-01

152

Characterization of Polyetheretherketone and Other Engineering Thermoplastics.  

National Technical Information Service (NTIS)

Three engineering thermoplastic materials were characterized by thermal/spectroscopic means to assess their suitability in fiberglass-filled molding resins for Mound applications. The three resins examined were: polyetheretherketone (PEEK) from ICI, Ltd.,...

R. B. Whitaker A. B. Nease R. O. Yelton

1984-01-01

153

Thermoplastic Elastomers via Radical Polymerization. II.  

National Technical Information Service (NTIS)

Simple models are used to study the formation of thermoplastic elastomers using a method for preparation of block copolymers introduced by Tobolsky and Rembaum. It was found that a small excess of isocyanate groups produce branched block copolymers with s...

E. J. Zaganiaris

1970-01-01

154

Process for Preparing Thermoplastic Aromatic Polyimides.  

National Technical Information Service (NTIS)

A method of preparing insoluble thermoplastic aromatic polyimides is described, having uniquely low softening temperatures by reacting, in a suitable solvent, an aromatic dianhydride, and a meta-substituted aromatic diamine.

V. L. Bell

1978-01-01

155

Fly ash-reinforced thermoplastic starch composites  

Microsoft Academic Search

As a by-product from the combustion of pulverized coal, fly ash was, respectively, used as the reinforcement for formamide and urea-plasticized thermoplastic starch (FUPTPS) and glycerol-plasticized thermoplastic starch (GPTPS). The introduction of fly ash improved tensile stress from 4.56MPa to 7.78MPa and Youngs modulus increased trebly from 26.8MPa to 84.6MPa for fly ash-reinforced FUPTPS (A-FUPTPS), while tensile stress increased from

X. F. Ma; J. G. Yu; N. Wang

2007-01-01

156

Random and systematic error analysis in the complex permittivity measurements of high dielectric strength thermoplastics  

Microsoft Academic Search

This paper presents the complex dielectric permittivity and loss tangent measurements for a selection of advanced polymer-based thermoplastics in the Q-band, V-band and W-band frequencies and discusses in detail the random and systematic errors that arise in the experimental setup. These plastics are reported to have exceptional mechanical, thermal and electrical properties and are extensively used as electrical insulating materials,

Nahid Rahman; Ana I. Medina Ayala; Konstantin A. Korolev; Mohammed N. Afsar; Rudy Cheung; Maurice Aghion

2009-01-01

157

Estimation of Compounding Conditions and Grade Selections in the Preparation of Thermoplastic Melt Blends  

Microsoft Academic Search

Blending-or modification of one polymer with another-is proving to hold great promise in tailor-making materials to satisfy a variety of specific cost\\/ performance targets. A number of commercial blends are available in the mar- ket with balanced combinations of physical properties, processing characteris- tics, and cost. The engineering thermoplastics that have been commonly used as components for forming blends are

A. V. Shenoy

1985-01-01

158

Determination of metal additives and bromine in recycled thermoplasts from electronic waste by TXRF analysis  

Microsoft Academic Search

A new method for analysis of metal additives in recycled thermoplasts from electronic waste was developed, based on dissolving\\u000a the samples in an organic solvent and subsequent analysis of the corresponding solutions or suspensions by total-reflection\\u000a X-ray fluorescence spectroscopy (TXRF). The procedure proved to be considerably less time consuming than the conventional\\u000a digestion of the polymer matrix. Additives containing Ti,

H. Fink; U. Panne; M. Theisen; R. Niessner; T. Probst; X. Lin

2000-01-01

159

Investigations on laser transmission welding of absorber-free thermoplastics  

NASA Astrophysics Data System (ADS)

Within the plastic industry laser transmission welding ranks among the most important joining techniques and opens up new application areas continuously. So far, a big disadvantage of the process was the fact that the joining partners need different optical properties. Since thermoplastics are transparent for the radiation of conventional beam sources (800- 1100 nm) the absorbance of one of the joining partners has to be enhanced by adding an infrared absorber (IR-absorber). Until recently, welding of absorber-free parts has not been possible. New diode lasers provide a broad variety of wavelengths which allows exploiting intrinsic absorption bands of thermoplastics. The use of a proper wavelength in combination with special optics enables laser welding of two optically identical polymer parts without absorbers which can be utilized in a large number of applications primarily in the medical and food industry, where the use of absorbers usually entails costly and time-consuming authorization processes. In this paper some aspects of the process are considered as the influence of the focal position, which is crucial when both joining partners have equal optical properties. After a theoretical consideration, an evaluation is carried out based on welding trials with polycarbonate (PC). Further aspects such as gap bridging capability and the influence of thickness of the upper joining partner are investigated as well.

Mamuschkin, Viktor; Olowinsky, Alexander; Britten, Simon W.; Engelmann, Christoph

2014-03-01

160

Formation, Stability and Properties of Self-Reinforcing Polymer Blends.  

National Technical Information Service (NTIS)

Blending of thermoplastic polymer is, in principle, a flexible and cost effective way to generate new plastic materials, and to extend their applicability. Blending is used to modify, for example, the thermal, chemical, optical, mechanical or processing p...

A. G. C. Machiels

1998-01-01

161

Thermoplastic polyurethane (TPU)/polyolefin (PO) blends  

NASA Astrophysics Data System (ADS)

Thermoplastic polyurethane (TPU) is a very important material with high versatility and superior physical properties. Melt blending TPU with metallocene polyolefin (PO) can lower TPU cost and improve polyolefin properties like abrasion resistance, adhesion, and paintability. Since TPU and non-polar PO blends are completely immiscible, efficient compatibilizers become the key issue and remain challenging. My main thesis work is to develop and study compatibilized TPU/PO blends. Although reactive compatibilization is considered the most efficient method, fast interfacial reactions between highly reactive functional groups are necessary to generate compatibilizers within usually short processing time. It is known that the urethane linkage (carbamate -NHCOO-) in TPU can reversibly dissociate to generate highly reactive isocyanates at melt temperatures. To find out the best reactive compatibilization, three approaches were employed on different molecular scales: (1) model urethane compound (dibutyl & dioctyl 4,4'-methylenebis(phenyl carbamate)) and small functional molecule (primary amine, secondary amine, hydroxyl, acid, anhydride, and epoxide) reactions at 200°C monitored by nuclear magnetic resonance and Fourier-transform infrared to examine the basic chemistry; (2) short, model TPU's with different chemical structures blended with functional polymers including poly(ethylene glycol) and polybutadiene to explore the effect of interface in immiscible mixtures; (3) melt blending of a commercial TPU with polypropylene (PP), further involving more complicated morphology, using different types of functional PP's (note: amine functional PP's were prepared by melt amination) as compatibilizers followed by rheological, morphological, thermal, and mechanical characterizations. Besides the core thesis project on TPU blends, other related work that has been accomplished includes: (1) adhesion between TPU and PP; (2) rheological properties of TPU; (3) block copolymer formation by reactive coupling. In the first work, the unique interfacial reactions were applied to promote TPU-PP adhesion that was quantified by asymmetric double cantilever beam test. In the second study, the abnormally high flow activation energy of TPU was explained by simultaneously investigating the effect of temperature and thermal degradation on the melt viscosity. In the third project, block copolymers were prepared by rapid reactive coupling of amine and isocyanate functional polymers and the reaction kinetics were also studied.

Lu, Qiwei

162

Liants Modifies Par des Polymeres pour Enduits et Enrobes Speciaux (Polymer Modified Binders for Bituminous or Asphaltic Paving Layers).  

National Technical Information Service (NTIS)

The state of the art in polymer modified binders is reviewed. The survey includes theoretical aspects of hydrocarbon binder properties modification, the nature of the changes induced by thermoplastic polymer addition, special procedures (such as the addit...

B. Brule

1987-01-01

163

Melting behavior of typical thermoplastic materials--an experimental and chemical kinetics study.  

PubMed

A medium-scale melting experiment rig was designed and constructed in this study. A detailed experimental study was conducted on the melting behavior and the chemical kinetic characteristics of three typical thermoplastic materials, including polypropylene (PP), polyethylene (PE) and polystyrene (PS). It is observed that the thermal decomposition of the thermoplastic materials mainly consists of three stages: the initial heating stage, the melting-dominated stage and the gasification-dominated stage. Melting of the materials examined takes place within a certain temperature range. The melting temperature of PS is the lowest, moreover, it takes the shortest time to be completely liquefied. To quantitatively represent the chemical kinetics, an nth-order reaction model was employed to interpret the thermal decomposition behavior of the materials. The calculated reaction order is largely in accordance with the small-scale thermal gravimetric analysis (TGA). The small difference between the results and TGA data suggests that there are some limitations in the small-scale experiments in simulating the behavior of thermoplastic materials in a thermal hazard. Therefore, investigating the thermal physical and chemical properties of the thermoplastic materials and their thermal hazard prevention in medium or large-scale experiments is necessary for the fire safety considerations of polymer materials. PMID:24007994

Wang, Nan; Tu, Ran; Ma, Xin; Xie, Qiyuan; Jiang, Xi

2013-11-15

164

Extraction, characterization of components, and potential thermoplastic applications of camelina meal grafted with vinyl monomers.  

PubMed

Camelina meal contains oil, proteins, and carbohydrates that can be used to develop value-added bioproducts. In addition to containing valuable polymers, coproducts generated during the production of biofuels are inexpensive and renewable. Camelina is a preferred oilseed crop for biodiesel production because camelina is easier to grow and provides better yields. In this research, the components in camelina meal were extracted and studied for their composition, structure, and properties. The potential of using the camelina meal to develop thermoplastics was also studied by grafting various vinyl monomers. Oil (19%) extracted from camelina meal could be useful for food and fuel applications, and proteins and cellulose in camelina meal could be useful in the development of films, fibers, and thermoplastics. Thermoplastic films developed from grafted camelina meal had excellent wet tensile properties, unlike thermoplastics developed from other biopolymers. Camelina meal grafted with butylmethacrylate (BMA) had high dry and wet tensile strengths of 53.7 and 17.3 MPa, respectively. PMID:22540881

Reddy, Narendra; Jin, Enqi; Chen, Lihong; Jiang, Xue; Yang, Yiqi

2012-05-16

165

Thermoset-Thermoplastic Aromatic Polyamides.  

National Technical Information Service (NTIS)

A composition and method for increasing the use temperature of polyamides based on the incorporation of a latent crosslinking agent into the polymer backbone, wherein high temperature performance is achieved without sacrificing solubility or processabilit...

T. L. St.Clair J. F. Wolfe T. D. Greenwood

1980-01-01

166

Thermoplastic Elastomers via polyolefin/Layered Silicate Nanocomposites  

NASA Astrophysics Data System (ADS)

Here we report the synthesis of fully exfoliated polyolefin nanocomposites via Surface-Initiated Ring Opening Metathesis Polymerization (SI-ROMP). Montmorillonite (MMT) clay platelets were rendered hydrophobic through ion exchange with alkyl-ammonium surfactants terminated with norbornene. We were then able to form block copolymer brushes of (substituted) norbornenes and cyclopentene via SI-ROMP. Subsequent hydrogenation yielded highly crystalline polyethylene and rubbery saturated polynorbornenes, thus giving a thermoplastic elastomer. Nanocomposites were prepared with different nanofiller percentages and were characterized for morphological (XRD, TEM), thermal (TGA, DSC), and mechanical (DMA, Rheology) properties. Complete exfoliation of nanocomposites was confirmed by XRD and TEM. A fraction of the polymer brushes were subsequently removed from their substrate by reverse ion exchange and characterized in parallel with their corresponding nanocomposite analogs. In this way we were able to directly assess the role of the filler particle in the thermal properties, melt rheology, morphology, and tensile properties.

Harsha Kalluru, Sri; Cochran, Eric W.

2013-03-01

167

Preparation and characterization of thermoplastic materials for invisible orthodontics.  

PubMed

PETG/PC/TPU polymer blend was prepared by mechanical blending. The mechanical properties of modified PETG/PC/TPU blend were characterized using a universal testing machine, and results were compared against two commercial thermoplastic products -Erkodur and Biolon. Blending modification improved the properties of PETG/PC/TPU. When blending ratio (wt%) was 70/10/20, PETG/PC/TPU exhibited optimal mechanical properties which exceeded those of Erkodur and Biolon. Tear strength was 50.23 MPa and elongation at break was 155.99%. Stress relaxation rate was 0.0136 N/s after 1 hour, which was significantly slower than Erkodur and Biolon (p<0.05). Water absorption rate was 0.57% after 2 weeks, which was significantly lower than Erkodur and Biolon (p<0.05). PMID:22123023

Zhang, Ning; Bai, Yuxing; Ding, Xuejia; Zhang, Yu

2011-11-25

168

Microcellular Foams Based on High Performance Thermoplastic Nanocomposites  

SciTech Connect

Foams from engineering thermoplastics nanocomposites based on Polyethersulphone and Polyethylene-2,6-naphthalate were prepared by using two different nanofillers (Silica nanoparticles and Graphite nanosheets). The effects of the nanofiller type and content on the foaming process was investigated and related to the density and cellular morphology of foams. The nanocomposite foams based on PES matrix exhibited improved nucleated cells both with SiO{sub 2} and Graphite nanosheets, but the density increased at all temperatures. On the contrary, nanocomposite foams based on PEN matrix showed different behaviors with the filler type. In this case, in fact, silica nanoparticles allowed lower densities when compared to the unfilled polymer foams, without influencing cells density. The Graphite nanosheets extended towards higher temperatures the foaming window of PEN nanocomposites, allowing densities as low as 0.15 at 260 deg. C.

Sorrentino, Luigi; Iannace, Salvatore [Institute for Composite and Biomedical Materials-National Research Council Piazzale V. Tecchio, 80-80125 Napoli (Italy)] [IMAST-Technological District in Polymer and Composite Engineering P.le Fermi 1 80055 Portici (Italy); Gargiulo, Marcella [Institute for Composite and Biomedical Materials-National Research Council Piazzale V. Tecchio, 80-80125 Napoli (Italy); Pezzullo, Giuseppe [Department of Materials and Production Engineering-University of Napoli Federico II Piazzale V. Tecchio, 80-80125 Napoli (Italy)

2010-06-02

169

Semi-interpenetrating polymer network's of polyimides: Fracture toughness  

NASA Technical Reports Server (NTRS)

The objective was to improve the fracture toughness of the PMR-15 thermosetting polyimide by co-disolving LaRC-TPI, a thermoplastic polyimide. The co-solvation of a thermoplastic into a thermoset produces an interpenetration of the thermoplastic polymer into the thermoset polyimide network. A second research program was planned around the concept that to improve the fracture toughness of a thermoset polyimide polymer, the molecular weight between crosslink points would be an important macromolecular topological parameter in producing a fracture toughened semi-IPN polyimide.

Hansen, Marion Glenn

1988-01-01

170

Development of Lignin-Based Polyurethane Thermoplastics  

SciTech Connect

In our continued effort to develop value-added thermoplastics from lignin, here we report utilizing a tailored feedstock to synthesize mechanically robust thermoplastic polyurethanes at very high lignin contents (75 65 wt %). The molecular weight and glass transition temperature (Tg) of lignin were altered through cross-linking with formaldehyde. The cross-linked lignin was coupled with diisocyanate-based telechelic polybutadiene as a network-forming soft segment. The appearance of two Tg s, around 35 and 154 C, for the polyurethanes indicates the existence of two-phase morphology, a characteristic of thermoplastic copolymers. A calculated Flory-Huggins interaction parameter of 7.71 also suggests phase immiscibility in the synthesized lignin polyurethanes. An increase in lignin loading increased the modulus, and an increase in crosslink-density increased the modulus in the rubbery plateau region of the thermoplastic. This path for synthesis of novel lignin-based polyurethane thermoplastics provides a design tool for high performance lignin-based biopolymers.

Saito, Tomonori [ORNL] [ORNL; Perkins, Joshua H [ORNL] [ORNL; Jackson, Daniel C [ORNL] [ORNL; Trammell, Neil E [ORNL] [ORNL; Hunt, Marcus A [ORNL] [ORNL; Naskar, Amit K [ORNL] [ORNL

2013-01-01

171

A Study on New Composite Thermoplastic Propellant  

NASA Astrophysics Data System (ADS)

Efforts have been paid to realize a new composite propellant using thermoplastics as a fuel binder and lithium as a metallic fuel. Thermoplastics binder makes it possible the storage of solid propellant in small blocks and to provide propellants blocks into rocket motor case at a quantity needed just before use, which enables the production facility of solid propellant at a minimum level, thus, production cost significantly lower. Lithium has been a candidate for a metallic fuel for the ammonium perchlorate based composite propellants owing to its capability to reduce the hydrogen chloride in the exhaust gas, however, never been used because lithium is not stable at room conditions and complex reaction products between oxygen, nitrogen, and water are formed at the surface of particles and even in the core. However, lithium particles whose surface shell structure is well controlled are rather stable and can be stored in thermoplastics for a long period. Evaluation of several organic thermoplastics whose melting temperatures are easily tractable was made from the standpoint of combustion characteristics, and it is shown that thermoplastics propellants can cover wide range of burning rate spectrum. Formation of well-defined surface shell of lithium particles and its kinetics are also discussed.

Kahara, Takehiro; Nakayama, Masanobu; Hasegawa, Hiroshi; Katoh, Kazushige; Miyazaki, Shigehumi; Maruizumi, Haruki; Hori, Keiichi; Morita, Yasuhiro; Akiba, Ryojiro

172

Plastic wastes as modifiers of the thermoplasticity of coal  

SciTech Connect

Plastic waste recycling represents a major challenge in environmental protection with different routes now available for dealing with mechanical, chemical, and energy recycling. New concepts in plastic waste recycling have emerged so that now such wastes can be used to replace fossil fuels, either as an energy source or as a secondary raw material. Our objective is to explore the modification of the thermoplastic properties of coal in order to assess the possibility of adding plastic waste to coal for the production of metallurgical coke. Two bituminous coals of different rank and thermoplastic properties were used as a base component of blends with plastic wastes such as high-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene (PP), polystyrene (PS), poly(ethylene terephthalate) (PET), and acrilonitrile-butadiene-styrene copolymer (ABS). In all cases, the addition of plastic waste led to a reduction in Gieseler maximum fluidity, the extent of the reduction depending on the fluidity of the base coal, and the amount, the molecular structure, and the thermal behavior of the polymer. As a consequence, the amount of volatile matter released by the plastic waste before, during, and after the maximum fluidity of the coal and the hydrogen-donor and hydrogen-acceptor capacities of the polymer were concluded to be key factors in influencing the extent of the reduction in fluidity and the development of anisotropic carbons. The incorporation of the plastic to the carbon matrix was clearly established in semicokes produced from blends of a high-fluid coal and the plastic tested by SEM examination. 42 refs., 10 figs., 7 tabs.

M.A. Diez; C. Barriocanal; R. Alvarez [Instituto Nacional del Carbon (INCAR), Oviedo (Spain)

2005-12-01

173

Carbon nanotubes in blends of polycaprolactone/thermoplastic starch.  

PubMed

Despite the importance of polymer-polymer multiphase systems, very little work has been carried out on the preferred localization of solid inclusions in such multiphase systems. In this work, carbon nanotubes (CNT) are dispersed with polycaprolactone (PCL) and thermoplastic starch (TPS) at several CNT contents via a combined solution/twin-screw extrusion melt mixing method. A PCL/CNT masterbatch was first prepared and then blended with 20 wt% TPS. Transmission and scanning electron microscopy images reveal a CNT localization principally in the TPS phase and partly at the PCL/TPS interface, with no further change by annealing. This indicates a strong driving force for the CNTs toward TPS. Young's model predicts that the nanotubes should be located at the interface. X-ray photoelectron spectroscopy (XPS) of extracted CNTs quantitatively confirms an encapsulation by TPS and reveals a covalent bonding of CNTs with thermoplastic starch. It appears likely that the nanotubes migrate to the interface, react with TPS and then are subsequently drawn into the low viscosity TPS phase. In a low shear rate/low shear stress internal mixer the nanotubes are found both in the PCL phase and at the PCL/TPS interface and have not completed the transit to the TPS phase. This latter result indicates the importance of choosing appropriate processing conditions in order to minimize kinetic effects. The addition of CNTs to PCL results in an increase in the crystallization temperature and a decrease in the percent crystallinity confirming the heterogeneous nucleating effect of the nanotubes. Finally, DMA analysis reveals a dramatic decrease in the starch rich phase transition temperature (~26 °C), for the system with nanotubes located in the TPS phase. PMID:23987335

Taghizadeh, Ata; Favis, Basil D

2013-10-15

174

Crystallization of Polymers from Stressed Melts  

Microsoft Academic Search

In the last decade, there have been several investigations into the route by which a polymer melt that has been subjected to flow transforms into a crystalline state. Crystallization of polymers from flowing or stressed melts is a technologically important problem since most thermoplastics are subjected to intense flow fields during normal processing operations. The renewed interest in this problem

Guruswamy Kumaraswamy

2005-01-01

175

Advanced polymer components. Volume 2. Final report  

Microsoft Academic Search

The Advanced Polymer Components Initiative began in December l989. The initial purpose of the program was to explore advanced engineering polymers for use as rocket propulsion components. As research progressed it became apparent that advanced thermoplastics in general were highly dependent on processing and post-processing as well as on chemical composition and morphology. This realization led to a branching of

Rusek

1995-01-01

176

Plasticizer-assisted polymer imprint and transfer  

Microsoft Academic Search

We have developed a new method to pattern polymeric materials, including non-thermoplastic polymers, at low temperature and low pressure. In this method, plasticizers are added to increase the chain mobility of the polymers, resulting in lower imprinting temperature and\\/or pressure. Two established imprinting and transfer techniques were chosen to demonstrate this method, namely, conventional nanoimprint lithography (NIL) and microcontact printing

Li Tan; Yen Peng Kong; Stella W. Pang; Albert F. Yee

2004-01-01

177

Polymer\\/metal composite for interconnection technology  

Microsoft Academic Search

In this paper, we report on the the rheological, electrical and mechanical properties of paste which is composed of a thermoplastic polymer, solvent and silver particles, and the resulting polymer\\/metal composite (PMC) which forms after the solvent from the paste has dried. We will refer to the two states as paste and PMC. The paste properties indicate the applicability of

R. F. Saraf; J. M. Roldan; R. Jagannathan; C. Sambucetti; J. Marino; C. Jahnes

1995-01-01

178

Environmentally degradable, high-performance thermoplastics from phenolic phytomonomers  

NASA Astrophysics Data System (ADS)

Aliphatic polyesters, such as poly(lactic acid), which degrade by hydrolysis, from naturally occurring molecules form the main components of biodegradable plastics. However, these polyesters have become substitutes for only a small percentage of the currently used plastic materials because of their poor thermal and mechanical properties. Polymers that degrade into natural molecules and have a performance closer to that of engineering plastics would be highly desirable. Although the use of a high-strength filler such as a bacterial cellulose or modified lignin greatly increases the plastic properties, it is the matrix polymer that determines the intrinsic properties of the composite. The introduction of an aromatic component into the thermoplastic polymer backbone is an efficient method to intrinsically improve the material performance. Here, we report the preparation of environmentally degradable, liquid crystalline, wholly aromatic polyesters. The polyesters were derived from polymerizable plant-derived chemicals-in other words, `phytomonomers' that are widely present as lignin biosynthetic precursors. The mechanical performance of these materials surpasses that of current biodegradable plastics, with a mechanical strength, ?, of 63MPa, a Young's modulus, E, of 16GPa, and a maximum softening temperature of 169?C. On light irradiation, their mechanical properties improved further and the rate of hydrolysis accelerated.

Kaneko, Tatsuo; Thi, Tran Hang; Shi, Dong Jian; Akashi, Mitsuru

2006-12-01

179

Polyurethane thermoplastic elastomers with inherent radiopacity for biomedical applications.  

PubMed

Synthesis and characterization of three different radiopaque thermoplastic polyurethane elastomers are reported. Radiopacity was introduced to the polyurethanes by incorporating an iodinated chain extender, namely, 4,4'-isopropylidinedi-(2,6-diiodophenol) (IBPA), into the polymer chain during polyurethane synthesis. Radiopaque polyurethanes (RPUs) were synthesized by reacting 4,4'-methylenebis(phenyl isocyanate) (MDI), IBPA, and three different diols. The polyols used for the synthesis were polypropylene glycol, polycaprolactone diol, and poly(hexamethylene carbonate) diol. RPUs were characterized by infrared spectroscopy, contact angle measurements, thermogravimetry, dynamic mechanical analysis, energy dispersive X-ray analysis, gel permeation chromatography, X-ray fluorescence spectroscopy, and X-radiography. X-ray images showed that all RPUs prepared using IBPA as the chain extender are highly radiopaque compared with an Aluminum wedge of equivalent thickness. Elemental analysis revealed that the polyurethanes contained 18-19% iodine in the polymer matrix. The RPUs developed have radiopacity equivalent to that of a polymer filled with 20 wt % barium sulfate. Results revealed that RPUs of wide range of properties may be produced by incorporating different diols as the soft chain segment. Cell culture cytotoxicity studies conducted using L929 cells by direct contact test and MTT assay proved that these RPUs are noncytotoxic in nature. PMID:22815186

Kiran, S; James, Nirmala R; Jayakrishnan, A; Joseph, Roy

2012-12-01

180

Process for crosslinking and extending conjugated diene-containing polymers  

NASA Technical Reports Server (NTRS)

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.

Bell, Vernon L. (inventor); Havens, Stephen J. (inventor)

1977-01-01

181

Reactive recycling of multiphase polymer systems through electron beam  

NASA Astrophysics Data System (ADS)

Recycling of polymer structural materials leads to two main obstacles: degradation of macromolecular chains and incompatibility of different polymer components. Both obstacles can be avoided by applying a reactive additive which acts as a functional compatibilizer. Electron-beam processing has been successfully applied to produce multiphase polymer composites using recycled polyester fibers, wood fibers, glass fibers and minerals as reinforcements in thermoplastic matrix.

Czvikovszky, Tibor

1995-11-01

182

A multi-purpose thermoplastic polyimide  

NASA Technical Reports Server (NTRS)

A linear thermoplastic polyimide, LARC-TPI, has been characterized and developed for a variety of high-temperature applications. In its fully imidized form, this new material can be used as an adhesive for bonding metals such as titanium, aluminum, copper, brass, and stainless steel. LARC-TPI is being evaluated as a thermoplastic for bonding large pieces of polyimide film to produce flexible, 100% void-free laminates for flexible circuit applications. The further development of LARC-TPI as a potential molding powder, composite matrix resin, high-temperature film and fiber is also discussed.

Saint Clair, A. K.; Saint Clair, T. L.

1981-01-01

183

Selecting thermoplastics for engineering applications. Second edition  

SciTech Connect

The difficult problem of selecting the best thermoplastic resin is made easier by the guidelines presented in this book. Included are methods of ranking the thermoplastics by their properties, price, and processability, along with quick-reference tables of rankings. Example programs for computerized ranking are also included. The problems of matching part design and molding conditions are also addressed. Contents include: (1) the selection process; (2) physical properties; (3) rheological properties; (4) injection molding; (5) prototype parts; (6) estimating part costs; (7) ranking of resins; (8) computerized approach to selection; (9) expert system SELECTHER; (10) resin suppliers; and (11) nomenclature and glossary.

MacDermott, C.P.; Shenoy, A.V.

1997-12-31

184

Rheology of Thermoplastic Foam Extrusion.  

National Technical Information Service (NTIS)

A phenomenological model of flow in an extrusion die has been developed. The macroscopic effect of the phase change from a homogeneous polymer melt, that contains a blowing agent, to a foam can be described in terms of two dimensionless parameters, alpha ...

A. M. Kraynik

1982-01-01

185

Composites of thermoplastic starch and nanoclays produced by extrusion and thermopressing.  

PubMed

The aim of this study was to produce thermoplastic starch (TPS) films and to enhance their properties by reinforcing them with hydrophilic and hydrophobic nanoclays. TPS films were prepared by extrusion and thermopressing, and their crystallinity, water vapor permeability (WVP), and mechanical properties were studied. The hydrophilic nanoclay lowered the material WVP due to the formation of an intercalated composite. The hydrophobic nanoclays increased the rigidity of the films but did not alter the tensile strength. The blending of nanoclays with thermoplastic starch modifies the mechanical properties and WVP, and these changes are strongly associated with the dispersion of nanoclay in the polymer matrix. The dispersion, in turn, depends on the compatibility of the matrix and the nanoclay in terms of the hygroscopicity and the concentration in which the nanoclay is used. The addition of nanoclays to starch-based films is a promising way to enhance them for industrial manufacture. PMID:24750751

Müller, Carmen M O; Laurindo, João Borges; Yamashita, Fabio

2012-06-20

186

In-Plane Shear Characterisation of Uni-Directionally Reinforced Thermoplastic Melts  

NASA Astrophysics Data System (ADS)

Intra-ply shear is an important mechanism in hot stamp forming processes of UD fibre reinforced thermoplastic laminates. Various methods have been developed to characterise this shear mechanism, but measured properties may differ for several orders of magnitude. Therefore, an alternative method to characterise the longitudinal shearing viscosity is presented. Straight fibre reinforced thermoplastic bars with a rectangular cross section are subjected to torsional loadings. The specimens' response can be used to characterise the shear properties of the fibre reinforced polymer melt. Different geometries and clamping conditions were modelled to show the sensitivity of the measured viscosity. Based on this, experiments were performed with thick bars with a PEI-AS4 and PEEK-AS4 composition. Frequency sweeps were applied at different temperatures. All measurements showed a clear shear thinning behaviour, which can conveniently be described with a power law model.

Haanappel, S. P.; Ten Thije, R.; Sachs, U.; Rietman, A. D.; Akkerman, R.

2011-05-01

187

Assessment of relative flammability and thermochemical properties of some thermoplastic materials  

NASA Technical Reports Server (NTRS)

The thermochemical and flammability characteristics of some typical thermoplastic materials currently in use and others being considered for use in aircraft interiors are described. The properties studied included (1) thermal mechanical properties such as glass transition and melt temperature, (2) changes in polymer enthalpy by differential scanning calorimetry, (3) thermogravimetric analysis in an anaerobic and oxidative environment, (4) oxygen index, (5) smoke evolution, (6) relative toxicity of the volatile products of pyrolysis, and (7) selected physical properties. The generic polymers which were evaluated included: acrylonitrile-butadiene-styrene, bisphenol A polycarbonate, bisphenol fluorenone carbonatedimethylsiloxane block polymer, phenolphthalein-bisphenol A polycarbonate, phenolphthalein polycarbonate, polyether sulfone, polyphenylene oxide, polyphenylene sulfide, polyaryl sulfone, chlorinated polyvinyl chloride homopolymer, polyvinyl fluoride, and polyvinylidene fluoride. Processing parameters including molding characteristics of some of the advanced polymers are described. Test results and relative rankings of some of the flammability, smoke and toxicity properties are presented.

Kourtides, D. A.; Parker, J. A.

1978-01-01

188

Characterization of flammability properties of some thermoplastic and thermoset resins. [for aircraft interiors  

NASA Technical Reports Server (NTRS)

The thermochemical and flammability properties of some thermally stable polymers considered for use in aircraft interiors are described. The properties studied include: (1) thermomechanical properties such as glass transition and melt temperature; (2) dynamic thermogravimetric analysis in anaerobic environment; (3) flammability properties such as oxygen index, flame spread, and smoke evolution; and (4) selected physical properties. The thermoplastic polymers evaluated included polyphenylene sulfide, polyaryl sulfone, 9,9-bis(4-hydroxyphenyl)-fluorene polycarbonate-poly(dimethylsiloxane) and polyether sulfone. The thermoset polymers evaluated included epoxy, bismaleimide, a modified phenolic and polyaromatic melamine resin. These resins were primarily used in the fabrication of glass reinforced prepregs for the construction of experimental panels. Test results and relative rankings of some of the flammability parameters are presented and the relationship of the molecular structure, char yield, and flammability properties of these polymers are discussed.

Kourtides, D. A.; Parker, J. A.

1978-01-01

189

Polypropylene ionic thermoplastic elastomers: Synthesis and properties  

Microsoft Academic Search

Polypropylene ionic thermoplastic elastomers have been prepared by melt radical grafting of maleic anhydride onto polypropylene in the presence of N-bromosuccinimide followed by neutralization of the resulting elastomeric grafted polypropylene using sodium salts. Sodium hydroxide and sodium acetate were compared in aqueous solution, as anhydrous or hydrated powders. The neutralization reaction was followed by Fourier transform infrared spectroscopy, allowing the

Dimitri D. J. Rousseaux; Xavier Drooghaag; Michel Sclavons; Pierre Godard; Veronique Carlier; Jacqueline Marchand-Brynaert

2010-01-01

190

Thermoplastic Composite Materials for Aerospace Applications  

NASA Astrophysics Data System (ADS)

Mechanical and thermo-physical properties of composites materials with thermoplastic matrix (PEEK/IM7, TPI/IM7 and PPS/IM7) used for aerospace applications have been analyzed as function of two different process techniques: compression molding and fiber placement process ``hot gas assisted.''

Casula, G.; Lenzi, F.; Vitiello, C.

2008-08-01

191

Thermoplastic/melt-processable polyimides  

NASA Technical Reports Server (NTRS)

Several polyimides were prepared which show promise for aircraft composite applications. This was achieved through a systematic polymer synthesis program where the glass transition temperatures were greatly lowered when compared to the older polyimide systems. Several of the materials were shown to be hot-melt processable and are attractive matrix resin candidates especially in light of their high g(sub Ic) values. At least two of these polyimides are available for evaluation and others are on the research horizon.

St.clair, T. L.; Burks, H. D.

