Effect of molecular weight on polyphenylquinoxaline properties

NASA Technical Reports Server (NTRS)

Jensen, Brian J.

1991-01-01

A series of polyphenyl quinoxalines with different molecular weight and end-groups were prepared by varying monomer stoichiometry. Thus, 4,4'-oxydibenzil and 3,3'-diaminobenzidine were reacted in a 50/50 mixture of m-cresol and xylenes. Reaction concentration, temperature, and stir rate were studied and found to have an effect on polymer properties. Number and weight average molecular weights were determined and correlated well with viscosity data. Glass transition temperatures were determined and found to vary with molecular weight and end-groups. Mechanical properties of films from polymers with different molecular weights were essentially identical at room temperature but showed significant differences at 232 C. Diamine terminated polymers were found to be much less thermooxidatively stable than benzil terminated polymers when aged at 316 C even though dynamic thermogravimetric analysis revealed only slight differences. Lower molecular weight polymers exhibited better processability than higher molecular weight polymers.

Environmental isolation task

NASA Technical Reports Server (NTRS)

Coulbert, C. D.

1982-01-01

The failure-analysis process was organized into a more specific set of long-term degradation steps so that material property change can be differentiated from module damage and module failure. Increasing module performance and life are discussed. A polymeric aging computer model is discussed. Early detection of polymer surface reactions due to aging is reported.

Approaches to New Endcaps for Improved Oxidation Resistance

NASA Technical Reports Server (NTRS)

Meador, Mary Ann B.; Frimer, Aryeh A.

1999-01-01

Norbornenyl-end capped PMR polyimide resins are widely used as polymer matrix composite materials for aircraft engine applications, since they combine ease of processing with good oxidative stability up to 300 C. PMR resins are prepared by a two-step approach involving the initial formation of oligomeric pre-polymers capped at both ends by a latent reactive end cap. The end cap undergoes cross-linking during higher temperature processing, producing the desired low density, high specific strength materials, for PMR- 15. The end cap facilitates processing by controlling the molecular weight of the oligomer and allowing flow before it cross-links. However, after cross-linking, this very end cap accounts for much of the weight loss in the polymer on aging in air at elevated temperatures. Understanding this degradation provides clues for designing new end caps to slow down degradation, and prolong the lifetime of the material.

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

NASA Technical Reports Server (NTRS)

Willis, P. B.

1985-01-01

The historical development of ethylene vinyl acetate (EVA) is presented, including the functional requirements, polymer selection, curing, stabilization, production and module processing. The construction and use of a new method for the accelerated aging of polymers is detailed. The method more closely resembles the conditions that may be encountered in actual module field exposure and additionally may permit service life to be predicted accurately. The use of hardboard as a low cost candidate substrate material is studied. The performance of surface antisoiling treatments useful for imparting a self cleaning property to modules is updated.

Evaluation of the effect of organic pro-degradant concentration in polypropylene exposed to the natural ageing

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

Montagna, L. S., E-mail: larissambiental@yahoo.com.br, E-mail: andrecatto@terra.com.br, E-mail: katiandry@hotmail.com, E-mail: mmcforte@hotmail.com, E-mail: ruth.santana@ufrgs.br; Catto, A. L., E-mail: larissambiental@yahoo.com.br, E-mail: andrecatto@terra.com.br, E-mail: katiandry@hotmail.com, E-mail: mmcforte@hotmail.com, E-mail: ruth.santana@ufrgs.br; Rossini, K., E-mail: larissambiental@yahoo.com.br, E-mail: andrecatto@terra.com.br, E-mail: katiandry@hotmail.com, E-mail: mmcforte@hotmail.com, E-mail: ruth.santana@ufrgs.br

The production and consumption of plastics in the last decade has recorded a remarkable increase in the scientific and industrial interest in environmentally degradable polymer (EDPs). Polymers wastes are deposited improperly, such as dumps, landfills, rivers and seas, causing a serious problem by the accumulation in the environment. The abiotic processes, like the photodegradation, are the most efficient occurring in the open environmental, where the polymers undergo degradation from the action of sunlight that result from direct exposure to solar radiation, however depend of the type of chemical ageing, which is the principal component of climatic ageing. The subject ofmore » this work is to study the influence of concentration of organic pro-degradant (1, 2 and 3 % w/w) in the polypropylene (PP) exposed in natural ageing. PP samples with and without the additive were processed in plates square form, obtained by thermal compression molding (TCM) using a press at 200°C under 2 tons for 5 min, and then were exposed at natural ageing during 120 days. The presence of organic additive influenced on PP degradability, this fact was assessed by changes in the thermal and morphology properties of the samples after 120 days of natural ageing. Scanning Electronic Microscopy (SEM) results of the morphological surface of the modified PP samples showed greater degradation photochemical oxidative when compared to neat PP, due to increase of rugosity and formation of microvoids. PP samples with different pro-degradant concentration under natural ageing presented a degree of crystallinity, obtained by Differential Scanning Calorimeter (DSC) increases in comparing the neat PP.« less

Interplay between Shear Loading and Structural Aging in a Physical Gelatin Gel

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

Ronsin, O.; Caroli, C.; Baumberger, T.

2009-09-25

We show that the aging of the mechanical relaxation of a gelatin gel exhibits the same scaling phenomenology as polymer and colloidal glasses. In addition, gelatin is known to exhibit logarithmic structural aging (stiffening). We find that stress accelerates this process. However, this effect is definitely irreducible to a mere age shift with respect to natural aging. We suggest that it is interpretable in terms of elastically aided elementary (coil->helix) local events whose dynamics gradually slows down as aging increases geometric frustration.

Polymer-Oxygen Compatibility Testing: Effect of Oxygen Aging on Ignition and Combustion Properties

NASA Technical Reports Server (NTRS)

Waller, Jess M.; Haas, Jon P.; Wilson, D. Bruce; Fries, Joseph (Technical Monitor)

2000-01-01

The oxygen compatibility of six polymers used in oxygen service was evaluated after exposure for 48 hours to oxygen pressures ranging from 350 to 6200 kPa (50 to 900 psia), and temperatures ranging from 50 to 250 C (122 to 302 F). Three elastomers were tested: CR rubber (C873-70), FKM fluorocarbon rubber (Viton A), and MPQ silicone rubber (MIL-ZZ-765, Class 2); and three thermoplastics were tested: polyhexamethylene adipamide (Zytel 42), polytetrafluoroethylene (Teflon TFE), and polychlorotrifluoroethylene (Neoflon CTFE M400H). Post-aging changes in mass, dimensions, tensile strength, elongation at break, and durometer hardness were determined. Also, the compression set was determined for the three elastomers. Results show that the properties under investigation were more sensitive to oxygen pressure at low to moderate temperatures, and more sensitive to temperature at low to moderate oxygen pressures. Inspection of the results also suggested that both chain scissioning and cross-linking processes were operative, consistent with heterogeneous oxidation. Attempts are underway to verify conclusively the occurrence of heterogeneous oxidation using a simple modulus profiling technique. Finally, the effect of aging at 620 kpa (90 psia) and 121 C (250 F) on ignition and combustion resistance was determined. As expected, aged polymers were less ignitable and combustible (had higher AlTs and lower heats of combustion). Special attention was given to Neoflon CTFE. More specifically, the effect of process history (compression versus extrusion molding) and percent crystallinity (quick- versus slow-quenched) on the AIT, heat of combustion, and impact sensitivity of Neoflon CTFE was investigated. Results show the AIT, heat of combustion, and impact sensitivity to be essentially independent of Neoflon CTFE process history and structure.

Semi-2-interpenetrating polymer networks of high temperature systems

NASA Technical Reports Server (NTRS)

Hanky, A. O.; St. Clair, T. L.

1985-01-01

A semi-interpenetrating (semi-IPN) polymer system of the semi-2-IPN type is described in which a polymer of acetylene-terminated imidesulfone (ATPISO2) is cross linked in the presence of polyimidesulfone (PISO2). Six different formulations obtained by mixing of either ATPISO2-1n or ATPISO2-3n with PISO2 in three different proportions were characterized in terms of glass transition temperature, thermooxidative stability, inherent viscosity, and dynamic mechanical properties. Adhesive (lap shear) strength was tested at elevated temperatures on aged samples of adhesive scrim cloth prepared from each resin. Woven graphite (Celion 1000)/polyimide composites were tested for flexural strength, flexural modulus, and shear strength. The network polymers have properties intermediate between those of the component polymers alone, have greatly improved processability over either polyimide, and are able to form good adhesive bonds and composites, making the semi-2-IPN systems superior materials for aerospace structures.

Protection of alodine coatings from thermal aging by removable polymer coatings.

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

Wagstaff, Brett R.; Bradshaw, Robert W.; Whinnery, LeRoy L., Jr.

2006-12-01

Removable polymer coatings were evaluated as a means to suppress dehydration of Alodine chromate conversion coatings during thermal aging and thereby retain the corrosion protection afforded by Alodine. Two types of polymer coatings were applied to Alodine-treated panels of aluminum alloys 7075-T73 and 6061-T6 that were subsequently aged for 15 to 50 hours at temperatures between 135 F to 200 F. The corrosion resistance of the thermally aged panels was evaluated, after stripping the polymer coatings, by exposure to a standard salt-fog corrosion test and the extent of pitting of the polymer-coated and untreated panels compared. Removable polymer coatings mitigatedmore » the loss of corrosion resistance due to thermal aging experienced by the untreated alloys. An epoxide coating was more effective than a fluorosilicone coating as a dehydration barrier.« less

Enhancing the quality of aged latent fingerprints developed by superglue fuming: loss and replenishment of initiator.

PubMed

Wargacki, Stephen P; Lewis, Linda A; Dadmun, Mark D

2008-09-01

The recovery and identification of latent fingerprints from a crime scene are crucial to many investigations. The cyanoacrylate (superglue) fuming method (CFM), which develops fingerprints by growing a polymer coating over the print residue, is a powerful method but encounters severe limitations when prints are aged or exposed to harsh environmental conditions. We examine the aging process and how the changes that occur to a fingerprint residue over time influence the growth of polymer during development. We identify loss of initiator by erosion and degradation that, when coupled with a loss of water from the print residue, result in a decreased ability to polymerize ethylcyanoacrylate. Then, we present a methodology by which the ability of aged latent fingerprints to polymerize ethylcyanoacrylate is recovered. Two print enhancement agents, acetic acid and ammonia, are demonstrated to improve the growth of polymer from the print ridges by over an order of magnitude, while retaining the integrity of the print structure. Comparison between the two enhancement agents indicate that the enhancement occurs due to ridge coating by the ammonia or acetic acid and pH control of the latent print.

Effect of Filler Concentration on Thermal Stability of Vinyl Copolymer Elastomer (VCE) Composites

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

Yang, Dali; Hubbard, Kevin Mark; Devlin, David James

To study the thermal stability of vinyl copolymer elastomer (VCE) in its composite form, systematic TGA characterizations were conducted in both nonisothermal and isothermal modes. The effects of filler concentration on the aging behaviors of the VCE/filler composites were investigated under nitroplasticizer (NP) environment. FTIR characterization was used to probe the structural changes in the VCE polymer before and after the thermal treatments. This study suggests that the filler concentration significantly deteriorates the thermal stability of NP at a moderate temperature (< 70 °C). The degradation of NP, in turn, accelerates the aging process of the VCE polymer in itsmore » composite form.« less

Ultrastructure Processing and Characterization of Polymers

DTIC Science & Technology

1988-01-01

Eur. Polym. J . 24, 123-127 (1988) (with R. Vukovic , G. Bogdanic, V. Kuresevic, and W.J. MacKnight) "Miscibility and Phase Behavior in Poly (2,6...Month, Day) |I5 fAGE U d FINAL FROM TO j -"_ 16. SUPPLEMENTARY NOTATION 17. COSATI CODES 18. SUBJECT TERMS (Continue on reverse if necessary and...Lee Dr. J . Obrzut Dr. D. Rice Dr. J . Schlenoff Dr. J . Shim V. JUNIOR RESEARCH PERSONNEL: M. Bishop R. Gregorius M. Lux J . Machado M. Masse R

Predictive aging of polymers

NASA Technical Reports Server (NTRS)

Cuddihy, Edward F. (Inventor); Willis, Paul B. (Inventor)

1989-01-01

A method of predicting aging of polymers operates by heating a polymer in the outdoors to an elevated temperature until a change of property is induced. The test is conducted at a plurality of temperatures to establish a linear Arrhenius plot which is extrapolated to predict the induction period for failure of the polymer at ambient temperature. An Outdoor Photo Thermal Aging Reactor (OPTAR) is also described including a heatable platen for receiving a sheet of polymer, means to heat the platen, and switching means such as a photoelectric switch for turning off the heater during dark periods.

Predictive aging of polymers

NASA Technical Reports Server (NTRS)

Cuddihy, Edward F. (Inventor); Willis, Paul B. (Inventor)

1990-01-01

A method of predicting aging of polymers operates by heating a polymer in the outdoors to an elevated temperature until a change of property is induced. The test is conducted at a plurality of temperatures to establish a linear Arrhenius plot which is extrapolated to predict the induction period for failure of the polymer at ambient temperature. An Outdoor Photo Thermal Aging Reactor (OPTAR) is also described including a heatable platen for receiving a sheet of polymer, means to heat the platen and switching means such as a photoelectric switch for turning off the heater during dark periods.

Ageing of polymer bonds: a coupled chemomechanical modelling approach

NASA Astrophysics Data System (ADS)

Dippel, Benedikt; Johlitz, Michael; Lion, Alexander

2014-05-01

With the increasing number of requirements on joinings, it gets more and more important to understand and predict an assemblies properties. Nowadays, in industrial applications, combinations of different materials get more common. In most of those cases, it is, besides other advantages, useful to connect such parts with adhesives to avoid local cells. Thus, the knowledge about the mechanical behaviour of adhesives over the whole time of utilisation is an essential element of engineering. As it is well known, ageing due to environmental influences such as oxygen, radiation, ozone and others plays a major role in polymers properties. So, for the prediction of applicability over the whole lifetime of a technical component, the change in mechanical properties due to ageing is necessary. In this contribution, we introduce a material model which takes into account the internal structure of an adhesive. Therefore, an interphase zone is introduced. In the interphase, which is developed due to the contact of an adhesive with an adherent, the materials properties change continuously from the surface to the centre of the joint, where the polymer is in a bulky state. Built up on this geometry dependency, the materials ageing as a function of the position is described. To model the change of the polymers state, we use a parameter representing chain scission processes and another one for the reformation of a new network. In a last step, the model is transferred into a finite element code for exemplary calculations.

Probing Polymer-Segment Motions By ESR

NASA Technical Reports Server (NTRS)

Tsay, Fun-Dow; Gupta, Amitava

1988-01-01

Molecular origins of mechanical properties and aging processes studied. Rotational motions of segments of poly(methyl methacrylate) molecules studied theoretically and experimentally. Activation energies of these motions as determined from temperature dependencies of ESR spectra agree closely with predictions of theory.

Rheological observation of glassy dynamics of dilute polymer solutions near the coil-stretch transition in elongational flows.

PubMed

Sridhar, T; Nguyen, D A; Prabhakar, R; Prakash, J Ravi

2007-04-20

It has long been conjectured that the macroscopic dynamics of dilute polymer solutions may exhibit a glasslike slowdown caused by ergodicity breaking, in the vicinity of the coil-stretch transition in elongational flows. We report experimental observations using a filament stretching rheometer that confirm the existence of such glassy states. It is observed that different time-dependent elongational strain-rate profiles lead to a pronounced history dependence and aging effects within a narrow range of strain rates. The results have a direct bearing on the analysis and design of processes employing dilute polymer solutions, such as ink-jet printing, surface coating, and turbulent-drag reduction.

Simultaneous Thermal and Gamma Radiation Aging of Cable Polymers

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

Fifield, Leonard S.; Liu, Shuaishuai; Bowler, Nicola

Polymers used in nuclear power plant electrical cable systems experience aging and degradation over time due to environmental stress including heat and gamma irradiation. Prediction of long-term cable performance has been based on results of short-term accelerated laboratory aging studies, but questions remain regarding the correlation of accelerated aging to long-term, in-plant aging. This work seeks to increase understanding of the combined effects of heat and radiation on cable polymer material aging toward addressing these questions.

Process for restoring membrane permeation properties

DOEpatents

Pinnau, Ingo; Toy, Lora G.; Casillas, Carlos G.

1997-05-20

A process for restoring the selectivity of high-flee-volume, glassy polymer membranes for condensable components over less-condensable components or non-condensable components of a gas mixture. The process involves exposing the membrane to suitable sorbent vapor, such as propane or butane, thereby reopening the microvoids that make up the free volume. The selectivity of an aged membrane may be restored to 70-100% of its original value. The selectivity of a membrane which is known to age over time can also be maintained by keeping the membrane in a vapor environment when it is not in use.

Process for restoring membrane permeation properties

DOEpatents

Pinnau, I.; Toy, L.G.; Casillas, C.G.

1997-05-20

A process is described for restoring the selectivity of high-free-volume, glassy polymer membranes for condensable components over less-condensable components or non-condensable components of a gas mixture. The process involves exposing the membrane to suitable sorbent vapor, such as propane or butane, thereby reopening the microvoids that make up the free volume. The selectivity of an aged membrane may be restored to 70--100% of its original value. The selectivity of a membrane which is known to age over time can also be maintained by keeping the membrane in a vapor environment when it is not in use. 8 figs.

A thermoplastic polyimidesulfone. [synthesis of processable and solvent resistant system

NASA Technical Reports Server (NTRS)

St. Clair, T. L.; Yamaki, D. A.

1984-01-01

A polymer system has been prepared which has the excellent thermoplastic properties generally associated with polysulfones, and the solvent resistance and thermal stability of aromatic polyimides. This material, with improved processability over the base polyimide, can be processed in the 260-325 C range in such a manner as to yield high quality, tough unfilled moldings; strong, high-temperature-resistant adhesive bonds; and well consolidated, graphite-fiber-reinforced moldings (composites). The unfilled moldings have physical properties that are similar to aromatic polysulfones which demonstrates the potential as an engineering thermoplastic. The adhesive bonds exhibit excellent retention of initial strength levels even after thermal aging for 5000 hours at 232 C. The graphite-fiber-reinforced moldings have mechanical properties which makes this polymer attractive for the fabrication of structural composites.

Ion track etching revisited: I. Correlations between track parameters in aged polymers

NASA Astrophysics Data System (ADS)

Fink, D.; Muñoz H., G.; García A., H.; Vacik, J.; Hnatowicz, V.; Kiv, A.; Alfonta, L.

2018-04-01

Some yet poorly understood problems of etching of pristine and swift heavy ion track-irradiated aged polymers were treated, by applying conductometry across the irradiated foils during etching. The onset times of etchant penetration across pristine foils, and the onset times of the different etched track regimes in irradiated foils were determined for polymers of various proveniences, fluences and ages, as well as their corresponding etching speeds. From the results, correlations of the parameters with each other were deduced. The normalization of these parameters enables one to compare irradiated polymer foils of different origin and treatment with one another. In a number of cases, also polymeric gel formation and swelling occur which influence the track etching behaviour. The polymer degradation during aging influences the track etching parameters, which differ from each other on both sides of the foils. With increasing sample age, these differences increase.

New Avenue for Limiting Degradation in NanoLi4Ti5O12 for Ultrafast-Charge Lithium-Ion Batteries: Hybrid Polymer-Inorganic Particles.

PubMed

Daigle, Jean-Christophe; Asakawa, Yuichiro; Beaupré, Mélanie; Vieillette, René; Laul, Dharminder; Trudeau, Michel; Zaghib, Karim

2017-12-13

Lithium titanium oxide (Li 4 Ti 5 O 12 )-based cells are a very promising battery technology for ultrafast-charge-discharge and long-cycle-life batteries. However, the surface reactivity of lithium titanium oxide in the presence of organic electrolytes continues to be a problem that may cause expansion of pouch cells. In this study, we report on the development of a simple and economical grafting method for forming hybrid polymer-Li 4 Ti 15 O 12 nanoparticles, which can be successfully applied in lithium-ion batteries. This method utilizes a low-cost and scalable hydrophobic polymer that is applicable in industrial processes. The hybrid materials demonstrated exceptional capability for preventing the degradation of cells in accelerated aging and operating over 150 cycles at 1C and 45 °C.

A modelling approach for the heterogeneous oxidation of elastomers

NASA Astrophysics Data System (ADS)

Herzig, A.; Sekerakova, L.; Johlitz, M.; Lion, A.

2017-09-01

The influence of oxygen on elastomers, known as oxidation, is one of the most important ageing processes and becomes more and more important for nowadays applications. The interaction with thermal effects as well as antioxidants makes oxidation of polymers a complex process. Based on the polymer chosen and environmental conditions, the ageing processes may behave completely different. In a lot of cases the influence of oxygen is limited to the surface layer of the samples, commonly referred to as diffusion-limited oxidation. For the lifetime prediction of elastomer components, it is essential to have detailed knowledge about the absorption and diffusion behaviour of oxygen molecules during thermo-oxidative ageing and how they react with the elastomer. Experimental investigations on industrially used elastomeric materials are executed in order to develop and fit models, which shall be capable of predicting the permeation and consumption of oxygen as well as changes in the mechanical properties. The latter are of prime importance for technical applications of rubber components. Oxidation does not occur homogeneously over the entire elastomeric component. Hence, material models which include ageing effects have to be amplified in order to consider heterogeneous ageing, which highly depends on the ageing temperature. The influence of elevated temperatures upon accelerated ageing has to be critically analysed, and influences on the permeation and diffusion coefficient have to be taken into account. This work presents phenomenological models which describe the oxygen uptake and the diffusion into elastomers based on an improved understanding of ongoing chemical processes and diffusion limiting modifications. On the one side, oxygen uptake is modelled by means of Henry's law in which solubility is a function of the temperature as well as the ageing progress. The latter is an irreversible process and described by an inner differential evolution equation. On the other side, further diffusion of oxygen into the material is described by a model based on Fick's law, which is modified by a reaction term. The evolved diffusion-reaction equation depends on the ageing temperature as well as on the progress of ageing and is able to describe diffusion-limited oxidation.

Changes in polyphenols of the seed coat during the after-darkening process in pinto beans (Phaseolus vulgaris L.).

PubMed

Beninger, Clifford W; Gu, Liwei; Prior, Ronald L; Junk, Donna C; Vandenberg, Albert; Bett, Kirstin E

2005-10-05

Proanthocyanidins and flavonoids were isolated and identified from seed coats of two aged and nonaged pinto bean lines: 1533-15 and CDC Pintium. The seed coat of 1533-15 darkens slowly and never darkens to the same extent as CDC Pintium. Analysis of the overall level of proanthocyanidins using a vanillin assay demonstrated that aged and nonaged seed coats of CDC Pintium had significantly higher levels of proanthocyanidins than aged and nonaged 1533-15 seed coats. Aged and nonaged seed coats of both lines were found to contain one main flavonol monomer, kaempferol, and three minor flavonols, kaempferol 3-O-glucoside, kaempferol 3-O-glucosylxylose, and kaempferol 3-O-acetylglucoside. These compounds were identified by NMR and ESI-MS analysis (except for kaempferol 3-O-acetylglucoside, which was tentatively identified only by ESI-MS analysis) and quantified using HPLC-DAD. The combined concentrations of all the kaempferol compounds in seed coats of CDC Pintium were significantly higher than in seed coats of 1533-15, and the combined contents did not change after aging. The content of kaempferol decreased nearly by half in the seed coats of CDC Pintium after aging, whereas no significant change was observed in the seed coats of 1533-15. Proanthocyanidin fractions from both lines, aged and nonaged, were subjected to LC-MS/MS analysis and found to be composed primarily of procyanidins. Procyanidins in the seed coats were predominantly polymers with the degree of polymers higher than 10. The proportion of these polymers decreased after aging, while that of the low-molecular-weight procyanidins increased. A catechin-kaempferol adduct was tentatively identified in both lines by LC-MS/MS, and the concentration increased in the seed coats after aging.

Solution aging and degradation of a transparent conducting polymer dispersion

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

Li, Jun; Jacobs, Ian E.; Friedrich, Stephan

As organic electronics improve, there is increased research interest on the longevity and stability of both the device and individual material components. Most of these studies focus on post deposition degradation and aging of the film. In this article, we examine the stability of polyelectrolyte dispersions before film coating. We observe substantial differences in the solution properties of the transparent conducting polymer, S-P3MEET, when comparing fresh versus aged dispersions and relate these solution differences to film properties. The aged dispersion contains large agglomerates and exhibits a typical shear-thinning rheological behavior, which results in non-uniformity of the spin-coated films. Near edgemore » X-ray absorption fine structure measurements were used to differentiate the changes in bonding and oxidation states and show that aged S-P3MEET is more highly self-doped than fresh S-P3MEET. We also show that addition of acid, salt or heat to fresh S-P3MEET can accelerate the degradation/aging process but are subjected to different mechanisms. Conductivity measurements of S-P3MEET films illustrate that there is a tradeoff between increased work function and decreased conductivity upon perfluorinated ionomer (PFI) loading. The formation of nanostructure in solution is also correlated to film morphology variations obtained from atomic force microscopy. Here, we expect that dispersion aging is a process that commonly exists in most solution-dispersed polyelectrolyte materials and that the methodologies presented in this paper might be beneficial to future degradation/stability studies.« less

Solution aging and degradation of a transparent conducting polymer dispersion

DOE PAGES

Li, Jun; Jacobs, Ian E.; Friedrich, Stephan; ...

2016-04-23

As organic electronics improve, there is increased research interest on the longevity and stability of both the device and individual material components. Most of these studies focus on post deposition degradation and aging of the film. In this article, we examine the stability of polyelectrolyte dispersions before film coating. We observe substantial differences in the solution properties of the transparent conducting polymer, S-P3MEET, when comparing fresh versus aged dispersions and relate these solution differences to film properties. The aged dispersion contains large agglomerates and exhibits a typical shear-thinning rheological behavior, which results in non-uniformity of the spin-coated films. Near edgemore » X-ray absorption fine structure measurements were used to differentiate the changes in bonding and oxidation states and show that aged S-P3MEET is more highly self-doped than fresh S-P3MEET. We also show that addition of acid, salt or heat to fresh S-P3MEET can accelerate the degradation/aging process but are subjected to different mechanisms. Conductivity measurements of S-P3MEET films illustrate that there is a tradeoff between increased work function and decreased conductivity upon perfluorinated ionomer (PFI) loading. The formation of nanostructure in solution is also correlated to film morphology variations obtained from atomic force microscopy. Here, we expect that dispersion aging is a process that commonly exists in most solution-dispersed polyelectrolyte materials and that the methodologies presented in this paper might be beneficial to future degradation/stability studies.« less

Aging of Polymers and Composites.

DTIC Science & Technology

1981-07-21

used to characterize the aging processes in the epoxy resin system, MY720 (mainly tetraglycidaldiaminodiphenyl methane, Ciba-Geigy) cured with Eporal...or nitrogen is used to purge the sample chamber; however, other gases can be used . The sample stage incorporates two matched heaters and Signal ...mass spectral data from the PAMS experiments. The hardware used in this facility is shown in Figure D2. The multiplexer permits the use of one analog

A thermoplastic polyimidesulfone

NASA Technical Reports Server (NTRS)

St.clair, T. L.; Yamaki, D. A.

1982-01-01

A polymer system has been prepared which has the excellent thermoplastic properties generally associated with polysulfones, and the solvent resistance and thermal stability of aromatic polyimides. This material, with improved processability over the base polyimide, can be processed in the 260-325 C range in such a manner as to yield high quality, tough unfilled moldings; strong, high-temperature-resistant adhesive bonds; and well consolidated, graphite-fiber-reinforced moldings (composities). The unfilled moldings have physical properties that are similar to aromatic polysulfones which demonstrates the potential as an engineering thermoplastic. The adhesive bonds exhibit excellent retention of initial strength levels even after thermal aging for 5000 hours at 232 C. The graphite-fiber-reinforced moldings have mechanical properties which makes this polymer attractive for the fabrication of structural composites.

High temperature polymer degradation: Rapid IR flow-through method for volatile quantification

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

Giron, Nicholas H.; Celina, Mathew C.

Accelerated aging of polymers at elevated temperatures often involves the generation of volatiles. These can be formed as the products of oxidative degradation reactions or intrinsic pyrolytic decomposition as part of polymer scission reactions. A simple analytical method for the quantification of water, CO 2, and CO as fundamental signatures of degradation kinetics is required. Here, we describe an analytical framework and develops a rapid mid-IR based gas analysis methodology to quantify volatiles that are contained in small ampoules after aging exposures. The approach requires identification of unique spectral signatures, systematic calibration with known concentrations of volatiles, and a rapidmore » acquisition FTIR spectrometer for time resolved successive spectra. Furthermore, the volatiles are flushed out from the ampoule with dry N2 carrier gas and are then quantified through spectral and time integration. This method is sufficiently sensitive to determine absolute yields of ~50 μg water or CO 2, which relates to probing mass losses of less than 0.01% for a 1 g sample, i.e. the early stages in the degradation process. Such quantitative gas analysis is not easily achieved with other approaches. Our approach opens up the possibility of quantitative monitoring of volatile evolution as an avenue to explore polymer degradation kinetics and its dependence on time and temperature.« less

High temperature polymer degradation: Rapid IR flow-through method for volatile quantification

DOE PAGES

Giron, Nicholas H.; Celina, Mathew C.

2017-05-19

Accelerated aging of polymers at elevated temperatures often involves the generation of volatiles. These can be formed as the products of oxidative degradation reactions or intrinsic pyrolytic decomposition as part of polymer scission reactions. A simple analytical method for the quantification of water, CO 2, and CO as fundamental signatures of degradation kinetics is required. Here, we describe an analytical framework and develops a rapid mid-IR based gas analysis methodology to quantify volatiles that are contained in small ampoules after aging exposures. The approach requires identification of unique spectral signatures, systematic calibration with known concentrations of volatiles, and a rapidmore » acquisition FTIR spectrometer for time resolved successive spectra. Furthermore, the volatiles are flushed out from the ampoule with dry N2 carrier gas and are then quantified through spectral and time integration. This method is sufficiently sensitive to determine absolute yields of ~50 μg water or CO 2, which relates to probing mass losses of less than 0.01% for a 1 g sample, i.e. the early stages in the degradation process. Such quantitative gas analysis is not easily achieved with other approaches. Our approach opens up the possibility of quantitative monitoring of volatile evolution as an avenue to explore polymer degradation kinetics and its dependence on time and temperature.« less

Predictive Modeling of Polymer Mechanical Behavior Coupled to Chemical Change/ Technique Development for Measuring Polymer Physical Aging.

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

Kropka, Jamie Michael; Stavig, Mark E.; Arechederra, Gabe Kenneth

Develop an understanding of the evolution of glassy polymer mechanical response during aging and the mechanisms associated with that evolution. That understanding will be used to develop constitutive models to assess the impact of stress evolution in encapsulants on NW designs.

Numerical-graphical method for describing the creep of damaged highly filled polymer materials

NASA Astrophysics Data System (ADS)

Bykov, D. L.; Martynova, E. D.; Mel'nikov, V. P.

2015-09-01

A method for describing the creep behavior until fracture of a highly filled polymer material previously damaged in preliminary tests is proposed. The constitutive relations are the relations of nonlinear endochronic theory of aging viscoelastic materials (NETAVEM) [1]. The numerical-graphical method for identifying the functions occurring in NETAVEM, which was proposed in [2] for describing loading processes at a constant strain rate, is used here for the first time in creep theory. We use the results of experiments with undamaged and preliminary damaged specimens under the action of the same constant tensile loads. The creep kernel is determined in experiments with an undamaged specimen. The reduced time function contained in NETAVEM is determined from the position of points corresponding to the same values of strain on the creep curves of the damaged and undamaged specimens. An integral equation is solved to obtain the aging function, and then the viscosity function is determined. The knowledge of all functions contained in the constitutive relations permits solving the creep problem for products manufactured from a highly filled polymer material.

Robust and Elastic Polymer Membranes with Tunable Properties for Gas Separation

DOE PAGES

Cao, Peng -Fei; Li, Bingrui; Hong, Tao; ...

2017-07-17

Here, polymer membranes with the capability to process a massive volume of gas are especially attractive for practical applications of gas separation. Although much effort has been devoted to develop novel polymer membranes with increased selectivity, the overall gas-separation performance and lifetime of membrane are still negatively affected by the weak mechanical performance, low plasticization resistance and poor physical aging tolerance. Recently, elastic polymer membranes with tunable mechanical properties have been attracting significant attentions due to their tremendous potential applications. Herein, we report a series of urethanerich PDMS-based polymer networks (U-PDMS-NW) with improved mechanical performance for gas separation. The cross-linkmore » density of U-PDMS-NWs is tailored by varying the molecular weight ( M n) of PDMS. The U-PDMS-NWs show up to 400% elongation and tunable Young’s modulus (1.3–122.2 MPa), ultimate tensile strength (1.1–14.3 MPa), and toughness (0.7–24.9 MJ/m 3). All of the U-PDMS-NWs exhibit salient gas-separation performance with excellent thermal resistance and aging tolerance, high gas permeability (>100 Barrer), and tunable gas selectivity (up to α[ P CO2/ P N2] ≈ 41 and α[ P CO2/ P CH4] ≈ 16). With well-controlled mechanical properties and gas-separation performance, these U-PDMS-NW can be used as a polymermembrane platform not only for gas separation but also for other applications such as microfluidic channels and stretchable electronic devices.« less

US/UK second level panel discussions on the health and value of: Ageing and lifetime predictions (u)

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

Castro, Richard G

2011-01-18

Many healthy physics, engineering, and materials exchanges are being accomplished in ageing and lifetime prediction that directly supports US and UK Stockpile Management Programs. Lifetime assessment studies of silicon foams under compression - Joint AWE/LANLlLLNL study of compression set in stress cushions completed. Provides phenomenological prediction out to 50 years. Polymer volatile out-gassing studies - New exchange on the out-gassing of Ethylene Vinyl Acetate (EVA) using isotopic {sup 13}C labeling studies to interrogate mechanistic processes. Infra-red (IR) gas cell analytical capabilities developed by AWE will be used to monitor polymer out-gassing profiles. Pu Strength ageing Experiments and Constitutive Modeling -more » In recently compared modeling strategies for ageing effects on Pu yield strength at high strain rates, a US/UK consensus was reached on the general principle that the ageing effect is additive and not multiplicative. The fundamental mechanisms for age-strengthening in Pu remains unknown. Pu Surface and Interface Reactions - (1) US/UK secondment resulted in developing a metal-metal oxide model for radiation damaged studies consistent with a Modified Embedded Atom Method (MEAM) potential; and (2) Joint US/UK collaboration to study the role of impurities in hydride initiation. Detonator Ageing (wide range of activities) - (1) Long-term ageing study with field trials at Pantex incorporating materials from LANL, LLNL, SNL and AWE; (2) Characterization of PETN growth to detonation process; (3) Detonator performance modeling; and (4) Performance fault tree analysis. Benefits are a unified approach to lifetime prediction that Includes: materials characterization and the development of ageing models through improved understanding of the relationship between materials properties, ageing properties and detonator performance.« less

Mechanics of the Delayed Fracture of Viscoelastic Bodies with Cracks: Theory and Experiment (Review)

NASA Astrophysics Data System (ADS)

Kaminsky, A. A.

2014-09-01

Theoretical and experimental studies on the deformation and delayed fracture of viscoelastic bodies due to slow subcritical crack growth are reviewed. The focus of this review is on studies of subcritical growth of cracks with well-developed fracture process zones, the conditions that lead to their critical development, and all stages of slow crack growth from initiation to the onset of catastrophic growth. Models, criteria, and methods used to study the delayed fracture of viscoelastic bodies with through and internal cracks are analyzed. Experimental studies of the fracture process zones in polymers using physical and mechanical methods as well as theoretical studies of these zones using fracture mesomechanics models that take into account the structural and rheological features of polymers are reviewed. Particular attention is given to crack growth in anisotropic media, the effect of the aging of viscoelastic materials on their delayed fracture, safe external loads that do not cause cracks to propagate, the mechanism of multiple-flaw fracture of viscoelastic bodies with several cracks and, especially, processes causing cracks to coalesce into a main crack, which may result in a break of the body. Methods and results of solving two- and three-dimensional problems of the mechanics of delayed fracture of aging and non-aging viscoelastic bodies with cracks under constant and variable external loads, wedging, and biaxial loads are given

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

NASA Technical Reports Server (NTRS)

Willis, P. B.; Baum, B.

1977-01-01

The potentially useful encapsulating materials for Task 3 of the Low-Cost Silicon Solar Array project were studied to identify, evaluate, and recommend encapsulant materials and processes for the production of cost-effective, long-life solar cell modules. Materials for study were chosen on the basis of existing knowledge of generic chemical types having high resistance to environmental weathering. The materials varied from rubbers to thermoplastics and presented a broad range of mechanical properties and processing requirements. Basic physical and optical properties were measured on the polymers and were redetermined after exposure to indoor artificial accelerated aging conditions covering four time periods. Strengths and weaknesses of the various materials were revealed and data was accumulated for the development of predictive methodologies. To date, silicone rubbers, fluorocarbons, and acrylic polymers appear to have the most promising combination of characteristics. The fluorocarbons may be used only as films, however, because of their high cost.

Effect of processing on Polymer/Composite structure and properties

NASA Technical Reports Server (NTRS)

1982-01-01

Advances in the vitality and economic health of the field of polymer forecasting are discussed. A consistent and rational point of view which considers processing as a participant in the underlying triad of relationships which comprise materials science and engineering is outlined. This triad includes processing as it influences material structure, and ultimately properties. Methods in processing structure properties, polymer science and engineering, polymer chemistry and synthesis, structure and modification and optimization through processing, and methods of melt flow modeling in processing structure property relations of polymer were developed. Mechanical properties of composites are considered, and biomedical materials research to include polymer processing effects are studied. An analysis of the design technology of advances graphite/epoxy composites is also reported.

The effect of side-chain substitution and hot processing on diketopyrrolopyrrole-based polymers for organic solar cells.

PubMed

Heintges, Gaël H L; Leenaers, Pieter J; Janssen, René A J

2017-07-14

The effects of cold and hot processing on the performance of polymer-fullerene solar cells are investigated for diketopyrrolopyrrole (DPP) based polymers that were specifically designed and synthesized to exhibit a strong temperature-dependent aggregation in solution. The polymers, consisting of alternating DPP and oligothiophene units, are substituted with linear and second position branched alkyl side chains. For the polymer-fullerene blends that can be processed at room temperature, hot processing does not enhance the power conversion efficiencies compared to cold processing because the increased solubility at elevated temperatures results in the formation of wider polymer fibres that reduce charge generation. Instead, hot processing seems to be advantageous when cold processing is not possible due to a limited solubility at room temperature. The resulting morphologies are consistent with a nucleation-growth mechanism for polymer fibres during drying of the films.

Impact of the Ageing on Viscoelastic Properties of Bitumen with the Liquid Surface Active Agent at Operating Temperatures

NASA Astrophysics Data System (ADS)

Iwański, Marek; Cholewińska, Malgorzata; Mazurek, Grzegorz

2017-10-01

The paper presents the influence of the ageing on viscoelastic properties of the bitumen at road pavement operating temperatures. The ageing process of bituminous binders causes changes in physical and mechanical properties of the bitumen. This phenomenon takes place in all stages of bituminous mixtures manufacturing, namely: mixing, storage, transport, placing. Nevertheless, during the service life it occurs the increase in stiffness of asphalt binder that is caused by the physical hardening of bitumen as well as the influence of oxidation. Therefore, it is important to identify the binder properties at a high and low operating temperatures of asphalt pavement after simulation of an ageing process. In the experiment as a reference bitumen, the polymer modified bitumen PMB 45/80-65 was used. The liquid surface active agent FA (fatty amine) was used as a bitumen viscosity-reducing modifier. It was added in the amount of 0,2%, 0,4% and 0,6% by the bitumen mass. All binder properties have been determined before ageing (NEAT) and after long-term ageing simulated by the Pressure Ageing Vessel method (PAV). To determine the binder properties at high temperatures the dynamic viscosity at 60°C was tested. On the basis of test results coming from the dynamic viscosity test it was calculated the binder hardening index. The properties at a low temperature were determined by measuring the creep modulus using Bending Beam Rheometer (BBR) at four temperatures: -10°C, -16°C, -22°C and -28°C. The stiffness creep modulus “S” and parameter “m” were determined. On the basis of dynamic viscosity test it was found that the ageing process caused a slight decrease in a dynamic viscosity. The level of a hardening index considerably increased at 0.6% fatty amine content. The long-term ageing process had a minor effect on stiffening of a polymer modified bitumen with FA additive regardless of a low temperature and an amount of fatty amine content.

Simultaneous Thermal and Gamma Radiation Aging of Electrical Cable Polymers

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

Fifield, Leonard S.

The polymers used for insulation in nuclear power plant electrical cables are susceptible to aging during long term operation. Elevated temperature is the primary contributor to changes in polymer structure that result loss of mechanical and electrical properties, but gamma radiation is also a significant source of degradation for polymers used within relevant plant locations. Despite many years of polymer degradation research, the combined effects of simultaneous exposure to thermal and radiation stress are not well understood. As nuclear operators contemplate and prepare for extended operations beyond initial license periods, a predictive understanding of exposure-based cable material degradation is becomingmore » an increasingly important input to safety, licensing, operations and economic decisions. We are focusing on carefully-controlled simultaneous thermal and gamma radiation accelerating aging and characterization of the most common nuclear cable polymers to understand the relative contributions of temperature, time, dose and dose rate to changes in cable polymer material structure and properties. Improved understanding of cable performance in long term operation will help support continued sustainable nuclear power generation.« less

Physical and mechanical properties of PLA, and their functions in widespread applications - A comprehensive review.

PubMed

Farah, Shady; Anderson, Daniel G; Langer, Robert

2016-12-15

Poly(lactic acid) (PLA), so far, is the most extensively researched and utilized biodegradable aliphatic polyester in human history. Due to its merits, PLA is a leading biomaterial for numerous applications in medicine as well as in industry replacing conventional petrochemical-based polymers. The main purpose of this review is to elaborate the mechanical and physical properties that affect its stability, processability, degradation, PLA-other polymers immiscibility, aging and recyclability, and therefore its potential suitability to fulfill specific application requirements. This review also summarizes variations in these properties during PLA processing (i.e. thermal degradation and recyclability), biodegradation, packaging and sterilization, and aging (i.e. weathering and hygrothermal). In addition, we discuss up-to-date strategies for PLA properties improvements including components and plasticizer blending, nucleation agent addition, and PLA modifications and nanoformulations. Incorporating better understanding of the role of these properties with available improvement strategies is the key for successful utilization of PLA and its copolymers/composites/blends to maximize their fit with worldwide application needs. Copyright © 2016 Elsevier B.V. All rights reserved.

Long-Term Stable Adhesion for Conducting Polymers in Biomedical Applications: IrOx and Nanostructured Platinum Solve the Chronic Challenge.

PubMed

Boehler, Christian; Oberueber, Felix; Schlabach, Sabine; Stieglitz, Thomas; Asplund, Maria

2017-01-11

Conducting polymers (CPs) have frequently been described as outstanding coating materials for neural microelectrodes, providing significantly reduced impedance or higher charge injection compared to pure metals. Usability has until now, however, been limited by poor adhesion of polymers like poly(3,4-ethylenedioxythiophene) (PEDOT) to metallic substrates, ultimately precluding long-term applications. The aim of this study was to overcome this weakness of CPs by introducing two novel adhesion improvement strategies that can easily be integrated with standard microelectrode fabrication processes. Iridium Oxide (IrOx) demonstrated exceptional stability for PEDOT coatings, resulting in polymer survival over 10 000 redox cycles and 110 days under accelerated aging conditions at 60 °C. Nanostructured Pt was furthermore introduced as a purely mechanical adhesion promoter providing 10-fold adhesion improvement compared to smooth Pt substrates by simply altering the morphology of Pt. This layer can be realized in a very simple process that is compatible with any electrode design, turning nanostructured Pt into a universal adhesion layer for CP coatings. By the introduction of these adhesion-promoting strategies, the weakness of CP-based neural probes can ultimately be eliminated and true long-term stable use of PEDOT on neural probes will be possible in future electrode generations.

Influence of γ-irradiation and temperature on the mechanical properties of EPDM cable insulation

NASA Astrophysics Data System (ADS)

Šarac, T.; Quiévy, N.; Gusarov, A.; Konstantinović, M. J.

2016-08-01

The mechanical properties of EPDM polymers, degraded as a result of extensive thermal and radiochemical aging treatment, are studied. The focus is given to dose rate effects in polymer insulation materials extracted from industrial cables in use in Belgian nuclear power plants. All studied mechanical characteristics such as the ultimate tensile stress, the Young's modulus, and the total elongation (or elongation at break) are found to be strongly affected by the irradiation dose. The ultimate tensile stress and Young's modulus are clearly exhibiting the dose rate effect, which originated from oxidation mediated interplay of polymer cross-linking and chain scission processes. The change of crossover between these two processes is found to be gradual, without critical dose rate or temperature values. On the contrary, the total elongation is observed not to be sensitive neither to irradiation temperature nor to the dose rate. Both cross-linking and chain scission seem to affect the total elongation in a similar way by reducing the average polymers chain length. This idea is confirmed by the model which shows that all total elongation data as a function of irradiation time can be reproduced by varying a single parameter, the pre-exponential factor of the irradiation rate constant.

Functionalization of polymer powders for SLS-processes using an atmospheric plasma jet in a fluidized bed reactor

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

Sachs, Marius; Schmitt, Adeliene; Schmidt, Jochen

2015-05-22

Recently additive manufacturing processes such as selective laser sintering (SLS) of polymers have gained more importance for industrial applications [1]. Tailor-made modification of polymers is essential in order to make these processes more efficient and to cover the industrial demands. The so far used polymer materials show weak performance regarding the mechanical stability of processed parts. To overcome this limitation, a new route to functionalize the surface of commercially available polymer particles (PA12; PE-HD; PP) using an atmospheric plasma jet in combination with a fluidized bed reactor has been investigated. Consequently, an improvement of adhesion and wettability [2] of themore » polymer surface without restraining the bulk properties of the powder is achieved. The atmospheric plasma jet process can provide reactive species at moderate temperatures which are suitable for polymer material. The functionalization of the polymer powders improves the quality of the devices build in a SLS-process.« less

Failure of structural elements made of polymer supported composite materials during the multiyear natural aging

NASA Astrophysics Data System (ADS)

Blinkov, Pavel; Ogorodov, Leonid; Grabovyy, Peter

2018-03-01

Modern high-rise construction introduces a number of limitations and tasks. In addition to durability, comfort and profitability, projects should take into account energy efficiency and environmental problems. Polymer building materials are used as substitutes for materials such as brick, concrete, metal, wood and glass, and in addition to traditional materials. Plastic materials are light, can be formed into complex shapes, durable and low, and also possess a wide range of properties. Plastic materials are available in various forms, colors and textures and require minimal or no color. They are resistant to heat transfer and diffusion of moisture and do not suffer from metal corrosion or microbial attack. Polymeric materials, including thermoplastics, thermoset materials and wood-polymer composites, have many structural and non-structural applications in the construction industry. They provide unique and innovative solutions at a low cost, and their use is likely to grow in the future. A number of polymer composite materials form complex material compositions, which are applied in the construction in order to analyze the processes of damage accumulation under the conditions of complex nonstationary loading modes, and to determine the life of structural elements considering the material aging. This paper present the results of tests on short-term compression loading with a deformation rate of v = 2 mm/min using composite samples of various shapes and sizes.

Experimental characterization and modeling of isothermal and nonisothermal physical aging in glassy polymer films

NASA Astrophysics Data System (ADS)

Guo, Yunlong

This dissertation focuses on nonisothermal physical aging of polymers from both experimental and theoretical aspects. The study concentrates on pure polymers rather than fiber-reinforced composites; this step removes several complicating factors to simplify the study. It is anticipated that the findings of this work can then be applied to composite materials applications. The physical aging tests in this work are performed using a dynamic mechanical analyzer (DMA). The viscoelastic response of glassy polymers under various loading and thermal histories are observed as stress-strain data at a series of time points. The first stage of the experimental work involves the characterization of the isothermal physical aging behavior of two advanced thermoplastics. The second stage conducts tests on the same materials with varying thermal histories and with long-term test duration. This forms the basis to assess and modify a nonisothermal physical aging model (KAHR-ate model). Based on the experimental findings, the KAHR-ate model has been revised by new correlations between aging shift factors and volume response; this revised model performed well in predicting the nonisothermal physical aging behavior of glassy polymers. In the work on isothermal physical aging, short-term creep and stress relaxation tests were performed at several temperatures within 15-35°C below the glass transition temperature (Tg) at various aging times, using the short-term test method established by Struik. Stress and strain levels were such that the materials remained in the linear viscoelastic regime. These curves were then shifted together to determine momentary master curves and shift rates. In order to validate the obtained isothermal physical aging behavior, the results of creep and stress relaxation testing were compared and shown to be consistent with one another using appropriate interconversion of the viscoelastic material functions. Time-temperature superposition of the master curves was also performed. The temperature shift factors and aging shift rates for both PEEK and PPS were consistent for both creep and stress relaxation test results. Nonisothermal physical aging was monitored by sequential short-term creep tests after a series of temperature jumps; the resulting strain histories were analyzed to determine aging shift factors (ate) for each of the creep tests. The nonisothermal aging response was predicted using the KAHR-ate model, which combines the KAHR model of volume recovery with a suitable linear relationship between aging shift factors and specific volume. The KAHR-ate model can be utilized to both predict aging response and to determine necessary model parameters from a set of aging shift factor data. For the PEEK and PPS materials considered in the current study, predictions of mechanical response were demonstrated to be in good agreement with the experimental results for several complicated thermal histories. In addition to short-term nonisothermal aging, long-term creep tests under identical thermal conditions were also analyzed. Effective time theory was unitized to predict long-term response under both isothermal and nonisothermal temperature histories. The long-term compliance after a series of temperature changes was predicted by the KAHR- ate model, and the theoretical predictions and experimental data showed good agreement for various thermal histories. Lastly, physical aging behavior of PPS near the glass transition temperature was investigated, in order to observe the mechanical response in the process of the evolution of the material into equilibrium. At several temperatures near Tg, the time need to reach equilibrium were determined by the creep test results at various aging times. In addition to isothermal physical aging, mechanical shift factors in the period of approaching equilibrium at a common temperature after temperature up-jumps and down-jumps are monitored from creep tests; prior to these temperature jumps, the materials were aged to reach equilibrium states. From these tests, asymmetry of approaching equilibrium phenomenon in ate was observed, which is first-time reported in the literature. This finding shows the similarity between the thermodynamic and mechanical properties during structural relaxation. This work will lead to improved understanding of the viscoelastic behavior of glassy polymers, which is important for better understanding and design of PMCs in elevated temperature applications. With the above findings, this dissertation deals with nonisothermal physical aging of glassy polymers, including both experimental characterization and constructing a framework for predictions of mechanical behavior of polymeric materials under complicated thermal conditions. (Abstract shortened by UMI.)

TOPICAL REVIEW: Monitoring of polymer melt processing

NASA Astrophysics Data System (ADS)

Alig, Ingo; Steinhoff, Bernd; Lellinger, Dirk

2010-06-01

The paper reviews the state-of-the-art of in-line and on-line monitoring during polymer melt processing by compounding, extrusion and injection moulding. Different spectroscopic and scattering techniques as well as conductivity and viscosity measurements are reviewed and compared concerning their potential for different process applications. In addition to information on chemical composition and state of the process, the in situ detection of morphology, which is of specific interest for multiphase polymer systems such as polymer composites and polymer blends, is described in detail. For these systems, the product properties strongly depend on the phase or filler morphology created during processing. Examples for optical (UV/vis, NIR) and ultrasonic attenuation spectra recorded during extrusion are given, which were found to be sensitive to the chemical composition as well as to size and degree of dispersion of micro or nanofillers in the polymer matrix. By small-angle light scattering experiments, process-induced structures were detected in blends of incompatible polymers during compounding. Using conductivity measurements during extrusion, the influence of processing conditions on the electrical conductivity of polymer melts with conductive fillers (carbon black or carbon nanotubes) was monitored.

Post polymerization cure shape memory polymers

DOEpatents

Wilson, Thomas S.; Hearon, II, Michael Keith; Bearinger, Jane P.

2017-01-10

This invention relates to chemical polymer compositions, methods of synthesis, and fabrication methods for devices regarding polymers capable of displaying shape memory behavior (SMPs) and which can first be polymerized to a linear or branched polymeric structure, having thermoplastic properties, subsequently processed into a device through processes typical of polymer melts, solutions, and dispersions and then crossed linked to a shape memory thermoset polymer retaining the processed shape.

Post polymerization cure shape memory polymers

DOEpatents

Wilson, Thomas S; Hearon, Michael Keith; Bearinger, Jane P

2014-11-11

This invention relates to chemical polymer compositions, methods of synthesis, and fabrication methods for devices regarding polymers capable of displaying shape memory behavior (SMPs) and which can first be polymerized to a linear or branched polymeric structure, having thermoplastic properties, subsequently processed into a device through processes typical of polymer melts, solutions, and dispersions and then crossed linked to a shape memory thermoset polymer retaining the processed shape.

Evolution of the microstructure of unmodified and polymer modified asphalt binders with aging in an accelerated weathering tester.

PubMed

Menapace, Ilaria; Masad, Eyad

2016-09-01

This paper presents findings on the evolution of the surface microstructure of two asphalt binders, one unmodified and one polymer modified, directly exposed to aging agents with increasing durations. The aging is performed using an accelerated weathering tester, where ultraviolet radiation, oxygen and an increased temperature are applied to the asphalt binder surface. Ultraviolet and dark cycles, which simulated the succession of day and night, alternated during the aging process, and also the temperature varied, which corresponded to typical summer day and night temperatures registered in the state of Qatar. Direct aging of an exposed binder surface is more effective in showing microstructural modifications than previously applied protocols, which involved the heat treatment of binders previously aged with standardized methods. With the new protocol, any molecular rearrangements in the binder surface after aging induced by the heat treatment is prevented. Optical photos show the rippling and degradation of the binder surface due to aging. Microstructure images obtained by means of atomic force microscopy show gradual alteration of the surface due to aging. The original relatively flat microstructure was substituted with a profoundly different microstructure, which significantly protrudes from the surface, and is characterized by various shapes, such as rods, round structures and finally 'flower' or 'leaf' structures. © 2016 The Authors Journal of Microscopy © 2016 Royal Microscopical Society.

A numerical model to simulate foams during devolatilization of polymers

NASA Astrophysics Data System (ADS)

Khan, Irfan; Dixit, Ravindra

2014-11-01

Customers often demand that the polymers sold in the market have low levels of volatile organic compounds (VOC). Some of the processes for making polymers involve the removal of volatiles to the levels of parts per million (devolatilization). During this step the volatiles are phase separated out of the polymer through a combination of heating and applying lower pressure, creating foam with the pure polymer in liquid phase and the volatiles in the gas phase. The efficiency of the devolatilization process depends on predicting the onset of solvent phase change in the polymer and volatiles mixture accurately based on the processing conditions. However due to the complex relationship between the polymer properties and the processing conditions this is not trivial. In this work, a bubble scale model is coupled with a bulk scale transport model to simulate the processing conditions of polymer devolatilization. The bubble scale model simulates the nucleation and bubble growth based on the classical nucleation theory and the popular ``influence volume approach.'' As such it provides the information of bubble size distribution and number density inside the polymer at any given time and position. This information is used to predict the bulk properties of the polymer and its behavior under the applied processing conditions. Initial results of this modeling approach will be presented.

Transport and Reactivity of Decontaminants to Provide Hazard Mitigation of Chemical Warfare Agents from Materials

DTIC Science & Technology

2016-06-01

Membranes .2. Neoprene, SBR, EPDM , NBR, and Natural- Rubber Versus Normal-Alkanes. J. Appl. Polym. Sci. 1991, 42 (8), 2329–2336. 24. Harogoppad, S.B...highly absorptive (e.g., tire rubber ). Absorptive materials are often more challenging to decontaminate because of the reduced accessibility of the...then aged for 60 min. During the aging period, agent mass was absorbed by a flux-based process.7 The agent-contaminated area of the panel may affect

Studies on the effect of virtual crosslinking on the hydrolytic stability of novel aliphatic polyurethane ureas for blood contact applications.

PubMed

Thomas, V; Jayabalan, M

2001-07-01

The effect of virtual crosslinking on the hydrolytic stability of completely aliphatic novel poly(urethane ureas), HFL9-PU1 (hard-segment content 57.5%) and HFL13-PU2 (hard-segment content 67.9%) based on 4,4'-methylene bis(cyclohexyl isocyanate) (H(12)MDI)-hydroxy-terminated polybutadiene-1,6-hexamethylene diamine, was studied. Fourier transform infrared-attenuated total reflectance and wide-angle X-ray diffraction studies revealed hydrogen-bonding interaction and microphase separation and formation of crystallites by short- and long-range ordering in hard-segment domains. Three-dimensional networks from hydrogen bonding in the present polymers lead to virtually crosslinking and insolubility. These polymers were noncytotoxic to L929 fibroblast cells. The hemolytic potential is below the accepted limit. The studies on in vitro biostability in Ringer's solution, phosphate buffered saline, and papain enzyme revealed no weight loss. The infrared spectral studies revealed changes in the surface, especially on HFL9-PU1 aged in Ringer's solution and phosphate buffered saline, and no changes when aged in papain. The marginal changes noticed in tensile properties were attributed to the changes in degree of hydrogen bonding and associated rearrangement of molecular structure in the bulk. The results revealed that the lesser the crosslinking in virgin polymer, the higher the crosslinking in aged polymer and vice versa. Increased crosslinking during aging provided increased tensile properties in the aged polymer over the virgin polymer and vice versa. For comparison, an aliphatic polyetherurethane urea (HFL16-PU3) was also synthesized using poly(oxy tetra methylene glycol) in addition to the above reactants. Though both HFL9-PU1 and HFL16-PU3 contained the same hard-segment content, the aged sample of the latter showed decreased tensile properties with increased crosslinking during aging in contrast to the former. This was attributed to less microphase separation in the virgin HFL16-PU3 polymer.

The importance of new processing techniques in tissue engineering

NASA Technical Reports Server (NTRS)

Lu, L.; Mikos, A. G.; McIntire, L. V. (Principal Investigator)

1996-01-01

The use of polymer scaffolds in tissue engineering is reviewed and processing techniques are examined. The discussion of polymer-scaffold processing explains fiber bonding, solvent casting and particulate leaching, membrane lamination, melt molding, polymer/ceramic fiber composite-foam processing, phase separation, and high-pressure processing.

Fabrication of multilayered conductive polymer structures via selective visible light photopolymerization

NASA Astrophysics Data System (ADS)

Cullen, Andrew T.; Price, Aaron D.

2017-04-01

Electropolymerization of pyrrole is commonly employed to fabricate intrinsically conductive polymer films that exhibit desirable electromechanical properties. Due to their monolithic nature, electroactive polypyrrole films produced via this process are typically limited to simple linear or bending actuation modes, which has hindered their application in complex actuation tasks. This initiative aims to develop the specialized fabrication methods and polymer formulations required to realize three-dimensional conductive polymer structures capable of more elaborate actuation modes. Our group has previously reported the application of the digital light processing additive manufacturing process for the fabrication of three-dimensional conductive polymer structures using ultraviolet radiation. In this investigation, we further expand upon this initial work and present an improved polymer formulation designed for digital light processing additive manufacturing using visible light. This technology enables the design of novel electroactive polymer sensors and actuators with enhanced capabilities and brings us one step closer to realizing more advanced electroactive polymer enabled devices.