1984-01-01

192

Vegetable Oil Derived Solvent, and Catalyst Free "Click Chemistry" Thermoplastic Polytriazoles  

PubMed Central

Azide-alkyne Huisgen “click” chemistry provides new synthetic routes for making thermoplastic polytriazole polymers—without solvent or catalyst. This method was used to polymerize three diester dialkyne monomers with a lipid derived 18 carbon diazide to produce a series of polymers (labelled C18C18, C18C9, and C18C4 based on monomer chain lengths) free of residual solvent and catalyst. Three diester dialkyne monomers were synthesized with ester chain lengths of 4, 9, and 18 carbons from renewable sources. Significant differences in thermal and mechanical properties were observed between C18C9 and the two other polymers. C18C9 presented a lower melting temperature, higher elongation at break, and reduced Young's modulus compared to C18C4 and C18C18. This was due to the “odd-even” effect induced by the number of carbon atoms in the monomers which resulted in orientation of the ester linkages of C18C9 in the same direction, thereby reducing hydrogen bonding. The thermoplastic polytriazoles presented are novel polymers derived from vegetable oil with favourable mechanical and thermal properties suitable for a large range of applications where no residual solvent or catalyst can be tolerated. Their added potential biocompatibility and biodegradability make them ideal for applications in the medical and pharmaceutical industries.

Floros, Michael C.; Leao, Alcides Lopes; Narine, Suresh S.

2014-01-01

193

Thermoplastic processing of proteins for film formation--a review.  

PubMed

Increasing interest in high-quality food products with increased shelf life and reduced environmental impact has encouraged the study and development of edible and/or biodegradable polymer films and coatings. Edible films provide the opportunity to effectively control mass transfer among different components in a food or between the food and its surrounding environment. The diversity of proteins that results from an almost limitless number of side-chain amino-acid sequential arrangements allows for a wide range of interactions and chemical reactions to take place as proteins denature and cross-link during heat processing. Proteins such as wheat gluten, corn zein, soy protein, myofibrillar proteins, and whey proteins have been successfully formed into films using thermoplastic processes such as compression molding and extrusion. Thermoplastic processing can result in a highly efficient manufacturing method with commercial potential for large-scale production of edible films due to the low moisture levels, high temperatures, and short times used. Addition of water, glycerol, sorbitol, sucrose, and other plasticizers allows the proteins to undergo the glass transition and facilitates deformation and processability without thermal degradation. Target film variables, important in predicting biopackage performance under various conditions, include mechanical, thermal, barrier, and microstructural properties. Comparisons of film properties should be made with care since results depend on parameters such as film-forming materials, film formulation, fabrication method, operating conditions, testing equipment, and testing conditions. Film applications include their use as wraps, pouches, bags, casings, and sachets to protect foods, reduce waste, and improve package recyclability. PMID:18298745

Hernandez-Izquierdo, V M; Krochta, J M

2008-03-01

194

Processing Conjugated-Diene-Containing Polymers  

NASA Technical Reports Server (NTRS)

Diels-Alder reaction used to cross-linked thermoplastics. Process uses Diels-Alder reaction to cross-link and/or extend conjugated-diene-containing polymers by reacting them with bis-unsaturated dienophiles results in improved polymer properties. Quantities of diene groups required for cross-linking varies from very low to very high concentrations. Process also used to extend, or build up molecular weights of, low-molecular-weight linear polymers with terminal conjugated dienic groups.

Bell, Vernon L.; Havens, Stephen J.

1987-01-01

195

40 CFR 414.40 - Applicability; description of the thermoplastic resins subcategory.  

Code of Federal Regulations, 2011 CFR

...Applicability; description of the thermoplastic resins subcategory. 414.40 Section 414...AND SYNTHETIC FIBERS Thermoplastic Resins § 414.40 Applicability; description of the thermoplastic resins subcategory. The provisions...

2011-07-01

196

40 CFR 414.40 - Applicability; description of the thermoplastic resins subcategory.  

Code of Federal Regulations, 2012 CFR

...Applicability; description of the thermoplastic resins subcategory. 414.40 Section 414...AND SYNTHETIC FIBERS Thermoplastic Resins § 414.40 Applicability; description of the thermoplastic resins subcategory. The provisions...

2012-07-01

197

Surface Treatment of Polymers with Activated Gas Plasma for Adhesive Bonding.  

National Technical Information Service (NTIS)

Several thermoplastic polymers were treated with activated helium and with activated oxygen. Bond strengths of adhesive-bonded specimens prepared from treated and from untreated coupons were compared. Treatment with activated gas plasma prior to bonding s...

J. R. Hall C. A. L. Westerdahl A. T. Devine M. J. Bodnar

1969-01-01

198

Production of continuous fiber thermoplastic composites by in-situ pultrusion  

NASA Astrophysics Data System (ADS)

The constructive design in the automotive industry, but also in many other industrial sectors has changed steadily over the past decades. It became much more complex due to e.g. increased use of hybrid materials. Combined with the desire to minimize the weight of vehicles and thus the CO2 emissions, the use of low density materials and especially fiber-reinforced plastics is increasing. E.g. Continuous fiber thermoplastic composites are used to reinforce injection molded parts. Low viscosity monomers like caprolactam, which is used to produce polyamide 6 by anionic polymerization are able to easily impregnate and penetrate the textile reinforcement. After wetting the fibers, the ring-opening polymerization starts and the matrix is becoming a polymer. At IKT, a method based on the RIM process (reaction injection molding) was developed to produce continuous fiber thermoplastic composites with high contents of continuous glass fibers. The anionic polymerization of polyamide 6 was now combined with the pultrusion process. Continuous glass fibers are pulled through a mold and wetted with caprolactam (including activator and catalyst). After the material polymerized in the mould, the finished continuous fiber thermoplastic composites can be pulled out and is finally sawn off.

Epple, S.; Bonten, C.

2014-05-01

199

Properties of thermoplastic blends: starch–polycaprolactone  

Microsoft Academic Search

Different compositions of wheat thermoplastic starch (TPS) and polycaprolactone (PCL) are melt blended by extrusion and injected. Different properties are determined: mechanical properties (tensile and impact tests), thermal and thermomechanical properties (DSC and DMTA) and hydrophobicity (contact angle measurement). A large range of blends is analysed with different glycerol (plasticizer):starch contents ratios (0.14:0.54) and various PCL concentrations (up to 40wt.%).

L. Averous; L. Moro; P. Dole; C. Fringant

2000-01-01

200

Challenges in Biomass–Thermoplastic Composites  

Microsoft Academic Search

Wood and other biomass resources have been blended with thermoplastic such as polyethylene, polypropylene, polylactic acid\\u000a and polyvinyl chloride to form wood plastic composites (WPC). WPCs have seen a large growth in the United States in recent\\u000a years mainly in the residential decking market with the removal of CCA treated wood decking from residential markets. While\\u000a there are many successes

Roger M. Rowell

2007-01-01

201

Rheological and Microstructural Features of Phase Transitions in Composite Polymer Materials Based on Tar and Polyethylene  

NASA Astrophysics Data System (ADS)

The change in the structure of tar- and polyethylene-based petroleum and polymer systems has been investigated by the methods of viscosity measurement and atomic force scanning microscopy. It has been established that the structural change of a composite petroleum and polymer thermoplastic material in the region of phase transitions of the 2nd kind results from the collapse of polymer coils and the formation of globules that subsequently aggregate. It has been shown using atomic-force-microscopy that a volume superlattice is formed from polymer globules in thermoplastic petroleum polymers in the region of phase transition of the 2nd kind.

Dolomatov, M. Yu.; Dezortsev, S. V.; Bakhtizin, R. Z.; Kharisov, B. R.; Nigmatullina, I. R.

2014-03-01

202

Foams from high performance thermoplastic PEN/PES blends with expanded graphite  

NASA Astrophysics Data System (ADS)

High performance thermoplastic blends based on PEN, PES and nanometric expanded graphite have been investigated to couple the foamability of the first polymer to the extended service temperatures of the second one. The thermo-mechanical behavior of blends was related to their composition and processing parameters for the production of foams have been explored through solid state foaming technique. The role of expanded graphite nanoparticles, of the blend composition and of the temperature was investigated to maximize the specific performances and improve the cellular morphology.

Sorrentino, L.; Cafiero, L.; Iannace, S.

2014-05-01

203

Aminosilane layers on the plasma activated thermoplastics: influence of solvent on its structure and morphology.  

PubMed

The chemistry and the structure of aminosilane layer on the plasma activated thermoplastic substrates, e.g., polycarbonate (PC), polystyrene (PS), poly(methyl methacrylate) (PMMA), and cyclic olefin co-polymer (COC) were investigated at the molecular level. The nature of the surface functional groups of the silane layers prepared by solution phase deposition in aqueous and anhydrous solvents were studied using various techniques including ellipsometry, goniometry, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and attenuated total reflectance infrared spectroscopy (ATR-IR). The XPS analyses revealed the presence of various oxygen functionalities on the plasma activated thermoplastics. Considerable differences were observed for the structure of aminosilane depending on the solvent used for the reaction. Deposition from aqueous solution resulted in relatively flat and smooth surfaces with consistent thickness compared to the anhydrous solution deposition. In the former case, 33% of the total nitrogen accounted for protonated amine and 16% for the free amino groups. In the latter, only 6% accounted for the protonated amine. The point of zero charge (pzc), on the aminosilane modified PC was found to be around 7, indicated that the surface is positively charged below pH 7 and negatively charged above pH 7. The surface analysis data suggested that various interactions are possible between the plasma activated thermoplastic surface and the aminosilane. In general, they are bound to the surface through covalent bond formation between the oxygen functionalities on the thermoplastic surface and the amino or the silanol groups of the aminosilane. PMID:24050640

Sunkara, Vijaya; Cho, Yoon-Kyoung

2013-12-01

204

Thermoforming of Continuous Fibre Reinforced Thermoplastic Composites  

NASA Astrophysics Data System (ADS)

The introduction of new materials, particularly for aerospace products, is not a simple, quick or cheap task. New materials require extensive and expensive qualification and must meet challenging strength, stiffness, durability, manufacturing, inspection and maintenance requirements. Growth in industry acceptance for fibre reinforced thermoplastic composite systems requires the determination of whole life attributes including both part processing and processed part performance data. For thermoplastic composite materials the interactions between the processing parameters, in-service structural performance and end of life recyclability are potentially interrelated. Given the large number and range of parameters and the complexity of the potential relationships, understanding for whole life design must be developed in a systematic building block approach. To assess and demonstrate such an approach this article documents initial coupon level thermoforming trials for a commercially available fibre reinforced thermoplastic laminate, identifying the key interactions between processing and whole life performance characteristics. To examine the role of the thermoforming process parameters on the whole life performance characteristics of the formed part requires a series of manufacturing trials combined with a series of characterisation tests on the manufacturing trial output. Using a full factorial test programme and considering all possible process parameters over a range of potential magnitudes would result in a very large number of manufacturing trials and accompanying characterisation tests. Such an approach would clearly be expensive and require significant time to complete, therefore failing to address the key requirement for a future design methodology capable of rapidly generating design knowledge for new materials and processes. In this work the role of mould tool temperature and blank forming temperature on the thermoforming of a commercially available thermoplastic based composite laminate is investigated followed by post processed part characterization. Key findings include an optimized composite processing window, and the influence of raw material blank forming temperature and mould tool temperature on part crystallinity and flexural strength. This process study forms one element of a major project structure which has been designed to address the gap between design, analysis and manufacturing, using at its core, a digital framework for the creation and management of performance parameters related to the lifecycle performance of thermoplastic composite structures.

McCool, Raurí; Murphy, Adrian; Wilson, Ryan; Jiang, Zhenyu; Price, Mark

2011-05-01

205

Nanoinjection Lithography for Submicrometer Electrodes on Polymer Substrates  

Microsoft Academic Search

In this paper, a high-throughput method for fabricating submicrometer electrodes on polymer substrates is introduced and results are presented. This new process, known as nanoinjection lithography, combines nanoinjection molding with trench-filling techniques to create submicrometer electrodes on thermoplastic polymers. The fabrication method and resulting electrodes are characterized in this work using scanning electron microscopy, surface profilometry, and atomic force microscopy.

Michael J. Rust; Se Hwan Lee; Chong H. Ahn

2007-01-01

206

In-situ - characterization of moisture induced swelling behaviour of microelectronic relevant polymers  

Microsoft Academic Search

For electronic application many polymer systems such as thermosets and thermoplastics with different properties are widely used. Thermosetting polymers e.g. epoxy resins, cause reliability problems when exposed to humid environments where phenomena such as moisture absorption and diffusion take place. It is important to know both absorption and desorption properties of used polymer systems. This paper presents a newly developed

H. Walter; J. Bauer; T. Braun; O. Holck; B. Wunderle; O. Wittler

2012-01-01

207

Improvements in Waterproofing Membranes by Modifying Bitumen with Thermoplastic Polymer.  

National Technical Information Service (NTIS)

Waterproofing of roofs with impermeable membranes based on bitumen modified with high modulus materials is widely employed. The mechanical and viscoelastic behavior of bitumen, either at low or at high temperatures, are appreciably improved by addition of...

S. Piazza A. Arcozzi F. Balestrazzi C. Verga S. D. Milanese

1982-01-01

208

Thermoplastic composite based processing technologies for high performance turbomachinery components  

Microsoft Academic Search

ABB is developing new designs and processes based on thermoplastic technology in response to the lack of appropriate and affordable manufacturing methods for high performance composites parts, such as rotating machine components. A complete technology platform has been developed including design methodology, rapid thermoforming processes, robotic-based thermoplastic fibre placement (TFP) and assembly procedures based on welding. It will be shown

Vishal Mallick

2001-01-01

209

Design and manufacturing of low cost thermoplastic composite bridge superstructures  

Microsoft Academic Search

An integral modular fiber thermoplastic composite bridge structural system is described. The design concept is presented by utilizing a high performance thermoplastic material (i.e. Glass\\/Polypropylene) along with an efficient low cost manufacturing process and fabrication techniques. The design is based on detailed finite element analyses to investigate the stiffness and strength of the structural system. To demonstrate the design concept, two

Nasim Uddin; Abdul Moeed Abro

2008-01-01

210

Imprinting of confining sites for cell cultures on thermoplastic substrates  

NASA Technical Reports Server (NTRS)

Prevention of test cell migration beyond the field of observation involves confining cells or cultures in microlagoons made in either a layer of grease or a thermoplastic substrate. Thermoplastic films or dishes are easily imprinted with specifically designed patterns of microlagoons.

Cone, C. D.; Fleenor, E. N.

1969-01-01

211

Thermoplastic encapsulation of waste surrogates by high-shear mixing  

SciTech Connect

Brookhaven National Laboratory (BNL) has developed a robust, extrusion-based polyethylene encapsulation process applicable to a wide range of solid and aqueous low-level radioactive, hazardous and mixed wastes. However, due to the broad range of physical and chemical properties of waste materials, pretreatment of these wastes is often required to make them amenable to processing with polyethylene. As part of the scope of work identified in FY95 {open_quotes}Removal and Encapsulation of Heavy Metals from Ground Water,{close_quotes} EPA SERDP No. 387, that specifies a review of potential thermoplastic processing techniques, and in order to investigate possible pretreatment alternatives, BNL conducted a vendor test of the Draiswerke Gelimat (thermokinetic) mixer on April 25, 1995 at their test facility in Mahwah, NJ. The Gelimat is a batch operated, high-shear, high-intensity fluxing mixer that is often used for mixing various materials and specifically in the plastics industry for compounding additives such as stabilizers and/or colorants with polymers.

Lageraaen, P.R.; Kalb, P.D.; Patel, B.R.

1995-12-01

212

Multiblock thermoplastic polyurethanes for biomedical and shape memory applications  

NASA Astrophysics Data System (ADS)

Polyurethanes are a class of polymers that are capable of tailoring the overall polymer structure and thus final properties by many factors. The great potential in tailoring polymer structures imparts PUs unique mechanical properties and good cytocompatibility, which make them good candidates for many biomedical devices. In this dissertation, three families of multiblock thermoplastic polyurethanes are synthesized and characterized for biomedical and shape memory applications. In the first case described in Chapters 2, 3 and 4, a novel family of multiblock thermoplastic polyurethanes consisting of poly(?-caprolactone) (PCL) and poly(ethylene glycol) (PEG) are presented. These materials were discovered to be very durable, with strain-to-break higher than 1200%. Heat-triggered reversible plasticity shape memory (RPSM) was observed, where the highly deformed samples completely recovered their as-cast shape within one minute when heating above the transition temperature. Instead of conventional "hard" blocks, entanglements, which result from high molecular weight, served as the physical crosslinks in this system, engendering shape recovery and preventing flow. Moreover, water-triggered shape memory effect of PCL-PEG TPUs is explored, wherein water permeated into the initially oriented PEG domains, causing rapid shape recovery toward the equilibrium shape upon contact with liquid water. The recovery behavior is found to be dependent on PEG weight percentage in the copolymers. By changing the material from bulk film to electrospun fibrous mat, recovery speed was greatly accelerated. The rate of water recovery was manipulated through structural variables, including thickness of bulk film and diameter of e-spun webs. A new, yet simple shape memory cycle, "wet-fixing" is also reported, where both the fixing and recovery ratios can be greatly improved. A detailed microstructural study on one particular composition is presented, revealing the evolution of microphase morphology during the shape memory cycle. Then, in Chapter 5, the role of Polyhedral oligosilsesquioxane (POSS) in suppressing enzymatic degradation of PCL-PEG TPUs is investigated. In vitro enzymatic hydrolytic biodegradation revealed that POSS incorporation significantly suppressed degradation of PCL-PEG TPUs. All TPUs were surface-eroded by enzymatic attack in which the chemical composition and the bulk mechanical properties exhibited little changes. A surface passivation mechanism is proposed to explain the protection of POSS-containing TPUs from enzymatic degradation. Finally, Chapter 6 presents another POSS-based TPUs system with PLA-based polyol as the glassy soft block. Manipulation of the final thermal and mechanical properties is discussed in terms of different polyols and POSS used. The free recovery and the constrained recovery responses of the polymer films were demonstrated as a function of the prior "fixing" deformation temperature. In addition, this family of materials was capable of memorizing their T g., where optimal recovery breadth and recovery stress were achieved when pre-deformation occurred right at Tg.

Gu, Xinzhu

213

Effect of Deformation History on the Morphology and Properties of Blends of Polycarbonate and a Thermotropic Liquid Crystalline Polymers.  

National Technical Information Service (NTIS)

The addition of an immiscible LCP phase improves the melt processability of a host thermoplastic polymer. In addition, by employing a suitable deformation history, the LCP phase may be elongated and oriented such that a microfibrillar morphology can be re...

A. Kohli N. Chung R. A. Weiss

1989-01-01

214

Trigeminal trophic syndrome treated with thermoplastic occlusion.  

PubMed

A 72-year-old man with a history of thrombotic CVA causing lateral medullary infarction presented with non-healing ulcers of the right side of the face of 5 months' duration. After extensive investigations, a diagnosis of trigeminal trophic syndrome was made. The ulcers progressed relentlessly despite amitriptyline and gabapentin, and he was treated with a combination of carbamazepine and thermoplastic mask occlusion of the right side of his face. Over the next 10 weeks the shallower facial ulcers began to diminish in depth and diameter, and the deeper ulcers stopped progressing. Although the patient showed early signs of healing, he died because of complications from the CVA. PMID:21332680

Kurien, Anil M; Damian, Diona L; Moloney, Fergal J

2011-02-01

215

Thermochemical characterization of some thermoplastic materials. [flammability and toxicity properties for aircraft interiors  

NASA Technical Reports Server (NTRS)

The thermochemical and flammability characteristics of some typical thermoplastic materials currently in use or being considered for use in aircraft interiors are described. The properties studied included thermomechanical properties such as glass-transition and melt temperature, changes in polymer enthalpy, thermogravimetric analysis in anerobic and oxidative environments, oxygen index, smoke evolution, relative toxicity of the volatile products of pyrolysis, and selected physical properties. The generic polymers evaluated included acrylonitrile butadiene styrene, bisphenol A polycarbonate, 9,9 bis (4-hydroxyphenyl) fluorene polycarbonate-poly (dimethylsiloxane) block polymer, phenolphthalein-bisphenol A polycarbonate, phenolphthalein polycarbonate, polyether sulfone, polyphenylene oxide, polyphenylene sulfide, polyaryl sulfone, chlorinated polyvinyl chloride homopolymer, polyvinyl fluoride, and polyvinylidene fluoride. Processing parameters, including molding characteristics of some of the advanced polymers, are described. Test results and relative rankings of some of the flammability, smoke, and toxicity properties are presented. Under these test conditions, some of the advanced polymers evaluated were significantly less flammable and toxic than or equivalent to polymers in current use.

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

1977-01-01

216

Surface grafting of carboxylic groups onto thermoplastic polyurethanes to reduce cell adhesion  

NASA Astrophysics Data System (ADS)

The interaction of polymers with other materials is an important issue, being their surface properties clearly crucial. For some important polymer applications, their surfaces have to be modified. Surface modification aims to tailor the surface characteristics of a material for a specific application without affecting its bulk properties. Materials can be surface modified by using biological, chemical or physical methods. The aim of this work was to improve the reactivity of the thermoplastic polyurethane (TPU) material (Elastollan®) surface and to make its surface cell repellent by grafting carboxylic groups onto its surface. Two TPU materials were studied: a polyether-based TPU and a polyester-based TPU. The grafting efficiency was evaluated by contact angle measurements and by analytical determination of the COOH groups. Scanning electron microscopy (SEM) of the membranes surface was performed as well as cell adhesion tests. It was proved that the surfaces of the TPUs membranes were successfully modified and that cell adhesion was remarkably reduced.

Alves, P.; Ferreira, P.; Kaiser, Jean-Pierre; Salk, Natalie; Bruinink, Arie; de Sousa, Hermínio C.; Gil, M. H.

2013-10-01

217

Microgravity Effects on Combustion of Polymers  

NASA Technical Reports Server (NTRS)

A viewgraph presentation describing various microgravity effects on the combustion of polymers is shown. The topics include: 1) Major combustion processes and controlling mechanisms in normal and microgravity environments; 2) Review of some buoyancy effects on combustion: melting of thermoplastics; flame strength, geometry and temperature; smoldering combustion; 3) Video comparing polymeric rods burning in normal and microgravity environments; and 4) Relation to spacecraft fire safety of current knowledge of polymers microgravity combustion.

Hirsch, David; Williams, Jim; Beeson, Harold

2007-01-01

218

Low Cost Processing of Commingled Thermoplastic Composites  

NASA Astrophysics Data System (ADS)

A low cost vacuum consolidation process has been investigated for use with commingled thermoplastic matrix composites. In particular, the vacuum consolidation behaviour of commingled polypropylene/glass fibre and commingled nylon/carbon fibre precursors were studied. Laminates were consolidated in a convection oven under vacuum pressure. During processing, the consolidation of the laminate packs was measured by use of non-contact eddy current sensors. The consolidation curves are then used to tune an empirical consolidation model. The overall quality of the resulting laminates is also discussed. Dynamic mechanical analysis, differential scanning calorimetry and mechanical tensile testing were also performed in order to determine the effects of varying processing parameters on the physical and mechanical properties of the laminates. Through this analysis, it was determined that the nylon/carbon fibre blend was not suitable for vacuum consolidation, while the polypropylene/glass fibre blend is a viable option for vacuum consolidation. The ultimate goal of this work is to provide a foundation from which low cost unmanned aerial vehicle (UAV) components can be designed and manufactured from thermoplastic matrix composites using a low cost processing technique as an alternative to traditional thermoset composite materials.

Chiasson, Matthew Lee

219

Acetylation of rice straw for thermoplastic applications.  

PubMed

An inexpensive and biodegradable thermoplastic was developed through acetylation of rice straw (RS) with acetic anhydride. Acetylation conditions were optimized. The structure and properties of acetylated RS were characterized by fourier transform infrared (FTIR), solid-state (13)C NMR spectroscopy, X-ray diffractometer (XRD), scanning electron microscope (SEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The results showed that acetylation of RS has successfully taken place, and comparing with raw RS, the degree of crystallinity decreased and the decomposition rate was slow. The acetylated RS has got thermoplasticity when weight ratio of RS and acetic anhydride was 1:3, using sulphuric acid (9% to RS) as catalyst in glacial acetic acid 35°C for 12h, and the dosage of solvent was 9 times RS, in which weight percent gain (WPG) of the modified RS powder was 35.5% and its percent acetyl content was 36.1%. The acetylated RS could be formed into transparent thin films with different amount of plasticizer diethyl phthalate (DEP) using tape casting technology. PMID:23688473

Zhang, Guangzhi; Huang, Kai; Jiang, Xue; Huang, Dan; Yang, Yiqi

2013-07-01

220

New photoactive polymers: Azobenzene elastomers  

Microsoft Academic Search

Azobenzene-containing elastomers have been synthesized for the first time. By free radical polymerization of methacrylate or acrylate-based monomers bearing an azobenzene moiety in solution with dissolved styrene-butadiene-styrene (SBS) triblock copolymer, azobenzene side-chain liquid crystalline polymer (SCLCP) was grafted on the rubbery polybutadiene (PB) central block of SBS. Similar to SBS, the resultant azobenzene SCLCP-grafted SBS was a thermoplastic elastomer, for

Shuying Bai

2003-01-01

221

Positron lifetime studies in thermoplastic polyimide test specimens  

NASA Technical Reports Server (NTRS)

Positron lifetime measurements were made in two thermoplastic polyimide materials recently developed at Langley. The long component lifetime values in polyimidesulfone samples are 847 + or - 81 Ps (dry) and 764 + or - 91 Ps (saturated). The corresponding values in LARC thermoplastic imides are 1080 + or - 139 Ps (dry) and 711 + or - 96 Ps (saturated). Clearly, the presence of moisture has greater effect on positron lifetime in LARC thermoplastic imides than in the case of polyimidesulfones. This result is consistent with the photomicrographic observations made on frozen water saturated specimens of these materials.

Singh, J. J.; Stclair, T. L.; Holt, W. H.; Mock, W., Jr.

1982-01-01

222

Thermal stabilities of drops of burning thermoplastics under the UL 94 vertical test conditions.  

PubMed

The properties of polymer melts will strongly affect the fire hazard of the pool induced by polymer melt flow. In this study the thermal stabilities of eight thermoplastic polymers as well as their melting drops generated under the UL 94 vertical burning test conditions were investigated by thermogravimetric experiments. It was found that the kinetic compensation effect existed for the decomposition reactions of the polymers and their drops. For polymethylmethacrylate (PMMA), high impact polystyrene (HIPS), poly(acrylonitrile-butadiene-styrene) (ABS), polyamide 6 (PA6), polypropylene (PP) and low density polyethylene (LDPE), the onset decomposition temperature and the two decomposition kinetic parameters (the pre-exponential factor and the activation energy) of the drop were less than those of the polymer. However, the onset decomposition temperature and the two kinetic parameters of PC's drop were greater than those of polycarbonate (PC). Interestingly, for polyethylenevinylacetate (EVA18) the drop hardly contained the vinyl acetate chain segments. Similarly, for the PMMA/LDPE blends and the PMMA/PP blends, when the volume fraction of PMMA was less than 50% the drop hardly contained PMMA, implying that the blend would not drip until PMMA burned away and its surface temperature approached the decomposition temperature of the continuous phase composed of LDPE or PP. PMID:23298738

Wang, Yong; Zhang, Jun

2013-02-15

223

ACT/ICAPS: Thermoplastic composite activities  

NASA Technical Reports Server (NTRS)

McDonnell Aircraft Company (MCAIR) is teamed with Douglas Aircraft Company (DAC) under NASA's Advanced Composite Technology (ACT) initiative in a program entitled Innovative Composite Aircraft Primary Structures (ICAPS). Efforts at MCAIR have focused on the use of thermoplastic composite materials in the development of structural details associated with an advanced fighter fuselage section with applicability to transport design. Based on innovative design/manufacturing concepts for the fuselage section primary structure, elements were designed, fabricated, and structurally tested. These elements focused on key issues such as thick composite lugs and low cost forming of fastenerless, stiffener/moldline concepts. Manufacturing techniques included autoclave consideration, single diaphragm co-consolidation (SDCC), and roll-forming.

Renieri, M. P.; Burpo, S. J.; Roundy, L. M.; Todd, S. M.

1992-01-01

224

Measurement of breast volume with thermoplastic casts.  

PubMed

A pilot study was carried through to assess the reproducibility of a new method of measuring breast volume. Twenty healthy female volunteers participated. A negative replica of the breast was made with thermoplastic cast material. The volume was measured by filling the cast with water until it reached two opposite points of the boundaries of the breast delineated on the cast. Three measurements were made of every cast and the mean was calculated. The range of the three measurements expressed as a percentage of the mean volume was 2.9 (SD 1.6)%. Each volunteer's breasts were measured twice with a brief intervening pause. The coefficient of variation between the two corresponding measurements was 6%. PMID:8815982

Edsander-Nord, A; Wickman, M; Jurell, G

1996-06-01

225

Thermoplastic starch films reinforced with talc nanoparticles.  

PubMed

Nanocomposite films of thermoplastic corn starch (TPS) with talc particles were obtained by thermo-compression in order to study the effect of filler on structure, optical, and thermal properties. Talc increased the films rigid phase, thus their cross-sections resulted more irregular. Talc preferential orientation within matrix and good compatibility between particles and TPS was observed by SEM. Slight crystalline structure changes in TPS matrix were measured by XRD and DSC, due to talc nucleating effect. Randomly dispersed talc nanoagglomerates and individual platelets were assessed by TEM. Laminar morphology and nano-sized particles allowed that nanocomposite films were optically transparent. TPS-talc films resulted heterogeneous materials, presenting domains rich in glycerol and others rich in starch. Talc incorporation higher than 3%, w/w increased softening resistance of the nanocomposites as stated by DMA. Relaxation temperatures of glycerol-rich phase shifted to higher values since talc reduces the mobility of starch chains. PMID:23648028

Castillo, Luciana; López, Olivia; López, Cintia; Zaritzky, Noemí; García, M Alejandra; Barbosa, Silvia; Villar, Marcelo

2013-06-20

226

Thermoplastic Single-Ply Roof Relieves Water Damage and Inconvenience.  

ERIC Educational Resources Information Center

Assesses use of thermoplastic single-ply roofs by North Carolina's Mars Hill College to prevent leaks, reduce maintenance costs, and enhance the value of their older historic buildings. Administrators comment on the roof's installation efficiency and cleanliness. (GR)

Williams, Jennifer Lynn

2002-01-01

227

Microfluidic device fabrication by thermoplastic hot-embossing.  

PubMed

Due to their low cost compatibility with replication-based fabrication methods, thermoplastics represent an exceptionally attractive family of materials for the fabrication of lab-on-a-chip platforms. A diverse range of thermoplastic materials suitable for microfluidic fabrication is available, offering a wide selection of mechanical and chemical properties that can be leveraged and further tailored for specific applications. While high-throughput embossing methods such as reel-to-reel processing of thermoplastics is an attractive method for industrial microfluidic chip production, the use of single chip hot embossing is a cost-effective technique for realizing high-quality microfluidic devices during the prototyping stage. Here we describe methods for the replication of microscale features in two thermoplastics, polymethylmethacrylate (PMMA) and polycarbonate (PC), using hot embossing from a silicon template fabricated by deep reactive-ion etching. PMID:23329439

Yang, Shuang; Devoe, Don L

2013-01-01

228

An Assessment of Recently Developed Thermoplastic Polyurethane and Polyester Elastomers.  

National Technical Information Service (NTIS)

The processing characteristics and aging properties of thermoplastic, injection moulded polyurethane and polyester copolymer elastomers have been assessed. The aging properties of the polyurethanes showed little improvement compared with cast and millable...

J. Wright

1973-01-01

229

Evaluation of Methods Used in Heat Sealing Thermoplastic Coated Fabrics.  

National Technical Information Service (NTIS)

This two part report covers an investigation of electronic sealing equipment, methods, and techniques for heat sealing selected thermoplastic-coated fabrics. Part one is a comparison of dielectric, thermal, ultrasonic, and thermal impulse methods, for sea...

T. J. Koehler

1969-01-01

230

Characterization of Glass-Filled Engineering Thermoplastic Composites.  

National Technical Information Service (NTIS)

Characterization of three engineering thermoplastic (TP) materials has been carried out to assess suitability for Mound applications: Poly(etheretherketone) (PEEK), Poly(etherimide) (PEI), and Poly(ethersulfone) (PES). Analyses included: thermogravimetric...

A. B. Nease R. B. Whitaker R. O. Yelton

1983-01-01

231

Epoxy Thermoplastic Pavement Marking Material: Specification and Testing.  

National Technical Information Service (NTIS)

This report presents the results of an extensive laboratory program to establish a specification for an epoxy thermoplastic (ETP) striping material which was developed in a contract research study for the Federal Highway Administration by Southwest Resear...

B. H. Chollar B. R. Appleman

1980-01-01

232

Test Performance of Thermoplastic Markings on New York Concrete Pavements.  

National Technical Information Service (NTIS)

Thermoplastic centerline markings were installed at 25 sites on portland cement concrete pavement throughout New York State to evaluate their performance under various pavement and weather conditions, and to identify factors affecting their performance. T...

E. D. McNaught J. T. Capelli G. F. Gurney

1977-01-01

233

Design and Analysis of Thermoplastic Composite Bridge Superstructures.  

National Technical Information Service (NTIS)

This study is primarily focused on addressing the application of fiber reinforced composites (thermoplastics) in the design of bridge decks. Bridges are vital components of the nation's infrastructure, many of which are deteriorated. The replacement of su...

A. M. Abro N. Uddin U. Vaidya

2007-01-01

234

Interpenetrating polymer networks for biological applications.  

PubMed

The use of a sequential polymerization method for preparing interpenetrating polymer networks with biocomatible surfaces has been studied. A hydrogel monomer was made to undergo polymerization with simultaneous cross-link formation, in the presence of a swollen thermoplastic elastomer heterophase block copolymer. On removal of the swelling solvent, an interpenetrating network of the hydrogel and the thermoplastic elastomer was obtained, which absorbed water in the manner of a hydrogel, but had mechanical properties superior to hydrogels. The studies employed a poly(ether-urethane) block copolymer as the thermoplastic elastomer. The materials fabricated included samples in which the interpenetrating polymerization extended throughout the termoplastic elastomer as well as samples in which the interpenetrating polymerization was confined to a region near the surface of the latter. PMID:454781

Dror, M; Elsabee, M Z; Berry, G C

1979-01-01

235

Characterization of polyetheretherketone and other engineering thermoplastics  

SciTech Connect

Three engineering thermoplastic materials were characterized by thermal/spectroscopic means to assess their suitability in fiberglass-filled molding resins for Mound applications. The three resins examined were: polyetheretherketone (PEEK) from ICI, Ltd., polyetherimide (PEI) from General Electric, and polyethersulfone (PES) from ICI. Thermogravimetric analysis of the three thermoplastics in N/sub 2/ showed that all had a decomposition onset temperature greater than or equal to 525/sup 0/C with PEEK > PEI > PES. Melt thermal stability analyses of glass-filled PEEK and of PEI showed <1% weight loss after 2 hr (N/sub 2/). Thermomechanical analysis (TMA) of glass-filled PEEK revealed a low temperature (approx. 60/sup -/70/sup 0/C) transition below T/sub g/ (approx. 150/sup 0/C). This transition disappeared on subsequent TMA runs and did not reappear on aging at room temperature, which suggests it was the result of molding stresses. Extra transitions below T/sub g/ were also noted for PES and PEI. Direct probe/mass spectroscopy reconstructed ion chromatograms showed water and phenyl sulfone ions to be present in both PES and PEEK (and volatilized below 200/sup 0/C in vacuum). Water only was observed in PEI. The presence of phenyl sulfone in PEEK was confirmed by FT-IR, and sulfur was found in amounts up to 0.23% by weight in 30% glass-filled molding compounds. A polymerization solvent, such as diphenyl sulfone, is a probable source. Fluoride (from a monomer used in the PEEK polymerization) was also detected in amounts up to 0.17% by weight in the 30% fiberglass molding compounds.

Whitaker, R.B.; Nease, A.B.; Yelton, R.O.

1984-04-13

236

Thermoplastic media for holographic data storage  

NASA Astrophysics Data System (ADS)

The growing prevalence of digital technologies has led to increased data generation so that new storage technologies must be developed to handle expanding capacity demand. Holographic data storage is a very promising candidate with the potential to provide ultra-high density data storage. Currently, many teams are developing holographic storage technology, with much of the emphasis on professional archival applications. However, consumer-oriented applications are also growing rapidly and the requirements for these applications are different from those for professional archival storage. In particular, a holographic medium for consumer applications must be simple, cheap, and easy to process. In addition, where content distribution is the intended application, the medium must also be compatible with mastering and replication processes. We present a new holographic medium designed to meet the requirements of consumer oriented applications. The media is based on thermoplastic materials that are modified by the inclusion of photo-chemically active dyes. A series of 0.6 and 1.2 mm thick discs were injection molded and characterized for holographic storage capacity and sensitivity. The first series of samples showed large refractive index modulations of 0.03 but a poor sensitivity of 0.1 cm/J. Analysis of the data showed that the low sensitivity limited the usable capacity of the media to M/# values of ~1. A new series of dyes were synthesized with optimized efficiency and injection molded in 1.2 mm substrates. These substrates demonstrated comparable usable capacity but with significantly increased sensitivities. The results of the measurements of the injection-molded thermoplastic media are presented.

Shi, Xiaolei; Lawrence, Brian; Dubois, Marc; Boden, Eugene P.; Erben, Christoph; Longley, Kathryn L.; Nielsen, Matthew C.

2005-09-01

237

Erasable optical memory media with thermoplastic\\/absorbent double layer  

Microsoft Academic Search

A thermoplastic\\/absorbent double layer type optical memory was developed. The thermoplastic was monodispersed polystyrene of which the molecular weight was 800–110 000, and the absorbent was Cu phthalocyanine. The erasing properties were dependent on the molecular weight. The medium was best when the molecular weight was 2000 and the record\\/erase repetition could be more than 350. The dye addition to

M. Kobayashi; A. Yabe; Y. Maeno; K. Oishi; K. Kawamura; S. Ohno

1988-01-01

238

CREEP MODELING FOR INJECTION-MOLDED LONG-FIBER THERMOPLASTICS  

Microsoft Academic Search

This paper proposes a model to predict the creep response of injection-molded long-fiber thermoplastics (LFTs). The model accounts for elastic fibers embedded in a thermoplastic resin that exhibits the nonlinear viscoelastic behavior described by the Schaperys model. It also accounts for fiber length and orientation distributions in the composite formed by the injection-molding process. Fiber length and orientation distributions were

Ba Nghiep Nguyen; Vlastimil Kunc; Satish K. Bapanapalli

2008-01-01

239

Semicrystalline thermoplastic elastomeric polyolefins: Advances through catalyst development and macromolecular design.  

PubMed

We report the design, synthesis, morphology, phase behavior, and mechanical properties of semicrystalline, polyolefin-based block copolymers. By using living, stereoselective insertion polymerization catalysts, syndiotactic polypropylene-block-poly(ethylene-co-propylene)-block-syndiotactic polypropylene and isotactic polypropylene-block-regioirregular polypropylene-block-isotactic polypropylene triblock copolymers were synthesized. The volume fraction and composition of the blocks, as well as the overall size of the macromolecules, were controlled by sequential synthesis of each block of the polymers. These triblock copolymers, with semicrystalline end-blocks and mid-segments with low glass-transition temperatures, show significant potential as thermoplastic elastomers. They have low Young's moduli, large strains at break, and better than 90% elastic recovery at strains of 100% or less. An isotactic polypropylene-block-regioirregular polypropylene-block-isotactic polypropylene-block-regioirregular polypropylene-block-isotactic polypropylene pentablock copolymer was synthesized that also shows exceptional elastomeric properties. Notably, microphase separation is not necessary in the semicrystalline isotactic polypropylenes to achieve good mechanical performance, unlike commercial styrenic thermoplastic elastomers. PMID:17032769

Hotta, Atsushi; Cochran, Eric; Ruokolainen, Janne; Khanna, Vikram; Fredrickson, Glenn H; Kramer, Edward J; Shin, Yong-Woo; Shimizu, Fumihiko; Cherian, Anna E; Hustad, Phillip D; Rose, Jeffrey M; Coates, Geoffrey W

2006-10-17

240

Compression thermal analysis of the consolidation process for thermoplastic matrix composites  

SciTech Connect

Consolidation of thermoplastic prepregs was measured with an integrally-heated parallel platen apparatus attached to a servo-hydraulic mechanical testing machine. The apparatus was designed as a small-scale, well-instrumented press. The lamination or consolidation process was viewed as a superposition of three distinctly occurring events identified as void volume reduction, fiber spreading, and autohesion. Consolidation was measured in relation to the original prepreg thickness and was reported as compressive or consolidation strain as a function of temperature. The derivative of the consolidation strain, the consolidation strain rate, was found to be qualitatively descriptive of viscoelastic phenomena occurring in the prepreg stack during consolidation. The apparatus was sensitive enough to identify glass and melt transitions of the polymer matrix, and to provide a measure of the net consolidation for a given processing cycle. The strain and the strain rate data were compared to thermoanalytical prepreg data obtained by Differential Scanning Calorimetry, and Dynamic Mechanical Analysis. Three different thermoplastic matrix composite systems were examined with this apparatus: Poly (etheretherketone), Poly(etherimide), and Poly(ethylene terephthalate). 21 refs.

Nelson, K.M.; Manson, J.A.E.; Seferis, J.C. (Washington Univ., Seattle (USA))

1990-07-01

241

Assessment of enhanced autofluorescence and impact on cell microscopy for microfabricated thermoplastic devices  

PubMed Central

Thermoplastics such as polystyrene (PS) and cyclo-olefin polymer (COP) have become common materials for fabrication of microfluidic cell-based systems because of a number of attractive properties. However, thermoplastics are also known to exhibit autofluorescence levels that may hinder their utility for cell-based and imaging applications. Here we identify and characterize a phenomenon causing an increase in the autofluorescence of polystyrene after thermal treatment. This effect is of particular importance for plastic microfluidic device fabrication because the ranges of pressures and temperatures causing this effect match the same range as those used for polystyrene bonding. Further, we find that the enhanced autofluorescence has significant impact on the image quality, accuracy, and ability to identify and quantify fluorescently labeled cells. We tested two alternative strategies – solvent bonding of PS or thermal bonding of COP – to alleviate the adverse effects of heterogeneous and enhanced autofluorescence on cell image analysis, and demonstrate that both strategies are viable options to thermal bonding of PS for specific applications where cellular imaging is of primary interest.

Young, Edmond W.K.; Berthier, Erwin; Beebe, David J.

2014-01-01

242

Formation and thermal stability of BMI-based interpenetrating polymers for gas separation membranes  

Microsoft Academic Search

Semi-interpenetrating polymer networks (semi-IPNs) were prepared by sol–gel technique through in situ polymerization of bismaleimide (BMI) in thermoplastic polyetherimide (PEI) as well as in polysulfone (PSF). This synthesis route allows arresting thermoset\\/thermoplastic phase separation at an early stage by solidifying the semi-IPNs through membrane phase inversion. The phase separation could be observed visually in the casting solution or by optical

Jamal Kurdi; Ashwani Kumar

2006-01-01

243

Polymer alloys with balanced heat storage capacity and engineering attributes and applications thereof  

DOEpatents

A thermoplastic polymer of relatively low melt temperature is blended with at least one of thermosets, elastomers, and thermoplastics of relatively high melt temperature in order to produce a polymer blend which absorbs relatively high quantities of latent heat without melting or major loss of physical and mechanical characteristics as temperature is raised above the melting temperature of the low-melt-temperature thermoplastic. The polymer blend can be modified by the addition of at least one of fillers, fibers, fire retardants, compatibilisers, colorants, and processing aids. The polymer blend may be used in applications where advantage can be taken of the absorption of excess heat by a component which remains solid and retains major fractions of its physical and mechanical characteristics while absorbing relatively high quantities of latent heat.

Soroushian, Parviz (Lansing, MI)

2002-01-01

244

Characterization and recovery of shape memory polymers filled with carbon nanofibers  

Microsoft Academic Search

The microstructure and shape memory properties of polymers utilizing two different shape memory processes reinforced with vapor grown carbon nanofibers (CNFs) were investigated by thermal and thermomechanical techniques. The first shape memory polymer (SMP) was a thermoplastic polyurethane elastomer (Irogran) that used strain-induced crystallization for locking in the deformation. Shape recovery occurred through the melting temperature of the crystallites and

Daniel Stephen Powers

2008-01-01

245

Counter-ion induced processibility of polyaniline: Conducting melt processible polymer blends  

Microsoft Academic Search

Conducting polymer blends made by blending thermoplastic bulk polymers with Neste Complex, a proprietary conducting polyaniline composition, using conventional melt processing techniques are reported. The percolation threshold for conductivity is observed at astonishingly low weight fraction of the conjugated conducting polyaniline indicating the formation of a unique morphology. Results on electrical and mechanical properties of these blends are presented and

Y. Cao; A. Andreatta; P. Smith; A. J. Heeger

1995-01-01

246

Sulfur polymer cement as a low-level waste glass matrix encapsulant.  

National Technical Information Service (NTIS)

Sulfur polymer cement (SPC) is being considered as a matrix encapsulant for the Hanford low-level (activity) waste glass. SPC is an elemental sulfur polymer-stabilized thermoplastic that is fluid at 120 (degrees)C to 140(degrees)C. The candidate process w...

P. Sliva Y. B. Peng D. K. Peeler

1996-01-01

247

Morphology of Thermoplastic Elastomers: Stereoblock Polypropylene.  

National Technical Information Service (NTIS)

Many recent developments in polymer materials science have been triggered by the development of improved synthetic methods, including the development of single site catalysts for controlled polymerizations, novel polymerization techniques, and highly spec...

H. Schoenherr W. Wiyatno C. W. Frank G. G. Fuller A. P. Gast J. A. Pople R. M. Waymouth

2002-01-01

248

Transparent thermoplastics: Replication of diffractive optical elements using micro-injection molding  

NASA Astrophysics Data System (ADS)

Small plastic components with sub-micron and micron gratings for diffractive optics were prepared by micro-injection molding. The aim of the work was to improve the filling of binary diffractive gratings with high aspect ratio by varying the molding parameters. Tests were made under conventional processing conditions with four transparent thermoplastics: polycarbonate (PC), cyclo-olefin polymer (COP), styrene-acrylonitrile copolymer (SAN), and hexafluoropropylene-tetrafluoroethylene-ethylene terpolymer (HFP-TFE-Et). Melt and mold temperatures were kept as recommended by the manufacturer. Other molding parameters (injection speed, shot size, vacuum, holding pressure, and injection plunger diameter) were varied, and their effect on the profile of the gratings was measured by atomic force microscopy. The filling of the gratings (500 nm and 1000 nm) was clearly affected by injection speed, shot size, and injection piston diameter, but the most significant factor was the type of material. Replication fidelity was highest with PC and lowest with SAN.

Kalima, V.; Pietarinen, J.; Siitonen, S.; Immonen, J.; Suvanto, M.; Kuittinen, M.; Mönkkönen, K.; Pakkanen, T. T.

2007-10-01

249

Electrical Properties of a Thermoplastic Polyurethane Filled with Titanium Dioxide Nanoparticles  

SciTech Connect

In this study we report a nanodielectric system composed of pre-synthesized nanoparticles embedded in an elastomer. Nanoparticles of titanium dioxide were synthesized in an aqueous solution of titanium chloride and polyethylene glycol. The nanoparticles were blended in a twin screw extruder with a thermoplastic, polyurethane (Morthane PS455-203), to form nanodielectrics at three different weight fractions of titanium dioxide. Impedance spectroscopy was employed to study polymer dynamics and the influence of nanoparticles on relaxation. The segmental relaxation associated with the glass transition of the polyurethane matrix, and the local relaxations associated with short range motions of polar groups were investigated at wide ranges of frequency (20 Hz-1 MHz) and temperature (300-20 K). The dielectric breakdown strength of the nanodielectrics was also measured to characterize their insulating properties and their potential for use in high voltage applications.

Polyzos, Georgios [ORNL; Tuncer, Enis [ORNL; Koerner, Hilmar [Air Force Research Laboratory, Wright-Patterson AFB, OH; Kidder, Michelle [ORNL; Vaia, Richard [Air Force Research Laboratory, Wright-Patterson AFB, OH; Sauers, Isidor [ORNL; James, David Randy [ORNL; Ellis, Alvin R [ORNL

2010-01-01

250

Highly conductive thermoplastic composites for rapid production of fuel cell bipolar plates  

DOEpatents

A low cost method of fabricating bipolar plates for use in fuel cells utilizes a wet lay process for combining graphite particles, thermoplastic fibers, and reinforcing fibers to produce a plurality of formable sheets. The formable sheets are then molded into a bipolar plates with features impressed therein via the molding process. The bipolar plates formed by the process have conductivity in excess of 150 S/cm and have sufficient mechanical strength to be used in fuel cells. The bipolar plates can be formed as a skin/core laminate where a second polymer material is used on the skin surface which provides for enhanced conductivity, chemical resistance, and resistance to gas permeation.

Huang, Jianhua [Blacksburg, VA; Baird, Donald G [Blacksburg, VA; McGrath, James E [Blacksburg, VA

2008-04-29

251

Deformation-morphology correlations in electrically conductive carbonnanotube-thermoplastic polyurethane nanocomposites  

Microsoft Academic Search

Addn. of small amts. (0.5-10 vol%) of multi-wall carbon nanotubes\\u000d\\u000a\\u0009(CNT) to thermoplastic elastomer Morthane produced polymer nanocomposites\\u000d\\u000a\\u0009with high elec. cond. (??1-10 S\\/cm), low elec. percolation (??0.005)\\u000d\\u000a\\u0009and enhancement of mech. properties including increased modulus and\\u000d\\u000a\\u0009yield stress without loss of the ability to stretch the elastomer\\u000d\\u000a\\u0009above 1000% before rupture. In situ X-ray scattering during deformation\\u000d\\u000a\\u0009indicated that

Hilmar Koerner; Weidong Liu; Max Alexander; Peter Mirau; Heather Dowty; Richard A. Vaia

2005-01-01

252

Shear Strength of Single Lap Joint Aluminium-Thermoplastic Natural Rubber (Al-TPNR) Laminated Composite  

NASA Astrophysics Data System (ADS)

In this work, we studied the effect of surface treatment on the aluminium surface and a coupling agent to improve adhesion between aluminium with organic polymer. Thermoplastic natural rubber (TPNR) matrix was prepared by melt blending of natural rubber (NR), liquid natural rubber (LNR) compatibilizer, linear low density polyethylene (LLDPE) and polyethylene grafted maleic anhydride (PE-g-MAH). The PEgMAH concentration used was varied from 0% - 25%. In addition, the aluminium surface was pre-treated with 3-glycidoxy propyl trimethoxy silane (3-GPS) to enhance the mechanical properties of laminated composite. It was found that the shear strength of single lap joint Al-TPNR laminated composite showing an increasing trend as a function of PE-g-MAH contents for the 3-GPS surface treated aluminium. Moreover, the scanning electron microscope (SEM) revealed that the strength improvement was associated with the chemical state of the compound involved.

Muzakkar, M. Z.; Ahmad, S.; Yarmo, M. A.; Jalar, A.; Bijarimi, M.

2013-04-01

253

Improving the cellular morphology in high performance thermoplastics foams through blending  

NASA Astrophysics Data System (ADS)

High performance thermoplastic blends based on Poly(ethylene naphthalate)/Poly(ether sulfone) polymers were prepared by melt compounding to study the correlations between composition, morphologies and cellular structure after foaming. Blends were employed to develop high performance foams with controlled cellular morphology by using CO2 as foaming agent. The role of composition, morphology and processing conditions on the dynamic-mechanical properties of solid blends and on the micro- and nano-cellular structures of their foams was analized. Dispersed PES both extended the service temperature and acted as gas reservoir in PEN based blends, lowering the foam density with respect to neat PEN. The dispersion of PEN drops in PES extended towards lower temperatures the PES foamability, allowing the nucleation and growth of bubbles and reducing the foam density.

Cafiero, Livia; Sorrentino, Luigi; Iannace, Salvatore

2014-05-01

254

Biodegradable thermoplastic polyurethanes incorporating polyhedral oligosilsesquioxane.  

PubMed

A new hybrid thermoplastic polyurethane (TPU) system that incorporates an organic, biodegradable poly(D, L-lactide) soft block with a hard block bearing the inorganic polyhedral oligosilsesquioxane (POSS) moiety is introduced and studied. Changes in the polyol composition made through variation of the hydrophilic initiator molecular weight show direct control of the final transition temperatures. Incorporating POSS into the hard segments allows for excellent elasticity above T(g), as evidenced with dynamic mechanical analysis, not seen in most other biodegradable materials. This elasticity is attributed to physical cross-links formed in the hard block through POSS crystallization, as revealed with wide-angle X-ray diffraction. Increasing the POSS incorporation level in the TPU hard block was observed to increase crystallinity and also the rigidity of the material. The highest incorporation, using a statistical average of three POSS units per hard block, demonstrated one-way shape memory with excellent shape fixing capabilities. In vitro degradation of this sample was also investigated during a two month period. Moderate water uptake and dramatic molecular weight decrease were immediately observed although large mass loss (approximately 20 wt %) was not observed until the two month time point. PMID:18698847

Knight, Pamela T; Lee, Kyung Min; Qin, Haihu; Mather, Patrick T

2008-09-01

255

Direct molding of thermoplastic micro-parts  

NASA Astrophysics Data System (ADS)

A new micro-molding machine is described which is used to fabricate micro-parts made of a thermoplastic material. A single pellet is directly molded into a transparent mold by means of a diode laser source. A very low holding pressure is applied and no mold heating system is required; therefore the size of the micro-machine is extremely small as well as the size of the mold. The micro-machine was used to mold three different materials: high-density polyethylene (HDPE), polystyrene (PS) and acrylonitrile-butadiene-styrene (ABS). A process map was initially defined for all the materials by changing the main process variables (i.e. laser power, molding time and focalization condition). In this phase, small disks, 3.5 mm in diameter, were molded and their diameter was measured to evaluate the dimensional accuracy of the process. Subsequently, internal micro-gears in HDPE and PS and a micro-coin in ABS were molded to show the capability of the new process in the replication of the mold cavity.

Quadrini, F.; Santo, L.; Trovalusci, F.

2008-10-01

256

Accelerated Strength Testing of Thermoplastic Composites  

NASA Technical Reports Server (NTRS)

Constant ramp strength tests on unidirectional thermoplastic composite specimens oriented in the 90 deg. direction were conducted at constant temperatures ranging from 149 C to 232 C. Ramp rates spanning 5 orders of magnitude were tested so that failures occurred in the range from 0.5 sec. to 24 hrs. (0.5 to 100,000 MPa/sec). Below 204 C, time-temperature superposition held allowing strength at longer times to be estimated from strength tests at shorter times but higher temperatures. The data indicated that a 50% drop in strength might be expected for this material when the test time is increased by 9 orders of magnitude. The shift factors derived from compliance data applied well to the strength results. To explain the link between compliance and strength, a viscoelastic fracture model was investigated. The model, which used compliance as input, was found to fit the strength data only if the critical fracture energy was allowed to vary with temperature reduced stress rate. This variation in the critical parameter severely limits its use in developing a robust time-dependent strength model. The significance of this research is therefore seen as providing both the indication that a more versatile acceleration method for strength can be developed and the evidence that such a method is needed.

Reeder, J. R.; Allen, D. H.; Bradley, W. L.

1998-01-01

257

Materials for Heated Head Automated Thermoplastic Tape Placement  

NASA Technical Reports Server (NTRS)

NASA Langley Research Center (LaRC) is currently pursuing multiple paths to develop out of autoclave (OOA) polymeric composite materials and processes. Polymeric composite materials development includes the synthesis of new and/or modified thermosetting and thermoplastic matrix resins designed for specific OOA processes. OOA processes currently under investigation include vacuum bag only (VBO) prepreg/composite fabrication, resin transfer molding (RTM), vacuum assisted resin transfer molding (VARTM) and heated head automated thermoplastic tape placement (HHATP). This paper will discuss the NASA Langley HHATP facility and capabilities and recent work on characterizing thermoplastic tape quality and requirements for quality part production. Samples of three distinct versions of APC-2 (AS4/PEEK) thermoplastic dry tape were obtained from two materials vendors, TENCATE, Inc. and CYTEC Engineered Materials** (standard grade and an experimental batch). Random specimens were taken from each of these samples and subjected to photo-microscopy and surface profilometry. The CYTEC standard grade of APC-2 tape had the most voids and splits and the highest surface roughness and/or waviness. Since the APC-2 tape is composed of a thermoplastic matrix, it offers the flexibility of reprocessing to improve quality, and thereby improve final quality of HHATP laminates. Discussions will also include potential research areas and future work that is required to advance the state of the art in the HHATP process for composite fabrication.

Jensen, Brian J.; Kinney, Megan C.; Cano, Roberto J.; Grimsley, Brian W.

2012-01-01

258

Wear comparison of thermoplastic materials used for orthodontic retainers.  

PubMed

Clear thermoplastic retainers are an alternative to fixed lingual retainers and removable Hawley appliances. However, thermoplastic retainers have demonstrated poor wear resistance and durability after only a few months of use. In this study, a simulated wear device was used to compare the wear of different thermoplastic materials used for orthodontic retainers. Three thermoplastic products were evaluated: C+ (Raintree Essix, New Orleans, La),.040-in Invisacryl C (Great Lakes Orthodontics, Towanda, NY), and.040-in TR sheet material (Bay Dental Direct, Bay City, Mich). Twenty specimens were fabricated for each group. The specimens were vacuum thermoformed according to the manufacturers' recommendations and subjected to wear for 1000 cycles in a wear apparatus with steatite ceramic abraders. Depth of wear was determined by surface profilometry. The maximum peak-to-valley measurement was recorded for each specimen. Mean wear (SD) in microns was as follows: C+, 5.9 (2.4); Invisacryl C, 6.1 (2.6); and TR, 1.6 (0.9). One-way analysis of variance detected a significant difference between groups (P <.001). TR material, a hard polyethylene terephthalate glycol copolymer (PETG), demonstrated greater resistance to wear than did the other 2 materials, which were softer, polypropylene-based thermoplastics. There was no evidence to suggest a difference in mean wear between the 2 polypropylene-based materials (P >.05). PMID:12970663

Gardner, Gary D; Dunn, William J; Taloumis, Louis

2003-09-01

259

An analytical approach toward monitoring degradation in engineering thermoplastic materials used for electrical applications  

Microsoft Academic Search

Engineering thermoplastics are being used in a broad array of applications throughout the electrical industry. Polyester thermoplastics offer desirable electrical and mechanical properties; but when used in the wrong environments, they can be susceptible to hydrolysis. Size exclusion chromatography (SEC) can be used as an analytical tool for monitoring the degree of hydrolytic degradation occurring to engineering thermoplastic materials. By

Sam J. Ferrito; Thomas A. Edison

1996-01-01

260

Study on the Functionality of Nano-Precipitated Calcium Carbonate as Filler in Thermoplastics  

Microsoft Academic Search

This research aims to investigate the functionality of nano-precipitated calcium carbonate (NPCC) as filler in thermoplastic resins based on property enhancement. Three types of thermoplastics were used: polyethylene (PE), polypropylene (PP) and polyvinyl chloride (PVC). The resins were evaluated by determining the effect of different NPCC loading on the chemical structure, thermal and mechanical properties of thermoplastics. Results showed that

Blessie A. Basilia; Marian Elaine G. Panganiban; Archilles Allen V. C. Collado; Michael Oliver D. Pesigan; Persia Ada de Yro

2007-01-01

261

Modelling and simulation in polymer and composites processing  

Microsoft Academic Search

The general theme of this special section is modelling and simulation in polymer and composite processing. Composite processing in general involves reactive processing. During the last decade there have been numerous advances in modelling and simulation in both thermoplastic and reactive processing. This fact, coupled with the enormous advances in computing capability, has made Computer Aided Engineering (CAE) a reality.

José M Castro

2004-01-01

262

EDITORIAL: Modelling and simulation in polymer and composites processing  

Microsoft Academic Search

The general theme of this special section is modelling and simulation in polymer and composite processing. Composite processing in general involves reactive processing. During the last decade there have been numerous advances in modelling and simulation in both thermoplastic and reactive processing. This fact, coupled with the enormous advances in computing capability, has made Computer Aided Engineering (CAE) a reality.

Josè M. Castro

2004-01-01

263

Effects of carbon nanoparticles on properties of thermoset polymer systems  

Microsoft Academic Search

Polymer nanocomposites are novel materials in which at least one of the dimensions of the reinforcing material is on the order of 100 nm or less. While thermoplastic nanocomposites have been studied very widely, there are fewer studies concerning the effect of nanoparticles on thermoset systems. Low temperature cure thermoset systems are very important for many important applications. In this

Siva Subramanyam Movva

2010-01-01

264

Biodegradable, Elastic Shape-Memory Polymers for Potential Biomedical Applications  

Microsoft Academic Search

The introduction of biodegradable implant materials as well as minimally invasive surgical procedures in medicine has substantially improved health care within the past few decades. This report describes a group of degradable thermoplastic polymers that are able to change their shape after an increase in temperature. Their shape-memory capability enables bulky implants to be placed in the body through small

Andreas Lendlein; Robert Langer

2002-01-01

265

Preparation, characterization and formation mechanism of thermoplastic polyurethane nanostructures using solution wetting template.  

PubMed

Template wetting with polymer solutions has not been well understood up to now, and the formation mechanism of polymer nanostructures with this method is still to be revealed. In the present work, thermoplastic polyurethane (TPU) nanostructures were prepared by wetting cylindrical nanopores in an anodic aluminum oxide (AAO) membrane with TPU solution in dimethylformamide (DMF) followed by solvent evaporation. Both tubular structures and solid structures were simultaneously observed at four different concentrations of TPU solutions (i.e., 5, 7, 10, and 15 wt%) by a scanning electron microscope (SEM) and a transmission electron microscope (TEM). Furthermore, a transition from a tubular structure to a solid structure was also found at a higher concentration of TPU solution (15 wt%). It is speculated that the top part of the single nanostructure is tubular, and the lower part is solid. A "capillary wetting-evaporation-deposition" mechanism is given to explain such a phenomenon. According to this mechanism, the higher polymer concentration, the larger amount of solution, and the smaller pore size are believed to be beneficial for the formation of solid structures. PMID:22413371

Han, Guiquan; Liu, Yuhong; Luo, Jianbin; Lu, Xinchun; Dong, Ying

2011-11-01

266

Surface-Initiated ARGET ATRP and Characterization of Thermoplastic Elastomer Montomorillonite Composites  

NASA Astrophysics Data System (ADS)

Polymer nanocomposites, with enhanced properties as compared to their bulk polymer counterparts, are becoming more prominent in advanced material applications. Here we report the synthesis of poly(n-butyl acrylate-b-styrene) (PBA-b-PS) from the surface of functionalized montmorillonite clay via activators regenerated by electron transfer (ARGET) atom transfer radical polymerization (ATRP). The ARGET mechanism allows for a substantial reduction in the amount of transition metal catalyst required. It also exhibits potential for eventual scale-up and the industrial adoption of ATRP as a versatile method for producing polymers with well-defined compositions and functionalities. The composite materials resemble traditional thermoplastic elastomer triblock copolymers, with the clay platelets dividing the central, rubbery PBA block. We used SAXS, NMR, and TEM to characterize the composition and structure of the composites. The resulting material properties were measured by tensile testing, dynamic mechanical analysis, and TGA. We anticipate the composites to have exceptional barrier properties due to the high degree of clay dispersion, which may lead to applications as recyclable packaging materials.

Easley, Jeffrey; Beck, Amanda; Ellison, Christopher

2010-03-01

267

Polymer nanowrinkles with continuously tunable wavelengths.  

PubMed

This paper describes a parallel method to generate polymer nanowrinkles over large areas with wavelengths that were continuously tuned down to 30 nm. Reactive ion etching using fluorinated gases was used to chemically treat thermoplastic polystyrene films, which resulted in a stiff skin layer. Upon heating, the treated thermoplastic, microscale, and nanoscale wrinkles were formed. We used variable-angle spectroscopic ellipsometry to characterize the thickness of the skin layer; this thickness could then be used to predict and control the nanowrinkle wavelength. Because the properties of these nanotextured polymer surfaces can be tuned over a large range of wrinkle wavelengths, they are promising for a broad range of applications, especially those that require large-area and uniform surface patterning. PMID:23758140

Huntington, Mark D; Engel, Clifford J; Hryn, Alexander J; Odom, Teri W

2013-07-10

268

Thermoplastic Explosive Compositions on the Base of Hexanitrohexaazaisowurtzitane  

NASA Astrophysics Data System (ADS)

Hexanitrohexaazaisowurtzitane is an azostructural compound known as CL-20. We performed a series of experiments with CL-20 synthesized in Russia to evaluate the possibility to use it in pressed high explosive compositions. We used it in thermoplastic compositions both with an inert binder and energetic binder. The compositions were conventionally named CL-20 Icy and CL-20A. It was determined that the thermoplastic compositions had the most high detonation parameters and a level of sensitivity to mechanical effects acceptable to allow their processing. Their detonation characteristics were compared with that of some known foreign compositions based on CL-20.

Ilyin, V. P.; Smirnov, S. P.; Kolganov, E. V.; Pechenev, Yu. G.

2006-08-01

269

LARC-TPI: A multi-purpose thermoplastic polyimide  

NASA Technical Reports Server (NTRS)

A linear thermoplastic polyimide, LARC-TPI, was characterized and developed for a variety of high temperature applications. In its fully imidized form, this material can be used as an adhesive for bonding metals such as titanium, aluminum, copper, brass, and stainless steel. LARC-TPI was evaluated as a thermoplastic for bonding large pieces of polyimide film to produce flexible, 100 void-free laminates for flexible circuit applications. The development of LARC-TPI as a potential molding powder, composite matrix resin, high temperature film and fiber is also discussed.

St.clair, A. K.; St.clair, T. L.

1982-01-01

270

Assessment of aligned fiber reinforced thermoplastic composite sheet forming processes  

NASA Astrophysics Data System (ADS)

This paper presents an assessment of the current state of the art in thermoplastic composite sheet forming. The sheet forming processes discussed include: matched die forming, double diaphragm forming, hydroforming, rubber block pressing, and shaped rubber tool forming. A description of each technique is provided as well as a description of the equipment required and typical applications. The technical assessment defines the geometric and material form limitations and ranks each process in terms of size and geometric complexity. In addition, a discussion of the cost drivers associated with thermoplastic composite sheet forming and how they relate to each process is included.

Smiley, A. J.; Schmitt, T. E.

271

Thermoplastic veils as advanced modifiers for multifunctional fiber reinforced composites  

NASA Astrophysics Data System (ADS)

The present paper is focused on the development of a novel technique to obtain multifunctional fiber reinforced composites. The technique is based on the use of thermoplastic veils composed of nano and micro thermoplastic fibers which preferentially dissolve upon curing in the epoxy matrix. The technique allows to control the phase morphology in the inter- and intra-laminar region of the laminates. Moreover, the selective dissolution of the fibers allow to achieve tailored dispersion of different types of nanofillers in the composites to obtain a functional graded material.