A process for preparing an ultra-thin, adhesiveless, multi-layered, patterned polymer substrate

NASA Technical Reports Server (NTRS)

Bryant, Robert G. (Inventor); Kruse, Nancy H. M. (Inventor); Fox, Robert L. (Inventor); Tran, Sang Q. (Inventor)

1995-01-01

A process for preparing an ultra-thin, adhesiveless, multi-layered, patterned polymer substrate is disclosed. The process may be used to prepare both rigid and flexible cables and circuit boards. A substrate is provided and a polymeric solution comprising a self-bonding, soluble polymer and a solvent is applied to the substrate. Next, the polymer solution is dried to form a polymer coated substrate. The polymer coated substrate is metallized and patterned. At least one additional coating of the polymeric solution is applied to the metallized, patterned, polymer coated substrate and the steps of metallizing and patterning are repeated. Lastly, a cover coat is applied. When preparing a flexible cable and flexible circuit board, the polymer coating is removed from the substrate.

Physical Aging Studies of Styrene-Butadiene and Carbonate-Siloxane Block Copolymers

DTIC Science & Technology

1979-11-19

Carbonate-Siloxane Block Copolymers, ,-- by Martin Tant Garth . D D C Prepared for Publication r - r-on n[? in the JAN Journal of Applied Polymer Science B...revereie ifI nocesy and Identify by black mumibo,) Polymer glasses Non equilibrium glasses Stress relaxation Block copolymers 20. AOSTRACT (Continwaon...copolymers in material applications. -2- Introduction The physical aging phenomenon in glassy polymers has drawn considerable interest within the

Near infrared (NIR) spectroscopy for in-line monitoring of polymer extrusion processes.

PubMed

Rohe, T; Becker, W; Kölle, S; Eisenreich, N; Eyerer, P

1999-09-13

In recent years, near infrared (NIR) spectroscopy has become an analytical tool frequently used in many chemical production processes. In particular, on-line measurements are of interest to increase process stability and to document constant product quality. Application to polymer processing e.g. polymer extrusion, could even increase product quality. Interesting parameters are composition of the processed polymer, moisture, or reaction status in reactive extrusion. For this issue a transmission sensor was developed for application of NIR spectroscopy to extrusion processes. This sensor includes fibre optic probes and a measuring cell to be adapted to various extruders for in-line measurements. In contrast to infrared sensors, it only uses optical quartz components. Extrusion processes at temperatures up to 300 degrees C and pressures up to 37 MPa have been investigated. Application of multivariate data analysis (e.g. partial least squares, PLS) demonstrated the performance of the system with respect to process monitoring: in the case of polymer blending, deviations between predicted and actual polymer composition were quite low (in the range of +/-0.25%). So the complete system is suitable for harsh industrial environments and could lead to improved polymer extrusion processes.

A modified dynamical model of drying process of polymer blend solution coated on a flat substrate

NASA Astrophysics Data System (ADS)

Kagami, Hiroyuki

2008-05-01

We have proposed and modified a model of drying process of polymer solution coated on a flat substrate for flat polymer film fabrication. And for example numerical simulation of the model reproduces a typical thickness profile of the polymer film formed after drying. Then we have clarified dependence of distribution of polymer molecules on a flat substrate on a various parameters based on analysis of numerical simulations. Then we drove nonlinear equations of drying process from the dynamical model and the fruits were reported. The subject of above studies was limited to solution having one kind of solute though the model could essentially deal with solution having some kinds of solutes. But nowadays discussion of drying process of a solution having some kinds of solutes is needed because drying process of solution having some kinds of solutes appears in many industrial scenes. Polymer blend solution is one instance. And typical resist consists of a few kinds of polymers. Then we introduced a dynamical model of drying process of polymer blend solution coated on a flat substrate and results of numerical simulations of the dynamical model. But above model was the simplest one. In this study, we modify above dynamical model of drying process of polymer blend solution adding effects that some parameters change with time as functions of some variables to it. Then we consider essence of drying process of polymer blend solution through comparison between results of numerical simulations of the modified model and those of the former model.

Miscibility Evaluation Of The Next Generation Solvent With Polymers Currently Used At DWPF, MCU, And Saltstone

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

Fondeur, F. F.

The Office of Waste Processing, within the Office of Technology Innovation and Development, funded the development of an enhanced Caustic-Side Solvent Extraction (CSSX) solvent for deployment at the Savannah River Site for removal of cesium from High Level Waste. This effort lead to the development of the Next Generation Solvent (NGS) with Tris (3,7-dimethyl octyl) guanidine (TiDG). The first deployment target for the NGS solvent is within the Modular CSSX Unit (MCU). Deployment of a new chemical within an existing facility requires verification that the new chemical components are compatible with the installed equipment. In the instance of a newmore » organic solvent, the primary focus is on compatibility of the solvent with organic polymers used in the affected facility. This report provides the calculated data from exposing these polymers to the Next Generation Solvent. An assessment of the dimensional stability of polymers known to be used or present in the MCU, Defense Waste Processing Facility (DWPF), and Saltstone facilities that will be exposed to the NGS showed that TiDG could selectively affect the elastomers and some thermoplastics to varying extents, but the typical use of these polymers in a confined geometry will likely prevent the NGS from impacting component performance. The polymers identified as of primary concern include Grafoil® (flexible graphite), Tefzel®, Isolast®, ethylene-propylene-diene monomer (EPDM) rubber, nitrile-butadiene rubber (NBR), styrene-butadiene rubber (SBR), ultra high molecular weight polyethylene (UHMWPE), and fluorocarbon rubber (FKM). Certain polymers like NBR and EPDM were found to interact mildly with NGS but their calculated swelling and the confined geometry will impede interaction with NGS. In addition, it was found that Vellumoid (cellulose fibers-reinforced glycerin and protein) may leach protein and Polyvinyl Chloride (PVC) may leach plasticizer (such as Bis-Ethylhexyl-Phthalates) into the NGS solvent. Either case will not impact decontamination or immobilization operations at Savannah River Site (SRS). Some applications have zero tolerance for dimensional changes such as the operation of valves while other applications a finite dimensional change improves the function of the application such as seals and gaskets. Additional considerations are required before using the conclusions from this work to judge outcomes in field applications. Decane, a component of Isopar L that is most likely to interact with the polymers, mildly interacted with the elastomers and the propylene based polymers but their degree of swelling is at most 10% and the confined geometry that they are typically placed in indicate this is not significant. In addition, it was found that Vellumoid may leach protein into the NGS solvent. Since Vellumoid is used at the mixer in Saltstone where it sees minimum quantities of solvent, this leaching has no effect on the extraction process at MCU or the immobilization process at saltstone. No significant interaction is expected between MaxCalix and the polymers and elastomers used at MCU, DWPF, and Saltstone. Overall, minimal and insignificant interactions are expected on extraction and immobilization operations when MCU switches from CSSX to NGS solvent. It is expected that contacting NGS will not accelerate the aging rate of polymers and elastomers under radiation and heat. This is due to the minimal interaction between NGS and the polymers and the confined geometries for these polymers. SRNL recommends the use of the HSP method (for screening) and some testing to evaluate the impact of other organic such as alcohols, glycolate, and their byproducts on the polymers used throughout the site.« less

Fabrication and characterization of novel polymer-matrix nanocomposites and their constituents

NASA Astrophysics Data System (ADS)

Ding, Rui

Two main issues for the wide application of polymer-matrix nanocomposites need to be addressed: cost-effective processing of high-performance nanomaterials, and fundamental understanding of the nanofiller-polymer interaction related to property changes of nanocomposites. To fabricate inexpensive and robust carbon nanofibers (CNFs) by the electrospinning technique, an organosolv lignin for replacing polyacrylonitrile (PAN) precursor was investigated in this work. Modification of lignin to its butyl ester alters the electrospinnability and the thermal mobility of the lignin/PAN blend precursor fibers, which further affect the thermostabilization and carbonization processes of CNFs. The micromorphology, carbon structure, and mechanical properties of resultant CNFs were evaluated in detail. Lignin butyration reveals a new approach to controlling inter-fiber bonding of CNFs which efficiently increases the tensile strength and modulus of nonwoven mats. A commercial vapor-grown CNF reinforcing of room-temperature-vulcanized (RTV) polysiloxane foam has potential impact on the residual tin catalyst in composites and consequently the aging and the long-term performance of the materials. Elemental spectra and mapping were employed to analyze the distribution and the composition of tin catalyst residues in the CNF/polysiloxane composites. Thermal analysis revealed a significant increase of thermal stability for CNF-filled composites. Further, the glass transition properties of polysiloxane are not evidently influenced by the physical interaction between CNF filler and polysiloxane matrix. Nanocomposites consisting of anthracene, a model polycyclic aromatic hydrocarbon (PAH) compound, and a thermosetting epoxy was matrix was studied to interpret the reinforcing effect on the glass transition temperature ( Tg) by different routes: physical dispersion and/or covalent modification. The molecular dynamics of the relaxation processes were analyzed by broadband dielectric spectroscopy (BDS). By parametric fitting using the Havriliak-Negami (HN) function, the Arrhenius diagram was obtained to evaluate the temperature dependence of the relaxation processes at different length scales for the nanocomposites. The segmental alpha relaxation was strongly affected by the reinforcing approaches and the correlation of T g-scaled fragility to molecular structures provides the explanation for the mechanisms of the nanofiller-polymer interaction. In addition, the accelerated chemical aging of nylon 6 polymer, a common material for wire insulations, was monitored by a nondestructive dielectric/capacitive method. The correlation between dielectric properties and electrical breakdown strength was found dependent on the polarity of the aircraft fluids to which nylon 6 was exposed. It was concluded that permittivity/capacitance measurement offers a feasible nondestructive method for diagnosing the breakdown strength of chemically immersed nylon 6.

The use of DMA to characterize the aging of asphalt binders.

DOT National Transportation Integrated Search

2010-06-01

This report presents issues associated with long-term aging of polymer modified asphalt cements (PMACs) as : reflected by dynamic mechanical analysis (DMA) data. In this study a standard SBS (styrene-butadiene-styrene block : copolymer) polymer modif...

Thermomechanical Properties and Glass Dynamics of Polymer-Tethered Colloidal Particles and Films

PubMed Central

2017-01-01

Polymer-tethered colloidal particles (aka “particle brush materials”) have attracted interest as a platform for innovative material technologies and as a model system to elucidate glass formation in complex structured media. In this contribution, Brillouin light scattering is used to sequentially evaluate the role of brush architecture on the dynamical properties of brush particles in both the individual and assembled (film) state. In the former state, the analysis reveals that brush–brush interactions as well as global chain relaxation sensitively depend on grafting density; i.e., more polymer-like behavior is observed in sparse brush systems. This is interpreted to be a consequence of more extensive chain entanglement. In contrast, the local relaxation of films does not depend on grafting density. The results highlight that relaxation processes in particle brush-based materials span a wider range of time and length scales as compared to linear chain polymers. Differentiation between relaxation on local and global scale is necessary to reveal the influence of molecular structure and connectivity on the aging behavior of these complex systems. PMID:29755139

Thermomechanical Properties and Glass Dynamics of Polymer-Tethered Colloidal Particles and Films.

PubMed

Cang, Yu; Reuss, Anna N; Lee, Jaejun; Yan, Jiajun; Zhang, Jianan; Alonso-Redondo, Elena; Sainidou, Rebecca; Rembert, Pascal; Matyjaszewski, Krzysztof; Bockstaller, Michael R; Fytas, George

2017-11-14

Polymer-tethered colloidal particles (aka "particle brush materials") have attracted interest as a platform for innovative material technologies and as a model system to elucidate glass formation in complex structured media. In this contribution, Brillouin light scattering is used to sequentially evaluate the role of brush architecture on the dynamical properties of brush particles in both the individual and assembled (film) state. In the former state, the analysis reveals that brush-brush interactions as well as global chain relaxation sensitively depend on grafting density; i.e., more polymer-like behavior is observed in sparse brush systems. This is interpreted to be a consequence of more extensive chain entanglement. In contrast, the local relaxation of films does not depend on grafting density. The results highlight that relaxation processes in particle brush-based materials span a wider range of time and length scales as compared to linear chain polymers. Differentiation between relaxation on local and global scale is necessary to reveal the influence of molecular structure and connectivity on the aging behavior of these complex systems.

Hydrophilization and hydrophobic recovery in polymers obtained by casting of polymer solutions on water surface.

PubMed

Bormashenko, Edward; Chaniel, Gilad; Gendelman, Oleg

2014-12-01

We demonstrate the possibility of hydrophilization of polymer films in situ under the process of their preparation. The polymer surface is hydrophilized when the polymer solution is spread on the water surface and the solvent is evaporated. Essential hydrophilization of the polymer surface is achieved under this process. We relate the observed hydrophilization of polymer films to the dipole-dipole interaction of the polar moieties of polymer chains with highly polar water molecules. The dipole-dipole interaction between water molecules and polar groups of polymer chains, orienting the polar groups of a polymer, may prevail over the London dispersion forces. The process, reported in the paper, allows to manufacture the films in which the hydrophilic moieties of the polymer molecule are oriented toward the polymer/air interface. It is demonstrated that even such traditionally extremely hydrophobic polymers as polydimethylsiloxane can be markedly hydrophilized. This hydrophilization, however, does not persist forever. After removal from the water surface, hydrophobic recovery was observed, i.e. polymer films restored their hydrophobicity with time. The characteristic time of the hydrophobic recovery is on the order of magnitude of hours. Copyright © 2014 Elsevier Inc. All rights reserved.

Comparison of Graphite Fabric Reinforced PMR-15 and Avimid N Composites After Long Term Isothermal Aging at Various Temperatures

NASA Technical Reports Server (NTRS)

Bowles, Kenneth J.; McCorkle, Linda; Ingrahm, Linda

1998-01-01

Extensive effort is currently being expended to demonstrate the feasibility of using high-performance, polymer-matrix composites as engine structural materials over the expected operating lifetime of the aircraft, which can extend from 18,000 to 30,000 hr. The goal is to develop light-weight, high-strength, and high-modulus materials for use in higher temperature sections of advanced 21 st century aircraft propulsion systems. To accomplish this goal, it is necessary to pursue the development of thermal and mechanical durability models for graphite-fiber-reinforced, polymer-matrix composites. Numerous investigations have been reported regarding the thermo-oxidative stability (TOS) of the polyimide PMR-15 (1-5). A significant amount of this work has been directed at edge and geometry effects, reinforcement fiber influences, and empirical modeling of high-temperature weight loss behavior. It is yet to be determined if the information obtained from the PMR-15 composite tests is applicable to other polyimide-matrix composites. The condensation-curing polymer Avimid N is another advanced composite material often considered for structural applications at high temperatures. Avimid N has better thermo-oxidative stability than PMR-15 (6), but the latter is more easily processed. The most comprehensive study of the thermo-oxidative stability of Avimid N neat resin and composites at 371 (infinity)C is found in Salin and Seferis (7). The purposes of the work described herein were to compare the thermal aging behavior of these two matrix polymers and to determine the reasons for and the consequences of the difference in thermal durability. These results might be of some use in improving future polymer development through the incorporation of the desirable characteristics of both polyimides.

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

Cao, Peng -Fei; Li, Bingrui; Hong, Tao

Here, polymer membranes with the capability to process a massive volume of gas are especially attractive for practical applications of gas separation. Although much effort has been devoted to develop novel polymer membranes with increased selectivity, the overall gas-separation performance and lifetime of membrane are still negatively affected by the weak mechanical performance, low plasticization resistance and poor physical aging tolerance. Recently, elastic polymer membranes with tunable mechanical properties have been attracting significant attentions due to their tremendous potential applications. Herein, we report a series of urethanerich PDMS-based polymer networks (U-PDMS-NW) with improved mechanical performance for gas separation. The cross-linkmore » density of U-PDMS-NWs is tailored by varying the molecular weight ( M n) of PDMS. The U-PDMS-NWs show up to 400% elongation and tunable Young’s modulus (1.3–122.2 MPa), ultimate tensile strength (1.1–14.3 MPa), and toughness (0.7–24.9 MJ/m 3). All of the U-PDMS-NWs exhibit salient gas-separation performance with excellent thermal resistance and aging tolerance, high gas permeability (>100 Barrer), and tunable gas selectivity (up to α[ P CO2/ P N2] ≈ 41 and α[ P CO2/ P CH4] ≈ 16). With well-controlled mechanical properties and gas-separation performance, these U-PDMS-NW can be used as a polymermembrane platform not only for gas separation but also for other applications such as microfluidic channels and stretchable electronic devices.« less

Effects of physical aging on long-term creep of polymers and polymer matrix composites

NASA Technical Reports Server (NTRS)

Brinson, L. Catherine; Gates, Thomas S.

1994-01-01

For many polymeric materials in use below the glass transition temperature, the long term viscoelastic behavior is greatly affected by physical aging. To use polymer matrix composites as critical structural components in existing and novel technological applications, this long term behavior of the material system must be understood. Towards that end, this study applied the concepts governing the mechanics of physical aging in a consistent manner to the study of laminated composite systems. Even in fiber-dominated lay-ups the effects of physical aging are found to be important in the long-term behavior of the composite. The basic concepts describing physical aging of polymers are discussed. Several aspects of physical aging which have not been previously documented are also explored in this study, namely the effects of aging into equilibrium and a relationship to the time-temperature shift factor. The physical aging theory is then extended to develop the long-term compliance/modulus of a single lamina with varying fiber orientation. The latter is then built into classical lamination theory to predict long-time response of general oriented lamina and laminates. It is illustrated that the long term response can be counterintuitive, stressing the need for consistent modeling efforts to make long term predictions of laminates to be used in structural situations.

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

NASA Technical Reports Server (NTRS)

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

1991-01-01

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

Method for separating water soluble organics from a process stream by aqueous biphasic extraction

DOEpatents

Chaiko, David J.; Mego, William A.

1999-01-01

A method for separating water-miscible organic species from a process stream by aqueous biphasic extraction is provided. An aqueous biphase system is generated by contacting a process stream comprised of water, salt, and organic species with an aqueous polymer solution. The organic species transfer from the salt-rich phase to the polymer-rich phase, and the phases are separated. Next, the polymer is recovered from the loaded polymer phase by selectively extracting the polymer into an organic phase at an elevated temperature, while the organic species remain in a substantially salt-free aqueous solution. Alternatively, the polymer is recovered from the loaded polymer by a temperature induced phase separation (cloud point extraction), whereby the polymer and the organic species separate into two distinct solutions. The method for separating water-miscible organic species is applicable to the treatment of industrial wastewater streams, including the extraction and recovery of complexed metal ions from salt solutions, organic contaminants from mineral processing streams, and colorants from spent dye baths.

Impact of polymer film thickness and cavity size on polymer flow during embossing : towards process design rules for nanoimprint lithography.

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

Schunk, Peter Randall; King, William P.; Sun, Amy Cha-Tien

2006-08-01

This paper presents continuum simulations of polymer flow during nanoimprint lithography (NIL). The simulations capture the underlying physics of polymer flow from the nanometer to millimeter length scale and examine geometry and thermophysical process quantities affecting cavity filling. Variations in embossing tool geometry and polymer film thickness during viscous flow distinguish different flow driving mechanisms. Three parameters can predict polymer deformation mode: cavity width to polymer thickness ratio, polymer supply ratio, and Capillary number. The ratio of cavity width to initial polymer film thickness determines vertically or laterally dominant deformation. The ratio of indenter width to residual film thickness measuresmore » polymer supply beneath the indenter which determines Stokes or squeeze flow. The local geometry ratios can predict a fill time based on laminar flow between plates, Stokes flow, or squeeze flow. Characteristic NIL capillary number based on geometry-dependent fill time distinguishes between capillary or viscous driven flows. The three parameters predict filling modes observed in published studies of NIL deformation over nanometer to millimeter length scales. The work seeks to establish process design rules for NIL and to provide tools for the rational design of NIL master templates, resist polymers, and process parameters.« less

Rheological changes of polyamide 12 under oscillatory shear

NASA Astrophysics Data System (ADS)

Mielicki, C.; Gronhoff, B.; Wortberg, J.

2014-05-01

Changes in material properties as well as process deviation prevent Laser Sintering (LS) technology from manufacturing of quality assured parts in a series production. In this context, the viscosity of Polyamide 12 (PA12) is assumed to possess the most significant influence, as it determines the sintering velocity, the resistance towards melt formation and the bonding strength of sintered layers. Moreover, the viscosity is directly related to the structure of the molten polymer. In particular, it has been recently reported that LS process conditions lead to structural changes of PA12 affecting viscosity and coalescence of adjacent polymer particles, i.e. melt formation significantly. Structural change of PA12 was understood as a post condensation. Its influence on viscosity was described by a time and temperature depending rheological model whereas time dependence was considered by a novel structural change shift factor which was derived from melt volume rate data. In combination with process data that was recorded using online thermal imaging, the model is suitable to control the viscosity (processability of the material) as result of material and process properties. However, as soon as laser energy is exposed to the powder bed PA12 undergoes a phase transition from solid to molten state. Above the melting point, structural change is expected to occur faster due to a higher kinetic energy and free volume of the molten polymer. Oscillatory shear results were used to study the influence of aging time and for validation of the novel structural change shift factor and its model parameters which were calibrated based on LS processing condition.

Effects of physical aging on long-term behavior of composites

NASA Technical Reports Server (NTRS)

Brinson, L. Catherine

1993-01-01

The HSCT plane, envisioned to have a lifetime of over 60,000 flight hours and to travel at speeds in excess of Mach 2, is the source of intensive study at NASA. In particular, polymer matrix composites are being strongly considered for use in primary and secondary structures due to their high strength to weight ratio and the options of property tailoring. However, an added difficulty in the use of polymer based materials is that their properties change significantly over time, especially at the elevated temperatures that will be experienced during flight, and prediction of properties based on irregular thermal and mechanical loading is extremely difficult. This study focused on one aspect of long-term polymer composite behavior: physical aging. When a polymer is cooled to below its glass transition temperature, the material is not in thermodynamic equilibrium and the free volume and enthalpy evolve over time to approach their equilibrium values. During this time, the mechanical properties change significantly and this change is termed physical aging. This work begins with a review of the concepts of physical aging on a pure polymer system. The effective time theory, which can be used to predict long term behavior based on short term data, is mathematically formalized. The effects of aging to equilibrium are proven and discussed. The theory developed for polymers is then applied first to a unidirectional composite, then to a general laminate. Comparison to experimental data is excellent. It is shown that the effects of aging on the long-term properties of composites can be counter-intuitive, stressing the importance of the development and use of a predictive theory to analyze structures.

Aqueous Nanoparticle Polymer Solar Cells: Effects of Surfactant Concentration and Processing on Device Performance

PubMed Central

2017-01-01

Polymer solar cells based on PDPP5T and PCBM as donor and acceptor materials, respectively, were processed from aqueous nanoparticle dispersions. Careful monitoring and optimization of the concentration of free and surface-bound surfactants in the dispersion, by measuring the conductivity and ζ-potential, is essential to avoid aggregation of nanoparticles at low concentration and dewetting of the film at high concentration. The surfactant concentration is crucial for creating reproducible processing conditions that aid in further developing aqueous nanoparticle processed solar cells. In addition, the effects of adding ethanol, of aging the dispersion, and of replacing [60]PCBM with [70]PCBM to enhance light absorption were studied. The highest power conversion efficiencies (PCEs) obtained are 2.0% for [60]PCBM and 2.4% for [70]PCBM-based devices. These PCEs are limited by bimolecular recombination of photogenerated charges. Cryo-TEM reveals that the two components phase separate in the nanoparticles, forming a PCBM-rich core and a PDPP5T-rich shell and causing a nonoptimal film morphology. PMID:28345859

A Course in Polymer Processing.

ERIC Educational Resources Information Center

Soong, David S.

1985-01-01

A special-topics course in polymer processing has acquired regular course status. Course goals, content (including such new topics as polymer applications in microelectronics), and selected term projects are described. (JN)

Processing Conjugated-Diene-Containing Polymers

NASA Technical Reports Server (NTRS)

Bell, Vernon L.; Havens, Stephen J.

1987-01-01

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.

Accelerated optical polymer aging studies for LED luminaire applications

NASA Astrophysics Data System (ADS)

Estupiñán, Edgar; Wendling, Peter; Kostrun, Marijan; Garner, Richard

2013-09-01

There is a need in the lighting industry to design and implement accelerated aging methods that accurately simulate the aging process of LED luminaire components. In response to this need, we have built a flexible and reliable system to study the aging characteristics of optical polymer materials, and we have employed it to study a commercially available LED luminaire diffuser made of PMMA. The experimental system consists of a "Blue LED Emitter" and a working surface. Both the temperatures of the samples and the optical powers of the LEDs are appropriately characterized in the system. Several accelerated aging experiments are carried out at different temperatures and optical powers over a 90 hour period and the measured transmission values are used as inputs to a degradation model derived using plausibility arguments. This model seems capable of predicting the behavior of the material as a function of time, temperature and optical power. The model satisfactorily predicts the measured transmission values of diffusers aged in luminaires at two different times and thus can be used to make application recommendations for this material. Specifically, at 35000 hours (the manufacturer's stated life of the luminaire) and at the typical operational temperature of the diffuser, the model predicts a transmission loss of only a few percent over the original transmission of the material at 450 nm, which renders this material suitable for this application.

Chemical stabilization of polymers: Implications for dermal exposure to additives.

PubMed

Bartsch, N; Girard, M; Schneider, L; Weijgert, V Van De; Wilde, A; Kappenstein, O; Vieth, B; Hutzler, C; Luch, A

2018-04-16

Technical benefits of additives in polymers stand in marked contrast to their associated health risks. Here, a multi-analyte method based on gas chromatography coupled to tandem mass spectrometry (GC-MS/MS) was developed to quantify polymer additives in complex matrices such as low-density polyethylene (LDPE) and isolated human skin layers after dermal exposure ex vivo. That way both technical aspects and dermal exposure were investigated. The effects of polymer additivation on the material were studied using the example of LDPE. To this end, a tailor-made polymer was applied in aging studies that had been furnished with two different mixtures of phenol- and diarylamine-based antioxidants, plasticizers and processing aids. Upon accelerated thermo-oxidative aging of the material, the formation of LDPE degradation products was monitored with attenuated total reflectance-Fourier transformed infrared (ATR-FTIR) spectroscopy. Compared to pure LDPE, a protective effect of added antioxidants could be observed on the integrity of the polymer. Further, thermo-oxidative degradation of the additives and its kinetics were investigated using LDPE or squalane as matrix. The half-lives of additives in both matrices revealed significant differences between the tested additives as well as between LDPE and squalane. For instance, 2-tert-butyl-6-[(3-tert-butyl-2-hydroxy-5-methylphenyl)methyl]-4-methylphenol (Antioxidant 2246) showed a half-life 12 times lower when incorporated in LDPE as compared to squalane. As a model for dermal exposure of consumers, human skin was brought into contact with the tailor-made LDPE containing additives ex vivo in static Franz diffusion cells. The skin was then analyzed for additives and decomposition products. This study proved 10 polymer additives of diverse pysicochemical properties and functionalities to migrate out of the polymer and eventually overcome the intact human skin barrier during contact. Moreover, their individual distribution within distinct skin layers was demonstrated. This is exemplified by the penetration of the procarcinogenic antioxidant N-phenylnaphthalen-2-amine (Neozon D) into the viable epidermis and the permeation through the skin of the neurotoxic plasticizer N-butylbenzenesulfonamide (NBBS). In addition, the analyses of additive degradation products in the isolated skin layers revealed the presence of 2-tert-butyl-4-methylphenol in all layers after contact to a polymer with substances of origin like Antioxidant 2246. Thus, attention needs to be paid to absorption of polymer additives together with their degradation products when it comes to dermal exposure assessment.

Using in-situ polymerization of conductive polymers to enhance the electrical properties of solution-processed carbon nanotube films and fibers.

PubMed

Allen, Ranulfo; Pan, Lijia; Fuller, Gerald G; Bao, Zhenan

2014-07-09

Single-walled carbon nanotubes/polymer composites typically have limited conductivity due to a low concentration of nanotubes and the insulating nature of the polymers used. Here we combined a method to align carbon nanotubes with in-situ polymerization of conductive polymer to form composite films and fibers. Use of the conducting polymer raised the conductivity of the films by 2 orders of magnitude. On the other hand, CNT fiber formation was made possible with in-situ polymerization to provide more mechanical support to the CNTs from the formed conducting polymer. The carbon nanotube/conductive polymer composite films and fibers had conductivities of 3300 and 170 S/cm, respectively. The relatively high conductivities were attributed to the polymerization process, which doped both the SWNTs and the polymer. In-situ polymerization can be a promising solution-processable method to enhance the conductivity of carbon nanotube films and fibers.

A Green Method for Processing Polymers using Dense Gas Technology

PubMed Central

Yoganathan, Roshan B.; Mammucari, Raffaella; Foster, Neil R.

2010-01-01

Dense CO2 can be used as an environmentally-benign polymer processing medium because of its liquid-like densities and gas-like mass transfer properties.In this work, polymer bio-blends of polycarbonate (PC), a biocompatible polymer, and polycaprolactone (PCL), a biodegradable polymer were prepared. Dense CO2 was used as a reaction medium for the melt-phase PC polymerization in the presence of dense CO2-swollen PCL particles and this method was used to prepare porous PC/PCL blends. To extend the applicability of dense CO2 to the biomedical industry and polymer blend processing, the impregnation of ibuprofen into the blend was conducted and subsequent dissolution characteristics were observed.

Chemical degradation and morphological instabilities during focused ion beam prototyping of polymers.

PubMed

Orthacker, A; Schmied, R; Chernev, B; Fröch, J E; Winkler, R; Hobisch, J; Trimmel, G; Plank, H

2014-01-28

Focused ion beam processing of low melting materials, such as polymers or biological samples, often leads to chemical and morphological instabilities which prevent the straight-forward application of this versatile direct-write structuring method. In this study the behaviour of different polymer classes under ion beam exposure is investigated using different patterning parameters and strategies with the aim of (i) correlating local temperatures with the polymers' chemistry and its morphological consequences; and (ii) finding a way of processing sensitive polymers with lowest chemical degradation while maintaining structuring times. It is found that during processing of polymers three temperature regimes can be observed: (1) at low temperatures all polymers investigated show stable chemical and morphological behaviour; (2) very high temperatures lead to strong chemical degradation which entails unpredictable morphologies; and (3) in the intermediate temperature regime the behaviour is found to be strongly material dependent. A detailed look reveals that polymers which rather cross-link in the proximity of the beam show stable morphologies in this intermediate regime, while polymers that rather undergo chain scission show tendencies to develop a creeping phase, where material follows the ion beam movement leading to instable and unpredictable morphologies. Finally a simple, alternative patterning strategy is suggested, which allows stable processing conditions with lowest chemical damage even for challenging polymers undergoing chain scission.

Dynamics of Hyperbranched Polymers under Confinement

NASA Astrophysics Data System (ADS)

Androulaki, Krystallenia; Chrissopoulou, Kiriaki; Anastasiadis, Spiros H.; Prevosto, Daniele; Labardi, Massimiliano

2015-03-01

The effect of severe confinement on the dynamics of three different generations of hyperbranched polyesters (Boltorns) is investigated by Dielectric Spectroscopy. The polymers are intercalated within the galleries of natural Na+-MMT, thus, forming 1nm polymer films confined between solid walls. The Tg's of the polymers determined by DSC show a clear dependence on the generation whereas the transition is completely suppressed when all the polymer chains are intercalated. The dynamic investigation of the bulk polymers reveals two sub-Tg processes, with similar behavior for the three polymers with the segmental relaxation observed above the Tg of each. For the nanocomposites, where all polymers are severely confined, the dynamics show significant differences compared to that of the bulk polymers. The sub-Tg processes are similar for the three generations but significantly faster and with weaker temperature dependence than those in the bulk. The segmental process appears at temperatures below the bulk polymer Tg, it exhibits an Arrhenius temperature dependence and shows differences for the three generations. A slow process that appears at higher temperatures is due to interfacial polarization. Co-financed by the EU and Greek funds through the Operational Program ``Education and Lifelong Learning'' of the NSRF-Research Funding Program: THALES-Investing in knowledge society through the Eur. Social Fund (MIS 377278) and COST Action MP0902-COINAPO.

Polymer surface treatment with particle beams

DOEpatents

Stinnett, Regan W.; VanDevender, J. Pace

1999-01-01

A polymer surface and near surface treatment process produced by irradiation with high energy particle beams. The process is preferably implemented with pulsed ion beams. The process alters the chemical and mechanical properties of the polymer surface in a manner useful for a wide range of commercial applications.

Modeling High-Pressure Gas-Polymer Sorpion Behavior Using the Sanchez-Lacombe Equation of State.

DTIC Science & Technology

1987-06-01

The solubility of a gas in an amorphous or molten polymer is an important consideration in membrane and polymer processes . For instance, the efficacy...to a supercritical fluid during the impregnation process . Swelling the polymer effectively increases the diffusion coefficient of the heavy dopant by...dissolve the impurity, and then diffuse out of the swollen matrix thus removing the impurity. This supercritical fluid extraction process is somewhat

Vacuum-deposited polymer/silver reflector material

NASA Astrophysics Data System (ADS)

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

1994-09-01

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

Conjugated Polymers Atypically Prepared in Water

PubMed Central

Invernale, Michael A.; Pendergraph, Samuel A.; Yavuz, Mustafa S.; Ombaba, Matthew; Sotzing, Gregory A.

2010-01-01

Processability remains a fundamental issue for the implementation of conducting polymer technology. A simple synthetic route towards processable precursors to conducting polymers (main chain and side chain) was developed using commercially available materials. These soluble precursor systems were converted to conjugated polymers electrochemically in aqueous media, offering a cheaper and greener method of processing. Oxidative conversion in aqueous and organic media each produced equivalent electrochromics. The precursor method enhances the yield of the electrochromic polymer obtained over that of electrodeposition, and it relies on a less corruptible electrolyte bath. However, electrochemical conversion of the precursor polymers often relies on organic salts and solvents. The ability to achieve oxidative conversion in brine offers a less costly and a more environmentally friendly processing step. It is also beneficial for biological applications. The electrochromics obtained herein were evaluated for electronic, spectral, and morphological properties. PMID:20959869

Incorporation of additives into polymers

DOEpatents

McCleskey, T. Mark; Yates, Matthew Z.

2003-07-29

There has been invented a method for incorporating additives into polymers comprising: (a) forming an aqueous or alcohol-based colloidal system of the polymer; (b) emulsifying the colloidal system with a compressed fluid; and (c) contacting the colloidal polymer with the additive in the presence of the compressed fluid. The colloidal polymer can be contacted with the additive by having the additive in the compressed fluid used for emulsification or by adding the additive to the colloidal system before or after emulsification with the compressed fluid. The invention process can be carried out either as a batch process or as a continuous on-line process.

Graywater Discharges from Vessels

DTIC Science & Technology

2011-11-01

soaps and detergents used in any capacity that will be discharged as part of graywater must be nontoxic and phosphate -free, and should be...mounted on one skid. The Evac MBR process is fully automated and controlled through a PLC. Evac uses high quality Kubota membranes. Kubota membranes...the best solution. • Non- corrosive . By choosing to use non- corrosive materials (including a special space age polymer yielding strength and

Polymer surface treatment with particle beams

DOEpatents

Stinnett, R.W.; VanDevender, J.P.

1999-05-04

A polymer surface and near surface treatment process produced by irradiation with high energy particle beams is disclosed. The process is preferably implemented with pulsed ion beams. The process alters the chemical and mechanical properties of the polymer surface in a manner useful for a wide range of commercial applications. 16 figs.

Solution-processable ambipolar diketopyrrolopyrrole-selenophene polymer with unprecedentedly high hole and electron mobilities.

PubMed

Lee, Junghoon; Han, A-Reum; Kim, Jonggi; Kim, Yiho; Oh, Joon Hak; Yang, Changduk

2012-12-26

There is a fast-growing demand for polymer-based ambipolar thin-film transistors (TFTs), in which both n-type and p-type transistor operations are realized in a single layer, while maintaining simplicity in processing. Research progress toward this end is essentially fueled by molecular engineering of the conjugated backbones of the polymers and the development of process architectures for device fabrication, which has recently led to hole and electron mobilities of more than 1.0 cm(2) V(-1) s(-1). However, ambipolar polymers with even higher performance are still required. By taking into account both the conjugated backbone and side chains of the polymer component, we have developed a dithienyl-diketopyrrolopyrrole (TDPP) and selenophene containing polymer with hybrid siloxane-solubilizing groups (PTDPPSe-Si). A synergistic combination of rational polymer backbone design, side-chain dynamics, and solution processing affords an enormous boost in ambipolar TFT performance, resulting in unprecedentedly high hole and electron mobilities of 3.97 and 2.20 cm(2) V(-1) s(-1), respectively.

In situ creation of reactive polymer nanoparticles and resulting polymer layers formed at the interfaces of liquid crystals (Conference Presentation)

NASA Astrophysics Data System (ADS)

Kang, Shin-Woong; Kundu, Sudarshan; Park, Heung-Shik; Oh, Keun Chan; Lyu, Jae Jin

2017-02-01

We report the in situ creation of reactive polymer nanoparticles and resulting polymer networks formed at the interfaces of liquid crystals. It is known that polymerization-induced phase separation proceeds in two distinct regimes depending on the concentration of monomer. For a high monomer concentration, phase separation occurs mainly through the spinodal decomposition process, consequently resulting in interpenetrating polymer networks. For a dilute system, however, the phase separation mainly proceeds and completes in the binodal decomposition regime. The system resembles the aggregation process of colloidal particle. In this case, the reaction kinetics is limited by the reaction between in situ created polymer aggregates and hence the network morphologies are greatly influenced by the diffusion of reactive polymer particles. The thin polymer layers localized at the surface of substrate are inevitably observed and can be comprehended by the interfacial adsorption and further cross-linking reaction of reactive polymer aggregates at the interface. This process provides a direct perception on understanding polymer stabilized liquid crystals accomplished by the interfacial polymer layer. The detailed study has been performed for an extremely dilute condition (below 0.5 wt%) by employing systematic experimental approaches. Creation and growth of polymer nanoparticles have been measured by particle size analyzer. The interfacial localization of polymer aggregates and resulting interfacial layer formation with a tens of nanometer scale have been exploited at various interfaces such as liquid-solid, liquid-liquid, and liquid-gas interfaces. The resulting interfacial layers have been characterized by using fuorescent confocal microscope and field emission scanning electron microscope. The detailed processes of the polymer stabilized vertically aligned liquid crystals will be discussed in support of the reported study.

ESR Analysis of Polymer Photo-Oxidation

NASA Technical Reports Server (NTRS)

Kim, Soon Sam; Liang, Ranty Hing; Tsay, Fun-Dow; Gupta, Amitave

1987-01-01

Electron-spin resonance identifies polymer-degradation reactions and their kinetics. New technique enables derivation of kinetic model of specific chemical reactions involved in degradation of particular polymer. Detailed information provided by new method enables prediction of aging characteristics long before manifestation of macroscopic mechanical properties.

Corrosive effect of environmental change on selected properties of polymer composites

NASA Astrophysics Data System (ADS)

Markovičová, L.; Zatkalíková, V.

2017-11-01

The development of composite materials and the related design and manufacturing technologies is one of the most important advances in the history of materials. Composites are multifunctional materials having unprecedented mechanical and physical properties that can be tailored to meet the requirements of a particular application. Ageing is also important and it is defined as the process of deterioration of engineering materials resulting from the combined effects of atmospheric radiation, heat, oxygen, water, micro-organisms and other atmospheric factors. The present article deals with monitoring the changes in the mechanical properties of composites with polymer matrix. The composite was formed from the PA matrix and glass fibers (GF). The composite contains 10, 20 and 30 % of glass fibers. The mechanical properties were evaluated on samples of the composite before and after UV radiation on the sample. Light microscopy was evaluated distribution of glass fibers in the polymer matrix and the presence of cracks caused by UV radiation.

Influence of Water on Tribological Properties of Wood-Polymer Composites

NASA Astrophysics Data System (ADS)

Mysiukiewicz, Olga; Sterzyński, Tomasz

2017-08-01

Utilization of ecological materials for appliances and products is one of the ways to achieve the goal of sustainability.Wood-polymer composites as a cheap, lightweight, durable and esthetic material has gained attention of scientists, engineers and consumers alike. Different kinds of polymeric matrices, plants used as the fillers, chemical of physical modifiers and processing technologies have already been widely studied. Nonetheless, surprisingly few information on Wood-Polymer Composites' tribology can be found. This paper is an attempt to fill this gap. Polypropylene-and poly(lactic acid)-based composites with varying wood flour content have been analyzed. The Brinell's hardness and coefficient of friction of the samples have been determined. In order to evaluate the influence of the moisture content on the tribological and mechanical properties of the composites, the samples have also been aged in water. The investigation revealed that polymeric composites filled with wood flour can present favorable coefficient of friction, compared to the neat resins. The results of our study can establish a good starting point for further investigation.

Oxidative Degradation of Nadic-End-Capped Polyimides. 2; Evidence for Reactions Occurring at High Temperatures

NASA Technical Reports Server (NTRS)

Meador, Mary Ann B.; Johnston, J. Christopher; Cavano, Paul J.; Frimer, Aryeh A.

1997-01-01

The oxidative degradation of PMR (for polymerization of monomeric reactants) polyimides at elevated temperatures was followed by cross-polarized magic angle spinning (Cp-MAS) NMR. C-13 labeling of selected sites in the polymers allowed for direct observation of the transformations arising from oxidation processes. As opposed to model compound studies, the reactions were followed directly in the polymer. The labeling experiments confirm the previously reported oxidation of the methylene carbon to ketone in the methylenedianiline portion of the polymer chain. They also show the formation of two other oxidized species, acid and ester, from this same carbon. In addition, the technique provides the first evidence of the kind of degradation reactions that are occurring in the nadic end caps. Several PMR formulations containing moieties determined to be present after oxidation, as suggested by the labeling study, were synthesized. Weight loss, FTIR, and natural abundance NMR of these derivatives were followed during aging. In this way, weight loss could be related to the observed transformations.

Thermal oxidative degradation of ethylene tetrafluoroethylene copolymer systems

NASA Astrophysics Data System (ADS)

Elders, Jonathan Patrick

Thermo-oxidative degradation of ethylene tetrafluoroethylene (ETFE) was investigated to determine how modifications for use in an electrical wire system affected its thermal stability. Modifications included electron irradiation and subsequent cross-linking during manufacture and contact with a metal surface. Samples with irradiation histories between 0 and 48 MRads were investigated. Degradation of ETFE was enhanced by contact with a metal "conductor" surface: silver - coated copper. Polymer degradation was analyzed by weight loss kinetics (thermogravimetric analysis (TGA)), changes in polymer morphology (differential scanning calorimetry (DSC)), optical microscopy, attenuated total reflectance (ATR) infrared spectroscopy, and gas chromatography - mass spectroscopy (GC/MS). Conductor aging (copper permeation through silver with subsequent oxidation) was investigated using scanning Auger Electron Spectroscopy (AES). Conductor aging is enhanced in the presence of the polymer surface. Interactions between conductor and polymer were analyzed by optical microscopy, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The rate of polymer degradation from 220°C to 280°C was independent of time and extent of degradation, and rate was proportional to irradiation dose. The activation energy for degradation of unirradiated ETFE was 227 kJ/mol and decreased from 150 to 138 kJ/mol for ETFE irradiated to doses between 6 and 48 MRads. Rates of degradation at 300°C to 320°C were dependent on the extent of degradation. Rates of degradation at temperatures between 230°C and 310°C were an order of magnitude larger in the presence of a conductor than in its absence, and activation energies for degradation in the presence of conductor were reduced to 120 kJ/mol. Degradation was modeled as the combination of bulk polymer degradation and catalytic degradation at the polymer-metal interface. ETFE aged at 250°C in the presence or absence of a conductor exhibited a double melting endotherm. ATR spectra of aged ETFE indicated polymer oxidation. Based on AES experiments, copper permeation during aging in the presence or absence of ETFE was consistent with Fickian diffusion. The coefficient for copper diffusion through silver was approximately 10 -15 cm2/second, and catalytic ETFE degradation was proportional to conductor aging. The copper oxidized on the surface to yield a material with a stoichiometric composition of Cu3O 2.

High aspect ratio template and method for producing same

NASA Technical Reports Server (NTRS)

Sakamoto, Jeff S. (Inventor); Weiss, James R. (Inventor); Fleurial, Jean-Pierre (Inventor); Kisor, Adam (Inventor); Tuszynski, Mark (Inventor); Stokols, Shula (Inventor); Holt, Todd Edward (Inventor); Welker, David James (Inventor); Breckon, Christopher David (Inventor)

2010-01-01

Millimeter to nano-scale structures manufactured using a multi-component polymer fiber matrix are disclosed. The use of dissimilar polymers allows the selective dissolution of the polymers at various stages of the manufacturing process. In one application, biocompatible matrixes may be formed with long pore length and small pore size. The manufacturing process begins with a first polymer fiber arranged in a matrix formed by a second polymer fiber. End caps may be attached to provide structural support and the polymer fiber matrix selectively dissolved away leaving only the long polymer fibers. These may be exposed to another product, such as a biocompatible gel to form a biocompatible matrix. The polymer fibers may then be selectively dissolved leaving only a biocompatible gel scaffold with the pores formed by the dissolved polymer fibers.

Modeling the Coupled Chemo-Thermo-Mechanical Behavior of Amorphous Polymer Networks.

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

Zimmerman, Jonathan A.; Nguyen, Thao D.; Xiao, Rui

2015-02-01

Amorphous polymers exhibit a rich landscape of time-dependent behavior including viscoelasticity, structural relaxation, and viscoplasticity. These time-dependent mechanisms can be exploited to achieve shape-memory behavior, which allows the material to store a programmed deformed shape indefinitely and to recover entirely the undeformed shape in response to specific environmental stimulus. The shape-memory performance of amorphous polymers depends on the coordination of multiple physical mechanisms, and considerable opportunities exist to tailor the polymer structure and shape-memory programming procedure to achieve the desired performance. The goal of this project was to use a combination of theoretical, numerical and experimental methods to investigate themore » effect of shape memory programming, thermo-mechanical properties, and physical and environmental aging on the shape memory performance. Physical and environmental aging occurs during storage and through exposure to solvents, such as water, and can significantly alter the viscoelastic behavior and shape memory behavior of amorphous polymers. This project – executed primarily by Professor Thao Nguyen and Graduate Student Rui Xiao at Johns Hopkins University in support of a DOE/NNSA Presidential Early Career Award in Science and Engineering (PECASE) – developed a theoretical framework for chemothermo- mechanical behavior of amorphous polymers to model the effects of physical aging and solvent-induced environmental factors on their thermoviscoelastic behavior.« less

Reducing the Cation Exchange Capacity of Lithium Clay to Form Better Dispersed Polymer-Clay Nanocomposites

NASA Technical Reports Server (NTRS)

Liang, Maggie

2004-01-01

Polymer-clay nanocomposites have exhibited superior strength and thermo- oxidative properties as compared to pure polymers for use in air and space craft; however, there has often been difficulty completely dispersing the clay within the matrices of the polymer. In order to improve this process, the cation exchange capacity of lithium clay is first lowered using twenty-four hour heat treatments of no heat, 130 C, 150 C, or 170 C to fixate the lithium ions within the clay layers so that they are unexchangeable. Generally, higher temperatures have generated lower cation exchange capacities. An ion exchange involving dodecylamine, octadecylamine, or dimethyl benzidine (DMBZ) is then employed to actually expand the clay galleries. X-ray diffraction and transmission electron microscopy can be used to determine whether the clay has been successfully exfoliated. Finally, resins of DMBZ with clay are then pressed into disks for characterization using dynamic mechanical analyzer and oven- aging techniques in order to evaluate their glass transition, modulus strength, and thermal-oxidative stability in comparison to neat DMBZ. In the future, they may also be tested as composites for flexural and laminar shear strength.

Characterization and recovery of polymers from mobile phone scrap.

PubMed

Kasper, Angela C; Bernardes, Andréa M; Veit, Hugo M

2011-07-01

Electronic scrap is part of a universally wide range of obsolete, defective, or used materials that need to be disposed of or recycled in an ecologically friendly manner. The present study focused on the polymers present in mobile phone scrap. In mobile phones, polymers are found in frames and in printed circuit boards (PCBs). The frames are mainly made of polymers whereas PCBs use a variety of material (polymers, ceramics, and metals) which makes recycling more difficult. As a first step, mobile phones were collected, separated by manufacturer/model, and weighed, and the principal polymer types identified. The frames and PCBs were processed separately. The metals in PCBs were separated out by an electrostatic separation process. The resulting polymeric material was identified and mixed with the polymers of frames to fabricate the samples. Two types of samples were made: one with polymeric frames, and the other with a mixture of frames and polymeric fraction from the PCBs. Both kinds of sample were fabricated by injection moulding. The samples were evaluated by mechanical tests (tensile, impact, and hardness) to verify the feasibility of recycling the polymers present in mobile phone scrap. The results demonstrated the technical viability of recovering polymers using mechanical processing followed by an injection process.

Methods and Materials for Selective Modification of Photopatterned Polymer Films.

DTIC Science & Technology

1999-06-28

reactivity templates (see below) formed by patterned irradiation of polymer films. In particular, the invention describes binding materials and processes ...image of the attached functional group) or that region of the polymer film left unexposed and unchanged during the aforementioned patterning process ...invention are accomplished by the structures and processes hereinafter 15 described. An aspect of the present invention is a process for modifying a

Dual aging behaviour in a clay-polymer dispersion.

PubMed

Zulian, Laura; Augusto de Melo Marques, Flavio; Emilitri, Elisa; Ruocco, Giancarlo; Ruzicka, Barbara

2014-07-07

Clay-polymer compounds have recently attracted increasing attention due to their intriguing physical properties in colloidal science and their rheological non-trivial behaviour in technological applications. Aqueous solutions of Laponite clay spontaneously age from a liquid up to an arrested state of different nature (gel or glass) depending on the colloidal volume fraction and ionic strength. We have investigated, through dynamic light scattering, how the aging dynamics of Laponite dispersions at fixed clay concentration (Cw = 2.0%) is modified by the addition of various amounts of poly(ethylene oxide) (PEO) (CPEO = (0.05 ÷ 0.50) %) at two different molecular weights (Mw = 100 kg mol(-1) and Mw = 200 kg mol(-1)). A surprising and intriguing phenomenon has been observed: the existence of a critical polymer concentration C that discriminates between two different aging dynamics. With respect to pure Laponite systems the aging will be assisted (faster) or hindered (slower) for PEO concentrations respectively lower (CPEO < C) or higher (CPEO > C) than the critical concentration. In this way a control on the aging dynamics of PEO-Laponite systems is obtained. A possible explanation based on the balance of competitive mechanisms related to the progressive saturation of the clay surface by polymers is proposed. This study shows how a real control on the aging speed of the PEO-Laponite system is at hand and renders possible a real control of the complex interparticle interaction potential.

Morphological control of inter-penetrating polymer networks

NASA Technical Reports Server (NTRS)

Hansen, Marion

1989-01-01

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.

Process for crosslinking and extending conjugated diene-containing polymers

NASA Technical Reports Server (NTRS)

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

1977-01-01

A process using a Diels-Alder reaction which increases the molecular weight and/or crosslinks polymers by reacting the polymers with bisunsaturated dienophiles is developed. The polymer comprises at least 75% by weight based on the reaction product, has a molecular weight of at least 5000 and a plurality of conjugated 1,3-diene systems incorporated into the molecular structure. A dienophile reaction with the conjugated 1,3-diene of the polymer is at least 1% by weight based on the reaction product. Examples of the polymer include polyesters, polyamides, polyethers, polysulfones and copolymers. The bisunsaturated dienophiles may include bis-maleimides, bis maleic and bis tumaric esters and amides. This method for expanding the molecular weight chains of the polymers, preferable thermoplastics, is advantageous for processing or fabricating thermoplastics. A low molecular weight thermoplastic is converted to a high molecular weight plastic having improved strength and toughness for use in the completed end use article.

Process for preparing polymer reinforced silica aerogels

NASA Technical Reports Server (NTRS)

Meador, Mary Ann B. (Inventor); Capadona, Lynn A. (Inventor)

2011-01-01

Process for preparing polymer-reinforced silica aerogels which comprises a one-pot reaction of at least one alkoxy silane in the presence of effective amounts of a polymer precursor to obtain a silica reaction product, the reaction product is gelled and subsequently subjected to conditions that promotes polymerization of the precursor and then supercritically dried to obtain the polymer-reinforced monolithic silica aerogels.

The in situ synthesis of PbS nanocrystals from lead(II) n-octylxanthate within a 1,3-diisopropenylbenzene–bisphenol A dimethacrylate sulfur copolymer

PubMed Central

Bear, J. C.; Mayes, A. G.; Parkin, I. P.; O'Brien, P.

2017-01-01

The synthesis of lead sulfide nanocrystals within a solution processable sulfur ‘inverse vulcanization’ polymer thin film matrix was achieved from the in situ thermal decomposition of lead(II) n-octylxanthate, [Pb(S2COOct)2]. The growth of nanocrystals within polymer thin films from single-source precursors offers a faster route to networks of nanocrystals within polymers when compared with ex situ routes. The ‘inverse vulcanization’ sulfur polymer described herein contains a hybrid linker system which demonstrates high solubility in organic solvents, allowing solution processing of the sulfur-based polymer, ideal for the formation of thin films. The process of nanocrystal synthesis within sulfur films was optimized by observing nanocrystal formation by X-ray photoelectron spectroscopy and X-ray diffraction. Examination of the film morphology by scanning electron microscopy showed that beyond a certain precursor concentration the nanocrystals formed were not only within the film but also on the surface suggesting a loading limit within the polymer. We envisage this material could be used as the basis of a new generation of materials where solution processed sulfur polymers act as an alternative to traditional polymers. PMID:28878986

Formulation and Characterization of Solid Dispersion Prepared by Hot Melt Mixing: A Fast Screening Approach for Polymer Selection

PubMed Central

Enose, Arno A.; Dasan, Priya K.; Sivaramakrishnan, H.; Shah, Sanket M.

2014-01-01

Solid dispersion is molecular dispersion of drug in a polymer matrix which leads to improved solubility and hence better bioavailability. Solvent evaporation technique was employed to prepare films of different combinations of polymers, plasticizer, and a modal drug sulindac to narrow down on a few polymer-plasticizer-sulindac combinations. The sulindac-polymer-plasticizer combination that was stable with good film forming properties was processed by hot melt mixing, a technique close to hot melt extrusion, to predict its behavior in a hot melt extrusion process. Hot melt mixing is not a substitute to hot melt extrusion but is an aid in predicting the formation of molecularly dispersed form of a given set of drug-polymer-plasticizer combination in a hot melt extrusion process. The formulations were characterized by advanced techniques like optical microscopy, differential scanning calorimetry, hot stage microscopy, dynamic vapor sorption, and X-ray diffraction. Subsequently, the best drug-polymer-plasticizer combination obtained by hot melt mixing was subjected to hot melt extrusion process to validate the usefulness of hot melt mixing as a predictive tool in hot melt extrusion process. PMID:26556187

Thermomechanical Properties, Antibiotic Release, and Bioactivity of a Sterilized Cyclodextrin Drug Delivery System

PubMed Central

Halpern, Jeffrey M.; Gormley, Catherine A.; Keech, Melissa; von Recum, Horst A.

2014-01-01

Various local drug delivery devices and coatings are being developed as slow, sustained release mechanism for drugs, yet the polymers are typically not evaluated after commercial sterilization techniques. We examine the effect that commercial sterilization techniques have on the physical, mechanical, and drug delivery properties of polyurethane polymers. Specifically we tested cyclodextrin-hexamethyl diisocyanate crosslinked polymers before and after autoclave, ethylene oxide, and gamma radiation sterilization processes. We found that there is no significant change in the properties of polymers sterilized by ethylene oxide and gamma radiation compared to non-sterilized polymers. Polymers sterilized by autoclave showed increased tensile strength (p<0.0001) compared to non-sterilized polymers . In the release of drugs, which were loaded after the autoclave sterilization process, we observed a prolonged release (p<0.05) and a prolonged therapeutic effect (p<0.05) but less drug loading (p<0.0001) compared to non-sterilized polymers. The change in the release profile and tensile strength in polymers sterilized by autoclave was interpreted as being caused by additional crosslinking from residual, unreacted, or partially-reacted crosslinker contained within the polymer. Autoclaving therefore represents additional thermo-processing to modify rate and dose from polyurethanes and other materials. PMID:24949201

A novel polymer extrusion micropelletization process

NASA Astrophysics Data System (ADS)

Aquite, William

Polymer micropellets provide a variety of potential applications for different processes in the polymer industry. Conventional pellets are in the size range of 2.5 mm to 5 mm, while micropellets are at least ten times smaller, in the size range of 50 μm to 1000 μm. The potential benefits to a processor using micropellets include: high surface to volume ratio, high bulk density, fast and even melting rates in extrusion, improved dry flow properties, faster injection molding cycles, and consequently lower energy consumption during processing. More specialized sintering processes that require polymer powders, such as selective sintering techniques, microporous plastics parts manufacturing, and other powder sintering methods would benefit from the production of polymer micropellets since these exhibit the advantages of pellets yet have a lower average size. This work focuses on the study of a technique developed at the Polymer Engineering Center. The technique uses a microcapillary die for the production of micropellets by causing instabilities in extruded polymer threads deformed using an air stream. Tuning of process conditions allow the development of surface disturbances that promote breakup of the threads into pellets, which are subsequently cooled and collected. Although micropellets with high sphericity and a narrow size distribution can be produced using this technique, minimal changes in process conditions also lead to the production of lenticular pellets as well as pellets, fibers and threads with a wide range of size and shape distributions. This work shows how changing processing conditions achieve a variety of shapes and sizes of micropellets, broadening its application for the production of powders from a variety of polymer resins. Different approaches were used, including dimensional analysis and numerical simulation of the micropelletization process. This research reveals the influence of non-linear viscoelastic effects on the dispersion of a polymer thread through surface disturbances. Furthermore, this research reveals how processing parameters can influence the quality of the produced micropellet. Through this work, an economically feasible technique was developed that can produce the raw material for processors that depend on polymer powders that will deliver ideally shaped and distributed micropellets.

Thermal and chemical stabilization of ethylene/vinyl acetate/vinyl alcohol (EVA-OH) terpolymers under nitroplasticizer environments

DOE PAGES

Yang, Dali; Hubbard, Kevin M.; Henderson, Kevin C.; ...

2014-09-17

Here, we compare the aging behaviors of cross-linked ethylene/vinyl acetate/vinyl alcohol terpolymers, also referred to as EVA-OH, when they are either immersed in nitroplasticizer (NP) liquid or exposed to NP vapor at different temperatures. And while thermogravimetric analysis and differential scanning calorimetry are used to probe the thermal stability of aged NP and polymers, Fourier transform infrared, gel permeation chromatography, ultra-violet/vis, and nuclear magnetic resonance are used to probe their structural changes over the aging process. Our study confirms that NP degrades through C[BOND]N cleavage, and releases HONO molecules at a slightly elevated temperature (<75°C). As these molecules accumulate inmore » the vapor phase, they react among themselves to create an acidic environment. Therefore, these chemical constituents in the NP vapor significantly accelerate the hydrolysis of EVA-OH polymer. When the hydrolysis occurs in both vinyl acetate and urethane groups and the scission at the cross-linker progresses, EVA-OH becomes vulnerable to further degradation in the NP vapor environment. Finally, through the comprehensive characterization, the possible degradation mechanisms of the terpolymers are proposed.« less

Effect of molecular weight on polymer processability

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

Karg, R.F.

1983-01-01

Differences in rheological behavior due to the polymer molecular weight and molecular weight distribution have been shown with the MPT. SBR polymers having high molecular weight fractions develop higher stress relaxation time values due to the higher degree of polymer entanglements. Tests conducted at increasing temperatures show the diminishing influence of the polymer entanglements upon stress relaxation time. EPDM polymers show stress relaxation time and head pressure behavior which correlates with mill processability. As anticipated, compounded stock of EPDM have broad molecular weight distribution has higher stress relaxation time values than EPDM compounds with narrow molecular weight distribution.