Cicala, Gianluca; Latteri, Alberta; Mannino, Salvatore; Cozzo, Giulia; Ognibene, Giulia; Recca, Antonino

2014-05-01

272

Investigations into the mechanical and physical behavior of thermoplastic elastomers  

NASA Astrophysics Data System (ADS)

This thesis describes investigations into the physical and mechanical characteristics of two commercial thermoplastic elastomer (TPE) systems. Both systems studied exhibit elastomeric behavior similar to more traditional crosslinked elastomers; however, in these TPEs non-conventional polymer architectures and morphologies are used to produce their elastomeric behavior. The two TPEs of interest are ethylene-propylene random copolymers and dynamically vulcanized blends of ethylene-propylene-diene monomer (EPDM) and isotactic polypropylene (iPP). Very few studies have examined the mechanical behavior of these materials in terms of their composition and morphology. As such, the primary goal of this research is to both qualitatively and quantitatively understand the influence of composition and morphology on mechanical behavior. In additional very little information is available that compares their performance with that of crosslinked elastomers. As a result, the secondary goal is to qualitatively compare the mechanical responses of these TPEs with that of their more traditional counterparts. The ethylene-propylene copolymers studied have very high comonomer contents and exhibit slow crystallization kinetics. Their morphology consists of nanoscale crystallites embedded in an amorphous rubbery matrix. These crystallites act as physical crosslinks that allow for elasticity. Slow crystallization causes subsequent changes in mechanical behavior that take place over days and even weeks. Physical responses (e.g., density, crystallization kinetics, and crystal structure) of five copolymer compositions are investigated. Mechanical responses (e.g., stiffness, ductility, yielding, and reversibility) are also examined. Finally, the influence of morphology on deformation is studied using in situ analytical techniques. The EPDM/iPP blends are dynamically vulcanized which produces a complex morphology consisting of chemically crosslinked EPDM domains embedded within a semicrystalline iPP matrix. Six compositions are investigated as a function of three parameters: major volume fraction, iPP molecular weight, and EPDM cure state. The influence of these parameters on morphology and resulting mechanical behavior is examined. This work culminates in the development of a morphological model to describe the steady-state reversibility of these EPDM/iPP blends. The model is then evaluated in terms of composition and cure state.

Wright, Kathryn Janelle

273

Continuation of tailored composite structures of ordered staple thermoplastic material  

NASA Technical Reports Server (NTRS)

The search for the cost effective composite structure has motivated the investigation of several approaches to develop composite structure from innovative material forms. Among the promising approaches is the conversion of a planar sheet to components of complex curvature through sheet forming or stretch forming. In both cases, the potential for material stretch in the fiber direction appears to offer a clear advantage in formability over continuous fiber systems. A framework was established which allows the simulation of the anisotropic mechanisms of deformation of long discontinuous fiber laminates wherein the matrix phase is a viscous fluid. Predictions for the effective viscosities of a hyper-anisotropic medium consisting of collimated, discontinuous fibers suspended in viscous matrix were extended to capture the characteristics of typical polymers including non-Newtonian behavior and temperature dependence. In addition, the influence of fiber misorientation was also modeled by compliance averaging to determine ensemble properties for a given orientation distribution. A design tool is presented for predicting the effect of material heterogeneity on the performance of curved composite beams such as those used in aircraft fuselage structures. Material heterogeneity can be induced during manufacturing processes such as sheet forming and stretch forming of thermoplastic composites. This heterogeneity can be introduced in the form of fiber realignment and spreading during the manufacturing process causing radial and tangential gradients in material properties. Two analysis procedures are used to solve the beam problems. The first method uses separate two-dimensional elasticity solutions for the stresses in the flange and web sections of the beam. The separate solutions are coupled by requiring that forces and displacements match section boundaries. The second method uses an approximate Rayleigh-Ritz technique to find the solutions for more complex beams. Analyses are performed for curved beams of various cross-sections loaded in pure bending and with a uniform distributed load. Preliminary results show that the geometry of the beam dictates the effect of heterogeneity on performance. The role of heterogeneity is larger in beams with a small average radius-to-depth ration, R/t, where R is the average radius of the beam and t is the difference between the inside and outside radii. Results of the anlysis are in the form of stresses and displacements and are compared to both mechanics of materials and numerical solutions obtained using finite element analysis.

Santare, Michael H.; Pipes, R. Byron

1992-01-01

274

Covalent attachment of a three-dimensionally printed thermoplast to a gelatin hydrogel for mechanically enhanced cartilage constructs.  

PubMed

Hydrogels can provide a suitable environment for tissue formation by embedded cells, which makes them suitable for applications in regenerative medicine. However, hydrogels possess only limited mechanical strength, and must therefore be reinforced for applications in load-bearing conditions. In most approaches the reinforcing component and the hydrogel network have poor interactions and the synergetic effect of both materials on the mechanical properties is not effective. Therefore, in the present study, a thermoplastic polymer blend of poly(hydroxymethylglycolide-co-?-caprolactone)/poly(?-caprolactone) (pHMGCL/PCL) was functionalized with methacrylate groups (pMHMGCL/PCL) and covalently grafted to gelatin methacrylamide (gelMA) hydrogel through photopolymerization. The grafting resulted in an at least fivefold increase in interface-binding strength between the hydrogel and the thermoplastic polymer material. GelMA constructs were reinforced with three-dimensionally printed pHMGCL/PCL and pMHMGCL/PCL scaffolds and tested in a model for a focal articular cartilage defect. In this model, covalent bonds at the interface of the two materials resulted in constructs with an improved resistance to repeated axial and rotational forces. Moreover, chondrocytes embedded within the constructs were able to form cartilage-specific matrix both in vitro and in vivo. Thus, by grafting the interface of different materials, stronger hybrid cartilage constructs can be engineered. PMID:24590160

Boere, Kristel W M; Visser, Jetze; Seyednejad, Hajar; Rahimian, Sima; Gawlitta, Debby; van Steenbergen, Mies J; Dhert, Wouter J A; Hennink, Wim E; Vermonden, Tina; Malda, Jos

2014-06-01

275

Design of bioabsorbable, amorphous polymer networks and composites  

Microsoft Academic Search

Amorphous, crosslinked, bioabsorbable polymers have been developed as an alternative to conventional linear, semi-crystalline thermoplastic bioabsorbable polymers, and as matrix resins for totally bioabsorbable composites. Bioabsorbable composites have been fabricated, consisting of poly(glycolic acid) surgical mesh embedded in polyester and polyester-urethane based matrices. Low-molecular weight precursors used in the matrices of the composites were based on D, L-lactide and [epsilon]-caprolactone

Wiggins

1992-01-01

276

Microinjection moulding of polymer microfluidic devices  

Microsoft Academic Search

Microfluidic devices have several applications in different fields, such as chemistry, medicine and biotechnology. Many research\\u000a activities are currently investigating the manufacturing of integrated microfluidic devices on a mass-production scale with\\u000a relatively low costs. This is especially important for applications where disposable devices are used for medical analysis.\\u000a Micromoulding of thermoplastic polymers is a developing process with great potential for

Usama M. Attia; Silvia Marson; Jeffrey R. Alcock

2009-01-01

277

Mechanical Behaviour of Particle Filled Thermoplastics.  

National Technical Information Service (NTIS)

An investigation is reported of the mechanical behavior of composite materials under load. The composites consisted of a dispersion of inorganic fillers in a polymer matrix. A model is described that makes it possible to calculate the stress at which the ...

P. H. T. Vollenberg

1987-01-01

278

A new synthetic route to a family of non-classical addition-type thermoplastics. I - Concept and demonstration  

NASA Technical Reports Server (NTRS)

A synthesis scheme was developed for a host of nonclassical addition-type thermoplastics (ATT) that can be cured by an addition reaction, leading to a linear polymer structure. The synthesis involves the reaction of an acetylene-terminated prepolymer with either a bismaleimide (BMI) or a biscitraconimide. A new polymer, designated LaRC-RP80, synthesized using this scheme, was found to exhibit several significantly improved properties over the commercial BMI, Kerimid 601, including an eight-fold increase in toughness while maintaining a high Tg, a higher (by 167 C) heat stability, and a 50-percent increase in moisture resistance. In addition, LaRC-RP80 has good hot/wet lap shear strength and processes easily at 288 C without voids in the finished product.

Pater, Ruth H.

1988-01-01

279

Tough, Microcracking-Resistant, High-Temperature Polymer  

NASA Technical Reports Server (NTRS)

Simultaneous synthesis from thermosetting and thermoplastic components yields polyimide with outstanding properties. Involves process in which one polymer cross-linked in immediate presence of other, undergoing simultaneous linear chain extension. New material, LaRC-RP40 synthesized from high-temperature thermosetting imide prepolymer and from thermoplastic monomer. Three significantly improved properties: toughness, resistance to microcracking, and glass-transition temperature. Shows promise as high-temperature matrix resin for variety of components of aircraft engines and for use in other aerospace structures.

Pater, Ruth H.; Razon, Pert; Smith, Ricky; Working, Dennis; Chang, Alice; Gerber, Margaret

1990-01-01

280

Dual-polymer laminates for corrosion-resistant equipment  

SciTech Connect

This paper describes combining a thermoplastic liner with a conventional fiberglass-reinforced plastic (FRP) exterior to yield a system that offers excellent chemical resistance and strength properties. Tanks, equipment, and piping made this way are often cheaper than those of competing alloys. The dual-polymer laminates provide a new approach to resisting attack by severe chemical environments and storing highly purified chemicals without contamination. Construction is similar to lining a steel vessel with a thermoplastic; but, with dual laminates, the liner can be build first, with structural layers added later.

Rolston, J.A.

1985-01-07

281

On-line consolidation of thermoplastic composites  

NASA Astrophysics Data System (ADS)

An on-line consolidation system, which includes a computer-controlled filament winding machine and a consolidation head assembly, has been designed and constructed to fabricate composite parts from thermoplastic towpregs. A statistical approach was used to determine the significant processing parameters and their effect on the mechanical and physical properties of composite cylinders fabricated by on-line consolidation. A central composite experimental design was used to select the processing conditions for manufacturing the composite cylinders. The thickness, density, void content, degree of crystallinity and interlaminar shear strength (ILSS) were measured for each composite cylinder. Micrographs showed that complete intimate contact and uniform fiber-matrix distribution were achieved. The degree of crystallinity of the cylinders was found to be in the range of 25-30%. Under optimum processing conditions, an ILSS of 58 MPa and a void content of <1% were achieved for APC-2 (PEEK/Carbon fiber) composite cylinders. An in-situ measurement system which uses a slip ring assembly and a computer data acquisition system was developed to obtain temperature data during winding. Composite cylinders were manufactured with eight K-type thermocouples installed in various locations inside the cylinder. The temperature distribution inside the composite cylinder during winding was measured for different processing conditions. ABAQUS finite element models of the different processes that occur during on-line consolidation were constructed. The first model was used to determine the convective heat transfer coefficient for the hot-air heat source. A convective heat transfer coefficient of 260 w/msp{2°}K was obtained by matching the calculated temperature history to the in-situ measurement data. To predict temperature distribution during winding an ABAQUS winding simulation model was developed. The winding speed was modeled by incrementally moving the convective boundary conditions around the outer surface of the composite cylinder. A towpreg heating model was constructed to predict the temperature distribution on the cross section of the incoming towpreg. For the process-induced thermal stresses analysis, a thermoelastic finite element model was constructed. Using the temperature history obtained from thermal analysis as the initial conditions, the thermal stresses during winding and cooling were investigated.

Shih, Po-Jen

282

Qualification testing of engineering thermoplastics for electrical distribution applications  

Microsoft Academic Search

Engineering thermoplastic materials are continually being incorporated as a cost competitive alternative for improving the performance characteristics of electrical distribution equipment and their accessories. Proper utilization of any material requires a thorough understanding of not only the inherent properties of the material, but also how it will react under various environments over a prolonged period of time. The material selection

S. J. Ferrito; Thomas A. Edison

2002-01-01

283

Plastic-On-Plastic Tribological Properties of Thermoplastic Composites  

Microsoft Academic Search

A comprehensive study of the wear factor and coef ficient of friction for a series of fiber reinforced and internally lubricated thermoplastic composites including glass fiber and carbon fiber reinforcements and silicone fluid and PTFE lubri cants. Polycarbonate, nylon 6\\/6, PPS, acetal, and PBT resins were studied in the modified dirll press wear washer test method. Wear factor and coefficient

Mark P. Wolverton; John E. Theberge

1981-01-01

284

Material, process, and product design of thermoplastic composite materials  

Microsoft Academic Search

Thermoplastic composites made of polypropylene (PP) and E-glass fibers were investigated experimentally as well as theoretically for two new classes of product designs. The first application was for reinforcement of wood. Commingled PP\\/glass yarn was consolidated and bonded on wood panel using a tie layer. The processing parameters, including temperature, pressure, heating time, cooling time, bonding strength, and bending strength

Heming Dai

2001-01-01

285

Hybrid yarn for thermoplastic fiber composites. Summary of technical results.  

National Technical Information Service (NTIS)

The program, which started at the 15th of June 1994 and expired at the 31st of December 1997, was a framework program under the Danish Materials Technology Program, MUP2. A new type of hybrid yarn for production of fiber composites with thermoplastic matr...

A. Lystrup

1998-01-01

286

Development and evaluation of thermoplastic street maintenance material  

NASA Technical Reports Server (NTRS)

An all-weather permanent street patching material was investigated for flexible and rigid pavements. The economic, operational, and material requirements are discussed along with the results of field tests with various mixtures of EVA resins and asphalt. Cost analyses for thermoplastic patching methods are included.

Siemens, W. D.

1973-01-01

287

Adhesion kinetics of nitrifying bacteria on various thermoplastic supports  

Microsoft Academic Search

The adhesion kinetics of nitrifying bacteria on various thermoplastic supports (polyethylene, polypropylene, polystyrene) were investigated by static adhesion tests. A simple kinetic model was presented that described the initial accumulation process of nitrifying bacteria on the supports. This model was then employed to study the effects of various factors on the adhesion kinetics of nitrifying bacteria. The findings indicated that

Yu Liu

1995-01-01

288

Breathable Protective Clothing with Hydrophilic Thermoplastic Elastomer Membrane Films  

Microsoft Academic Search

Thermoplastic elastomers offer many interesting properties. This paper introduces the material class of TPE and describes their application in breathable laminates for garment improvement, especially protection garments. The most important production and manufacturing processes will be discussed and the relevant properties will be presented. Special attention will be given to the TPU as an important raw material for breathable TPE-films.

Ralf Schledjewski; Dirk Schultze; Klaus-Peter Imbach

1997-01-01

289

Functional patterns obtained by nanoimprinting lithography and subsequent growth of polymer brushes  

Microsoft Academic Search

In this work the growth of polymer brushes was combined with nanoimprint lithography (NIL) in order to obtain new functional nanopatterns. First, a functional thermoplastic methacrylic copolymer poly(methyl methacrylate-co-2-bromoisobutyryl-oxy-ethyl methacrylate) was synthesized. This copolymer was successfully patterned by NIL using a silicon stamp at 160 °C and 60 bar. Next, hydrophilic polymer brushes based on poly(3-sulfopropylmethacrylate) and hydrophobic polymer brushes

A. Genua; J. A. Alduncín; J. A. Pomposo; H. Grande; N. Kehagias; V. Reboud; C. Sotomayor; I. Mondragon; D. Mecerreyes

2007-01-01

290

Nonlinear rheology and strain recovery of short chain branched polyolefin elastomers and thermoplastic olefin blends  

NASA Astrophysics Data System (ADS)

Polyolefin elastomers are random copolymers having a polyethylene backbone with the higher olefinic comonomer incorporated as short-chain branches. These random copolymers are widely used as polymer modifiers for thermoplastic materials such as polypropylenes, resulting in thermoplastic olefin (TPO) blends. This thesis addresses the nonlinear rheological behavior of the elastomers and then of the TPO blends. The effects of varying short chain branch density (SCB) on the melt rheology of three ethylene-octene random copolymers have been investigated. In particular, the strain-hardening behavior in extensional flow and strain recovery following nonlinear shear creep has been evaluated. The zero-shear viscosity followed trends in the backbone molecular weight closely. While the three copolymers were indistinguishable in linear viscoelastic creep and recovery, recovery following nonlinear shear creep decreased progressively with increasing SCB density. This reveals that the extent of rapid chain equilibration that occurs over Rouse time scales at higher strains was progressively lower with increasing SCB density. Strain hardening in uniaxial extensional flow was observed for all three copolymers. At strain rates below the primitive chain equilibration rates, strain hardening increases progressively with increasing SCB density. At higher rates, upon onset of primitive chain stretch, the strain hardening behavior for the three melts merges. Two thermoplastic olefin (TPO) blends were characterized in the context of injection molding; the surface morphology of injection molded tensile bars with these materials showed surface defects or flow marks to different extents. The flow marks were traced to different degrees of strain recovery in the dispersed phases of the two blends. This recovery occurred over injection molding timescales of the order of a few seconds. Strain recovery after shear creep was higher in the blend that displayed more severe flow marks in injection molding; the corresponding elastomer by itself also showed a greater extent of creep recovery. The quick strain recovery in the elastomer must be associated with elastic stresses rather than interfacial tension. A new experimental apparatus was assembled to study strain recovery after elongation of a model elastomer suspended in a less viscoelastic medium at room temperature. Small drops of well-characterized elastomers suspended in a matrix fluid of lower viscosity and elasticity, are stretched rapidly without wall effects in this setup; the stretch ratio of the drops is then recorded over time. Preliminary results confirm significant recovery over a few seconds. Exploration of the full range of parameters with this setup is left for future work.

Patham, Bhaskar

291

Modification of wood fiber with thermoplastics by reactive steam-explosion processing  

NASA Astrophysics Data System (ADS)

For the first time, a novel processing method of co-refining wood and polyolefin (PO) by steam-explosion was scientifically explored for wood-thermoplastic composites without a coupling agent. Traditional studies have addressed the improvement of adhesion between components of wood thermoplastic composites through the use of coupling agents such as maleated PO. The objective of this study was to increase adhesion between wood and PO through reactive processing conditions of steam-explosion. PO characteristics, such as type (polyethylene or polypropylene), form (pellet, fiber, or powder) and melt viscosity were studied along with oxygen gas content of the steam-explosion reactor vessel. Modification of co-processed wood fiber was characterized in four studies: microscopy analysis of dispersion of PO with wood fiber, sorption properties of co-processed material, chemical analysis of fractionated components, and morphological investigation of co-processed material. Two additional studies are listed in the appendices that relate to adsorption of amphiphilic polymers to the cellulose fiber surface, which is one hypothesis of fiber surface modification by co-steam-explosion. Microscopy studies revealed that PO melt viscosity was found to influence the degree of dispersion and uniformity of the steam-exploded material. The hygroscopic nature of the co-processed fiber declined as shown by sorption isotherm data. Furthermore, a water vapor kinetics study found that all co-refined material had increased initial diffusion coefficients compared to the control fiber. Chemical changes in fractionated components were PO-type dependent. Lignin extracted from co-processed wood and polyethylene showed PO enrichment determined from an increase of methylene stretching in the Fourier Transform infrared subtraction spectra, while lignin from co-processed wood and polypropylene did not. Additionally, extracted PO showed indirect signs of oxidation as reflected by fluorescence studies. Solid state nuclear magnetic resonance spectroscopy revealed a number of differences in the co-processed materials such as increased cellulose crystallinity, new covalent linkages and an alternative distribution of components on the nanoscale reflected in the T1rho relaxation parameter. Steam-explosion was shown to modify wood fiber through the addition of "non-reactive" polyolefins without the need for coupling agents. In light of these findings, co-refining by steam-explosion should be viewed as a new reactive processing method for wood thermoplastic composites.

Renneckar, Scott H.

292

Influence of surface roughness and contact load on friction coefficient and scratch behavior of thermoplastic olefins  

NASA Astrophysics Data System (ADS)

To study the effects of surface roughness and contact load on the friction behavior and scratch resistance of polymers, a set of model thermoplastic olefins (TPO) systems with various surface roughness ( Ra) levels were prepared and evaluated. It is found that a higher Ra corresponds to a lower surface friction coefficient ( ?s). At each level of Ra, ?s gets larger as contact load increases, with a greater increase in ?s as Ra level increases. It is also observed that with increasing contact load and increasing Ra, the ?s tend to level off. In evaluating TPO scratch resistance, a lower ?s would delay the onset of ductile drawing-induced fish-scale surface deformation feature, thereby raising the load required to cause scratch visibility. However, as the contact load is further increased, the ?s evolves to become scratch coefficient of friction (SCOF) as significant sub-surface deformation and tip penetration occur and material displacement begins, i.e., ploughing. No dependence of Ra and ?s on the critical load for the onset of ploughing is observed. In this work, the distinction between ?s and SCOF will be illustrated. Approaches for improving scratch resistance of polymers via control of Ra are also discussed.

Jiang, Han; Browning, Robert; Fincher, Jason; Gasbarro, Anthony; Jones, Scooter; Sue, Hung-Jue

2008-05-01

293

Foam injection molding of thermoplastic elastomers: Blowing agents, foaming process and characterization of structural foams  

NASA Astrophysics Data System (ADS)

Polymer foams play an important role caused by the steadily increasing demand to light weight design. In case of soft polymers, like thermoplastic elastomers (TPE), the haptic feeling of the surface is affected by the inner foam structure. Foam injection molding of TPEs leads to so called structural foam, consisting of two compact skin layers and a cellular core. The properties of soft structural foams like soft-touch, elastic and plastic behavior are affected by the resulting foam structure, e.g. thickness of the compact skins and the foam core or density. This inner structure can considerably be influenced by different processing parameters and the chosen blowing agent. This paper is focused on the selection and characterization of suitable blowing agents for foam injection molding of a TPE-blend. The aim was a high density reduction and a decent inner structure. Therefore DSC and TGA measurements were performed on different blowing agents to find out which one is appropriate for the used TPE. Moreover a new analyzing method for the description of processing characteristics by temperature dependent expansion measurements was developed. After choosing suitable blowing agents structural foams were molded with different types of blowing agents and combinations and with the breathing mold technology in order to get lower densities. The foam structure was analyzed to show the influence of the different blowing agents and combinations. Finally compression tests were performed to estimate the influence of the used blowing agent and the density reduction on the compression modulus.

Ries, S.; Spoerrer, A.; Altstaedt, V.

2014-05-01

294

The crystallization of tough thermoplastic resins in the presence of carbon fibers  

NASA Technical Reports Server (NTRS)

The presence of carbon fibers increased the crystallization rates of both PEEK and PPS thermoplastic polymers. The effect was most pronounced at higher crystallization temperatures. Isothermal crystallization rates were analyzed by applying classical phenomenological nucleation theory. Unusually high values of the so-called Avrami exponent were found for neat PEEK. Isothermal crystallization of PEEK and PPS polymers produced crystalline samples having a wide variety of melting temperatures. The melting as observed by differential scanning calorimetry occurred as dual endotherms which were called primary (higher temperature) and secondary melting peaks. Each primary peak accounted for most of the crystallinity present. The secondary peaks represented the melting of crystallites formed later than those attributable to the primary endotherms. The presence of carbon fibers increased the thermal stability of both PEEK and PPS crystallites as manifested by higher temperatures for the primary melting peaks. This may be attributable to increased crystallite size, greater crystallite perfection, and/or favorable modification of the crystallite interface. Over the range studied, crystallization temperature strongly influenced the positions of the secondary peaks but not the primary peaks.

Theil, Michael H.

1988-01-01

295

Impact of Nanotube Addition on Stress Recovery of Thermoplastic Elastomer Nanocomposites.  

NASA Astrophysics Data System (ADS)

Recent extension of polymer nanocomposite concepts to shape memory polymers has demonstrated potential to substantially improve recovery stress and provide novel triggering options, while still maintaining large deformations. One such example is multi wall carbon nanotubes (MWCNT)s in thermoplastic polyurethane (PU), where the MWCNTs increase modulus and modify strain induced crystallization leading to improved strain set and recovery force relative to unfilled PU as well as conventionally-filled PU. The impact of MWCNT alignment on the stress recovery rate depends on MWCNT concentration and the procedure used to `set' the deformation. Differences in response time upon shape recovery are observed whether the nanocomposites are `set' above the melting point of soft segment crystallites or at room temperature (RT). A detailed dynamic mechanical analysis protocol reveals that recovery rate and shape fixity are increasing as a function of MWCNT volume fraction and that RT processed nanocomposites show overall superior results. Recovery times can be described with a modification of the Kohlrausch-Williams-Watt equation, indicating a contribution from elasticity of the carbon nanotubes or chain scission of the matrix PU.

Powers, Daniel; Alexander, Max; Vaia, Richard; Arlen, Michael; Koerner, Hilmar

2006-03-01

296

Synthesis of nano cellulose fibers and effect on thermoplastics starch based films.  

PubMed

Starch based films limit their application due to highly hydrophilic nature and poor mechanical properties. This problem was sought to be overcome by forming a nanocomposite of Thermoplastic starch (TPS) and Nano-Cellulose fibers (NCF). NCF was successfully synthesised from short stable cotton fibres by a chemo-mechanical process. TPS/NCF composite films were prepared by solution casting method, and their characterizations were done in terms of differential scanning calorimeter (DSC), morphology (SEM), water vapor permeability (WVTR), oxygen transmission rate (OTR), X-ray diffractograms, light transmittance and tensile properties. At very low concentration of NCF filled TPS composite film showed improvement in properties. The 0.4wt% NCF loaded TPS films showed 46.10% improved tensile strength than by base polymer film, beyond that 0.5wt% concentration tensile strength starts to deteriorate. WVTR and OTR results showed improved water vapor barrier property of TPS matrix. The DSC thermograms of TPS and composite films did not show any significant effect on the melting point of composite film to the base polymer TPS. PMID:24750616

Savadekar, N R; Mhaske, S T

2012-06-01

297

Semi-interpenetrating polymer network for tougher and more microcracking resistant high temperature polymers  

NASA Technical Reports Server (NTRS)

This invention is a semi-interpenetrating polymer network which includes a high performance thermosetting polyimide having a nadic end group acting as a crosslinking site and a high performance linear thermoplastic polyimide. An improved high temperature matrix resin is provided which is capable of performing at 316 C in air for several hundreds of hours. This resin has significantly improved toughness and microcracking resistance, excellent processability and mechanical performance, and cost effectiveness.

Pater, Ruth H. (inventor)

1992-01-01

298

Controlling the wettability of hierarchically structured thermoplastics.  

PubMed

Surfaces play an important role in defining the properties of materials, controlling wetting, adsorption, or desorption of biomolecules, and sealing/bonding of different materials. We have combined microscale features with plasma-etched nanoscale roughness and chemical modification to tailor the wettability of the substrates. Cyclic olefin polymers and copolymers (COPs/COCs) were processed to make a range of surfaces with controlled superhydrophobic or -hydrophilic properties. The hydrophobic properties of the polymers were increased by the introduction of microstructures of varying geometry and spacing through hot embossing. The COC/COP substrates were functionalized by plasma activation in O(2), CF(4), and a mixture of both gases. The plasma etching introduces nanoscale roughness and also chemically modifies the surface, creating either highly hydrophilic or highly hydrophobic (contact angle >150°) surfaces depending on the gas mixture. The influence of geometry and chemistries was characterized by atomic force microscopy, contact angle measurements, and X-ray photoelectron spectroscopy. Measurements of the contact angle and contact angle hysteresis demonstrated long-term stability of the superhydrophobic/superhydrophilic characteristics (>6 months). PMID:22043942

Cortese, Barbara; Morgan, Hywel

2012-01-10

299

Interfacial strength development in thermoplastic resins and fiber-reinforced thermoplastic composites  

NASA Technical Reports Server (NTRS)

An experimental program to develop test methods to be used to characterize interfacial (autohesive) strength development in polysulfone thermoplastic resin and graphite-polysulfone prepreg during processing is reported. Two test methods were used to examine interfacial strength development in neat resin samples. These included an interfacial tension test and a compact tension (CT) fracture toughness test. The interfacial tensile test proved to be very difficult to perform with a considerable amount of data scatter. Thus, the interfacial test was discarded in favor of the fracture toughness test. Interfacial strength development was observed by measuring the refracture toughness of precracked compact tension specimens that were rehealed at a given temperature and contact time. The measured refracture toughness was correlated with temperature and contact time. Interfacial strength development in graphite-polysulfone unidirectional composites was measured using a double cantilever beam (DCB) interlaminar fracture toughness test. The critical strain energy release rate of refractured composite specimens was measured as a function of healing temperature and contact time.

Howes, Jeremy C.; Loos, Alfred C.

1987-01-01

300

[Cell proliferation and cellular activity of primary cell cultures of the oral cavity after cell seeding on the surface of a degradable, thermoplastic block copolymer].  

PubMed

Using standard cell biological and biochemical methods we were able to test the ability of a degradable, thermoplastic block copolymer to support the adhesion, proliferation, and the cellular activity of primary cell cultures of the oral cavity in vitro. The delicate balance between a group of endogenous enzymes, Matrix Metalloproteinases (MMPs), and their inhibitors (Tissue Inhibitor of MMPs, TIMPs) have a decisive function in the remodeling of the extracellular matrix during processes like wound healing or the integration of biomaterials in surrounding tissues after implantation. Recently developed, biodegradable thermoplastic elastomers with shape-memory properties may be the key to develop new therapeutical options in head and neck surgery. Primary cell cultures of the oral cavity of Sprague-Dawley rats were seeded on the surface of a thermoplastic block copolymer and on a polystyrene surface as control. Conditioned media of the primary cells were analyzed for MMPs and TIMPs after different periods of cell growth. The MMP and TIMP expression was analysed by zymography and a radiometric enzyme assay. No statistically significant differences in the appearance and the kinetic of MMP-1, MMP-2, MMP-9 and TIMPs were detected between cells grown on the polymer surface compared to the control. An appropriate understanding of the molecular processes that regulate cellular growth and integration of a biomaterial in surrounding tissue is the requirement for an optimal adaptation of biodegradable, polymeric biomaterials to the physiological, anatomical, and surgical conditions in vivo to develop new therapeutic options in otolaryngology and head and neck surgery. PMID:15884705

Rickert, D; Lendlein, A; Kelch, S; Franke, R P; Moses, M A

2005-04-01

301

Method for shaping sheet thermoplastic and the like  

NASA Technical Reports Server (NTRS)

Processes and apparati for shaping sheet glass or thermoplastic materials use force from a layer of a flowing fluid, such as air, between the sheet and a mandrel at close to the softening temperature of the thermoplastic. The shape is preserved by cooling. The shape of the air bearing mandrel and the pressure distribution of the fluid contribute to the final shape. A process can be conducted on one or two surfaces such that the force from the air layer is on one or two surfaces of the sheet. The gap size between the sheet and mandrel determines the pressure profile in the gap, which also determines the final sheet shape. In general, smaller gaps lead to larger viscous forces. The pressure profile depends on the shape of the mandrel, the size of the fluid gap and the sheet and the fluid supply pressure.

Akilian, Mireille K. (Inventor); Schattenburg, Mark L. (Inventor)

2011-01-01

302

Toroid Joining Gun. [thermoplastic welding system using induction heating  

NASA Technical Reports Server (NTRS)

The Toroid Joining Gun is a low cost, self-contained, portable low powered (100-400 watts) thermoplastic welding system developed at Langley Research Center for joining plastic and composite parts using an induction heating technique. The device developed for use in the fabrication of large space sructures (LSST Program) can be used in any atmosphere or in a vacuum. Components can be joined in situ, whether on earth or on a space platform. The expanded application of this welding gun is in the joining of thermoplastic composites, thermosetting composites, metals, and combinations of these materials. Its low-power requirements, light weight, rapid response, low cost, portability, and effective joining make it a candidate for solving many varied and unique bonding tasks.

Buckley, J. D.; Fox, R. L.; Swaim, R J.

1985-01-01

303

Pultrusion with thermoplastics for the fabrication of structures in space  

NASA Technical Reports Server (NTRS)

The use of the pultrusion method to produce structures in space is proposed. This technique is based on transporting materials in coils or bundles and fabricating the structures in space. Two methods for thermoplastic impregnation of advanced composite are described. The properties of three pultruded thermoplastic matrix materials, polyphenylene sulfide, polyetherimide (PEI), and polyetheretherketone (PEEK) are discussed and evaluated. It is observed that the pultrusions containing PEI and PEEK reveal post-fabrication potential of lightweight, high strength advanced composites and this method of fabrication produces strength values comparable to those of conventional techniques. Earth-based and space-based planetary shelter models are developed and compared. It is noted that cargo storage volume is dependent on a combination of profiles, packaging, and manufacturing methods.

Wilson, Maywood L.; Macconochie, Ian O.; Johnson, Gary S.

1988-01-01

304

Characterization of poly(methyl methacrylate) and thermoplastic polyurethane-carbon nanofiber composites produced by chaotic mixing  

NASA Astrophysics Data System (ADS)

Chaotic mixing is a novel mixing technique offering high mixing efficiency even under mild shearing conditions. In this work, chaotic mixing was used to prepare composites of carbon nanofibers and two thermoplastic polymers---poly (methyl methacrylate) (PMMA) and thermoplastic polyurethanes (TPU)---and their electrical, mechanical, and thermal properties were evaluated. The TPU systems were based on the reaction products of 4,4'-diphenylmethane diisocyanate, (MDI), soft segment polyol, and 1,4-butanediol as chain extender. Soft segment polyols in the form of poly(propylene glycol) (PPG), and poly(epsilon-caprolactone)diol (PCL) were used to obtain respectively amorphous and crystalline soft segments. Of these, the TPU system based on crystalline soft segment exhibited shape memory effects. Both, as-received untreated carbon nanofibers (CNF) with a very low amount of atomic oxygen on the surface, and oxidized carbon nanofibers (CNFOX) were used. CNFOX was also modified by esterifying with PPG to produce a third type of carbon nanofiber named CNFOL. These carbon nanofibers were examined by X-ray photoelectron spectroscopy to determine the elemental composition of the surface, and by scanning electron microscopy and transmission electron microscopy to determine the surface morphology.

Jiminez, Guillermo A.

305

Joining of aluminum and long fiber thermoplastic (LFT) composites  

NASA Astrophysics Data System (ADS)

Metal/polymer joints are used in variety of areas: aerospace, automotive, prosthetic devices, electronic packaging, etc. The present study involves a tailcone, which is currently made of aluminum and a new design will involve a joint between aluminum and long fiber thermoplastic (LFT) composite. The new tailcones were processed by insert molding, also called as extrusion-compression molding. Finite element (FE) models were used to obtain a temperature profile during cooling of tailcone from processing and to estimate thermal stresses generated. Experimental verification of the temperature profile was obtained by IR thermography. It was observed that the LFT part of the tailcone cooled faster than aluminum. During the cooling of the tailcone, the aluminum insert acted as a heat sink because of the large difference between the thermal conductivities of aluminum and the LFT composite. Thermal stresses computed were 2.5 MPa and 12 MPa in the case of beaded and threaded insert tailcones, respectively. Static pullout tests were done to obtain an insight into the failure mechanisms of the joint between aluminum and LFT composite. Both the tailcone configurations, with beaded and threaded inserts, showed about the same average peak load, 96 kN. Radiographic and metallographic studies showed that the damage at the interface between aluminum and LFT composite occurred in the form of microcracks, followed by complete separation normal to the stress axis. The tailcones housed in projectiles were test fired and it was found that the HBTs disintegrated immediately after they came out of the barrel. A new design was proposed to overcome the drawbacks of the HBTs, called filled-back tailcone (FBT). Static pullout tests on FBTs showed no failure of the tailcones, which was in accord with the test firing where tailcone did not fail. The study of aluminum/LFT composite interfaces was extended into the realm of laminated composites. Laminated composites were made in the form of alternate layers between LFT composite and metal (called as LMLs) such as aluminum by compression molding. Interlaminar shear strength of the laminates was determined by short beam three-point bend tests. It was found that the strength depends on the surface quality of the aluminum. ILSS in the case of mean roughness (Ra) 3.3 mum was 34.5 MPa, whereas 24 MPa in the case of mean roughness of 0.4 mum. Tensile test results showed that average Young's modulus and tensile strength of the laminate were 44.8 GPa and 244 MPa, respectively. Rule-of-mixtures predictions matched closely with the experimental results. Low velocity impact (LVI) tests showed that the specific perforation energy of the LMLs was significantly higher (7.1 J/kg m-2) than that of LFT composite (1.2 J/kg m-2). This new type of hybrid composite, LML, is quite promising for a variety of applications in automotive as well as aerospace industries.

Kulkarni, Rahul R.

306

The compression of wood\\/thermoplastic fiber mats during consolidation  

Microsoft Academic Search

Secondary processing of non-woven wood and wood\\/thermoplastic fiber mats is generally performed using compression molding, where heated platens or dies form the final product. Although the study and use of wood–fiber composites is widespread, few research efforts have explicitly described the fundamentals of mat consolidation. In contrast, the wood composite literature has prolifically addressed the compression of wood-strand composites. Models

Karl R. Englund; Michael P. Wolcott; John C. Hermanson

2004-01-01

307

RESISTANCE WELDING OF THERMOPLASTIC COMPOSITE SKIN\\/STRINGER SPECIMENS  

Microsoft Academic Search

An investigation of resistance welding of thermoplastic composites skin\\/stringer specimens is presented. Skin\\/stringer configurations with square-ended and 20° taper-ended flanges were resistance-welded using a metal mesh heating element. The skin and stringer laminates were made of 16-ply APC-2\\/AS4 PEEK\\/carbon fiber composite. The objective of this work was to study the feasibility of resistance welding to assemble aerospace structures with non-uniform

Martine Dubé; Pascal Hubert; Ali Yousefpour; Johanne Denault

308

Thermostable Insulating Thermoplastic Elastomers from Rubber Polycarbonate Blends  

Microsoft Academic Search

Thermoplastic elastomeric blends based on polycarbonate (PC) (30 parts) and elastomers (70 parts) of varying polarity, e.g., ethylene propylene diene rubber (EPDM), chlorinated polyethylene (CPE), nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), acrylic rubber (ACM) have been studied and characterized by various methods, e.g., stress-strain measurement, surface energy estimation, thermogravimetric analysis, dynamic mechanical analysis and volume resistivity measurement. The highest

Namita Roy Choudhury; Anil K. Bhowmick

1996-01-01

309

Structural response of bead-stiffened thermoplastic shear webs  

NASA Technical Reports Server (NTRS)

The results of an experimental and analytical study of the structural response and failure characteristics of selected bead-stiffened thermoplastic shear-webs are presented. Results are given for specimens with one stiffeneer, with two stiffeners, and different stiffener geometries. Selected analytical results that were obtained with the Computational Structural Mechanics (CSM) Testbed computer code are presented. Analytical results that describe normal and transverse shear stress are also presented.

Rouse, Marshall

1991-01-01

310

Binary and ternary blends of polylactide, polycaprolactone and thermoplastic starch  

Microsoft Academic Search

In this study binary and ternary blends of polylactide (PLA), polycaprolactone (PCL) and thermoplastic starch (TPS) are prepared using a one-step extrusion process and the morphology, rheology and physical properties are examined. The morphology and quantitative image analysis of the 50\\/50 PLA\\/TPS blend transverse phase size demonstrate a bimodal distribution and the addition of PCL to form a ternary blend

Pierre Sarazin; Gang Li; William J. Orts; Basil D. Favis

2008-01-01

311

Rheological and mechanical properties of polypropylene\\/thermoplastic starch blend  

Microsoft Academic Search

Starch as an inexpensive and renewable source has been used as a filler for environmentally friendly plastics for about two\\u000a decades. In order to improve the compatibility between hydrophilic starch granules and hydrophobic polypropylene (PP), glycerol\\u000a used as a plasticizer for starch to enhance the dispersion and the interfacial affinity in thermoplastic starch (TPS)\\/PP blend.\\u000a In this study, PP was

Mosab Kaseem; Kotiba Hamad; Fawaz Deri

312

Thermoset-thermoplastic aromatic polyamide containing N-propargyl groups  

NASA Technical Reports Server (NTRS)

The compounds of the class of aromatic polyamides useful as matrix resins in the manufacture of composites or laminate fabrication were developed. The process for preparing this thermoplastic-thermoset polyamide system involves incorporating a latent crosslinking moiety along the backbone of the polyamide to improve the temperature range of fabrication thereof wherein the resin softens at a relatively low temperature (approx. 154 C) and subsequently sets-up or undergoes crosslinking when subjected to higher temperature (approx. 280 C).

St.clair, T. L.; Wolfe, J. F.; Greenwood, T. D. (inventors)

1984-01-01

313

Behavior of Natural-Fiber\\/Thermoplastic Sheet Piling  

Microsoft Academic Search

This paper describes the flexural behavior of an innovative Natural-Fiber\\/Thermoplastic Composite (NFTC) also known as Wood Plastic Composite (WPC) sheet piling. Test methods were developed and full-scale bending tests were conducted to characterize the flexural performance of the piles as part of a larger effort to develop a structural design methodology. In this study, WPC sheet piling specimens were produced

Daniel Alvarez-Valencia; Habib J. Dagher

314

Elastic/viscoplastic behavior of fiber-reinforced thermoplastic composites  

NASA Technical Reports Server (NTRS)

An elastic/viscoplastic constitutive model was used to characterize the nonlinear and rate dependent behavior of a continuous fiber-reinforced thermoplastic composite. This model was incorporated into a finite element program for the analysis of laminated plates and shells. Details on the finite element formulation with the proposed constitutive model were presented. The numerical results were compared with experimental data for uniaxial tension and three-point bending tests of (+ or - 45 deg)3s APC-2 laminates.

Wang, C.; Sun, C. T.; Gates, T. S.

1990-01-01

315

Modified Single-Wall Carbon Nanotubes for Reinforce Thermoplastic Polyimide  

NASA Technical Reports Server (NTRS)

A significant improvement in the mechanical properties of the thermoplastic polyimide film was obtained by the addition of noncovalently functionalized single-wall carbon nanotubes (SWNTs). Polyimide films were reinforced using pristine SWNTs and functionalized SWNTs (F-SWNTs). The tensile strengths of the polyimide films containing F-SWNTs were found to be approximately 1.4 times higher than those prepared from pristine SWNTs.

Lebron-COlon, Marisabel; Meador, Michael A.

2006-01-01

316

Manufacturing Process and Application of Pseudo-thermoplastic Polyvinyl Alcohol  

Microsoft Academic Search

Polyvinyl alcohol (PVA) has too close melting and degradation temperatures which causes the failure of temperature control during processing. This study uses glycerin as plasticizing agent to improve high thermo-melting property of PVA so that PVA can be processed at a thermo-melt temperature of 190°C and be equipped with the pseudo-thermoplastic characteristic. The PVA processed with this method is called

Chin-An Lin; Hsiao-Chi Tsai; Te-Hsing Ku

2007-01-01

317

A procedure for measuring biaxial viscoelastic behavior of thermoplastics  

Microsoft Academic Search

In order to accurately simulate the thermoforming or blowmolding manufacturing processes using finite elements or some other\\u000a suitable computational procedure, it is necessary to know the constitutive behavior of the material being formed. In this\\u000a study, an apparatus was developed to measure the large deformation behavior of thermoplastic sheet at elevated temperatures.\\u000a The specifications of the test apparatus, as well

S. R. Hummel; H. F. Nied

2004-01-01

318

40 CFR 414.40 - Applicability; description of the thermoplastic resins subcategory.  

Code of Federal Regulations, 2010 CFR

... EFFLUENT GUIDELINES AND STANDARDS ORGANIC CHEMICALS, PLASTICS, AND SYNTHETIC FIBERS Thermoplastic Resins § 414.40...Polybutadiene *Polybutenes Polybutenyl Succinic Anhydride *Polycarbonates *Polyester Resins *Polyester Resins,...

2009-07-01

319

40 CFR 414.40 - Applicability; description of the thermoplastic resins subcategory.  

Code of Federal Regulations, 2010 CFR

... EFFLUENT GUIDELINES AND STANDARDS ORGANIC CHEMICALS, PLASTICS, AND SYNTHETIC FIBERS Thermoplastic Resins § 414.40...Polybutadiene *Polybutenes Polybutenyl Succinic Anhydride *Polycarbonates *Polyester Resins *Polyester Resins,...

2010-07-01

320

Novel alpha-zirconium phosphonates for the reinforcement of ductile thermoplastics  

NASA Astrophysics Data System (ADS)

Ductile thermoplastics are useful additives for providing fracture toughness to brittle thermosetting polymers; however, this toughening is usually accompanied by a significant decrease in elastic modulus. Therefore, alpha-zirconium phosphonates (ZrP) were developed and investigated as reinforcing nano-scale fillers that increase the yield strength and elastic modulus of a polyester thermoplastic without causing a reduction in its ductility. ZrP materials are synthetic layered compounds that are imbued with targeted organic surface functionalities and whose structural development can be carefully controlled in the laboratory. Ether-terminal alkyl ZrP materials were designed and synthesized, using a conventional ZrF62--mediated preparation, with the intent of developing strong dipole-dipole interactions between the layer surfaces and polyester macromolecules. Additionally, a general method for using lamellar lyotropic liquid crystals (LLC's) as supramolecular templates for alkyl ZrP was evaluated, whose products showed promising similarity to the conventionally prepared materials. The LLC-forming characteristics of several organophosphonate preparations were determined, showing improved mesophase stability with mixed amphiphiles and preparation with R4N + counterions. A mixed-surface octyl/methoxyundecyl ZrP was produced and combined with polycaprolactone (PCL) and polymethylmethacrylate (PMMA) in concentrations up to 50% (w/w). The mechanical properties of the ZrP/PCL nanocomposite were evaluated by tensile, flexural, and dynamic mechanical testing methods. Nanocomposites containing 5% (w/w) ZrP showed significant increases in tensile yield stress and elastic modulus without suffering any loss of ductility versus the unfilled polymer. Layer delamination from the ZrP tactoids was minimal and did not occur through an intercalative mechanism. Higher ZrP loadings resulted in the agglomeration of tactoids, leading to defect structures and loss of strength and ductility. Intercalative penetration of the ZrP tactoids by PCL was limited by kinetic barriers and also the strong interlayer attraction between the ZrP surfaces. Further modification to the ZrP surface is needed to reduce self-attraction between the layers. Formulations including a mobile solvent may also lead to intercalation and swelling of the tactoids. Finally, in situ templating, based on the newly observed LLC constructs, is recommended to avoid any remaining kinetic barriers to intercalation.

Furman, Benjamin R.

321

Processing and Damage Tolerance of Continuous Carbon Fiber Composites Containing Puncture Self-Healing Thermoplastic Matrix  

NASA Technical Reports Server (NTRS)

Research at NASA Langley Research Center (NASA LaRC) has identified several commercially available thermoplastic polymers that self-heal after ballistic impact and through-penetration. One of these resins, polybutadiene graft copolymer (PB(sub g)), was processed with unsized IM7 carbon fibers to fabricate reinforced composite material for further evaluation. Temperature dependent characteristics, such as the degradation point, glass transition (T(sub g)), and viscosity of the PBg polymer were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic parallel plate rheology. The PBg resin was processed into approximately equal to 22.0 cm wide unidirectional prepreg tape in the NASA LaRC Advanced Composites Processing Research Laboratory. Data from polymer thermal characterization guided the determination of a processing cycle used to fabricate quasi-isotropic 32-ply laminate panels in various dimensions up to 30.5cm x 30.5cm in a vacuum press. The consolidation quality of these panels was analyzed by optical microscopy and acid digestion. The process cycle was further optimized based on these results and quasi-isotropic, [45/0/-45/90]4S, 15.24cm x 15.24cm laminate panels were fabricated for mechanical property characterization. The compression strength after impact (CAI) of the IM7/pBG composites was measured both before and after an elevated temperature and pressure healing cycle. The results of the processing development effort of this composite material as well as the results of the mechanical property characterization are presented in this paper.

Grimsley, Brian W.; Gordon, Keith L.; Czabaj, Michael W.; Cano, Roberto J.; Siochi, Emilie J.

2012-01-01

322

Material, process, and product design of thermoplastic composite materials  

NASA Astrophysics Data System (ADS)

Thermoplastic composites made of polypropylene (PP) and E-glass fibers were investigated experimentally as well as theoretically for two new classes of product designs. The first application was for reinforcement of wood. Commingled PP/glass yarn was consolidated and bonded on wood panel using a tie layer. The processing parameters, including temperature, pressure, heating time, cooling time, bonding strength, and bending strength were tested experimentally and evaluated analytically. The thermoplastic adhesive interface was investigated with environmental scanning electron microscopy. The wood/composite structural design was optimized and evaluated using a Graphic Method. In the second application, we evaluated use of thermoplastic composites for explosion containment in an arrester. PP/glass yarn was fabricated in a sleeve form and wrapped around the arrester. After consolidation, the flexible composite sleeve forms a solid composite shell. The composite shell acts as a protection layer in a surge test to contain the fragments of the arrester. The manufacturing process for forming the composite shell was designed. Woven, knitted, and braided textile composite shells made of commingled PP/glass yarn were tested and evaluated. Mechanical performance of the woven, knitted, and braided composite shells was examined analytically. The theoretical predictions were used to verify the experimental results.

Dai, Heming

323

Rechargeable lithium battery employing a new ambient temperature hybrid polymer electrolyte based on PVK+PVdF–HFP (copolymer)  

Microsoft Academic Search

We describe here for the first time, our recent success in developing an ambient temperature Li+ conducting solid polymer electrolyte (SPE) using the concept of polymer alloying upon blending two thermoplastic polymers such as poly(vinylidene) fluoride-hexafluoropropylene (PVdF–HFP-copolymer) and poly(N-vinylcarbazole), PVK and achieved the room temperature electrolytic conductivity (?i) of 0.7×10?3S\\/cm for a typical composition of PVdF–HFP copolymer\\/PVK blend mixed with

M. S. Michael; S. R. S. Prabaharan

2004-01-01

324

A novel high-performance gel polymer electrolyte membrane basing on electrospinning technique for lithium rechargeable batteries  

Microsoft Academic Search

Nonwoven films of composites of thermoplastic polyurethane (TPU) with different proportion of poly(vinylidene fluoride) (PVdF) (80, 50 and 20%, w\\/w) are prepared by electrospinning 9wt% polymer solution at room temperature. Then the gel polymer electrolytes (GPEs) are prepared by soaking the electrospun TPU–PVdF blending membranes in 1M LiClO4\\/ethylene carbonate (EC)\\/propylene carbonate (PC) for 1h. The gel polymer electrolyte (GPE) shows

Na Wu; Qi Cao; Xianyou Wang; Xiaoyun Li; Huayang Deng

325

Microstructural Characterization of Polymers by Positron Lifetime Spectroscopy  

NASA Technical Reports Server (NTRS)

Positrons provide a versatile probe for monitoring microstructural features of molecular solids. In this paper, we report on positron lifetime measurements in two different types of polymers. The first group comprises polyacrylates processed on earth and in space. The second group includes fully-compatible and totally-incompatible Semi-Interpenetrating polymer networks of thermosetting and thermoplastic polyimides. On the basis of lifetime measurements, it is concluded that free volumes are a direct reflection of physical/electromagnetic properties of the host polymers.

Singh, Jag J.

1996-01-01

326

Thermoplastic vulcanizate nanocomposites based on polypropylene/ethylene propylene diene terpolymer (PP/EPDM) prepared by reactive extrusion  

NASA Astrophysics Data System (ADS)

For this work, different grades of polypropylene-g-maleic anhydride polymers were chosen to elucidate the effect of compatibilizer on the nanoclay dispersion level in thermoplastic phase. X-ray diffraction (XRD) patterns along with transmission electron microscopy (TEM) and scanning electron microscope (SEM) micrographs confirmed that prepared PP nanocomposites ranged from intercalated structure to a coexistence of intercalated tactoids and exfoliated layers namely “partially exfoliated” nanocomposite. Among various factors affecting the compatibilizer performance, it is shown that only the relaxation behaviour of compatibilizer correlates directly with the nanocomposites characterization results; higher relaxation times of the compatibilizer are associated with better dispersion of nanoclay. To study the co-continuity development of the nonreactive blends, EPDM and the mentioned PP nanocomposites at various compositions were melt blended using an internal mixer. Based on continuity measurements of TPEs and TPE nanocomposites for both thermoplastic and rubber phase, it is shown that the presence of nanoclay decreases the co-continuity composition range and alters its symmetrical feature. However, this effect is more pronounced in the intercalated nanocomposites than in partially exfoliated nanocomposites. It seems that better nanoclay dispersion limits the reduction of the thermoplastic phase continuity in a manner that the continuity index of the thermoplastic phase for partially exfoliated TPE nanocomposite prepared at high EPDM content (i.e. at 70 wt%) is greater than that of corresponding TPE without nanoclay. According to these results, it is possible to shift to higher EPDM content using partially exfoliated system before formation of matrix-dispersed particle structure which limits thermoplastic vulcanizate production. This should be mentioned that gamma irradiation was carried out in order to fix the EPDM morphology to estimate the continuity of PP using the solvent extraction and gravimetry technique. Additionally, the effect of continuity on rheological behaviour of TPE nanocomposites was investigated. The ultimate goal in this field is to maximize the rubber like behaviour by controlling the blend morphology and the level of crosslinking. Therefore, this study also covers the effects of nanoclay presence and its dispersion level on the crosslinking reaction of thermoplastic vulcanizate nanocomposites prepared by reactive extrusion. Here, the rubber phase was dynamically vulcanized using dimethylol phenolic resin or octylphenol-formaldehyde resin along with stannous chloride dihydrate as the catalyst. In the present study, the dynamic vulcanization of the prepared TPVs and corresponding nanocomposites are characterized using different criteria, such as gel content, viscosity and normalized storage modulus in the time sweep tests, nuclear magnetic resonance (NMR) signal line width, bound curative content and residual diene concentration. The combination of the above parameters appears to be sufficient to provide a clear description of the systems. The last part of the present study is devoted to find how the dispersion level of nanoclay and consequently the extent of crosslinking change the rubber like behaviour and the morphology of the prepared TPVs. Therefore, recently developed method named temperature scanning stress relaxation (TSSR) was used to estimate the rubber indices of TPVs and TPV nanocomposites. The mentioned method also successfully provided information about the extent of crosslinking reaction. It is shown that the rubber like behaviour of the blends containing 50wt% and 60wt% of EPDM in which morphological studies suggest the presence of the rubber droplets in vicinity of irregular shape rubber particles with a low level of interconnectivity, correlates with the rubber droplet size. Therefore, the nanoclay presence affects the rubber index values mainly through its effect on the size of the rubber droplets that controls the number of retraction points in the proposed buckling mechanism duri

Mirzadeh, Amin

327

LaRC TPI 1500 series polymers  

NASA Technical Reports Server (NTRS)

The crystallization behavior and the melt flow properties of two batches of 1500 series LaRC-TPI polymers from Mitsui Toatsu Chemicals (MTC) were investigated. The characterization methods include Differential Scanning Calorimetry, the x ray diffractography and the melt rheology. The as-received materials possess initial crystalline melting peak temperatures of 295 and 305 C, respectively. These materials are less readily recrystallizable at elevated temperatures when compared to other semicrystalline thermoplastics. For the samples annealed at temperatures below 330 C, a semicrystalline polymer can be obtained. On the other hand, a purely amorphous structure is realized in the samples annealed at temperatures above 330 C. Isothermal crystallization kinetics were studied by means of the simple Avrami equation. The viscoelastic properties at elevated temperatures below and above glass transition temperature of the polymers were measured. Information with regard to the molecule sizes and distributions in these polymers were also extracted from melt rheology.

Hou, Tan-Hung; Bai, Jia-Mo

1990-01-01

328

Viscoelastic behavior and electrical properties of flexible nanofiber filled polymer nanocomposites. Influence of processing conditions  

Microsoft Academic Search

Two different types of high aspect ratio flexible nanofibers, cellulose nanofibrils and carbon nanotubes, were dispersed in an amorphous thermoplastic polymer matrix. The mechanical and (in the case of carbon nanotubes filled composites) electrical properties of these composites were investigated. Dynamic mechanical analysis highlighted the influence of entanglements between fibers and of fiber\\/fiber contact properties on the composite mechanical reinforcement

Florent Dalmas; Jean-Yves Cavaillé; Catherine Gauthier; Laurent Chazeau; Rémy Dendievel

2007-01-01

329

Production and characterization of polymer nanocomposite with aligned single wall carbon nanotubes  

Microsoft Academic Search

We reported a simple method to fabricate polymer nanocomposites with single-walled carbon nanotubes (SWNTs) having exceptional alignment and improved mechanical properties. The composite films were fabricated by casting a suspension of single walled carbon nanotubes in a solution of thermoplastic polyurethane and tetrahydrofuran. The orientation as well as dispersion of nanotubes was determined by scanning electron microscopy, transmission electron microscopy

Wei Chen; Xiaoming Tao

2006-01-01

330

Electroless copper plating and surface characterization of thermoplastic PPO based printed circuit boards  

Microsoft Academic Search

Purpose – The adhesion between electroless copper and a substrate is one of the most important factors in the reliability of thermoplastic printed circuit boards. The purpose of this paper is to investigate the effects of mechanical grinding and acid etching of thermoplastic substrate materials on the adhesion of copper deposited by an electroless copper plating process. The base material

Teija Laine-Ma; Pekka Ruuskanen; Satu Kortet; Mikko Karttunen

2009-01-01

331

Study on the ? relaxation mechanism of thermosetting polyimide\\/thermoplastic polyimide blends  

Microsoft Academic Search

The thermosetting polyimide PMR-15 and its blends with thermoplastic polyimides have been studied by dynamic mechanical analysis. The results obtained indicate that the level of ? relaxations in PMR-15 are increased with an increase in cross-linking density. This phenomenon is interpreted as a change of chemical structure during the cross-linking process. Addition of thermoplastic polyimide makes the magnitude of ?

Hao Tang; Lisong Dong; Jin Zhang; Menxian Ding; Zhiliu Feng

1996-01-01

332

High strength–toughness combination of melt intercalated nanoclay-reinforced thermoplastic olefins  

Microsoft Academic Search

We examine here the mechanical behavior and the micromechanism of fracture in impact tested neat and nanoclay-reinforced thermoplastic olefins, both of which have been processed under similar conditions. The reinforcement of thermoplastic olefins with nanoclay increases modulus and yields strength of the resulting nanocomposite and retains impact strength. The enhancement of modulus and yield strength is related to the reinforcement

C. Deshmane; Q. Yuan; R. D. K. Misra

2007-01-01

333

Development of LaRC (TM): IA thermoplastic polyimide coated aerospace wiring  

NASA Technical Reports Server (NTRS)

NASA Langley has invented LaRC(exp TM) IA and IAX which are thermoplastic polyimides with good melting, thermal and chemical resistance properties. It was the objective of this contract to prepare and extrude LaRC (exp TM) polyimide onto aircraft wire and evaluate the polymers performance in this critical application. Based on rheology and chemical resistance studies at Imitec, LaRC (exp TM) IAX melts readily in an extruder, facilitating the manufacture of thin wall coatings. The polyimide does not corode the extruder, develop gel particles nor advance in viscosity. The insulated wire was tested according to MiL-W-22759E test specifications. The resulting wire coated with LaRC (exp TM) IAX displayed exceptional properties: surface resistance, non blocking, non burning, hot fluid resistance, impulse dielectric, insulation resistance, low temperature flexibility, thermal aging, wire weight, dimensions, negligible high temperature shrinkage and stripability. The light weight and other properties merit its application in satellites, missiles and aircraft applications. The extruded IAX results in a polyimide aircraft insulation without seams, outstanding moisture resistance, continuous lengths and abrasion resistance.

Keating, Jack

1995-01-01

334

Sensitivity Studies for In-Situ Automated Tape Placement of Thermoplastic Composites  

NASA Technical Reports Server (NTRS)

This modeling effort seeks to improve the interlaminate bond strength of thermoplastic carbon composites produced by the in-situ automated tape placement (ATP) process. An existing high productivity model is extended to lower values of the Peclet number that correspond to the present operating conditions of the Langley ATP robot. (The Peclet number is the dimensionless ratio of inertial to diffusive heat transfer.) In sensitivity studies, all of the process and material parameters are individually varied. The model yields the corresponding variations in the effective bonding time (EBT) referred to the glass transition temperature. According to reptation theory, the interlaminate bond strength after wetting occurs is proportional to the one-fourth power of EBT. The model also computes the corresponding variations in the thermal input power (TIP) and the mass and volumetric process rates. Process studies show that a 10 percent increase in the consolidation length results in a 20 percent increase in EBT and a 5 percent increase in TIP. A surprising result is that a 10 K decrease in the tooling temperature results in a 25 percent increase in EBT and an 8 percent increase in TIP. Material studies show that a 10 K decrease in glass transition temperature results in an 8 percent increase in EBT and a 8 percent decrease in TIP. A 20 K increase in polymer degradation temperature results in a 23 percent increase in EBT with no change in TIP.

Costen, Robert C.; Marchello, Joseph M.

2004-01-01

335

Tunable wetting of polymer surfaces.  

PubMed

A simple method was developed for the preparation of polymeric materials with controlled surface wettability or tunable surface wetting. The method is applicable to a large number of polymers, thermoplastic or thermoset. With this method, it is possible to prepare polymer surfaces with static water contact angles ranging from 0° (superhydrophilic) to greater than 170° (superhydrophobic). The method developed is based on spin-coating of a hydrophilic/hydrophobic silica mixture dispersed in an organic solvent or solvent mixture onto the polymer surface. Depending on the hydrophilic/hydrophobic silica ratio in the coating mixture, it is possible to obtain polymer surfaces displaying gradually changing wettability from superhydrophilic to superhydrophobic. In this article, preparation and surface characteristics of polystyrene (PS) and cross-linked epoxy resin (ER) films are provided as general examples. Polymer surfaces obtained were characterized by scanning electron microscopy, white light interferometry, atomic force microscopy, X-ray photoelectron spectroscopy, and static water contact angle measurements. Effects of the type of polymeric substrate and composition of the silica mixture on the surface behavior of the composite systems were investigated. PMID:22989033

Yilgor, Iskender; Bilgin, Sevilay; Isik, Mehmet; Yilgor, Emel

2012-10-16

336

Capillary Force Lithography: Fabrication of Functional Polymer Templates as Versatile Tools for Nanolithography  

Microsoft Academic Search

The implementation of high-resolution polymer templates fabricated by capillary force lithography (CFL) is explored both in nanoimprint lithography (NIL) and in the wet-etching of metals. Several different thermoplastic and UV-curable polymers and types of substrates are incorporated into the general CFL procedure to meet the diverging requirements of these two applications. The mechanical stability of UV-curable templates for imprinting in

Christiaan M. Bruinink; Mária Peter; Pascale A. Maury; Boer de Meint; Laurens Kuipers; Jurriaan Huskens; David N. Reinhoudt

2006-01-01

337

New Results on Plasma Activated Bonding of Imprinted Polymer Features for Bio MEMS Applications  

Microsoft Academic Search

Nanoimprint Lithography is a well-acknowledged low cost, high resolution, large area 3D patterning process for polymers. It includes the most promising methods: high pressure hot embossing (HE) and UV-Nanoimprint Lithography (UV-NIL). Curing of the imprinted structures is either done by cooling down below the glass transition temperature of the thermoplastic polymer in case of HE or by subsequent UV-light exposure

P. Kettner; R. L. Pelzer; T. Glinsner; S. Farrens; D. Lee

2006-01-01

338

A molecular network model to describe the nonlinear viscoelastic behavior of polymers  

Microsoft Academic Search

A transient molecular network model is built to describe the nonlinear viscoelasticity of polymers by considering the effect\\u000a of entanglement loss and regeneration on the relaxation of molecular strands. It is an extension of previous network theories.\\u000a The experimental data on three thermoplastic polymers (ABS, PVC and PA6) obtained under various loading conditions are used\\u000a to test the model. Agreement

Chen Xiaohong; Han Mingbao; Wang Ren

1993-01-01

339

All-thermoplastic nanoplasmonic microfluidic device for transmission SPR biosensing.  

PubMed

Early and accurate disease diagnosis still remains a major challenge in clinical settings. Biomarkers could potentially provide useful tools for the detection and monitoring of disease progression, treatment safety and efficacy. Recent years have witnessed prodigious advancement in biosensor development with research directed towards rapid, real-time, label-free and sensitive biomarker detection. Among emerging techniques, nanoplasmonic biosensors pose tremendous potential to accelerate clinical diagnosis with real-time multiplexed analysis, rapid and miniaturized assays, low sample consumption and high sensitivity. In order to translate these technologies from the proof-of-principle concept level to point of care clinical diagnosis, integrated, portable devices having small footprint cartridges that house low-cost disposable consumables are sought. Towards this goal, we developed an all-polymeric nanoplasmonic microfluidic (NMF) transmission surface plasmon resonance (SPR) biosensor. The device was fabricated in thermoplastics using a simple, single step and cost-effective hot embossing technique amenable to mass production. The novel 3D hierarchical mold fabrication process enabled monolithic integration of blazed nanogratings within the detection chambers of a multichannel microfluidic system. Consequently, a single hard thermoplastic bottom substrate comprising plasmonic and fluidic features allowed integration of active fluidic elements, such as pneumatic valves, in the top soft thermoplastic cover, increasing device functionality. A simple and compact transmission-based optical setup was employed with multiplexed end-point or dual-channel kinetic detection capability which did not require stringent angular accuracy. The sensitivity, specificity and reproducibility of the transmission SPR biosensor was demonstrated through label-free immunodetection of soluble cell-surface glycoprotein sCD44 at clinically relevant picomolar to nanomolar concentrations. PMID:23287840

Malic, Lidija; Morton, Keith; Clime, Liviu; Veres, Teodor

2013-03-01

340

Wear testing and measurement techniques for polymer composite gears  

Microsoft Academic Search

Injection-moulded composite gears using fibre-reinforced thermoplastics often exhibit increased performance compared with those made from unreinforced polymers. In general, materials are chosen on cost or simple performance grounds (such as, nominal flexural modulus or heat deflection temperature).Aspects of the performance of polymeric gears have been studied by a number of workers and efforts have been made to simulate the contact

N. A Wright; S. N Kukureka

2001-01-01

341

ZnO Nanorod Thermoplastic Polyurethane Nanocomposites: Morphology and Shape Memory Performance  

SciTech Connect

The impact of dispersed alkylthiol-modified ZnO nanorods, as a function of rod aspect ratio and concentration, on the shape memory character of a thermoplastic polyurethane with low hard-segment density (LHS-TPU) is examined relative to the enhanced performance occurring for carbon nanofiber (CNF) dispersion. Solution blending resulted in uniform dispersion within the LHS-TPU of the ZnO nanorods at low volume (weight) fractions (<2.9% v/v (17.75% w/w)). Tensile modulus enhancements were modest though, comparable to values observed for spherical nanofillers. Shape memory characteristics, which in this LHS-TPU result when strain-induced crystallites retard the entropic recovery of the deformed chains, were unchanged for these low volume fraction ZnO nanocomposites. Higher ZnO loadings (12% v/v (50% w/w)) exhibited clustering of ZnO nanorods into a mesh-like structure. Here, tensile modulus and shape recovery characteristics were improved, although not as great as seen for comparable CNF addition. Wide angle X-ray diffraction and NMR revealed that the addition of ZnO nanorods did not impact the inherent strain induced crystallization of the LHS-TPU, which is in contrast to the impact of CNFs and emphasizes the impact of interactions at the polymer-nanoparticle interface. Overall, these findings reinforce the hypothesis that the shape memory properties of polymer nanocomposites are governed by the extent to which nanoparticle addition, via nanoparticle aspect ratio, hierarchical morphology, and interfacial interactions, impacts the molecular mechanism responsible for trapping elastic strain.

Koerner, H.; Kelley, J; George, J; Drummy, L; Mirau, P; Bell, N; Hsu, J; Vaia, R

2009-01-01

342

Erosion behavior and mechanical properties of thermoplastic polyurethanes  

NASA Astrophysics Data System (ADS)

Solid particle erosion is a crucial aspect for the performance and lifetime of important components utilized in several fields. Thermoplastic Polyurethanes (TPUs) are often selected as coating materials on the basis of their very interesting erosion behavior. But despite serious attempts in recent years to correlate their extraordinary performance with morphological and mechanical properties, only few indications are available today. This paper investigates the erosion of several TPUs by quartz sand particles using a high impact velocity (160m/s) under various impact angles. The results, expressed in terms of erosion rate, suggest that the viscoelastic properties could play an important role in their erosion behavior.