Continuous process to produce lithium-polymer batteries

DOEpatents

Chern, Terry Song-Hsing; Keller, David Gerard; MacFadden, Kenneth Orville

1998-01-01

Solid polymer electrolytes are extruded with active electrode material in a continuous, one-step process to form composite electrolyte-electrodes ready for assembly into battery cells. The composite electrolyte-electrode sheets are extruded onto current collectors to form electrodes. The composite electrodes, as extruded, are electronically and ionically conductive. The composite electrodes can be overcoated with a solid polymer electrolyte, which acts as a separator upon battery assembly. The interface between the solid polymer electrolyte composite electrodes and the solid polymer electrolyte separator has low resistance.

Photo-degradation of high efficiency fullerene-free polymer solar cells.

PubMed

Upama, Mushfika Baishakhi; Wright, Matthew; Mahmud, Md Arafat; Elumalai, Naveen Kumar; Mahboubi Soufiani, Arman; Wang, Dian; Xu, Cheng; Uddin, Ashraf

2017-12-07

Polymer solar cells are a promising technology for the commercialization of low cost, large scale organic solar cells. With the evolution of high efficiency (>13%) non-fullerene polymer solar cells, the stability of the cells has become a crucial parameter to be considered. Among the several degradation mechanisms of polymer solar cells, burn-in photo-degradation is relatively less studied. Herein, we present the first systematic study of photo-degradation of novel PBDB-T:ITIC fullerene-free polymer solar cells. The thermally treated and as-prepared PBDB-T:ITIC solar cells were exposed to continuous 1 sun illumination for 5 hours. The aged devices exhibited rapid losses in the short-circuit current density and fill factor. The severe short-circuit current and fill factor burn in losses were attributed to trap mediated charge recombination, as evidenced by an increase in Urbach energy for aged devices.

75 FR 77624 - Intent To Grant an Exclusive License for U.S. Army Owned Inventions to Polymer Processing Institute

Federal Register 2010, 2011, 2012, 2013, 2014

2010-12-13

... DEPARTMENT OF DEFENSE Department of the Army Intent To Grant an Exclusive License for U.S. Army Owned Inventions to Polymer Processing Institute AGENCY: Department of the Army, DoD. ACTION: Notice... contemplates granting an exclusive license to Polymer Processing Institute, a not-for-profit corporation having...

Polymer based tunneling sensor

NASA Technical Reports Server (NTRS)

Wang, Jing (Inventor); Zhao, Yongjun (Inventor); Cui, Tianhong (Inventor)

2006-01-01

A process for fabricating a polymer based circuit by the following steps. A mold of a design is formed through a lithography process. The design is transferred to a polymer substrate through a hot embossing process. A metal layer is then deposited over at least part of said design and at least one electrical lead is connected to said metal layer.

Fabrication process for polymer PLC platforms with V-grooves for passive alignment

NASA Astrophysics Data System (ADS)

Park, Suntak; Lee, Jong-Moo; Ahn, Joon Tae; Baek, Yong-Soon

2005-12-01

A method for polymer planar lightwave circuit (PLC) devices fabricated on a substrate with V-grooves is developed for passive alignment of an optical fiber to a polymer waveguide. In order to minimize thickness nonuniformity of polymer layers caused by the V-grooves, dry film resist (DFR) is used. The V-grooves are covered with the DFR before the polymer layers are spin-coated on the substrate. The DFR prevents the polymer from being filled in the V-grooves as well as from being spin-coated nonuniformly on the substrate. This process provides a simple and cost-effective fabrication method of polymer PLCs or platforms for passive alignment.

Nanoscale Mobility of Aqueous Polyacrylic Acid in Dental Restorative Cements.

PubMed

Berg, Marcella C; Benetti, Ana R; Telling, Mark T F; Seydel, Tilo; Yu, Dehong; Daemen, Luke L; Bordallo, Heloisa N

2018-03-28

Hydrogen dynamics in a time range from hundreds of femtoseconds to nanoseconds can be directly analyzed using neutron spectroscopy, where information on the inelastic and quasi-elastic scattering, hereafter INS and QENS, can be obtained. In this study, we applied these techniques to understand how the nanoscale mobility of the aqueous solution of polyacrylic acid (PAA) used in conventional glass ionomer cements (GICs) changes under confinement. Combining the spectroscopic analysis with calorimetric results, we were able to separate distinct motions within both the liquid and the GICs. The QENS analysis revealed that the self-diffusion translational motion identified in the liquid is also visible in the GIC. However, as a result of the formation of the cement matrix and its setting, both translational diffusion and residence time differed from the PAA solution. When comparing the local diffusion obtained for the selected GIC, the only noticeable difference was observed for the slow dynamics associated with the polymer chain. Additionally, over short-term aging, progressive water binding to the polymer chain occurred in one of the investigated GICs. Finally, a considerable change in the density of the GIC without progressive water binding indicates an increased polymer cross-linking. Taken together, our results suggest that accurate and deep understanding of polymer-water binding, polymer cross-linking, as well as material density changes occurring during the maturation process of GIC are necessary for the development of advanced dental restorative materials.

Preparation of prepreg graphite tape with insoluble polymer

NASA Technical Reports Server (NTRS)

Yates, C. I.

1973-01-01

Powdered polymer is finely ground. Second polymer, soluble, is mixed with appropriate solvent. Milled polymer and graphite filaments are added to soluble polymer-solvent solution to create slurry. Slurry is dried, and when ready for processing, the soluble, binder-polymer is removed by heat during precure or cure cycle.

Radiation processing of natural polymers: The IAEA contribution

NASA Astrophysics Data System (ADS)

Haji-Saeid, Mohammad; Safrany, Agnes; Sampa, Maria Helena de O.; Ramamoorthy, Natesan

2010-03-01

Radiation processing offers a clean and additive-free method for preparation of value-added novel materials based on renewable, non-toxic, and biodegradable natural polymers. Crosslinked natural polymers can be used as hydrogel wound dressings, face cleaning cosmetic masks, adsorbents of toxins, and non-bedsore mats; while low molecular weight products show antibiotic, antioxidant, and plant-growth promoting properties. Recognizing the potential benefits that radiation technology can offer for processing of natural polymers into useful products, the IAEA implemented a coordinated research project (CRP) on "Development of Radiation-processed products of Natural Polymers for application in Agriculture, Healthcare, Industry and Environment". This CRP was launched at the end of 2007 with participation of 16 MS to help connecting radiation technology and end-users to derive enhanced benefits from these new value-added products of radiation-processed natural materials. In this paper the results of activities in participating MS related to this work will be presented.

Manufacturing polymer light emitting diode with high luminance efficiency by solution process

NASA Astrophysics Data System (ADS)

Kim, Miyoung; Jo, SongJin; Yang, Ho Chang; Yoon, Dang Mo; Kwon, Jae-Taek; Lee, Seung-Hyun; Choi, Ju Hwan; Lee, Bum-Joo; Shin, Jin-Koog

2012-06-01

While investigating polymer light emitting diodes (polymer-LEDs) fabricated by solution process, surface roughness influences electro-optical (E-O) characteristics. We expect that E-O characteristics such as luminance and power efficiency related to surface roughness and layer thickness of emitting layer with poly-9-Vinylcarbazole. In this study, we fabricated polymer organic light emitting diodes by solution process which guarantees easy, eco-friendly and low cost manufacturing for flexible display applications. In order to obtain high luminescence efficiency, E-O characteristics of these devices by varying parameters for printing process have been investigated. Therefore, we optimized process condition for polymer-LEDs by adjusting annealing temperatures of emission, thickness of emission layer showing efficiency (10.8 cd/A) at 10 mA/cm2. We also checked wavelength dependent electroluminescence spectrum in order to find the correlation between the variation of efficiency and the thickness of the layer.

Ion track etching revisited: II. Electronic properties of aged tracks in polymers

NASA Astrophysics Data System (ADS)

Fink, D.; Muñoz Hernández, G.; Cruz, S. A.; Garcia-Arellano, H.; Vacik, J.; Hnatowicz, V.; Kiv, A.; Alfonta, L.

2018-02-01

We compile here electronic ion track etching effects, such as capacitive-type currents, current spike emission, phase shift, rectification and background currents that eventually emerge upon application of sinusoidal alternating voltages across thin, aged swift heavy ion-irradiated polymer foils during etching. Both capacitive-type currents and current spike emission occur as long as obstacles still prevent a smooth continuous charge carrier passage across the foils. In the case of sufficiently high applied electric fields, these obstacles are overcome by spike emission. These effects vanish upon etchant breakthrough. Subsequent transmitted currents are usually of Ohmic type, but shortly after breakthrough (during the track' core etching) often still exhibit deviations such as strong positive phase shifts. They stem from very slow charge carrier mobility across the etched ion tracks due to retarding trapping/detrapping processes. Upon etching the track's penumbra, one occasionally observes a split-up into two transmitted current components, one with positive and another one with negative phase shifts. Usually, these phase shifts vanish when bulk etching starts. Current rectification upon track etching is a very frequent phenomenon. Rectification uses to inverse when core etching ends and penumbra etching begins. When the latter ends, rectification largely vanishes. Occasionally, some residual rectification remains which we attribute to the aged polymeric bulk itself. Last not least, we still consider background currents which often emerge transiently during track etching. We could assign them clearly to differences in the electrochemical potential of the liquids on both sides of the etched polymer foils. Transient relaxation effects during the track etching cause their eventually chaotic behaviour.

Polymer deformation and filling modes during microembossing

NASA Astrophysics Data System (ADS)

Rowland, Harry D.; King, William P.

2004-12-01

This work investigates the initial stages of polymer deformation during hot embossing micro-manufacturing at processing temperatures near the glass transition temperature (Tg) of polymer films having sufficient thickness such that polymer flow is not supply limited. Several stages of polymer flow can be observed by employing stamp geometries of various widths and varying imprint conditions of time and temperature to modulate polymer viscosity. Experiments investigate conditions affecting cavity filling phenomena, including apparent polymer viscosity. Stamps with periodic ridges of height and width 4 µm and periodicity 30, 50 and 100 µm emboss trenches into polymethyl methacrylate films at Tg - 10 °C < Temboss < Tg + 20 °C. Imprint parameters of time, temperature and load are correlated with replicated polymer shape, height and imprinted area. Polymer replicates are measured by atomic force microscopy and inspected by scanning electron microscopy. Cavity size and the temperature dependence of polymer viscosity significantly influence the nature of polymer deformation in hot embossing micro-manufacturing and must be accounted for in rational process design.

Carboxymethylcellulose adsorption on molybdenite: the effect of electrolyte composition on adsorption, bubble-surface collisions, and flotation.

PubMed

Kor, Mohammad; Korczyk, Piotr M; Addai-Mensah, Jonas; Krasowska, Marta; Beattie, David A

2014-10-14

The adsorption of carboxymethylcellulose polymers on molybdenite was studied using spectroscopic ellipsometry and atomic force microscopy imaging with two polymers of differing degrees of carboxyl group substitution and at three different electrolyte conditions: 1 × 10(-2) M KCl, 2.76 × 10(-2) M KCl, and simulated flotation process water of multicomponent electrolyte content, with an ionic strength close to 2.76 × 10(-2) M. A higher degree of carboxyl substitution in the adsorbing polymer resulted in adsorbed layers that were thinner and with more patchy coverage; increasing the ionic strength of the electrolyte resulted in increased polymer layer thickness and coverage. The use of simulated process water resulted in the largest layer thickness and coverage for both polymers. The effect of the adsorbed polymer layer on bubble-particle attachment was studied with single bubble-surface collision experiments recorded with high-speed video capture and image processing and also with single mineral molybdenite flotation tests. The carboxymethylcellulose polymer with a lower degree of substitution resulted in almost complete prevention of wetting film rupture at the molybdenite surface under all electrolyte conditions. The polymer with a higher degree of substitution prevented rupture only when adsorbed from simulated process water. Molecular kinetic theory was used to quantify the effect of the polymer on the dewetting dynamics for collisions that resulted in wetting film rupture. Flotation experiments confirmed that adsorbed polymer layer properties, through their effect on the dynamics of bubble-particle attachment, are critical to predicting the effectiveness of polymers used to prevent mineral recovery in flotation.

Consolidation & Factors Influencing Sintering Process in Polymer Powder Based Additive Manufacturing

NASA Astrophysics Data System (ADS)

Sagar, M. B.; Elangovan, K.

2017-08-01

Additive Manufacturing (AM) is two decade old technology; where parts are build layer manufacturing method directly from a CAD template. Over the years, AM techniques changes the future way of part fabrication with enhanced intricacy and custom-made features are aimed. Commercially polymers, metals, ceramic and metal-polymer composites are in practice where polymers enhanced the expectations in AM and are considered as a kind of next industrial revolution. Growing trend in polymer application motivated to study their feasibility and properties. Laser sintering, Heat sintering and Inhibition sintering are the most successful AM techniques for polymers but having least application. The presentation gives up selective sintering of powder polymers and listed commercially available polymer materials. Important significant factors for effective processing and analytical approaches to access them are discussed.

High Energy Density in Azobenzene-based Materials for Photo-Thermal Batteries via Controlled Polymer Architecture and Polymer-Solvent Interactions.

PubMed

Jeong, Seung Pyo; Renna, Lawrence A; Boyle, Connor J; Kwak, Hyunwook S; Harder, Edward; Damm, Wolfgang; Venkataraman, Dhandapani

2017-12-19

Energy densities of ~510 J/g (max: 698 J/g) have been achieved in azobenzene-based syndiotactic-rich poly(methacrylate) polymers. The processing solvent and polymer-solvent interactions are important to achieve morphologically optimal structures for high-energy density materials. This work shows that morphological changes of solid-state syndiotactic polymers, driven by different solvent processings play an important role in controlling the activation energy of Z-E isomerization as well as the shape of the DSC exotherm. Thus, this study shows the crucial role of processing solvents and thin film structure in achieving higher energy densities.

Process for the displacement of cyanide ions from metal-cyanide complexes

DOEpatents

Smith, Barbara F.; Robinson, Thomas W.

1997-01-01

The present invention relates to water-soluble polymers and the use of such water-soluble polymers in a process for the displacement of the cyanide ions from the metal ions within metal-cyanide complexes. The process waste streams can include metal-cyanide containing electroplating waste streams, mining leach waste streams, mineral processing waste streams, and related metal-cyanide containing waste streams. The metal ions of interest are metals that give very strong complexes with cyanide, mostly iron, nickel, and copper. The physical separation of the water-soluble polymer-metal complex from the cyanide ions can be accomplished through the use of ultrafiltration. Once the metal-cyanide complex is disrupted, the freed cyanide ions can be recovered for reuse or destroyed using available oxidative processes rendering the cyanide nonhazardous. The metal ions are released from the polymer, using dilute acid, metal ion oxidation state adjustment, or competing chelating agents, and collected and recovered or disposed of by appropriate waste management techniques. The water-soluble polymer can then be recycled. Preferred water-soluble polymers include polyethyleneimine and polyethyleneimine having a catechol or hydroxamate group.

Kinetics and capacities of phosphorus sorption to tertiary stage wastewater alum solids, and process implications for achieving low-level phosphorus effluents.

PubMed

Maher, Chris; Neethling, J B; Murthy, Sudhir; Pagilla, Krishna

2015-11-15

The role of adsorption and/or complexation in removal of reactive or unreactive effluent phosphorus by already formed chemical precipitates or complexes has been investigated. Potential operational efficiency gains resulting from age of chemically precipitated tertiary alum sludge and the recycle of sludge to the process stream was undertaken at the Iowa Hill Water Reclamation Facility which employs the DensaDeg(®) process (IDI, Richmond, VA) for tertiary chemical P removal to achieve a filtered final effluent total phosphorus concentration of <30 μg/L. The effect of sludge solids age was found to be insignificant over the solids retention time (SRT) of 2-8 days, indicating that the solids were unaffected by the aging effects of decreasing porosity and surface acidity. The bulk of solids inventory was retained in the clarifier blanket, providing no advantage in P removal from increased solids inventory at higher SRTs. When solids recycle was redirected from the traditional location of the flocculation reactor to a point just prior to chemical addition in the chemical mixing reactor, lower effluent soluble P concentrations at lower molar doses of aluminum were achieved. At laboratory scale, the "spent" or "waste" chemical alum sludge from P removal showed high capacity and rapid kinetics for P sorption from real wastewater effluents. Saturation concentrations were in the range of 8-29 mg soluble reactive P/g solids. Higher saturation concentrations were found at higher temperatures. Alum sludge produced without a coagulant aid polymer had a much higher capacity for P sorption than polymer containing alum sludge. The adsorption reaction reached equilibrium in less than 10 min with 50% or greater removal within the first minute. Copyright © 2015 Elsevier Ltd. All rights reserved.

Nonequilibrium processes of segregation and diffusion in metal-polymer tribosystems

NASA Astrophysics Data System (ADS)

Sidashov, A. V.; Kolesnikov, I. V.

2017-12-01

The article presents the results of exchange-diffusion processes between chemical elements in metal-polymer tribosystems (between a metal wheel of a rolling stock and a composite polymer brake shoe). The effect of the segregation processes on the strength characteristics of the working surface of a tribosystem is estimated by quantum chemical calculations, Auger and X-ray photoelectron spectroscopies.

Ladder polymers for use as high temperature stable resins or coatings

NASA Technical Reports Server (NTRS)

Meador, Mary Ann (Inventor)

1990-01-01

An object of the invention is to synthesize a new class of ladder and partial ladder polymers. In accordance with the invention, the new class of ladder and partial ladder polymers are synthesized by polymerizing a bis-dienophile with a bis-diene. Another object of the invention is to provide a fabricated, electrically conducting, void free composite comprising the new class of the ladder and partial ladder polymers described above. The novelty of the invention relates to a new class of ladder and partial ladder polymers and a process for synthesizing these polymers. These polymers are soluble in common organic solvents and are characterized with a unique dehydration property at temperatures of 300 to 400 C to provide thermo-oxidatively stable pentiptycene units along the polymeric backbone. These polymers are further characterized with high softening points and good thermo-oxidative stability properties. Thus these polymers have potential as processable, matrix resins for high temperature composite applications.

Radiochemical ageing of EPDM elastomers. 3. Mechanism of radiooxidation

NASA Astrophysics Data System (ADS)

Rivaton, A.; Cambon, S.; Gardette, J.-L.

2005-01-01

The preceding paper of this series was devoted to the identification and quantification of the main chemical changes resulting from the radiochemical ageing of EPDM (77.9% ethylene, 21.4% propylene, 0.7% diene) and EPR (76.6% ethylene, 23.4% propylene) films irradiated under oxygen atmosphere using 60Co gamma rays. The double bond of the diene was observed to be consumed with a high radiochemical yield. The oxidation and reticulation rates were observed to be higher in the case of EPDM than in EPR. Accumulation of the major oxidation products in both polymers was shown to occur in the order of decreasing concentrations: hydroperoxides, ketones, carboxylic acids and alcohols, peroxides. On the basis of the analysis of the oxidation products formed in EPDM and EPR, and taking into account their relative concentrations, the mechanisms accounting for the EPDM γ-degradation under oxygen atmosphere are proposed in the present paper. Two main processes are involved in the EPDM radiooxidation. The random γ-radiolysis of the polymer provides a constant source of macroalkyl radicals mainly formed on ethylene units. The secondary radicals so formed are likely to initiate a selective oxidation of the polymer through free-radicals reactions involving the abstraction of labile hydrogen atoms. In particular, the hydroperoxides decomposition and the consumption of the ENB moieties, this latter being the most oxidisable site and the source of crosslinking, may result from hydrogen abstraction by radical species.

Removal of waterborne microorganisms by filtration using clay-polymer complexes.

PubMed

Undabeytia, Tomas; Posada, Rosa; Nir, Shlomo; Galindo, Irene; Laiz, Leonila; Saiz-Jimenez, Cesareo; Morillo, Esmeralda

2014-08-30

Clay-polymer composites were designed for use in filtration processes for disinfection during the course of water purification. The composites were formed by sorption of polymers based on starch modified with quaternary ammonium ethers onto the negatively charged clay mineral bentonite. The performance of the clay-polymer complexes in removal of bacteria was strongly dependent on the conformation adopted by the polycation on the clay surface, the charge density of the polycation itself and the ratio between the concentrations of clay and polymer used during the sorption process. The antimicrobial effect exerted by the clay-polymer system was due to the cationic monomers adsorbed on the clay surface, which resulted in a positive surface potential of the complexes and charge reversal. Clay-polymer complexes were more toxic to bacteria than the polymers alone. Filtration employing our optimal clay-polymer composite yielded 100% removal of bacteria after the passage of 3L, whereas an equivalent filter with granular activated carbon (GAC) hardly yielded removal of bacteria after 0.5L. Regeneration of clay-polymer complexes saturated with bacteria was demonstrated. Modeling of the filtration processes permitted to optimize the design of filters and estimation of experimental conditions for purifying large water volumes in short periods. Copyright © 2014 Elsevier B.V. All rights reserved.

Processes for preparing carbon fibers using gaseous sulfur trioxide

DOEpatents

Barton, Bryan E.; Lysenko, Zenon; Bernius, Mark T.; Hukkanen, Eric J.

2016-01-05

Disclosed herein are processes for preparing carbonized polymers, such as carbon fibers, comprising: sulfonating a polymer with a sulfonating agent that comprises SO.sub.3 gas to form a sulfonated polymer; treating the sulfonated polymer with a heated solvent, wherein the temperature of said solvent is at least 95.degree. C.; and carbonizing the resulting product by heating it to a temperature of 500-3000.degree. C.

Highly Efficient Flexible Hybrid Photovoltaic Cells Based on Low-Band-Gap Conjugated Polymers Sensitized by Nanoparticle-Grafted Carbon

DTIC Science & Technology

2010-09-01

modeling, synthesis , and characterization of several series functional and processable electro-active conjugated polymers with evolving frontier...tasks as a basic obligation of this award: Task #1. Low Band Gap Polymers The awardee (Professor Sun’s group at NSU) shall design, synthesis , and...design, modeling, synthesis , and characterizations of several series functional and processable electro-active conjugated polymers with evolving

Planar-Processed Polymer Transistors.

PubMed

Xu, Yong; Sun, Huabin; Shin, Eul-Yong; Lin, Yen-Fu; Li, Wenwu; Noh, Yong-Young

2016-10-01

Planar-processed polymer transistors are proposed where the effective charge injection and the split unipolar charge transport are all on the top surface of the polymer film, showing ideal device characteristics with unparalleled performance. This technique provides a great solution to the problem of fabrication limitations, the ambiguous operating principle, and the performance improvements in practical applications of conjugated-polymer transistors. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tough, High-Performance, Thermoplastic Addition Polymers

NASA Technical Reports Server (NTRS)

Pater, Ruth H.; Proctor, K. Mason; Gleason, John; Morgan, Cassandra; Partos, Richard

1991-01-01

Series of addition-type thermoplastics (ATT's) exhibit useful properties. Because of their addition curing and linear structure, ATT polymers have toughness, like thermoplastics, and easily processed, like thermosets. Work undertaken to develop chemical reaction forming stable aromatic rings in backbone of ATT polymer, combining high-temperature performance and thermo-oxidative stability with toughness and easy processibility, and minimizing or eliminating necessity for tradeoffs among properties often observed in conventional polymer syntheses.

Enhancing performing characteristics of organic semiconducting films by improved solution processing

DOEpatents

Bazan, Guillermo C; Moses, Daniel; Peet, Jeffrey; Heeger, Alan J

2014-05-13

Improved processing methods for enhanced properties of conjugated polymer films are disclosed, as well as the enhanced conjugated polymer films produced thereby. Addition of low molecular weight alkyl-containing molecules to solutions used to form conjugated polymer films leads to improved photoconductivity and improvements in other electronic properties. The enhanced conjugated polymer films can be used in a variety of electronic devices, such as solar cells and photodiodes.

Progress report

NASA Technical Reports Server (NTRS)

Abhiraman, A.; Collard, D.; Cardelino, B.; Bhatia, S.; Desai, P.; Harruna, I.; Khan, I.; Mariam, Y.; Mensah, T.; Mitchell, M.

1992-01-01

The NASA funding allowed Clark Atlanta University (CAU) to establish a High Performance Polymers And Ceramics (HiPPAC) Research Center. The HiPPAC Center is consolidating and expanding the existing polymer and ceramic research capabilities at CAU through the development of interdepartmental and interinstitutional research in: (1) polymer synthesis; (2) polymer characterization and properties; (3) polymer processing; (4) polymer-based ceramic synthesis; and (5) ceramic characterization and properties. This Center has developed strong interactions between scientists and materials scientists of CAU and their counterparts from sister institutions in the Atlanta University Center (AUC) and the Georgia Institute of Technology. As a component of the center, we have started to develop strong collaborations with scientists from other universities and the HBCU's, national and federal agency laboratories, and the private sector during this first year. During this first year we have refined the focus of the research in the HiPPAC Center to three areas with seven working groups that will start programmatic activities on January 1, 1993, as follows: (1) nonlinear optical properties of chitosan derivatives; (2) polymeric electronic materials; (3) nondestructive characterization and prediction of polyimide performance; (4) solution processing of high-performance materials; (5) processable polyimides for composite applications; (6) sol-gel based ceramic materials processing; and (7) synthetic based processing of pre-ceramic polymers.

Continuous process to produce lithium-polymer batteries

DOEpatents

Chern, T.S.H.; Keller, D.G.; MacFadden, K.O.

1998-05-12

Solid polymer electrolytes are extruded with active electrode material in a continuous, one-step process to form composite electrolyte-electrodes ready for assembly into battery cells. The composite electrolyte electrode sheets are extruded onto current collectors to form electrodes. The composite electrodes, as extruded, are electronically and ionically conductive. The composite electrodes can be over coated with a solid polymer electrolyte, which acts as a separator upon battery assembly. The interface between the solid polymer electrolyte composite electrodes and the solid polymer electrolyte separator has low resistance. 1 fig.

Precipitation of lamellar gold nanocrystals in molten polymers

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

Palomba, M.; Carotenuto, G., E-mail: giancaro@unina.it

Non-aggregated lamellar gold crystals with regular shape (triangles, squares, pentagons, etc.) have been produced by thermal decomposition of gold chloride (AuCl) molecules in molten amorphous polymers (polystyrene and poly(methyl methacrylate)). Such covalent inorganic gold salt is high soluble into non-polar polymers and it thermally decomposes at temperatures compatible with the polymer thermal stability, producing gold atoms and chlorine radicals. At the end of the gold precipitation process, the polymer matrix resulted chemically modified because of the partial cross-linking process due to the gold atom formation reaction.

A Dry Powder Process for Preparing Uni-Tape Prepreg from Polymer Powder Coated Filamentary Towpregs

NASA Technical Reports Server (NTRS)

Wilkinson, Steven P. (Inventor); Johnston, Norman J. (Inventor); Marchello, Joseph M. (Inventor)

1995-01-01

A process for preparing uni-tape prepreg from polymer powder coated filamentary towpregs is provided. A plurality of polymer powder coated filamentary towpregs are provided. The towpregs are collimated so that each towpreg is parallel. The sandwich is heated to a temperature wherein the polymer flows and intimately contacts the filaments and pressure is repeatedly applied perpendicularly to the sandwich with a longitudinal oscillating action wherein the filaments move apart and the polymer wets the filaments forming a uni-tape prepreg. The uni-tape prepreg is subsequently cooled.

Control of pore size and structure of tissue engineering scaffolds produced by supercritical fluid processing.

PubMed

Tai, Hongyun; Mather, Melissa L; Howard, Daniel; Wang, Wenxin; White, Lisa J; Crowe, John A; Morgan, Steve P; Chandra, Amit; Williams, David J; Howdle, Steven M; Shakesheff, Kevin M

2007-12-17

Tissue engineering scaffolds require a controlled pore size and structure to host tissue formation. Supercritical carbon dioxide (scCO2) processing may be used to form foamed scaffolds in which the escape of CO2 from a plasticized polymer melt generates gas bubbles that shape the developing pores. The process of forming these scaffolds involves a simultaneous change in phase in the CO2 and the polymer, resulting in rapid expansion of a surface area and changes in polymer rheological properties. Hence, the process is difficult to control with respect to the desired final pore size and structure. In this paper, we describe a detailed study of the effect of polymer chemical composition, molecular weight and processing parameters on final scaffold characteristics. The study focuses on poly(DL-lactic acid) (PDLLA) and poly(DL-lactic acid-co-glycolic acid) (PLGA) as polymer classes with potential application as controlled release scaffolds for growth factor delivery. Processing parameters under investigation were temperature (from 5 to 55 degrees C) and pressure (from 60 to 230 bar). A series of amorphous PDLLA and PLGA polymers with various molecular weights (from 13 KD to 96 KD) and/or chemical compositions (the mole percentage of glycolic acid in the polymers was 0, 15, 25, 35 and 50 respectively) were employed. The resulting scaffolds were characterised by optical microscopy, scanning electron microscopy (SEM), and micro X-ray computed tomography (microCT). This is the first detailed study on using these series polymers for scaffold formation by supercritical technique. This study has demonstrated that the pore size and structure of the supercritical PDLLA and PLGA scaffolds can be tailored by careful control of processing conditions.

Semiconducting polymers with nanocrystallites interconnected via boron-doped carbon nanotubes.

PubMed

Yu, Kilho; Lee, Ju Min; Kim, Junghwan; Kim, Geunjin; Kang, Hongkyu; Park, Byoungwook; Ho Kahng, Yung; Kwon, Sooncheol; Lee, Sangchul; Lee, Byoung Hun; Kim, Jehan; Park, Hyung Il; Kim, Sang Ouk; Lee, Kwanghee

2014-12-10

Organic semiconductors are key building blocks for future electronic devices that require unprecedented properties of low-weight, flexibility, and portability. However, the low charge-carrier mobility and undesirable processing conditions limit their compatibility with low-cost, flexible, and printable electronics. Here, we present significantly enhanced field-effect mobility (μ(FET)) in semiconducting polymers mixed with boron-doped carbon nanotubes (B-CNTs). In contrast to undoped CNTs, which tend to form undesired aggregates, the B-CNTs exhibit an excellent dispersion in conjugated polymer matrices and improve the charge transport between polymer chains. Consequently, the B-CNT-mixed semiconducting polymers enable the fabrication of high-performance FETs on plastic substrates via a solution process; the μFET of the resulting FETs reaches 7.2 cm(2) V(-1) s(-1), which is the highest value reported for a flexible FET based on a semiconducting polymer. Our approach is applicable to various semiconducting polymers without any additional undesirable processing treatments, indicating its versatility, universality, and potential for high-performance printable electronics.

A thermo-chemo-mechanically coupled constitutive model for curing of glassy polymers

NASA Astrophysics Data System (ADS)

Sain, Trisha; Loeffel, Kaspar; Chester, Shawn

2018-07-01

Curing of a polymer is the process through which a polymer liquid transitions into a solid polymer, capable of bearing mechanical loads. The curing process is a coupled thermo-chemo-mechanical conversion process which requires a thorough understanding of the system behavior to predict the cure dependent mechanical behavior of the solid polymer. In this paper, a thermodynamically consistent, frame indifferent, thermo-chemo-mechanically coupled continuum level constitutive framework is proposed for thermally cured glassy polymers. The constitutive framework considers the thermodynamics of chemical reactions, as well as the material behavior for a glassy polymer. A stress-free intermediate configuration is introduced within a finite deformation setting to capture the formation of the network in a stress-free configuration. This work considers a definition for the degree of cure based on the chemistry of the curing reactions. A simplified version of the proposed model has been numerically implemented, and simulations are used to understand the capabilities of the model and framework.

Morphology evolution in high-performance polymer solar cells processed from nonhalogenated solvent

DOE PAGES

Cai, Wanzhu; Liu, Peng; Jin, Yaocheng; ...

2015-05-26

A new processing protocol based on non-halogenated solvent and additive is developed to produce polymer solar cells with power conversion efficiencies better than those processed from commonly used halogenated solvent-additive pair. Morphology studies show that good performance correlates with a finely distributed nanomorphology with a well-defined polymer fibril network structure, which leads to balanced charge transport in device operation.

International Conference on Electronic Processes in Organic Materials (6th) Held in Gurzuf, Crimea, Ukraine, on September 25-29, 2006

DTIC Science & Technology

2006-09-29

MEH-PPV and blends MEH-PPV/fullerene derivative to investigate the charge transfer process . Microstructure - properties correlation of blends polymer...liquid crystals 4. Nonlinear properties of organic structures and composites 5. Electronic processes within polymer composites 6. Nanostructures. Polymer...P.A.Kondratenko, Yu.M.Lopatkin, TN.Sakun. SPECTROSCOPIC PROPERTIES AND PROCESSES OF PHOTODISSOCIATION OF DYES ....... 32 D.-Q. Feng, D. Wisbey, Y. Ta4 Ya. B

Optimization of mechanical performance of oxidative nano-particle electrode nitrile butadiene rubber conducting polymer actuator.

PubMed

Kim, Baek-Chul; Park, S J; Cho, M S; Lee, Y; Nam, J D; Choi, H R; Koo, J C

2009-12-01

Present work delivers a systematical evaluation of actuation efficiency of a nano-particle electrode conducting polymer actuator fabricated based on Nitrile Butadiene Rubber (NBR). Attempts are made for maximizing mechanical functionality of the nano-particle electrode conducting polymer actuator that can be driven in the air. As the conducting polymer polypyrrole of the actuator is to be fabricated through a chemical oxidation polymerization process that may impose certain limitations on both electrical and mechanical functionality of the actuator, a coordinated study for optimization process of the actuator is necessary for maximizing its performance. In this article actuation behaviors of the nano-particle electrode polypyrrole conducting polymer is studied and an optimization process for the mechanical performance maximization is performed.

Diode laser welding of polypropylene: investigations of the microstructures in the welded seam

NASA Astrophysics Data System (ADS)

Abed, S.; Laurens, Patricia; Carretero, C.; Deschamps, J. R.; Duval, C.

2003-03-01

Laser welding of thermoplastic polymers is a non-contact process especially efficient for joining thermoplastic polymers. This innovative technology is already used for industrial series production in different sectors (automobile, packaging,...). The majority of the basic research concerns the weld strength depending on polymer nature, optical properties, butt design and process parameters. Nevertheless, a lack of knowledge concerning the influence of thermal history of the weld seam on morphology of semicrystalline polymer still exists, when this parameter strongly influences the strength of the weld. Actual results of diode laser transmission welding (LTW) experiments on polypropylene, a semicrystalline polymer widely used in industry, could contribute to a better understanding of the process itself and to success in practical applications.

Method of solution preparation of polyolefin class polymers for electrospinning processing included

NASA Technical Reports Server (NTRS)

Rabolt, John F. (Inventor); Givens, Steven R. (Inventor); Lee, Keun-Hyung (Inventor)

2011-01-01

A process to make a polyolefin fiber which has the following steps: mixing at least one polyolefin into a solution at room temperature or a slightly elevated temperature to form a polymer solution and electrospinning at room temperature said polymer solution to form a fiber.

The effect of accelerated aging on the wear of UHMWPE.

PubMed

Sakoda, H; Fisher, J; Lu, S; Buchanan, F

2001-01-01

Oxidative degradation of UHMWPE has been found to be a cause of elevated wear rate of the polymer in total joint replacement leading to failure of these devices. In order to evaluate long term stability of polymers, various accelerated aging methods have been developed. In this study, wear rates of shelf aged UHMWPE and "accelerated aged" UHMWPE were compared using a multi-directional pin-on-plate wear test machine in order to evaluate the effect of the accelerated aging on wear. Wear factors of the aged materials were found to depend on their density, which is a measure of oxidation level. Finally, accelerated aging was calibrated against shelf aging in terms of wear rate. Copyright 2001 Kluwer Academic Publishers

Affects of Microgravity on the Polymerization and Material Properties of Biomedical Grade Polymers

NASA Astrophysics Data System (ADS)

Crane, Deborah J.

2002-01-01

the material of choice in the production of acetabular cups for hip and tibial cradles for knee orthopeadic implant components for over 30 years. Although UHMWPE is used for more than 1.5 million implants a year in the United States alone and more than 3 million implant surgeries a year worldwide, problems with debris particle formation, pitting and fracture continue to induce premature failure of implant components. chains produced during polymerization are capable of packing into crystalline structures called lamellae, which are embedded within randomly oriented amorphous regions. Crosslinks, or tie molecules bridge the crystalline structures, which contribute to the materials' toughness and strength as a biomedical material. Research has been conducted providing evidence that a crosslinked gradient at the articulating surface of the polymer component provides resistance to surface degradation and subsequent debris formation. Recently, the introduction of highly crosslinked UHMWPE had proven to reduce some of the problems associated with the applications of this polymer as a biomedical material and was seen as the answer to solving the continuing problems associated with UHMWPE implant components. Yet current research into the fatigue characteristics of highly crosslinked UHMWPE has shown that subsurface crack propagation and subsequent delamination continues to produce problematic debris generation. Studies have shown that various sterilization and accelerated aging (to emulate natural oxidation rates) protocols adversely effects the material properties. Additional research has shown that alignment of the lamellae, caused by processing technique, fabrication or surface articulation may be the precursor to debris particle formation. Processing techniques performed under high pressure has proven to effect the width of the crystalline lamellae and therefore, the material's response to wear and fracture. UHMWP due to a microgravity environment, which could be extended to include other polymers. Polymerization as well as polymer processing in a microgravity environment may affect the length and orientation of the molecular chains, the degree of crosslinking, and distribution of amorphous to crystalline portions of the material, thus changing the ultimate properties of the polymer. Small polymer samples would be produced from the resin for testing and analysis. This research would include the effect of micro-g processing by compression molded vs. ram extruded samples for analysis. Morphological alterations in the material could be monitored using Transmission Electron Microscopy and associated properties such as toughness, density and crystallinity could be determined and compared to terra produced materials using conventional mechanical testing, density gradient columns and calorimetry techniques. If alterations are evident, fatigue testing can be performed on small specimens in order to determine the material's resistance to crack initiation and propagation. number of orthopaedic implant recipients and could be extended for use in robotics and other beneficial applications. Although polymers exhibit the greatest biocompatibility, problems with debris particle generation continue to reduce the effectiveness of UHMWPE as a biomedical material. Further polymer research in a microgravity environment may prove to produce the desired alterations in the materials' morphology and associated properties, therefore providing millions of people with superior orthopaedic implant components and lessen the occurrences of repeat surgery.

75 FR 53277 - Notice of Workshop on Polymers for Photovoltaic Systems

Federal Register 2010, 2011, 2012, 2013, 2014

2010-08-31

... photovoltaic systems; testing, performance, and reliability of polymers in photovoltaic systems; impact of... mentioned topics; presentation of a NIST- developed accelerated aging and service life prediction...

Growing perovskite into polymers for easy-processable optoelectronic devices

NASA Astrophysics Data System (ADS)

Masi, Sofia; Colella, Silvia; Listorti, Andrea; Roiati, Vittoria; Liscio, Andrea; Palermo, Vincenzo; Rizzo, Aurora; Gigli, Giuseppe

2015-01-01

Here we conceive an innovative nanocomposite to endow hybrid perovskites with the easy processability of polymers, providing a tool to control film quality and material crystallinity. We verify that the employed semiconducting polymer, poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), controls the self-assembly of CH3NH3PbI3 (MAPbI3) crystalline domains and favors the deposition of a very smooth and homogenous layer in one straightforward step. This idea offers a new paradigm for the implementation of polymer/perovskite nanocomposites towards versatile optoelectronic devices combined with the feasibility of mass production. As a proof-of-concept we propose the application of such nanocomposite in polymer solar cell architecture, demonstrating a power conversion efficiency up to 3%, to date the highest reported for MEH-PPV. On-purpose designed polymers are expected to suit the nanocomposite properties for the integration in diverse optoelectronic devices via facile processing condition.

Growing perovskite into polymers for easy-processable optoelectronic devices

PubMed Central

Masi, Sofia; Colella, Silvia; Listorti, Andrea; Roiati, Vittoria; Liscio, Andrea; Palermo, Vincenzo; Rizzo, Aurora; Gigli, Giuseppe

2015-01-01

Here we conceive an innovative nanocomposite to endow hybrid perovskites with the easy processability of polymers, providing a tool to control film quality and material crystallinity. We verify that the employed semiconducting polymer, poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), controls the self-assembly of CH3NH3PbI3 (MAPbI3) crystalline domains and favors the deposition of a very smooth and homogenous layer in one straightforward step. This idea offers a new paradigm for the implementation of polymer/perovskite nanocomposites towards versatile optoelectronic devices combined with the feasibility of mass production. As a proof-of-concept we propose the application of such nanocomposite in polymer solar cell architecture, demonstrating a power conversion efficiency up to 3%, to date the highest reported for MEH-PPV. On-purpose designed polymers are expected to suit the nanocomposite properties for the integration in diverse optoelectronic devices via facile processing condition. PMID:25579988

Visibly transparent polymer solar cells produced by solution processing.

PubMed

Chen, Chun-Chao; Dou, Letian; Zhu, Rui; Chung, Choong-Heui; Song, Tze-Bin; Zheng, Yue Bing; Hawks, Steve; Li, Gang; Weiss, Paul S; Yang, Yang

2012-08-28

Visibly transparent photovoltaic devices can open photovoltaic applications in many areas, such as building-integrated photovoltaics or integrated photovoltaic chargers for portable electronics. We demonstrate high-performance, visibly transparent polymer solar cells fabricated via solution processing. The photoactive layer of these visibly transparent polymer solar cells harvests solar energy from the near-infrared region while being less sensitive to visible photons. The top transparent electrode employs a highly transparent silver nanowire-metal oxide composite conducting film, which is coated through mild solution processes. With this combination, we have achieved 4% power-conversion efficiency for solution-processed and visibly transparent polymer solar cells. The optimized devices have a maximum transparency of 66% at 550 nm.

Water evaporation on highly viscoelastic polymer surfaces.

PubMed

Pu, Gang; Severtson, Steven J

2012-07-03

Results are reported for a study on the evaporation of water droplets from a highly viscoelastic acrylic polymer surface. These are contrasted with those collected for the same measurements carried out on polydimethylsiloxane (PDMS). For PDMS, the evaporation process involves the expected multistep process including constant drop area, constant contact angle, and finally a combination of these steps until the liquid is gone. In contrast, water evaporation from the acrylic polymer shows a constant drop area mode throughout. Furthermore, during the evaporation process, the drop area actually expands on the acrylic polymer. The single mode evaporation process is consistent with formation of wetting structures, which cannot be propagated by the capillary forces. Expansion of the drop area is attributed to the influence of the drop capillary pressure. Furthermore, the rate of drop area expansion is shown to be dependent on the thickness of the polymer film.

The Contribution of IUPAC to Polymer Science Education

ERIC Educational Resources Information Center

Chan, Chin Han; Fellows, Christopher M.; Hess, Michael; Hiorns, Roger; Hoven, Voravee P.; Russell, Gregory T.; dos Santos, Cla´udio G.; S?turcova´, Adriana; Theato, Patrick

2017-01-01

Polymer education relies on generally agreed terminology and nomenclature rules. The Polymer Division of the International Union of Pure and Applied Chemistry (IUPAC) generates and recommends such rules for naming processes and materials in polymer science. It is the goal of IUPAC that these recommendations be applied in polymer science curricula…

Gas-separation process

DOEpatents

Toy, Lora G.; Pinnau, Ingo; Baker, Richard W.

1994-01-01

A process for separating condensable organic components from gas streams. The process makes use of a membrane made from a polymer material that is glassy and that has an unusually high free volume within the polymer material.

Organization of polymer chains onto long, single-wall carbon nano-tubes: effect of tube diameter and cooling method.

PubMed

Kumar, Sunil; Pattanayek, Sudip K; Pereira, Gerald G

2014-01-14

We use molecular dynamics simulations to investigate the arrangement of polymer chains when absorbed onto a long, single-wall carbon nano-tube (SWCNT). We study the conformation and organization of the polymer chains on the SWCNT and their dependence on the tube's diameter and the rate of cooling. We use two types of cooling processes: direct quenching and gradual cooling. The radial density distribution function and bond orientational order parameter are used to characterize the polymer chain structure near the surface. In the direct cooling process, the beads of the polymer chain organize in lamella-like patterns on the surface of the SWCNT with the long axis of the lamella parallel to the axis of the SWCNT. In a stepwise, gradual cooling process, the polymer beads form a helical pattern on the surface of a relatively thick SWCNT, but form a lamella-like pattern on the surface of a very thin SWCNT. We develop a theoretical (free energy) model to explain this difference in pattern structures for the gradual cooling process and also provide a qualitative explanation for the pattern that forms from the direct cooling process.

Polymerization initated at sidewalls of carbon nanotubes

NASA Technical Reports Server (NTRS)

Tour, James M. (Inventor); Hudson, Jared L. (Inventor); Krishnamoorti, Ramanan (Inventor); Yurekli, Koray (Inventor); Mitchell, Cynthia A. (Inventor)

2011-01-01

The present invention is directed to aryl halide (such as aryl bromide) functionalized carbon nanotubes that can be utilized in anionic polymerization processes to form polymer-carbon nanotube materials with improved dispersion ability in polymer matrices. In this process the aryl halide is reacted with an alkyllithium species or is reacted with a metal to replace the aryl-bromine bond with an aryl-lithium or aryl-metal bond, respectively. It has further been discovered that other functionalized carbon nanotubes, after deprotonation with a deprotonation agent, can similarly be utilized in anionic polymerization processes to form polymer-carbon nanotube materials. Additionally or alternatively, a ring opening polymerization process can be performed. The resultant materials can be used by themselves due to their enhanced strength and reinforcement ability when compared to their unbound polymer analogs. Additionally, these materials can also be blended with pre-formed polymers to establish compatibility and enhanced dispersion of nanotubes in otherwise hard to disperse matrices resulting in significantly improved material properties. The resultant polymer-carbon nanotube materials can also be used in drug delivery processes due to their improved dispersion ability and biodegradability, and can also be used for scaffolding to promote cellular growth of tissue.

Study of Polymer Crystallization by Physical Vapor Deposition

NASA Astrophysics Data System (ADS)

Jeong, Hyuncheol

When a polymer is confined under the submicron length scale, confinement size and interfaces can significantly impact the crystallization kinetics and resulting morphology. The ability to tune the morphology of confined polymer systems is of critical importance for the development of high-performance polymer microelectronics. The wisdom from the research on confined crystallization suggests that it would be beneficial to have a processing route in which the crystallization of polymers is driven by interface and temperature effects at a nanometer-scale confinement. In practice, for atomic and small-molecular systems, physical vapor deposition (PVD) has been recognized as the most successful processing route for the precise control of the film structure at surface utilizing confinement effects. While standard PVD technologies are not generally applicable to the deposition of the chemically fragile macromolecules, the development of matrix-assisted pulsed laser evaporation (MAPLE) now enables the non-destructive PVD of high-molecular weight polymers. In this thesis work, we investigated the use of MAPLE for the precise control of the crystallization of polymer films at a molecular level. We also sought to decipher the rules governing the crystallization of confined polymers, by using MAPLE as a tool to form confined polymer systems onto substrates with a controlled temperature. We first explored the early stages of film growth and crystallization of poly(ethylene oxide) (PEO) at the substrate surface formed by MAPLE. The unique mechanism of film formation in MAPLE, the deposition of submicron-sized polymer droplets, allowed for the manifestation of confinement and substrate effects in the crystallization of MAPLE-deposited PEO. Furthermore, we also focused on the property of the amorphous PEO film formed by MAPLE, showing the dependence of polymer crystallization kinetics on the thermal history of the amorphous phase. Lastly, we probed how MAPLE processing affected the semi-crystalline structure in MAPLE-deposited polyethylene (PE) films. Depositing PE at various temperatures remarkably allowed for the tunability of the melting temperature and crystallinity of the PE films, thus manipulating the semi-crystalline structure. By comparing the structure of PE formed by different processing routes, i.e., MAPLE and melt-crystallization, we discussed how processing routes affect the development of semi-crystalline phase in polymer films.

Electric Field-Mediated Processing of Polymers. Appendix 1

NASA Technical Reports Server (NTRS)

Wnek, G. E.; Bowlin, G. L.; Haas, T. W.

2000-01-01

Significant opportunities exist for the processing of polymers (homopolymers and blends) using electric fields. We suggest that a broad range of properties can be achieved using a relatively small number of polymers, with electric fields providing the ability to tailor properties via the control of shape, morphology, and orientation. Specific attention is given to electrospinning, but we note that electroaerosol formation and field-modulated film casting represent additional processing options.

Chemical vapor deposition and characterization of polysilanes polymer based thin films and their applications in compound semiconductors and silicon devices

NASA Astrophysics Data System (ADS)

Oulachgar, El Hassane

As the semiconductors industry is moving toward nanodevices, there is growing need to develop new materials and thin films deposition processes which could enable strict control of the atomic composition and structure of thin film materials in order to achieve precise control on their electrical and optical properties. The accurate control of thin film characteristics will become increasingly important as the miniaturization of semiconductor devices continue. There is no doubt that chemical synthesis of new materials and their self assembly will play a major role in the design and fabrication of next generation semiconductor devices. The objective of this work is to investigate the chemical vapor deposition (CVD) process of thin film using a polymeric precursor as a source material. This process offers many advantages including low deposition cost, hazard free working environment, and most importantly the ability to customize the polymer source material through polymer synthesis and polymer functionalization. The combination between polymer synthesis and CVD process will enable the design of new generation of complex thin film materials with a wide range of improved chemical, mechanical, electrical and optical properties which cannot be easily achieved through conventional CVD processes based on gases and small molecule precursors. In this thesis we mainly focused on polysilanes polymers and more specifically poly(dimethylsilanes). The interest in these polymers is motivated by their distinctive electronic and photonic properties which are attributed to the delocalization of the sigma-electron along the Si-Si backbone chain. These characteristics make polysilane polymers very promising in a broad range of applications as a dielectric, a semiconductor and a conductor. The polymer-based CVD process could be eventually extended to other polymer source materials such as polygermanes, as well as and a variety of other inorganic and hybrid organic-inorganic polymers. This work has demonstrated that a polysilane polymeric source can be used to deposit a wide range of thin film materials exhibiting similar properties with conventional ceramic materials such as silicon carbide (SiC), silicon oxynitride (SiON), silicon oxycarbide (SiOC) silicon dioxide (SiO2) and silicon nitride (Si3N4). The strict control of the deposition process allows precise control of the electrical, optical and chemical properties of polymer-based thin films within a broad range. This work has also demonstrated for the first time that poly(dimethylsilmaes) polymers deposited by CVD can be used to effectively passivate both silicon and gallium arsenide MOS devices. This finding makes polymer-based thin films obtained by CVD very promising for the development of high-kappa dielectric materials for next generation high-mobility CMOS technology. Keywords. Thin films, Polymers, Vapor Phase Deposition, CVD, Nanodielectrics, Organosilanes, Polysilanes, GaAs Passivation, MOSFET, Silicon Oxynitride, Integrated Waveguide, Silicon Carbide, Compound Semiconductors.

Method for the preparation of thin-skinned asymmetric reverse osmosis membranes and products thereof

NASA Technical Reports Server (NTRS)

Wydeven, T. J. (Inventor); Katz, M. G.

1984-01-01

A method for preparing water insoluble asymmetric membranes from water soluble polymers is discussed. The process involves casting a film of the polymer, partially drying it, and then contacting it with a concentrated solution of a transition metal salt. The transition metal ions render the polymer insoluable and are believed to form a complex with it. Optionally, the polymer is crosslinked with heat or radiation. The most preferred polymer is poly(vinyl alcohol). The most preferred complexing salt is copper sulfate. The process and the metal ion linked membranes are discussed. The membranes are reverse osmosis membranes.

Nonlinear dynamics that appears in the dynamical model of drying process of a polymer solution coated on a flat substrate

NASA Astrophysics Data System (ADS)

Kagami, Hiroyuki

2007-01-01

We have proposed and modified the dynamical model of drying process of polymer solution coated on a flat substrate for flat polymer film fabrication and have presented the fruits through some meetings and so on. Though basic equations of the dynamical model have characteristic nonlinearity, character of the nonlinearity has not been studied enough yet. In this paper, at first, we derive nonlinear equations from the dynamical model of drying process of polymer solution. Then we introduce results of numerical simulations of the nonlinear equations and consider roles of various parameters. Some of them are indirectly concerned in strength of non-equilibriumity. Through this study, we approach essential qualities of nonlinearity in non-equilibrium process of drying process.

Effect of simulated mechanical recycling processes on the structure and properties of poly(lactic acid).

PubMed

Beltrán, F R; Lorenzo, V; Acosta, J; de la Orden, M U; Martínez Urreaga, J

2018-06-15

The aim of this work is to study the effects of different simulated mechanical recycling processes on the structure and properties of PLA. A commercial grade of PLA was melt compounded and compression molded, then subjected to two different recycling processes. The first recycling process consisted of an accelerated ageing and a second melt processing step, while the other recycling process included an accelerated ageing, a demanding washing process and a second melt processing step. The intrinsic viscosity measurements indicate that both recycling processes produce a degradation in PLA, which is more pronounced in the sample subjected to the washing process. DSC results suggest an increase in the mobility of the polymer chains in the recycled materials; however the degree of crystallinity of PLA seems unchanged. The optical, mechanical and gas barrier properties of PLA do not seem to be largely affected by the degradation suffered during the different recycling processes. These results suggest that, despite the degradation of PLA, the impact of the different simulated mechanical recycling processes on the final properties is limited. Thus, the potential use of recycled PLA in packaging applications is not jeopardized. Copyright © 2017 Elsevier Ltd. All rights reserved.

A novel process route for the production of spherical SLS polymer powders

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

Schmidt, Jochen; Sachs, Marius; Blümel, Christina

2015-05-22

Currently, rapid prototyping gradually is transferred to additive manufacturing opening new applications. Especially selective laser sintering (SLS) is promising. One drawback is the limited choice of polymer materials available as optimized powders. Powders produced by cryogenic grinding show poor powder flowability resulting in poor device quality. Within this account we present a novel process route for the production of spherical polymer micron-sized particles of good flowability. The feasibility of the process chain is demonstrated for polystyrene e. In a first step polymer microparticles are produced by a wet grinding method. By this approach the mean particle size and the particlemore » size distribution can be tuned between a few microns and several 10 microns. The applicability of this method will be discussed for different polymers and the dependencies of product particle size distribution on stressing conditions and process temperature will be outlined. The comminution products consist of microparticles of irregular shape and poor powder flowability. An improvement of flowability of the ground particles is achieved by changing their shape: they are rounded using a heated downer reactor. The influence of temperature profile and residence time on the product properties will be addressed applying a viscous-flow sintering model. To further improve the flowability of the cohesive spherical polymer particles nanoparticles are adhered onto the microparticles’ surface. The improvement of flowability is remarkable: rounded and dry-coated powders exhibit a strongly reduced tensile strength as compared to the comminution product. The improved polymer powders obtained by the process route proposed open new possibilities in SLS processing including the usage of much smaller polymer beads.« less

Fingermark visualisation on uncirculated £5 (Bank of England) polymer notes: Initial process comparison studies.

PubMed

Downham, Rory P; Brewer, Eleigh R; King, Roberto S P; Luscombe, Aoife M; Sears, Vaughn G

2017-06-01

Experiments were conducted to investigate the effectiveness of a range of fingermark visualisation processes on brand new, uncirculated, £5 polymer banknotes (and their test note predecessors), as produced by the Bank of England (BoE). In the main study of this paper, a total of 14 individual processes were investigated on BoE £5 polymer banknotes, which included both 'Category A' processes (as recommended in the Home Office Fingermark Visualisation Manual) as well as recently developed processes, including fpNatural ® 2 powder (cuprorivaite) from Foster+Freeman and a vacuum metal deposition sequence that evaporates silver followed by zinc. Results from this preliminary investigation indicate that fpNatural ® 2, multimetal deposition, Wet Powder ™ Black, iron oxide powder suspension and black magnetic powder are the most effective processes on these uncirculated £5 BoE polymer banknotes, when viewed under "primary viewing" conditions (white light or fluorescence). Additional fingermarks were visualised on the polymer banknotes following the subsequent use of reflected infrared imaging and lifting techniques, and with the benefit of these techniques taken into consideration, the aforementioned processes remained amongst the most effective overall. This work provides initial insight into fingermark visualisation strategies for BoE £5 polymer banknotes, and the need for further studies in order to generate mature operational guidance is emphasised. Copyright © 2017 Elsevier B.V. All rights reserved.

Microwave Processing of Materials

DTIC Science & Technology

1994-01-01

up to many meters in electrically insulating materials, such as ceramics, polymers, and certain composite materials. As discussed in Chapter 2, the...for University of Illinois, Urbana Center: High Performance Polymeric Materials Technology 1206 West Green Street Adhesives & Composites United...Michigan State University, application of microwave processing to polymers and polymer composites Dr. Raymond Decker, University Science Partners

Probing polymer crystallization at processing-relevant cooling rates with synchrotron radiation

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

Cavallo, Dario, E-mail: Dario.cavallo@unige.it; Portale, Giuseppe; Androsch, René

2015-12-17

Processing of polymeric materials to produce any kind of goods, from films to complex objects, involves application of flow fields on the polymer melt, accompanied or followed by its rapid cooling. Typically, polymers solidify at cooling rates which span over a wide range, from a few to hundreds of °C/s. A novel method to probe polymer crystallization at processing-relevant cooling rates is proposed. Using a custom-built quenching device, thin polymer films are ballistically cooled from the melt at rates between approximately 10 and 200 °C/s. Thanks to highly brilliant synchrotron radiation and to state-of-the-art X-ray detectors, the crystallization process ismore » followed in real-time, recording about 20 wide angle X-ray diffraction patterns per second while monitoring the instantaneous sample temperature. The method is applied to a series of industrially relevant polymers, such as isotactic polypropylene, its copolymers and virgin and nucleated polyamide-6. Their crystallization behaviour during rapid cooling is discussed, with particular attention to the occurrence of polymorphism, which deeply impact material’s properties.« less

Dynamic-template-directed multiscale assembly for large-area coating of highly-aligned conjugated polymer thin films

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

Mohammadi, Erfan; Zhao, Chuankai; Meng, Yifei

Solution processable semiconducting polymers have been under intense investigations due to their diverse applications from printed electronics to biomedical devices. However, controlling the macromolecular assembly across length scales during solution coating remains a key challenge, largely due to the disparity in timescales of polymer assembly and high-throughput printing/coating. Herein we propose the concept of dynamic templating to expedite polymer nucleation and the ensuing assembly process, inspired by biomineralization templates capable of surface reconfiguration. Molecular dynamic simulations reveal that surface reconfigurability is key to promoting template–polymer interactions, thereby lowering polymer nucleation barrier. Employing ionic-liquid-based dynamic template during meniscus-guided coating results inmore » highly aligned, highly crystalline donor-acceptor polymer thin films over large area (41cm 2) and promoted charge transport along both the polymer backbone and the π-π stacking direction in field-effect transistors. We further demonstrate that the charge transport anisotropy can be reversed by tuning the degree of polymer backbone alignment.« less

Effects of Alkylthio and Alkoxy Side Chains in Polymer Donor Materials for Organic Solar Cells.