Acierno, Domenico; Sanguigno, Luigi; Arena, Gaetano; Friedrich, Klaus; Padenko, Eugen; Russo, Pietro

2014-05-01

343

Impact characterization of graphite fiber reinforced thermoplastic laminates  

NASA Astrophysics Data System (ADS)

Instrumented drop-weight impact testings were conducted in conjunction with the ultrasonic C-scan and scanning electron microscopy to characterize the impact response at low velocities. Thermoplastic composite materials in the simply supported case showed dramatic improvements in impact damage resistance compared to the thermoset composite materials as reported. Scanning electron microscopy examination of the fracture surface revealed fiber-matrix-debonding, fiber pull-out, and few delaminations. Matrix behavior can be characterized by a hackly appearance. On the other hand, the fracture mechanisms of the transverse normal compression and shear punch were matrix cracking and grouped lamina delamination as opposed to individual lamina delamination, respectively.

Chaudhuri, J.; Choe, G. H.; Vinson, J. R.

1993-06-01

344

Moisture sorption and plasticization of bloodmeal-based thermoplastics  

Microsoft Academic Search

Sorption characteristics, thermo-mechanical and mechanical properties of bloodmeal-based thermoplastics have been investigated\\u000a between water activities (a\\u000a w) of 0.2 and 0.8, using water and tri-ethylene glycol (TEG) as plasticizers. Three different mass ratios of TEG to water were\\u000a used, 1:1, 1:2 and 5:6 with a total plasticizer content of 60 parts per hundred parts bloodmeal. It was found that the

Casparus J. R. VerbeekNicolas; Nicolas J. Koppel

345

Time Issues in Semi-Crystalline Thermoplastics Processing  

NASA Astrophysics Data System (ADS)

Cooling rate of semicrystalline thermoplastic (PEEK) based composite parts has been assessed by means of a thermal flow model. Cold tool thermoforming was found suitable for thin parts, but the use of a preheated tool is suggested. Cooling rate is critical for automated lay-up consequently the optimization of this technique requires the use of a complex apparatus, able to provide both heating of the part during lay-up and a control of the cooling rate. Alternatively a modified cooling rate vs. crystallinity behavior of the material must be achieved.

Iannone, Michele

2010-06-01

346

Polymer Concretes.  

National Technical Information Service (NTIS)

A review of the uses of polmers in concretes was carried out, including: polymer concretes such as impregnated composites, premixed polymer concretes and polymer bound aggregates; concretes which have solid, water soluble or dispersed polymers added to th...

1975-01-01

347

Polyphenylquinoxalines containing pendant phenylethynyl and ethynyl groups. [for thermoplastic resins  

NASA Technical Reports Server (NTRS)

Poly(phenylquinoxaline) prepolymers containing pendant phenylethynyl and ethynyl groups are disclosed along with the process for forming these polymers. Monomers and the process for producing same that are employed to prepare the polymers are also disclosed.

Hergenrother, P. M. (inventor)

1983-01-01

348

Shrinking Polymers  

NSDL National Science Digital Library

In this activity, learners discover that some plastics will shrink when you get them hot. Learners bake polystyrene in a regular oven and discover what happens. Safety note: Learners need an adult's help for this activity! Use this activity to talk about different types of plastics such as thermoplastics and thermosets.

Foundation, Polymer S.

2004-01-01

349

Polymer research at NASA Langley Research Center  

NASA Technical Reports Server (NTRS)

Polymer synthesis programs involve the development of Novel thermoplastics, pseudothermoplastics, and thermosets. These systems are prepared to elucidate structure-property relationships involving thermal capabilities, toughness, processability and environmental stability. Easily processable polyimides, solvent-resistant polysulfones and polyphenylquinoxalines, and tougher high and intermediate temperature polymers were developed. Characterization efforts included high pressure liquid chromatography methodology, the development of toughness tests for fiber reinforced composites, a study of electrical properties of metal ion filled polyimides, and a study of the mutagenicity of aromatic diamines. Also the mechanism of cure/degradation of experimental polymers was studied by rheology, mechanical behavior, separation techniques and spectroscopy. The degradative crosslinking of alkyl-containing polyimides, the separation and identification of crosslinked phenylquinoxalines, the rheological behavior of hot-melt polyimides, and the elucidation of the cure of norbornene endcapped imides were also studied.

St.clair, T. L.; Johnston, N. J.

1982-01-01

350

Magnetostrictive pressure device for thermoplastic fiber placement process  

NASA Astrophysics Data System (ADS)

Fiber reinforced composites offer excellent specific stiffness and strength and are therefore interesting for rotating machinery applications. The main disadvantage of high performance composites is the manufacturing process which is labor intensive and thus slow and expensive. The Thermoplastic Fiber Placement process overcomes these difficulties due to its high degree of automation. During the process, an impregnated tape is heated up and then consolidated in-situ under pressure. The process which is used at ABB consists of a six axis robot, a heat source and a pressure device for consolidation. Today mechanical roller element are used to apply the forces normal to the surface to the composite part. These forces are necessary for proper consolidation. The roller action prevents damage due to shearing of the tape during lay down. To improve the processing sped, and to expand the use of the Thermoplastic Fiber Placement process for more complex structures, two severe drawbacks of the solid roller approach need to be overcome; the small pressure contact area which limits the speed of the process and the poor conformability which prevents the process from being applied to highly 3D surfaces. Smart materials such as piezoelectrics, electrostrictives and magnetostrictives can produce high forces at high operating frequencies and enable a large, conformable actuated surface to be realized. A pressure device made with a magnetostrictive actuator has been tested. The main design goal is to apply the consolidation pressure correctly, without introducing shear forces on the tape, in order to produce parts with optimal mechanical properties.

Ahrens, Markus; Mallick, Vishal

1999-07-01

351

CREEP MODELING FOR INJECTION-MOLDED LONG-FIBER THERMOPLASTICS  

SciTech Connect

This paper proposes a model to predict the creep response of injection-molded long-fiber thermoplastics (LFTs). The model accounts for elastic fibers embedded in a thermoplastic resin that exhibits the nonlinear viscoelastic behavior described by the Schapery’s model. It also accounts for fiber length and orientation distributions in the composite formed by the injection-molding process. Fiber length and orientation distributions were measured and used in the analysis that applies the Eshelby’s equivalent inclusion method, the Mori-Tanaka assumption (termed as the Eshelby-Mori-Tanaka approach) and the fiber orientation averaging technique to compute the overall strain increment resulting from an overall constant applied stress during a given time increment. The creep model for LFTs has been implemented in the ABAQUS finite element code via user-subroutines and has been validated against the experimental creep data obtained for long-glass-fiber/polypropylene specimens. The effects of fiber orientation and length distributions on the composite creep response are determined and discussed.

Nguyen, Ba Nghiep; Kunc, Vlastimil; Bapanapalli, Satish K.

2008-06-30

352

Stress-induced structural changes in thermoplastic composites  

SciTech Connect

Polymeric Composites: Cyclic stress effects on PEEK (Poly-ether-ether-ketone) matrix thermoplastic composite system were examined by thermal-analysis techniques: DSC (Differential Scanning Calorimeter), DMA (Dynamic Mechanical Analysis), TMA (Thermomechanical Analysis), TGA (Thermogravimetric Analysis), TMA (Thermomechanical Analysis), TGA (Thermogravimetric Analysis), DGT (Density Gradient Technique), and WAXS (Wide angle X-ray Scattering). These measurements identified for the first time stress-induced crystallization of PEEK below the glass transition temperature (Tg). Also, PEEK crystallization above T[sub g] was kinetically studied by DSC and DMA, and a previously developed dual-crystallization methodology was extended to account for the influence of stress on crystallization. Finally, a fatigue kinetic model for un-notched PEEK films and a crack propagation model for PEEK composites were also developed providing a relation between matrix morphology and end-use performance. Collectively, this work established the importance of structural changes in thermoplastic-based composites that can be both monitored and influenced by dynamic (cyclic) mechanical experiments.

Kitano, A.

1991-01-01

353

Interlaminate Deformation in Thermoplastic Composite Laminates: Experimental-Numerical Correlation  

NASA Astrophysics Data System (ADS)

The interlaminar deformation behaviors of thermoplastic AS4/PEEK composite laminates subjected to static tensile loading are investigated by means of microscopic moiré interferometry with high spatial resolution. The fully threedimensional orthotropic elastic-plastic analysis of interlaminar deformation for the thermoplastic laminates is developed in this paper, and used to simulate the stress-strain curves of tensile experiment for its angle-ply laminates. Under uniaxial tensile loading, the 3D orthotropic elastic-plastic FE analysis and microscopic moiré interferometry of interlaminar deformations are carried out for the [±25]S4 laminates. The quantitative local-filed experimental results of interlaminar shear strain and displacements at freeedge surface of the laminate are compared with corresponding numerical results of the orthotropic elastic-plastic FE model. It is indicated that the numerical tensile stressstrain curves of angle-ply laminates computed with 3D orthotropic elastic-plastic model are agree with experimental results. The numerical interlaminar displacement U and shear strain ?xz are also consistent with the experimental results obtained by moiré interferometry. It is expected the elastic-plastic interlaminar stresses and deformations analysis for the optimal design and application of AS4/PEEK laminates and its structures.

Shen, M.; Tong, J.; Wang, S.; Fang, Y.

2010-06-01

354

Dielectric Characterization of PCL-Based Thermoplastic Materials for Microwave Diagnostic and Therapeutic Applications  

PubMed Central

We propose the use of a polycaprolactone (PCL)-based thermoplastic mesh as a tissue-immobilization interface for microwave imaging and microwave hyperthermia treatment. An investigation of the dielectric properties of two PCL-based thermoplastic materials in the frequency range of 0.5 – 3.5 GHz is presented. The frequency-dependent dielectric constant and effective conductivity of the PCL-based thermoplastics are characterized using measurements of microstrip transmission lines fabricated on substrates comprised of the thermoplastic meshes. We also examine the impact of the presence of a PCL-based thermoplastic mesh on microwave breast imaging. We use a numerical test bed comprised of a previously reported three-dimensional anatomically realistic breast phantom and a multi-frequency microwave inverse scattering algorithm. We demonstrate that the PCL-based thermoplastic material and the assumed biocompatible medium of vegetable oil are sufficiently well matched such that the PCL layer may be neglected by the imaging solution without sacrificing imaging quality. Our results suggest that PCL-based thermoplastics are promising materials as tissue immobilization structures for microwave diagnostic and therapeutic applications.

Aguilar, Suzette M.; Shea, Jacob D.; Al-Joumayly, Mudar A.; Van Veen, Barry D.; Behdad, Nader; Hagness, Susan C.

2011-01-01

355

Dielectric characterization of PCL-based thermoplastic materials for microwave diagnostic and therapeutic applications.  

PubMed

We propose the use of a polycaprolactone (PCL)-based thermoplastic mesh as a tissue-immobilization interface for microwave imaging and microwave hyperthermia treatment. An investigation of the dielectric properties of two PCL-based thermoplastic materials in the frequency range of 0.5-3.5 GHz is presented. The frequency-dependent dielectric constant and effective conductivity of the PCL-based thermoplastics are characterized using measurements of microstrip transmission lines fabricated on substrates comprised of the thermoplastic meshes. We also examine the impact of the presence of a PCL-based thermoplastic mesh on microwave breast imaging. We use a numerical test bed comprised of a previously reported 3-D anatomically realistic breast phantom and a multi-frequency microwave inverse scattering algorithm. We demonstrate that the PCL-based thermoplastic material and the assumed biocompatible medium of vegetable oil are sufficiently well matched such that the PCL layer may be neglected by the imaging solution without sacrificing imaging quality. Our results suggest that PCL-based thermoplastics are promising materials as tissue immobilization structures for microwave diagnostic and therapeutic applications. PMID:21622068

Aguilar, Suzette M; Shea, Jacob D; Al-Joumayly, Mudar A; Van Veen, Barry D; Behdad, Nader; Hagness, Susan C

2012-03-01

356

High-Temperature Shape Memory Polymers  

NASA Technical Reports Server (NTRS)

physical conformation changes when exposed to an external stimulus, such as a change in temperature. Such materials have a permanent shape, but can be reshaped above a critical temperature and fixed into a temporary shape when cooled under stress to below the critical temperature. When reheated above the critical temperature (Tc, also sometimes called the triggering or switching temperature), the materials revert to the permanent shape. The current innovation involves a chemically treated (sulfonated, carboxylated, phosphonated, or other polar function group), high-temperature, semicrystalline thermoplastic poly(ether ether ketone) (Tg .140 C, Tm = 340 C) mix containing organometallic complexes (Zn++, Li+, or other metal, ammonium, or phosphonium salts), or high-temperature ionic liquids (e.g. hexafluorosilicate salt with 1-propyl-3- methyl imidazolium, Tm = 210 C) to form a network where dipolar or ionic interactions between the polymer and the low-molecular-weight or inorganic compound forms a complex that provides a physical crosslink. Hereafter, these compounds will be referred to as "additives". The polymer is semicrystalline, and the high-melt-point crystals provide a temporary crosslink that acts as a permanent crosslink just so long as the melting temperature is not exceeded. In this example case, the melting point is .340 C, and the shape memory critical temperature is between 150 and 250 C. PEEK is an engineering thermoplastic with a high Young fs modulus, nominally 3.6 GPa. An important aspect of the invention is the control of the PEEK functionalization (in this example, the sulfonation degree), and the thermal properties (i.e. melting point) of the additive, which determines the switching temperature. Because the compound is thermoplastic, it can be formed into the "permanent" shape by conventional plastics processing operations. In addition, the compound may be covalently cross - linked after forming the permanent shape by S-PEEK by applying ionizing radiation ( radiation, neutrons), or by chemical crosslinking to form a covalent permanent network. With respect to other shape memory polymers, this invention is novel in that it describes the use of a thermoplastic composition that can be thermally molded or solution-cast into complex "permanent" shapes, and then reheated or redissolved and recast from solution to prepare another shape. It is also unique in that the shape memory behavior is provided by a non-polymer additive.

Yoonessi, Mitra; Weiss, Robert A.

2012-01-01

357

Damage accumulation at notches and the fracture stress of carbon-fibre\\/polymer composites: Combined effects of stress and temperature  

Microsoft Academic Search

Damage accumulation around a notch in a tough thermoplastic or a toughened thermosetting polymer containing carbon fibres has been shown to depend on the magnitude of the localised tensile stress, temperature, extent of thermal cycling and ductility of the matrix. The nature and extent of damage have been investigated by X-ray radiography. Thermal cycling to moderate temperature sets up thermal

Kevin D. Cowley; Peter W. R. Beaumont

1997-01-01

358

Experimental observation and prediction of interfacial tension and viscoelastic emulsion model behavior in novel phosphate glass–polymer hybrids  

Microsoft Academic Search

The interfacial tension of hybrids composed of a tin-based phosphate glass (Pglass) and thermoplastic polymers, low-density polyethylene (LDPE), polystyrene (PS), and polypropylene (PP) was investigated using pendant drop and droplet deformation methods. High surface tension values were determined for the pure Pglass and subsequently used to obtain interfacial tension values that were found to be greater than that of most

Peter C Guschl; Joshua U Otaigbe

2003-01-01

359

Preparation and rheological behavior of polymer-modified asphalts  

NASA Astrophysics Data System (ADS)

Different materials and methods were used to prepare and stabilize polymer-modified asphalts. Addition of thermoplastic elastomers improved some technically important properties of asphalt. Due to inherent factors like large density difference between asphalt and polyethylene, many physical methods in which the structure of asphalt is unchanged, failed to stabilize this system. The effect of addition of copolymers and a pyrolytic oil residue derived from used tire rubber were also studied and found to be ineffective on the storage stability of the polymer-asphalt emulsions while high and moderate temperature properties of the asphalt were found to be improved. Finally, the technique of catalytic grafting of polymer on the surface of high-density particles (e.g. carbon black) was used to balance the large density difference between asphalt and polymer. The resulting polymer-asphalts were stable at high temperatures and showed enhanced properties at low and high temperatures.

Yousefi, Ali Akbar

1999-09-01

360

Patterning methods for polymers in cell and tissue engineering.  

PubMed

Polymers provide a versatile platform for mimicking various aspects of physiological extracellular matrix properties such as chemical composition, rigidity, and topography for use in cell and tissue engineering applications. In this review, we provide a brief overview of patterning methods of various polymers with a particular focus on biocompatibility and processability. The materials highlighted here are widely used polymers including thermally curable polydimethyl siloxane, ultraviolet-curable polyurethane acrylate and polyethylene glycol, thermo-sensitive poly(N-isopropylacrylamide) and thermoplastic and conductive polymers. We also discuss how micro- and nanofabricated polymeric substrates of tunable elastic modulus can be used to engineer cell and tissue structure and function. Such synergistic effect of topography and rigidity of polymers may be able to contribute to constructing more physiologically relevant microenvironment. PMID:22258887

Kim, Hong Nam; Kang, Do-Hyun; Kim, Min Sung; Jiao, Alex; Kim, Deok-Ho; Suh, Kahp-Yang

2012-06-01

361

Correlation between thermal, optical and morphological properties of heterogeneous blends of poly(3-hexylthiophene) and thermoplastic polyurethane  

NASA Astrophysics Data System (ADS)

A correlation between thermal, optical and morphological properties of self-sustained films formed from blends of poly(3-hexylthiophene) (P3HT) and thermoplastic polyurethane (TPU), with 1, 10 and 20 wt% of P3HT in TPU, is established. Images of scanning electron microscopy (SEM) show the formation of domains of P3HT into the TPU matrix, characterizing the blend material as heterogeneous. The heat capacity (Cp) dependence on P3HT contents was investigated in a large temperature interval. In the region of the TPU glass transition, the difference between the experimental and predicted ?Cp values is more pronounced for the 1 wt% case, which strongly suggests that in this case there is a higher influence of the P3HT chains on the TPU matrix. The SEM images for the 1 wt% blended film present the formation of the smallest P3HT domains in the TPU matrix. The relatively high reduction of the PL intensity of the pure electronic transition peak in the 1 wt% blended film, in comparison to the other blended films and also to a pure P3HT film, favours the assumption that the smallest P3HT domains are at the origin of a more structural disordered character. This fact is in agreement with the results obtained by Raman spectroscopy and also by photoluminescence resolved by polarization in stretched self-sustained films, showing an ample correlation between morphological, thermal and optical properties of these blended materials. In addition, the thermoplastic properties of the polyurethane configure very good conditions for tensile drawing of P3HT and other conjugated polymer molecules.

Patrício, Patrícia S. O.; Calado, Hállen D. R.; de Oliveira, Flávio A. C.; Righi, Ariete; Neves, Bernardo R. A.; Silva, Glaura G.; Cury, Luiz A.

2006-08-01

362

LDRD final report on intelligent polymers for nanodevice performance control  

SciTech Connect

A variety of organic and hybrid organic-inorganic polymer systems were prepared and evaluated for their bulk response to optical, thermal and chemical environmental changes. These included modeling studies of polyene-bridged metal porphyrin systems, metal-mediated oligomerization of phosphaalkynes as heteroatomic analogues to polyacetylene monomers, investigations of chemically amplified degradation of acid- and base-sensitive polymers and thermally responsive thermoplastic thermosets based on Diels-Alder cycloaddition chemistry. The latter class of materials was utilized to initiate work to develop a new technique for rapidly building a library of systems with varying depolymerization temperatures.

JAMISON,GREGORY M.; LOY,DOUGLAS A.; WHEELER,DAVID R.; SAUNDERS,RANDALL S.L; SHELNUTT,JOHN A.; CARR,MARTIN J.; SHALTOUT,RAAFAT M.

2000-01-01

363

Interpenetrating polymer network approach to tougher and more microcracking resistant high temperature polymers. I. LaRC-RP40  

SciTech Connect

Interpenetrating polymer networks in the form of the LaRC-RP40 resin, prepared by the in situ polymerization of a thermosetting imide prepolymer and thermoplastic monomer reactants, are presently used to obtain toughness and microcracking resistance in a high-temperature polymer. Attention is presently given to the processing, physical, and mechanical properties, as well as the thermooxidative stability, of both the neat resin and the resin as a graphite fiber-reinforced matrix. Microcracking after thermal cycling was also tested. LaRC-RP40 exhibits significant resin fracture toughness improvements over the PMR-15 high-temperature matrix resin. 16 references.

Pater, R.H.; Morgan, C.D.

1988-10-01

364

Processing Optimization of Deformed Plain Woven Thermoplastic Composites  

NASA Astrophysics Data System (ADS)

This research addresses the processing optimization of post-manufactured, plain weave architecture composite panels consisted of four glass layers and thermoplastic polyurethane (TPU) when formed with only localized heating. Often times, during the production of deep drawn composite parts, a fabric preform experiences various defects, including non-isothermal heating and thickness variations. Minimizing these defects is of utmost importance for mass produceability in a practical manufacturing process. The broad objective of this research was to implement a design of experiments approach to minimize through-thickness composite panel variation during manufacturing by varying the heating time, the temperature of heated components and the clamping pressure. It was concluded that the heated tooling with least area contact was most influential, followed by the length of heating time and the amount of clamping pressure.

Smith, John R.; Vaidya, Uday K.

2013-12-01

365

Superhydrophobic thermoplastic polyurethane films with transparent/fluorescent performance.  

PubMed

In this paper, we report a simple and versatile route for the fabrication of superhydrophobic thermoplastic polyurethane (TPU) films. The approach is based on octadecanamide (ODAA)-directed assembly of nanosilica/TPU/ODAA hybrid with a well-defined sheetlike microstructure. The superhydrophobic hybrid film shows a transparent property, and its water contact angle reaches as high as 163.5° without any further low surface energy treatment. In addition, the superhydrophobic TPU hybrid film with fluorescent properties is achieved by smartly introducing CdTe quantum dots, which will extend potential application of the film to optoelectronic areas. The resulting fluorescent surface produced in this system is stable and has a water contact angle of 172.3°. This assembly method to control surface structures represents an intriguing and valuable route to tune the surface properties of organic-inorganic hybrid films. PMID:21043449

Yang, Shengyang; Wang, Lifang; Wang, Cai-Feng; Chen, Li; Chen, Su

2010-12-01

366

Effect of supramolecular structures on thermoplastic zein-lignin bionanocomposites.  

PubMed

The effect of alkaline lignin (AL) and sodium lignosulfonate (LSS) on the structure of thermoplastic zein (TPZ) was studied. Protein structural changes and the nature of the physical interaction between lignin and zein were investigated by means of X-ray diffraction and Fourier transform infrared (FT-IR) spectroscopy and correlated with physical properties. Most relevant protein structural changes were observed at low AL concentration, where strong H-bondings between the functional groups of AL and the amino acids in zein induced a destructuring of inter- and intramolecular interactions in ?-helix, ?-sheet, and ?-turn secondary structures. This destructuring allowed for an extensive protein conformational modification which, in turn, resulted in a strong improvement of the physical properties of the bionanocomposite. PMID:21834554

Oliviero, Maria; Verdolotti, Letizia; Di Maio, Ernesto; Aurilia, Marco; Iannace, Salvatore

2011-09-28

367

Modeling Fatigue Damage in Long-Fiber Thermoplastics  

SciTech Connect

This paper applies a fatigue damage model recently developed for injection-molded long-fiber thermoplastics (LFTs) to predict the modulus reduction and fatigue lifetime of glass/polyamide 6,6 (PA6,6) specimens. The fatigue model uses a multiscale mechanistic approach to describe fatigue damage accumulation in these materials subjected to cyclic loading. Micromechanical modeling using a modified Eshelby-Mori-Tanaka approach combined with averaging techniques for fiber length and orientation distributions is performed to establish the stiffness reduction relation for the composite as a function of the microcrack volume fraction. Next, continuum damage mechanics and a thermodynamic formulation are used to derive the constitutive relations and the damage evolution law. The fatigue damage model has been implemented in the ABAQUS finite element code and has been applied to analyze fatigue of the studied glass/PA6,6 specimens. The predictions agree well with the experimental results.

Nguyen, Ba Nghiep; Kunc, Vlastimil; Bapanapalli, Satish K.

2009-10-30

368

Tape Placement Head for Applying Thermoplastic Tape to an Object  

NASA Technical Reports Server (NTRS)

A tape placement head for applying thermoplastic tape to an object includes a heated feeder which guides the tape/tow to a heated zone. The heated zone has a line compactor having a single row of at least one movable heated member. An area compactor is located in the heated zone downstream from the line compactor. The area compactor includes a plurality of rows of movable feet which are extendable toward the tape/tow different distances with respect to each other to conform to the shape of the object. A shim is located between the heated compactors and the tape/tow. A chilled compactor is in a chilled zone downstream from the heated zone. The chilled zone includes a line chilled compactor and an area chilled compactor. A chilled shim is mounted between the chilled compactor and the tape/tow.

Cope, Ralph D. (Inventor); Funck, Steve B. (Inventor); Gruber, Mark B. (Inventor); Lamontia, Mark A. (Inventor); Johnson, Anthony D. (Inventor)

2008-01-01

369

Analysis of a space-exposed thermoplastic resin  

NASA Technical Reports Server (NTRS)

The chemical characterization of a thermoplastic resin exposed to the low Earth orbit (LEO) environment for 10 months and for 5.8 years is reported. The resin, processed as a thick film and as a matrix for a graphite fiber reinforced composite, few exposed in the RAM direction on the NASA Long Duration Exposure Facility (LDEF). Differences attributable to environmental exposure were detected in infrared spectra and in various molecular weight parameters of film after 10 months in LEO. Those effects were not as apparent in composites after 5.8 years in LEO. Increased exposure to atomic oxygen toward the end of the LDEF mission probably scrubbed these effects from specimens exposed for 5.8 years. The intent of this study is to increase our fundamental understanding of space environmental effects on polymeric materials and to develop a benchmark for enhancing our methodology for and understanding of the ground-based simulation of space environmental effects.

Young, Philip R.; Slemp, Wayne S.; Siochi, Emilie J.; Davis, Judith R. J.

1992-01-01

370

Sensitivity Studies for In-Situ Automated Tape Placement of Thermoplastic Composites.  

National Technical Information Service (NTIS)

This modeling effort seeks to improve the interlaminate bond strength of thermoplastic carbon composites produced by the in-situ automated tape placement (ATP) process. An existing high productivity model is extended to lower values of the Peclet number t...

R. C. Costen J. M. Marchello

2004-01-01

371

EXPERIMENTAL IDENTIFICATION OF FATIGUE DAMAGE MODEL FOR SHORT GLASS FIBRE REINFORCED THERMOPLASTIC COMPOSITES  

Microsoft Academic Search

A polycyclic fatigue damage model for short glass fibre reinforced thermoplastics is developed and implemented into ABAQUS FE code using UMAT subroutine. The MNL model is introduced here in terms of damage rates:

H. Nouri; H. Chalal; F. Meraghni; P. Lory

372

Studies of the Dynamic and Mechanical Properties of Thermoplastics by the Split Hopkinson Pressure Bar Method.  

National Technical Information Service (NTIS)

The split Hopkinson pressure bar method is introduced in the investigation of thermoplastics. Compression tests at strain rates of the order of 1000 s(-1) were performed on polypropylene, polyamide 6 and polycarbonate. The materials were studied in both e...

E. J. Paeaekkoenen P. Toermaelae V. T. Kuokkala

1981-01-01

373

Interlaminar Fatigue Crack Growth in a Thermoplastic-Matrix Fiber Composite at Room and Elevated Temperatures.  

National Technical Information Service (NTIS)

A study on the interlaminar fatigue crack growth behavior in a thermoplastic matrix composite at both room elevated temperatures is presented. Experiments are conducted on an AS4-graphite fiber/polyamide J1 resin composite system. Details of interlaminar ...

A. Miyase J. Blondet K. B. Su S. S. Wang

1989-01-01

374

Method of Determining the Thickness and Uniformity of Application for Thermoplastic Pavement Marking Material.  

National Technical Information Service (NTIS)

A laser thickness-measurement device for measuring the thickness of thermoplastic pavement marking material (TPMM) has been successfully developed. The system has been installed onto a pushcart for easy field operation. The device is based on a laser tria...

R. Liu J. Li X. Chen Y. Chen H. Xing R. Liang

2002-01-01

375

Epoxy Thermoplastic Marking Material: Summary of Research Results and Revised Specification.  

National Technical Information Service (NTIS)

This report presents the results of an extensive laboratory program to establish a specification for an epoxy thermoplastic (ETP) striping material which was developed in a contract research study for the Federal Highway Administration by Southwest Resear...

B. H. Chollar B. R. Appleman

1982-01-01

376

Remote Performance Monitoring of a Thermoplastic Composite Bridge at Camp Mackall, NC.  

National Technical Information Service (NTIS)

This Corrosion Prevention and Control project demonstrated the use of an automated structural performance monitoring (SPM) system to remotely monitor the long-term performance of an innovative bridge constructed of recycled thermoplastics. The SPM system ...

B. K. Myers D. M. Butler K. Palutke R. G. Lampo

2011-01-01

377

Processes for Dispersing Single Wall Carbon Nanotubes in Polymers and How to Determine Their Spatial and Alignment Distributions  

Microsoft Academic Search

We are currently designing and making polymer nanocomposites with single wall carbon nanotubes (SWNT) to obtain improved mechanical properties, electrical conductivity, flammability, and thermal conductivity. Our coagulation method is broadly applicable to nanocomposites using readily-soluble thermoplastics such as polystyrene and poly (methyl methacrylate). A variation of this method has been developed for nanotube\\/polymer composites based on high-density polyethylene. Nylon-based composites

Karen I. Winey

2006-01-01

378

Modification of wood fiber with thermoplastics by reactive steam-explosion processing  

Microsoft Academic Search

For the first time, a novel processing method of co-refining wood and polyolefin (PO) by steam-explosion was scientifically explored for wood-thermoplastic composites without a coupling agent. Traditional studies have addressed the improvement of adhesion between components of wood thermoplastic composites through the use of coupling agents such as maleated PO. The objective of this study was to increase adhesion between

Scott H. Renneckar

2004-01-01

379

FIBER LENGTH DISTRIBUTION MEASUREMENT FOR LONG GLASS AND CARBON FIBER REINFORCED INJECTION MOLDED THERMOPLASTICS  

SciTech Connect

Procedures for fiber length distribution (FLD) measurement of long fiber reinforced injection molded thermoplastics were refined for glass and carbon fibers. Techniques for sample selection, fiber separation, digitization and length measurement for both fiber types are described in detail. Quantitative FLD results are provided for glass and carbon reinforced polypropylene samples molded with a nominal original fiber length of 12.7 mm (1/2 in.) using equipment optimized for molding short fiber reinforced thermoplastics.

Kunc, Vlastimil [ORNL; Frame, Barbara J [ORNL; Nguyen, Ba N. [Pacific Northwest National Laboratory (PNNL); TuckerIII, Charles L. [University of Illinois, Urbana-Champaign; Velez-Garcia, Gregorio [Virginia Polytechnic Institute and State University

2007-01-01

380

Thermoplastic matrix composites for aeronautical applications - The amorphous/semi-crystalline blends option  

NASA Astrophysics Data System (ADS)

Blends obtained by mixing high temperature applications thermoplastics have been investigated. Namely the blends considered in this work are made by semi-crystalline thermoplastics PEEK with amorphous PEI. The final goal is to analyse the mechanical, chemical-physical and environmental resistance characteristics of these blends to evaluate their suitability as matrices of carbon reinforced composites for aeronautical structural applications. The first collected results are very promising.

Iannone, Michele; Esposito, Floriana; Cammarano, Aniello

2014-05-01

381

Highly compatible wood thermoplastic composites from lignocellulosic material modified in ionic liquids: Preparation and thermal properties  

Microsoft Academic Search

A study of converting chemically modified wood into thermoplastic materials was undertaken to de- velop a new technology platform for the effective utiliza- tion of wood-based lignocellulosic materials. Highly substituted benzoylated spruce thermomechanical pulp (TMP) and lauroylated spruce TMP were used as compo- nents for thermoplastic composites of poly(styrene) and poly(propylene). Scanning electron microscopy (SEM), dif- ferential scanning calorimetry (DSC),

Haibo Xie; Paula Jarvi; Mikko Karesoja; Alistair King; Ilkka Kilpelainen; Dimitris S. Argyropoulos

2009-01-01

382

Electrospinning thermoplastic polyurethane-contained collagen nanofibers for tissue-engineering applications.  

PubMed

Electrospinning is a new method used in tissue engineering. It can spin fibers in nanoscale by electrostatic force. A series of thermoplastic polyurethane (TPU)/collagen blend nanofibrous membranes was prepared with different weight ratios and concentrations via electrospinning. The two biopolymers used 1,1,1,3,3,3,-hexafluoro-2-propanol (HFP) as solvent. The electrospun TPU-contained collagen nanofibers were characterized using scanning electron microscopy (SEM), XPS spectroscopy, atomic force microscopy, apparent density and porosity measurement, contact-angle measurement, mechanical tensile testing and viability of pig iliac endothelial cells (PIECs) on blended nanofiber mats. Our data indicate that fiber diameter was influenced by both polymer concentration and blend weight ratio of collagen to TPU. The average diameter of nanofibers gradually decreases with increasing collagen content in the blend. XPS analysis indicates that collagen is found to be present at the surface of blended nanofiber. The results of porosity and contact-angle measurement suggest that with the collagen content in the blend system, the porosity and hydrophilicity of the nanofiber mats is greatly improved. We have also characterized the molecular interactions in TPU/collagen complex by Fourier transform infrared spectroscopy (FT-IR). The result could demonstrate that there were no intermolecular bonds between the molecules of TPU and collagen. The ultimate tensile stress and strain were carried out and the data confirmed the FT-IR results. The TPU/collagen blend nanofibrous mats were further investigated as promising scaffold for PIEC culture. The cell proliferation and SEM morphology observations showed that the cells could not only favorably grow well on the surface of blend nanofibrous mats, but also able to migrate inside the scaffold within 24 h of culture. These results suggest that the blend nanofibers of TPU/collagen are designed to mimic the native extracellular matrix for tissue engineering and develop functional biomaterials. PMID:19619394

Chen, Rui; Qiu, Lijun; Ke, Qinfei; He, Chuanglong; Mo, Xiumei

2009-01-01

383

Modelling of the glass fiber length and the glass fiber length distribution in the compounding of short glass fiber-reinforced thermoplastics  

NASA Astrophysics Data System (ADS)

The use of short glass fiber-reinforced thermoplastics for the production of highly stressed parts in the plastics processing industry has experienced an enormous boom in the last few years. The reasons for this are primarily the improvements to the stiffness and strength properties brought about by fiber reinforcement. These positive characteristics of glass fiber-reinforced polymers are governed predominantly by the mean glass fiber length and the glass fiber length distribution. It is not enough to describe the properties of a plastics component solely as a function of the mean glass fiber length [1]. For this reason, a mathematical-physical model has been developed for describing the glass fiber length distribution in compounding. With this model, it is possible on the one hand to optimize processes for the production of short glass fiber-reinforced thermoplastics, and, on the other, to obtain information on the final distribution, on the basis of which much more detailed statements can be made about the subsequent properties of the molded part. Based on experimental tests, it was shown that this model is able to accurately describe the change in glass fiber length distribution in compounding.

Kloke, P.; Herken, T.; Schöppner, V.; Rudloff, J.; Kretschmer, K.; Heidemeyer, P.; Bastian, M.; Walther, Dridger, A.

2014-05-01

384

Study of thermal stability and degradation of fire resistant candidate polymers for aircraft interiors  

NASA Technical Reports Server (NTRS)

The thermochemistry of bismaleimide resins and phenolphthalein polycarbonate was studied. Both materials are fire-resistant polymers and may be suitable for aircraft interiors. The chemical composition of the polymers has been determined by nuclear magnetic resonance and infrared spectroscopy and by elemental analysis. Thermal properties of these polymers have been characterized by thermogravimetric analyses. Qualitative evaluation of the volatile products formed in pyrolysis under oxidative and non-oxidative conditions has been made using infrared spectrometry. The residues after pyrolysis were analyzed by elemental analysis. The thermal stability of composite panel and thermoplastic materials for aircraft interiors was studied by thermogravimetric analyses.

Hsu, M. T. S.

1976-01-01

385

Self-Healing Polymer Networks  

NASA Astrophysics Data System (ADS)

Supramolecular chemistry teaches us to control non-covalent interactions between organic molecules, particularly through the use of optimized building blocks able to establish several hydrogen bonds in parallel. This discipline has emerged as a powerful tool in the design of new materials through the concept of supramolecular polymers. One of the fascinating aspects of such materials is the possibility of controlling the structure, adding functionalities, adjusting the macroscopic properties of and taking profit of the non-trivial dynamics associated to the reversibility of H-bond links. Applications of these compounds may include adhesives, coatings, rheology additives, high performance materials, etc. However, the synthesis of such polymers at the industrial scale still remains a challenge. Our first ambition is to design supramolecular polymers with original properties, the second ambition is to devise simple and environmentally friendly methods for their industrial production. In our endeavours to create novel supramolecular networks with rubbery elasticity, self-healing ability and as little as possible creep, the strategy to prolongate the relaxation time and in the same time, keep the system flexible was to synthesize rather than a single molecule, an assembly of randomly branched H-bonding oligomers. We propose a strategy to obtain through a facile one-pot synthesis a large variety of supramolecular materials that can behave as differently as associating low-viscosity liquids, semi-crystalline or amorphous thermoplastics, viscoelastic melts or self-healing rubbers.

Tournilhac, Francois

2012-02-01

386

The influence of different screw concepts while processing fibre reinforced thermoplastics with the concept of inline-compounding on an injection moulding machine  

NASA Astrophysics Data System (ADS)

Today, the global market poses major challenges for industrial product development. Complexity, the wide range of variants, flexibility and individuality are just some of the features that products have to fulfil. Product series additionally have shorter and shorter lifetimes. Because of their high capacity for adaptation, polymers are increasingly able to substitute traditional materials such as wood, glass and metals in various fields of application [1]. But polymers can only substitute other materials if they are optimally suited to the applications in question. Hence, product-specific material development is becoming increasingly important [2]. The problem is that the traditional development process for new polymer formulations is much too complex, too slow and therefore too expensive. Product-specific material development is thus out of the question for most processors. Integrating the compounding step in the injection moulding process would lead to a more efficient and faster development process for a new polymer formulation, providing an opportunity to create new product-specific materials. This process is called inline-compounding on an injection moulding machine. In order to develop this innovative formulation concept, with the focus on fibre reinforced thermoplastics, different screw-concepts are compared with regard to the resultant performance characteristics in the part, such as mechanical properties and fibre length distribution.

Moritzer, E.; Müller, E.; Kleeschulte, R.

2014-05-01

387

Photochemical Functionalization of Polymer Surfaces for Microfabricated Devices  

PubMed Central

Herein we report the topochemical modification of polymer surfaces with perfluorinated aromatic azides. The aryl azides, which have quaternary amine or aldehyde functional groups, were linked to the surface of the polymer by UV irradiation. The polymer substrates used in this study were cyclic olefin copolymer (COC) and poly(methylmethacrylate) (PMMA). These substrates were characterized before and after modification, using reflection-absorption infrared spectroscopy (RAIRS), sessile water contact angle measurements, and X-ray photoelectron spectroscopy (XPS). Analysis of the surface confirmed the presence of an aromatic groups with aldehyde or quaternary amine functionality. Enzyme immobilization and patterning onto polymer surfaces were studied using confocal microscopy. Enzymatic digests were carried out on modified probes manufactured from thermoplastic substrates and the resulting peptide analysis was completed using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS).

Mecomber, Justin S.; Murthy, Rajesh S.; Rajam, Sridhar; Singh, Pradeep N. D.; Gudmundsdottir, Anna D.; Limbach, Patrick A.

2012-01-01

388

Combustion of a Polymer (PMMA) Sphere in Microgravity  

NASA Technical Reports Server (NTRS)

A series of low gravity, aircraft-based, experiments was conducted to investigate the combustion of supported thermoplastic polymer spheres under varying ambient conditions. The three types of thermoplastic investigated were polymethylmethacrylate (PMMA), polypropylene (PP). and polystyrene (PS). Spheres with diameters ranging from 2 mm to 6.35 mm were tested. The total initial pressure varied from 0.05 MPa to 0. 15 MPa whereas the ambient oxygen concentration varied from 19 % to 30 % (by volume). The ignition system consisted of a pair of retractable energized coils. Two CCD cameras recorded the burning histories of the spheres. The video sequences revealed a number of dynamic events including bubbling and sputtering, as well as soot shell formation and break-up during combustion of the spheres at reduced gravity. The ejection of combusting material from the burning spheres represents a fire hazard that must be considered at reduced gravity. The ejection process was found to be sensitive to polymer type. All average burning rates were measured to increase with initial sphere diameter and oxygen concentration, whereas the initial pressure had little effect. The three thermoplastic types exhibited different burning characteristics. For the same initial conditions, the burning rate of PP was slower than PMMA, whereas the burning rate of PS was comparable to PMMA. The transient diameter of the burning thermoplastic exhibited two distinct periods: an initial period (enduring approximately half of the total burn duration) when the diameter remained approximately constant, and a final period when the square of the diameter linearly decreased with time. A simple homogeneous two-phase model was developed to understand the changing diameter of the burning sphere. Its value is based on a competition between diameter reduction due to mass loss from burning and sputtering, and diameter expansion due to the processes of swelling (density decrease with heating) and bubble growth. The model relies on empirical parameters for input, such as the burning rate and the duration of the initial and final burning periods.

Yang, Jiann C.; Hamins, Anthony; Donnelly, Michelle K.

1999-01-01

389

Comparison of Piezoresistive Monofilament Polymer Sensors  

PubMed Central

The development of flexible polymer monofilament fiber strain sensors have many applications in both wearable computing (clothing, gloves, etc.) and robotics design (large deformation control). For example, a high-stretch monofilament sensor could be integrated into robotic arm design, easily stretching over joints or along curved surfaces. As a monofilament, the sensor can be woven into or integrated with textiles for position or physiological monitoring, computer interface control, etc. Commercially available conductive polymer monofilament sensors were tested alongside monofilaments produced from carbon black (CB) mixed with a thermo-plastic elastomer (TPE) and extruded in different diameters. It was found that signal strength, drift, and precision characteristics were better with a 0.3 mm diameter CB/TPE monofilament than thick (?2 mm diameter) based on the same material or commercial monofilaments based on natural rubber or silicone elastomer (SE) matrices.

Melnykowycz, Mark; Koll, Birgit; Scharf, Dagobert; Clemens, Frank

2014-01-01

390

Comparison of piezoresistive monofilament polymer sensors.  

PubMed

The development of flexible polymer monofilament fiber strain sensors have many applications in both wearable computing (clothing, gloves, etc.) and robotics design (large deformation control). For example, a high-stretch monofilament sensor could be integrated into robotic arm design, easily stretching over joints or along curved surfaces. As a monofilament, the sensor can be woven into or integrated with textiles for position or physiological monitoring, computer interface control, etc. Commercially available conductive polymer monofilament sensors were tested alongside monofilaments produced from carbon black (CB) mixed with a thermo-plastic elastomer (TPE) and extruded in different diameters. It was found that signal strength, drift, and precision characteristics were better with a 0.3 mm diameter CB/TPE monofilament than thick (~2 mm diameter) based on the same material or commercial monofilaments based on natural rubber or silicone elastomer (SE) matrices. PMID:24419161

Melnykowycz, Mark; Koll, Birgit; Scharf, Dagobert; Clemens, Frank

2014-01-01

391

Thermoplastic Polyurethanes as Carbonization Agents in Intumescent Blends. Part 1: Fire Retardancy of Polypropylene\\/Thermoplastic Polyurethane\\/Ammonium Polyphosphate Blends  

Microsoft Academic Search

This work deals with the fire retardancy of polypropylene (PP)\\/thermoplastic polyurethane (TPU)\\/ammonium polyphosphate (APP) intu mescent blends, using TPU with different chemical compositions and struc tures. The influence of the chemical nature of the polyol used in the synthesis of the TPU on the fire resistance of materials is discussed. Moreover, smoke pro duction from combustion of the blend and

Michel Bugajny; Michel Le Bras; Serge Bourbigot; Franck Poutch; Jean-Marc Lefebvre

1999-01-01

392

Microgravity Polymers  

NASA Technical Reports Server (NTRS)

A one-day, interactive workshop considering the effects of gravity on polymer materials science was held in Cleveland, Ohio, on May 9, 1985. Selected programmatic and technical issues were reviewed to introduce the field to workshop participants. Parallel discussions were conducted in three disciplinary working groups: polymer chemistry, polymer physics, and polymer engineering. This proceedings presents summaries of the workshop discussions and conclusions.

1986-01-01

393

Advanced Polymers  

Microsoft Academic Search

Polymer science gains its power from the infinite versatility of synthetic polymers. Not only the bulk materials but also their basic constituents, polymer molecules, are tailor-made. The polymer molecule is built from smaller molecular units known as monomers, repeated hundreds or thousands of times in a chainlike structure. The choice of monomers and the way they are assembled shape the

Eric Baer

1986-01-01

394

Carbon-fiber surface treatments for improved adhesion to thermoplastic polymers  

SciTech Connect

The effect of anodization in NaOH, H/sub 2/SO/sub 4/, and amine salts on the surface chemistry of carbon fibers was examined by X-ray photoelectron spectroscopy (XPS). The surface of carbon fibers after anodization in NaOH and H/sub 2/SO/sub 4/ were examined by scanning transmission electron microscopy (STEM), angular dependent XPS, ultraviolet (UV) absorption spectroscopy of the anodization bath, secondary ion mass spectrometry, and polar/dispersive surface energy analysis. Hercules AS-4, Dexter Hysol XAS, and Union Carbide T-300 fibers were examined by STEM, angular dependent XPS, and breaking strength measurement before and after commercial surface treatment. The fibers from the three companies were anodized to create a similar surface chemistry on each fiber. XPS was used to compare the surface chemistry after anodization. Adhesion of carbon fibers to polysulfone, polycarbonate, and polyetherimide was studied using the fiber critical length test. Oxygen and nitrogen were added to the fiber surfaces by anodization in amine salts. Analysis of the plasmon peak in the carbon 1s signal indicated that H/sub 2/SO/sub 4/ anodization affected the morphological structure of the carbon-fiber surface.

DeVilbis, T.A. III

1987-01-01

395

A general approach towards thermoplastic multishape-memory polymers via sequence structure design.  

PubMed

The chain sequence of a poly(styrene-co-methyl acrylate) copolymer is designed to form a V-shaped gradient sequence via controlled/living radical emulsion copolymerization. This specially designed chain sequence gives this common copolymer the capacity of multishape memory. The copolymer can sequentially recover to its permanent shape from three or more previously programmed temporary shapes with the stimulus of temperature. PMID:23108904

Luo, Yingwu; Guo, Yunlong; Gao, Xiang; Li, Bo-Geng; Xie, Tao

2013-02-01

396

Microhardness of condensation polymers and copolymers. 2. Poly(ester ether carbonate) thermoplastic terpolymers  

Microsoft Academic Search

The number of phases, transition temperatures, and microhardness of a series of poly(ester ether carbonate) (PEEC) multiblock terpolymers with poly(butylene terephthalate) (PBT) hard segments have been investigated as a function of ether\\/carbonate (EC) soft-segment composition at constant PBT content. The polymerization degree of PBT and the intrinsic viscosity of the terpolymers were determined by viscosimetry. The degree of crystal-Unity, long

F. J. Baltá Calleja; S. Fakirov; Z. Roslaniec; M. Krumova; T. A. Ezquerra; D. R. Rueda

1998-01-01

397

Thermoplastic Starch Films with Vegetable Oils of Brazilian Cerrado  

NASA Astrophysics Data System (ADS)

Biodegradable polymers are one of the most promising ways to replace non-degradable polymers. TPS films were prepared by casting from cassava starch and three different vegetable oils of Brazilian Cerrado as plasticizer: buriti, macaúba and pequi. In this preliminary work it was investigated materials thermal characteristics by TG and TMA. Thermal properties of oils depends on their chemical structures. Starch and vegetable oils are natural resources that can be used how alternative to producing materials that cause minor environmental impact.

Schlemmer, D.; Sales, M. J. A.

2008-08-01

398

Chemical imaging of thermoplastic olefin (TPO) surface architecture  

SciTech Connect

In the automotive industry, ethylene-propylene rubber (EPR) is mixed with polypropylene (PP) to form a thermoplastic olefin (TPO) for use as car bumpers and fascia. An adhesion promoting primer, chlorinated polyolefin (CPO), is spray coated onto the TPO surface to increase adhesion of the base and clear coat paints to the low surface free energy TPO substrate. The surface morphology of rubber domains within the CPO-coated TPO substrate contributes strongly to the material characteristics, including impact resistance and adhesion properties. However, elastomer-phase analysis is challenging using traditional microanalysis imaging techniques. The authors employ fluorescence and Raman chemical imaging to characterize the TPO architecture in order to better understand the surface properties of coated TPO. Fluorescence imaging makes use of Nile red (NR), a fluorescent solvatochromic dye, solvated in the primer, which is effective in differentiating rubber from polypropylene on the basis of large variations in the fluorescence quantum efficiency. Confocal fluorescence chemical imaging performed on T PO coated with NR-doped CPO shows a thin (2--3 {micro}m) layer of elastomer that has migrated to the TPO surface. Raman chemical imaging is in direct agreement with the fluorescence experiments by measuring the intrinsic vibrational signatures of CPO, EPR, and PP without the need for dyes or stains. Raman contrast is enhanced using cosine correlation analysis, a novel multivariate processing technique that provides chemical contrast on the basis of differences in spectral shape.

Morris, H.R. [Duquesne Univ., Pittsburgh, PA (United States). School of Pharmacy] [Duquesne Univ., Pittsburgh, PA (United States). School of Pharmacy; Turner, J.F. II [Carnegie Mellon Univ., Pittsburgh, PA (United States). Center for Light Microscope Imaging and Biotechnology] [Carnegie Mellon Univ., Pittsburgh, PA (United States). Center for Light Microscope Imaging and Biotechnology; Munro, B.; Ryntz, R.A. [Visteon Automotive Systems, Dearborn, MI (United States)] [Visteon Automotive Systems, Dearborn, MI (United States); Treado, P.J. [ChemIcon Inc., Pittsburgh, PA (United States)] [ChemIcon Inc., Pittsburgh, PA (United States)

1999-04-13

399

The development of an alternative thermoplastic powder prepregging technique  

NASA Technical Reports Server (NTRS)

An alternative powder prepregging technique is discussed that is based on the deposition of powder onto carbon fibers that have been moistened using an ultrasonic humidifier. The dry fiber tow is initially spread to allow a greater amount of the fiber surface to be exposed to the powder, thus ensuring a significant amount of intimate contact between the fiber and the matrix. Moisture in the form of ultrafine water droplets is then deposited onto the spread fiber tow. The moisture promotes adhesion to the fiber until the powder can be tacked to the fibers by melting. Powdered resin is then sieved onto the fibers and then tacked onto the fibers by quick heating in a convective oven. This study focuses on the production of prepregs and laminates made with LaRC-TPI (thermoplastic polyimide) using this process. Although the process appears to be successful, early evaluation was hampered by poor interfacial adhesion. The adhesion problem, however, seems to be the result of a material system incompatibility, rather than being influenced by the process.

Ogden, A. L.; Hyer, M. W.; Wilkes, G. L.; Loos, A. C.

1992-01-01

400

Transparent large-strain thermoplastic polyurethane magnetoactive nanocomposites.  

PubMed

Organically modified superparamagnetic MnFe(2)O(4)/thermoplastic polyurethane elastomer (TPU) nanocomposites (0.1-8 wt %) were prepared by solvent mixing followed by solution casting. Linear aliphatic alkyl chain modification of spherical MnFe(2)O(4) provided compatibility with the TPU containing a butanediol extended polyester polyol-MDI. All MnFe(2)O(4)/TPU nanocomposite films were superparamagnetic and their saturation magnetization, ?(s), increased with increasing MnFe(2)O(4) content. All nanocomposite films exhibited large deformations (>10 mm) under a magneto-static field. This is the first report of large actuation of magnetic nanoparticle nanocomposites at low-loading levels of 0.1 wt % (0.025 vol %). The maximum actuation deformation of the MnFe(2)O(4)/TPU nanocomposite films increased exponentially with increasing nanoparticle concentration. An empirical correlation between the maximum displacement, saturation magnetization, and magnetic nanoparticle loading is proposed. The cyclic deformation actuation of a 6 wt % surface modified MnFe(2)O(4)/TPU, in a low magnetic field 151 < B(y) < 303 Oe, exhibited excellent reproducibility and controllability. MnFe(2)O(4)/TPU nanocomposite films (0.1-2 wt %) were transparent and semitransparent over the wavelengths from 350 to 700 nm. PMID:21710967

Yoonessi, Mitra; Peck, John A; Bail, Justin L; Rogers, Richard B; Lerch, Bradley A; Meador, Michael A

2011-07-01

401

Consolidation of graphite thermoplastic textile preforms for primary aircraft structure  

NASA Technical Reports Server (NTRS)

The use of innovative cost effective material forms and processes is being considered for fabrication of future primary aircraft structures. Processes that have been identified as meeting these goals are textile preforms that use resin transfer molding (RTM) and consolidation forming. The Novel Composites for Wing and Fuselage Applications (NCWFA) program has as its objective the integration of innovative design concepts with cost effective fabrication processes to develop damage-tolerant structures that can perform at a design ultimate strain level of 6000 micro-inch/inch. In this on-going effort, design trade studies were conducted to arrive at advanced wing designs that integrate new material forms with innovative structural concepts and cost effective fabrication methods. The focus has been on minimizing part count (mechanical fasteners, clips, number of stiffeners, etc.), by using cost effective textile reinforcement concepts that provide improved damage tolerance and out-of-plane load capability, low-cost resin transfer molding processing, and thermoplastic forming concepts. The fabrication of representative Y spars by consolidation methods will be described. The Y spars were fabricated using AS4 (6K)/PEEK 150g commingled angle interlock 0/90-degree woven preforms with +45-degree commingled plies stitched using high strength Toray carbon thread and processed by autoclave consolidation.

Suarez, J.; Mahon, J.

1991-01-01

402

Microstructure and thermomechanical properties relationship of segmented thermoplastic polyurethane (TPU)  

NASA Astrophysics Data System (ADS)

Thermoplastic polyurethanes (TPU) are important polymeric materials for seals. In competition with Acrylonitrile butadiene rubbers (NBR), TPU exhibits higher strength and a considerable better abrasion resistance. The advantage of NBR over TPU is a smaller compression set but however TPU excels in its much shorter processing cycle times. Generally a TPU is a block copolymer composed of hard and soft segments, which plays an important role in determining the material properties. TPU can be processed either to ready moulded parts or can be incorporated by multi component moulding, in both cases it shows decent mechanical properties. In the present work, the relationship between melt-process induced TPU morphology and resultant thermo mechanical properties were examined and determined by means of quasi-static tensile test, creep experiment, tension test and dynamical mechanical analysis (DMA). Scanning electron beam microscope (SEM) and differential scanning calorimeter (DSC) were used to study the morphology of the samples. A significant mathematical description of the stress-strain behaviour of TPU was found using a 3 term approach. Moreover it became evident that processing conditions such as processing temperature have crucial influence on morphology as well as short and long-term performance. To be more precise, samples processed at higher temperatures showed a lack of large hard segment agglomerates, a smaller strength for strains up to 250% and higher creep compliance.

Frick, Achim; Borm, Michael; Kaoud, Nouran; Kolodziej, Jan; Neudeck, Jens

2014-05-01

403

Investigation the degradation and devulcanization reaction of thermoplastic vulcanizate using peroxide compound  

NASA Astrophysics Data System (ADS)

Investigation the Degradation and Devulcanization Reaction of Thermoplastic Vulcanizate using Peroxide Compound was carried out by means of benzoyl peroxide as a devulcanizing agent. The temperature for the recycling condition was gradually increased from 80°C to 190°C because of the half-life of benzoyl peroxide. Furthermore, the effects of time and concentration of devulcanizing agent on the recycling process were investigated. The extent of devulcanization of thermoplastic vulcanizate was studied by estimation of percent devulcanization, gel fraction of rubber after swelling and crosslink density. According to the results, we found that the crosslink density of devulcanized thermoplastic vulcanizate was 29.37% less than virgin thermoplastic vulcanizate by adding benzoyl peroxide for 1 phr. This result is correspondence to the decreasing in gel fraction of devulcanized thermoplastic vulcanizate. Moreover, the addition of 5 phr and 10 phr to TPVs result to the significant decrement in crosslink density about 64%. The effect of temperature for devulcanization was also investigated to obtain the optimum conditions. The result shows that the percentage of devulcanization was slightly increased as the increasing in the starting temperature from 80°C to 105°C.

Temram, Chokkanit; Wattanakul, Karnthidaporn

2012-09-01

404

Self-Healing Polymers and Composites  

NASA Astrophysics Data System (ADS)

Self-healing polymers and fiber-reinforced polymer composites possess the ability to heal in response to damage wherever and whenever it occurs in the material. This phenomenal material behavior is inspired by biological systems in which self-healing is commonplace. To date, self-healing has been demonstrated by three conceptual approaches: capsule-based healing systems, vascular healing systems, and intrinsic healing polymers. Self-healing can be autonomic—automatic without human intervention—or may require some external energy or pressure. All classes of polymers, from thermosets to thermoplastics to elastomers, have potential for self-healing. The majority of research to date has focused on the recovery of mechanical integrity following quasi-static fracture. This article also reviews self-healing during fatigue and in response to impact damage, puncture, and corrosion. The concepts embodied by current self-healing polymers offer a new route toward safer, longer-lasting, fault-tolerant products and components across a broad cross section of industries including coatings, electronics, transportation, and energy.

Blaiszik, B. J.; Kramer, S. L. B.; Olugebefola, S. C.; Moore, J. S.; Sottos, N. R.; White, S. R.

2010-08-01

405

Large-strain, rigid-to-rigid deformation of bistable electroactive polymers  

Microsoft Academic Search

Thermoplastic poly(tert-butyl acrylate) (PTBA) is reported as an electroactive polymer that is rigid at ambient conditions and turns into a dielectric elastomer above a transition temperature. In the rubbery state, a PTBA thin film can be electrically actuated to strains up to 335% in area expansion. The calculated actuation pressure is 3.2 MPa. The actuation is made bistable by cooling

Zhibin Yu; Wei Yuan; Paul Brochu; Bin Chen; Zhitian Liu; Qibing Pei

2009-01-01

406

Carbon-Fiber Reinforced Plastic Passive Composite Damper by Use of Piezoelectric Polymer\\/Ceramic  

Microsoft Academic Search

In this study, the passive damping of carbon-fiber reinforced plastic (CFRP) cantilever beams is examined using (1) interleaving of viscoelastic thermoplastic films, (2) piezoelectric polymer (PVDF) film interlayers and (3) surface-bonded piezoelectric ceramics. Introducing polyethylene-based film interlayers between composite plies resulted in a significant increase in the vibration loss factor. It is also shown that the vibration damping of CFRP

Toshio Tanimoto

2002-01-01

407

Preparation of cotton linter nanowhiskers by high-pressure homogenization process and its application in thermoplastic starch  

NASA Astrophysics Data System (ADS)

The present work deals with the preparation of cotton linter nanowhiskers (CLNW) by acid hydrolysis and subsequent processing in a high-pressure homogenizer. Prepared CLNW were then used as a reinforcing material in thermoplastic starch (TPS), with an aim to improve its performance properties. Concentration of CLNW was varied as 0, 1, 2, 3, 4 and 5 wt% in TPS. TPS/CLNW nanocomposite films were prepared by solution-casting process. The nanocomposite films were characterized by tensile, differential scanning calorimetry, scanning electron microscopy (SEM), water vapor permeability (WVP), oxygen permeability (OP), X-ray diffraction and light transmittance properties. 3 wt% CLNW-loaded TPS nanocomposite films demonstrated 88 % improvement in the tensile strength as compared to the pristine TPS polymer film; whereas, WVP and OP decreased by 90 and 92 %, respectively, which is highly appreciable compared to the quantity of CLNW added. DSC thermograms of nanocomposite films did not show any significant effect on melting temperature as compared to the pristine TPS. Light transmittance (T r) value of TPS decreased with increased content of CLNW. Better interaction between CLNW and TPS, caused due to the hydrophilic nature of both the materials, and uniform distribution of CLNW in TPS were the prime reason for the improvement in properties observed at 3 wt% loading of CLNW in TPS. However, CLNW was seen to have formed agglomerates at higher concentration as determined from SEM analysis. These nanocomposite films can have potential use in food and pharmaceutical packaging applications.

McClain, Charles R.; Christian, James R.; Signorini, Sergio R.; Lewis, Marlon R.; Asanuma, Ichio; Turk, Daniela; Dupouy-Douchement, Cecile

2014-06-01

408

Characterization of thermoplastic polyurethane/polylactic acid (TPU/PLA) tissue engineering scaffolds fabricated by microcellular injection molding.  

PubMed

Polylactic acid (PLA) and thermoplastic polyurethane (TPU) are two kinds of biocompatible and biodegradable polymers that can be used in biomedical applications. PLA has rigid mechanical properties while TPU possesses flexible mechanical properties. Blended TPU/PLA tissue engineering scaffolds at different ratios for tunable properties were fabricated via twin screw extrusion and microcellular injection molding techniques for the first time. Multiple test methods were used to characterize these materials. Fourier transform infrared spectroscopy (FTIR) confirmed the existence of the two components in the blends; differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) confirmed the immiscibility between the TPU and PLA. Scanning electron microscopy (SEM) images verified that, at the composition ratios studied, PLA was dispersed as spheres or islands inside the TPU matrix and that this phase morphology further influenced the scaffold's microstructure and surface roughness. The blends exhibited a large range of mechanical properties that covered several human tissue requirements. 3T3 fibroblast cell culture showed that the scaffolds supported cell proliferation and migration properly. Most importantly, this study demonstrated the feasibility of mass producing biocompatible PLA/TPU scaffolds with tunable microstructures, surface roughnesses, and mechanical properties that have the potential to be used as artificial scaffolds in multiple tissue engineering applications. PMID:24094186

Mi, Hao-Yang; Salick, Max R; Jing, Xin; Jacques, Brianna R; Crone, Wendy C; Peng, Xiang-Fang; Turng, Lih-Sheng

2013-12-01

409

Microcellular wood-fibre thermoplastic composites: Processing-structure-properties  

NASA Astrophysics Data System (ADS)

In this study, processing-structure-property relationships in foamed wood-fibre plastic composites made with a physical blowing agent were investigated. For the polymers studied, it was found that the crystallinity and morphology have a critical effect on the foaming process. Therefore, an investigation of both semicrystalline and amorphous polymers was conducted. Several amorphous and semicrystalline polymers were selected, based on preliminary experimental results. By non-isothermal crystallisation of the semicrystalline polymers at various cooling rates, specimens with different crystallinities and crystal morphologies were made. The microstructures and sorption properties of these specimens were studied. All the specimens were foamed in a batch process using carbon dioxide as blowing agent and their structures were, investigated. The results showed a great influence of crystallinity and morphology on the solubility and diffusivity of the blowing agent in and through the polymer and especially on the cellular structure of the resulting foams. In contrast to the work of Colton (1989), who suggested that the foaming process should be conducted at a temperature above the melting point, it was shown that by controlling the crystallinity and crystal morphology it is feasible to produce microcellular foams from semicrystalline polymers in the solid state. In the second phase of the study, high density polyethylene and polystyrene were used as the matrices in a foamed wood-fibre composite. Sheets of composites were produced by compounding polymers and fibre. These samples were saturated with carbon dioxide at high pressure and the saturated specimens were foamed at elevated temperatures. Structural analysis and characterisation were performed on both foamed and unfoamed samples. The experimental results showed that the addition of wood fibre had very different effects on the mechanical properties of polystyrene (a glassy polymer) and polyethylene (a semicrystalline ductile polymer). Fibres acted as nucleating agents in the crystallisation of the matrix, and drastically changed the morphology. The impact strength of PS increased when wood fibres were added, while wood fibre diminished the impact strength of PE. The presence of wood fibres significantly changed the microstructure of the composite in the foaming process. Overall, while diminishing the tensile properties (strength and modulus), foaming caused a significant improvement of impact strength of the wood-fibre composites.

Doroudiani, Saeed

410

Characteristics of denture thermoplastic resins for non-metal clasp dentures.  

PubMed

Six thermoplastic resins and conventional acrylic resin were examined to characterize their mechanical and physical properties, water sorption, solubility, flexural strength, modulus of elasticity, tensile strength and color stability. Thermoplastic resins for non-metal clasp dentures exhibiting low water sorption and solubility offer hygienic advantages. Since they have a low modulus of elasticity and are easily manipulated, these materials make it possible for larger undercuts to be used for retention compared to acrylic resin. Not all of the thermoplastic resins tested fractured after the bending test in contrast to the conventional denture base resin, which fractured when tested beyond its proportional limit. It was also found that clinically noticeable staining may occur on the polyamide resins and polyethylene terephtalate resins. PMID:20644329

Takabayashi, Yota

2010-08-01

411

Influence of thickness and undercut of thermoplastic resin clasps on retentive force.  

PubMed

Thermoplastic resin clasps have been used for esthetic denture rehabilitation. However, details of the design of the clasps have never been thoroughly clarified. This study investigated the retentive forces of thermoplastic resin clasps for non-metal clasp dentures. The retentive forces of all thermoplastic resin clasps depended on the elastic modulus of each resin, undercuts, thickness, and widths of the tested. A clasp with more than 0.5 mm undercut and 1.0 mm thickness is needed for Valplast. Similarly, more than 0.25 mm undercut and 1.0 mm thickness and 0.5 mm undercut and 0.5 mm thickness are required for Estheshot and Reigning, respectively; thus, the recommended clasp arm thickness is 1.0 mm to 1.5 mm for Valplast and Estheshot and 0.5 mm to 1.0 mm for Reigning when the width of the retentive arm is 5.0 mm. PMID:23718997

Osada, Hidekazu; Shimpo, Hidemasa; Hayakawa, Tohru; Ohkubo, Chikahiro

2013-01-01

412

Microstructural Characterization of Semi-Interpenetrating Polymer Networks by Positron Lifetime Spectroscopy  

NASA Technical Reports Server (NTRS)

Thermoset and thermoplastic polyimides have complementary physical and mechanical properties. Whereas thermoset polyimides are brittle and generally easier to process, thermoplastic polyimides are tough but harder to process. A combination of these two types of polyimides may help produce polymers more suitable for aerospace applications. Semi-Interpenetrating Polymer Networks (S-IPN) of thermoset LaRC(TM)-RP46 and thermoplastic LaRC(TM)-IA polyimides were prepared in weight percent ratios ranging from 100:0 to 0:100. Positron lifetime measurements were made in these samples to correlate their free volume features with physical and mechanical properties. As expected, positronium atoms are not formed in these samples. The second lifetime component has been used to infer the positron trap dimensions. The 'free volume' goes through a minimum at a ratio of about 50:50, and this suggests that S-IPN samples are not merely solid solutions of the two polymers. These data and related structural properties of the S-IPN samples are discussed.