PubMed

Cui, Chaohua; Wong, Wai-Yeung

2016-02-01

Side chains play a considerable role not only in improving the solubility of polymers for solution-processed device fabrication, but also in affecting the molecular packing, electron affinity and thus the device performance. In particular, electron-donating side chains show unique properties when employed to tune the electronic character of conjugated polymers in many cases. Therefore, rational electron-donating side chain engineering can improve the photovoltaic properties of the resulting polymer donors to some extent. Here, a survey of some representative examples which use electron-donating alkylthio and alkoxy side chains in conjugated organic polymers for polymer solar cell applications will be presented. It is envisioned that an analysis of the effect of such electron-donating side chains in polymer donors would contribute to a better understanding of this kind of side chain behavior in solution-processed conjugated organic polymers for polymer solar cells. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dynamic-template-directed multiscale assembly for large-area coating of highly-aligned conjugated polymer thin films

PubMed Central

Mohammadi, Erfan; Zhao, Chuankai; Meng, Yifei; Qu, Ge; Zhang, Fengjiao; Zhao, Xikang; Mei, Jianguo; Zuo, Jian-Min; Shukla, Diwakar; Diao, Ying

2017-01-01

Solution processable semiconducting polymers have been under intense investigations due to their diverse applications from printed electronics to biomedical devices. However, controlling the macromolecular assembly across length scales during solution coating remains a key challenge, largely due to the disparity in timescales of polymer assembly and high-throughput printing/coating. Herein we propose the concept of dynamic templating to expedite polymer nucleation and the ensuing assembly process, inspired by biomineralization templates capable of surface reconfiguration. Molecular dynamic simulations reveal that surface reconfigurability is key to promoting template–polymer interactions, thereby lowering polymer nucleation barrier. Employing ionic-liquid-based dynamic template during meniscus-guided coating results in highly aligned, highly crystalline donor–acceptor polymer thin films over large area (>1 cm2) and promoted charge transport along both the polymer backbone and the π–π stacking direction in field-effect transistors. We further demonstrate that the charge transport anisotropy can be reversed by tuning the degree of polymer backbone alignment. PMID:28703136

Dynamic-template-directed multiscale assembly for large-area coating of highly-aligned conjugated polymer thin films

DOE PAGES

Mohammadi, Erfan; Zhao, Chuankai; Meng, Yifei; ...

2017-07-13

Solution processable semiconducting polymers have been under intense investigations due to their diverse applications from printed electronics to biomedical devices. However, controlling the macromolecular assembly across length scales during solution coating remains a key challenge, largely due to the disparity in timescales of polymer assembly and high-throughput printing/coating. Herein we propose the concept of dynamic templating to expedite polymer nucleation and the ensuing assembly process, inspired by biomineralization templates capable of surface reconfiguration. Molecular dynamic simulations reveal that surface reconfigurability is key to promoting template–polymer interactions, thereby lowering polymer nucleation barrier. Employing ionic-liquid-based dynamic template during meniscus-guided coating results inmore » highly aligned, highly crystalline donor-acceptor polymer thin films over large area (41cm 2) and promoted charge transport along both the polymer backbone and the π-π stacking direction in field-effect transistors. We further demonstrate that the charge transport anisotropy can be reversed by tuning the degree of polymer backbone alignment.« less

Low-temperature oxidizing plasma surface modification and composite polymer thin-film fabrication techniques for tailoring the composition and behavior of polymer surfaces

NASA Astrophysics Data System (ADS)

Tompkins, Brendan D.

This dissertation examines methods for modifying the composition and behavior of polymer material surfaces. This is accomplished using (1) low-temperature low-density oxidizing plasmas to etch and implant new functionality on polymers, and (2) plasma enhanced chemical vapor deposition (PECVD) techniques to fabricate composite polymer materials. Emphases are placed on the structure of modified polymer surfaces, the evolution of polymer surfaces after treatment, and the species responsible for modifying polymers during plasma processing. H2O vapor plasma modification of high-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene (PP), polystyrene (PS), polycarbonate (PC), and 75A polyurethane (PU) was examined to further our understanding of polymer surface reorganization leading to hydrophobic recovery. Water contact angles (wCA) measurements showed that PP and PS were the most susceptible to hydrophobic recovery, while PC and HDPE were the most stable. X-ray photoelectron spectroscopy (XPS) revealed a significant quantity of polar functional groups on the surface of all treated polymer samples. Shifts in the C1s binding energies (BE) with sample age were measured on PP and PS, revealing that surface reorganization was responsible for hydrophobic recovery on these materials. Differential scanning calorimetry (DSC) was used to rule out the intrinsic thermal properties as the cause of reorganization and hydrophobic recovery on HDPE, LDPE, and PP. The different contributions that polymer cross-linking and chain scission mechanisms make to polymer aging effects are considered. The H2O plasma treatment technique was extended to the modification of 0.2 microm and 3.0 microm track-etched polycarbonate (PC-TE) and track-etched polyethylene terephthalate (PET-TE) membranes with the goal of permanently increasing the hydrophilicity of the membrane surfaces. Contact angle measurements on freshly treated and aged samples confirmed the wettability of the membrane surfaces was significantly improved by plasma treatment. XPS and SEM analyses revealed increased oxygen incorporation onto the surface of the membranes, without any damage to the surface or pore structure. Contact angle measurements on a membrane treated in a stacked assembly suggest the plasma effectively modified the entire pore cross section. Plasma treatment also increased water flux through the membranes, with results from plasma modified membranes matching those from commercially available hydrophilic membranes (treated with wetting agent). Mechanisms for the observed modification are discussed in terms of OH and O radicals implanting oxygen functionality into the polymers. Oxidizing plasma systems (O2, CO2, H2O vapor, and formic acid vapor) were used to modify track-etched polycarbonate membranes and explore the mechanisms and species responsible for etching polycarbonate during plasma processing. Etch rates were measured using scanning electron microscopy; modified polycarbonate surfaces were further characterized using x-ray photoelectron spectroscopy and water contact angles. Etch rates and surface characterization results were combined with optical emission spectroscopy data used to identify gas-phase species and their relative densities. Although the oxide functionalities implanted by each plasma system were similar, the H2O vapor and formic acid vapor plasmas yielded the lowest contact angles after treatment. The CO2, H2O vapor, and formic acid vapor plasma-modified surfaces were, however, found to be similarly stable one month after treatment. Overall, etch rate correlated directly to the relative gas-phase density of atomic oxygen and, to a lesser extent, hydroxyl radicals. PECVD of acetic acid vapor (CH3COOH) was used to deposit films on PC-TE and silicon wafer substrates. The CH3COOH films were characterized using XPS, wCA, and SEM. This modification technique resulted in continuous deposition and self-limiting deposition of a-CxO yHz films on Si wafers and PC-TE, respectively. The self-limiting deposition on PC-TE revealed that resulting films have minimal impact on 3D PC structures. This technique would allow for more precise fabrication of patterned or nano-textured PC. PECVD is used to synthesize hydrocarbon/fluorocarbon thin films with compositional gradients by continuously changing the ratio of gases in a C 3F8/H2 plasma. The films are characterized using variable angle spectroscopic ellipsometry (VASE), Fourier transform infrared spectroscopy (FTIR), XPS, wCA, and SEM. These methods revealed that shifting spectroscopic signals can be used to characterize organization in the deposited film. Using these methods, along with gas-phase diagnostics, film chemistry and the underlying deposition mechanisms are elucidated, leading to a model that accurately predicts film thickness.

Processing and characterization of natural cellulose fibers/thermoset polymer composites.

PubMed

Thakur, Vijay Kumar; Thakur, Manju Kumari

2014-08-30

Recently natural cellulose fibers from different biorenewable resources have attracted the considerable attraction of research community all around the globe owing to their unique intrinsic properties such as biodegradability, easy availability, environmental friendliness, flexibility, easy processing and impressive physico-mechanical properties. Natural cellulose fibers based materials are finding their applications in a number of fields ranging from automotive to biomedical. Natural cellulose fibers have been frequently used as the reinforcement component in polymers to add the specific properties in the final product. A variety of cellulose fibers based polymer composite materials have been developed using various synthetic strategies. Seeing the immense advantages of cellulose fibers, in this article we discuss the processing of biorenewable natural cellulose fibers; chemical functionalization of cellulose fibers; synthesis of polymer resins; different strategies to prepare cellulose based green polymer composites, and diverse applications of natural cellulose fibers/polymer composite materials. The article provides an in depth analysis and comprehensive knowledge to the beginners in the field of natural cellulose fibers/polymer composites. The prime aim of this review article is to demonstrate the recent development and emerging applications of natural cellulose fibers and their polymer materials. Copyright © 2014 Elsevier Ltd. All rights reserved.

Damage of polyesters by the atmospheric free radical oxidant NO3 •: a product study involving model systems

PubMed Central

Goeschen, Catrin

2013-01-01

Summary Manufactured polymer materials are used in increasingly demanding applications, but their lifetime is strongly influenced by environmental conditions. In particular, weathering and ageing leads to dramatic changes in the properties of the polymers, which results in decreased service life and limited usage. Despite the heavy reliance of our society on polymers, the mechanism of their degradation upon exposure to environmental oxidants is barely understood. In this work, model systems of important structural motifs in commercial high-performing polyesters were used to study the reaction with the night-time free radical oxidant NO3 • in the absence and presence of other radical and non-radical oxidants. Identification of the products revealed ‘hot spots’ in polyesters that are particularly vulnerable to attack by NO3 • and insight into the mechanism of oxidative damage by this environmentally important radical. It is suggested that both intermediates as well as products of these reactions are potentially capable of promoting further degradation processes in polyesters under environmental conditions. PMID:24204400

Penetration of carbon-fabric-reinforced composites by edge cracks during thermal aging

NASA Technical Reports Server (NTRS)

Bowles, Kenneth J.; Kamvouris, John E.

1994-01-01

Thermo-oxidative stability (TOS) test results are significantly influenced by the formation and growth or presence of interlaminar and interlaminar cracks in the cut edges of all carbon-fiber-crosslinked high-temperature polymer matrix composites(exp 1-5) (i.e., unidirectional, crossplied, angle-plied, and fabric composites). The thermo-oxidative degradation of these composites is heavily dependent on the surface area that is exposed to the harmful environment and on the surface-to-volume ratio of the structure under study. Since the growth of cracks and voids on the composite surfaces significantly increases the exposed surface areas, it is imperative that the interaction between the aging process and the formation of new surface area as the aging time progresses be understood.

Effects of polymer-nanoparticle interactions on the viscosity of unentangled polymers under extreme nanoconfinement during capillary rise infiltration.

PubMed

Hor, Jyo Lyn; Wang, Haonan; Fakhraai, Zahra; Lee, Daeyeon

2018-03-28

We explore the effect of confinement and polymer-nanoparticle interactions on the viscosity of unentangled polymers undergoing capillary rise infiltration (CaRI) in dense packings of nanoparticles. In CaRI, a polymer is thermally induced to wick into the dense packings of nanoparticles, leading to the formation of polymer-infiltrated nanoparticle films, a new class of thin film nanocomposites with extremely high concentrations of nanoparticles. To understand the effect of this extreme nanoconfinement, as well as polymer-nanoparticle interactions on the polymer viscosity in CaRI films, we use two polymers that are known to have very different interactions with SiO2 nanoparticles. Using in situ spectroscopic ellipsometry, we monitor the polymer infiltration process, from which we infer the polymer viscosity based on the Lucas-Washburn model. Our results suggest that physical confinement increases the viscosity by approximately two orders of magnitude. Furthermore, confinement also increases the glass transition temperature of both polymers. Thus, under extreme nanoconfinement, the physical confinement has a more significant impact than the polymer-nanoparticle interactions on the viscosity of unentangled polymers, measured through infiltration dynamics, as well as the glass transition temperature. These findings will provide fundamental frameworks for designing processes to enable the fabrication of CaRI nanocomposite films with a wide range of nanoparticles and polymers.

Characterization of Volatile Nylon 6.6 Thermal-Oxidative Degradation Products by Selective Isotopic Labeling and Cryo-GC/MS

NASA Astrophysics Data System (ADS)

Smith, Jonell N.; V. White, Gregory; White, Michael I.; Bernstein, Robert; Hochrein, James M.

2012-09-01

Aged materials, such as polymers, can exhibit modifications to their chemical structure and physical properties, which may render the material ineffective for its intended purpose. Isotopic labeling was used to characterize low-molecular weight volatile thermal-oxidative degradation products of nylon 6.6 in an effort to better understand and predict changes in the aged polymer. Headspace gas from aged (up to 243 d at 138 °C) nylon 6.6 monomers (adipic acid and 1,6-hexanediamine) and polymer were preconcentrated, separated, and detected using cryofocusing gas chromatography mass spectrometry (cryo-GC/MS). Observations regarding the relative concentrations observed in each chromatographic peak with respect to aging time were used in conjunction with mass spectra for samples aged under ambient air to determine the presence and identity of 18 degradation products. A comparison of the National Institute of Standards and Technology (NIST) library, unlabeled, and isotopically labeled mass spectra (C-13 or N-15) and expected fragmentation pathways of each degradation product were used to identify the location of isotopically labeled atoms within the product's chemical structure, which can later be used to determine the exact origin of the species. In addition, observations for unlabeled nylon 6.6 aged in an O-18 enriched atmosphere were used to determine if the source of oxygen in the applicable degradation products was from the gaseous environment or the polymer. Approximations for relative isotopic ratios of unlabeled to labeled products are reported, where appropriate.

Process for crosslinking methylene-containing aromatic polymers with ionizing radiation

NASA Technical Reports Server (NTRS)

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

1990-01-01

A process for crosslinking aromatic polymers containing radiation-sensitive methylene groups (-CH2-) by exposing the polymers to ionizing radiation thereby causing crosslinking of the polymers through the methylene groups is described. Crosslinked polymers are resistant to most organic solvents such as acetone, alcohols, hydrocarbons, methylene, chloride, chloroform, and other halogenated hydrocarbons, to common fuels and to hydraulic fluids in contrast to readily soluble uncrosslinked polymers. In addition, the degree of crosslinking of the polymers depends upon the percentage of the connecting groups which are methylene which ranges from 5 to 50 pct and preferably from 25 to 50 pct of the connecting groups, and is also controlled by the level of irradiation which ranges from 25 to 1000 Mrads and preferably from 25 to 250 Mrads. The temperature of the reaction conditions ranges from 25 to 200 C and preferably at or slightly above the glass transition temperature of the polymer. The crosslinked polymers are generally more resistant to degradation at elevated temperatures such as greater than 150 C, have a reduced tendency to creep under load, and show no significant embrittlement of parts fabricated from the polymers.

[Safety and structural analysis of polymers produced in manufacturing process of alpha-lipoic acid].

PubMed

Shimoda, Hiroshi; Tanaka, Junji; Seki, Azusa; Honda, Haruya; Akaogi, Seiichiro; Komatsubara, Hirobumi; Suzuki, Nobuo; Kameyama, Mayumi; Tamura, Satoru; Murakami, Nobutoshi

2007-10-01

Alpha-Lipoic acid has recently been permitted for use in foodstuffs and is contained in tablets and capsules. Although alpha-lipoic acid is synthesized from adipic acid, the safety of polymers produced during the purification and drying processes has been an issue of concern. Hence, we examined the safety profiles of thermally denatured polymer (LAP-A) and ethanol-denatured polymer (LAP-B) produced in the manufacturing process of alpha-lipoic acid. Furthermore, we conducted structural analysis of these polymers by 1H-NMR and FAB-MS spectroscopy. In a consecutive ingestion test, male and female mice ingested diet containing 0.1 and 0.2% LAP-A and -B for 4 weeks. Blood uric acid, potassium and lactate dehydrogenase (LDH) tended to increase without dose-dependency. Relative liver weights were also increased. However, male dogs that were orally administered LAP-B (500 mg/kg) once did not show any abnormalities in blood parameters or general condition. These findings indicate that alpha-lipoic acid polymers are not acutely toxic; however, chronic ingestion of these polymers may affect liver and kidney functions.

Crosslink Density and Molecular Weight Effects on the Viscoelastic Response of a Glassy High-Performance Polyimide

NASA Technical Reports Server (NTRS)

Nicholson, Lee M.; Whitley, Karen S.; Gates, Thomas S.

2001-01-01

Durability and long-term performance are among the primary concerns for the use of advanced polymer matrix composites (PMCs) in modern aerospace structural applications. For a PMC subJected to long-term exposure at elevated temperatures. the viscoelastic nature of the polymer matrix will contribute to macroscopic changes in composite stiffness, strength and fatigue life. Over time. changes in the polymer due to physical aging will have profound effects on tile viscoelastic compliance of the material, hence affecting its long-term durability. Thus, the ability to predict material performance using intrinsic properties, such as crosslink density and molecular weight, would greatly enhance the efficiency of design and development of PMCs. The objective of this paper is to discuss and present the results of an experimental study that considers the effects of crosslink density, molecular weight and temperature on the viscoelastic behavior including physical aging of an advanced polymer. Five distinct variations in crosslink density were used to evaluate the differences in mechanical performance of an advanced polyimide. The physical aging behavior was isolated by conducting sequenced, short-term isothermal creep compliance tests in tension. These tests were performed over a range of sub-glass transition temperatures. The material constants, material master curves and physical aging-related parameters were evaluated as a function of temperature crosslink density and molecular weight using time-temperature and time-aging time superposition techniques.

Precursors for the polymer-assisted deposition of films

DOEpatents

McCleskey, Thomas M.; Burrell, Anthony K.; Jia, Quanxi; Lin, Yuan

2013-09-10

A polymer assisted deposition process for deposition of metal oxide films is presented. The process includes solutions of one or more metal precursor and soluble polymers having binding properties for the one or more metal precursor. After a coating operation, the resultant coating is heated at high temperatures to yield metal oxide films. Such films can be epitaxial in structure and can be of optical quality. The process can be organic solvent-free.

Characterization and measurement of polymer wear

NASA Technical Reports Server (NTRS)

Buckley, D. H.; Aron, P. R.

1984-01-01

Analytical tools which characterize the polymer wear process are discussed. The devices discussed include: visual observation of polymer wear with SEM, the quantification with surface profilometry and ellipsometry, to study the chemistry with AES, XPS and SIMS, to establish interfacial polymer orientation and accordingly bonding with QUARTIR, polymer state with Raman spectroscopy and stresses that develop in polymer films using a X-ray double crystal camera technique.

Thickening compositions, and related materials and processes

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

O'Brien, Michael Joseph; Perry, Robert James; Enick, Robert Michael

A silicone polymer is provided, modified with at least one functional group from the class of anthraquinone amide groups; anthraquinone sulfonamide groups; thioxanthone amide groups; or thioxanthone sulfone amide groups. The polymer can be combined with a hydrocarbon solvent or with supercritical carbon dioxide (CO.sub.2), and is very effective for increasing the viscosity of either medium. A process for the recovery of oil from a subterranean, oil-bearing formation is also described, using supercritical carbon dioxide modified with the functionalized silicone polymer. A process for extracting natural gas or oil from a bedrock-shale formation is also described, again using the modifiedmore » silicone polymer.« less

Gas-separation process

DOEpatents

Toy, L.G.; Pinnau, I.; Baker, R.W.

1994-01-25

A process is described for separating condensable organic components from gas streams. The process makes use of a membrane made from a polymer material that is glassy and that has an unusually high free volume within the polymer material. 6 figures.

The materials processing research base of the Materials Processing Center

NASA Technical Reports Server (NTRS)

Flemings, M. C.; Bowen, H. K.; Kenney, G. B.

1980-01-01

The goals and activities of the center are discussed. The center activities encompass all engineering materials including metals, ceramics, polymers, electronic materials, composites, superconductors, and thin films. Processes include crystallization, solidification, nucleation, and polymer synthesis.

Processes for preparing carbon fibers using sulfur trioxide in a halogenated solvent

DOEpatents

Patton, Jasson T.; Barton, Bryan E.; Bernius, Mark T.; Chen, Xiaoyun; Hukkanen, Eric J.; Rhoton, Christina A.; Lysenko, Zenon

2015-12-29

Disclosed here are processes for preparing carbonized polymers (preferably carbon fibers), comprising sulfonating a polymer with a sulfonating agent that comprises SO.sub.3 dissolved in a solvent to form a sulfonated polymer; treating the sulfonated polymer with a heated solvent, wherein the temperature of the solvent is at least 95.degree. C.; and carbonizing the resulting product by heating it to a temperature of 500-3000.degree. C. Carbon fibers made according to these methods are also disclosed herein.

Interdiffusion of Polycarbonate in Fused Deposition Modeling Welds

NASA Astrophysics Data System (ADS)

Seppala, Jonathan; Forster, Aaron; Satija, Sushil; Jones, Ronald; Migler, Kalman

2015-03-01

Fused deposition modeling (FDM), a now common and inexpensive additive manufacturing method, produces 3D objects by extruding molten polymer layer-by-layer. Compared to traditional polymer processing methods (injection, vacuum, and blow molding), FDM parts have inferior mechanical properties, surface finish, and dimensional stability. From a polymer processing point of view the polymer-polymer weld between each layer limits the mechanical strength of the final part. Unlike traditional processing methods, where the polymer is uniformly melted and entangled, FDM welds are typically weaker due to the short time available for polymer interdiffusion and entanglement. To emulate the FDM process thin film bilayers of polycarbonate/d-polycarbonate were annealed using scaled times and temperatures accessible in FDM. Shift factors from Time-Temperature Superposition, measured by small amplitude oscillatory shear, were used to calculate reasonable annealing times (min) at temperatures below the actual extrusion temperature. The extent of interdiffusion was then measured using neutron reflectivity. Analogous specimens were prepared to characterize the mechanical properties. FDM build parameters were then related to interdiffusion between welded layers and mechanical properties. Understating the relationship between build parameters, interdiffusion, and mechanical strength will allow FDM users to print stronger parts in an intelligent manner rather than using trial-and-error and build parameter lock-in.

Overview of EO polymers and polymer modulator stability

NASA Astrophysics Data System (ADS)

Lindsay, Geoffrey A.; Ashley, Paul R.; Guenther, Andrew P.; Sanghadasa, Mohan

2005-09-01

This is a brief overview of the technology of nonlinear optical polymers (NLOP) and their use in electro-optic (EO) modulators. This paper also covers preliminary results from the authors' laboratories on highly active CLD- and FTC-type chromophores in guest-host films of APC amorphous polycarbonate. Emphasis will be given to thermal stability and long-term EO modulator aging.

Analytical pyrolysis mass spectrometry: new vistas opened by temperature-resolved in-source PYMS

NASA Astrophysics Data System (ADS)

Boon, Jaap J.

1992-09-01

Analytical pyrolysis mass spectrometry (PYMS) is introduced and its applications to the analysis of synthetic polymers, biopolymers, biomacromolecular systems and geomacromolecules are critically reviewed. Analytical pyrolysis inside the ionisation chamber of a mass spectrometer, i.e. in-source PYMS, gives a complete inventory of the pyrolysis products evolved from a solid sample. The temperature-resolved nature of the experiment gives a good insight into the temperature dependence of the volatilisation and pyrolytic dissociation processes. Chemical ionisation techniques appear to be especially suitable for the analysis of oligomeric fragments released in early stages of the pyrolysis of polymer systems. Large oligomeric fragments were observed for linear polymers such as cellulose (pentadecamer), polyhydroxyoctanoic acid (tridecamer) and polyhydroxybutyric acid (heneicosamer). New in-source PYMS data are presented on artists' paints, the plant polysaccharides cellulose and xyloglucan, several microbial polyhydroxyalkanoates, wood and enzyme-digested wood, biodegraded roots and a fossil cuticle of Miocene age. On-line and off-line pyrolysis chromatography mass spectrometric approaches are also discussed. New data presented on high temperature gas chromatography--mass spectrometry of deuterio-reduced permethylated pyrolysates of cellulose lead to a better understanding of polysaccharide dissociation mechanisms. Pyrolysis as an on-line sample pretreatment method for organic macromolecules in combination with MS techniques is a very challenging field of mass spectrometry. Pyrolytic dissociation and desorption is not at all a chaotic process but proceeds according to very specific mechanisms.

Direct fabrication of silicone lenses with 3D printed parts

NASA Astrophysics Data System (ADS)

Kamal, Tahseen; Watkins, Rachel; Cen, Zijian; Lee, W. M.

2016-11-01

The traditional process of making glass lenses requires grinding and polishing of the material which is a tedious and sensitive process. Existing polymer lens making techniques, such as high temperature reflow techniques, have been significantly simple lens making processes which cater well to customer industry. Recently, the use of UV-curing liquid lens has ushered in customized lens making (Printed Optics), but contains undesirable yellowing effects. Polydimethylsiloxane (PDMS) is a transparent polymer curable at low temperature (<100°C) provides an alternative to lens making. In this work, we showed that PDMS lenses are fabricated using single silicone droplets which are formed in a guided and controlled passive manner using 3D printed tools. These silicone lenses have attributes such as smoothness of curvature, resilience to temperature change, low optical aberrations, high transparency (>95%) and minimal aging (yellowing). Moreover, these lenses have a range of focal lengths (3.5 mm to 14.5 mm as well as magnifications (up to 160X). In addition, we created smartphone attachment to turn smart device (tablet or smartphone) into a low-powered microscope. In future we plan to extend this method to produce microlens array.

Processing of Fine-Scale Piezoelectric Ceramic/Polymer Composites for Sensors and Actuators

NASA Technical Reports Server (NTRS)

Janas, V. F.; Safari, A.

1996-01-01

The objective of the research effort at Rutgers is the development of lead zirconate titanate (PZT) ceramic/polymer composites with different designs for transducer applications including hydrophones, biomedical imaging, non-destructive testing, and air imaging. In this review, methods for processing both large area and multifunctional ceramic/polymer composites for acoustic transducers were discussed.

Angular dependence of etch rates in the etching of poly-Si and fluorocarbon polymer using SF6, C4F8, and O2 plasmas

NASA Astrophysics Data System (ADS)

Min, Jae-Ho; Lee, Gyeo-Re; Lee, Jin-Kwan; Moon, Sang Heup; Kim, Chang-Koo

2004-05-01

The dependences of etch rates on the angle of ions incident on the substrate surface in four plasma/substrate systems that constitute the advanced Bosch process were investigated using a Faraday cage designed for the accurate control of the ion-incident angle. The four systems, established by combining discharge gases and substrates, were a SF6/poly-Si, a SF6/fluorocarbon polymer, an O2/fluorocarbon polymer, and a C4F8/Si. In the case of SF6/poly-Si, the normalized etch rates (NERs), defined as the etch rates normalized by the rate on the horizontal surface, were higher at all angles than values predicted from the cosine of the ion-incident angle. This characteristic curve shape was independent of changes in process variables including the source power and bias voltage. Contrary to the earlier case, the NERs for the O2/polymer decreased and eventually reached much lower values than the cosine values at angles between 30° and 70° when the source power was increased and the bias voltage was decreased. On the other hand, the NERs for the SF6/polymer showed a weak dependence on the process variables. In the case of C4F8/Si, which is used in the Bosch process for depositing a fluorocarbon layer on the substrate surface, the deposition rate varied with the ion incident angle, showing an S-shaped curve. These characteristic deposition rate curves, which were highly dependent on the process conditions, could be divided into four distinct regions: a Si sputtering region, an ion-suppressed polymer deposition region, an ion-enhanced polymer deposition region, and an ion-free polymer deposition region. Based on the earlier characteristic angular dependences of the etch (or deposition) rates in the individual systems, ideal process conditions for obtaining an anisotropic etch profile in the advanced Bosch process are proposed. .

Dry powder process for preparing uni-tape prepreg from polymer powder coated filamentary towpregs

NASA Technical Reports Server (NTRS)

Wilkinson, Steven P. (Inventor); Johnston, Norman J. (Inventor); Marchello, Joseph M. (Inventor)

1997-01-01

A process for preparing uni-tape prepreg from polymer powder coated filamentary towpregs is provided. A plurality of polymer powder coated filamentary towpregs are provided. The towpregs are collimated so that each towpreg is parallel. A material is applied to each side of the towpreg to form a sandwich. The sandwich is heated to a temperature wherein the polymer flows and intimately contacts the filaments and pressure is repeatedly applied perpendicularly to the sandwich with a longitudinal oscillating action wherein the filaments move apart and the polymer wets the filaments forming a uni-tape prepreg. The uni-tape prepreg is subsequently cooled.

Investigation of the adhesion properties of direct 3D printing of polymers and nanocomposites on textiles: Effect of FDM printing process parameters

NASA Astrophysics Data System (ADS)

Hashemi Sanatgar, Razieh; Campagne, Christine; Nierstrasz, Vincent

2017-05-01

In this paper, 3D printing as a novel printing process was considered for deposition of polymers on synthetic fabrics to introduce more flexible, resource-efficient and cost effective textile functionalization processes than conventional printing process like screen and inkjet printing. The aim is to develop an integrated or tailored production process for smart and functional textiles which avoid unnecessary use of water, energy, chemicals and minimize the waste to improve ecological footprint and productivity. Adhesion of polymer and nanocomposite layers which were 3D printed directly onto the textile fabrics using fused deposition modeling (FDM) technique was investigated. Different variables which may affect the adhesion properties including 3D printing process parameters, fabric type and filler type incorporated in polymer were considered. A rectangular shape according to the peeling standard was designed as 3D computer-aided design (CAD) to find out the effect of the different variables. The polymers were printed in different series of experimental design: nylon on polyamide 66 (PA66) fabrics, polylactic acid (PLA) on PA66 fabric, PLA on PLA fabric, and finally nanosize carbon black/PLA (CB/PLA) and multi-wall carbon nanotubes/PLA (CNT/PLA) nanocomposites on PLA fabrics. The adhesion forces were quantified using the innovative sample preparing method combining with the peeling standard method. Results showed that different variables of 3D printing process like extruder temperature, platform temperature and printing speed can have significant effect on adhesion force of polymers to fabrics while direct 3D printing. A model was proposed specifically for deposition of a commercial 3D printer Nylon filament on PA66 fabrics. In the following, among the printed polymers, PLA and its composites had high adhesion force to PLA fabrics.

Manipulating Semicrystalline Polymers in Confinement.

PubMed

Shingne, Nitin; Geuss, Markus; Thurn-Albrecht, Thomas; Schmidt, Hans-Werner; Mijangos, Carmen; Steinhart, Martin; Martín, Jaime

2017-08-17

Because final properties of nanoscale polymeric structures are largely determined by the solid-state microstructure of the confined polymer, it is imperative not only to understand how the microstructure of polymers develops under nanoscale confinement but also to establish means to manipulate it. Here we present a series of processing strategies, adapted from methods used in bulk polymer processing, that allow us to control the solidification of polymer nanostructures. First, we show that supramolecular nucleating agents can be readily used to modify the crystallization kinetics of confined poly(vinylidene fluoride) (PVDF). In addition, we demonstrate that microstructural features that are not traditionally affected by nucleating agents, such as the orientation of crystals, can be tuned with the crystallization temperature applied. Interestingly, we also show that high crystallization temperatures and long annealing periods induce the formation of the γ modification of PVDF, hence enabling the simple production of ferro/piezoelectric nanostructures. We anticipate that the approaches presented here can open up a plethora of new possibilities for the processing of polymer-based nanostructures with tailored properties and functionalities.

Process for making polymers comprising derivatized carbon nanotubes and compositions thereof

NASA Technical Reports Server (NTRS)

Tour, James M. (Inventor); Bahr, Jeffrey L. (Inventor); Yang, Jiping (Inventor)

2007-01-01

The present invention incorporates new processes for blending derivatized carbon nanotubes into polymer matrices to create new polymer/composite materials. When modified with suitable chemical groups using diazonium chemistry, the nanotubes can be made chemically compatible with a polymer matrix, allowing transfer of the properties of the nanotubes (such as mechanical strength) to the properties of the composite material as a whole. To achieve this, the derivatized (modified) carbon nanotubes are physically blended with the polymeric material, and/or, if desired, allowed to react at ambient or elevated temperature. These methods can be utilized to append functionalities to the nanotubes that will further covalently bond to the host polymer matrix, or directly between two tubes themselves. Furthermore, the nanotubes can be used as a generator of polymer growth, wherein the nanotubes are derivatized with a functional group that is an active part of a polymerization process, which would also result in a composite material in which the carbon nanotubes are chemically involved.

Electrical condition monitoring method for polymers

DOEpatents

Watkins, Jr., Kenneth S.; Morris, Shelby J [Hampton, VA; Masakowski, Daniel D [Worcester, MA; Wong, Ching Ping [Duluth, GA; Luo, Shijian [Boise, ID

2008-08-19

An electrical condition monitoring method utilizes measurement of electrical resistivity of an age sensor made of a conductive matrix or composite disposed in a polymeric structure such as an electrical cable. The conductive matrix comprises a base polymer and conductive filler. The method includes communicating the resistivity to a measuring instrument and correlating resistivity of the conductive matrix of the polymeric structure with resistivity of an accelerated-aged conductive composite.

Polymers for 3D Printing and Customized Additive Manufacturing.

PubMed

Ligon, Samuel Clark; Liska, Robert; Stampfl, Jürgen; Gurr, Matthias; Mülhaupt, Rolf

2017-08-09

Additive manufacturing (AM) alias 3D printing translates computer-aided design (CAD) virtual 3D models into physical objects. By digital slicing of CAD, 3D scan, or tomography data, AM builds objects layer by layer without the need for molds or machining. AM enables decentralized fabrication of customized objects on demand by exploiting digital information storage and retrieval via the Internet. The ongoing transition from rapid prototyping to rapid manufacturing prompts new challenges for mechanical engineers and materials scientists alike. Because polymers are by far the most utilized class of materials for AM, this Review focuses on polymer processing and the development of polymers and advanced polymer systems specifically for AM. AM techniques covered include vat photopolymerization (stereolithography), powder bed fusion (SLS), material and binder jetting (inkjet and aerosol 3D printing), sheet lamination (LOM), extrusion (FDM, 3D dispensing, 3D fiber deposition, and 3D plotting), and 3D bioprinting. The range of polymers used in AM encompasses thermoplastics, thermosets, elastomers, hydrogels, functional polymers, polymer blends, composites, and biological systems. Aspects of polymer design, additives, and processing parameters as they relate to enhancing build speed and improving accuracy, functionality, surface finish, stability, mechanical properties, and porosity are addressed. Selected applications demonstrate how polymer-based AM is being exploited in lightweight engineering, architecture, food processing, optics, energy technology, dentistry, drug delivery, and personalized medicine. Unparalleled by metals and ceramics, polymer-based AM plays a key role in the emerging AM of advanced multifunctional and multimaterial systems including living biological systems as well as life-like synthetic systems.

Polymers for 3D Printing and Customized Additive Manufacturing

PubMed Central

2017-01-01

Additive manufacturing (AM) alias 3D printing translates computer-aided design (CAD) virtual 3D models into physical objects. By digital slicing of CAD, 3D scan, or tomography data, AM builds objects layer by layer without the need for molds or machining. AM enables decentralized fabrication of customized objects on demand by exploiting digital information storage and retrieval via the Internet. The ongoing transition from rapid prototyping to rapid manufacturing prompts new challenges for mechanical engineers and materials scientists alike. Because polymers are by far the most utilized class of materials for AM, this Review focuses on polymer processing and the development of polymers and advanced polymer systems specifically for AM. AM techniques covered include vat photopolymerization (stereolithography), powder bed fusion (SLS), material and binder jetting (inkjet and aerosol 3D printing), sheet lamination (LOM), extrusion (FDM, 3D dispensing, 3D fiber deposition, and 3D plotting), and 3D bioprinting. The range of polymers used in AM encompasses thermoplastics, thermosets, elastomers, hydrogels, functional polymers, polymer blends, composites, and biological systems. Aspects of polymer design, additives, and processing parameters as they relate to enhancing build speed and improving accuracy, functionality, surface finish, stability, mechanical properties, and porosity are addressed. Selected applications demonstrate how polymer-based AM is being exploited in lightweight engineering, architecture, food processing, optics, energy technology, dentistry, drug delivery, and personalized medicine. Unparalleled by metals and ceramics, polymer-based AM plays a key role in the emerging AM of advanced multifunctional and multimaterial systems including living biological systems as well as life-like synthetic systems. PMID:28756658

Investigation of Thermal and Viscoelastic Properties of Polymers Relevant to Hot Melt Extrusion, IV: Affinisol™ HPMC HME Polymers.

PubMed

Gupta, Simerdeep Singh; Solanki, Nayan; Serajuddin, Abu T M

2016-02-01

Most cellulosic polymers cannot be used as carriers for preparing solid dispersion of drugs by hot melt extrusion (HME) due to their high melt viscosity and thermal degradation at high processing temperatures. Three HME-grade hydroxypropyl methylcelluloses, namely Affinisol™ HPMC HME 15 cP, Affinisol™ HPMC HME 100 cP, and Affinisol™ HPMC HME 4 M, have recently been introduced by The Dow Chemical Co. to enable the preparation of solid dispersion at lower and more acceptable processing temperatures. In the present investigation, physicochemical properties of the new polymers relevant to HME were determined and compared with that of Kollidon(®) VA 64. Powder X-ray diffraction (PXRD), modulated differential scanning calorimetry (mDSC), thermogravimetric analysis (TGA), moisture sorption, rheology, and torque analysis by melt extrusion were applied. PXRD and mDSC showed that the Affinisol™ polymers were amorphous in nature. According to TGA, the onset of degradation for all polymers was >220°C. The Affinisol™ polymers exhibited less hygroscopicity than Kollidon(®) VA 64 and another HPMC polymer, Methocel™ K100LV. The complex viscosity profiles of the Affinisol™ polymers as a function of temperature were similar. The viscosity of the Affinisol™ polymers was highly sensitive to the shear rate applied, and unlike Kollidon(®) VA 64, the viscosity decreased drastically when the angular frequency was increased. Because of the very high shear rate encountered during melt extrusion, Affinisol™ polymers showed capability of being extruded at larger windows of processing temperatures as compared to that of Kollidon(®) VA 64.

Space and surface charge behavior analysis of charge-eliminated polymer films

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

Oda, Tetsuji; Takashima, Kazunori; Ichiyama, Shinichiro

1995-12-31

Charge behavior of corona-charged or charge eliminated polymer films being dipped in the city water were studied. They were polytetrafluoroethylene (PTFE teflon{trademark}), polypropylene (PP), low density or high density polyethylene (LDPE or HDPE) thin films which are as grown (native) or plasma-processed. The plasma processing at low pressure was tested as antistatic processing. Charge elimination was done by being dipped in alcohol or city water. TSDC analysis and surface charge profile measurement were done for both charged and charge eliminated polymer films. Surface charge density of plasma processed polymer films just after corona charging is roughly the same as thatmore » of an original film. There is little difference between surface charge density profile of a native film and that of a plasma processed film. A large hetero current peak of TSDC was observed at room temperature for a processed film. It was found that the hetero peak disappears after charge elimination process. A pressure pulse wave method by using a pulse-driven piezoelectric PVDF polymer film as a piezoelectric actuator was newly developed to observe real space charge distribution. A little difference of internal space charge distribution between the plasma processed film and the native one after corona charging is found.« less

The effect of polymer aging on the uptake of fuel aromatics and ethers by microplastics.

PubMed

Müller, Axel; Becker, Roland; Dorgerloh, Ute; Simon, Franz-Georg; Braun, Ulrike

2018-05-14

Microplastics are increasingly entering marine, limnic and terrestrial ecosystems worldwide, where they sorb hydrophobic organic contaminants. Here, the sorption behavior of the fuel-related water contaminants benzene, toluene, ethyl benzene and xylene (BTEX) and four tertiary butyl ethers to virgin and via UV radiation aged polypropylene (PP) and polystyrene (PS) pellets was investigated. Changes in material properties due to aging were recorded using appropriate polymer characterization methods, such as differential scanning calorimetry, Fourier transform infrared spectroscopy, gel permeation chromatography, X-ray photoelectron spectroscopy, and microscopy. Pellets were exposed to water containing BTEX and the ethers at 130-190 μg L -1 for up to two weeks. Aqueous sorbate concentrations were determined by headspace gas chromatography. Sorption to the polymers was correlated with the sorbate's K ow and was significant for BTEX and marginal for the ethers. Due to substantially lower glass transition temperatures, PP showed higher sorption than PS. Aging had no effect on the sorption behavior of PP. PS sorbed less BTEX after aging due to an oxidized surface layer. Copyright © 2018 Elsevier Ltd. All rights reserved.

Photoinitiated grafting of porous polymer monoliths and thermoplastic polymers for microfluidic devices

DOEpatents

Frechet, Jean M. J. [Oakland, CA; Svec, Frantisek [Alameda, CA; Rohr, Thomas [Leiden, NL

2008-10-07

A microfluidic device preferably made of a thermoplastic polymer that includes a channel or a multiplicity of channels whose surfaces are modified by photografting. The device further includes a porous polymer monolith prepared via UV initiated polymerization within the channel, and functionalization of the pore surface of the monolith using photografting. Processes for making such surface modifications of thermoplastic polymers and porous polymer monoliths are set forth.

The Effects of Polymer Carrier, Hot Melt Extrusion Process and Downstream Processing Parameters on the Moisture Sorption Properties of Amorphous Solid Dispersions

PubMed Central

Feng, Xin; Vo, Anh; Patil, Hemlata; Tiwari, Roshan V.; Alshetaili, Abdullah S.; Pimparade, Manjeet B.; Repka, Michael A.

2017-01-01

Objective The aim of this study was to evaluate the effect of polymer carrier, hot melt extrusion (HME) and downstream processing parameters on the water uptake properties of amorphous solid dispersions. Methods Three polymers and a model drug were used to prepare amorphous solid dispersions utilizing HME technology. The sorption-desorption isotherms of solid dispersions and their physical mixtures were measured by the Dynamic Vapor Sorption system, and the effect of polymer hydrophobicity, hygroscopicity, molecular weight and the HME process were investigated. FTIR imaging was performed to understand the phase separation driven by the moisture. Key findings Solid dispersions with polymeric carriers with lower hydrophilicity, hygroscopicity, and higher molecular weight could sorb less moisture under the high RH conditions. The water uptake ability of polymer-drug solid dispersion systems were decreased compared to the physical mixture after HME, which might be due to the decreased surface area and porosity. The FTIR imaging indicated the homogeneity of the drug molecularly dispersed within the polymer matrix was changed after exposure to high RH. Conclusion Understanding the effect of formulation and processing on the moisture sorption properties of solid dispersions is essential for the development of drug products with desired physical and chemical stability. PMID:26589107

Modeling and prediction of relaxation of polar order in high-activity nonlinear optical polymers

NASA Astrophysics Data System (ADS)

Guenthner, Andrew J.; Lindsay, Geoffrey A.; Wright, Michael E.; Fallis, Stephen; Ashley, Paul R.; Sanghadasa, Mohan

2007-09-01

Mach-Zehnder optical modulators were fabricated using the CLD and FTC chromophores in polymer-on-silicon optical waveguides. Up to 17 months of oven-ageing stability are reported for the poled polymer films. Modulators containing an FTC-polyimide had the best over all aging performance. To model and extrapolate the ageing data, a relaxation correlation function attributed to A. K. Jonscher was compared to the well-established stretched exponential correlation function. Both models gave a good fit to the data. The Jonscher model predicted a slower relaxation rate in the out years. Analysis showed that collecting data for a longer period relative to the relaxation time was more important for generating useful predictions than the precision with which individual model parameters could be estimated. Thus from a practical standpoint, time-temperature superposition must be assumed in order to generate meaningful predictions. For this purpose, Arrhenius-type expressions were found to relate the model time constants to the ageing temperatures.

Selective separation of Eu{sup 3+} using polymer-enhanced ultrafiltration

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

Norton, M.V.

1994-03-01

A process to selectively remove {sup 241}Am from liquid radioactive waste was investigated as an actinide separation method applicable to Hanford and other waste sites. The experimental procedures involved removal of Eu, a nonradioactive surrogate for Am, from aqueous solutions at pH 5 using organic polymers in conjunction with ultrafiltration. Commercially available polyacrylic acid (60,000 MW) and Pacific Northwest Laboratory`s (PNL) synthesized E3 copolymer ({approximately}10,000 MW) were tested. Test solutions containing 10 {mu}g/mL of Eu were dosed vath each polymer at various concentrations in order to bind Eu (i.e., by complexation and/or cation exchange) for subsequent rejection by an ultrafiltrationmore » coupon. Test solutions were filtered with and without polymer to determine if enhanced Eu separation could be achieved from polymer treatment. Both polymers significantly increased Eu removal. Optimum concentrations were 20 {mu}g/mL of polyacrylic acid and 100 {mu}g/mL of E3 for 100% Eu rejection by the Amicon PM10 membrane at 55 psi. In addition to enhancement of removal, the polymers selectively bound Eu over Na, suggesting that selective separation of Eu was possible. This suggests that polymer-enhanced ultrafiltration is a potential process for separation of {sup 241}Am from Hanford tank waste, further investigation of binding agents and membranes effective under very alkaline and high ionic strength is warranted. This process also has potential applications for selective separation of toxic metals from industrial process streams.« less

Enabling thermal processing of ritonavir-polyvinyl alcohol amorphous solid dispersions by KinetiSol® Dispersing.

PubMed

LaFountaine, Justin S; Jermain, Scott V; Prasad, Leena Kumari; Brough, Chris; Miller, Dave A; Lubda, Dieter; McGinity, James W; Williams, Robert O

2016-04-01

Polyvinyl alcohol has received little attention as a matrix polymer in amorphous solid dispersions (ASDs) due to its thermal and rheological limitations in extrusion processing and limited organic solubility in spray drying applications. Additionally, in extrusion processing, the high temperatures required to process often exclude thermally labile APIs. The purpose of this study was to evaluate the feasibility of processing polyvinyl alcohol amorphous solid dispersions utilizing the model compound ritonavir with KinetiSol® Dispersing (KSD) technology. The effects of KSD rotor speed and ejection temperature on the physicochemical properties of the processed material were evaluated. Powder X-ray diffraction and modulated differential scanning calorimetry were used to confirm amorphous conversion. Liquid chromatography-mass spectroscopy was used to characterize and identify degradation pathways of ritonavir during KSD processing and (13)C nuclear magnetic resonance spectroscopy was used to investigate polymer stability. An optimal range of processing conditions was found that resulted in amorphous product and minimal to no drug and polymer degradation. Drug release of the ASD produced from the optimal processing conditions was evaluated using a non-sink, pH-shift dissolution test. The ability to process amorphous solid dispersions with polyvinyl alcohol as a matrix polymer will enable further investigations of the polymer's performance in amorphous systems for poorly water-soluble compounds. Copyright © 2016 Elsevier B.V. All rights reserved.

Multilayered composite proton exchange membrane and a process for manufacturing the same

DOEpatents

Santurri, Pasco R; Duvall, James H; Katona, Denise M; Mausar, Joseph T; Decker, Berryinne

2015-05-05

A multilayered membrane for use with fuel cells and related applications. The multilayered membrane includes a carrier film, at least one layer of an undoped conductive polymer electrolyte material applied onto the carrier film, and at least one layer of a conductive polymer electrolyte material applied onto the adjacent layer of polymer electrolyte material. Each layer of conductive polymer electrolyte material is doped with a plurality of nanoparticles. Each layer of undoped electrolyte material and doped electrolyte material may be applied in an alternating configuration, or alternatively, adjacent layers of doped conductive polymer electrolyte material is employed. The process for producing a multilayered composite membrane includes providing a carrier substrate and solution casting a layer of undoped conductive polymer electrolyte material and a layer of conductive polymer electrolyte material doped with nanoparticles in an alternating arrangement or in an arrangement where doped layers are adjacent to one another.

Motors and Their Tethers: The Role of Secondary Binding Sites in Processive Motility

PubMed Central

Kincaid, Margaret M.; King, Stephen J.

2007-01-01

Cytoskeletal motors convert the energy from binding and hydrolyzing ATP into conformational changes that direct movement along a cytoskeletal polymer substrate. These enzymes utilize different mechanisms to generate long-range motion on the order of a micron or more that is required for functions ranging from muscle contraction to transport of growth factors along a nerve axon. Several of the individual cytoskeletal motors are processive, meaning that they have the ability to take sequential steps along their polymer substrate without dissociating from the polymer. This ability to maintain contact with the polymer allows individual motors to move cargos quickly from one cellular location to another. Many of the processive motors have now been found to utilize secondary binding sites that aid in motor processivity. PMID:17172850

Tailoring the physical properties of homopolymers and polymer nanocomposites via solid-state processing

NASA Astrophysics Data System (ADS)

Pierre, Cynthia

Numerous approaches can be used to modify polymer properties. In this thesis, it is demonstrated that an innovative, continuous, industrially scalable process called solid-state shear pulverization (SSSP) can be used to enhance polymer properties with and without the addition of nanofillers. The SSSP process employs a modified twin-screw extruder in which the barrel is cooled rather than heated, resulting in the polymer being processed at a temperature below its glass transition temperature, if the polymer is amorphous, or its melt transition temperature, if the polymer is semi-crystalline. The material processed via SSSP experiences high levels of shear and compressive stresses, resulting in many repeated fragmentation and fusion steps during pulverization, which can lead to mechanochemistry. This research provides the first in-depth study on the effect of SSSP processing on the molecular structure as well as physical properties of homopolymers. Rheological characterization has demonstrated an increase in the melt viscosity of pulverized poly(ethylene terephthalate) (PET), which can be ascribed to the in situ formation of lightly branched PET. Further evidence of branched PET is provided via a dramatic increase in the rate of crystallization of the pulverized samples. These results suggest that SSSP processing can enhance the reuse and recyclability of PET. While SSSP processing has dramatic effects on the structure of polyesters and consequently their properties, a mild effect is observed for polyolefins. This thesis also demonstrates via a combination of methods that the well-exfoliated state can be achieved via SSSP processing of various polymer nanocomposites, using as-received, unmodified fillers. For example, extensive comparisons are made concerning the thermal stability in air or nitrogen atmosphere of polypropylene (PP)/clay, PP/graphite, and PP/carbon nanotube (CNT) nanocomposites made by SSSP. These comparisons suggest that the mechanism by which CNTs enhance the thermal stability of PP differs from the mechanism associated with clay and graphite.

Molecular scale modeling of polymer imprint nanolithography.

PubMed

Chandross, Michael; Grest, Gary S

2012-01-10

We present the results of large-scale molecular dynamics simulations of two different nanolithographic processes, step-flash imprint lithography (SFIL), and hot embossing. We insert rigid stamps into an entangled bead-spring polymer melt above the glass transition temperature. After equilibration, the polymer is then hardened in one of two ways, depending on the specific process to be modeled. For SFIL, we cross-link the polymer chains by introducing bonds between neighboring beads. To model hot embossing, we instead cool the melt to below the glass transition temperature. We then study the ability of these methods to retain features by removing the stamps, both with a zero-stress removal process in which stamp atoms are instantaneously deleted from the system as well as a more physical process in which the stamp is pulled from the hardened polymer at fixed velocity. We find that it is necessary to coat the stamp with an antifriction coating to achieve clean removal of the stamp. We further find that a high density of cross-links is necessary for good feature retention in the SFIL process. The hot embossing process results in good feature retention at all length scales studied as long as coated, low surface energy stamps are used.

Diffusion of residual monomer in polymer resins.

PubMed Central

Piver, W T

1976-01-01

A simplified mathematical model which made use of Fick's laws of diffusion written in spherical coordinates was developed to describe the rate of diffusion of residual monomers from polymer resins. The properties of the monomer-polymer system which influenced the amount of monomer remaining in the polymer as a function of time were the diffusivity and solubility of the monomer in the polymer, and the particle size of the polymer resin. This model was used to analyze literature data on the diffusion of residual vinyl chloride monomer in polyvinyl chloride resins made by the suspension process. It was concluded that particle size of the resin was a significant parameter which should be taken advantage of in process equipment designed to remove residual monomer from PVC resins. The diffusivity of the monomer in the polymer was a function of the solubility of the monomer in the polymer. Monomer solubility can be determined from Henry's law. It was suggested that this model could be adapted to describe diffusion of monomers from any monomer-polymer system, and would be a useful approach to modeling the transport of nonreactive chemical additives from plastics. PMID:1026410

Application of mass spectrometry to process control for polymer material in autoclave curing

NASA Technical Reports Server (NTRS)

Smith, A. C.

1983-01-01

Mass spectrometer analysis of gas samples collected during a cure cycle of polymer materials can be used as a process control technique. This technique is particularly helpful in studying the various types of solvents and resin systems used in the preparation of polymer materials and characterizing the chemical composition of different resin systems and their mechanism of polymerization.

Polyestercarbonates which exhibit improved processibility

DOEpatents

Krabbenhoft, Herman Otto

1999-01-01

The invention relates to a polyestercarbonate polymer which comprises repeating units of a mono-unsaturated aliphatic dicarboxylic acid having about 12 to about 20 carbon atoms. Preferred dicarboxylic acids for incorporation into the polymer are cis-octadec-9-enedioic acid or trans-octadec-9-enedioic acid. The use of these mono-unsaturated acids results in polymers with lower glass transition temperatures, and enhances processibility.

Boron-carbon-silicon polymers and ceramic and a process for the production thereof

NASA Technical Reports Server (NTRS)

Riccitiello, Salvatore (Inventor); Hsu, Ming-Ta (Inventor); Chen, Timothy S. (Inventor)

1992-01-01

The present invention relates to a process for the production of an organoborosilicon preceramic polymer. The polymer is prepared by the reaction of vinylsilane or vinlymethylsilanes (acetylene)silane or acetylene alkyl silanes and borane or borane derivatives. The prepolymer form is pyrolyzed to produce a ceramic article useful in high temperature (e.g., aerospace) or extreme environmental applications.

``Coffee-ring'' patterns of polymer droplets

NASA Astrophysics Data System (ADS)

Biswas, Nupur; Datta, Alokmay

2013-02-01

Dried droplets of polymer solutions carries the self-assembly behavior of polymer molecules by forming various patterns. Pattern formation is a consequence of deposition of molecules depending on motion of the contact line during the drying process. The contact line motion depends on initial polymer concentrations and hence entanglement. Thus depending on entanglement the patterns represent the `particle' like or `collective' behavior of polymer molecules.

Dry particle coating of polymer particles for tailor-made product properties

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

Blümel, C., E-mail: karl-ernst.wirth@fau.de; Schmidt, J., E-mail: karl-ernst.wirth@fau.de; Dielesen, A., E-mail: karl-ernst.wirth@fau.de

2014-05-15

Disperse polymer powders with tailor-made particle properties are of increasing interest in industrial applications such as Selective Laser Beam Melting processes (SLM). This study focuses on dry particle coating processes to improve the conductivity of the insulating polymer powder in order to assemble conductive devices. Therefore PP particles were coated with Carbon Black nanoparticles in a dry particle coating process. This process was investigated in dependence of process time and mass fraction of Carbon Black. The conductivity of the functionalized powders was measured by impedance spectroscopy. It was found that there is a dependence of process time, respectively coating ratiomore » and conductivity. The powder shows higher conductivities with increasing number of guest particles per host particle surface area, i.e. there is a correlation between surface functionalization density and conductivity. The assembled composite particles open new possibilities for processing distinct polymers such as PP in SLM process. The fundamentals of the dry particle coating process of PP host particles with Carbon Black guest particles as well as the influence on the electrical conductivity will be discussed.« less

High Performance Polymers and Composites (HiPPAC) Center

NASA Technical Reports Server (NTRS)

Mintz, Eric A.; Veazie, David

2005-01-01

NASA University Research Centers funding has allowed Clark Atlanta University (CAU) to establish a High Performance Polymers and Composites (HiPPAC) Research Center. Clark Atlanta University, through the HiPPAC Center has consolidated and expanded its polymer and composite research capabilities through the development of research efforts in: (1) Synthesis and characterization of polymeric NLO, photorefractive, and piezoelectric materials; (2) Characterization and engineering applications of induced strain smart materials; (3) Processable polyimides and additives to enhance polyimide processing for composite applications; (4) Fabrication and mechanical characterization of polymer based composites.

A Study on the Properties of Carbon Black Mortar Using Granulated Blast Furnace Slag and Polymer.

PubMed

Jang, Hong-Seok; Jeon, Ui-Hyeon; So, Seung-Young

2015-11-01

White Portland Cement (WPC) and inorganic pigment have been used in colored concrete, but there are some physical problems such as increases in efflorescence, and poor workability and low economics. The aim of this study was to investigate the effects of GBFS and polymer (methyl cellulose) on the physical properties of carbon black mortar. For this purpose, a flow test, compressive strength test and color evaluation and was carried out on cement mortar mixed with polymer by changing the proportion of cement and ratio of GBFS. The results show that the addition of polymer influences significantly the color value efficiency in colored mortar. This is due to the reduction of overall amount of micro pore. This polymer films prevent the transport of soluble calcium towards the surface, and decreases efflorescence. And the flow of colored mortar was increased in proportion to the addition rate of the GBFS. In addition the strength of colored mortars with GBFS at the long-term aged (after 28 days) was higher than that of the general WPC mortar, although its strength was developed slowly at the early ages.

Innovative Additive for Bitumen Based on Processed Fats

NASA Astrophysics Data System (ADS)

Babiak, Michał; Kosno, Jacek; Ratajczak, Maria; Zieliński, Krzysztof

2017-10-01

Various additives, admixtures and modifiers are used to improve technical properties and strength characteristics of building materials. Manufacturers of waterproofing materials, concrete, ceramics and bitumen have to use innovative, increasingly complex and costly additives, admixtures or modifiers. As a result, simple and inexpensive substances have been replaced by complex, long chain polymers, multi component resins or plastics. For economic and ecological reasons waste materials are more frequently used as additives, admixtures and modifiers. Nowadays the most commonly used physical modifiers of bitumen belong to the group of polymers - large molecular organic compounds of natural origin or being the result of planned chemical synthesis. Polymers are substances that do not chemically react with bitumen, they act as fillers or create a spatial network within bitumen (the so called physical cross-linking). The development of organic chemistry has allowed the synthesis of a number of substances chemically modifying bitumen. The most promising are heterocyclic organic compounds belonging to the group of imidazolines. The aim of the study presented in this paper was to demonstrate the suitability of processed natural and post-refining fat waste (diamidoamine dehydrate) as bitumen modifier. This paper discusses the impact of adding technical imidazoline on selected bitumen characteristics. Samples of bitumen 160/220, which is most commonly used for the production of waterproofing products, were analysed. For base bitumen and bitumen modified with technical imidazoline the following measurements were taken: measurement of the softening point by Ball and Ring method, determination of the breaking point by Fraass method and needle penetration measurement at 25°C. Later the samples were aged using TFOT laboratory method and the basic characteristics were determined again. The results showed that a small amount of imidazoline improved bitumen thermoplastic parameters at low temperatures and had a significant impact on weakening bitumen oxidation and ageing. The addition of technical imidazoline prevents bitumen from hardening, thus increasing its flexibility and its resistance to mechanical damage. Due to many difficulties in the production of polymer bitumens and in order to find cheaper, more environment friendly solutions, the authors proposed an ecological bituminous modifier which, due to chemical reaction with binders, creates a stable and firm in time product. Imidazolines have a negative impact on bitumen softening point, which makes them impossible to use as an independent modifier. Therefore, at a later stage of the research, the authors will attempt to create a hybrid bitumen modifier which will combine the beneficial effect of polymers and imidazoline on the characteristics of bituminous binders.

Rotationally Molded Liquid Crystalline Polymers

NASA Technical Reports Server (NTRS)

Rogers, Martin; Scribben, Eric; Baird, Donald; Hulcher, Bruce

2002-01-01

Rotational molding is a unique process for producing hollow plastic parts. Rotational molding offers low cost tooling and can produce very large parts with complicated shapes. Products made by rotational molding include water tanks with capacities up to 20,000 gallons, truck bed liners, playground equipment, air ducts, Nylon fuel tanks, pipes, toys, stretchers, kayaks, pallets, and many others. Thermotropic liquid crystalline polymers are an important class of engineering resins employed in a wide variety of applications. Thermotropic liquid crystalline polymers resins are composed of semirigid, nearly linear polymeric chains resulting in an ordered mesomorphic phase between the crystalline solid and the isotropic liquid. Ordering of the rigid rod-like polymers in the melt phase yields microfibrous, self-reinforcing polymer structures with outstanding mechanical and thermal properties. Rotational molding of liquid crystalline polymer resins results in high strength and high temperature hollow structures useful in a variety of applications. Various fillers and reinforcements can potentially be added to improve properties of the hollow structures. This paper focuses on the process and properties of rotationally molded liquid crystalline polymers. This paper will also highlight the interactions between academia and small businesses in developing new products and processes.

Development of polysilsesquioxane composites

NASA Technical Reports Server (NTRS)

Srinivasan, K.; Tiwari, S. N.

1990-01-01

Polymer composites are increasingly being required to operate for prolonged durations at higher temperatures than in the past. Hence there have been increased efforts devoted to synthesizing and characterizing polymers capable of withstanding temperatures greater than 300 C for long periods. Several such organic polymers have been investigated in recent times. This research effort seeks to enquire if inorganic polymers can be utilized to provide the same result. Ceramics have long been recognized as providing superior thermal properties for demanding applications. However, the extremely high softening temperatures preclude their being shaped into complex shapes through melt processing techniques common to organic polymers. One approach towards solving this problem has been through the development of preceramic polymers. These are capable of being processed in the polymeric state with ease, and subsequently being pyrolyzed to ceramic structures. This experimental study is aimed at studying the feasibility of using preceramic polymers (that have not been subject to the pyrolysis step) as high performance composite matrices for high temperature applications. A preliminary study of this nature is not geared towards optimizing mechanical properties suitable for such composites. Rather, this study attempts to process such resins in composite form and suitably characterize their properties.

A Course in Polymer Processing.

ERIC Educational Resources Information Center

Soong, David S.

1981-01-01

Following a brief introduction to the origin and nature of a course in polymer rheology and melt processing, discusses course objectives, detailed content, teaching strategies, and observations/experiences from its first offering. (SK)

Surface energy characteristics of zeolite embedded PVDF nanofiber films with electrospinning process

NASA Astrophysics Data System (ADS)

Kang, Dong Hee; Kang, Hyun Wook

2016-11-01

Electrospinning is a nano-scale fiber production method with various polymer materials. This technique allows simple fiber diameters control by changing the physical conditions such as applied voltage and polymer solution viscosity during the fabrication process. The electrospun polymer fibers form a thin porous film with high surface area to volume ratio. Due to these unique characteristics, it is widely used for many application fields such as photocatalyst, electric sensor, and antibacterial scaffold for tissue engineering. Filtration is one of the main applications of electrospun polymer fibers for specific application of filtering out dust particles and dehumidification. Most polymers which are commonly used in electrospinning are hard to perform the filtering and dehumidification simultaneously because of their low hygroscopic property. To overcome this obstacle, the desiccant polymers are developed such as polyacrylic acid and polysulfobetaine methacrylate. However, the desiccant polymers are generally expensive and need special solvent for electrospinning. An alternating way to solve these problems is mixing desiccant material like zeolite in polymer solution during an electrospinning process. In this study, the free surface energy characteristics of electrospun polyvinylidene fluoride (PVDF) film with various zeolite concentrations are investigated to control the hygroscopic property of general polymers. Fundamental physical property of wettability with PVDF shows hydrophobicity. The electrospun PVDF film with small weight ratio with higher than 0.1% of zeolite powder shows diminished contact angles that certifying the wettability of PVDF can be controlled using desiccant material in electrospinning process. To quantify the surface energy of electrospun PVDF films, sessile water droplets are introduced on the electrospun PVDF film surface and the contact angles are measured. The contact angles of PVDF film are 140° for without zeolite and 80° for with 5 wt% of zeolite respectively. As a result, the surface energy of PVDF film can be controlled by embedding zeolite particles in electrospinning process and applied to filtration application of dust filtering and dehumidification simultaneously with low manufacturing cost.

Reactive processing and mechanical properties of polymer derived silicon nitride matrix composites and their use in coating and joining ceramics and ceramic matrix composites

NASA Astrophysics Data System (ADS)

Stackpoole, Margaret Mary

Use of preceramic polymers offers many advantages over conventional ceramic processing routes. Advantages include being able to plastically form the part, form a pyrolized ceramic material at lower temperatures and form high purity microstructures which are tailorable depending on property requirements. To date preceramic polymers are mostly utilized in the production of low dimensional products such as fibers since loss of volatiles during pyrolysis leads to porosity and large shrinkage (in excess of 30%). These problems have been partially solved by use of active fillers (e.g. Ti, Cr, B). The reactive filler converts to a ceramic material with a volume expansion and this increases the density and reduces shrinkage and porosity. The expansion of the reactive filler thus compensates for the polymer shrinkage if the appropriate volume fraction of filler is present in a reactive atmosphere (e.g. N2 or NH3). This approach has resulted in structural composites with limited success. The present research investigates the possibility of using filled preceramic polymers to form net shaped ceramic composite materials and to investigate the use of these unique composite materials to join and coat ceramics and ceramic composites. The initial research focused on phase and microstructural development of bulk composites from the filled polymer/ceramic systems. A processing technique was developed to insure consistency between different samples and the most promising filler/polymer choices for this application have been determined. The processing temperatures and atmospheres have also been optimized. The work covers processing and characterization of bulk composites, joints and coatings. With careful control of processing near net shape bulk composites were fabricated. Both ambient and high temperature strength and fracture toughness was obtained for these composite systems. The potential of using reactively filled preceramic polymers to process joints and coatings was also investigated. A critical thickness below which crack free joints/coatings could be processed was determined. Finally, mechanical properties of the joints and coatings at ambient and elevated temperatures (including oxidation studies) have been evaluated. The interfacial fracture behavior of the joints and coatings was also evaluated.

Development of critical molecular weight-property specifications for high performance polymers used as adhesives and composites

NASA Technical Reports Server (NTRS)

Kranbuehl, D. E.

1982-01-01

The polyimide resin, LARC-160, was prepared from diethyl-3, 3', 4,4'-benzophenone tetracarboxylate, ethyl-5-norbornene-2,3-dicarboxylate and Jeffamine AP-22. The imidization reactions of NE and BTDE were studied by HPLC, C-13-NMR and IR. NE imidizes slowly at 12 C; BTDE imidizes when the resin is heated above 100 C. Both imidization reactions proceed directly to the imide. Neither amic acid is present in significant quantities at any stage of the imidization reactions. The monomer mixture was stored at 12 C for periods up to 14 months. The effects of resin aging at this temperature on the chemical composition of the resin monomer mixture and the imidized polymer formed on curing were investigated. Aging the resin monomer mixture has the effect of partially advancing the imidization reaction. The average size of the cured polymer increases slightly with resin age.

Modelization of three-layered polymer coated steel-strip ironing process using a neural network

NASA Astrophysics Data System (ADS)

Sellés, M. A.; Schmid, S. R.; Sánchez-Caballero, S.; Seguí, V. J.; Reig, M. J.; Pla, R.

2012-04-01

An alternative to the traditional can manufacturing process is to use plastic laminated rolled steels as base stocks. This material consist of pre-heated steel coils that are sandwiched between one or two sheets of polymer. The heated sheets are then immediately quenched, which yields a strong bond between the layers. Such polymer-coated steels were investigated by Jaworski [1,2] and Sellés [3], and found to be suitable for ironing with carefully controlled conditions. A novel multi-layer polymer coated steel has been developed for container applications. This material presents an interesting extension to previous research on polymer laminated steel in ironing, and offers several advantages over the previous material (Sellés [3]). This document shows a modelization for the ironing process (the most crucial step in can manufacturing) done by using a neural network

Investigation of the Bitumen Modification Process Regime Parameters Influence on Polymer-Bitumen Bonding Qualitative Indicators

NASA Astrophysics Data System (ADS)

Belyaev, P. S.; Mishchenko, S. V.; Belyaev, V. P.; Belousov, O. A.; Frolov, V. A.

2018-04-01

The objects of this study are petroleum road bitumen and polymeric bituminous binder for road surfaces obtained by polymer materials. The subject of the study is monitoring the polymer-bitumen binder quality changes as a result of varying the bitumen modification process. The purpose of the work is to identify the patterns of the modification process and build a mathematical model that provides the ability to calculate and select technological equipment. It is shown that the polymer-bitumen binder production with specified quality parameters can be ensured in apparatuses with agitators in turbulent mode without the colloidal mills use. Bitumen mix and modifying additives limiting indicators which can be used as restrictions in the form of mathematical model inequalities are defined. A mathematical model for the polymer-bitumen binder preparation has been developed and its adequacy has been confirmed.

Characterization of polymer composites during autoclave manufacturing by Fourier transform Raman spectroscopy

NASA Astrophysics Data System (ADS)

Farquharson, Stuart; Smith, Wayne W.; Rigas, Elias J.; Granville, Dana

2001-02-01

12 The superior engineering properties of fiber reinforced polymer matrix composites, primarily the high strength-to- weight ratio, make them suitable to applications ranging from sporting goods to aircraft components (e.g. helicopter blades). Unfortunately, consistent fabrication of components with desired mechanical properties has proven difficult, and has led to high production costs. This is largely due to the inability to monitor and control polymer cure, loosely defined as the process of polymer chain extension and cross- linking. Even with stringent process control, slight variations in the pre-polymer formulations (e.g. prepreg) can influence reaction rates, reaction mechanisms, and ultimately, product properties. In an effort to optimize the performance of thermoset composite, we have integrated fiber optic probes between the plies of laminates and monitored cure by Raman spectroscopy, with the eventual goal of process control. Here we present real-time measurements of two high performance aerospace companies cured within an industrial autoclave.

Characterization of Solid Polymers, Ceramic Gap Filler, and Closed-Cell Polymer Foam Using Low-Load Test Methods

NASA Technical Reports Server (NTRS)

Herring, Helen M.

2008-01-01

Various solid polymers, polymer-based composites, and closed-cell polymer foam are being characterized to determine their mechanical properties, using low-load test methods. The residual mechanical properties of these materials after environmental exposure or extreme usage conditions determines their value in aerospace structural applications. In this experimental study, four separate polymers were evaluated to measure their individual mechanical responses after thermal aging and moisture exposure by dynamic mechanical analysis. A ceramic gap filler, used in the gaps between the tiles on the Space Shuttle, was also tested, using dynamic mechanical analysis to determine material property limits during flight. Closed-cell polymer foam, used for the Space Shuttle External Tank insulation, was tested under low load levels to evaluate how the foam's mechanical properties are affected by various loading and unloading scenarios.

Durability of switchable QR code carriers under hydrolytic and photolytic conditions

NASA Astrophysics Data System (ADS)

Ecker, Melanie; Pretsch, Thorsten

2013-09-01

Following a guest diffusion approach, the surface of a shape memory poly(ester urethane) (PEU) was either black or blue colored. Bowtie-shaped quick response (QR) code carriers were then obtained from laser engraving and cutting, before thermo-mechanical functionalization (programming) was applied to stabilize the PEU in a thermo-responsive (switchable) state. The stability of the dye within the polymer surface and long-term functionality of the polymer were investigated against UVA and hydrolytic ageing. Spectrophotometric investigations verified UVA ageing-related color shifts from black to yellow-brownish and blue to petrol-greenish whereas hydrolytically aged samples changed from black to greenish and blue to light blue. In the case of UVA ageing, color changes were accompanied by dye decolorization, whereas hydrolytic ageing led to contrast declines due to dye diffusion. The Michelson contrast could be identified as an effective tool to follow ageing-related contrast changes between surface-dyed and laser-ablated (undyed) polymer regions. As soon as the Michelson contrast fell below a crucial value of 0.1 due to ageing, the QR code was no longer decipherable with a scanning device. Remarkably, the PEU information carrier base material could even then be adequately fixed and recovered. Hence, the surface contrast turned out to be the decisive parameter for QR code carrier applicability.

The effects of polymers' visco-elastoplastic properties on the micro cavities filling step of hot embossing process

NASA Astrophysics Data System (ADS)

Cheng, Gang; Barrière, Thierry

2018-05-01

The hot embossing process has been widely used in the manufacturing of polymer components, especially for the fabrication of micro or nano components. The significant advantage of the hot embossing process compared to the traditional injection moulding process is the excellent effective filling ratio for the high aspect ratio components and large surface structural components. The lack of material behavior modeling and numerical simulation limits the further development the hot embossing process, especially at the micro and nano scales. In this paper, a visco-elastoplastic behavior law has been proposed to describe the amorphous thermoplastic polymer mechanical properties in the hot embossing processing temperature range, which is lightly above their glass transition temperature. Uniaxial compression tests have been carried out in order to investigate the amorphous thermoplastic polymers properties. The material parameters in the visco-elastoplastic model have been identified according to the experimental results. A 3D numerical model has been created in the simulation software, which is based on the finite element method. The numerical simulation of the filling step of the hot embossing process has been effectuated by taking into account the viscous, elastic and plastic behaviors of thermoplastic polymers. The micro hot embossing process has been carried out using horizontal injection compression moulding equipment. A complete compression mould tool, equipped with the heating system, the cooling system, the ejection system and the vacuum system, has been designed and elaborated for this research work. The microfluidic devices based on the amorphous thermoplastic polymers have been successfully elaborated by hot embossing process. Proper agreement between the numerical simulation and the experimental elaboration has been obtained.

New Polymers: Beautiful Structures, But How Can We Bring Them to the Market?

PubMed

Voit, Brigitte

2017-03-06

"… Nobody in our academic polymer community doubts that polymers are the materials of the 21st century, and will continue to enable and drive the development of future technologies, and ensure our high standard of living and wellbeing in the context of both an aging population and the energy transformation. However, we should be aware that there is a difference between polymers and plastics …" Read more about this perspective in the Guest Editorial by Brigitte Voit. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Inorganic nanostructure-organic polymer heterostructures useful for thermoelectric devices

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

See, Kevin C.; Urban, Jeffrey J.; Segalman, Rachel A.

The present invention provides for an inorganic nanostructure-organic polymer heterostructure, useful as a thermoelectric composite material, comprising (a) an inorganic nanostructure, and (b) an electrically conductive organic polymer disposed on the inorganic nanostructure. Both the inorganic nanostructure and the electrically conductive organic polymer are solution-processable.

Atomizing apparatus for making polymer and metal powders and whiskers

DOEpatents

Otaigbe, Joshua U.; McAvoy, Jon M.; Anderson, Iver E.; Ting, Jason; Mi, Jia; Terpstra, Robert

2003-03-18

Method for making polymer particulates, such as spherical powder and whiskers, by melting a polymer material under conditions to avoid thermal degradation of the polymer material, atomizing the melt using gas jet means in a manner to form atomized droplets, and cooling the droplets to form polymer particulates, which are collected for further processing. Atomization parameters can be controlled to produce polymer particulates with controlled particle shape, particle size, and particle size distribution. For example, atomization parameters can be controlled to produce spherical polymer powders, polymer whiskers, and combinations of spherical powders and whiskers. Atomizing apparatus also is provided for atoomizing polymer and metallic materials.

Effects of Prior Aging at 260 deg C in Argon on Inelastic Deformation Behavior of PMR-15 Polymer at 260 deg C: Experiment and Modeling

DTIC Science & Technology

2010-03-01

thermosets [9]. Elastomers have the ability to stretch to several times their original length and return to their original state [14]. Rubber is a classic...without loss of its properties [12]. Thermoplastics have significant toughness and temperature resistance, but are not as good as thermosets in...overall composite performance [12]. Thermosets are much less able to deform once processed. Thermosets are “polymeric materials that in their final

Long-term aging of Ag/a-C:H:O nanocomposite coatings in air and in aqueous environment

NASA Astrophysics Data System (ADS)

Drábik, Martin; Pešička, Josef; Biederman, Hynek; Hegemann, Dirk

2015-04-01

Nanocomposite coatings of silver particles embedded in a plasma polymer matrix possess interesting properties depending on their microstructure. The film microstructure is affected among others also by the RF power supplied during the deposition, as shown by transmission electron microscopy. The optical properties are characterized by UV-vis-NIR spectroscopy. An anomalous optical absorption peak from the Ag nanoparticles is observed and related to the microstructure of the nanocomposite films. Furthermore, a long-term aging of the coatings is studied in-depth in ambient air and in aqueous environments. It is shown that the studied films are not entirely stable. The deposition conditions and the microstructure of the films affect the processes taking place during their aging in both environments.

Investigation of polymer derived ceramics cantilevers for application of high speed atomic force microscopy

NASA Astrophysics Data System (ADS)

Wu, Chia-Yun

High speed Atomic Force Microscopy (AFM) has a wide variety of applications ranging from nanomanufacturing to biophysics. In order to have higher scanning speed of certain AFM modes, high resonant frequency cantilevers are needed; therefore, the goal of this research is to investigate using polymer derived ceramics for possible applications in making high resonant frequency AFM cantilevers using complex cross sections. The polymer derived ceramic that will be studied, is silicon carbide. Polymer derived ceramics offer a potentially more economic fabrication approach for MEMS due to their relatively low processing temperatures and ease of complex shape design. Photolithography was used to make the desired cantilever shapes with micron scale size followed by a wet etching process to release the cantilevers from the substrates. The whole manufacturing process we use borrow well-developed techniques from the semiconducting industry, and as such this project also could offer the opportunity to reduce the fabrication cost of AFM cantilevers and MEMS in general. The characteristics of silicon carbide made from the precursor polymer, SMP-10 (Starfire Systems), were studied. In order to produce high qualities of silicon carbide cantilevers, where the major concern is defects, proper process parameters needed to be determined. Films of polymer derived ceramics often have defects due to shrinkage during the conversion process. Thus control of defects was a central issue in this study. A second, related concern was preventing oxidation; the polymer derived ceramics we chose is easily oxidized during processing. Establishing an environment without oxygen in the whole process was a significant challenge in the project. The optimization of the parameters for using photolithography and wet etching process was the final and central goal of the project; well established techniques used in microfabrication were modified for use in making the cantilever in the project. The techniques developed here open a path to the fabrication of cantilevers with unconventional cross sections.

System Applies Polymer Powder To Filament Tow

NASA Technical Reports Server (NTRS)

Baucom, Robert M.; Snoha, John J.; Marchello, Joseph M.

1993-01-01

Polymer powder applied uniformly and in continuous manner. Powder-coating system applies dry polymer powder to continuous fiber tow. Unique filament-spreading technique, combined with precise control of tension on fibers in system, ensures uniform application of polymer powder to web of spread filaments. Fiber tows impregnated with dry polymer powders ("towpregs") produced for preform-weaving and composite-material-molding applications. System and process valuable to prepreg industry, for production of flexible filament-windable tows and high-temperature polymer prepregs.

Organometallic Polymeric Conductors

NASA Technical Reports Server (NTRS)

Youngs, Wiley J.

1997-01-01

For aerospace applications, the use of polymers can result in tremendous weight savings over metals. Suitable polymeric materials for some applications like EMI shielding, spacecraft grounding, and charge dissipation must combine high electrical conductivity with long-term environmental stability, good processability, and good mechanical properties. Recently, other investigators have reported hybrid films made from an electrically conductive polymer combined with insulating polymers. In all of these instances, the films were prepared by infiltrating an insulating polymer with a precursor for a conductive polymer (either polypyrrole or polythiophene), and oxidatively polymerizing the precursor in situ. The resulting composite films have good electrical conductivity, while overcoming the brittleness inherent in most conductive polymers. Many aerospace applications require a combination of properties. Thus, hybrid films made from polyimides or other engineering resins are of primary interest, but only if conductivities on the same order as those obtained with a polystyrene base could be obtained. Hence, a series of experiments was performed to optimize the conductivity of polyimide-based composite films. The polyimide base chosen for this study was Kapton. 3-MethylThiophene (3MT) was used for the conductive phase. Three processing variables were identified for producing these composite films, namely time, temperature, and oxidant concentration for the in situ oxidation. Statistically designed experiments were used to examine the effects of these variables and synergistic/interactive effects among variables on the electrical conductivity and mechanical strength of the films. Multiple linear regression analysis of the tensile data revealed that temperature and time have the greatest effect on maximum stress. The response surface of maximum stress vs. temperature and time (for oxidant concentration at 1.2 M) is shown. Conductivity of the composite films was measured for over 150 days in air at ambient temperature. The conductivity of the films dropped only half an order of magnitude in that time. Films aged under vacuum at ambient temperature diminished slightly in conductivity in the first day, but did not change thereafter. An experimental design approach will be applied to maximize the efficiency of the laboratory effort. The material properties (initial and long term) will also be monitored and assessed. The experimental results will add to the existing database for electrically conductive polymer materials. Attachments: 1) Synthesis Crystal Structure, and Polymerization of 1,2:5,6:9,10-Tribenzo-3,7,11,13-tetradehydro(14) annulene. 2) Reinvestigation of the Photocyclization of 1,4-Phenylene Bis(phenylmaleic anhydride): Preparation and Structure of (5)Helicene 5,6:9,10-Dianhydride. 3) Preparation and Structure Charecterization of a Platinum Catecholate Complex Containing Two 3-Ethynyltheophone Groups. and 4) Rigid-Rod Polymers Based on Noncoplanar 4,4'-Biphenyldiamines: A Review of Polymer Properties vs Configuration of Diamines.

Preparation and characterization of fusion processed solid dispersions containing a viscous thermally labile polymeric carrier.

PubMed

Hughey, Justin R; Keen, Justin M; Miller, Dave A; Brough, Chris; McGinity, James W

2012-11-15

The primary aim of the present study was to investigate the ability of hydroxypropyl and methoxyl substituted cellulose ethers to stabilize supersaturated concentrations of itraconazole (ITZ), a poorly water-soluble weak base, after an acid-to-neutral pH transition. A secondary aim of the study was to evaluate the effect of fusion processes on polymer stability and molecular weight. Polymer screening studies showed that stabilization of ITZ supersaturation was related to the molecular weight of the polymer and levels of hydroxypropyl and methoxyl substitution. METHOCEL E50LV (E50LV), which is characterized as having a high melt viscosity, was selected for solid dispersion formulation studies. Hot-melt extrusion processing of E50LV based compositions resulted in high torque loads, low material throughput and polymer degradation. KinetiSol Dispersing, a novel fusion based processing technique, was evaluated as a method to prepare the solid dispersions with reduced levels of polymer degradation. An experimental design revealed that polymer molecular weight was sensitive to shearing forces and high temperatures. However, optimal processing conditions resulted in significantly reduced E50LV degradation relative to HME processing. The technique was effectively utilized to prepare homogenous solid solutions of E50LV and ITZ, characterized as having a single glass transition temperature over a wide range of drug loadings. All prepared compositions provided for a high degree of ITZ supersaturation stabilization. Copyright © 2012 Elsevier B.V. All rights reserved.

Microstructure of Pharmaceutical Semicrystalline Dispersions: The Significance of Polymer Conformation.

PubMed

Van Duong, Tu; Goderis, Bart; Van Humbeeck, Jan; Van den Mooter, Guy

2018-02-05

The microstructure of pharmaceutical semicrystalline solid dispersions has attracted extensive attention due to its complexity that might result in the diversity in physical stability, dissolution behavior, and pharmaceutical performance of the systems. Numerous factors have been reported that dictate the microstructure of semicrystalline dispersions. Nevertheless, the importance of the complicated conformation of the polymer has never been elucidated. In this study, we investigate the microstructure of dispersions of polyethylene glycol and active pharmaceutical ingredients by small-angle X-ray scattering and high performance differential scanning calorimetry. Polyethylene glycol with molecular weight of 2000 g/mol (PEG2000) and 6000 g/mol (PEG6000) exhibited remarkable discrepancy in the lamellar periodicity in dispersions with APIs which was attributed to the differences in their folding behavior. The long period of PEG2000 always decreased upon aging-induced exclusion of APIs from the interlamellar region of extended chain crystals whereas the periodicity of PEG6000 may decrease or increase during storage as a consequence of the competition between the drug segregation and the lamellar thickening from nonintegral-folded into integral-folded chain crystals. These processes were in turn significantly influenced by the crystallization tendency of the pharmaceutical compounds, drug-polymer interactions, as well as the dispersion composition and crystallization temperature. This study highlights the significance of the polymer conformation on the microstructure of semicrystalline systems that is critical for the preparation of solid dispersions with consistent and reproducible quality.

Process for hardening the surface of polymers

DOEpatents

Mansur, Louis K.; Lee, Eal H.

1992-01-01

Hard surfaced polymers and the method for making them is generally described. Polymers are subjected to simultaneous multiple ion beam bombardment, that results in a hardening of the surface and improved wear resistance.

Polymer/riblet combination for hydrodynamic skin friction reduction

NASA Technical Reports Server (NTRS)

Reed, Jason C. (Inventor); Bushnell, Dennis M. (Inventor)

1995-01-01

A process is disclosed for reducing skin friction and inhibiting the effects of liquid turbulence in a system involving the flow of a liquid along the surface of a body, e.g. a marine vehicle. This process includes injecting a drag reducing polymer into the valleys of adjacent, evenly spaced, longitudinal grooves extending along the length of the surface of the body, so that the rate of diffusion of the polymer from individual grooves into the liquid flow is predictably controlled by the groove dimensions. When the polymer has diffused over the tips of the grooves into the near wall region of the boundary layer, the polymer effectively reduces the turbulent skin friction. A substantial drag reducing effect is achieved with less polymer than must be used to lower skin friction when the surface of the body is smooth.

Polymer/riblet combination for hydrodynamic skin friction reduction

NASA Technical Reports Server (NTRS)

Bushnell, Dennis M. (Inventor); Reed, Jason C. (Inventor)

1990-01-01

A process is disclosed for reducing skin friction and inhibiting the effects of liquid turbulence in a system involving the flow of a liquid along the surface of a body, e.g., a marine vehicle. This process includes injecting a drag reducing polymer into the valleys of adjacent, evenly spaced, longitudinal grooves extending along the length of the surface of the body, so that the rate of diffusion of the polymer from individual grooves into the liquid flow is predictably controlled by the groove dimensions. When the polymer has diffused over the tips of the grooves into the near wall region of the boundary layer, the polymer effectively reduces the turbulent skin friction. A substantial drag reducing effect is achieved with less polymer than must be used to lower skin friction when the surface of the body is smooth.

Thermal Spray Formation of Polymer Coatings

NASA Technical Reports Server (NTRS)

Coquill, Scott; Galbraith, Stephen L.; Tuss. Darren L.; Ivosevic, Milan

2008-01-01

This innovation forms a sprayable polymer film using powdered precursor materials and an in-process heating method. This device directly applies a powdered polymer onto a substrate to form an adherent, mechanically-sound, and thickness-regulated film. The process can be used to lay down both fully dense and porous, e.g., foam, coatings. This system is field-deployable and includes power distribution, heater controls, polymer constituent material bins, flow controls, material transportation functions, and a thermal spray apparatus. The only thing required for operation in the field is a power source. Because this method does not require solvents, it does not release the toxic, volatile organic compounds of previous methods. Also, the sprayed polymer material is not degraded because this method does not use hot combustion gas or hot plasma gas. This keeps the polymer from becoming rough, porous, or poorly bonded.

Convective polymer assembly for the deposition of nanostructures and polymer thin films on immobilized particles.

PubMed

Richardson, Joseph J; Björnmalm, Mattias; Gunawan, Sylvia T; Guo, Junling; Liang, Kang; Tardy, Blaise; Sekiguchi, Shota; Noi, Ka Fung; Cui, Jiwei; Ejima, Hirotaka; Caruso, Frank

2014-11-21

We report the preparation of polymer particles via convective polymer assembly (CPA). Convection is used to move polymer solutions and cargo through an agarose gel that contains immobilized template particles. This method both coats and washes the particles in a process that is amenable to automation, and does not depend on passive diffusion or electrical currents, thus facilitating incorporation of fragile and nanoscale objects, such as liposomes and gold nanoparticles, into the thin polymer films. Template dissolution leads to the formation of stable polymer particles and capsules.

The effects of polymer carrier, hot melt extrusion process and downstream processing parameters on the moisture sorption properties of amorphous solid dispersions.

PubMed

Feng, Xin; Vo, Anh; Patil, Hemlata; Tiwari, Roshan V; Alshetaili, Abdullah S; Pimparade, Manjeet B; Repka, Michael A

2016-05-01

The aim of this study was to evaluate the effect of polymer carrier, hot melt extrusion and downstream processing parameters on the water uptake properties of amorphous solid dispersions. Three polymers and a model drug were used to prepare amorphous solid dispersions utilizing the hot melt extrusion technology. The sorption-desorption isotherms of solid dispersions and their physical mixtures were measured by the dynamic vapour sorption system, and the effects of polymer hydrophobicity, hygroscopicity, molecular weight and the hot melt extrusion process were investigated. Fourier transform infrared (FTIR) imaging was performed to understand the phase separation driven by the moisture. Solid dispersions with polymeric carriers with lower hydrophilicity, hygroscopicity and higher molecular weight could sorb less moisture under the high relative humidity (RH) conditions. The water uptake ability of polymer-drug solid dispersion systems were decreased compared with the physical mixture after hot melt extrusion, which might be due to the decreased surface area and porosity. The FTIR imaging indicated that the homogeneity of the drug molecularly dispersed within the polymer matrix was changed after exposure to high RH. Understanding the effect of formulation and processing on the moisture sorption properties of solid dispersions is essential for the development of drug products with desired physical and chemical stability. © 2015 Royal Pharmaceutical Society.

Synthesis and Characterization of Composite Membranes made of Graphene and Polymers of Intrinsic Microporosity

DTIC Science & Technology

2016-02-16

group of polymers with molecular sieve behaviour due to their rigid, contorted macromolecular backbones. They show great potential in organophilic...ageing is expected by adding graphene as a nanofiller. Little is experimentally known about how the material disperses in the polymer. Here we used Raman...effective understanding of the structure-property relationships of the composite. Obtaining such structural infor- mation, however, is experimentally

Investigation of the use of recycled polymer-modified asphalt in asphaltic concrete pavements.

DOT National Transportation Integrated Search

2004-06-30

This report presents issues associated with recycling polymer modified asphalt cements (PMACs), particularly blending aged PMAC with new PMAC. A styrene-butadiene-styrene (SBS) PMAC was selected and graded using the Superpave Performance Grading (PG)...

Highly accelerated lifetime for externally applied bond critical fiber-reinforced polymer (FRP) infrastructure materials.

DOT National Transportation Integrated Search

2014-03-01

This report describes a research project to investigate accelerated aging protocols for fiber-reinforced : polymer (FRP) reinforcement of concrete. This research was conducted in three stages. In the first : stage, various spectroscopic techniques we...

Characterizing Residuals in New and Aged Fluorotelomer Polymers in Soil

EPA Science Inventory

Fluorotelomer polymers (FTPs) comprise some of the major products of the fluorotelomer industry. FTPs impart anti-wetting and anti-staining properties which are invaluable to wide range of consumer products including clothing, upholstery, food packaging, and carpeting. FTPs retai...

Composite membranes, methods of making same, and applications of same

DOEpatents

Pintauro, Peter N.; Park, Andrew; Ballengee, Jason

2016-05-24

In one aspect of the present invention, a method of fabricating a composite membrane includes: forming a first polymer solution from a first polymer and a second polymer solution from a second polymer, respectively, where the first polymer includes a charged polymer and the second polymer includes an uncharged polymer; electrospinning, separately and simultaneously, the first and second polymer solutions to form a dual fiber mat with first polymer fibers and second polymer fibers; and processing the dual fiber mat by softening and flowing one of the first or second polymer fibers to fill in the void space between the other of the first and second polymer fibers so as to form the composite membrane. In some embodiments, the composite membrane may be a proton exchange membrane (PEM) or an anion exchange membrane (AEM).

Lower Critical Solubility Temperature Behavior in Membranes Formed from a 2-(2-Methoxyethoxy)ethoxy-Containing Polyphosphazene

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

Stewart, F.F.; Lash, R.P.

A phosphazene polymer with three pendant groups was synthesized and characterized as a membrane material. Substitution of the phosphazene with 64% 2-(2-methoxyethoxy)ethanol (MEE), 27% 4-methoxyphenol, and 9% 2-allyphenol yielded a hydrophilic elastomer with considerable flow at room temperature. Solution behavior showed significant aging effects where, using fresh solutions, membranes could not cast on porous ceramic supports (0.2-micron pore size) without significant polymer penetration into the pores. Solutions aged for two weeks were found to readily penetrate into the pores of the ceramic support. Analysis of fresh and aged solutions by laser light scattering showed significant loss in molecular weight withmore » time. Pervaporation of water-dye solutions using dimensionally stabilized membranes revealed in inverse correlation between flux and temperature, suggesting thermally induced morphological changes within the polymer. This polymer was found to exhibit, in the bulk state, lower critical solubility temperature (LCST) behavior where the material becomes less hydrophilic with increasing temperature. LCST behavior was probed thermally and gravimetrically and has been attributed to the anomalous pervaporation results. The degree to which LCST effects membrane transport was influenced by changes in the crosslink density and permeate side pressure.« less

Effects of processing on the release profiles of matrix systems containing 5-aminosalicylic acid.

PubMed

Korbely, Anita; Kelemen, András; Kása, Péter; Pintye-Hódi, Klára

2012-12-01

The aim of this study was to investigate the influence of different processing methods on the profiles of 5-aminosalicylic acid dissolution from controlled-release matrix systems based on Eudragit® RL and Eudragit® RS water-insoluble polymers. The pure polymers and their mixtures were studied as matrix formers using different processing methods, i.e., direct compression, wet granulation of the active ingredient with the addition of polymer(s) to the external phase, wet granulation with water, and wet granulation with aqueous dispersions. In comparison with the directly compressed tablets, tablets made by wet granulation with water demonstrated a 6-19% increase in final drug dissolution, whereas when polymers were applied in the external phase during compression, a 0-13% decrease was observed in the amount of drug released. Wet granulation with aqueous polymer dispersions delayed the release of the drug; this was especially marked (a 54-56% decrease in drug release) in compositions, which contained a high amount of Eudragit RL 30D. The release profiles were mostly described by the Korsmeyer-Peppas model or the Hopfenberg model.

Microstructural aspects in steel fiber reinforced acrylic emulsion polymer modified concrete

NASA Astrophysics Data System (ADS)

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

2018-03-01

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

Nucleation, Growth, and Alignment of Poly(3-hexylthiophene) Nanofibers for High-Performance OFETs.

PubMed

Persson, Nils E; Chu, Ping-Hsun; McBride, Michael; Grover, Martha; Reichmanis, Elsa

2017-04-18

Conjugated semiconducting polymers have been the subject of intense study for over two decades with promising advances toward a printable electronics manufacturing ecosystem. These materials will deliver functional electronic devices that are lightweight, flexible, large-area, and cost-effective, with applications ranging from biomedical sensors to solar cells. Synthesis of novel molecules has led to significant improvements in charge carrier mobility, a defining electrical performance metric for many applications. However, the solution processing and thin film deposition of conjugated polymers must also be properly controlled to obtain reproducible device performance. This has led to an abundance of research on the process-structure-property relationships governing the microstructural evolution of the model semicrystalline poly(3-hexylthiophene) (P3HT) as applied to organic field effect transistor (OFET) fabrication. What followed was the production of an expansive body of work on the crystallization, self-assembly, and charge transport behavior of this semiflexible polymer whose strong π-π stacking interactions allow for highly creative methods of structural control, including the modulation of solvent and solution properties, flow-induced crystallization and alignment techniques, structural templating, and solid-state thermal and mechanical processing. This Account relates recent progress in the microstructural control of P3HT thin films through the nucleation, growth, and alignment of P3HT nanofibers. Solution-based nanofiber formation allows one to develop structural order prior to thin film deposition, mitigating the need for intricate deposition processes and enabling the use of batch and continuous chemical processing steps. Fiber growth is framed as a traditional crystallization problem, with the balance between nucleation and growth rates determining the fiber size and ultimately the distribution of grain boundaries in the solid state. Control of nucleation can be accomplished through a sonication-based seeding procedure, while growth can be modulated through supersaturation control via the tuning of solvent quality, the use of UV irradiation or through aging. These principles carry over to the flow-induced growth of P3HT nanofibers in a continuous microfluidic processing system, leading to thin films with significantly enhanced mobility. Further gains can be made by promoting long-range polymer chain alignment, achieved by depositing nanofibers through shear-based coating methods that promote high fiber packing density and alignment. All of these developments in processing were carried out on a standard OFET platform, enabling us to generalize quantitative structure-property relationships from structural data sources such as UV-vis, AFM, and GIWAXS. It is shown that a linear correlation exists between mobility and the in-plane orientational order of nanofibers, as extracted from AFM images using advanced computer vision software developed by our group. Herein, we discuss data-driven approaches to the determination of process-structure-property relationships, as well as the transferability of structural control strategies for P3HT to other conjugated polymer systems and applications.

High-Performance Polymers Having Low Melt Viscosities

NASA Technical Reports Server (NTRS)

Jensen, Brian J.

2005-01-01

High-performance polymers that have improved processing characteristics, and a method of making them, have been invented. One of the improved characteristics is low (relative to corresponding prior polymers) melt viscosities at given temperatures. This characteristic makes it possible to utilize such processes as resin-transfer molding and resin-film infusion and to perform autoclave processing at lower temperatures and/or pressures. Another improved characteristic is larger processing windows that is, longer times at low viscosities. Other improved characteristics include increased solubility of uncured polymer precursors that contain reactive groups, greater densities of cross-links in cured polymers, improved mechanical properties of the cured polymers, and greater resistance of the cured polymers to chemical attack. The invention is particularly applicable to poly(arylene ether)s [PAEs] and polyimides [PIs] that are useful as adhesives, matrices of composite materials, moldings, films, and coatings. PAEs and PIs synthesized according to the invention comprise mixtures of branched, linear, and star-shaped molecules. The monomers of these polymers can be capped with either reactive end groups to obtain thermosets or nonreactive end groups to obtain thermoplastics. The synthesis of a polymeric mixture according to the invention involves the use of a small amount of a trifunctional monomer. In the case of a PAE, the trifunctional monomer is a trihydroxy- containing compound for example, 1,3,5-trihydroxybenzene (THB). In the case of a PI, the trifunctional monomer is a triamine for example, triamino pyrimidine or melamine. In addition to the aforementioned trifunctional monomer, one uses the difunctional monomers of the conventional formulation of the polymer in question (see figure). In cases of nonreactive end caps, the polymeric mixtures of the invention have melt viscosities and melting temperatures lower than those of the corresponding linear polymers of equal molecular weights. The lower melting temperatures and melt viscosities provide larger processing windows. In cases of reactive end caps, the polymeric mixtures of the invention have lower melt viscosities before curing and the higher cross-link densities after curing (where branching in the uncured systems would become cross-links in the cured systems), relative to the corresponding linear polymers of equal molecular weights. The greater cross-link densities afford increased resistance to chemical attack and improved mechanical properties.

Nonaqueous polypyrrole colloids

DOEpatents

Armes, Steven P.; Aldissi, Mahmoud

1991-01-01

Processable conductive polymers including an oxidized, polymerized aromatic heterocyclic monomer, e.g., pyrrole, an stabilizing effective amount of a poly(vinyl acetate) and dopant anions, and a process of preparing said processable conductive polymers directly in a nonaqueous medium such as methyl acetate, methyl formate, ethyl formate, and propyl formate are disclosed.

Accelerated Testing Of Photothermal Degradation Of Polymers

NASA Technical Reports Server (NTRS)

Kim, Soon Sam; Liang, Ranty Hing; Tsay, Fun-Dow

1989-01-01

Electron-spin-resonance (ESR) spectroscopy and Arrhenius plots used to determine maximum safe temperature for accelerated testing of photothermal degradation of polymers. Aging accelerated by increasing illumination, temperature, or both. Results of aging tests at temperatures higher than those encountered in normal use valid as long as mechanism of degradation same throughout range of temperatures. Transition between different mechanisms at some temperature identified via transition between activation energies, manifesting itself as change in slope of Arrhenius plot at that temperature.

Process for hardening the surface of polymers

DOEpatents

Mansur, L.K.; Lee, E.H.

1992-07-14

Hard surfaced polymers and the method for making them is generally described. Polymers are subjected to simultaneous multiple ion beam bombardment, that results in a hardening of the surface and improved wear resistance. 1 figure.

Direct growth of high crystallinity graphene from water-soluble polymer powders

NASA Astrophysics Data System (ADS)

Chen, Qiao; Zhong, Yujia; Huang, Meirong; Zhao, Guoke; Zhen, Zhen; Zhu, Hongwei

2018-07-01

The use of solid-state carbon sources is effective to produce graphene by safe and low-cost chemical vapor deposition (CVD) process. Water-soluble polymers are generally environmentally friendly and have great potential on large-scale green production of graphene. Here, we systematically study the growth of graphene from water-soluble polymers on copper foils. Two different conversion ways are adopted to investigate the growth mechanism of graphene from water-soluble polymers. We find that the metal-binding functional group hydroxyl strongly influences the vaporization of water-soluble polymers on Cu foils, which hinders the formation of graphene films by rapid thermal treatment. In direct CVD process using water-soluble polymer powders as precursors, oxygenated functional groups in polymers can enhance the crystallinity of as-grown graphene in contrast to solid hydrocarbons without containing oxygen (e.g. polyethylene). Large and continuous graphene films of high quality are synthesized from polyvinyl alcohol and polyethylene glycol. Nitrogen doping in graphene can be easily realized by using nitrogen-containing water-soluble polymers (e.g. polyvinyl pyrrolidone).

Polymer relaxation and stretching dynamics in semi-dilute DNA solutions: a single molecule study

NASA Astrophysics Data System (ADS)

Hsiao, Kai-Wen; Brockman, Christopher; Schroeder, Charles

2015-03-01

In this work, we study polymer relaxation and stretching dynamics in semi-dilute DNA solutions using single molecule techniques. Using this approach, we uncover a unique scaling relation for longest polymer relaxation time that falls in the crossover regime described by semi-flexible polymer solutions, which is distinct from truly flexible polymer chains. In addition, we performed a series of step-strain experiments on single polymers in semi-dilute solutions in planar extensional flow using an automated microfluidic trap. In this way, we are able to precisely control the flow strength and the amount of strain applied to single polymer chains, thereby enabling direct observation of the full stretching and relaxation process in semi-dilute solutions during transient start-up and flow cessation. Interestingly, we observe polymer individualism in the conformation of single chains in semi-dilute solutions, which to our knowledge has not yet been observed. In addition, we observe the relaxation data can be explained by a multi-exponential decay process after flow cessation in semi-dilute solutions. Overall, our work reports key advance in non-dilute polymer systems from a molecular perspective via direct observation of dynamics in strong flows. DOW fellowship.

High aspect ratio template and method for producing same for central and peripheral nerve repair

NASA Technical Reports Server (NTRS)

Sakamoto, Jeff S. (Inventor); Chan, Christina (Inventor); Tuszynski, Mark Henry (Inventor); Mehrotra, Sumit (Inventor); Gros, Thomas (Inventor)

2011-01-01

Millimeter to nano-scale structures manufactured using a multi-component polymer fiber matrix are disclosed. The use of dissimilar polymers allows the selective dissolution of the polymers at various stages of the manufacturing process. In one application, biocompatible matrixes may be formed with long pore length and small pore size. The manufacturing process begins with a first polymer fiber arranged in a matrix formed by a second polymer fiber. End caps may be attached to provide structural support and the polymer fiber matrix selectively dissolved away leaving only the long polymer fibers. These may be exposed to another product, such as a biocompatible gel to form a biocompatible matrix. The polymer fibers may then be selectively dissolved leaving only a biocompatible gel scaffold with the pores formed by the dissolved polymer fibers. The scaffolds may be used in, among other applications, the repair of central and peripheral nerves. Scaffolds for the repair of peripheral nerves may include a reservoir for the sustained release of nerve growth factor. The scaffolds may also include a multifunctional polyelectrolyte layer for the sustained release of nerve growth factor and enhance biocompatibility.

Evolution of material properties during free radical photopolymerization

NASA Astrophysics Data System (ADS)

Wu, Jiangtao; Zhao, Zeang; Hamel, Craig M.; Mu, Xiaoming; Kuang, Xiao; Guo, Zaoyang; Qi, H. Jerry

2018-03-01

Photopolymerization is a widely used polymerization method in many engineering applications such as coating, dental restoration, and 3D printing. It is a complex chemical and physical process, through which a liquid monomer solution is rapidly converted to a solid polymer. In the most common free-radical photopolymerization process, the photoinitiator in the solution is exposed to light and decomposes into active radicals, which attach to monomers to start the polymerization reaction. The activated monomers then attack Cdbnd C double bonds of unsaturated monomers, which leads to the growth of polymer chains. With increases in the polymer chain length and the average molecular weight, polymer chains start to connect and form a network structure, and the liquid polymer solution becomes a dense solid. During this process, the material properties of the cured polymer change dramatically. In this paper, experiments and theoretical modeling are used to investigate the free-radical photopolymerization reaction kinetics, material property evolution and mechanics during the photopolymerization process. The model employs the first order chemical reaction rate equations to calculate the variation of the species concentrations. The degree of monomer conversion is used as an internal variable that dictates the mechanical properties of the cured polymer at different curing states, including volume shrinkage, glass transition temperature, and nonlinear viscoelastic properties. To capture the nonlinear behavior of the cured polymer under low temperature and finite deformation, a multibranch nonlinear viscoelastic model is developed. A phase evolution model is used to describe the mechanics of the coupling between the crosslink network evolution and mechanical loading during the curing process. The comparison of the model and the experimental results indicates that the model can capture property changes during curing. The model is further applied to investigate the internal stress of a thick sample caused by volume shrinkage during photopolymerization. Changes in the conversion degree gradient and the internal stress during photopolymerization are determined using FEM simulation. The model can be extended to many photocuring processes, such as photopolymerization 3D printing, surface coating and automotive part curing processes.

Laser micromachining as a metallization tool for microfluidic polymer stacks

NASA Astrophysics Data System (ADS)

Brettschneider, T.; Dorrer, C.; Czurratis, D.; Zengerle, R.; Daub, M.

2013-03-01

A novel assembly approach for the integration of metal structures into polymeric microfluidic systems is described. The presented production process is completely based on a single solid-state laser source, which is used to incorporate metal foils into a polymeric multi-layer stack by laser bonding and ablation processes. Chemical reagents or glues are not required. The polymer stack contains a flexible membrane which can be used for realizing microfluidic valves and pumps. The metal-to-polymer bond was investigated for different metal foils and plasma treatments, yielding a maximum peel strength of Rps = 1.33 N mm-1. A minimum structure size of 10 µm was determined by 3D microscopy of the laser cut line. As an example application, two different metal foils were used in combination to micromachine a standardized type-T thermocouple on a polymer substrate. An additional laser process was developed which allows metal-to-metal welding in close vicinity to the polymer substrate. With this process step, the reliability of the electrical contact could be increased to survive at least 400 PCR temperature cycles at very low contact resistances.

Molding process for imidazopyrrolone polymers

NASA Technical Reports Server (NTRS)

Johnson, C. L. (Inventor)

1973-01-01

A process is described for producing shaped articles of imidazopyrrolone polymers comprising molding imidazopyrrolone polymer molding power under pressure and at a temperature greater than 475 C. Moderate pressures may be employed. Preferably, prior to molding, a preform is prepared by isostatic compression. The preform may be molded at a relatively low initial pressure and temperature; as the temperature is increased to a value greater than 475 C., the pressure is also increased.

Computational analysis for biodegradation of exogenously depolymerizable polymer

NASA Astrophysics Data System (ADS)

Watanabe, M.; Kawai, F.

2018-03-01

This study shows that microbial growth and decay in a biodegradation process of exogenously depolymerizable polymer are controlled by consumption of monomer units. Experimental outcomes for residual polymer were incorporated in inverse analysis for a degradation rate. The Gauss-Newton method was applied to an inverse problem for two parameter values associated with the microbial population. A biodegradation process of polyethylene glycol was analyzed numerically, and numerical outcomes were obtained.

Hydrophobically-associating cationic polymers as micro-bubble surface modifiers in dissolved air flotation for cyanobacteria cell separation.

PubMed

Yap, R K L; Whittaker, M; Diao, M; Stuetz, R M; Jefferson, B; Bulmus, V; Peirson, W L; Nguyen, A V; Henderson, R K

2014-09-15

Dissolved air flotation (DAF), an effective treatment method for clarifying algae/cyanobacteria-laden water, is highly dependent on coagulation-flocculation. Treatment of algae can be problematic due to unpredictable coagulant demand during blooms. To eliminate the need for coagulation-flocculation, the use of commercial polymers or surfactants to alter bubble charge in DAF has shown potential, termed the PosiDAF process. When using surfactants, poor removal was obtained but good bubble adherence was observed. Conversely, when using polymers, effective cell removal was obtained, attributed to polymer bridging, but polymers did not adhere well to the bubble surface, resulting in a cationic clarified effluent that was indicative of high polymer concentrations. In order to combine the attributes of both polymers (bridging ability) and surfactants (hydrophobicity), in this study, a commercially-available cationic polymer, poly(dimethylaminoethyl methacrylate) (polyDMAEMA), was functionalised with hydrophobic pendant groups of various carbon chain lengths to improve adherence of polymer to a bubble surface. Its performance in PosiDAF was contrasted against commercially-available poly(diallyl dimethyl ammonium chloride) (polyDADMAC). All synthesised polymers used for bubble surface modification were found to produce positively charged bubbles. When applying these cationic micro-bubbles in PosiDAF, in the absence of coagulation-flocculation, cell removals in excess of 90% were obtained, reaching a maximum of 99% cell removal and thus demonstrating process viability. Of the synthesised polymers, the polymer containing the largest hydrophobic functionality resulted in highly anionic treated effluent, suggesting stronger adherence of polymers to bubble surfaces and reduced residual polymer concentrations. Copyright © 2014 Elsevier Ltd. All rights reserved.

Processing Solvent Dependent Morphology of Diketopyrrolopyrrole (DPP) based Low Band Gap Polymer and PCBM Blends

NASA Astrophysics Data System (ADS)

Ferdous, Sunzida; Liu, Feng; Russell, Thomas

2013-03-01

Solution processing of polymer semiconductors is widely used for fabrication of low cost organic solar cells. Recently, mixed solvent systems or additive based systems for fabricating polymer solar cells have proven to be beneficial for obtaining high performance devices with multi-length scale morphologies. To control the morphology during the processing step, one needs to understand the effect of solvent as it evaporates to form the final thin film structure. In this study, we used diketopyrrolopyrrole (DPP) based low band gap polymer and phenyl-C71-butyric acid methyl ester (PCBM) blend in a series of mixed solvent systems consisting of a good solvent for both of the active material components, as well as different solvents that are good solvents for PCBM, but poor solvents for the polymer. Different evaporation times of the poor solvents during the drying process, and different solubility of the polymer in these poor solvents as well as their interaction with the substrate play an important role in the final morphology. In-situ GIWAXS studies were performed to observe the evolution of the structure as the solvent evaporates. The final morphologies of the thin film devices were also characterized by AFM, TEM, and various x-ray scattering techniques to correlate the morphology with the obtained device performances.

Solid electrolyte material manufacturable by polymer processing methods

DOEpatents

Singh, Mohit; Gur, Ilan; Eitouni, Hany Basam; Balsara, Nitash Pervez

2012-09-18

The present invention relates generally to electrolyte materials. According to an embodiment, the present invention provides for a solid polymer electrolyte material that is ionically conductive, mechanically robust, and can be formed into desirable shapes using conventional polymer processing methods. An exemplary polymer electrolyte material has an elastic modulus in excess of 1.times.10.sup.6 Pa at 90 degrees C. and is characterized by an ionic conductivity of at least 1.times.10.sup.-5 Scm-1 at 90 degrees C. An exemplary material can be characterized by a two domain or three domain material system. An exemplary material can include material components made of diblock polymers or triblock polymers. Many uses are contemplated for the solid polymer electrolyte materials. For example, the present invention can be applied to improve Li-based batteries by means of enabling higher energy density, better thermal and environmental stability, lower rates of self-discharge, enhanced safety, lower manufacturing costs, and novel form factors.

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

PubMed

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

2010-09-01

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 create a hermetic join with an extended life remains the barrier to widespread acceptance of polymers for this application. This article provides an overview of the current techniques used for direct bonding of polymers, with a focus on thermoplastics. Thermal bonding methods are feasible, but some take too long and/or require two stage processing. Some methods are not suitable because of excessive heat load which may be delivered to sensitive components within the capsule. Laser welding is presented as the method of choice; however the establishment of suitable laser process parameters will require significant research. 2010. Published by Elsevier Ltd.

Synthesis of molecular imprinting polymers for extraction of gallic acid from urine.

PubMed

Bhawani, Showkat Ahmad; Sen, Tham Soon; Ibrahim, Mohammad Nasir Mohammad

2018-02-21

The molecularly imprinted polymers for gallic acid were synthesized by precipitation polymerization. During the process of synthesis a non-covalent approach was used for the interaction of template and monomer. In the polymerization process, gallic acid was used as a template, acrylic acid as a functional monomer, ethylene glycol dimethacrylate as a cross-linker and 2,2'-azobisisobutyronitrile as an initiator and acetonitrile as a solvent. The synthesized imprinted and non-imprinted polymer particles were characterized by using Fourier-transform infrared spectroscopy and scanning electron microscopy. The rebinding efficiency of synthesized polymer particles was evaluated by batch binding assay. The highly selective imprinted polymer for gallic acid was MIPI1 with a composition (molar ratio) of 1:4:20, template: monomer: cross-linker, respectively. The MIPI1 showed highest binding efficiency (79.50%) as compared to other imprinted and non-imprinted polymers. The highly selective imprinted polymers have successfully extracted about 80% of gallic acid from spiked urine sample.

Stepwise heating in Stille polycondensation toward no batch-to-batch variations in polymer solar cell performance.

PubMed

Lee, Sang Myeon; Park, Kwang Hyun; Jung, Seungon; Park, Hyesung; Yang, Changduk

2018-05-14

For a given π-conjugated polymer, the batch-to-batch variations in molecular weight (M w ) and polydispersity index (Ð) can lead to inconsistent process-dependent material properties and consequent performance variations in the device application. Using a stepwise-heating protocol in the Stille polycondensation in conjunction with optimized processing, we obtained an ultrahigh-quality PTB7 polymer having high M w and very narrow Ð. The resulting ultrahigh-quality polymer-based solar cells demonstrate up to 9.97% power conversion efficiencies (PCEs), which is over 24% enhancement from the control devices fabricated with commercially available PTB7. Moreover, we observe almost negligible batch-to-batch variations in the overall PCE values from ultrahigh-quality polymer-based devices. The proposed stepwise polymerization demonstrates a facile and effective strategy for synthesizing high-quality semiconducting polymers that can significantly improve device yield in polymer-based solar cells, an important factor for the commercialization of organic solar cells, by mitigating device-to-device variations.

Fabrication of fiber supported ionic liquids and methods of use

DOEpatents

Luebke, David R; Wickramanayake, Shan

2013-02-26

One or more embodiments relates to the production of a fabricated fiber having an asymmetric polymer network and having an immobilized liquid such as an ionic liquid within the pores of the polymer network. The process produces the fabricated fiber in a dry-wet spinning process using a homogenous dope solution, providing significant advantage over current fabrication methods for liquid-supporting polymers. The fabricated fibers may be effectively utilized for the separation of a chemical species from a mixture based on the selection of the polymer, the liquid, and the solvent utilized in the dope.

Conductivity fuel cell collector plate and method of fabrication

DOEpatents

Braun, James C.

2002-01-01

An improved method of manufacturing a PEM fuel cell collector plate is disclosed. During molding a highly conductive polymer composite is formed having a relatively high polymer concentration along its external surfaces. After molding the polymer rich layer is removed from the land areas by machining, grinding or similar process. This layer removal results in increased overall conductivity of the molded collector plate. The polymer rich surface remains in the collector plate channels, providing increased mechanical strength and other benefits to the channels. The improved method also permits greater mold cavity thickness providing a number of advantages during the molding process.

High-Performance, Semi-Interpenetrating Polymer Network

NASA Technical Reports Server (NTRS)

Pater, Ruth H.; Lowther, Sharon E.; Smith, Janice Y.; Cannon, Michelle S.; Whitehead, Fred M.; Ely, Robert M.

1992-01-01

High-performance polymer made by new synthesis in which one or more easy-to-process, but brittle, thermosetting polyimides combined with one or more tough, but difficult-to-process, linear thermoplastics to yield semi-interpenetrating polymer network (semi-IPN) having combination of easy processability and high tolerance to damage. Two commercially available resins combined to form tough, semi-IPN called "LaRC-RP49." Displays improvements in toughness and resistance to microcracking. LaRC-RP49 has potential as high-temperature matrix resin, adhesive, and molding resin. Useful in aerospace, automotive, and electronic industries.

Synthetic biodegradable functional polymers for tissue engineering: a brief review.

PubMed

BaoLin, Guo; Ma, Peter X

2014-04-01

Scaffolds play a crucial role in tissue engineering. Biodegradable polymers with great processing flexibility are the predominant scaffolding materials. Synthetic biodegradable polymers with well-defined structure and without immunological concerns associated with naturally derived polymers are widely used in tissue engineering. The synthetic biodegradable polymers that are widely used in tissue engineering, including polyesters, polyanhydrides, polyphosphazenes, polyurethane, and poly (glycerol sebacate) are summarized in this article. New developments in conducting polymers, photoresponsive polymers, amino-acid-based polymers, enzymatically degradable polymers, and peptide-activated polymers are also discussed. In addition to chemical functionalization, the scaffold designs that mimic the nano and micro features of the extracellular matrix (ECM) are presented as well, and composite and nanocomposite scaffolds are also reviewed.

New insights into the mechanism of interaction between CO2 and polymers from thermodynamic parameters obtained by in situ ATR-FTIR spectroscopy.

PubMed

Gabrienko, Anton A; Ewing, Andrew V; Chibiryaev, Andrey M; Agafontsev, Alexander M; Dubkov, Konstantin A; Kazarian, Sergei G

2016-03-07

This work reports new physical insights of the thermodynamic parameters and mechanisms of possible interactions occurring in polymers subjected to high-pressure CO2. ATR-FTIR spectroscopy has been used in situ to determine the thermodynamic parameters of the intermolecular interactions between CO2 and different functional groups of the polymers capable of specific interactions with sorbed CO2 molecules. Based on the measured ATR-FTIR spectra of the polymer samples subjected to high-pressure CO2 (30 bar) at different temperatures (300-340 K), it was possible to characterize polymer-polymer and CO2-polymer interactions. Particularly, the enthalpy and entropy of the formation of the specific non-covalent complexes between CO2 and the hydroxy (-OH), carbonyl (C[double bond, length as m-dash]O) and hydroxyimino ([double bond, length as m-dash]N-OH) functional groups of the polymer samples have been measured. Furthermore, the obtained spectroscopic results have provided an opportunity for the structure of these complexes to be proposed. An interesting phenomenon regarding the behavior of CO2/polymer systems has also been observed. It has been found that only for the polyketone, the value of enthalpy was negative indicating an exothermic process during the formation of the CO2-polymer non-covalent complexes. Conversely, for the polyoxime and polyalcohol samples there is a positive enthalpy determined. This is a result of the initial polymer-polymer interactions requiring more energy to break than is released during the formation of the CO2-polymer complex. The effect of increasing temperature to facilitate the breaking of the polymer-polymer interactions has also been observed. Hence, a mechanism for the formation of CO2-polymer complexes was suggested based on these results, which occurs via a two-step process: (1) the breaking of the existing polymer-polymer interactions followed by (2) the formation of new CO2-polymer non-covalent interactions.

Method of making polymer powders and whiskers as well as particulate products of the method and atomizing apparatus

DOEpatents

Otaigbe, Joshua U.; McAvoy, Jon M.; Anderson, Iver E.; Ting, Jason; Mi, Jia; Terpstra, Robert

2001-01-09

Method for making polymer particulates, such as spherical powder and whiskers, by melting a polymer material under conditions to avoid thermal degradation of the polymer material, atomizing the melt using gas jet means in a manner to form atomized droplets, and cooling the droplets to form polymer particulates, which are collected for further processing. Atomization parameters can be controlled to produce polymer particulates with controlled particle shape, particle size, and particle size distribution. For example, atomization parameters can be controlled to produce spherical polymer powders, polymer whiskers, and combinations of spherical powders and whiskers. Atomizing apparatus also is provided for atoomizing polymer and metallic materials.