Singh, Jag J.; Pater, Ruth H.; Eftekhari, Abe

1996-01-01

413

Morphological control of inter-penetrating polymer networks  

NASA Technical Reports Server (NTRS)

Synthetic organic polymer chemistry has been successful in producing composition of matter with thermal oxidation stability and progressively higher glass transition temperatures. In part, this was done by increasing the steric-hindrance of moieties in the chain of a macromolecule. The resulting polymers are usually quite insoluble and produce molten polymers of very high viscosities. These types of polymers are not easily processed into graphite fiber prepregs by melt or solution impregnation methods. Hence, a technological need exists to produce new knowledge of how to produce polymer-fiber composites from this class of polymers. The concept of freeze drying amic-acid prepolymers with reactive thermoplastic was proposed as a research topic for the ASEE/NASA Summer Faculty Program of 1989 as a means of producing polymer-fiber composites. This process scheme has the thermodynamic attribute that the magnitude of phase separation due to differences in solubility of two organic constituents in solution will be greatly reduced by removing a solvent not by evaporation but by sublimation. Progress to date on evaluating this polymer processing concept is briefly outlined.

Hansen, Marion

1989-01-01

414

Chemical Modification and Structure-property Relationships of Acrylic and Ionomeric Thermoplastic Elastomer Gels  

NASA Astrophysics Data System (ADS)

Block copolymers (BCs) have remained at the forefront of materials research due to their versatility in applications ranging from hot-melt/pressure-sensitive adhesives and impact modifiers to compatibilizing agents and vibration-dampening/nanotemplating media. Of particular interest are macromolecules composed of two or more chemically dissimilar blocks covalently linked together to form triblock or pentablock copolymers. If the blocks are sufficiently incompatible and the copolymer behaves as a thermoplastic elastomer, the molecules can spontaneously self-assemble to form nanostructured materials that exhibit shape memory due to the formation of a supramolecular network. The BCs of these types are termed as conventional. When BCs contain blocks having ionic moieties such as sulfonic acid groups, they are termed as block ionomers. Designing new systems based on either conventional or ionic BCs, characterizing their structure-property relationships and later using them as electroacive polymers form the essential objectives of this work. Electroactive polymers (EAPs) exhibit electromechanical actuation when stimulated by an external electric field. In the first part of this work, it is shown that BCs resolve some of the outstanding problems presently encountered in the design of two different classes of EAP actuators: dielectric elastomers (DEs) and ionic polymer metal composites (IPMCs). All-acrylic triblock copolymer gels used as DEs actuate with high efficacy without any requirement of mechanical prestrain and, thus, eliminate the need for bulky and heavy hardware essential with prestrained dielectric actuators, as well as material problems associated with stress relaxation. The dependence of actuation behavior on gel morphology as evaluated from mechanical and microstructure studies is observed. In the case of IPMCs, ionic BCs employed in this study greatly facilitate processing compared to other contenders such as NafionRTM, which is commonly used in this class of EAPs. The unique copolymer investigated here (i) retains its mechanical integrity when highly solvated by polar solvents, (ii) demonstrates a high degree of actuation when tested in a cantilever configuration, and (iii) avoids the shortcomings of back-relaxation/overshoot within the testing conditions when used in combination with an appropriate solvent. In the second part of this work, two chemical strategies to design midblock sulfonated block ionomers are explored. In one case, selective sulfonation of the midblocks in triblock copolymers is achieved via a dioxane:sulfur trioxide chemistry, while in the other acetyl sulfate is used for the same purpose. Excellent control on the degree of sulfonation (DOS) is achieved. The block ionomers swell in different solvents while retaining their mechanical integrity. They show disorder-order, order-order, and order-reduced order morphological transitions as DOS varies. These transitions in morphologies are reflected in their thermal behavior as well. The microstructures show periodicity, which is, again, a function of DOS. The transitions are explained in terms of the molar volume expansion and volume densification of the blocks on sulfonation. The ionic levels, morphology and periodicity in microstructure are important for applications such as actuators, sensors and fuel cell membranes. The ability to tune these aspects in the ionomers designed in this work make them potential candidates for these applications.

Vargantwar, Pruthesh Hariharrao

415

A randomized clinical trial of thermoplastic retainer wear.  

PubMed

The purpose of this study was to determine whether thermoplastic retainers need to be worn full-time for a limited period or whether part-time wear from the outset is adequate to maintain tooth position, arch form, and occlusion. This study was a randomized clinical trail, conducted in a district general hospital. Sixty-two participants were enrolled in the study. Group 1, full-time wear, consisted of 30 patients (12 males and 18 females, aged 13.6 +/- 1.5 years) and group 2, part-time wear, 32 patients (14 males and 18 females, aged 13.8 +/- 1.5 years). Each patient was assigned to one of the groups by random number generation. Clinical records in the form of study models were taken at the start of active treatment (T1), at debond (T2), 6 months into the retention phase (T3), and 1 year post-debond (T4). The irregularity index, intercanine width, intermolar width, arch length, overbite, overjet, and Peer Assessment Rating (PAR) scores were measured on study models using digital callipers. A Mann-Whitney test was used to evaluate the treatment changes within each group. The only statistically significant difference was found to be at T3 and T4 for overbite (P = 0.05 and P = 0.02, respectively). PAR scoring showed more variable changes in group 2. There was good correlation for the measurement method. There was no statistical difference for the two groups for overjet, arch length, intermolar width, intercanine width, and irregularity index at any time point. PMID:19828592

Thickett, E; Power, S

2010-02-01

416

Characterization of elastic-viscoplastic properties of an AS4/PEEK thermoplastic composite  

NASA Technical Reports Server (NTRS)

The elastic-viscoplastic properties of an AS4/PEEK (APC-2) thermoplastic composite were characterized at 24 C (75 F) and 121 C (250 F) by using a one-parameter viscoplasticity model. To determine the strain-rate effects, uniaxial tension tests were performed on unidirectional off-axis coupon specimens with different monotonic strain rates. A modified Bodner and Partom's model was also used to describe the viscoplasticity of the thermoplastic composite. The experimental results showed that viscoplastic behavior can be characterized quite well using the one-parameter overstress viscoplasticity model.

Yoon, K. J.; Sun, C. T.

1991-01-01

417

Thermoplastic nanoclay-modified vulcanizates based on polypropylene and nitrile-butadiene rubber  

NASA Astrophysics Data System (ADS)

Thermoplastic vulcanizates based on polypropylene and nitrile-butadiene rubber, containing modified organoclay were developed. It was shown that composites containing 1 to 5 pbw of Cloisite 15A montmorillonite added to rubber show improved physical-mechanical characteristics. Their swelling degree in AI-92 and motor oil was determined. The swelling degree of composites in petrol and motor oil decreases substantially, by 20-63%, due to the introduction of Cloisite 15A montmorillonite. Modification of thermoplastic vulcanizates using layered silicates raised the degradation onset temperature and decreases weight loss upon high temperature heating.

Volfson, Svetoslav I.; Okhotina, Natalya A.; Nigmatullina, Alina I.; Panfilova, Olga A.

2014-05-01

418

Synthesis of thermoplastic polyurethanes and polyurethane nanocomposites under chaotic mixing conditions  

NASA Astrophysics Data System (ADS)

The self-similar mixing microstructures generated in chaotic mixing of prepolymer and chain extender were utilized to augment conversion and molecular weight in the synthesis of thermoplastic polyurethanes (TPU) and polyurethane nanocomposites. The values of time scales of mixing and chemical reaction were varied so as to obtain the best possible product. The chaotic mixing parameter (theta), catalyst concentration, and chemical structures of polyols and diisocyanates were used as factors to exert influence on the speed of conversion, molecular weight, and phase separation during synthesis. The time to reach maximum torque during mixing and tensile properties of the products were evaluated. In addition, the barrier to diffusion of water vapor through composites of reactive and nonreactive clay particles and pristine polyurethanes was determined. The time scales of reaction and mixing were obtained respectively from the values of kinetic rate constant of the reaction system and Liapunov exponents, the latter characterizes fluid element separation. As a general observation, it was found that best polyurethane products were obtained when the time scale of mixing and the time scale of reaction between -NCO and -OH groups were close to each other. It was found that a value of theta = 1440° with sinusoidal rotor speed variation provided the best mixing condition and the time scale of reaction was gradually shortened using higher concentration of catalysts. In addition, the chaotic mixing protocol with cylindrical rotors produced better products than a mixer formed by a set of commercial neutral kneading discs. The effective shear rate was kept the same in both cases for fair comparison. It was also found that phase separation of hard segments in systems with 38 wt% hard segments limited the maximum value of conversion even though the time scales of mixing and chemical reactions were matched. This indicates that the time scale of phase separation must also be considered in the analysis. Composites of polyurethanes with reactive nanoclay contained micrometer size clay particles. However, they provided significant reduction in water permeation due to alignment of clay particles by chaotic mixing flow. It was found that very little clay-polymer tethering reaction occurred due to strong imbalance in reactivity---the reactivity between prepolymer and butanediol were found to be 25 times faster than those between prepolymer and reactive clay. The knowledge gleaned from the study can be extended to other reactive systems and to designing of continuous chaotic mixing devices.

Jung, Changdo

419

Organosilane Polymers.  

National Technical Information Service (NTIS)

Purified dialkyldichlorosilane monomers were reacted with alkali metals in organic solvent solutions to form linear diorganosilane homopolymers and copolymers. The organosilane polymers were characterized by spectrometric and thermal analysis. Polymer sol...

J. P. Wesson T. C. Williams

1976-01-01

420

Functionalization of polymers using an atmospheric plasma jet in a fluidized bed reactor and the impact on SLM-processes  

NASA Astrophysics Data System (ADS)

In order to improve thermoplastics (e.g. Polyamide, Polypropylene and Polyethylene) for Selective Laser Beam Melting (SLM) processes a new approach to functionalize temperature sensitive polymer powders in a large scale is investigated. This is achieved by combining an atmospheric pressure plasma jet and a fluidized bed reactor. Using pressurized air as the plasma gas, radicals like OH* are created. The functionalization leads to an increase of the hydrophilicity of the treated polymer powder without changing the bulk properties. Using the polymers in a SLM process to build single layers of melted material leads to an improvement of the melted layers.

Sachs, M.; Schmitt, A.; Schmidt, J.; Peukert, W.; Wirth, K.-E.

2014-05-01

421

Space environmental effects on polymer composites: Research needs and opportunities  

NASA Technical Reports Server (NTRS)

The long-term performance of polymer-based composites in the space environment is discussed. Both thermoset and thermoplastic matrix composites are included in this discussion. Previous efforts on the space environmental effects on composites are briefly reviewed. Focus of this review is placed on the effects of hygrothermal stresses, atomic oxygen, ultraviolet (UV), and space debris/micrometeoroid impacts along with the potential synergism. Potential approaches to estimating the residual strength of polymer composites after exposure to atomic oxygen erosion or space debris/micrometeoroid impact are evaluated. New ground-based data are then utilized to illustrate the effects of atomic oxygen and thermal cycling on the failure behavior of polymer composites. Finally, research needs, challenges, and opportunities in the field of space environmental effects on composite materials are highlighted.

Jang, Bor Z.; Bianchi, J.; Liu, Y. M.; Chang, C. P.

1993-01-01

422

SULFUR POLYMER ENCAPSULATION.  

SciTech Connect

Sulfur polymer cement (SPC) is a thermoplastic polymer consisting of 95 wt% elemental sulfur and 5 wt% organic modifiers to enhance long-term durability. SPC was originally developed by the U.S. Bureau of Mines as an alternative to hydraulic cement for construction applications. Previous attempts to use elemental sulfur as a construction material in the chemical industry failed due to premature degradation. These failures were caused by the internal stresses that result from changes in crystalline structure upon cooling of the material. By reacting elemental sulfur with organic polymers, the Bureau of Mines developed a product that successfully suppresses the solid phase transition and significantly improves the stability of the product. SPC, originally named modified sulfur cement, is produced from readily available, inexpensive waste sulfur derived from desulfurization of both flue gases and petroleum. The commercial production of SPC is licensed in the United States by Martin Resources (Odessa, Texas) and is marketed under the trade name Chement 2000. It is sold in granular form and is relatively inexpensive ({approx}$0.10 to 0.12/lb). Application of SPC for the treatment of radioactive, hazardous, and mixed wastes was initially developed and patented by Brookhaven National Laboratory (BNL) in the mid-1980s (Kalb and Colombo, 1985; Colombo et al., 1997). The process was subsequently investigated by the Commission of the European Communities (Van Dalen and Rijpkema, 1989), Idaho National Engineering Laboratory (Darnell, 1991), and Oak Ridge National Laboratory (Mattus and Mattus, 1994). SPC has been used primarily in microencapsulation applications but can also be used for macroencapsulation of waste. SPC microencapsulation has been demonstrated to be an effective treatment for a wide variety of wastes, including incinerator hearth and fly ash; aqueous concentrates such as sulfates, borates, and chlorides; blowdown solutions; soils; and sludges. It is not recommended for treatment of wastes containing high concentrations of nitrates because of potentially dangerous reactions between sulfur, nitrate, and trace quantities of organics. Recently, the process has been adapted for the treatment of liquid elemental mercury and mercury contaminated soil and debris.

KALB, P.

2001-08-22

423

Zoetic polymers  

Microsoft Academic Search

Conditions mediating the formation of biological polymers in situ are reviewed, and terminology suggested to differentiate polymers found in living cells from synthetic materials and polymers derived from biological sources that are modified or studied in a way that obscures their biological function. Methods currently used to characterize the mechanical properties of biopolymer networks in cells are briefly discussed.

Ralph Nossal

2004-01-01

424

Utilizing straw as a filler in thermoplastic building materials  

Microsoft Academic Search

A recent addition to the list of composite building materials is plastic lumber. While utilizing recycled plastics as building materials promotes recycling, plastic lumber itself is a poor replacement for solid wood. Research is underway to improve the mechanical properties of wood\\/polymer composites. This report investigates the use of Willamette Valley rye grass straw as a filler in the commodity

John Simonsen

1996-01-01

425

Functionalized Materials From Elastomers to High Performance Thermoplastics  

Microsoft Academic Search

Synthesis and incorporation of functionalized materials continues to generate significant research interest in academia and in industry. If chosen correctly, a functional group when incorporated into a polymer can deliver enhanced properties, such as adhesion, water solubility, thermal stability, etc. The utility of these new materials has been demonstrated in drug-delivery systems, coatings, membranes and compatibilizers. Two approaches exist to

Laura Ann Salazar

2003-01-01

426

Weathering resistance of halogen-free flame retardance in thermoplastics  

Microsoft Academic Search

The influence of weathering on the fire retardancy of polymers is investigated by means of a cone calorimeter test, before and after artificial weathering. The surface degradation was monitored using different techniques (ATR–FTIR, microscopy, colour measurement). Different kinds of polymeric materials were chosen, all as they are used in practice: polycarbonate (PC) blends, polyamide (PA) and polypropylene (PP) flame-retarded with

U. Braun; V. Wachtendorf; A. Geburtig; H. Bahr; B. Schartel

2010-01-01

427

High-precision flexible fabrication of tissue engineering scaffolds using distinct polymers  

SciTech Connect

Three-dimensional porous structures using biodegradable materials with excellent biocompatibility are critically important for tissue engineering applications. We present a multi-nozzle-based versatile deposition approach to flexibly construct porous tissue engineering scaffolds using distinct polymeric biomaterials such as thermoplastic and photo-crosslinkable polymers. We first describe the development of the deposition system and fabrication of scaffolds from two types of biodegradable polymers using this system. The thermoplastic sample is semi-crystalline poly({var_epsilon}-caprolactone) (PCL) that can be processed at a temperature higher than its melting point and solidifies at room temperature. The photo-crosslinkable one is polypropylene fumarate (PPF) that has to be dissolved in a reactive solvent as a resin for being cured into solid structures. Besides the direct fabrication of thermoplastic PCL scaffolds, we specifically develop a layer molding approach for the fabrication of crosslinkable polymers, which traditionally can only be fabricated by stereolithography. In this approach, a thermoplastic supporting material (paraffin wax) is first deposited to make a mold for each specific layer, and then PPF is deposited on demand to fill the mold and cured by the UV light. The supporting material can be removed to produce a porous scaffold of crosslinked PPF. Both PCL and crosslinked PPF scaffolds fabricated using the developed system have been characterized in terms of compressive mechanical properties, morphology, pore size and porosity. Mouse MC3T3-E1 pre-osteoblastic cell studies on the fabricated scaffolds have been performed to demonstrate their capability of supporting cell proliferation and ingrowth, aiming for bone tissue engineering applications.

Wei, Chuang [North Carolina State University; Cai, Lei [ORNL; Sonawane, Bhushan [North Carolina State University; Wang, Shanfeng [ORNL; Dong, Jingyan [North Carolina State University

2012-01-01

428

Structure-morphology-rheology relationships in thermoplastic polyurethanes  

NASA Astrophysics Data System (ADS)

The effect of thermal history on the phase transitions, morphology, and rheological behavior of six thermoplastic polyurethanes (TPUs) with varying contents of hard segment, each having 4,4'-methylene bis(phenyl isocyanate) and 1,4-butane diol as hard segment and poly(epsilon-caprolactone) diol as soft segment was investigated using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), fourier-transform infrared (FTIR) spectroscopy, and polarizing optical microscopy (POM). Specifically, we conducted dynamic frequency sweep experiments at various temperatures for all six TPUs synthesized, as well as isochronal temperature sweep experiments using the parallel-plate fixture of a cone-and-plate rheometer. In the dynamic frequency sweep experiments, the initial morphology was controlled by heating a specimen to a temperature above the isotropization temperature (Ti) of the hard segment, and then slowly cooled the sample down to a predetermined temperature below the Ti of each TPU specimen. Initial DSC experiments provided information on thermal transition temperatures of each TPU specimen. The rheological measurements are interpreted with the aid of the images from polarized optical microscopy taken under the same thermal histories employed as for the rheological measurements. It was found that thermal history of specimen (L3) had a profound influence on the variations of storage modulus (G ') and loss modulus (G?) with time observed during isothermal annealing, based upon the structural development of spherulitic superstructure of hard segment. The differences in the rheological behavior observed among the different TPUs synthesized in this study are further interpreted with the aid of Fourier transform infrared spectra obtained at various temperatures. It is concluded that hydrogen bonding has a profound influence on the time variations of rheological behavior during measurements. Finally, we have investigated time variations of G ' obtained during isochronal dynamic temperature sweep experiments. It has been observed that values of G' for a TPU specimen having low content of hard segments decrease gradually with increasing temperature, whereas values of G' for a TPU specimen having high content of hard segments decrease rapidly at a critical temperature, which is very close to the melting temperature of the microcrystallites in the hard segment. It is concluded that the determination of the microphase-separation temperature of multi-segmented TPUs is very difficult, if not impossible, owing to the existence of mixed phases consisting of hard and soft segments, making the phase interface much diffused.

Youn, Yeo-O.

429

Bursting Bubbles from Combustion of Thermoplastic Materials in Microgravity  

NASA Technical Reports Server (NTRS)

Many thermoplastic materials in common use for a wide range of applications, including spacecraft, develop bubbles internally as they burn due to chemical reactions taking place within the bulk. These bubbles grow and migrate until they burst at the surface, forceably ejecting volatile gases and, occasionally, molten fuel. In experiments in normal gravity, Kashiwagi and Ohlemiller observed vapor jets extending a few centimeters from the surface of a radiatively heated polymethylmethacrylate (PMMA) sample, with some molten material ejected into the gas phase. These physical phenomena complicated the combustion process considerably. In addition to the non-steady release of volatiles, the depth of the surface layer affected by oxygen was increased, attributed to the roughening of the surface by bursting events. The ejection of burning droplets in random directions presents a potential fire hazard unique to microgravity. In microgravity combustion experiments on nylon Velcro fasteners and on polyethylene wire insulation, the presence of bursting fuel vapor bubbles was associated with the ejection of small particles of molten fuel as well as pulsations of the flame. For the nylon fasteners, particle velocities were higher than 30 cm/sec. The droplets burned robustly until all fuel was consumed, demonstrating the potential for the spread of fire in random directions over an extended distance. The sequence of events for a bursting bubble has been photographed by Newitt et al.. As the bubble reaches the fluid surface, the outer surface forms a dome while the internal bubble pressure maintains a depression at the inner interface. Liquid drains from the dome until it breaks into a cloud of droplets on the order of a few microns in size. The bubble gases are released rapidly, generating vortices in the quiescent surroundings and transporting the tiny droplets. The depression left by the escaping gases collapses into a central jet, which rises with a high velocity and may break up, releasing one or more relatively large drops (on the order of a millimeter in these experiments). A better understanding of bubble development and bursting processes, the effects of bursting behavior on burning rate of the bulk material, and the circumstances under which large droplets are expelled, as well as their trajectories, sizes, and burning rates, is sought through computer modeling compared with experiment.

Butler, K. B.

1999-01-01

430

Production of natural fiber reinforced thermoplastic composites through the use of polyhydroxybutyrate-rich biomass  

Microsoft Academic Search

Previous research has demonstrated that production of natural fiber reinforced thermoplastic composites (NFRTCs) utilizing bacterially-derived pure polyhydroxybutyrate (PHB) does not yield a product that is cost competitive with synthetic plastic-based NFRTCs. Moreover, the commercial production of pure PHB is not without environmental impacts. To address these issues, we integrated unpurified PHB in NFRTC construction, thereby eliminating a significant energy and

Erik R. Coats; Frank J. Loge; Michael P. Wolcott; Karl Englund; Armando G. McDonald

2008-01-01

431

Thermal and dynamic mechanical characterization of thermoplastic polyurethane\\/organoclay nanocomposites prepared by melt compounding  

Microsoft Academic Search

Thermoplastic polyurethane (TPU) nanocomposites based on organically modified layered silicate (OMLS) were prepared by melt intercalation process followed by compression molding. Different percentage of organoclays was incorporated into the TPU matrix in order to examine the influence of the nanoscaled fillers on nanostructure morphology and material properties. The microscopic morphology of the nanocomposites was evaluated by wide angle X-ray diffraction

A. K. Barick; D. K. Tripathy

2010-01-01

432

Preparing composite materials from matrices of processable aromatic polyimide thermoplastic blends  

NASA Technical Reports Server (NTRS)

Composite materials with matrices of tough, thermoplastic aromatic polyimides are obtained by blending semi-crystalline polyimide powders with polyamic acid solutions to form slurries, which are used in turn to prepare prepregs, the consolidation of which into finished composites is characterized by excellent melt flow during processing.

Johnston, Norman J. (inventor); St.clair, Terry L. (inventor); Baucom, Robert M. (inventor); Gleason, John R. (inventor)

1991-01-01

433

Model predictive control of a twin-screw extruder for thermoplastic vulcanizate (TPV) applications  

Microsoft Academic Search

This paper deals with the design and experimental study of a model predictive controller (MPC) for the regulation of the melt temperature (MT) and the motor load (ML) in a pilot plant co-rotating twin-screw extruder for thermoplastic vulcanizate (TPV) applications. It is shown that these two process variables have significant influence on the crosslinking of the rubber chains by initiation

M. Trifkovic; M. Sheikhzadeh; K. Choo; S. Rohani

434

Chemical-Assisted Bonding of Thermoplastics/Elastomer for Fabricating Microfluidic Valves  

PubMed Central

Thermoplastics such as cyclic olefin copolymer (COC) and polymethylmethacrylate (PMMA) have been increasingly used in fabricating microfluidic devices. However, the state-of-the-art microvalve technology is a polydimethylsiloxane (PDMS)-based three-layer structure. In order to integrate such a valve with a thermoplastics-based microfluidic device, a bonding method for thermoplastics/PDMS must be developed. We report here a method to bond COC with PDMS through surface activation by corona discharge, surface modification using 3-(trimethoxysilyl)propyl methacrylate (TMSPMA), and thermal annealing. The method is also applicable to PMMA. The bonding strength between thermoplastics and PDMS was represented by the peeling force, which was measured using a method established by the International Organization for Standardization (ISO). The bonding strength measurement offered an objective and quantitative indicator for protocol optimization, as well as comparison with other PDMS-associated bonding methods. Using optimized bonding conditions, two valve arrays were fabricated in a COC/PDMS/COC device and cyclic operations of valve closing/opening were successfully demonstrated. The valve-containing devices withstood 100 psi (~689 KPa) without delamination. Further, we integrated such valve arrays in a device for protein separation and demonstrated isoelectric focusing in the presence of valves.

Gu, Pan; Liu, Ke; Chen, Hong; Nishida, Toshikazu; Fan, Z. Hugh

2010-01-01

435

Crystallinity Effects on Fracture of Rings Made of Thermoplastic Powder Impregnated Carbon or Glass Fiber Composites  

Microsoft Academic Search

Effects of the supermolecular structure of a thermoplastic matrix on the flexural response of glass (GF) or carbon fiber (CF)\\/polyamide 12 (PA 12) composite rings were investigated. An additional attempt was made to determine their interlaminar mode I fracture energy. Specimen rings were prepared by dry winding of carbon or glass fibers bundles, interspersed with polyamide powder and surrounded by

M. Evstatiev; K. Friedrich; S. Fakirov

1993-01-01

436

Surface friction effects related to pressforming of continuous fibre thermoplastic composites  

Microsoft Academic Search

In the pressforming of thermoplastic composite sheet, the heated laminate is rapidly formed into a mould. The moulding force is transmitted using either matched metal dies or by a rubber pad\\/metal mould combination. Friction must occur between the metal or rubber mould surface and the heated composite as the laminate moves across the tool surface until it is fully formed.

Adrian M. Murtagh; John J. Lennon; Patrick J. Mallon

1995-01-01

437

SENSITIVITY STUDIES FOR IN-SITU AUTOMATED TAPE PLACEMENT OF THERMOPLASTIC COMPOSITES  

Microsoft Academic Search

This modeling effort seeks to improve the interlaminate bond strength of thermoplastic carbon composites produced by the in-situ automated tape placement (ATP) process. An existing high productivity model is extended to lower values of the Peclet number that correspond to the present operating conditions of the Langley ATP robot. (The Peclet number is the dimensionless ratio of inertial to diffusive

Robert C. Costen; Joseph M. Marchello

438

Microcellular foams of thermoplastic vulcanizates (TPVs) based on waste ground rubber tire powder  

Microsoft Academic Search

With the increased adoption of thermoplastic vulcanizates (TPVs) in automotive weather seal systems, the foams of TPVs present an important milestone in providing key applications such as trunk and door seals. In this study, microcellular foams of TPV based on waste ground rubber tire powder (WGRT) were investigated. In order to investigate the relationship between processing conditions and structure of

Zhen Xiu Zhang; Shu Ling Zhang; Sung Hyo Lee; Dong Jin Kang; Jin Kuk Kim

2008-01-01

439

Properties of thermoplastic composites with cotton and guayule biomass residues as fiber fillers  

Microsoft Academic Search

This study was conducted to evaluate the suitability of using residual plant fibers from agricultural waste streams as reinforcement in thermoplastic composites. Three groups of plant fibers evaluated included cotton burrs, sticks and linters from cotton gin waste (CGW), guayule whole plant, and guayule bagasse. The plant fibers were characterized for physical (bulk density and particle size distribution) and chemical

Sreekala G. Bajwa; Dilpreet S. Bajwa; Greg Holt; Terry Coffelt; Francis Nakayama

2011-01-01

440

Preparation and properties of starch thermoplastics modified with waterborne polyurethane from renewable resources  

Microsoft Academic Search

A waterborne polyurethane (PU) aqueous dispersion was synthesized from castor oil, and blended with thermoplastic starch (TPS) to obtain a novel biodegradable plastic with improved physical properties. The effect of PU content on the morphology, miscibility and physical properties of the resulting blends was well investigated by scanning electron microscopy, differential scanning calorimetry, dynamic mechanical thermal analysis and measurements of

Yongshang Lu; Lan Tighzert; Patrice Dole; Damien Erre

2005-01-01

441

Thermoplastic elastomers based on polypropylene\\/natural rubber and polypropylene\\/recycle rubber blends  

Microsoft Academic Search

Fine rubber powder obtained from the sanding process of polishing rubber balls and artificial eggs (recycled rubber, RR) was used to prepare polypropylene (PP)\\/RR blends, a thermoplastic elastomer using different RR content. A similar series of blends using natural rubber, SMR L (NR) was also prepared. The results indicated that at a similar rubber content, PP\\/RR blends have higher, tensile

H Ismail; Suryadiansyah

2002-01-01

442

Correction of the measurement of fiber length of short fiber reinforced thermoplastics  

Microsoft Academic Search

Short fiber reinforced thermoplastics are often made using extrusion compounding and injection moulding techniques. Fiber breakage takes place during processing. In finished fiber reinforced parts, there often exists a fiber length distribution. Measurement of fiber length is often performed on photographs of short fibers obtained from burning off or dissolving the matrix. However, relatively long fibers crossing the photographs cannot

Shao-Yun Fu; Yiu-Wing Mai; Emma Chui-Yee Ching; Robert K. Y Li

2002-01-01

443

Preparation and characterization of wheat straw fibers for reinforcing application in injection molded thermoplastic composites  

Microsoft Academic Search

The potential of wheat straw fibers prepared by mechanical and chemical processes as reinforcing additives for thermoplastics was investigated. Fibers prepared by mechanical and chemical processes were characterized with respect to their chemical composition, morphology, and physical, mechanical and thermal properties. Composites of polypropylene filled with 30% wheat straw fibers were prepared and their mechanical properties were also evaluated. The

S. Panthapulakkal; A. Zereshkian; M. Sain

2006-01-01

444

Thermoplastic rubber comprising ethylene-vinyl acetate copolymer, asphalt and fluxing oil  

NASA Technical Reports Server (NTRS)

A thermoplastic rubber is made from a mixture of between about 10 percent and about 50 percent of asphalt, between about 5 percent and about 30 percent fluxing oil, and between about 35 percent and about 70 percent of a copolymer of polyethylene and vinyl acetate.

Hendel, F. J. (inventor)

1970-01-01

445

Evaluation of a Thermoplastic Immobilization System for Breast and Chest Wall Radiation Therapy  

SciTech Connect

We report on the impact of a thermoplastic immobilization system on intra- and interfraction motion for patients undergoing breast or chest wall radiation therapy. Patients for this study were treated using helical tomotherapy. All patients were immobilized using a thermoplastic shell extending from the shoulders to the ribcage. Intrafraction motion was assessed by measuring maximum displacement of the skin, heart, and chest wall on a pretreatment 4D computed tomography, while inter-fraction motion was inferred from patient shift data arising from daily image guidance procedures on tomotherapy. Using thermoplastic immobilization, the average maximum motion of the external contour was 1.3 {+-} 1.6 mm, whereas the chest wall was found to be 1.6 {+-} 1.9 mm. The day-to-day setup variation was found to be large, with random errors of 4.0, 12.0, and 4.5 mm in the left-right, superior-inferior, and anterior-posterior directions, respectively, and the standard deviations of the systematic errors were found to be 2.7, 9.8, and 4.1 mm. These errors would be expected to dominate any respiratory motion but can be mitigated by daily online image guidance. Using thermoplastic immobilization can effectively reduce respiratory motion of the chest wall and external contour, but these gains can only be realized if daily image guidance is used.

Strydhorst, Jared H. [Ottawa Hospital Cancer Centre, Ottawa (Canada); Department of Physics, Carleton University, Ottawa (Canada); Caudrelier, Jean-Michel [Ottawa Hospital Cancer Centre, Ottawa (Canada); Department of Radiology, University of Ottawa, Ottawa (Canada); Clark, Brenda G. [Ottawa Hospital Cancer Centre, Ottawa (Canada); Department of Physics, Carleton University, Ottawa (Canada); Department of Radiology, University of Ottawa, Ottawa (Canada); Montgomery, Lynn A.; Fox, Greg [Ottawa Hospital Cancer Centre, Ottawa (Canada); MacPherson, Miller S., E-mail: mmacpherson@cvh.on.c [Ottawa Hospital Cancer Centre, Ottawa (Canada); Department of Radiology, University of Ottawa, Ottawa (Canada); Department of Radiation Oncology, University of Toronto, Toronto (Canada); Radiation Medicine Program, Princess Margaret Hospital, Toronto (Canada)

2011-04-01

446

PROCESSING AND CHARACTERIZATION OF WELDED BONDS BETWEEN THERMOSET AND THERMOPLASTIC COMPOSITES  

EPA Science Inventory

To assemble complex structures with short cycle times, the feasibility of welding thermoplastic (TP) to thermoset (TS) composites is demonstrated using a phenomenological approach. The effect of the thermal degradation of the TS composite (AS4/3501-6) on its shear strength is ass...

447

Fatigue damage model for injection-molded short glass fibre reinforced thermoplastics  

Microsoft Academic Search

The present paper is a contribution to the phenomenological modelling of fatigue non-linear cumulative diffuse damage in short glass fibre reinforced thermoplastic matrix composites. In such materials, fatigue damage kinetic exhibits three stages, namely: (i) material softening and damage initiation, (ii) coalescence and propagation of micro-cracks and (iii) macroscopic cracks propagation and material failure. The proposed model is built in

H. Nouri; F. Meraghni; P. Lory

2009-01-01

448

Micromechanical modeling of short glass-fiber reinforced thermoplastics-Isotropic damage of pseudograins  

Microsoft Academic Search

A micromechanical damage modeling approach is presented to predict the overall elasto-plastic behavior and damage evolution in short fiber reinforced composite materials. The practical use of the approach is for injection molded thermoplastic parts reinforced with short glass fibers. The modeling is proceeded as follows. The representative volume element is decomposed into a set of pseudograins, the damage of which

S. Kammoun; L. Brassart; G. Robert; I. Doghri; L. Delannay

2011-01-01

449

Synthesis of thermoplastic elastomers based on PET glycolysates: Study of their dielectric properties  

Microsoft Academic Search

Thermoplastic elastomers based on PET glycolysates were synthesized in the molten state according to a multistep process. Their chemical structures were studied (1H NMR, triple detection, steric exclusion chromatography) as well as their thermal properties (ATG, DSC) and their morphology (AFM). Influence of hard segments composition on the different properties was investigated with the same