Automated manufacturing process for DEAP stack-actuators

NASA Astrophysics Data System (ADS)

Tepel, Dominik; Hoffstadt, Thorben; Maas, Jürgen

2014-03-01

Dielectric elastomers (DE) are thin polymer films belonging to the class of electroactive polymers (EAP), which are coated with compliant and conductive electrodes on each side. Due to the influence of an electrical field, dielectric elastomers perform a large amount of deformation. In this contribution a manufacturing process of automated fabricated stack-actuators based on dielectric electroactive polymers (DEAP) are presented. First of all the specific design of the considered stack-actuator is explained and afterwards the development, construction and realization of an automated manufacturing process is presented in detail. By applying this automated process, stack-actuators with reproducible and homogeneous properties can be manufactured. Finally, first DEAP actuator modules fabricated by the mentioned process are validated experimentally.

Behavior of polysulfone composite and nanocomposite membranes under hypochlorite ageing

NASA Astrophysics Data System (ADS)

Anadão, Priscila; Souza de Santis, Henrique; Rezende Montes, Rafael; Wiebeck, Hélio

2018-05-01

Polysulfone activated carbon or graphite composite membranes and polysulfone montmorillonite clay nanocomposite membranes were prepared by wet-phase inversion method. Its effectiveness against hypochlorite degradation by forming composite and nanocomposite structures was studied by means of an ageing experiment. The formation of some fissures on the composite membrane surface was observed through electron micrographs scanning. The number-average molecular weight of the polysulfone of all membranes was reduced. This reduction was more noticeable in the composite membranes owing to the lower interaction between polymer chains and filler, such interaction being also the reason for polydispersity increase. Fourier transform infrared spectroscopy detected the reduction of the PSf bands in the nanocomposite membranes; in the composite membranes, some PSf band intensities were probably increased owing to the exposure of the PSf groups to the ageing process. All membranes presented brittleness with ageing, which was more pronounced in the composite membranes due to the membrane defects formed.

Processing of plastics

PubMed Central

Spaak, Albert

1975-01-01

An overview is given of the processing of plastic materials from the handling of polymers in the pellet and powder form to manufacturing of a plastic fabricated product. Various types of equipment used and melt processing ranges of various polymer formulations to make the myriad of plastic products that are commercially available are discussed. PMID:1175556

Controlled release of tocopherols from polymer blend films

NASA Astrophysics Data System (ADS)

Obinata, Noe

Controlled release packaging has great potential to increase storage stability of foods by releasing active compounds into foods continuously over time. However, a major limitation in development of this technology is the inability to control the release and provide rates useful for long term storage of foods. Better understanding of the factors affecting active compound release is needed to overcome this limitation. The objective of this research was to investigate the relationship between polymer composition, polymer processing method, polymer morphology, and release properties of active compounds, and to provide proof of principle that compound release is controlled by film morphology. A natural antioxidant, tocopherol was used as a model active compound because it is natural, effective, heat stable, and soluble in most packaging polymers. Polymer blend films were produced from combination of linear low density polyethylene (LLDPE) and high density polyethylene (HDPE), polypropylene (PP), or polystyrene (PS) with 3000 ppm mixed tocopherols using conventional blending method and innovative blending method, smart blending with a novel mixer using chaotic advection. Film morphologies were visualized with scanning electron microscopy (SEM). Release of tocopherols into 95% ethanol as a food simulant was measured by UV/Visible spectrophotometry or HPLC, and diffusivity of tocopherols in the polymers was estimated from this data. Polymer composition (blend proportions) and processing methods have major effects on film morphology. Four different types of morphologies, dispersed, co-continuous, fiber, and multilayer structures were developed by either conventional extrusion or smart blending. With smart blending of fixed polymer compositions, different morphologies were progressively developed with fixed polymer composition as the number of rod rotations increased, providing a way to separate effects of polymer composition and morphology. The different morphologies obtained using conventional and smart blending greatly affected tocopherol release. Strong correlation was observed between morphology and release rate: multilayer, slow release; co-continuous and fiber, moderate; disperse: fast release. Results indicate that morphology can be manipulated by polymer composition and processing method, and release rates of tocopherols are varied with polymer morphology. Manipulating polymer compositions and film morphologies may provide a means to control the release of tocopherols from food contact films.

Characterization of molecularly imprinted polymers using a new polar solvent titration method.

PubMed

Song, Di; Zhang, Yagang; Geer, Michael F; Shimizu, Ken D

2014-07-01

A new method of characterizing molecularly imprinted polymers (MIPs) was developed and tested, which provides a more accurate means of identifying and measuring the molecular imprinting effect. In the new polar solvent titration method, a series of imprinted and non-imprinted polymers were prepared in solutions containing increasing concentrations of a polar solvent. The polar solvent additives systematically disrupted the templation and monomer aggregation processes in the prepolymerization solutions, and the extent of disruption was captured by the polymerization process. The changes in binding capacity within each series of polymers were measured, providing a quantitative assessment of the templation and monomer aggregation processes in the imprinted and non-imprinted polymers. The new method was tested using three different diphenyl phosphate imprinted polymers made using three different urea functional monomers. Each monomer had varying efficiencies of templation and monomer aggregation. The new MIP characterization method was found to have several advantages. To independently verify the new characterization method, the MIPs were also characterized using traditional binding isotherm analyses. The two methods appeared to give consistent conclusions. First, the polar solvent titration method is less susceptible to false positives in identifying the imprinting effect. Second, the method is able to differentiate and quantify changes in binding capacity, as measured at a fixed guest and polymer concentration, arising from templation or monomer aggregation processes in the prepolymerization solution. Third, the method was also easy to carry out, taking advantage of the ease of preparing MIPs. Copyright © 2014 John Wiley & Sons, Ltd.

3D Printing of Ball Grid Arrays

NASA Astrophysics Data System (ADS)

Sinha, Shayandev; Hines, Daniel; Dasgupta, Abhijit; Das, Siddhartha

Ball grid arrays (BGA) are interconnects between an integrated circuit (IC) and a printed circuit board (PCB), that are used for surface mounting electronic components. Typically, lead free alloys are used to make solder balls which, after a reflow process, establish a mechanical and electrical connection between the IC and the PCB. High temperature processing is required for most of these alloys leading to thermal shock causing damage to ICs. For producing flexible circuits on a polymer substrate, there is a requirement for low temperature processing capabilities (around 150 C) and for reducing strain from mechanical stresses. Additive manufacturing techniques can provide an alternative methodology for fabricating BGAs as a direct replacement for standard solder bumped BGAs. We have developed aerosol jet (AJ) printing methods to fabricate a polymer bumped BGA. As a demonstration of the process developed, a daisy chain test chip was polymer bumped using an AJ printed ultra violet (UV) curable polymer ink that was then coated with an AJ printed silver nanoparticle laden ink as a conducting layer printed over the polymer bump. The structure for the balls were achieved by printing the polymer ink using a specific toolpath coupled with in-situ UV curing of the polymer which provided good control over the shape, resulting in well-formed spherical bumps on the order of 200 um wide by 200 um tall for this initial demonstration. A detailed discussion of the AJ printing method and results from accelerated life-time testing will be presented

A Mechanistic Understanding of a Binary Additive System to Synergistically Boost Efficiency in All-Polymer Solar Cells

PubMed Central

Kim, Yu Jin; Ahn, Sunyong; Wang, Dong Hwan; Park, Chan Eon

2015-01-01

All-polymer solar cells are herein presented utilizing the PBDTTT-CT donor and the P(NDI2OD-T2) acceptor with 1,8-diiodooctane (DIO) and 1-chloronaphthalene (CN) binary solvent additives. A systematic study of the polymer/polymer bulk heterojunction photovoltaic cells processed from the binary additives revealed that the microstructures and photophysics were quite different from those of a pristine system. The combination of DIO and CN with a DIO/CN ratio of 3:1 (3 vol% DIO, 1 vol% CN and 96 vol% o-DCB) led to suitable penetrating polymer networks, efficient charge generation and balanced charge transport, which were all beneficial to improving the efficiency. This improvement is attributed to increase in power conversion efficiency from 2.81% for a device without additives to 4.39% for a device with the binary processing additives. A detailed investigation indicates that the changes in the polymer:polymer interactions resulted in the formation of a percolating nasnoscale morphology upon processing with the binary additives. Depth profile measurements with a two-dimensional grazing incidence wide-angle X-ray scattering confirm this optimum phase feature. Furthermore impedance spectroscopy also finds evidence for synergistically boosting the device performance. PMID:26658472

Poly(Amide-imide) Aerogel Materials Produced via an Ice Templating Process

PubMed Central

Gawryla, Matthew D.; Arndt, Eric M.

2018-01-01

Low density composites of sodium montmorillonite and poly(amide-imide) polymers have been created using an ice templating method, which serves as an alternative to the often-difficult foaming of high temperature/high performance polymers. The starting polymer was received in the poly(amic acid) form which can be cured using heat, into a water insoluble amide-imide copolymer. The resulting materials have densities in the 0.05 g/cm3 range and have excellent mechanical properties. Using a tertiary amine as a processing aid provides for lower viscosity and allows more concentrated polymer solutions to be used. The concentration of the amine relative to the acid groups on the polymer backbone has been found to cause significant difference in the mechanical properties of the dried materials. The synthesis and characterization of low density versions of two poly(amide-imide) polymers and their composites with sodium montmorillonite clay are discussed in the present work. PMID:29401663

Poly(Amide-imide) Aerogel Materials Produced via an Ice Templating Process.

PubMed

Gawryla, Matthew D; Arndt, Eric M; Sánchez-Soto, Miguel; Schiraldi, David A

2018-02-03

Low density composites of sodium montmorillonite and poly(amide-imide) polymers have been created using an ice templating method, which serves as an alternative to the often-difficult foaming of high temperature/high performance polymers. The starting polymer was received in the poly(amic acid) form which can be cured using heat, into a water insoluble amide-imide copolymer. The resulting materials have densities in the 0.05 g/cm³ range and have excellent mechanical properties. Using a tertiary amine as a processing aid provides for lower viscosity and allows more concentrated polymer solutions to be used. The concentration of the amine relative to the acid groups on the polymer backbone has been found to cause significant difference in the mechanical properties of the dried materials. The synthesis and characterization of low density versions of two poly(amide-imide) polymers and their composites with sodium montmorillonite clay are discussed in the present work.

Metallization of electronic insulators

DOEpatents

Gottesfeld, Shimshon; Uribe, Francisco A.

1994-01-01

An electroplated element is formed to include an insulating substrate, a conducting polymer polymerized in situ on the substrate, and a metal layer deposited on the conducting polymer. In one application a circuit board is formed by polymerizing pyrrole on an epoxy-fiberglass substrate in a single step process and then electrodepositing a metal over the resulting polypyrrole polymer. No chemical deposition of the metal is required prior to electroplating and the resulting layer of substrate-polymer-metal has excellent adhesion characteristics. The metal deposition is surprisingly smooth and uniform over the relatively high resistance film of polypyrrole. A continuous manufacturing process is obtained by filtering the solution between successive substrates to remove polymer formed in the solution, by maintaining the solution oxidizing potential within selected limits, and by adding a strong oxidant, such as KMnO.sub.4 at periodic intervals to maintain a low sheet resistivity in the resulting conducting polymer film.

Manipulation of Molecular Weight Distribution Shape as a New Strategy to Control Processing Parameters.

PubMed

Nadgorny, Milena; Gentekos, Dillon T; Xiao, Zeyun; Singleton, S Parker; Fors, Brett P; Connal, Luke A

2017-10-01

Molecular weight and dispersity (Ð) influence physical and rheological properties of polymers, which are of significant importance in polymer processing technologies. However, these parameters provide only partial information about the precise composition of polymers, which is reflected by the shape and symmetry of molecular weight distribution (MWD). In this work, the effect of MWD symmetry on thermal and rheological properties of polymers with identical molecular weights and Ð is demonstrated. Remarkably, when the MWD is skewed to higher molecular weight, a higher glass transition temperature (T g ), increased stiffness, increased thermal stability, and higher apparent viscosities are observed. These observed differences are attributed to the chain length composition of the polymers, easily controlled by the synthetic strategy. This work demonstrates a versatile approach to engineer the properties of polymers using controlled synthesis to skew the shape of MWD. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Novel thermal annealing methodology for permanent tuning polymer optical fiber Bragg gratings to longer wavelengths.

PubMed

Pospori, A; Marques, C A F; Sagias, G; Lamela-Rivera, H; Webb, D J

2018-01-22

The Bragg wavelength of a polymer optical fiber Bragg grating can be permanently shifted by utilizing the thermal annealing method. In all the reported fiber annealing cases, the authors were able to tune the Bragg wavelength only to shorter wavelengths, since the polymer fiber shrinks in length during the annealing process. This article demonstrates a novel thermal annealing methodology for permanently tuning polymer optical fiber Bragg gratings to any desirable spectral position, including longer wavelengths. Stretching the polymer optical fiber during the annealing process, the period of Bragg grating, which is directly related with the Bragg wavelength, can become permanently longer. The methodology presented in this article can be used to multiplex polymer optical fiber Bragg gratings at any desirable spectral position utilizing only one phase-mask for their photo-inscription, reducing thus their fabrication cost in an industrial setting.

Macro and micro analysis of small molecule diffusion in amorphous polymers

NASA Astrophysics Data System (ADS)

Putta, Santosh Krishna

In this study, both macroscopic and microscopic numerical techniques have been explored, to model and understand the diffusion behavior of small molecules in amorphous polymers, which very often do not follow the classical Fickian law. It was attempted to understand the influence of various aspects of the molecular structure of a polymer on its macroscopic diffusion behavior. At the macroscopic level, a hybrid finite-element/finite-difference model is developed to implement the coupled diffusion and deformation constitutive equations. A viscoelasticity theory, combined with time-freevolume superposition is used to model the deformation processes. A freevolume-based model is used to model the diffusion processes. The freevolume in the polymer is used as a coupling factor between the deformation and the diffusion processes. The model is shown to qualitatively describe some of the typical non-Fickian diffusion behavior in polymers. However, it does not directly involve the microstructure of a polymer. Further, some of the input parameters to the model are difficult to obtain experimentally. A numerical microscopic approach is therefore adopted to study the molecular structure of polymers. A molecular mechanics and dynamics technique combined with a modified Rotational Isomeric State (RIS) approach, is followed to generate the molecular structure for two types of polycarbonates, and, two types of polyacrylates, starting only with their chemical structures. A new efficient 3-D algorithm for Delaunay Tessellation is developed, and, then applied to discretize the molecular structure into Delaunay Tetrahedra. By using the dicretized molecular structure, size, shape, and, connectivity of free-spaces for small molecule diffusion in the above mentioned polymers, are then studied in relation to their diffusion properties. The influence of polymer and side chain flexibility, and diffusant-diffusant and diffusant-polymer molecular interactions, is also discussed with respect to the diffusion properties.

Visible Light Responsive Liquid Crystal Polymers Containing Reactive Moieties with Good Processability.

PubMed

Liu, Yuyun; Wu, Wei; Wei, Jia; Yu, Yanlei

2017-01-11

Two types of novel reactive linear liquid crystal polymers (LLCPs) with different azotolene concentrations have been synthesized and processed into films and fibers by solution and melting processing methods. Then, the LLCPs in the obtained monodomain fiber and polydomain film were easily cross-linked with difunctional primary amines. The resulted cross-linked liquid crystal polymers (CLCPs) underwent reversible photoinduced bending and unbending behaviors in response to 445 and 530 nm visible light at room temperature, respectively. The post-cross-linking method provides a facile way to prepare the CLCP films and fibers with different shapes from LLCPs, which can be processed by traditional melting and solution methods.

Nanostructural self-organization and dynamic adaptation of metal-polymer tribosystems

NASA Astrophysics Data System (ADS)

Mashkov, Yu. K.

2017-02-01

The results of investigating the effect of nanosize modifiers of a polymer matrix on the nanostructural self-organization of polymer composites and dynamic adaptation of metal-polymer tribosystems, which considerably affect the wear resistance of polymer composite materials, have been analyzed. It has been shown that the physicochemical nanostructural self-organization processes are developed in metal-polymer tribosystems with the formation of thermotropic liquid-crystal structures of the polymer matrix, followed by the transition of the system to the stationary state with a negative feedback that ensures dynamic adaptation of the tribosystem to given operating conditions.

Manufacturing a Porous Structure According to the Process Parameters of Functional 3D Porous Polymer Printing Technology Based on a Chemical Blowing Agent

NASA Astrophysics Data System (ADS)

Yoo, C. J.; Shin, B. S.; Kang, B. S.; Yun, D. H.; You, D. B.; Hong, S. M.

2017-09-01

In this paper, we propose a new porous polymer printing technology based on CBA(chemical blowing agent), and describe the optimization process according to the process parameters. By mixing polypropylene (PP) and CBA, a hybrid CBA filament was manufactured; the diameter of the filament ranged between 1.60 mm and 1.75 mm. A porous polymer structure was manufactured based on the traditional fused deposition modelling (FDM) method. The process parameters of the three-dimensional (3D) porous polymer printing (PPP) process included nozzle temperature, printing speed, and CBA density. Porosity increase with an increase in nozzle temperature and CBA density. On the contrary, porosity increase with a decrease in the printing speed. For porous structures, it has excellent mechanical properties. We manufactured a simple shape in 3D using 3D PPP technology. In the future, we will study the excellent mechanical properties of 3D PPP technology and apply them to various safety fields.

Fabrication of nanofibers reinforced polymer microstructures using femtosecond laser material processing

NASA Astrophysics Data System (ADS)

Alubaidy, Mohammed-Amin

A new method has been introduced for the formation of microfeatures made of nanofibers reinforced polymer, using femtosecond laser material processing. The Femtosecond laser is used for the generation of three-dimensional interweaved nanofibers and the construction of microfeatures, like microchannels and voxels, through multi photon polymerization of nanofiber dispersed polymer resin. A new phenomenon of multiphoton polymerization induced by dual wavelength irradiation was reported for the first time. A significant improvement in the spatial resolution, compared to the two photon absorption (2PA) and the three photon absorption (3PA) processes has been achieved. Conductive polymer microstructures and magnetic polymer microstructures have been fabricated through this method. The mechanical properties of nanofiber reinforced polymer microstructures has been investigated by means of nanoindentation and the volume fraction of the generated nanofibers in the nanocomposite was calculated by using nanoindentation analysis. The results showed significant improvement in strength of the material. The electrical conductivity of the two photon polymerization (TPP) generated microfeatures was measured by a two-probe system at room temperature and the conductivity-temperature relationship was measured at a certain temperature range. The results suggest that the conductive polymer microstructure is reproducible and has a consistent conductivity-temperature relation. The magnetic strength has been characterized using Guassmeter. To demonstrate the potential application of the new fabrication method, a novel class of DNA-functionalized three-dimensional (3D), stand-free, and nanostructured electrodes were fabricated. The developed nanofibrous DNA biosensor has been characterized by cyclic voltammetry with the use of ferrocyanide as an electrochemical redox indicator. Results showed that the probe--target recognition has been improved. This research demonstrated that femtosecond laser materials processing is a viable tool of the construction of naomaterial- reinforced polymer microfeatures with tailored properties.

Electrospun Polymer Blend Nanofibers for Tunable Drug Delivery: The Role of Transformative Phase Separation on Controlling the Release Rate.

PubMed

Tipduangta, Pratchaya; Belton, Peter; Fábián, László; Wang, Li Ying; Tang, Huiru; Eddleston, Mark; Qi, Sheng

2016-01-04

Electrospun fibrous materials have a wide range of biomedical applications, many of them involving the use of polymers as matrices for incorporation of therapeutic agents. The use of polymer blends improves the tuneability of the physicochemical and mechanical properties of the drug loaded fibers. This also benefits the development of controlled drug release formulations, for which the release rate can be modified by altering the ratio of the polymers in the blend. However, to realize these benefits, a clear understanding of the phase behavior of the processed polymer blend is essential. This study reports an in depth investigation of the impact of the electrospinning process on the phase separation of a model partially miscible polymer blend, PVP K90 and HPMCAS, in comparison to other conventional solvent evaporation based processes including film casting and spin coating. The nanoscale stretching and ultrafast solvent removal of electrospinning lead to an enhanced apparent miscibility between the polymers, with the same blends showing micronscale phase separation when processed using film casting and spin coating. Nanoscale phase separation in electrospun blend fibers was confirmed in the dry state. Rapid, layered, macroscale phase separation of the two polymers occurred during the wetting of the fibers. This led to a biphasic drug release profile from the fibers, with a burst release from PVP-rich phases and a slower, more continuous release from HPMCAS-rich phases. It was noted that the model drug, paracetamol, had more favorable partitioning into the PVP-rich phase, which is likely to be a result of greater hydrogen bonding between PVP and paracetamol. This led to higher drug contents in the PVP-rich phases than the HPMCAS-rich phases. By alternating the proportions of the PVP and HPMCAS, the drug release rate can be modulated.

Process to prepare stable trifluorostyrene containing compounds grafted to base polymers using a solvent/water mixture

DOEpatents

Roelofs, Mark Gerrit; Yang, Zhen-Yu; Han, Amy Qi

2010-06-15

A fluorinated ion exchange polymer is prepared by grafting at least one grafting monomer derived from trifluorostyrene on to at least one base polymer in a organic solvent/water mixture. These ion exchange polymers are useful in preparing catalyst coated membranes and membrane electrode assemblies used in fuel cells.

Disentangled solid state and metastable polymer melt; a solvent free route to high-modulus high-strength tapes and films of UHMWPE

NASA Astrophysics Data System (ADS)

Rastogi, Sanjay

2013-03-01

Ultra High Molecular Weight Polyethylene (UHMWPE) having average molar mass greater than a million g/mol is an engineering polymer. Due to its light-weight, high abrasion resistance and biocompatibility it is used for demanding applications such as body armour, prostheses etc. At present, because of its high melt viscosity to achieve the uniaxial/biaxial properties in the form of fibers/films the polymer is processed via solution route where nearly 95wt% of the solvent is used to process 5wt% of the polymer. In past several attempts have been made to process the polymer without using any solvent. However, compared to the solvent processing route the achieved mechanical properties were rather poor. Here we show that by controlled synthesis it is feasible to obtain UHMWPE that could be processed free of solvent to make uniaxial tapes and biaxial films, having unprecedented mechanical properties, exceeding that of the solution spun fibers. We address some of the fundamental aspects of chemistry, physics, rheology and processing for the development of desired morphological features to achieve the ultimate mechanical properties in tapes and films. The paper will also address the metastable melt state obtained on melting of the disentangled crystals and its implication on rheology in linear and nonlinear viscoelastic region. Solid state NMR studies will be applied to establish disentangled state in solid state to the polymerisation conditions. References: Macromolecules 2011, 44(14), 5558-5568; Nature Materials 2005, 4, 635-641; Phys Rev Lett 2006, 96(21), 218303-218205. The authors acknowledge financial support by the Dutch Polymer Institute.

Low-viscosity hydroxypropylcellulose (HPC) grades SL and SSL: versatile pharmaceutical polymers for dissolution enhancement, controlled release, and pharmaceutical processing.

PubMed

Sarode, Ashish; Wang, Peng; Cote, Catherine; Worthen, David R

2013-03-01

Hydroxypropylcellulose (HPC)-SL and -SSL, low-viscosity hydroxypropylcellulose polymers, are versatile pharmaceutical excipients. The utility of HPC polymers was assessed for both dissolution enhancement and sustained release of pharmaceutical drugs using various processing techniques. The BCS class II drugs carbamazepine (CBZ), hydrochlorthiazide, and phenytoin (PHT) were hot melt mixed (HMM) with various polymers. PHT formulations produced by solvent evaporation (SE) and ball milling (BM) were prepared using HPC-SSL. HMM formulations of BCS class I chlorpheniramine maleate (CPM) were prepared using HPC-SL and -SSL. These solid dispersions (SDs) manufactured using different processes were evaluated for amorphous transformation and dissolution characteristics. Drug degradation because of HMM processing was also assessed. Amorphous conversion using HMM could be achieved only for relatively low-melting CBZ and CPM. SE and BM did not produce amorphous SDs of PHT using HPC-SSL. Chemical stability of all the drugs was maintained using HPC during the HMM process. Dissolution enhancement was observed in HPC-based HMMs and compared well to other polymers. The dissolution enhancement of PHT was in the order of SE>BM>HMM>physical mixtures, as compared to the pure drug, perhaps due to more intimate mixing that occurred during SE and BM than in HMM. Dissolution of CPM could be significantly sustained in simulated gastric and intestinal fluids using HPC polymers. These studies revealed that low-viscosity HPC-SL and -SSL can be employed to produce chemically stable SDs of poorly as well as highly water-soluble drugs using various pharmaceutical processes in order to control drug dissolution.

Electroless metal plating of plastics

DOEpatents

Krause, Lawrence J.

1986-01-01

Process for plating main group metals on aromatic polymers is carried out by the use of a nonaqueous solution of a salt of an alkali metal in a positive valence state and a main group metal in a negative valence state with contact between the solution and polymer providing a redox reaction causing the deposition of the main group metal and the reduction of the polymer. Products from the process exhibit useful decorative and electrical properties.

Electroless metal plating of plastics

DOEpatents

Krause, L.J.

1982-09-20

Process for plating main group metals on aromatic polymers is carried out by the use of a nonaqueous solution of a salt of an alkali metal in a positive valence state and a main group metal in a negative valence state with contact between the solution and polymer providing a redox reaction causing the deposition of the main group metal and the reduction of the polymer. Products from the process exhibit useful decorative and electrical properties.

Electroless metal plating of plastics

DOEpatents

Krause, Lawrence J.

1984-01-01

Process for plating main group metals on aromatic polymers is carried out by the use of a nonaqueous solution of a salt of an alkali metal in a positive valence state and a main group metal in a negative valence state with contact between the solution and polymer providing a redox reaction causing the deposition of the main group metal and the reduction of the polymer. Products from the process exhibit useful decorative and electrical properties.

Fatigue Behavior of a SiC/SiC Composite at 1000 deg C in Air and in Steam

DTIC Science & Technology

2010-12-01

SiC dual-layer interphase. The composite was manufactured by a Polymer Infiltration and Pyrolysis (PIP... Polymer Infiltration and Pyrolysis (PIP) process. A seal coat of SiC and elemental boron was applied to the test specimens after machining. The tensile...manufactured by a Polymer Infiltration and Pyrolysis (PIP) process. A seal coat of SiC and elemental boron was applied to the test specimens

High-performance vitrimers from commodity thermoplastics through dioxaborolane metathesis

NASA Astrophysics Data System (ADS)

Röttger, Max; Domenech, Trystan; van der Weegen, Rob; Breuillac, Antoine; Nicolaÿ, Renaud; Leibler, Ludwik

2017-04-01

Windmills, cars, and dental restoration demand polymer materials and composites that are easy to process, assemble, and recycle while exhibiting outstanding mechanical, thermal, and chemical resistance. Vitrimers, which are polymer networks able to shuffle chemical bonds through exchange reactions, could address these demands if they were prepared from existing plastics and processed with fast production rates and current equipment. We report the metathesis of dioxaborolanes, which is rapid and thermally robust, and use it to prepare vitrimers from polymers as different as poly(methyl methacrylate), polystyrene, and high-density polyethylene that, although permanently cross-linked, can be processed multiple times by means of extrusion or injection molding. They show superior chemical resistance and dimensional stability and can be efficiently assembled. The strategy is applicable to polymers with backbones made of carbon-carbon single bonds.

Piling-to-buckling transition in the drying process of polymer solution drop on substrate having a large contact angle.

PubMed

Kajiya, Tadashi; Nishitani, Eisuke; Yamaue, Tatsuya; Doi, Masao

2006-01-01

We studied the drying process of polymer solution drops placed on a substrate having a large contact angle with the drop. The drying process takes place in three stages. First, the droplet evaporates keeping the contact line fixed. Second, the droplet shrinks uniformly with receding contact line. Finally the contact line is pinned again, and the droplet starts to be deformed. The shape of the final polymer deposit changes from concave dot, to flat dot, and then to concave dot again with the increase of the initial polymer concentration. This shape change is caused by the gradual transition from the solute piling mechanism proposed by Deegan to the crust buckling mechanism proposed by de Gennes and Pauchard.

New polymers for low-gravity purification of cells by phase partitioning

NASA Technical Reports Server (NTRS)

Harris, J. M.

1983-01-01

A potentially powerful technique for separating different biological cell types is based on the partitioning of these cells between the immiscible aqueous phases formed by solution of certain polymers in water. This process is gravity-limited because cells sediment rather than associate with the phase most favored on the basis of cell-phase interactions. In the present contract we have been involved in the synthesis of new polymers both to aid in understanding the partitioning process and to improve the quality of separations. The prime driving force behind the design of these polymers is to produce materials which will aid in space experiments to separate important cell types and to study the partitioning process in the absence of gravity (i.e., in an equilibrium state).

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

NASA Technical Reports Server (NTRS)

Hergenrother, P. M. (Inventor)

1983-01-01

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.

Recent Advances in the Development of Processable High-Temperature POLYMERS1

NASA Astrophysics Data System (ADS)

Meador, Michael A.

1998-08-01

High-temperature polymers have found widespread use in aerospace and electronics applications. This review deals with recent developments in the chemistry of these materials that have led to improvements in processability and high-temperature stability.

Structure of Irreversibly Adsorbed Star Polymers

NASA Astrophysics Data System (ADS)

Akgun, Bulent; Aykan, Meryem Seyma; Canavar, Seda; Satija, Sushil K.; Uhrig, David; Hong, Kunlun

Formation of irreversibly adsorbed polymer chains on solid substrates have a huge impact on the wetting, glass transition, aging and polymer chain mobility in thin films. In recent years there has been many reports on the formation, kinetics and dynamics of these layers formed by linear homopolymers. Recent studies showed that by varying the number of polymer arms and arm molecular weight one can tune the glass transition temperature of thin polymer films. Using polymer architecture as a tool, the behavior of thin films can be tuned between the behavior of linear chains and soft colloids. We have studied the effect of polymer chain architecture on the structure of dead layer using X-ray reflectivity (XR) and atomic force microscopy. Layer thicknesses and densities of flattened and loosely adsorbed chains has been measured for linear, 4-arm, and 8-arm star polymers with identical total molecular weight as a function of substrate surface energy, annealing temperature and annealing time. Star polymers have been synthesized using anionic polymerization. XR measurements showed that 8-arm star PS molecules form the densest and the thickest dead layers among these three molecules.

Additives and method for controlling clathrate hydrates in fluid systems

DOEpatents

Sloan, Jr., Earle Dendy; Christiansen, Richard Lee; Lederhos, Joseph P.; Long, Jin Ping; Panchalingam, Vaithilingam; Du, Yahe; Sum, Amadeu Kun Wan

1997-01-01

Discussed is a process for preventing clathrate hydrate masses from detrimentally impeding the possible flow of a fluid susceptible to clathrate hydrate formation. The process is particularly useful in the natural gas and petroleum production, transportation and processing industry where gas hydrate formation can cause serious problems. Additives preferably contain one or more five member, six member and/or seven member cyclic chemical groupings. Additives include polymers having lactam rings. Additives can also contain polyelectrolytes that are believed to improve conformance of polymer additives through steric hinderance and/or charge repulsion. Also, polymers having an amide on which a C.sub.1 -C.sub.4 group is attached to the nitrogen and/or the carbonyl carbon of the amide may be used alone, or in combination with ring-containing polymers for enhanced effectiveness. Polymers having at least some repeating units representative of polymerizing at least one of an oxazoline, an N-substituted acrylamide and an N-vinyl alkyl amide are preferred.

Additives and method for controlling clathrate hydrates in fluid systems

DOEpatents

Sloan, E.D. Jr.; Christiansen, R.L.; Lederhos, J.P.; Long, J.P.; Panchalingam, V.; Du, Y.; Sum, A.K.W.

1997-06-17

Discussed is a process for preventing clathrate hydrate masses from detrimentally impeding the possible flow of a fluid susceptible to clathrate hydrate formation. The process is particularly useful in the natural gas and petroleum production, transportation and processing industry where gas hydrate formation can cause serious problems. Additives preferably contain one or more five member, six member and/or seven member cyclic chemical groupings. Additives include polymers having lactam rings. Additives can also contain polyelectrolytes that are believed to improve conformance of polymer additives through steric hindrance and/or charge repulsion. Also, polymers having an amide on which a C{sub 1}-C{sub 4} group is attached to the nitrogen and/or the carbonyl carbon of the amide may be used alone, or in combination with ring-containing polymers for enhanced effectiveness. Polymers having at least some repeating units representative of polymerizing at least one of an oxazoline, an N-substituted acrylamide and an N-vinyl alkyl amide are preferred.

Photochemical modification of polymeric materials and the polarization of light in ionomeric guest/host systems

NASA Astrophysics Data System (ADS)

Pan, Bo

Photochemical methods were introduced to develop important extrusion processes, through which polymers can either be functionalized or modified by altering molecular weight characteristics. Therefore, poly(methyl methacrylate) (PMMA) incorporated with a small amount of light-reactive functional groups was synthesized. These functional groups can be activated by UV irradiation in a post extrusion process to produce high molecular weight polymer and/or crosslinked polymer. Environmental stress cracking resistance of these polymers was examined and correlated to damping using dynamic mechanic analysis. To improve industrial reactive extrusion process of preparing maleic anhydride grafted polypropylene (MAR-g-PP), photografting was proposed and studied. Using benzophenone (BP) as the initiator, grafting efficiency was significantly improved compared to peroxide initiated grafting. Moreover, nearly constant conversion of maleic anhydride was observed in photografting. The high efficiency of benzophenone initiated photografting was attributed to the formation of the excited triplet state maleic anhydride. A rate constant of 6.0*109 M-1*sec-1 for the quenching of triplet state BP with MAH was obtained using laser photolysis spectroscopy. In a comparison, the hydrogen abstraction process from polypropylene by the triplet state BP molecules has a rate constant of 4.1*105 M-1*sec-1. In solution grafting with the use of benzene as the solvent, a facile triplet state energy transfer process may also occur leading to the formation of the excited triplet state MAH. Spectroscopic methods involving light were also used for the study of the guest-host interactions in polymer systems. The use of ionomers as the matrix for the oriented guest/host systems, cationic dye systems in particular, was shown to enhance polarization efficiency as well as dye uptake as comparing to conventional polymers, such as poly(vinyl alcohol). It was found that the dye molecules in carboxylated EVOH (EVOH-COONa) have higher degree of orientation than in EVOH, while polymer chain orientation is quite similar in these two polymers. The difference in the dye orientation was attributed to the ion-ion interactions between dye molecules and carboxylate groups of the modified polymer.

Blowing Polymer Bubbles in an Acoustic Levitator

NASA Technical Reports Server (NTRS)

Lee, M. C.

1985-01-01

In new manufacturing process, small gas-filled polymer shells made by injecting gas directly into acoustically levitated prepolymer drops. New process allows sufficient time for precise control of shell geometry. Applications foreseen in fabrication of deuterium/tritium-filled fusion targets and in pharmaceutical coatings. New process also useful in glass blowing and blow molding.

Azobenzene-based supramolecular polymers for processing MWCNTs.

PubMed

Maggini, Laura; Marangoni, Tomas; Georges, Benoit; Malicka, Joanna M; Yoosaf, K; Minoia, Andrea; Lazzaroni, Roberto; Armaroli, Nicola; Bonifazi, Davide

2013-01-21

Photothermally responsive supramolecular polymers containing azobenzene units have been synthesised and employed as dispersants for multi-walled carbon nanotubes (MWCNTs) in organic solvents. Upon triggering the trans-cis isomerisation of the supramolecular polymer intermolecular interactions between MWCNTs and the polymer are established, reversibly affecting the suspensions of the MWCNTs, either favouring it (by heating, i.e. cis→trans isomerisation) or inducing the CNTs' precipitation (upon irradiation, trans→cis isomerisation). Taking advantage of the chromophoric properties of the molecular subunits, the solubilisation/precipitation processes have been monitored by UV-Vis absorption spectroscopy. The structural properties of the resulting MWCNT-polymer hybrid materials have been thoroughly investigated via thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and atomic force microscopy (AFM) and modelled with molecular dynamics simulations.

Isothermal aging effects on PMR-15 resin

NASA Technical Reports Server (NTRS)

Bowles, Kenneth J.; Jayne, Douglas; Leonhardt, Todd A.

1992-01-01

Specimens of PMR-15 polyimide neat resin were aged in air at temperatures of 288, 316, and 343 C. Weight losses and dimensional changes were monitored during the course of the exposure time. Physical changes were also observed by optical and electron microscopy. It was found that polyimide polymer degradation occurred within a thin surface layer that developed and grew during thermal aging. The cores of the polymer specimens were protected from oxidative degradation, and they were relatively unchanged by the thermal treatment. Surface cracking was observed at 343 C and was probably due to an interaction between voids and stresses that developed in the surface layer.

Development of PVA/gelatin nanofibrous scaffolds for Tissue Engineering via electrospinning

NASA Astrophysics Data System (ADS)

Perez-Puyana, V.; Jiménez-Rosado, M.; Romero, A.; Guerrero, A.

2018-03-01

The electrospinning process is an emerging and relatively easy technique to prepare three-dimensional matrices with micro- and nanofibers. To achieve it, aqueous polymer solutions from synthetic or natural polymers are used. PVA was selected as polymer and gelatin because of its biocompatibility and biodegradability. A complete characterization of the polymeric solutions (density, surface tension, etc) was previously performed. Subsequently, a standard electrospinning process (15 kV, 0.4 ml h-1 and 10 cm) was carried out to obtain scaffolds. The influence of the polymer concentration and the protein addition was observed by performing FTIR analyses and studied by analyzing the water contact angle and SEM images.

Nanocrystal/sol-gel nanocomposites

DOEpatents

Klimov, Victor L.; Petruska, Melissa A.

2010-05-25

The present invention is directed to a process for preparing a solid composite having colloidal nanocrystals dispersed within a sol-gel matrix, the process including admixing colloidal nanocrystals with an amphiphilic polymer including hydrophilic groups selected from the group consisting of --COOH, --OH, --SO.sub.3H, --NH.sub.2, and --PO.sub.3H.sub.2 within a solvent to form an alcohol-soluble colloidal nanocrystal-polymer complex, admixing the alcohol-soluble colloidal nanocrystal-polymer complex and a sol-gel precursor material, and, forming the solid composite from the admixture. The present invention is also directed to the resultant solid composites and to the alcohol-soluble colloidal nanocrystal-polymer complexes.

Chemistry of the metal-polymer interfacial region.

PubMed

Leidheiser, H; Deck, P D

1988-09-02

In many polymer-metal systems, chemical bonds are formed that involve metal-oxygen-carbon complexes. Infrared and Mössbauer spectroscopic studies indicate that carboxylate groups play an important role in some systems. The oxygen sources may be the polymer, the oxygen present in the oxide on the metal surface, or atmospheric oxygen. Diffusion of metal ions from the substrate into the polymer interphase may occur in some systems that are cured at elevated temperatures. It is unclear whether a similar, less extensive diffusion occurs over long time periods in systems maintained at room temperature. The interfacial region is dynamic, and chemical changes occur with aging at room temperature. Positron annihilation spectroscopy may have application to characterizing the voids at the metal-polymer interface.

Direct Printing of Graphene onto Plastic Substrates.

NASA Astrophysics Data System (ADS)

Hines, Daniel; Lock, Evgeniya; Walton, Scott; Baraket, Mira; Laskoski, Matthew; Mulvaney, Shawn; Sheehan, Paul; Lee, Woo; Robinson, Jeremy

2011-03-01

Graphene films have been synthesized on metal foils using CVD growth and have the potential to be compatible with roll-to-roll printing. To be usable in electronic devices, these films need to be removed from the metallic substrate. Currently this is accomplished by spin coating a polymer film over the graphene and chemically etching away the metal substrate. We have developed a direct printing method that allows graphene films to be printed off the metal substrate onto a polymer substrate. This printing process does not generate chemical waste, is compatible with roll-to-toll processing and renders the metal foil reusable. Adhesion of the graphene film to the polymer substrate is established by attaching perfluorophenylazides (PFPA) azide linker molecules to a plasma activated polymer surface. The transfer printing was performed by placing the PFPA treated polymer surface in contact with a graphene covered Cu foil and heating under pressure. Graphene films successfully printed onto a polystyrene substrate have been characterized by Raman spectroscopy and electrical measurements revealed the presence of Gr on the polymer surface. Details of the printing process along with characteristics of the graphene film after printing will be presented.

Classroom Demonstrations of Polymer Principles Part II. Polymer Formation.

ERIC Educational Resources Information Center

Rodriguez, F.; And Others

1987-01-01

This is part two in a series on classroom demonstrations of polymer principles. Described is how large molecules can be assembled from subunits (the process of polymerization). Examples chosen include both linear and branched or cross-linked molecules. (RH)

Materials, device, and interface engineering to improve polymer-based solar cells

NASA Astrophysics Data System (ADS)

Hau, Steven Kin

The continued depletion of fossil fuel resources has lead to the rise in energy production costs which has lead to the search for an economically viable alternative energy source. One alternative of particular interest is solar energy. A promising alternative to inorganic materials is organic semiconductor polymer solar cells due to their advantages of being cheaper, light weight, flexible and made into large areas by roll-to-roll processing. In this dissertation, an integrated approach is taken to improve the overall performance of polymer-based solar cells by the development of new polymer materials, device architectures, and interface engineering of the contacts between layers. First, a new class of metallated conjugated polymers is explored as potential solar cell materials. Systematic modifications to the molecular units on the main chain of amorphous metallated Pt-polymers show a correlation that improving charge carrier mobility also improves solar cell performance leading to mobilities as high as 1 x 10-2 cm2/V·s and efficiencies as high as 4.1%. Second, an inverted device architecture using a more air stable electrode (Ag) is demonstrated to improve the ambient stability of unencapsulated P3HT:PCBM devices showing over 80% efficiency retention after 40 days of exposure. To further demonstrate the potential for roll-to-roll processing of polymer solar cells, solution processed Ag-nanoparticles were used to replace the vacuum deposited Ag anode electrode for inverted solar cells showing efficiencies as high as 3%. In addition, solution processed polymer based electrodes were demonstrated as a replacement to the expensive and brittle indium tin oxide showing efficiencies of 3% on flexible substrate solar cells. Third, interface engineering of the n-type (high temperature sol-gel processed TiO2 or ZnO, low temperature processed ZnO nanoparticles) electron selective metal oxide contacts in inverted solar cells with self-assembled monolayers (SAM) show improved device performance. Modifying the n-type layer in inverted cells with C60-SAMs containing different anchoring groups leads to an improvement in photocurrent density and fill factor leading to efficiencies as high as 4.9%.

Evolution in the charge injection efficiency of evaporated Au contacts on a molecularly doped polymer

NASA Astrophysics Data System (ADS)

Ioannidis, Andronique; Facci, John S.; Abkowitz, Martin A.

1998-08-01

Injection efficiency from evaporated Au contacts on a molecularly doped polymer (MDP) system has been previously observed to evolve from blocking to ohmic over time. In the present article this contact forming phenomenon is analyzed in detail. The initially blocking nature of the Au contact is in contrast with that expected from the relative workfunctions of Au and of the polymer which suggest Au should inject holes efficiently. It is also in apparent contrast to a differently prepared interface of the same materials. The phenomenon is not unique to this interface, having been confirmed also for evaporated Ag and mechanically made liquid Hg contacts on the same MDP. The MDP is a disordered solid state solution of electroactive triarylamine hole transporting TPD molecules in a polycarbonate matrix. The trap-free hole-transport MDP provides a model system for the study of metal/polymer interfaces by enabling the use of a recently developed technique that gives a quantitative measure of contact injection efficiency. The technique combines field-dependent steady state injection current measurements at a contact under test with time-of-flight (TOF) mobility measurements made on the same sample. In the present case, MDP films were prepared with two top vapor-deposited contacts, one of Au (test contact) and one of Al (for TOF), and a bottom carbon-loaded polymer electrode which is known to be ohmic for hole injection. The samples were aged at various temperatures below the glass transition of the MDP (85 °C) and the evolution of current versus field and capacitance versus frequency behaviors are followed in detail over time and analyzed. Control measurements ensure that the evolution of the electrical properties is due to the Au/polymer interface behavior and not the bulk. All evaporated Au contacts eventually achieved ohmic injection. The evaporated Au/MDP interface was also investigated by transmission electron microscopy as a function of time and showed no evidence of Au interdiffusion in the MDP layer, remaining abrupt to within ˜10 Å over the course of the evolution in injection efficiency. Mechanisms related to Au penetration into the MDP are therefore unlikely. Rapid sequence data acquisition enabled the detection of two main processes in the injection evolution. The evolving injection efficiency is very well fit by two exponentials, enabling the characterization of time and temperature dependence of the evolution processes.

Vogel-Fulcher dependence of relaxation rates in a nematic monomer and elastomer

NASA Astrophysics Data System (ADS)

Shenoy, D.; Filippov, S.; Aliev, F.; Keller, P.; Thomsen, D.; Ratna, B.

2000-12-01

Dielectric relaxation spectroscopy is used to study the relaxation processes in a nematic monomer and the corresponding cross-linked polymer nematic liquid crystal (elastomer). In the frequency window 10 mHz to 2 GHz the monomer liquid crystal shows a single relaxation whereas the polymer exhibits three relaxation processes, two of which are quantitatively analyzed. The temperature dependence of relaxation times in both the monomer and polymer follows a Vogel-Fulcher behavior. The relaxation processes are identified with specific molecular motions and activation energies are calculated in a linear approximation for comparison with literature data.

Water/alcohol soluble conjugated polymers as highly efficient electron transporting/injection layer in optoelectronic devices.

PubMed

Huang, Fei; Wu, Hongbin; Cao, Yong

2010-07-01

Water/alcohol soluble conjugated polymers (WSCPs) can be processed from water or other polar solvents, which offer good opportunities to avoid interfacial mixing upon fabrication of multilayer polymer optoelectronic devices by solution processing, and can dramatically improve charge injection from high work-function metal cathode resulting in greatly enhancement of the device performance. In this critical review, the authors provide a brief review of recent developments in this field, including the materials design, functional principles, and their unique applications as interface modification layer in solution-processable multilayer optoelectronic devices (135 references).

Thermoplastic coating of carbon fibers

NASA Technical Reports Server (NTRS)

Edie, D. D.; Lickfield, G. C.; Drews, M. J.; Ellison, M. S.; Gantt, B. W.

1989-01-01

A process is being developed which evenly coats individual carbon fibers with thermoplastic polymers. In this novel, continuous coating process, the fiber tow bundle is first spread cover a series of convex rollers and then evenly coated with a fine powder of thermoplastic matrix polymer. Next, the fiber is heated internally by passing direct current through the powder coated fiber. The direct current is controlled to allow the carbon fiber temperature to slightly exceed the flow temperature of the matrix polymer. Analysis of the thermoplastic coated carbon fiber tows produced using this continuous process indicates that 30 to 70 vol pct fiber prepregs can be obtained.

Extensional Rheology Experiment Developed to Investigate the Rheology of Dilute Polymer Solutions in Microgravity

NASA Technical Reports Server (NTRS)

Logsdon, Kirk A.

2001-01-01

A fundamental characteristic of fluid is viscosity; that is, the fluid resists forces that cause it to flow. This characteristic, or parameter, is used by manufacturers and end-users to describe the physical properties of a specific material so that they know what to expect when a material, such as a polymer, is processed through an extruder, a film blower, or a fiber-spinning apparatus. Normally, researchers will report a shear viscosity that depends on the rate of an imposed shearing flow. Although this type of characterization is sufficient for some processes, simple shearing experiments do not provide a complete picture of what a processor may expect for all materials. Extensional stretching flows are common in many polymer-processing operations such as extrusion, blow molding, and fiber spinning. Therefore, knowledge of the complete rheological (ability to flow and be deformed) properties of the polymeric fluid being processed is required to accurately predict and account for the flow behavior. In addition, if numerical simulations are ever able to serve as a priori design tools for optimizing polymer processing operations such as those described above, an accurate knowledge of the extensional viscosity of a polymer system and its variation with temperature, concentration, molecular weight, and strain rate is critical.

Study on dissolution behavior of polymer-bound and polymer-blended photo-acid generator (PAG) resists

NASA Astrophysics Data System (ADS)

Yamamoto, Hiroki; Kozawa, Takahiro; Tagawa, Seiichi

2013-03-01

The requirements for the next generation resist materials are so challenging that it is indispensable for feasibility of EUV lithography to grasp basic chemistry of resist matrices in all stage of resist processes. Under such circumstances, it is very important to know dissolution characteristics of the resist film into alkaline developer though the dissolution of exposed area of resist films in alkaline developer to form a pattern is a complex reactive process. In this study, the influence of EUV and KrF exposure on the dissolution behavior of polymer bound PAG and polymer blended PAG was studied in detail using quartz crystal microbalance (QCM) methods. The difference in swelling formation between KrF and EUV exposure was observed. It is likely that difference of reaction mechanism induces the difference of these swelling. Also, it is observed that the swelling of polymer-bound PAG is less than that of polymer blended PAG in both KrF and EUV exposure. This result indicates that polymer-bound PAG suppresses swelling very well and showed an excellent performance. Actually, the developed polymer bound-PAG resist showed an excellent performance (half pitch 50 nm line and space pattern). Thus, polymer bound PAG is one of the promising candidate for 16 nm EUV resist.

Nanopatterns by phase separation of patterned mixed polymer monolayers

DOEpatents

Huber, Dale L; Frischknecht, Amalie

2014-02-18

Micron-size and sub-micron-size patterns on a substrate can direct the self-assembly of surface-bonded mixed polymer brushes to create nanoscale patterns in the phase-separated mixed polymer brush. The larger scale features, or patterns, can be defined by a variety of lithographic techniques, as well as other physical and chemical processes including but not limited to etching, grinding, and polishing. The polymer brushes preferably comprise vinyl polymers, such as polystyrene and poly(methyl methacrylate).

Localized Enzymatic Degradation of Polymers: Physics and Scaling Laws

NASA Astrophysics Data System (ADS)

Lalitha Sridhar, Shankar; Vernerey, Franck

2018-03-01

Biodegradable polymers are naturally abundant in living matter and have led to great advances in controlling environmental pollution due to synthetic polymer products, harnessing renewable energy from biofuels, and in the field of biomedicine. One of the most prevalent mechanisms of biodegradation involves enzyme-catalyzed depolymerization by biological agents. Despite numerous studies dedicated to understanding polymer biodegradation in different environments, a simple model that predicts the macroscopic behavior (mass and structural loss) in terms of microphysical processes (enzyme transport and reaction) is lacking. An interesting phenomenon occurs when an enzyme source (released by a biological agent) attacks a tight polymer mesh that restricts free diffusion. A fuzzy interface separating the intact and fully degraded polymer propagates away from the source and into the polymer as the enzymes diffuse and react in time. Understanding the characteristics of this interface will provide crucial insight into the biodegradation process and potential ways to precisely control it. In this work, we present a centrosymmetric model of biodegradation by characterizing the moving fuzzy interface in terms of its speed and width. The model predicts that the characteristics of this interface are governed by two time scales, namely the polymer degradation and enzyme transport times, which in turn depend on four main polymer and enzyme properties. A key finding of this work is simple scaling laws that can be used to guide biodegradation of polymers in different applications.

Introducing Students to Feedstock Recycling of End-of-Life Silicones via a Low-Temperature, Iron-Catalyzed Depolymerization Process

ERIC Educational Resources Information Center

Do¨hlert, Peter; Weidauer, Maik; Peifer, Raphael; Kohl, Stephan; Enthaler, Stephan

2015-01-01

The straightforward large-scale synthesis and the ability to adjust the properties of polymers make polymers very attractive materials. Polymers have been used in numerous applications and an increased demand is foreseeable. However, a serious issue is the accumulation of enormous amounts of end-of-life polymers, which are currently recycled by…

Failure mechanism of the polymer infiltration of carbon nanotube forests

NASA Astrophysics Data System (ADS)

Buchheim, Jakob; Park, Hyung Gyu

2016-11-01

Polymer melt infiltration is one of the feasible methods for manufacturing filter membranes out of carbon nanotubes (CNTs) on large scales. Practically, however, its process suffers from low yields, and the mechanism behind this failure is rather poorly understood. Here, we investigate a failure mechanism of polymer melt infiltration of vertical aligned (VA-) CNTs. In penetrating the VA-CNT interstices, polymer melts exert a capillarity-induced attractive force laterally on CNTs at the moving meniscus, leading to locally agglomerated macroscale bunches. Such a large configurational change can deform and distort individual CNTs so much as to cause buckling or breakdown of the alignment. In view of membrane manufacturing, this irreversible distortion of nanotubes is detrimental, as it could block the transport path of the membranes. The failure mechanism of the polymer melt infiltration is largely attributed to steric hindrance and an energy penalty of confined polymer chains. Euler beam theory and scaling analysis affirm that CNTs with low aspect ratio, thick walls and sparse distribution can maintain their vertical alignment. Our results can enrich a mechanistic understanding of the polymer melt infiltration process and offer guidelines to the facile large-scale manufacturing of the CNT-polymer filter membranes.

Mechanically triggered heterolytic unzipping of a low-ceiling-temperature polymer

NASA Astrophysics Data System (ADS)

Diesendruck, Charles E.; Peterson, Gregory I.; Kulik, Heather J.; Kaitz, Joshua A.; Mar, Brendan D.; May, Preston A.; White, Scott R.; Martínez, Todd J.; Boydston, Andrew J.; Moore, Jeffrey S.

2014-07-01

Biological systems rely on recyclable materials resources such as amino acids, carbohydrates and nucleic acids. When biomaterials are damaged as a result of aging or stress, tissues undergo repair by a depolymerization-repolymerization sequence of remodelling. Integration of this concept into synthetic materials systems may lead to devices with extended lifetimes. Here, we show that a metastable polymer, end-capped poly(o-phthalaldehyde), undergoes mechanically initiated depolymerization to revert the material to monomers. Trapping experiments and steered molecular dynamics simulations are consistent with a heterolytic scission mechanism. The obtained monomer was repolymerized by a chemical initiator, effectively completing a depolymerization-repolymerization cycle. By emulating remodelling of biomaterials, this model system suggests the possibility of smart materials where aging or mechanical damage triggers depolymerization, and orthogonal conditions regenerate the polymer when and where necessary.

Chromatography, solid-phase extraction, and capillary electrochromatography with MIPs.

PubMed

Tóth, Blanka; Horvai, George

2012-01-01

Most analytical applications of molecularly imprinted polymers are based on their selective adsorption properties towards the template or its analogs. In chromatography, solid phase extraction and electrochromatography this adsorption is a dynamic process. The dynamic process combined with the nonlinear adsorption isotherm of the polymers and other factors results in complications which have limited the success of imprinted polymers. This chapter explains these problems and shows many examples of successful applications overcoming or avoiding the problems.

Controlled release from drug microparticles via solventless dry-polymer coating.

PubMed

Capece, Maxx; Barrows, Jason; Davé, Rajesh N

2015-04-01

A novel solvent-less dry-polymer coating process employing high-intensity vibrations avoiding the use of liquid plasticizers, solvents, binders, and heat treatments is utilized for the purpose of controlled release. The main hypothesis is that such process having highly controllable processing intensity and time may be effective for coating particularly fine particles, 100 μm and smaller via exploiting particle interactions between polymers and substrates in the dry state, while avoiding breakage yet achieving conformal coating. The method utilizes vibratory mixing to first layer micronized polymer onto active pharmaceutical ingredient (API) particles by virtue of van der Waals forces and to subsequently mechanically deform the polymer into a continuous film. As a practical example, ascorbic acid and ibuprofen microparticles, 50-500 μm, are coated with the polymers polyethylene wax or carnauba wax, a generally recognized as safe material, resulting in controlled release on the order of seconds to hours. As a novelty, models are utilized to describe the coating layer thickness and the controlled-release behavior of the API, which occurs because of a diffusion-based mechanism. Such modeling would allow the design and control of the coating process with application for the controlled release of microparticles, particularly those less than 100 μm, which are difficult to coat by conventional solvent coating methods. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

The analysis of thermoplastic characteristics of special polymer sulfur composite

NASA Astrophysics Data System (ADS)

Książek, Mariusz

2017-01-01

Specific chemical environments step out in the industry objects. Portland cement composites (concrete and mortar) were impregnated by using the special polymerized sulfur and technical soot as a filler (polymer sulfur composite). Sulfur and technical soot was applied as the industrial waste. Portland cement composites were made of the same aggregate, cement and water. The process of special polymer sulfur composite applied as the industrial waste is a thermal treatment process in the temperature of about 150-155°C. The result of such treatment is special polymer sulfur composite in a liquid state. This paper presents the plastic constants and coefficients of thermal expansion of special polymer sulfur composites, with isotropic porous matrix, reinforced by disoriented ellipsoidal inclusions with orthotropic symmetry of the thermoplastic properties. The investigations are based on the stochastic differential equations of solid mechanics. A model and algorithm for calculating the effective characteristics of special polymer sulfur composites are suggested. The effective thermoplastic characteristics of special polymer sulfur composites, with disoriented ellipsoidal inclusions, are calculated in two stages: First, the properties of materials with oriented inclusions are determined, and then effective constants of a composite with disoriented inclusions are determined on the basis of the Voigt or Rice scheme. A brief summary of new products related to special polymer sulfur composites is given as follows: Impregnation, repair, overlays and precast polymer concrete will be presented. Special polymer sulfur as polymer coating impregnation, which has received little attention in recent years, currently has some very interesting applications.

Molecular Approach to Conjugated Polymers with Biomimetic Properties.

PubMed

Baek, Paul; Voorhaar, Lenny; Barker, David; Travas-Sejdic, Jadranka

2018-06-13

The field of bioelectronics involves the fascinating interplay between biology and human-made electronics. Applications such as tissue engineering, biosensing, drug delivery, and wearable electronics require biomimetic materials that can translate the physiological and chemical processes of biological systems, such as organs, tissues. and cells, into electrical signals and vice versa. However, the difference in the physical nature of soft biological elements and rigid electronic materials calls for new conductive or electroactive materials with added biomimetic properties that can bridge the gap. Soft electronics that utilize organic materials, such as conjugated polymers, can bring many important features to bioelectronics. Among the many advantages of conjugated polymers, the ability to modulate the biocompatibility, solubility, functionality, and mechanical properties through side chain engineering can alleviate the issues of mechanical mismatch and provide better interface between the electronics and biological elements. Additionally, conjugated polymers, being both ionically and electrically conductive through reversible doping processes provide means for direct sensing and stimulation of biological processes in cells, tissues, and organs. In this Account, we focus on our recent progress in molecular engineering of conjugated polymers with tunable biomimetic properties, such as biocompatibility, responsiveness, stretchability, self-healing, and adhesion. Our approach is general and versatile, which is based on functionalization of conjugated polymers with long side chains, commonly polymeric or biomolecules. Applications for such materials are wide-ranging, where we have demonstrated conductive, stimuli-responsive antifouling, and cell adhesive biointerfaces that can respond to external stimuli such as temperature, salt concentration, and redox reactions, the processes that in turn modify and reversibly switch the surface properties. Furthermore, utilizing the advantageous chemical, physical, mechanical and functional properties of the grafts, we progressed into grafting of the long side chains onto conjugated polymers in solution, with the vision of synthesizing solution-processable conjugated graft copolymers with biomimetic functionalities. Examples of the developed materials to date include rubbery and adhesive photoluminescent plastics, biomolecule-functionalized electrospun biosensors, thermally and dually responsive photoluminescent conjugated polymers, and tunable self-healing, adhesive, and stretchable strain sensors, advanced functional biocidal polymers, and filtration membranes. As outlined in these examples, the applications of these biomimetic, conjugated polymers are still in the development stage toward truly printable, organic bioelectronic devices. However, in this Account, we advocate that molecular engineering of conjugated polymers is an attractive approach to a versatile class of organic electronics with both ionic and electrical conductivity as well as mechanical properties required for next-generation bioelectronics.

Reverse Aging of Composite Materials for Aeronautical Applications

NASA Astrophysics Data System (ADS)

lannone, Michele

2008-08-01

Hygro-thermal ageing of polymer matrix composite materials is a major issue for all the aeronautical structures. For carbon-epoxy composites generally used in aeronautical applications the major effect of ageing is the humidity absorption, which induces a plasticization effect, generally decreasing Tg and elastic moduli, and finally design allowables. A thermodynamical and kinetic study has been performed, aimed to establish a program of periodic heating of the composite part, able to reversing the ageing effect by inducing water desorption. The study was founded on a simple model based on Fick's law, coupled with a concept of "relative saturation coefficient" depending on the different temperature of the composite part and the environment. The behaviour of some structures exposed to humidity and "reverse aged" by heating has been virtually tested. The conclusion of the study allowed to issue a specific patent application for aeronautical structures to be designed on the basis of a "humidity free" concept which allows the use of higher design allowables; having as final results lighter composite structures with a simplified certification process.

Polymer/Silicate Nanocomposites Developed for Improved Thermal Stability and Barrier Properties

NASA Technical Reports Server (NTRS)

Campbell, Sandi G.

2001-01-01

The nanoscale reinforcement of polymers is becoming an attractive means of improving the properties and stability of polymers. Polymer-silicate nanocomposites are a relatively new class of materials with phase dimensions typically on the order of a few nanometers. Because of their nanometer-size features, nanocomposites possess unique properties typically not shared by more conventional composites. Polymer-layered silicate nanocomposites can attain a certain degree of stiffness, strength, and barrier properties with far less ceramic content than comparable glass- or mineral-reinforced polymers. Reinforcement of existing and new polyimides by this method offers an opportunity to greatly improve existing polymer properties without altering current synthetic or processing procedures.

Supercritical fluid processing: opportunities for new resist materials and processes

NASA Astrophysics Data System (ADS)

Gallagher-Wetmore, Paula M.; Ober, Christopher K.; Gabor, Allen H.; Allen, Robert D.

1996-05-01

Over the past two decades supercritical fluids have been utilized as solvents for carrying out separations of materials as diverse as foods, polymers, pharmaceuticals, petrochemicals, natural products, and explosives. More recently they have been used for non-extractive applications such as recrystallization, deposition, impregnation, surface modification, and as a solvent alternative for precision parts cleaning. Today, supercritical fluid extraction is being practiced in the foods and beverage industries; there are commercial plants for decaffeinating coffee and tea, extracting beer flavoring agents from hops, and separating oils and oleoresins from spices. Interest in supercritical fluid processing of polymers has grown over the last ten years, and many new purification, fractionation, and even polymerization techniques have emerged. One of the most significant motivations for applying this technology to polymers has been increased performance demands. More recently, with increasing scrutiny of traditional solvents, supercritical fluids, and in particular carbon dioxide, are receiving widespread attention as 'environmentally conscious' solvents. This paper describes several examples of polymers applications, including a few involving photoresists, which demonstrate that as next- generation advanced polymer systems emerge, supercritical fluids are certain to offer advantages as cutting edge processing tools.

Wetting of polymer melts on coated and uncoated steel surfaces

NASA Astrophysics Data System (ADS)

Vera, Julie; Contraires, Elise; Brulez, Anne-Catherine; Larochette, Mathieu; Valette, Stéphane; Benayoun, Stéphane

2017-07-01

A comparative study of the wetting of three different commercial polymer melts on various coated and uncoated steel surfaces is described in this report. The wettability of steel and coatings (three different titanium nitride coatings, TiN, TiNOx, TiNOy, a chromium coating, CrN, and a diamond-like carbon coating, DLC) used for mold in polymer processing is determined at different temperatures between 25 °C and 120 °C. Contact angle measurements of melted polypropylene (PP), Acrylonitrile Butadiene Styrene (ABS) and Polycarbonate (PC) on steel and on the different coatings were performed to investigate the wetting behavior under closer-to-processing conditions. Recommendations for good measurement conditions were proposed. Moreover, the surface free energy of each melt polymer was determined. The works of adhesion between all polymers and all substrates were established. Among all tested polymers, the lowest value of the works of adhesion is calculated for ABS and for PC thereafter, and the highest value is calculated for PP. These results will be particularly important for such applications as determining the extent to which these polymers can contribute to the replication quality in injection molding.

Mechanistic modelling of drug release from a polymer matrix using magnetic resonance microimaging.

PubMed

Kaunisto, Erik; Tajarobi, Farhad; Abrahmsen-Alami, Susanna; Larsson, Anette; Nilsson, Bernt; Axelsson, Anders

2013-03-12

In this paper a new model describing drug release from a polymer matrix tablet is presented. The utilization of the model is described as a two step process where, initially, polymer parameters are obtained from a previously published pure polymer dissolution model. The results are then combined with drug parameters obtained from literature data in the new model to predict solvent and drug concentration profiles and polymer and drug release profiles. The modelling approach was applied to the case of a HPMC matrix highly loaded with mannitol (model drug). The results showed that the drug release rate can be successfully predicted, using the suggested modelling approach. However, the model was not able to accurately predict the polymer release profile, possibly due to the sparse amount of usable pure polymer dissolution data. In addition to the case study, a sensitivity analysis of model parameters relevant to drug release was performed. The analysis revealed important information that can be useful in the drug formulation process. Copyright © 2013 Elsevier B.V. All rights reserved.

Synthesis of surface molecular imprinted polymers based on carboxyl-modified silica nanoparticles with the selective detection of dibutyl phthalate from tap water samples

NASA Astrophysics Data System (ADS)

Xu, Wanzhen; Zhang, Xiaoming; Huang, Weihong; Luan, Yu; Yang, Yanfei; Zhu, Maiyong; Yang, Wenming

2017-12-01

In this work, the molecular imprinted polymers were synthesized with the low monomer concentrations for dibutyl phthalate (DBP). The polymers were prepared over carboxyl-modified silica nanoparticle, which used methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the cross-linker agent and azoisobutyronitrile as the initiator in the process of preparation. Various measures were used to characterize the structure and morphology in order to get the optimal polymer. The characterization results show that the optimal polymer has suitable features for further adsorption process. And adsorption capacity experiments were evaluated to analyze its adsorption performance, through adsorption isotherms/kinetics, selectivity adsorption and desorption and regeneration experiments. These results showed that the molecular imprinted polymers had a short equilibrium time about 60 min and high stability with 88% after six cycles. Furthermore, the molecular imprinted polymers were successfully applied to remove dibutyl phthalate. The concentration range was 5.0-30.0 μmol L-1, and the limit of detection was 0.06 μmol L-1 in tap water samples.

Rotationally Molded Liquid Crystalline Polymers

NASA Technical Reports Server (NTRS)

Rogers, Martin; Stevenson, Paige; Scribben, Eric; Baird, Donald; Hulcher, Bruce

2002-01-01

Rotational molding is a unique process for producing hollow plastic parts. Rotational molding offers advantages of low cost tooling and can produce very large parts with complicated shapes. Products made by rotational molding include water tanks with capacities up to 20,000 gallons, truck bed liners, playground equipment, air ducts, Nylon fuel tanks, pipes, toys, stretchers, kayaks, pallets, and many others. Thermotropic liquid crystalline polymers are an important class of engineering resins employed in a wide variety of applications. Thermotropic liquid crystalline polymers resins are composed of semi-rigid, nearly linear polymeric chains resulting in an ordered mesomorphic phase between the crystalline solid and the isotropic liquid. Ordering of the rigid rod-like polymers in the melt phase yields microfibrous, self-reinforcing polymer structures with outstanding mechanical and thermal properties. Rotational molding of liquid crystalline polymer resins results in high strength and high temperature hollow structures useful in a variety of applications. Various fillers and reinforcements can potentially be added to improve properties of the hollow structures. This paper focuses on the process and properties of rotationally molded liquid crystalline polymers.

Experiment Research on Hot-Rolling Processing of Nonsmooth Pit Surface.

PubMed

Gu, Yun-Qing; Fan, Tian-Xing; Mou, Jie-Gang; Yu, Wei-Bo; Zhao, Gang; Wang, Evan

2016-01-01

In order to achieve the nonsmooth surface drag reduction structure on the inner polymer coating of oil and gas pipelines and improve the efficiency of pipeline transport, a structural model of the machining robot on the pipe inner coating is established. Based on machining robot, an experimental technique is applied to research embossing and coating problems of rolling-head, and then the molding process rules under different conditions of rolling temperatures speeds and depth are analyzed. Also, an orthogonal experiment analysis method is employed to analyze the different effects of hot-rolling process apparatus on the embossed pits morphology and quality of rolling. The results also reveal that elevating the rolling temperature or decreasing the rolling speed can also improve the pit structure replication rates of the polymer coating surface, and the rolling feed has little effect on replication rates. After the rolling-head separates from the polymer coating, phenomenon of rebounding and refluxing of the polymer coating occurs, which is the reason of inability of the process. A continuous hot-rolling method for processing is used in the robot and the hot-rolling process of the processing apparatus is put in a dynamics analysis.

Experiment Research on Hot-Rolling Processing of Nonsmooth Pit Surface

PubMed Central

Gu, Yun-qing; Fan, Tian-xing; Mou, Jie-gang; Yu, Wei-bo; Zhao, Gang; Wang, Evan

2016-01-01

In order to achieve the nonsmooth surface drag reduction structure on the inner polymer coating of oil and gas pipelines and improve the efficiency of pipeline transport, a structural model of the machining robot on the pipe inner coating is established. Based on machining robot, an experimental technique is applied to research embossing and coating problems of rolling-head, and then the molding process rules under different conditions of rolling temperatures speeds and depth are analyzed. Also, an orthogonal experiment analysis method is employed to analyze the different effects of hot-rolling process apparatus on the embossed pits morphology and quality of rolling. The results also reveal that elevating the rolling temperature or decreasing the rolling speed can also improve the pit structure replication rates of the polymer coating surface, and the rolling feed has little effect on replication rates. After the rolling-head separates from the polymer coating, phenomenon of rebounding and refluxing of the polymer coating occurs, which is the reason of inability of the process. A continuous hot-rolling method for processing is used in the robot and the hot-rolling process of the processing apparatus is put in a dynamics analysis. PMID:27022235

Thermoelectric plastics: from design to synthesis, processing and structure–property relationships

PubMed Central

Kroon, Renee; Mengistie, Desalegn Alemu; Kiefer, David; Hynynen, Jonna; Ryan, Jason D.; Yu, Liyang

2016-01-01

Thermoelectric plastics are a class of polymer-based materials that combine the ability to directly convert heat to electricity, and vice versa, with ease of processing. Potential applications include waste heat recovery, spot cooling and miniature power sources for autonomous electronics. Recent progress has led to surging interest in organic thermoelectrics. This tutorial review discusses the current trends in the field with regard to the four main building blocks of thermoelectric plastics: (1) organic semiconductors and in particular conjugated polymers, (2) dopants and counterions, (3) insulating polymers, and (4) conductive fillers. The design and synthesis of conjugated polymers that promise to show good thermoelectric properties are explored, followed by an overview of relevant structure–property relationships. Doping of conjugated polymers is discussed and its interplay with processing as well as structure formation is elucidated. The use of insulating polymers as binders or matrices is proposed, which permit the adjustment of the rheological and mechanical properties of a thermoelectric plastic. Then, nanocomposites of conductive fillers such as carbon nanotubes, graphene and inorganic nanowires in a polymer matrix are introduced. A case study examines poly(3,4-ethylenedioxythiophene) (PEDOT) based materials, which up to now have shown the most promising thermoelectric performance. Finally, a discussion of the advantages provided by bulk architectures e.g. for wearable applications highlights the unique advantages that thermoelectric plastics promise to offer. PMID:27385496

40 CFR 723.250 - Polymers.

Code of Federal Regulations, 2010 CFR

2010-07-01

... functional group. Fluorotelomers means the products of telomerization, which is the reaction of a telogen... relevant polymer-forming reaction used for the particular process. Monomer Unit means the reacted form of... monomer units but which, under the relevant reaction conditions used for the particular process, cannot...

Cryogenic Etching of High Aspect Ratio 400 nm Pitch Silicon Gratings.

PubMed

Miao, Houxun; Chen, Lei; Mirzaeimoghri, Mona; Kasica, Richard; Wen, Han

2016-10-01

The cryogenic process and Bosch process are two widely used processes for reactive ion etching of high aspect ratio silicon structures. This paper focuses on the cryogenic deep etching of 400 nm pitch silicon gratings with various etching mask materials including polymer, Cr, SiO 2 and Cr-on-polymer. The undercut is found to be the key factor limiting the achievable aspect ratio for the direct hard masks of Cr and SiO 2 , while the etch selectivity responds to the limitation of the polymer mask. The Cr-on-polymer mask provides the same high selectivity as Cr and reduces the excessive undercut introduced by direct hard masks. By optimizing the etching parameters, we etched a 400 nm pitch grating to ≈ 10.6 μ m depth, corresponding to an aspect ratio of ≈ 53.

Fiber reinforced polymer (FRP) composite piles used on pier rehabilitation, Little Diamond Island, Casco Bay, Portland, Maine.

DOT National Transportation Integrated Search

2012-10-01

Fiber reinforced polymer (FRP) composite piles were used on a pier rehabilitation project at : Little Diamond Island in Casco Bay near Portland Maine. The project was the replacement : of an aging wooden pier at the ferry berthing terminal. The FRP p...

Influence of film structure on the dewetting kinetics of thin polymer films in the solvent annealing process.

PubMed

Zhang, Huanhuan; Xu, Lin; Lai, Yuqing; Shi, Tongfei

2016-06-28

On a non-wetting solid substrate, the solvent annealing process of a thin polymer film includes the swelling process and the dewetting process. Owing to difficulties in the in situ analysis of the two processes simultaneously, a quantitative study on the solvent annealing process of thin polymer films on the non-wetting solid substrate is extremely rare. In this paper, we design an experimental method by combining spectroscopic ellipsometry with optical microscopy to achieve the simultaneous in situ study. Using this method, we investigate the influence of the structure of swollen film on its dewetting kinetics during the solvent annealing process. The results show that for a thin PS film with low Mw (Mw = 4.1 kg mol(-1)), acetone molecules can form an ultrathin enriched layer between the PS film and the solid substrate during the swelling process. The presence of the acetone enriched layer accounts for the exponential kinetic behavior in the case of a thin PS film with low Mw. However, the acetone enriched layer is not observed in the case of a thin PS film with high Mw (Mw = 400 kg mol(-1)) and the slippage effect of polymer chains is valid during the dewetting process.

STIMULI-RESPONSIVE POLYMERS WITH ENHANCED EFFICIENCY IN RESERVOIR RECOVERY PROCESSES

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

Charles McCormick; Roger Hester

This sixth and final progress report for DOE Award Number DE-FC26-01BC15317 describes research during the period March 01, 2004 through August 31, 2004 performed at the University of Southern Mississippi on ''Stimuli Responsive Polymers with Enhanced Efficiency in Reservoir Recovery'' processes. Significantly, terpolymers that are responsive to changes in pH and ionic strength have been synthesized, characterized, and their solution properties have been extensively examined. Terpolymers composed of acrylamide, a carboxylated acrylamido monomer (AMBA), and a quaternary ammonium monomer (AMBATAC) with balanced compositions of the latter two, exhibit increases in aqueous solution viscosity as NaCl concentration is increased. This increasemore » in polymer coil size can be expected upon injection of this type of polymer into oil reservoirs of moderate-to-high salinity, leading to better mobility control. The opposite effect (loss of viscosity) is observed for conventional polymer systems. Additionally polymer mobility characteristics have been conducted for a number of hydrophilic copolymers utilizing an extensional flow apparatus and size exclusion chromatography. This study reveled that oil recovery enhancement through use of polymers in a water flood is due to the polymer's resistance to deformation as it flows through the reservoir. Individual polymers when in aqueous solution form coils. The larger the polymer's coil size, the greater the polymer's resistance to extensional flow and the more effective the polymer is in enhancing oil recovery. Large coil sizes are obtained by increasing the polymer molecular weight and having macromolecular structures that favor greater swelling of the coil by the aqueous solvent conditions (temperature, pH and electrolyte concentration) existing in the reservoir.« less

Simulation of ring polymer melts with GPU acceleration

NASA Astrophysics Data System (ADS)

Schram, R. D.; Barkema, G. T.

2018-06-01

We implemented the elastic lattice polymer model on the GPU (Graphics Processing Unit), and show that the GPU is very efficient for polymer simulations of dense polymer melts. The implementation is able to perform up to 4.1 ṡ109 Monte Carlo moves per second. Compared to our standard CPU implementation, we find an effective speed-up of a factor 92. Using this GPU implementation we studied the equilibrium properties and the dynamics of non-concatenated ring polymers in a melt of such polymers, using Rouse modes. With increasing polymer length, we found a very slow transition to compactness with a growth exponent ν ≈ 1 / 3. Numerically we find that the longest internal time scale of the polymer scales as N3.1, with N the molecular weight of the ring polymer.

Flexible Polymer/Metal/Polymer and Polymer/Metal/Inorganic Trilayer Transparent Conducting Thin Film Heaters with Highly Hydrophobic Surface.

PubMed

Kang, Tae-Woon; Kim, Sung Hyun; Kim, Cheol Hwan; Lee, Sang-Mok; Kim, Han-Ki; Park, Jae Seong; Lee, Jae Heung; Yang, Yong Suk; Lee, Sang-Jin

2017-09-27

Polymer/metal/polymer and polymer/metal/inorganic trilayer-structured transparent electrodes with fluorocarbon plasma polymer thin film heaters have been proposed. The polymer/metal/polymer and polymer/metal/inorganic transparent conducting thin films fabricated on a large-area flexible polymer substrate using a continuous roll-to-roll sputtering process show excellent electrical properties and visible-light transmittance. They also exhibit water-repelling surfaces to prevent wetting and to remove contamination. In addition, the adoption of a fluorocarbon/metal/fluorocarbon film permits an outer bending radius as small as 3 mm. These films have a sheet resistance of less than 5 Ω sq -1 , sufficient to drive light-emitting diode circuits. The thin film heater with the fluorocarbon/Ag/SiN x structure exhibits excellent heating characteristics, with a temperature reaching 180 °C under the driving voltage of 13 V. Therefore, the proposed polymer/metal/polymer and polymer/metal/inorganic transparent conducting electrodes using polymer thin films can be applied in flexible and rollable displays as well as automobile window heaters and other devices.

Puncture-Healing Properties of Carbon Nanotube-Filled Ionomers

NASA Technical Reports Server (NTRS)

Ward, Thomas C.

2003-01-01

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.

Basalt fiber reinforced polymer composites: Processing and properties

NASA Astrophysics Data System (ADS)

Liu, Qiang

A high efficiency rig was designed and built for in-plane permeability measurement of fabric materials. A new data derivation procedure to acquire the flow fluid pattern in the experiment was developed. The measurement results of the in-plane permeability for basalt twill 31 fabric material showed that a high correlation exists between the two principal permeability values for this fabric at 35% fiber volume fraction. This may be the most important scientific contribution made in this thesis. The results from radial measurements corresponded quite well with those from Unidirectional (UD) measurements, which is a well-established technique. No significant differences in mechanical properties were found between basalt fabric reinforced polymer composites and glass composites reinforced by a fabric of similar weave pattern. Aging results indicate that the interfacial region in basalt composites may be more vulnerable to environmental damage than that in glass composites. However, the basalt/epoxy interface may have been more durable than the glass/epoxy interface in tension-tension fatigue because the basalt composites have significantly longer fatigue life. In this thesis, chapter I reviews the literature on fiber reinforced polymer composites, with concentration on permeability measurement, mechanical properties and durability. Chapter II discusses the design of the new rig for in-plane permeability measurement, the new derivation procedure for monitoring of the fluid flow pattern, and the permeability measurement results. Chapter III compares the mechanical properties and durability between basalt fiber and glass fiber reinforced polymer composites. Lastly, chapter IV gives some suggestions and recommendations for future work.

Iron oxyhydroxide mineralization on microbial extracellular polysaccharides

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

Chan, Clara S.; Fakra, Sirine C.; Edwards, David C.

2010-06-22

Iron biominerals can form in neutral pH microaerophilic environments where microbes both catalyze iron oxidation and create polymers that localize mineral precipitation. In order to classify the microbial polymers that influence FeOOH mineralogy, we studied the organic and mineral components of biominerals using scanning transmission X-ray microscopy (STXM), micro X-ray fluorescence ({mu}XRF) microscopy, and high-resolution transmission electron microscopy (HRTEM). We focused on iron microbial mat samples from a creek and abandoned mine; these samples are dominated by iron oxyhydroxide-coated structures with sheath, stalk, and filament morphologies. In addition, we characterized the mineralized products of an iron-oxidizing, stalk-forming bacterial culture isolatedmore » from the mine. In both natural and cultured samples, microbial polymers were found to be acidic polysaccharides with carboxyl functional groups, strongly spatially correlated with iron oxyhydroxide distribution patterns. Organic fibrils collect FeOOH and control its recrystallization, in some cases resulting in oriented crystals with high aspect ratios. The impact of polymers is particularly pronounced as the materials age. Synthesis experiments designed to mimic the biomineralization processes show that the polysaccharide carboxyl groups bind dissolved iron strongly but release it as mineralization proceeds. Our results suggest that carboxyl groups of acidic polysaccharides are produced by different microorganisms to create a wide range of iron oxyhydroxide biomineral structures. The intimate and potentially long-term association controls the crystal growth, phase, and reactivity of iron oxyhydroxide nanoparticles in natural systems.« less

Review of potential processing techniques for the encapsulation of wastes in thermoplastic polymers

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

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

1995-08-01

Thermoplastic encapsulation has been extensively studied at Brookhaven National Laboratory`s (BNL) Environmental and Waste Technology Center (EWTC) as a waste encapsulation technology applicable to a wide range of waste types including radioactive, hazardous and mixed wastes. Encapsulation involves processing thermoplastic and waste materials into a waste form product by heating and mixing both materials into a homogeneous molten mixture. Cooling of the melt results in a solid monolithic waste form in which contaminants have been completely surrounded by a polymer matrix. Heating and mixing requirements for successful waste encapsulation can be met using proven technologies available in various types ofmore » commercial equipment. Processing techniques for thermoplastic materials, such as low density polyethylene (LDPE), are well established within the plastics industry. The majority of commercial polymer processing is accomplished using extruders, mixers or a combination of these technologies. Extruders and mixers are available in a broad range of designs and are used during the manufacture of consumer and commercial products as well as for compounding applications. Compounding which refers to mixing additives such as stabilizers and/or colorants with polymers, is analogous to thermoplastic encapsulation. Several processing technologies were investigated for their potential application in encapsulating residual sorbent waste in selected thermoplastic polymers, including single-screw extruders, twin-screw extruders, continuous mixers, batch mixers as well as other less conventional devices. Each was evaluated based on operational ease, quality control, waste handling capabilities as well as degree of waste pretreatment required. Based on literature review, this report provides a description of polymer processing technologies, a discussion of the merits and limitations of each and an evaluation of their applicability to the encapsulation of sorbent wastes.« less

Aqueous Processing for Printed Organic Electronics: Conjugated Polymers with Multistage Cleavable Side Chains.

PubMed

Schmatz, Brian; Yuan, Zhibo; Lang, Augustus W; Hernandez, Jeff L; Reichmanis, Elsa; Reynolds, John R

2017-09-27

The ability to process conjugated polymers via aqueous solution is highly advantageous for reducing the costs and environmental hazards of large scale roll-to-roll processing of organic electronics. However, maintaining competitive electronic properties while achieving aqueous solubility is difficult for several reasons: (1) Materials with polar functional groups that provide aqueous solubility can be difficult to purify and characterize, (2) many traditional coupling and polymerization reactions cannot be performed in aqueous solution, and (3) ionic groups, though useful for obtaining aqueous solubility, can lead to a loss of solid-state order, as well as a screening of any applied bias. As an alternative, we report a multistage cleavable side chain method that combines desirable aqueous processing attributes without sacrificing semiconducting capabilities. Through the attachment of cleavable side chains, conjugated polymers have for the first time been synthesized, characterized, and purified in organic solvents, converted to a water-soluble form for aqueous processing, and brought through a final treatment to cleave the polymer side chains and leave behind the desired electronic material as a solvent-resistant film. Specifically, we demonstrate an organic soluble polythiophene that is converted to an aqueous soluble polyelectrolyte via hydrolysis. After blade coating from an aqueous solution, UV irradiation is used to cleave the polymer's side chains, resulting in a solvent-resistant, electroactive polymer thin film. In application, this process results in aqueous printed materials with utility for solid-state charge transport in organic field effect transistors (OFETs), along with red to colorless electrochromism in ionic media for color changing displays, demonstrating its potential as a universal method for aqueous printing in organic electronics.

Corrosion Fatigue and Environmentally Assisted Cracking in Aging Military Vehicles (La fatigue-corrosion et la fissuration en milieu ambiant des vehicules militaires vieillissants)

DTIC Science & Technology

2011-03-01

deposition temperature is above 260°C (500°F), CVD Al cannot be applied to many structural alloys used in aerospace [12]. 23.3.4 Spray Deposited Cadmium...Alternatives There are several different aluminum-based coatings that can be deposited by spraying : aluminum and Al alloys , metallic-ceramic coatings...and Al - and Zn-filled polymers [12]. Thermal spray (flame or arc) is a very flexible and cost-effective process for deposition of pure

Corrosion Fatigue and Environmentally Assisted Cracking in Aging Military Vehicles (le fatigue-corrosion et la fissuration en milieu ambiant des vehicules militaires vieillissants)

DTIC Science & Technology

2011-03-01

deposition temperature is above 260°C (500°F), CVD Al cannot be applied to many structural alloys used in aerospace [12]. 23.3.4 Spray Deposited Cadmium...Alternatives There are several different aluminum-based coatings that can be deposited by spraying : aluminum and Al alloys , metallic-ceramic coatings...and Al - and Zn-filled polymers [12]. Thermal spray (flame or arc) is a very flexible and cost-effective process for deposition of pure

Processing and Dynamic Failure Characterization of Novel Impact Absorbing Transparent Interpenetrating Polymer Networks (t-IPN)

DTIC Science & Technology

2013-07-05

oven for the same curing treatment as before. The scanning electron microscope (SEM) photo in Figure 19 shows a typical sample with TMSPM and IPTES...Methacrylate-based Polymers,’ S. A . Bird , PhD Dissertation, Department of Polymer and Fiber Engineering, Auburn University, Summer 2013. ’Fracture Behavior...Polymer Networks with Polyurethane-poly(methyl methacrylate),’ K. C. Jajam, S. A . Bird , M. L. Auad, and H. V. Tippur, Polymer Testing, Vol. 32, pp

Physical Properties of Polymers (Ultrastructure Processing of Polymers)

DTIC Science & Technology

1982-09-30

vinyl benzene Network-Diluent Systems". 17. J . Appl. Polym. Sci. 28, 219-224 (1983) (with R. Vukovic and W.J. MacKnight) "Compatibility of Some...Temperature of Polymer Networks by Dil uents". 23. J . Appl. Polym. Sci. 28, 1379-1389 (1983) (with R. Vukovic , V. Kuresevic, N. Segudovic, and W.J...AFOSR 80-0101 IV. DATES: 1 January 1980 - 30 September 1982 V. SENIOR RESEARCH PERSONNEL*: Dr. C. Crosby Dr. G. ten Brinke Dr. T. Ellis Dr. R. Vukovic

Water-Based Coating Simplifies Circuit Board Manufacturing

NASA Technical Reports Server (NTRS)

2008-01-01

The Structures and Materials Division at Glenn Research Center is devoted to developing advanced, high-temperature materials and processes for future aerospace propulsion and power generation systems. The Polymers Branch falls under this division, and it is involved in the development of high-performance materials, including polymers for high-temperature polymer matrix composites; nanocomposites for both high- and low-temperature applications; durable aerogels; purification and functionalization of carbon nanotubes and their use in composites; computational modeling of materials and biological systems and processes; and developing polymer-derived molecular sensors. Essentially, this branch creates high-performance materials to reduce the weight and boost performance of components for space missions and aircraft engine components. Under the leadership of chemical engineer, Dr. Michael Meador, the Polymers Branch boasts world-class laboratories, composite manufacturing facilities, testing stations, and some of the best scientists in the field.

Effect of polymers on the retention and aging of enzyme on bioactive papers.

PubMed

Khan, Mohidus Samad; Haniffa, Sharon B M; Slater, Alison; Garnier, Gil

2010-08-01

The effect of polymer on the retention and the thermal stability of bioactive enzymatic papers was measured using a colorimetric technique quantifying the intensity of the enzyme-substrate product complex. Alkaline phosphatase (ALP) was used as model enzyme. Three water soluble polymers: a cationic polyacrylamide (CPAM), an anionic polyacrylic acid (PAA) and a neutral polyethylene oxide (PEO) were selected as retention aids. The model polymers increased the enzyme adsorption on paper by around 50% and prevented enzyme desorption upon rewetting of the papers. The thermal deactivation of ALP retained on paper with polymers follows two sequential first order reactions. This was also observed for ALP simply physisorbed on paper. The retention aid polymers instigated a rapid initial deactivation which significantly decreased the longevity of the enzymatic papers. This suggests some enzyme-polymer interaction probably affecting the enzyme tertiary structure. A deactivation mathematical model predicting the enzymatic paper half-life was developed. Crown Copyright 2010. Published by Elsevier B.V. All rights reserved.

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

DTIC Science & Technology

1986-01-31

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

Poly(carbonate-imide) polymer

NASA Technical Reports Server (NTRS)

St. Clair, Terry L. (Inventor); Maudgal, Shubha (Inventor); Pratt, J. Richard (Inventor)

1987-01-01

A novel series of polymers and copolymers based on a polyimide backbone with the incorporation of carbonate moieties along the backbone. The process for preparing these polymers and copolymers is also disclosed as is a novel series of dinitrodiphenyl carbonates and diaminodiphenyl carbonates. The novel polymers and copolymers exhibit high temperature capability and because of the carbonate unit, many exhibit a high degree of order and/or crystallinity.

Modification of polymers by polymeric additives

NASA Astrophysics Data System (ADS)

Nesterov, A. E.; Lebedev, E. V.

1989-08-01

The conditions for the thermodynamic compatibility of polymers and methods for its enhancement are examined. The study of the influence of various factors on the concentration-temperature limits of compatibility, dispersion stabilisation processes, and methods for the improvement of adhesion between phases in mixtures of thermodynamically incompatible polymers is described. Questions concerning the improvement of the physicomechanical characteristics of polymer dispersions are considered. The bibliography includes 200 references.

Organosilicon Polymers as Precursors for Silicon Containing Ceramics: Recent Developments.

DTIC Science & Technology

1987-08-14

the polymer to a ceramic material, hopefully of the desired composition . In the latter alternative, shrinkage during pyrolysis should not be great...carbon-carbon composite materials. In order to have a useful preceramic polymer . considerations of structure and reactivitv are of paramount importance...process so that on pyrolysis non-volatile, three-dimensional networks (which lead to maximum weight retention) are formed. Thus. preceramic polymer

Achieving 15% Tandem Polymer Solar Cells

DTIC Science & Technology

2015-06-23

solar cell structures – both polymer only and hybrid tandem cells to constantly pushing the envelope of solution processed solar cell ...performance – 11.6% polymer tandem cell , 7% transparent tandem polymer cell , and over 10% PCE hybrid tandem solar cells were achieved. In addition, AFOSR’s...final support also enabled us to explore novel hybrid perovskite solar cells in depth. For example, single junction cell efficiency

Two-step sulfonation process for the conversion of polymer fibers to carbon fibers

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

Barton, Bryan E.; Patton, Jasson T.; Hukkanen, Eric J.

Disclosed herein are processes for preparing carbon fibers, comprising: sulfonating a polymer fiber with a sulfonating agent that is fuming sulfuric acid, sulfuric acid, chlorosulfonic acid, or a combination thereof; treating the sulfonated polymer with a heated solvent, wherein the temperature of the heated solvent is at least 95.degree. C.; and carbonizing the resulting product by heating it to a temperature of 501-3000.degree. C. Carbon fibers prepared according to these methods are also disclosed herein.

Polymer Infiltration Studies

NASA Technical Reports Server (NTRS)

Marchello, Joseph M.

1991-01-01

Progress was made on the preparation of carbon fiber composites using advanced polymer resins. Processes reported include powder towpreg process, weaving towpreg made from dry powder prepreg, composite from powder coated towpreg, and toughening of polyimide resin (PMR) composites by semi-interpenetrating networks. Several important areas of polymer infiltration into fiber bundles will be researched. Preparation to towpreg for textile preform weaving and braiding and for automated tow placement is a major goal, as are the continued development of prepregging technology and the various aspects of composite part fabrication.

Supercritical transitiometry of polymers.

PubMed

Randzio, S L; Grolier, J P

1998-06-01

Employing supercritical fluids (SCFs) during polymers processing allows the unusual properties of SCFs to be exploited for making polymer products that cannot be obtained by other means. A new supercritical transitiometer has been constructed to permit study of the interactions of SCFs with polymers during processing under well-defined conditions of temperature and pressure. The supercritical transitiometer allows pressure to be exerted by either a supercritical fluid or a neutral medium and enables simultaneous determination of four basic parameters of a transition, i.e., p, T, Δ(tr)H and Δ(tr)V. This permits determination of the SCF effect on modification of the polymer structure at a given pressure and temperature and defines conditions to allow reproducible preparation of new polymer structures. Study of a semicrystalline polyethylene by this method has defined conditions for preparation of new microfoamed phases with good mechanical properties. The low densities and microporous structures of the new materials may make them useful for applications in medicine, pharmacy, or the food industry, for example.

Nonequilibrium thermodynamics of dilute polymer solutions in flow.

PubMed

Latinwo, Folarin; Hsiao, Kai-Wen; Schroeder, Charles M

2014-11-07

Modern materials processing applications and technologies often occur far from equilibrium. To this end, the processing of complex materials such as polymer melts and nanocomposites generally occurs under strong deformations and flows, conditions under which equilibrium thermodynamics does not apply. As a result, the ability to determine the nonequilibrium thermodynamic properties of polymeric materials from measurable quantities such as heat and work is a major challenge in the field. Here, we use work relations to show that nonequilibrium thermodynamic quantities such as free energy and entropy can be determined for dilute polymer solutions in flow. In this way, we determine the thermodynamic properties of DNA molecules in strong flows using a combination of simulations, kinetic theory, and single molecule experiments. We show that it is possible to calculate polymer relaxation timescales purely from polymer stretching dynamics in flow. We further observe a thermodynamic equivalence between nonequilibrium and equilibrium steady-states for polymeric systems. In this way, our results provide an improved understanding of the energetics of flowing polymer solutions.

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

PubMed

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

2017-01-18

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

Method of forming a foamed thermoplastic polymer

DOEpatents

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

1984-11-21

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.

Thermal spraying of polyethylene-based polymers: Processing and characterization

NASA Astrophysics Data System (ADS)

Otterson, David Mark

This research explores the development of a flame-spray process map as it relates to polymers. This work provides a more complete understanding of the thermal history of the coating material from injection, to deposition and finally to cooling. This was accomplished through precise control of the processing conditions during deposition. Mass flow meters were used to monitor air and fuel flows as they were systematically changed, while temperatures were simultaneously monitored along the length of the flame. A process model was then implemented that incorporated this information along with measured particle velocities, particle size distribution, the polymer's melting temperature and its enthalpy of melting. This computational model was then used to develop a process map that described particle softening, melting and decomposition phenomena as a function of particle size and standoff distance. It demonstrated that changes in particle size caused significant variations in particle states achieved in-flight. A series of experiments were used to determine the range of spray parameters within which a cohesive coating without visible signs of degradation could be sprayed. These results provided additional information that complimented the computational processing map. The boundaries established by these results were the basis for a Statistical Design of Experiments that tested the effects that subtle processing changes had on coating properties. A series of processing maps were developed that combined the computational and the experimental results to describe the manner in which processing parameters interact to determine the degree of melting, polymer degradation and coating porosity. Strong interactions between standoff distance and traverse rate can cause the polymer to degrade and form pores in the coating. A clear picture of the manner in which particle size and standoff distance interact to determine particle melting was provided by combining the computational processing map with the collected splats and microstructures. Finally, a strong interaction was observed between standoff distance and flame length, which is determined by the air:fuel ratio. When flame length exceeds the standoff distance, polymer degradation results from excessive heating of the substrate. A descriptive model of the process is then provided to highlight the importance of these interactions. (Abstract shortened by UMI.)

Pressure polymerization of polyester

DOEpatents

Maurer, Charles J.; Shaw, Gordon; Smith, Vicky S.; Buelow, Steven J.; Tumas, William; Contreras, Veronica; Martinez, Ronald J.

2000-08-29

A process is disclosed for the preparation of a polyester polymer or polyester copolymer under superatmospheric pressure conditions in a pipe or tubular reaction under turbannular flow conditions. Reaction material having a glycol equivalents to carboxylic acid equivalents mole ratio of from 1.0:1 to 1.2:1, together with a superatmospheric dense gaseous medium are fed co-currently to the reactor. Dicarboxylic acid and/or diol raw materials may be injected into any of the reaction zones in the process during operation to achieve the overall desired mole ratio balance. The process operates at temperatures of from about 220.degree. C. to about 320.degree. C., with turbannular flow achieved before the polymer product and gas exit the reactor process. The pressure in the reaction zones can be in the range from 15 psia to 2500 psia. A polymer product having a DP of a greater than 40, more preferably at least about 70, is achieved by the transfer of water from the reacting material polymer melt to the gaseous medium in the reactor.

The increase of compressive strength of natural polymer modified concrete with Moringa oleifera

NASA Astrophysics Data System (ADS)

Susilorini, Rr. M. I. Retno; Santosa, Budi; Rejeki, V. G. Sri; Riangsari, M. F. Devita; Hananta, Yan's. Dianaga

2017-03-01

Polymer modified concrete is one of some concrete technology innovations to meet the need of strong and durable concrete. Previous research found that Moringa oleifera can be applied as natural polymer modifiers into mortars. Natural polymer modified mortar using Moringa oleifera is proven to increase their compressive strength significantly. In this resesearch, Moringa oleifera seeds have been grinded and added into concrete mix for natural polymer modified concrete, based on the optimum composition of previous research. The research investigated the increase of compressive strength of polymer modified concrete with Moringa oleifera as natural polymer modifiers. There were 3 compositions of natural polymer modified concrete with Moringa oleifera referred to previous research optimum compositions. Several cylinder of 10 cm x 20 cm specimens were produced and tested for compressive strength at age 7, 14, and, 28 days. The research meets conclusions: (1) Natural polymer modified concrete with Moringa oleifera, with and without skin, has higher compressive strength compared to natural polymer modified mortar with Moringa oleifera and also control specimens; (2) Natural polymer modified concrete with Moringa oleifera without skin is achieved by specimens contains Moringa oleifera that is 0.2% of cement weight; and (3) The compressive strength increase of natural polymer modified concrete with Moringa oleifera without skin is about 168.11-221.29% compared to control specimens

Tough, processable semi-interpenetrating polymer networks from monomer reactants

NASA Technical Reports Server (NTRS)

Pater, Ruth H. (Inventor)

1994-01-01

A high temperature semi-interpenetrating polymer network (semi-IPN) was developed which had significantly improved processability, damage tolerance, and mechanical performance, when compared to the commercial Thermid materials. This simultaneous semi-IPN was prepared by mixing the monomer precursors of Thermid AL-600 (a thermoset) and NR-150B2 (a thermoplastic) and allowing the monomers to react randomly upon heating. This reaction occurs at a rate which decreases the flow and broadens the processing window. Upon heating at a higher temperature, there is an increase in flow. Because of the improved flow properties, broadened processing window and enhanced toughness, high strength polymer matrix composites, adhesives and molded articles can now be prepared from the acetylene end-capped polyimides which were previously inherently brittle and difficult to process.

Improved electron transport properties of n-type naphthalenediimide polymers through refined molecular ordering and orientation induced by processing solvents.

PubMed

An, Yujin; Long, Dang Xuan; Kim, Yiho; Noh, Yong-Young; Yang, Changduk

2016-05-14

To determine the role played by the choice of processing solvents in governing the photophysics, microstructure, and charge carrier transport in naphthalenediimide (NDI)-based polymers, we have prepared two new NDI-bithiophene (T2)- and NDI-thienothiophene (TTh)-containing polymers with hybrid siloxane pentyl chains (SiC5) (P(NDI2SiC5-T2) and P(NDI2SiC5-TTh)). Among the various processing solvents studied here, the films prepared using chloroform exhibited far better electron mobilities (0.16 ± 0.1-0.21 ± 0.05 cm(2) V(-1) s(-1)) than the corresponding samples prepared from different solvents, exceeding one order of magnitude higher, indicating the significant influence of the processing solvent on the charge transport. Upon thin-film analysis using atomic force microscopy and grazing incidence X-ray diffraction, we discovered that molecular ordering and orientation are affected by the choice of the processing solvent, which is responsible for the change in the transport characteristics of this class of polymers.

Silver nanowires network encapsulated by low temperature sol-gel ZnO for transparent flexible electrodes with ambient stability

NASA Astrophysics Data System (ADS)

Shin, Wonjung; Cho, Wonki; Baik, Seung Jae

2018-01-01

As a geometrically engineered realization of transparent electrode, Ag nanowires network is promising for its superior characteristics both on electrical conductivity and optical transmittance. However, for a potential commercialization of Ag nanowires network, further investigations on encapsulation materials are necessary to prevent degradation caused by ambient aging. In addition, the temperature range of the coating process for the encapsulation material needs to be low enough to prevent degradation of polymer substrates during the film coating processes, when considering emerging flexible device application of transparent electrodes. We present experimental results showing that low temperature sol-gel ZnO processed under 130 °C is an effective encapsulation material preventing ambient oxidation of Ag nanowires network without degrading electrical, optical, and mechanical properties.

Diorganosilacetylene-alt-diorganosilvinylene polymers and a process densifying porous silicon-carbide bodies

DOEpatents

Barton, Thomas J.; Ijadi-Maghsoodi, Sina; Pang, Yi

1994-05-17

The present invention provides linear organosilicon polymers including acetylene and vinylene moieties, and a process for their preparation. These diorganosilacetylene-alt-diorganosilvinylene linear polymers can be represented by the formula: --[--(R.sup.1)(R.sup.2)Si--C.tbd.C--(R.sup.3)(R.sup.4)Si--CH=CH--].sub.n-- , wherein n.gtoreq.2; and each R.sup.1, R.sup.2, R.sup.3, and R.sup.4 is independently selected from the group consisting of hydrogen, halogen, alkyl, alkenyl, aryl, and aralkyl radicals. The polymers are soluble in organic solvents, air stable, and can be pulled into fibers or cast into films. They can be thermally converted into silicon carbide ceramic materials.

Diorganosilacetylene-alt-diorganosilvinylene polymers and a process of preparation

DOEpatents

Barton, Thomas J.; Ijadi-Maghsoodi, Sina; Pang, Yi

1993-08-31

The present invention provides linear organosilicon polymers including acetylene and vinylene moieties, and a process for their preparation. These diorganosilacetylenealt-diorganosilvinylene linear polymers can be represented by the formula: --[--(R.sup.1)(R.sup.2)Si--C.ident.C--(R.sup.3)(R.sup.4)Si--CH=CH--].sub.n --, wherein n.gtoreq.2; each R.sup.1, R.sup.2, R.sup.3, and R.sup.4 is independently selected from the group consisting of hydrogen, halogen, alkyl, alkenyl, aryl, and aralkyl radicals. The polymers are soluble in organic solvents, air stable, and can be pulled into fibers or cast into films. They can be thermally converted into silicon carbide ceramic materials.

Diorganosilacetylene-alt-diorganosilvinylene polymers and a process of preparation

DOEpatents

Barton, Thomas J.; Ijadi-Maghsoodi, Sina; Pang, Yi

1995-10-10

The present invention provides linear organosilicon polymers including acetylene and vinylene moieties, and a process for their preparation. These diorganosilacetylene-alt-diorganosilvinylene linear polymers can be represented by the formula: --[--(R.sup.1)(R.sup.2)Si--C.tbd.C--(R.sup.3)(R.sup.4)Si--CH.dbd.CH--].sub .n --, wherein n.gtoreq.2; and each R.sup.1, R.sup.2, R.sup.3, and R.sup.4 is independently selected from the group consisting of hydrogen, halogen, alkyl, alkenyl, aryl, and aralkyl radicals. The polymers are soluble in organic solvents, air stable, and can be pulled into fibers or cast into films. They can be thermally converted into silicon carbide ceramic materials.

Diorganosilacetylene-alt-diorganosilvinylene polymers and a process of preparation

DOEpatents

Barton, T.J.; Ijadi-Maghsoodi, S.; Yi Pang.

1993-08-31

The present invention provides linear organosilicon polymers including acetylene and vinylene moieties, and a process for their preparation. These diorganosilacetylene-alt-diorganosilvinylene linear polymers can be represented by the formula: -[-(R[sup 1])(R[sup 2])Si-C[triple bond]C-(R[sup 3])(R[sup 4])Si-CH[double bond]CH-][sub n]-, wherein n[>=]2; each R[sup 1], R[sup 2], R[sup 3], and R[sup 4] is independently selected from the group consisting of hydrogen, halogen, alkyl, alkenyl, aryl, and aralkyl radicals. The polymers are soluble in organic solvents, air stable, and can be pulled into fibers or cast into films. They can be thermally converted into silicon carbide ceramic materials.

Diorganosilacetylene-alt-diorganosilvinylene polymers and a process of preparation

DOEpatents

Barton, T.J.; Ijadi-Maghsoodi, S.; Pang, Y.

1995-10-10

The present invention provides linear organosilicon polymers including acetylene and vinylene moieties, and a process for their preparation. These diorganosilacetylene-alt-diorganosilvinylene linear polymers can be represented by the formula: --[--(R{sup 1})(R{sup 2})Si--C{triple_bond}C--(R{sup 3})(R{sup 4})Si--CH{double_bond}CH--]{sub n}--, wherein n{>=}2; and each R{sup 1}, R{sup 2}, R{sup 3}, and R{sup 4} is independently selected from the group consisting of hydrogen, halogen, alkyl, alkenyl, aryl, and aralkyl radicals. The polymers are soluble in organic solvents, air stable, and can be pulled into fibers or cast into films. They can be thermally converted into silicon carbide ceramic materials.

Low density microcellular foams

DOEpatents

Aubert, J.H.; Clough, R.L.; Curro, J.G.; Quintana, C.A.; Russick, E.M.; Shaw, M.T.

1985-10-02

Low density, microporous polymer foams are provided by a process which comprises forming a solution of polymer and a suitable solvent followed by rapid cooling of the solution to form a phase-separated system and freeze the phase-separated system. The phase-separated system comprises a polymer phase and a solvent phase, each of which is substantially continuous within the other. The morphology of the polymer phase prior to and subsequent to freezing determine the morphology of the resultant foam. Both isotropic and anisotropic foams can be produced. If isotropic foams are produced, the polymer and solvent are tailored such that the solution spontaneously phase-separates prior to the point at which any component freezes. The morphology of the resultant polymer phase determines the morphology of the reusltant foam and the morphology of the polymer phase is retained by cooling the system at a rate sufficient to freeze one or both components of the system before a change in morphology can occur. Anisotropic foams are produced by forming a solution of polymer and solvent that will not phase separate prior to freezing of one or both components of the solution. In such a process, the solvent typically freezes before phase separation occurs. The morphology of the resultant frozen two-phase system determines the morphology of the resultant foam. The process involves subjecting the solution to essentially one-dimensional cooling. Foams having a density of less than 0.1 g/cc and a uniform cell size of less than 10 ..mu..m and a volume such that the foams have a length greater than 1 cm are provided.

The Influence of Polymer Sequence on the Formation of Bulk-Heterojunctions in Organic Solar Cells

NASA Astrophysics Data System (ADS)

Gao, Dong

This thesis summarizes my work on organic solar cells during my graduate studies. Chapter 1 serves as an introduction to organic solar cells. I will briefly discuss the working mechanism, and describe the device fabrication processes and testing set up that I designed at the beginning of my graduate studies. Chapter 2 describes the size-dependent behavior of polymer solar cells measured under partial illumination. We found that ITO resistance is a significant source of power loss because sheet resistance (Rs) increases with area. The non-illuminated part of a partially illuminated device introduces some interesting effects related to the physics of device operation. Specifically, this contributes additional "dark diodes" that connect in parallel with an illuminated cell, giving rise to an apparent decrease in VOC and increase in FF as the illuminated portion of the cell is decreased. Chapter 3 is a study of a P3HS-b-P3HT block copolymer as a donor material in organic solar cells. Fiber-like nanostructures are formed spontaneously in P3HS-b-P3HT:PCBM devices, and their thermal stability exceeds homopolymer:PCBM devices or ternary mixtures. Although P3HS-b-P3HT contains two distinct electron donor materials, the EQE spectra, hole mobility, Jsc, and PCE exceed that of a physical mixture of the two homopolymers and PCBM. Chapter 4 compares the photovoltaic properties of two conjugated copolymers with the same composition, P3HS-b-P3HT and P3HS- s-P3HT. The block polymer spontaneously undergoes intrinsic phase separation and the statistical polymer does not. P3HS-b-P3HT devices perform best when the native self-assembled structure is most perturbed, which is accomplished using PC71BM. P3HS-s-P3HT is a polymer that does not form a native phase separated structure. Here vapor annealing can be used to more predictably optimize the polymer:fullerene morphology. Chapter 5 studies the evolution of the electron mobility of two different acceptors with different crystallinity, PC71BM and ICBA, in a crystallized P3HT matrix during a prolonged thermal aging process. ICBA has an electron mobility that is over an order of magnitude lower than PC71BM. Given that both devices use the same polymer donor, it appears that high electron mobility does not correlate with the best device performance. The evolution of the acceptor appears to be the dominant factor that leads to long term changes in devices. Chapter 6 describes the synthesis of donor-acceptor copolymers with a "blocky" structure. Selenophene is introduced into PBDTTT-C-T in order to improve molecular ordering between polymer chains. Though more ordered morphologies are observed with blocky polymers, the physical mixture of parent polymers perform better in solar cell devices, which is not well correlated with morphology. Chapter 7 summarizes the above work and discusses the further directions in organic solar cell research.

Process for application of powder particles to filamentary materials

NASA Technical Reports Server (NTRS)

Baucom, Robert M. (Inventor); Snoha, John J. (Inventor); Marchello, Joseph M. (Inventor)

1991-01-01

This invention is a process for the uniform application of polymer powder particles to a filamentary material in a continuous manner to form a uniform composite prepreg material. A tow of the filamentary material is fed under carefully controlled tension into a spreading unit, where it is spread pneumatically into an even band. The spread filamentary tow is then coated with polymer particles from a fluidized bed, after which the coated filamentary tow is fused before take-up on a package for subsequent utilization. This process produces a composite prepreg uniformly without imposing severe stress on the filamentary material, and without requiring long, high temperature residence times for the polymer.

Dry Process for Manufacturing Hybridized Boron Fiber/Carbon Fiber Thermoplastic Composite Materials from a Solution Coated Precursor

NASA Technical Reports Server (NTRS)

Belvin, Harry L. (Inventor); Cano, Roberto J. (Inventor)

2003-01-01

An apparatus for producing a hybrid boron reinforced polymer matrix composite from precursor tape and a linear array of boron fibers. The boron fibers are applied onto the precursor tapes and the precursor tape processed within a processing component having an impregnation bar assembly. After passing through variable-dimension forming nip-rollers, the precursor tape with the boron fibers becomes a hybrid boron reinforced polymer matrix composite. A driving mechanism is used to pulled the precursor tape through the method and a take-up spool is used to collect the formed hybrid boron reinforced polymer matrix composite.

Membrane separation of ionic liquid solutions

DOEpatents

Campos, Daniel; Feiring, Andrew Edward; Majumdar, Sudipto; Nemser, Stuart

2015-09-01

A membrane separation process using a highly fluorinated polymer membrane that selectively permeates water of an aqueous ionic liquid solution to provide dry ionic liquid. Preferably the polymer is a polymer that includes polymerized perfluoro-2,2-dimethyl-1,3-dioxole (PDD). The process is also capable of removing small molecular compounds such as organic solvents that can be present in the solution. This membrane separation process is suitable for drying the aqueous ionic liquid byproduct from precipitating solutions of biomass dissolved in ionic liquid, and is thus instrumental to providing usable lignocellulosic products for energy consumption and other industrial uses in an environmentally benign manner.

Spacecraft dielectric material properties and spacecraft charging

NASA Technical Reports Server (NTRS)

Frederickson, A. R.; Wall, J. A.; Cotts, D. B.; Bouquet, F. L.

1986-01-01

The physics of spacecraft charging is reviewed, and criteria for selecting and testing semiinsulating polymers (SIPs) to avoid charging are discussed and illustrated. Chapters are devoted to the required properties of dielectric materials, the charging process, discharge-pulse phenomena, design for minimum pulse size, design to prevent pulses, conduction in polymers, evaluation of SIPs that might prevent spacecraft charging, and the general response of dielectrics to space radiation. SIPs characterized include polyimides, fluorocarbons, thermoplastic polyesters, poly(alkanes), vinyl polymers and acrylates, polymers containing phthalocyanine, polyacene quinones, coordination polymers containing metal ions, conjugated-backbone polymers, and 'metallic' conducting polymers. Tables summarizing the results of SIP radiation tests (such as those performed for the NASA Galileo Project) are included.

Ultrahigh Molecular Weight Aromatic Siloxane Polymers

NASA Technical Reports Server (NTRS)

Ludwick, L. M.

1983-01-01

Silphenylene-siloxane polymers can be prepared by a condensation reaction of a diol 1,4-bis(hydroxydimethylsilyl)benzene and a silane bis(dimethylamino)dimethylsilane. Using a stepwise condensation technique, a polymer (R=CH3) with a molecular weight in excess of 1.0 x 1 million has been produced. The polymer exhibits increased thermal stability, compared to a methyl siloxane polymer without the aromatic phenyl ring in the backbone. The use of bis(dimethylamino)methylvinylsilane should allow for ready crosslinking at the vinyl sites (R=-CH=CH2) introduced into the backbone. However, under the conditions of the reaction system a high molecular weight polymer was not obtained or the polymer underwent a crosslinking process during the synthesis.

Polymers by Non-Redox Processes: Synthesis, Physical Studies and Application

DTIC Science & Technology

1992-12-31

Schiff Base," in lournal Polymer Science Polymer Chemitry , 29 749 (1991), Y. Wei, R. Hariharan and J.K. Ray. 1991-25 "Fast Atom Bombardment Mass...Graduate Student - Georgia Arbuckle Graduate Student - David Swanson Visiting Graduate Student - Angela Fagot Technician - Boris Vuchic Computer

Solution-processed organic spin-charge converter.

PubMed

Ando, Kazuya; Watanabe, Shun; Mooser, Sebastian; Saitoh, Eiji; Sirringhaus, Henning

2013-07-01

Conjugated polymers and small organic molecules are enabling new, flexible, large-area, low-cost optoelectronic devices, such as organic light-emitting diodes, transistors and solar cells. Owing to their exceptionally long spin lifetimes, these carbon-based materials could also have an important impact on spintronics, where carrier spins play a key role in transmitting, processing and storing information. However, to exploit this potential, a method for direct conversion of spin information into an electric signal is indispensable. Here we show that a pure spin current can be produced in a solution-processed conducting polymer by pumping spins through a ferromagnetic resonance in an adjacent magnetic insulator, and that this generates an electric voltage across the polymer film. We demonstrate that the experimental characteristics of the generated voltage are consistent with it being generated through an inverse spin Hall effect in the conducting polymer. In contrast with inorganic materials, the conducting polymer exhibits coexistence of high spin-current to charge-current conversion efficiency and long spin lifetimes. Our discovery opens a route for a new generation of molecular-structure-engineered spintronic devices, which could lead to important advances in plastic spintronics.

High-throughput microarray mapping of cell wall polymers in roots and tubers during the viscosity-reducing process.

PubMed

Huang, Yuhong; Willats, William G; Lange, Lene; Jin, Yanling; Fang, Yang; Salmeán, Armando A; Pedersen, Henriette L; Busk, Peter Kamp; Zhao, Hai

2016-01-01

Viscosity reduction has a great impact on the efficiency of ethanol production when using roots and tubers as feedstock. Plant cell wall-degrading enzymes have been successfully applied to overcome the challenges posed by high viscosity. However, the changes in cell wall polymers during the viscosity-reducing process are poorly characterized. Comprehensive microarray polymer profiling, which is a high-throughput microarray, was used for the first time to map changes in the cell wall polymers of sweet potato (Ipomoea batatas), cassava (Manihot esculenta), and Canna edulis Ker. over the entire viscosity-reducing process. The results indicated that the composition of cell wall polymers among these three roots and tubers was markedly different. The gel-like matrix and glycoprotein network in the C. edulis Ker. cell wall caused difficulty in viscosity reduction. The obvious viscosity reduction of the sweet potato and the cassava was attributed to the degradation of homogalacturonan and the released 1,4-β-d-galactan and 1,5-α-l-arabinan. © 2015 International Union of Biochemistry and Molecular Biology, Inc.

Control of metallic corrosion through microbiological route.

PubMed

Maruthamuthu, S; Ponmariappan, S; Mohanan, S; Palaniswamy, N; Palaniappan, R; Rengaswamy, N S

2003-09-01

Involvement of biofilm or microorganisms in corrosion processes is widely acknowledged. Although majority of the studies on microbiologically induced corrosion (MIC) have concentrated on aerobic/anaerobic bacteria. There are numerous aerobic bacteria, which could hinder the corrosion process. The microbiologically produced exopolymers provide the structural frame work for the biofilm. These polymers combine with dissolved metal ions and form organometallic complexes. Generally heterotrophic bacteria contribute to three major processes: (i) synthesis of polymers (ii) accumulation of reserve materials like poly-beta-hydroxy butrate (iii) production of high molecular weight extracellular polysaccharides. Poly-beta-hydroxy butyrate is a polymer of D(-)beta-hydroxy butrate and has a molecular weight between 60,000 and 2,50,000. Some extracellular polymers also have higher molecular weights. It seems that higher molecular weight polymer acts as biocoating. In the present review, role of biochemistry on corrosion inhibition and possibilities of corrosion inhibition by various microbes are discussed. The role of bacteria on current demand during cathodic protection is also debated. In addition, some of the significant contributions made by CECRI in this promising area are highlighted.

Organic phototransistors with nanoscale phase-separated polymer/polymer bulk heterojunction layers

NASA Astrophysics Data System (ADS)

Hwang, Hyemin; Kim, Hwajeong; Nam, Sungho; Bradley, Donal D. C.; Ha, Chang-Sik; Kim, Youngkyoo

2011-05-01

Low-cost detectors for sensing photons at a low light intensity are of crucial importance in modern science. Phototransistors can deliver better signals of low-intensity light by electrical amplification, but conventional inorganic phototransistors have a limitation owing to their high temperature processes in vacuum. In this work, we demonstrate organic phototransistors with polymer/polymer bulk heterojunction blend films (mixtures of p-type and n-type semiconducting polymers), which can be fabricated by inexpensive solution processes at room temperature. The key idea here is to effectively exploit hole charges (from p-type polymer) as major signaling carriers by employing p-type transistor geometry, while the n-type polymer helps efficient charge separation from excitons generated by incoming photons. Results showed that the present organic transistors exhibited proper functions as p-type phototransistors with ~4.3 A W-1 responsivity at a low light intensity (1 µW cm-2), which supports their encouraging potential to replace conventional cooled charge coupled devices (CCD) for low-intensity light detection applications.Low-cost detectors for sensing photons at a low light intensity are of crucial importance in modern science. Phototransistors can deliver better signals of low-intensity light by electrical amplification, but conventional inorganic phototransistors have a limitation owing to their high temperature processes in vacuum. In this work, we demonstrate organic phototransistors with polymer/polymer bulk heterojunction blend films (mixtures of p-type and n-type semiconducting polymers), which can be fabricated by inexpensive solution processes at room temperature. The key idea here is to effectively exploit hole charges (from p-type polymer) as major signaling carriers by employing p-type transistor geometry, while the n-type polymer helps efficient charge separation from excitons generated by incoming photons. Results showed that the present organic transistors exhibited proper functions as p-type phototransistors with ~4.3 A W-1 responsivity at a low light intensity (1 µW cm-2), which supports their encouraging potential to replace conventional cooled charge coupled devices (CCD) for low-intensity light detection applications. Electronic supplementary information (ESI) available: XPS spectra of P3HT:F8BT nanolayers and pristine P3HT and F8BT films, HRTEM images of P3HT:F8BT blend film detached from the substrate, and 1D GIXD profiles of P3HT:F8BT nanolayers and PI layer coated on the ITO-glass substrates. See DOI: 10.1039/c0nr00915f

40 CFR 63.11398 - What definitions apply to this subpart?

Code of Federal Regulations, 2013 CFR

2013-07-01

... acrylonitrile units: acrylic fiber or modacrylic fiber. Acrylonitrile solution polymerization means a process where acrylonitrile and comonomers are dissolved in a solvent to form a polymer solution (typically... resulting reactor polymer solution (spin dope) is filtered and pumped directly to the fiber spinning process...

40 CFR 63.11398 - What definitions apply to this subpart?

Code of Federal Regulations, 2014 CFR

2014-07-01

... acrylonitrile units: acrylic fiber or modacrylic fiber. Acrylonitrile solution polymerization means a process where acrylonitrile and comonomers are dissolved in a solvent to form a polymer solution (typically... resulting reactor polymer solution (spin dope) is filtered and pumped directly to the fiber spinning process...

Pulp extrusion at ultra-high consistencies : selection of water soluble polymers for process optimization

Treesearch

C. Tim Scott

2002-01-01

Pulp extrusion at ultra-high consistencies (20% to 40% solids) is a new process developed at USDA Forest Service, Forest Products Laboratory (FPL) to convert recovered papers, wastepaper, and papermill residuals into solid sheets or profiles for compression molding. This process requires adding a water-soluble polymer (WSP) to alter the rheological properties of the...

Process of Making Boron-Fiber Reinforced Composite Tape

NASA Technical Reports Server (NTRS)

Belvin, Harry L. (Inventor); Cano, Roberto J. (Inventor); Johnston, Norman J. (Inventor); Marchello, Joseph M. (Inventor)

2002-01-01

The invention is an apparatus and method for producing a hybrid boron reinforced polymer matrix composition from powder pre-impregnated fiber tow bundles and a linear array of boron fibers. The boron fibers are applied onto the powder pre-impregnated fiber tow bundles and then are processed within a processing component having an impregnation bar assembly. After passing through variable-dimension forming nip-rollers, the powder pre-impregnated fiber tow bundles with the boron fibers become a hybrid boron reinforced polymer matrix composite tape. A driving mechanism pulls the powder pre-impregnated fiber tow bundles with boron fibers through the processing line of the apparatus and a take-up spool collects the formed hybrid boron-fiber reinforced polymer matrix composite tape.

Process to produce lithium-polymer batteries

DOEpatents

MacFadden, Kenneth Orville

1998-01-01

A polymer bonded sheet product suitable for use as an electrode in a non-aqueous battery system. A porous electrode sheet is impregnated with a solid polymer electrolyte, so as to diffuse into the pores of the electrode. The composite is allowed to cool, and the electrolyte is entrapped in the porous electrode. The sheet products composed have the solid polymer electrolyte composition diffused into the active electrode material by melt-application of the solid polymer electrolyte composition into the porous electrode material sheet. The solid polymer electrolyte is maintained at a temperature that allows for rapid diffusion into the pores of the electrode. The composite electrolyte-electrode sheets are formed on current collectors and can be coated with solid polymer electrolyte prior to battery assembly. The interface between the solid polymer electrolyte composite electrodes and the solid polymer electrolyte coating has low resistance.

Process and Microstructure to Achieve Ultra-high Dielectric Constant in Ceramic-Polymer Composites.

PubMed

Zhang, Lin; Shan, Xiaobing; Bass, Patrick; Tong, Yang; Rolin, Terry D; Hill, Curtis W; Brewer, Jeffrey C; Tucker, Dennis S; Cheng, Z-Y

2016-10-21

Influences of process conditions on microstructure and dielectric properties of ceramic-polymer composites are systematically studied using CaCu 3 Ti 4 O 12 (CCTO) as filler and P(VDF-TrFE) 55/45 mol.% copolymer as the matrix by combining solution-cast and hot-pressing processes. It is found that the dielectric constant of the composites can be significantly enhanced-up to about 10 times - by using proper processing conditions. The dielectric constant of the composites can reach more than 1,000 over a wide temperature range with a low loss (tan δ ~ 10 -1 ). It is concluded that besides the dense structure of composites, the uniform distribution of the CCTO particles in the matrix plays a key role on the dielectric enhancement. Due to the influence of the CCTO on the microstructure of the polymer matrix, the composites exhibit a weaker temperature dependence of the dielectric constant than the polymer matrix. Based on the results, it is also found that the loss of the composites at low temperatures, including room temperature, is determined by the real dielectric relaxation processes including the relaxation process induced by the mixing.

Process and Microstructure to Achieve Ultra-high Dielectric Constant in Ceramic-Polymer Composites

NASA Astrophysics Data System (ADS)

Zhang, Lin; Shan, Xiaobing; Bass, Patrick; Tong, Yang; Rolin, Terry D.; Hill, Curtis W.; Brewer, Jeffrey C.; Tucker, Dennis S.; Cheng, Z.-Y.

2016-10-01

Influences of process conditions on microstructure and dielectric properties of ceramic-polymer composites are systematically studied using CaCu3Ti4O12 (CCTO) as filler and P(VDF-TrFE) 55/45 mol.% copolymer as the matrix by combining solution-cast and hot-pressing processes. It is found that the dielectric constant of the composites can be significantly enhanced-up to about 10 times - by using proper processing conditions. The dielectric constant of the composites can reach more than 1,000 over a wide temperature range with a low loss (tan δ ~ 10-1). It is concluded that besides the dense structure of composites, the uniform distribution of the CCTO particles in the matrix plays a key role on the dielectric enhancement. Due to the influence of the CCTO on the microstructure of the polymer matrix, the composites exhibit a weaker temperature dependence of the dielectric constant than the polymer matrix. Based on the results, it is also found that the loss of the composites at low temperatures, including room temperature, is determined by the real dielectric relaxation processes including the relaxation process induced by the mixing.

Process and Microstructure to Achieve Ultra-high Dielectric Constant in Ceramic-Polymer Composites

PubMed Central

Zhang, Lin; Shan, Xiaobing; Bass, Patrick; Tong, Yang; Rolin, Terry D.; Hill, Curtis W.; Brewer, Jeffrey C.; Tucker, Dennis S.; Cheng, Z.-Y.

2016-01-01

Influences of process conditions on microstructure and dielectric properties of ceramic-polymer composites are systematically studied using CaCu3Ti4O12 (CCTO) as filler and P(VDF-TrFE) 55/45 mol.% copolymer as the matrix by combining solution-cast and hot-pressing processes. It is found that the dielectric constant of the composites can be significantly enhanced–up to about 10 times – by using proper processing conditions. The dielectric constant of the composites can reach more than 1,000 over a wide temperature range with a low loss (tan δ ~ 10−1). It is concluded that besides the dense structure of composites, the uniform distribution of the CCTO particles in the matrix plays a key role on the dielectric enhancement. Due to the influence of the CCTO on the microstructure of the polymer matrix, the composites exhibit a weaker temperature dependence of the dielectric constant than the polymer matrix. Based on the results, it is also found that the loss of the composites at low temperatures, including room temperature, is determined by the real dielectric relaxation processes including the relaxation process induced by the mixing. PMID:27767184

Laser hybrid joining of plastic and metal components for lightweight components

NASA Astrophysics Data System (ADS)

Rauschenberger, J.; Cenigaonaindia, A.; Keseberg, J.; Vogler, D.; Gubler, U.; Liébana, F.

2015-03-01

Plastic-metal hybrids are replacing all-metal structures in the automotive, aerospace and other industries at an accelerated rate. The trend towards lightweight construction increasingly demands the usage of polymer components in drive trains, car bodies, gaskets and other applications. However, laser joining of polymers to metals presents significantly greater challenges compared with standard welding processes. We present recent advances in laser hybrid joining processes. Firstly, several metal pre-structuring methods, including selective laser melting (SLM) are characterized and their ability to provide undercut structures in the metal assessed. Secondly, process parameter ranges for hybrid joining of a number of metals (steel, stainless steel, etc.) and polymers (MABS, PA6.6-GF35, PC, PP) are given. Both transmission and direct laser joining processes are presented. Optical heads and clamping devices specifically tailored to the hybrid joining process are introduced. Extensive lap-shear test results are shown that demonstrate that joint strengths exceeding the base material strength (cohesive failure) can be reached with metal-polymer joining. Weathering test series prove that such joints are able to withstand environmental influences typical in targeted fields of application. The obtained results pave the way toward implementing metalpolymer joints in manufacturing processes.

New Materials for the Repair of Polyimide Electrical Wire Insulation

NASA Technical Reports Server (NTRS)

2008-01-01

Two viable polyimide backbone materials have been identified that will allow the repair of polyimide electrical wire insulation found on the Space Shuttle and other aging aircraft. This identification is the outcome of ongoing efforts to assess the viability of using such polyimides and polyimide precursors (polyamic acids [PAAs]) as repair materials for aging polyimide electrical wire insulation. These repair materials were selected because they match the chemical makeup of the underlying wire insulation as closely as possible. This similarity allows for maximum compatibility, coupled with the outstanding physical properties of polyimides. The two polyimide backbone materials allow the polymer to be extremely flexible and to melt at low temperatures. A polymer chain end capping group that allows the polymer to crosslink into a nonflowable repair upon curing at around 200 C was also identified.

Facile and green preparation of novel adsorption materials by combining sol-gel with ion imprinting technology for selective removal of Cu(II) ions from aqueous solution

NASA Astrophysics Data System (ADS)

Ren, Zhongqi; Zhu, Xinyan; Du, Jian; Kong, Delong; Wang, Nian; Wang, Zhuo; Wang, Qi; Liu, Wei; Li, Qunsheng; Zhou, Zhiyong

2018-03-01

A novel green adsorption polymer was prepared by ion imprinted technology in conjunction with sol-gel process under mild conditions for the selective removal of Cu(II) ions from aqueous solution. Effects of preparation conditions on adsorption performance of prepared polymers were studied. The ion-imprinted polymer was prepared using Cu(II) ion as template, N-[3-(2-aminoethylamino) propyl] trimethoxysilane (AAPTMS) as functional monomer and tetraethyl orthosilicate (TEOS) as cross-linker. Water was used as solvent in the whole preparation process. The imprinted and non-imprinted polymers were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), atomic force microscope (AFM), Brunauer, Emmett and Teller (BET) and zeta potential. Three-dimensional network structure was formed and functional monomer was successfully cross-linked into the network structure of polymers. Effects of adsorption conditions on adsorption performance of prepared polymers were studied too. The pH value is of great influence on adsorption behavior. Adsorption by ion-imprinted polymer was fast (adsorption equilibrium was reached within 60 min). The adsorption capacity of Cu(II) ion-imprinted polymer was always larger than that of non-imprinted polymer. Pseudo-second-order kinetics model and Freundlich isotherm model fitted well with adsorption data. The maximum adsorption capacity of Cu(II) ion-imprinted polymer was 39.82 mg·g-1. However, the preparation conditions used in this work are much milder than those reported in literatures. The Cu(II) ion-imprinted polymer showed high selectivity and relative selectivity coefficients for Pb(II), Ni(II), Cd(II) and Co(II). In addition, the prepared ion-imprinted polymer could be reused several times without significant loss of adsorption capacity.

Aggregation of flexible polyelectrolytes: Phase diagram and dynamics.

PubMed

Tom, Anvy Moly; Rajesh, R; Vemparala, Satyavani

2017-10-14

Similarly charged polymers in solution, known as polyelectrolytes, are known to form aggregated structures in the presence of oppositely charged counterions. Understanding the dependence of the equilibrium phases and the dynamics of the process of aggregation on parameters such as backbone flexibility and charge density of such polymers is crucial for insights into various biological processes which involve biological polyelectrolytes such as protein, DNA, etc. Here, we use large-scale coarse-grained molecular dynamics simulations to obtain the phase diagram of the aggregated structures of flexible charged polymers and characterize the morphology of the aggregates as well as the aggregation dynamics, in the presence of trivalent counterions. Three different phases are observed depending on the charge density: no aggregation, a finite bundle phase where multiple small aggregates coexist with a large aggregate and a fully phase separated phase. We show that the flexibility of the polymer backbone causes strong entanglement between charged polymers leading to additional time scales in the aggregation process. Such slowing down of the aggregation dynamics results in the exponent, characterizing the power law decay of the number of aggregates with time, to be dependent on the charge density of the polymers. These results are contrary to those obtained for rigid polyelectrolytes, emphasizing the role of backbone flexibility.

Pushing the polymer envelope

NASA Astrophysics Data System (ADS)

Tolley, Paul R.

2005-09-01

The pressure to "push the polymer envelope" is clear, given the exploding range of demanding applications with optical components. There are two keys to success: 1. Expanded range of polymers with suitable optical properties. 2. Sophisticated manufacturing process options with an overall system perspective: -Tolerances and costs established relative to need (proof-of-concept, prototype, low to high volume production). -Designed to integrate into an assembly that meets all environmental constraints, not just size and weight, which are natural polymer advantages. (Withstanding extreme temperatures and chemical exposure is often critical, as are easy clean-up and general resistance to surface damage.) -Highly repeatable. The thesis of this paper is that systematically innovating processes we already understand on materials we already know can deliver big returns. To illustrate, we introduce HRDT1, High Refraction Diamond Turning, a patent-pending processing option to significantly reduce total costs for high index, high thermal applications.

Controlled thermal expansion printed wiring boards based on liquid crystal polymer dielectrics

NASA Technical Reports Server (NTRS)

Knoll, Thomas E.; Blizard, Kent; Jayaraj, K.; Rubin, Leslie S.

1994-01-01

Dielectric materials based on innovative Liquid Crystal Polymers (LCP's) have been used to fabricate surface mount printed wiring boards (PWB's) with a coefficient of thermal expansion matched to leadless ceramic chip carriers. Proprietary and patented polymer processing technology has resulted in self reinforcing material with balanced in-plane mechanical properties. In addition, LCP's possess excellent electrical properties, including a low dielectric constant (less than 2.9) and very low moisture absorption (less than 0.02%). LCP-based multilayer boards processed with conventional drilling and plating processes show improved performance over other materials because they eliminate the surface flatness problems of glass or aramid reinforcements. Laser drilling of blind vias in the LCP dielectric provides a very high density for use in direct chip attach and area array packages. The material is ideally suited for MCM-L and PCMCIA applications fabricated with very thin dielectric layers of the liquid crystal polymer.

Processing of continuous fiber reinforced ceramic composites for ultra high temperature applications using organosilicon polymer precursors

NASA Astrophysics Data System (ADS)

Nicholas, James Robert

The current work is on the development of continuous fiber reinforced ceramic materials (CFCCs) for use in ultra high temperature applications. These applications subject materials to extremely high temperatures(> 2000°C). Monolithic ceramics are currently being used for these applications, but the tendency to fail catastrophically has driven the need for the next generation of material. Reinforcing with continuous fibers significantly improves the toughness of the monolithic materials; however, this is a manufacturing challenge. The development of commercial, low-viscosity preceramic polymers provides new opportunities to fabricate CFCCs. Preceramic polymers behave as polymers at low temperatures and are transformed into ceramics upon heating to high temperatures. The polymer precursors enable the adaptation of well-established polymer processing techniques to produce high quality materials at relatively low cost. In the present work, SMP-10 from Starfire Systems, and PURS from KiON Corp. were used to manufacture ZrB2-SiC/SiC CFCCs using low cost vacuum bagging process in conjunction with the polymer infiltration and pyrolysis process. The microstructure was investigated using scanning electron microscopy and it was determined that the initial greenbody cure produced porosity of both closed and open pores. The open pores were found to be more successfully re-infiltrated using neat resin compared to slurry reinfiltrate; however, the closed pores were found to be impenetrable during subsequent reinfiltrations. The mechanical performance of the manufactured samples was evaluated using flexure tests and found the fiber reinforcement prevented catastrophic failure behavior by increasing fracture toughness. Wedge sample were fabricated and evaluated to demonstrate the ability to produce CFCC of complex geometry.

Effect of Processing Parameters on the Morphology of PVDF Electrospun Nanofiber

NASA Astrophysics Data System (ADS)

Zulfikar, M. A.; Afrianingsih, I.; Nasir, M.; Alni, A.

2018-03-01

Electrospinning is a process that produces continuous polymer fibers with diameters in the submicron range through the action of an external electric field imposed on a polymer solution or melt. Because of the tiny diameter in several hundreds of nanometers and the high porosity, electrospun membranes show potential applications in extensive areas such as filtration systems, biomedical tissue templates, drug delivery membranes, and so on. In the electrospinning process, some parameters such as polymer concentration, feeding rate of the polymer solution, additives, humidity, viscosity, surface tension, applied voltage, and nozzle-to ground collector distance will affect the fiber diameter and morphology. In this work, we have evaluated the effects of two processing parameters including the flow rate of the polymer solution and nozzle-to ground collector distance, on the morphology of the fibers formed. The solutions used in the electrospinning experiments were prepared using Poly(vinylidene fluoride) (PVDF). This material was dissolved in N,N-dimethylformamide (DMF) to make solutions with concentrations of 20 wt%. These solutions was electrospun using a 5 mL plastic syringe with an 8 gauge stainless needle at an applied voltage of 20.0 kV, a flow rate of 0.02-0.04 mL/min and nozzle-to ground collector distance of 12 and 15 cm. Electrospinning of PVDF polymer solution was performed in horizontal alignment having a grounded aluminum foil which serves as a collector. The nanofibers obtained were characterized by polarizing optical microscope. We find that the low flow rate of the polymer solution and nozzle-to ground collector distance are strongly correlated with the formation of bead defects in the fibers.

High-speed electro-optic polymers: mm-Wave applications and silica planar lightwave circuit integration

NASA Astrophysics Data System (ADS)

Chang, Daniel H.

The development of high speed polymer electro-optic modulators has seen steady and significant progress in recent years, enabling novel applications in RF-Photonics. Two of these are described in this Thesis: an Opto-Electronic Oscillator (OEO), which is a hybrid RF and optical oscillator capable of high spectral purity, and Photonic Time-Stretch, which is a signal processing technique for waveform spectral shifting with application to photonically-assisted A/D conversion. In both cases, the operating frequencies achieved have been the highest demonstrated to date. Application of this promising material to more complicated devices, however, is stymied by insertion loss performance. Current loss figures, while acceptable for single modulators, are too high for large arrays of modulators or intrinsically long devices such as AWGs or photonic-RF phase shifters. This is especially frustrating in light of a key virtue which polymers possess as a photonic material: its photolithographic process-ability makes patterning complex devices possible. Indeed, the current ascendancy of silica-based waveguide devices can be attributed largely to the same reason. In this Thesis, we also demonstrate the first hybrid device composed of silica planar lightwave circuits (PLCs) and polymer planar waveguides. Our approach utilizes grayscale lithography to enable vertical coupling between polymer and silica layers, minimizing entanglement of their respective fabrication processes. We have achieved coupling excess loss figures on the order of 1dB. We believe this is the natural next step in the development of electro-optic polymer devices. The two technologies are highly complementary. Silica PLCs, with excellent propagation loss and fiber coupling, are ideally suited for long passive waveguiding. By endowing them with the high-speed phase shifting capability offered by polymers, active wideband photonic devices of increasing complexity and array size can be contemplated.

Dispersions of polymer ionomers: I.

PubMed

Capek, Ignác

2004-12-31

The principal subject discussed in the current paper is the effect of ionic functional groups in polymers on the formation of nontraditional polymer materials, polymer blends or polymer dispersions. Ionomers are polymers that have a small amount of ionic groups distributed along a nonionic hydrocarbon chain. Specific interactions between components in a polymer blend can induce miscibility of two or more otherwise immiscible polymers. Such interactions include hydrogen bonding, ion-dipole interactions, acid-base interactions or transition metal complexation. Ion-containing polymers provide a means of modifying properties of polymer dispersions by controlling molecular structure through the utilization of ionic interactions. Ionomers having a relatively small number of ionic groups distributed usually along nonionic organic backbone chains can agglomerate into the following structures: (1) multiplets, consisting of a small number of tightly packed ion pairs; and (2) ionic clusters, larger aggregates than multiplets. Ionomers exhibit unique solid-state properties as a result of strong associations among ionic groups attached to the polymer chains. An important potential application of ionomers is in the area of thermoplastic elastomers, where the associations constitute thermally reversible cross-links. The ionic (anionic, cationic or polar) groups are spaced more or less randomly along the polymer chain. Because in this type of ionomer an anionic group falls along the interior of the chain, it trails two hydrocarbon chain segments, and these must be accommodated sterically within any domain structure into which the ionic group enters. The primary effects of ionic functionalization of a polymer are to increase the glass transition temperature, the melt viscosity and the characteristic relaxation times. The polymer microstructure is also affected, and it is generally agreed that in most ionomers, microphase-separated, ion-rich aggregates form as a result of strong ion-dipole attractions. As a consequence of this new phase, additional relaxation processes are often observed in the viscoelastic behavior of ionomers. Light functionalization of polymers can increase the glass transition temperature and gives rise to two new features in viscoelastic behavior: (1) a rubbery plateau above T(g) and (2) a second loss process at elevated temperatures. The rubbery plateau was due to the formation of a physical network. The major effect of the ionic aggregate was to increase the longer time relaxation processes. This in turn increases the melt viscosity and is responsible for the network-like behavior of ionomers above the glass transition temperature. Ionomers rich in polar groups can fulfill the criteria for the self-assembly formation. The reported phenomenon of surface micelle formation has been found to be very general for these materials.

Nanotechnology for the Solid Waste Reduction of Military Food Packaging

DTIC Science & Technology

2015-02-01

processability of the polymer (i.e. viscosity ), as is characteristic with conventional macroscopic fillers. When dispersed throughout the polymer and...approximately half the 3 Figure 4. Conventional Composites vs. Nanocomposites Layer ed Clay M o n o m er In Intercalated Na noc om pos ite...polymer/ clay layers. Exfoliation occurs when the clay platelets become further separated by the polymer chains. The separation distance can be from 80

Effects of Temperature and Steam Environment on Fatigue Behavior of Three SIC/SIC Ceramic Matrix Composites

DTIC Science & Technology

2008-09-01

Infiltration (CVI), Chemical Vapor Deposition (CVD) and polymer impregnation/ pyrolysis (PIP) [5:20, 32]. The SiC fibers currently... composite was infiltrated with a mixture of polymer , filler particles and solvent. During pyrolysis under nitrogen at temperatures > 1000 °C, the...using polymer infiltration and pyrolysis (PIP) method. Polymer infiltration and pyrolysis processing method allows near-net-shape molding and

Electrical conduction in polymer dielectrics

NASA Technical Reports Server (NTRS)

Cotts, D. B.

1985-01-01

The use of polymer dielectrics with moderate resistivities could reduce or eliminate problems associated with spacecraft charging. The processes responsible for conduction and the properties of electroactive polymers are reviewed, and correlations drawn between molecular structure and electrical conductivity. These structure-property relationships led to the development of several new electroactive polymer compositions and the identification of several systems that have the requisite thermal, mechanical, environmental and electrical properties for use in spacecraft.

DNA translocation across protein channels: How does a polymer worm through a hole?

NASA Astrophysics Data System (ADS)

Muthukumar, M.

2001-03-01

Free energy barriers control the translocation of polymers through narrow channels. Based on an analogy with the classical nucleation and growth process, we have calculated the translocation time and its dependencies on the length, stiffness, and sequence of the polymer, solution conditions, and the strength of the driving electrochemical potential gradient. Our predictions will be compared with experimental results and prospects of reading polymer sequences.

Water-soluble polymers for recovery of metal ions from aqueous streams

DOEpatents

Smith, Barbara F.; Robison, Thomas W.

1998-01-01

A process of selectively separating a target metal contained in an aqueous solution by contacting the aqueous solution containing a target metal with an aqueous solution including a water-soluble polymer capable of binding with the target metal for sufficient time whereby a water-soluble polymer-target metal complex is formed, and, separating the solution including the water-soluble polymer-target metal complex from the solution is disclosed.

Carbon doped PDMS: conductance stability over time and implications for additive manufacturing of stretchable electronics

NASA Astrophysics Data System (ADS)

Tavakoli, Mahmoud; Rocha, Rui; Osorio, Luis; Almeida, Miguel; de Almeida, Anibal; Ramachandran, Vivek; Tabatabai, Arya; Lu, Tong; Majidi, Carmel

2017-03-01

Carbon doped PDMS (cPDMS), has been used as a conductive polymer for stretchable electronics. Compared to liquid metals, cPDMS is low cost and is easier to process or to print with an additive manufacturing process. However, changes on the conductance of the carbon based conductive PDMS (cPDMS) were observed over time, in particular after integration of cPDMS and the insulating polymer. In this article we investigate the process parameters that lead to improved stability over conductance of the cPDMS over time. Slight modifications to the fabrication process parameters were conducted and changes on the conductance of the samples for each method were monitored. Results suggested that change of the conductance happens mostly after integration of a pre-polymer over a cured cPDMS, and not after integration of the cPDMS over a cured insulating polymer. We show that such changes can be eliminated by adjusting the integration priority between the conductive and insulating polymers, by selecting the right curing temperature, changing the concentration of the carbon particles and the thickness of the conductive traces, and when possible by changing the insulating polymer material. In this way, we obtained important conclusions regarding the effect of these parameters on the change of the conductance over time, that should be considered for additive manufacturing of soft electronics. Also, we show that these changes can be possibly due to the diffusion from PDMS into cPDMS.

Investigation of the role of flocculation conditions in recuperative thickening on dewatering performance and biogas production.

PubMed

Cobbledick, Jeffrey; Zhang, Victor; Rollings-Scattergood, Sasha; Latulippe, David R

2017-11-01

There is considerable interest in recuperative thickening (RT), the recycling of partially digested solids in an anaerobic digester outlet stream back into the incoming feed, as a 'high-performance' process to increase biogas production, increase system capacity, and improve biosolids stabilization. While polymer flocculation is commonly used in full-scale RT operations, no studies have investigated the effect of flocculation conditions on RT process performance. Our goal was to investigate the effect of polymer type and dosage conditions on dewatering performance and biogas production in a lab-scale RT system. The type of polymer flocculant significantly affected dewatering performance. For example, the 440 LH polymer (low molecular weight (MW) polyacrylamide) demonstrated lower capillary suction time (CST) and filtrate total suspended solids (TSS) values than the C-6267 polymer (high MW polyacrylamide). An examination of the dewatering performance of RT digesters with different polymers found a strong correlation between CST and filtrate TSS. The type of polymer flocculant had no significant effect on biogas productivity or composition; the methane content was greater than 60% in good agreement with typical results. The optimization of the polymer flocculation conditions is a critical task for which the lab-scale RT system used in this work is ideally suited.

Light weight polymer matrix composite material

NASA Technical Reports Server (NTRS)

Bowles, Kenneth J. (Inventor); Lowell, Carl E. (Inventor)

1991-01-01

A graphite fiber reinforced polymer matrix is layed up, cured, and thermally aged at about 750.degree. F. in the presence of an inert gas. The heat treatment improves the structural integrity and alters the electrical conductivity of the materials. In the preferred embodiment PMR-15 polyimides and Celion-6000 graphite fibers are used.

Characterizing Fluorotelomer and Polyfluoroalkyl Substances in New and Aged Fluorotelomer-Based Polymers for Degradation Studies with GC/MS and LC/MS/MS

EPA Science Inventory

Fluorotelomer-based polymers (FTPs), the dominant product of the fluorotelomer industry, are antistaining and antiwetting agents that permeate the products and surfaces of modern society. However, the degree to which these materials expose humans and the environment to fluorotelo...

Solid phase graft copolymerization of acrylic monomers onto thermoplastics and their use as blend compatibilizers

NASA Astrophysics Data System (ADS)

Subramanian, Srinivas

This research work is an extension of some of the earlier work done on the development of solid phase grafting technique to graft various monomers onto polymers as well as postulation of the usefulness of the graft copolymers thus synthesized. Polystyrene grafted with acrylic acid, previously developed in bench scale, was synthesized in pilot-plant scale batches. Process parameter studies on the grafting of acrylic acid onto polypropylene and developmental studies on the grafting of maleic anhydride onto polystyrene were also done. Polymers grafted with polar molecules such as maleic anhydride and acrylic acid have been used to compatibilize immiscible blends of polar and non-polar polymers. On the same note, the applicability of the solid phase graft copolymers as blend compatibilizers were investigated and their performance was compared to commercially available compatibilizers. Solid phase graft copolymerization process is a technique to synthesize graft copolymers. Some of its salient features are use of minimal solvent to conduct the reaction and easy equipment modification. It is a low pressure and low temperature process. This technique provides a viable alternative to the environmentally hazardous, and time consuming conventional process currently in use. Hence, development of this technique could be beneficial not only to the plastics industry, but also to mankind. Also, this technique provides a low-cost and extremely easy method to develop graft copolymers such as acrylic acid functionalized polymers that are rapidly gaining popularity as blend compatibilizers and polymer reinforcing agents. A study that proves the potential of these solid phase graft copolymers as good blend compatibilizers for industrially important immiscible polymers will develop interest in the industries about this grafting process. The free radical solid phase graft copolymerization process was carried in a modified Brabender-type mixer fitted with specially designed blades to promote efficient mixing of the polymer, initiator, monomer, and solvent. The grafting was qualitatively confirmed by means of a FTIR and quantitatively using titration. The polymer blends were synthesized in a single screw extruder. Rheological, morphological, thermal, mechanical, and molecular weight studies were done on these blends. The graft copolymers produced in larger batches had the same amount of graft content as those produced in smaller batches. This small success is a positive step towards the goal of commercializing this process. Grafting of acrylic acid onto polypropylene gave graft levels of 4 weight percent. However, the attempt to graft maleic anhydride onto polystyrene was not successful. The solid phase graft copolymers were successfully able to compatibilize the polymer blend systems studied (PS/PMMA, PS/nylon 6,6, PS/nylon 6, and PP/nylon 6). The properties of the blends compatibilized using the solid phase graft copolymers were comparable to and in some instances, better than those of the blends compatibilized with commercially available graft copolymers. The successful scale-up of the process, development of new graft copolymers and ability of copolymers to compatibilize blends augurs well for the solid phase grafting process.

The role of energetic ions from plasma in the creation of nanostructured materials and stable polymer surface treatments

NASA Astrophysics Data System (ADS)

Bilek, M. M. M.; Newton-McGee, K.; McKenzie, D. R.; McCulloch, D. G.

2006-01-01

Plasma processes for the synthesis of new materials as thin films have enabled the production of a wide variety of new materials. These include meta-stable phases, which are not readily found in nature, and more recently, materials with structure on the nanoscale. Study of plasma synthesis processes at the fundamental level has revealed that ion energy, depositing flux and growth surface temperature are the critical parameters affecting the microstructure and the properties of the thin film materials formed. In this paper, we focus on the role of ion flux and impact energy in the creation of thin films with nanoscale structure in the form of multilayers. We describe three synthesis strategies, based on the extraction of ions from plasma sources and involving modulation of ion flux and ion energy. The microstructure, intrinsic stress and physical properties of the multilayered samples synthesized are studied and related back to the conditions at the growth surface during deposition. When energetic ions of a non-condensing species are used, it is possible to place active groups on the surfaces of materials such as polymers. These active groups can then be used as bonding sites in subsequent chemical attachment of proteins or other macromolecules. If the energy of the non-condensing ions is increased to a few keV then modified layers buried under the surface can be produced. Here we describe a method by which the aging effect, which is often observed in plasma surface modifications on polymers, can be reduced and even eliminated using high energy ion bombardment.

Chemiluminescence as a condition monitoring method for thermal aging and lifetime prediction of an HTPB elastomer.

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

Gillen, Kenneth Todd; Minier, Leanna M. G.; Celina, Mathias C.

Chemiluminescence (CL) has been applied as a condition monitoring technique to assess aging related changes in a hydroxyl-terminated-polybutadiene based polyurethane elastomer. Initial thermal aging of this polymer was conducted between 110 and 50 C. Two CL methods were applied to examine the degradative changes that had occurred in these aged samples: isothermal 'wear-out' experiments under oxygen yielding initial CL intensity and 'wear-out' time data, and temperature ramp experiments under inert conditions as a measure of previously accumulated hydroperoxides or other reactive species. The sensitivities of these CL features to prior aging exposure of the polymer were evaluated on the basismore » of qualifying this method as a quick screening technique for quantification of degradation levels. Both the techniques yielded data representing the aging trends in this material via correlation with mechanical property changes. Initial CL rates from the isothermal experiments are the most sensitive and suitable approach for documenting material changes during the early part of thermal aging.« less

Leaching of nitroso rubber material removes uncured polymer

NASA Technical Reports Server (NTRS)

Bratfisch, W. A.; Gonzalez, R.

1972-01-01

New leaching process removes uncured polymer from nitroso rubber, elastomer used in presence of nitrogen tetroxide. Uncured portion is removed by controlled soaking of polymer slab in Freon TF. Leaching with Freon TF prevents nitroso rubber from adhering to adjoining surfaces and limiting its usefulness in either static or dynamic applications.

Excited-State Complexes of Conjugated Polymers: Novel Photophysical Processes and Optoelectronic Materials.

DTIC Science & Technology

1995-03-20

corresponding excited-state complexes were only recently discovered. The results of our extensive studies of intermolecular excimers and exciplexes of many...the luminescence of conjugated polymers. The luminescence and charge photogeneration in exciplexes of conjugated polymers with donor triarylamines will also be presented. jg

Process for removing polymer-forming impurities from naphtha fraction

DOEpatents

Kowalczyk, D.C.; Bricklemyer, B.A.; Svoboda, J.J.

1983-12-27

Polymer precursor materials are vaporized without polymerization or are removed from a raw naphtha fraction by passing the raw naphtha to a vaporization zone and vaporizing the naphtha in the presence of a wash oil while stripping with hot hydrogen to prevent polymer deposits in the equipment. 2 figs.

Process for removing polymer-forming impurities from naphtha fraction

DOEpatents

Kowalczyk, Dennis C.; Bricklemyer, Bruce A.; Svoboda, Joseph J.

1983-01-01

Polymer precursor materials are vaporized without polymerization or are removed from a raw naphtha fraction by passing the raw naphtha to a vaporization zone (24) and vaporizing the naphtha in the presence of a wash oil while stripping with hot hydrogen to prevent polymer deposits in the equipment.

Cyclopentadithiophene-Benzothiadiazole Donor-Acceptor Polymers as Prototypical Semiconductors for High-Performance Field-Effect Transistors.

PubMed

Li, Mengmeng; An, Cunbin; Pisula, Wojciech; Müllen, Klaus

2018-05-15

Donor-acceptor (D-A) conjugated polymers are of great interest as organic semiconductors, because they offer a rational tailoring of the electronic properties by modification of the donor and acceptor units. Nowadays, D-A polymers exhibit field-effect mobilities on the order of 10 -2 -10 0 cm 2 V -1 s -1 , while several examples showed a mobility over 10 cm 2 V -1 s -1 . The development of cyclopentadithiophene-benzothiadiazole (CDT-BTZ) copolymers one decade ago represents an important step toward high-performance organic semiconductors for field-effect transistors. The significant rise in field-effect mobility of CDT-BTZ in comparison to the existing D-A polymers at that time opened the door to a new research field with a large number of novel D-A systems. From this point, the device performance of CDT-BTZ was gradually improved by a systematic optimization of the synthesis and polymer structure as well as by an efficient solution processing into long-range ordered thin films. The key aspect was a comprehensive understanding of the relation between polymer structure and solid-state organization. Due to their fundamental role for the field of D-A polymers in general, this Account will for the first time explicitly focus on prototypical CDT-BTZ polymers, while other reviews provide an excellent general overview on D-A polymers. The first part of this Account discusses strategies for improving the charge carrier transport, focusing on chemical aspects. Improved synthesis as an essential stage toward high purity, and high molecular weight is a prerequisite for molecular order. The modification of substituents is a further crucial feature to tune the CDT-BTZ packing and self-assembly. Linear alkyl side chains facilitate intermolecular π-stacking interactions, while branched ones increase solubility and alter the polymer packing. Additional control over the supramolecular organization of CDT-BTZ polymers is introduced by alkenyl substituents via their cis-trans isomerization. The last discussed chemical concept is based on heteroatom variation within the CDT unit. The relationships found experimentally for CDT-BTZ between polymer chemical structure, solid-state organization, and charge carrier transport are explained by means of theoretical simulations. Besides the effects of molecular design, the second part of this Account discusses the processing conditions from solution. The film microstructure, defined as a mesoscopic domain organization, is critically affected by solution processing. Suitable processing techniques allow the formation of a long-range order and a uniaxial orientation of the CDT-BTZ chains, thus lowering the trapping density of grain boundaries for charge carriers. For instance, alignment of the CDT-BTZ polymer by dip-coating yields films with a pronounced structural and electrical anisotropy and favors a fast migration of charge carriers along the conjugated backbones in the deposition direction. By using film compression with the assistance of an ionic liquid, one even obtains CDT-BTZ films with a band-like transport and a transistor hole mobility of 10 cm 2 V -1 s -1 . This device performance is attributed to large domains in the compressed films being formed by CDT-BTZ with longer alkyl chains, which establish a fine balance between polymer interactions and growth kinetics during solvent evaporation. On the basis of the prototypical semiconductor CDT-BTZ, this Account provides general guidelines for achieving high-performance polymer transistors by taking into account the subtle balance of synthetic protocol, molecular design, and processing.

Decoration of multi-walled carbon nanotubes by polymer wrapping and its application in MWCNT/polyethylene composites.

PubMed

Hsiao, An-En; Tsai, Shu-Ya; Hsu, Mei-Wen; Chang, Shinn-Jen

2012-05-06

We dispersed the non-covalent functionalization of multi-walled carbon nanotubes (CNTs) with a polymer dispersant and obtained a powder of polymer-wrapped CNTs. The UV-vis absorption spectrum was used to investigate the optimal weight ratio of the CNTs and polymer dispersant. The powder of polymer-wrapped CNTs had improved the drawbacks of CNTs of being lightweight and difficult to process, and it can re-disperse in a solvent. Then, we blended the polymer-wrapped CNTs and polyethylene (PE) by melt-mixing and produced a conductive masterbatch and CNT/PE composites. The polymer-wrapped CNTs showed lower surface resistivity in composites than the raw CNTs. The scanning electron microscopy images also showed that the polymer-wrapped CNTs can disperse well in composites than the raw CNTs.

Structural Polymer-Based Carbon Nanotube Composite Fibers: Understanding the Processing–Structure–Performance Relationship

PubMed Central

Song, Kenan; Zhang, Yiying; Meng, Jiangsha; Green, Emily C.; Tajaddod, Navid; Li, Heng; Minus, Marilyn L.

2013-01-01

Among the many potential applications of carbon nanotubes (CNT), its usage to strengthen polymers has been paid considerable attention due to the exceptional stiffness, excellent strength, and the low density of CNT. This has provided numerous opportunities for the invention of new material systems for applications requiring high strength and high modulus. Precise control over processing factors, including preserving intact CNT structure, uniform dispersion of CNT within the polymer matrix, effective filler–matrix interfacial interactions, and alignment/orientation of polymer chains/CNT, contribute to the composite fibers’ superior properties. For this reason, fabrication methods play an important role in determining the composite fibers’ microstructure and ultimate mechanical behavior. The current state-of-the-art polymer/CNT high-performance composite fibers, especially in regards to processing–structure–performance, are reviewed in this contribution. Future needs for material by design approaches for processing these nano-composite systems are also discussed. PMID:28809290

Application of In Situ Fiberization for fabrication of improved strain isolation pads and graphite epoxy composites

NASA Technical Reports Server (NTRS)

Rosser, R. W.; Seibold, R. W.; Basiulis, D. I.

1982-01-01

The feasibility of applying the in situ fiberization process to the fabrication of strain isolation pads (SIP) for the Space Shuttle and to the fabrication of graphite-epoxy composites was evaluated. The ISF process involves the formation of interconnected polymer fiber networks by agitation of dilute polymer solutions under controlled conditions. High temperature polymers suitable for SIP use were fiberized and a successful fiberization of polychloro trifluoroethylene, a relatively high melting polymer, was achieved. Attempts to fiberize polymers with greater thermal stability were unsuccessful, apparently due to characteristics caused by the presence of aromaticity in the backbone of such materials. Graphite-epoxy composites were fabricated by interconnecting two dimensional arrays of graphite fiber with polypropylene IS fibers with subsequent epoxy resin impregnation. Mechanical property tests were performed on laminated panels of this material to evaluate intralaminar and interlaminar shear strength, and thus fracture toughness. Test results were generally unpromising.

Selective Photophysical Modification on Light-Emitting Polymer Films for Micro- and Nano-Patterning

PubMed Central

Zhang, Xinping; Liu, Feifei; Li, Hongwei

2016-01-01

Laser-induced cross-linking in polymeric semiconductors was utilized to achieve micro- and nano-structuring in thin films. Single- and two-photon cross-linking processes led to the reduction in both the refractive index and thickness of the polymer films. The resultant photonic structures combine the features of both relief- and phase-gratings. Selective cross-linking in polymer blend films based on different optical response of different molecular phases enabled “solidification” of the phase-separation scheme, providing a stable template for further photonic structuring. Dielectric and metallic structures are demonstrated for the fabrication methods using cross-linking in polymer films. Selective cross-linking enables direct patterning into polymer films without introducing additional fabrication procedures or additional materials. The diffraction processes of the emission of the patterned polymeric semiconductors may provide enhanced output coupling for light-emitting diodes or distributed feedback for lasers. PMID:28773248

Simulating the flow of entangled polymers.

PubMed

Masubuchi, Yuichi

2014-01-01

To optimize automation for polymer processing, attempts have been made to simulate the flow of entangled polymers. In industry, fluid dynamics simulations with phenomenological constitutive equations have been practically established. However, to account for molecular characteristics, a method to obtain the constitutive relationship from the molecular structure is required. Molecular dynamics simulations with atomic description are not practical for this purpose; accordingly, coarse-grained models with reduced degrees of freedom have been developed. Although the modeling of entanglement is still a challenge, mesoscopic models with a priori settings to reproduce entangled polymer dynamics, such as tube models, have achieved remarkable success. To use the mesoscopic models as staging posts between atomistic and fluid dynamics simulations, studies have been undertaken to establish links from the coarse-grained model to the atomistic and macroscopic simulations. Consequently, integrated simulations from materials chemistry to predict the macroscopic flow in polymer processing are forthcoming.

An investigation into the use of polymer blends to improve the printability of and regulate drug release from pharmaceutical solid dispersions prepared via fused deposition modeling (FDM) 3D printing.

PubMed

Alhijjaj, Muqdad; Belton, Peter; Qi, Sheng

2016-11-01

FDM 3D printing has been recently attracted increasing research efforts towards the production of personalized solid oral formulations. However, commercially available FDM printers are extremely limited with regards to the materials that can be processed to few types of thermoplastic polymers, which often may not be pharmaceutically approved materials nor ideal for optimizing dosage form performance of poor soluble compounds. This study explored the use of polymer blends as a formulation strategy to overcome this processability issue and to provide adjustable drug release rates from the printed dispersions. Solid dispersions of felodipine, the model drug, were successfully fabricated using FDM 3D printing with polymer blends of PEG, PEO and Tween 80 with either Eudragit E PO or Soluplus. As PVA is one of most widely used polymers in FDM 3D printing, a PVA based solid dispersion was used as a benchmark to compare the polymer blend systems to in terms of processability. The polymer blends exhibited excellent printability and were suitable for processing using a commercially available FDM 3D printer. With 10% drug loading, all characterization data indicated that the model drug was molecularly dispersed in the matrices. During in vitro dissolution testing, it was clear that the disintegration behavior of the formulations significantly influenced the rates of drug release. Eudragit EPO based blend dispersions showed bulk disintegration; whereas the Soluplus based blends showed the 'peeling' style disintegration of strip-by-strip. The results indicated that interplay of the miscibility between excipients in the blends, the solubility of the materials in the dissolution media and the degree of fusion between the printed strips during FDM process can be used to manipulate the drug release rate of the dispersions. This brings new insight into the design principles of controlled release formulations using FDM 3D printing. Copyright © 2016 Elsevier B.V. All rights reserved.

Supercritical carbon dioxide-processed resorbable polymer nanocomposites for bone graft substitute applications

NASA Astrophysics Data System (ADS)

Baker, Kevin C.

Numerous clinical situations necessitate the use of bone graft materials to enhance bone formation. While autologous and allogenic materials are considered the gold standards in the setting of fracture healing and spine fusion, their disadvantages, which include donor site morbidity and finite supply have stimulated research and development of novel bone graft substitute materials. Among the most promising candidate materials are resorbable polymers, composed of lactic and/or glycolic acid. While the characteristics of these materials, such as predictable degradation kinetics and biocompatibility, make them an excellent choice for bone graft substitute applications, they lack mechanical strength when synthesized with the requisite porous morphology. As such, porous resorbable polymers are often reinforced with filler materials. In the presented work, we describe the use of supercritical carbon dioxide (scCO2) processing to create porous resorbable polymeric constructs reinforced by nanostructured, organically modified Montmorillonite clay (nanoclay). scCO2 processing simultaneously disperses the nanoclay throughout the polymeric matrix, while imparting a porous morphology to the construct conducive to facilitating cellular infiltration and neoangiogenesis, which are necessary components of bone growth. With the addition of as little as 2.5wt% of nanoclay, the compressive strength of the constructs nearly doubles putting them on par with human cortico-cancellous bone. Rheological measurements indicate that the dominant mode of reinforcement of the nanocomposite constructs is the restriction of polymer chain mobility. This restriction is a function of the positive interaction between polymer chains and the nanoclay. In vivo inflammation studies indicate biocompatibility of the constructs. Ectopic osteogenesis assays have determined that the scCO2-processed nanocomposites are capable of supporting growth-factor induced bone formation. scCO 2-processed resorbable polymer nanocomposites composed of resorbable polymers and nanocaly exhibit physical, mechanical and biologic properties that make them excellent candidate materials for structural bone graft substitute applications.

Translocation of a Polymer Chain across a Nanopore: A Brownian Dynamics Simulation Study

NASA Technical Reports Server (NTRS)

Tian, Pu; Smith, Grant D.

2003-01-01

We carried out Brownian dynamics simulation studies of the translocation of single polymer chains across a nanosized pore under the driving of an applied field (chemical potential gradient). The translocation process can be either dominated by the entropic barrier resulted from restricted motion of flexible polymer chains or by applied forces (or chemical gradient across the wall), we focused on the latter case in our studies. Calculation of radius of gyrations at the two opposite sides of the wall shows that the polymer chains are not in equilibrium during the translocation process. Despite this fact, our results show that the one-dimensional diffusion and the nucleation model provide an excellent description of the dependence of average translocation time on the chemical potential gradients, the polymer chain length and the solvent viscosity. In good agreement with experimental results and theoretical predictions, the translocation time distribution of our simple model shows strong non-Gaussian characteristics. It is observed that even for this simple tubelike pore geometry, more than one peak of translocation time distribution can be generated for proper pore diameter and applied field strengths. Both repulsive Weeks-Chandler-Anderson and attractive Lennard-Jones polymer-nanopore interaction were studied, attraction facilitates the translocation process by shortening the total translocation time and dramatically improve the capturing of polymer chain. The width of the translocation time distribution was found to decrease with increasing temperature, increasing field strength, and decreasing pore diameter.

How Stress Treatments Influence the Performance of Biodegradable Poly(Butylene Succinate)-Based Copolymers with Thioether Linkages for Food Packaging Applications

PubMed Central

Genovese, Laura

2017-01-01

Biodegradable poly(butylene succinate) (PBS)-based random copolymers containing thioether linkages (P(BSxTDGSy)) of various compositions have been investigated and characterized from the gas barrier, thermal, and mechanical point of view, after food contact simulants or thermal and photoaging processes. Each stress treatment was performed on thin films and the results obtained have been compared to the same untreated film, used as a standard. Barrier properties with different gases (O2 and CO2) were evaluated, showing that the polymer chemical composition strongly influenced the permeability behavior. The relationships between the diffusion coefficients (D) and solubility (S) with polymer composition were also investigated. The results highlighted a correlation between polymer chemical structure and treatment. Gas transmission rate (GTR) mainly depending on the performed treatment, as GTR increased with the increase of TDGS co-unit amount. Thermal and mechanical tests allowed for the recording of variations in the degree of crystallinity and in the tensile properties. An increase in the crystallinity degree was recorded after contact with simulant liquids and aging treatments, together with a molecular weight decrease, a slight enhancement of the elastic modulus and a decrement of the elongation at break, proportional to the TDGS co-unit content. PMID:28867806

[Surgical treatment of recurrent urethral strictures in males after unsuccessful operations].

PubMed

Simon, V; Vacík, J; Michálek, J; Novák, V; Lopour, P; Spunda, M

2000-12-06

Subvesical obstructions of any origin represent a frequent and serious disorder occurring predominantly in males. Often it brings incontinence and/or erectility dysfunction, infection of urinary tract. Relapses of the acute pyelonephritis can turn into chronic tubulointersticial one and terminate in the renal insufficiency. To treat strictures, dilation, intermittent catheterization and recently stent introduction were used. Most suitable appears a stent from composite polymers. The aim of our work was to test properties of stents developed in the Institute of Macromolecular Chemistry ASCR. Stents from composite polymers, which are non-toxic, not-irritable can swell in body fluids and have mechanical properties similar to that of silicone rubber. Properties of the material are functionally graded and the casting or repoussé from the material can subsequently change its shape. Ten patients (males, aged 25 to 78 years) with long urethral strictures in its bulbocavernous part (50%) were treated with this method. Strictures were caused by pelvical fractures (4 times), prostate hypertrophy surgery (4 times), prolonged catheterizations (2 times). All patients were followed for 16 to 26 month and had no severities. Our results indicate that stent from composite polymers and silicone may have long-acting effects without irritation or crust formation and beneficially effected healing of the spongio-fibrous process.

How Stress Treatments Influence the Performance of Biodegradable Poly(Butylene Succinate)-Based Copolymers with Thioether Linkages for Food Packaging Applications.

PubMed

Siracusa, Valentina; Genovese, Laura; Munari, Andrea; Lotti, Nadia

2017-08-30

Biodegradable poly(butylene succinate) (PBS)-based random copolymers containing thioether linkages (P(BSxTDGSy)) of various compositions have been investigated and characterized from the gas barrier, thermal, and mechanical point of view, after food contact simulants or thermal and photoaging processes. Each stress treatment was performed on thin films and the results obtained have been compared to the same untreated film, used as a standard. Barrier properties with different gases (O₂ and CO₂) were evaluated, showing that the polymer chemical composition strongly influenced the permeability behavior. The relationships between the diffusion coefficients ( D ) and solubility ( S ) with polymer composition were also investigated. The results highlighted a correlation between polymer chemical structure and treatment. Gas transmission rate ( GTR ) mainly depending on the performed treatment, as GTR increased with the increase of TDGS co-unit amount. Thermal and mechanical tests allowed for the recording of variations in the degree of crystallinity and in the tensile properties. An increase in the crystallinity degree was recorded after contact with simulant liquids and aging treatments, together with a molecular weight decrease, a slight enhancement of the elastic modulus and a decrement of the elongation at break, proportional to the TDGS co-unit content.

Long term isothermal aging and thermal analysis of N-CYCAP polyimides

NASA Technical Reports Server (NTRS)

Sutter, James K.; Waters, John F.; Schverman, Marla A.

1991-01-01

The N-CYCAP polyimides utilize a (2,2) paracyclophane endcap that polymerizes and does not generate volatile gases during the cure process. These polyimides have both high glass temperatures (390 C) and an onset of decomposition in air of 560 C. Thermal oxidative stability (TOS) weight loss studies show that replacing 25 percent by weight of the paraphenylene diamine in the polymer backbone with metaphenylene diamine improves the weight loss characteristics. N-CYCAP neat resin samples performed better than PMR-II-50 when exposed at 343 and 371 C in air for up to 1000 hours. Preliminary composite studies show that both PMR-II-50 and N-CYCAP have better thermal stability when fabricated on T-40R. Higher isothermal aging temperatures of longer aging times are needed to determine the differences in TOS between composite samples of PMR-II-50 and N-CYCAP polyimides.

Studies of organic paint binders by NMR spectroscopy

NASA Astrophysics Data System (ADS)

Spyros, A.; Anglos, D.

2006-06-01

Nuclear magnetic resonance spectroscopy is applied to the study of aged binding media used in paintings, namely linseed oil, egg tempera and an acrylic medium. High resolution 1D and 2D NMR experiments establish the state of hydrolysis and oxidation of the linseed and egg tempera binders after five years of aging, by determining several markers sensitive to the hydrolytic and oxidative processes of the binder lipid fraction. The composition of the acrylic binder co-polymer is determined by 2D NMR spectroscopy, while the identification of a surfactant, poly(ethylene glycol), found in greater amounts in aged acrylic medium, is reported. The non-destructive nature of the proposed analytical NMR methodology, and minimization of the amount of binder material needed through the use of sophisticated cryoprobes and hyphenated LC-NMR techniques, make NMR attractive for the arts analyst, in view of its rapid nature and experimental simplicity.

Effect of an acid filler on hydrolysis and biodegradation of poly-lactic acid (PLA)

NASA Astrophysics Data System (ADS)

Iozzino, Valentina; Speranza, Vito; Pantani, Roberto

2015-12-01

The use of biodegradable polymers is certainly an excellent strategy to solve many of the problems related to the disposal of the traditional polymers, whose accumulation in the environment is harmful and damaging. In order to optimize the use of biodegradable polymers, it is very important to understand and control the transformation processes, the structures and the morphologies resulting from the process conditions used to produce the articles and, not least, the biodegradation. The latter is strictly dependent on the just mentioned variables. The poly-lactic acid, PLA, is a biodegradable polymer. Many studies have been carried out on the degradation process of this polymer. In the course of this work we performed degradation tests on the PLA, with a specific D-isomer content, having amorphous structure, and in particular of biodegradation and hydrolysis. An acid chemical, fumaric acid, was added to PLA with the objective of controlling the rate of hydrolysis and of biodegradation. The hydrolysis process was followed, as function of time, by means of different techniques: pH variation, variation of weight of samples and variation of crystallinity degree and glass transition temperature using DSC analysis. The samples were also analyzed in terms of biodegradability by means of a homemade respirometer apparatus, in controlled composting conditions.

Progress in radiation processing of polymers

NASA Astrophysics Data System (ADS)

Chmielewski, Andrzej G.; Haji-Saeid, Mohammad; Ahmed, Shamshad

2005-07-01

Modification in polymeric structure of plastic material can be brought either by conventional chemical means or by exposure to ionization radiation from ether radioactive sources or highly accelerated electrons. The prominent drawbacks of chemical cross-linking typically involve the generation of noxious fumes and by products of peroxide degradation. Both the irradiation sources have their merits and limitations. Increased utilization of electron beams for modification and enhancement of polymer materials has been in particular witnessed over the past 40 years. The paper highlights several recent cases of EB utilization to improve key properties of selected plastic products. In paper is provided a survey of radiation processing methods of industrial interest, encompassing technologies which are already commercially well established, through developments in the active R&D stage which show pronounced promise for future commercial use. Radiation cross-linking technologies discussed include: application in cable and wire, application in rubber tyres, radiation vulcanization of rubber latex, development of radiation crosslinked SiC fiber, polymer recycling, development of gamma compatible pp, hydrogels etc. Over the years, remarkable advancement has been achieved in radiation processing of natural polymers. Role of radiation in improving the processing of temperature of PCL for use as biodegradable polymer, in accelerated breakdown of cellulose into viscose and enhancement in yields of chitin/chitosan from sea-food waste, is described.

Supercritical Fluid Processing of Propellant Polymers

DTIC Science & Technology

1991-01-01

coffee decaffeination , spice extraction, and lipids purification. The processing principles have also long been well known and practiced in the...rn PL-TR-91 -3003 AD: AD-A234 285 Final Report Supercritical Fluid Processing for the period of Propellant Polymers September 1989 to September 1990...PROJECT TASK I’Ac K UNIT ELEMENT NO. NO. P:~53Co O 62302F 5730 0055 3𔃻U-- 11. TITLE (Include Security Classification) Supercritical Fluid Processing

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

NASA Astrophysics Data System (ADS)

Wegner, Andreas

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

Fluorinated benzothiadiazole-based conjugated polymers for high-performance polymer solar cells without any processing additives or post-treatments.

PubMed

Wang, Ning; Chen, Zheng; Wei, Wei; Jiang, Zhenhua

2013-11-13

Thanks to their many favorable advantages, polymer solar cells exhibit great potential for next-generation clean energy sources. Herein, we have successfully designed and synthesized a series of new fluorinated benzothiadiazole-based conjugated copolymers PBDT(TEH)-DT(H)BTff (P1), PBDT(TEH)-DT(EH)BTff (P2), and PBDT(HDO)-DT(H)BTff (P3). The power conversion efficiencies of 4.46, 6.20, and 8.30% were achieved for P1-, P2-, and P3-based devices within ~100 nm thickness active layers under AM 1.5G illumination without any processing additives or post-treatments, respectively. The PCE of 8.30% for P3 is the highest value for the reported traditional single-junction polymer solar cells via a simple fabrication architecture without any additives or post-treatments. In addition, it is noteworthy that P3 also allows making high efficient polymer solar cells with high PCEs of 7.27 and 6.56% under the same condition for ~200 and ~300 nm thickness active layers, respectively. Excellent photoelectric properties and good solubility make polymer P3 become an alternative material for high-performance polymer solar cells.

Covalent bond force profile and cleavage in a single polymer chain

NASA Astrophysics Data System (ADS)

Garnier, Lionel; Gauthier-Manuel, Bernard; van der Vegte, Eric W.; Snijders, Jaap; Hadziioannou, Georges

2000-08-01

We present here the measurement of the single-polymer entropic elasticity and the single covalent bond force profile, probed with two types of atomic force microscopes (AFM) on a synthetic polymer molecule: polymethacrylic acid in water. The conventional AFM allowed us to distinguish two types of interactions present in this system when doing force spectroscopic measurements: the first interaction is associated with adsorption sites of the polymer chains onto a bare gold surface, the second interaction is directly correlated to the rupture process of a single covalent bond. All these bridging interactions allowed us to stretch the single polymer chain and to determine the various factors playing a role in the elasticity of these molecules. To obtain a closer insight into the bond rupture process, we moved to a force sensor stable in position when measuring attractive forces. By optimizing the polymer length so as to fulfill the elastic stability conditions, we were able for the first time to map out the entire force profile associated with the cleavage of a single covalent bond. Experimental data coupled with molecular quantum mechanical calculations strongly suggest that the breaking bond is located at one end of the polymer chain.

Silylene-diethynyl-arylene polymers having liquid crystalline properties

DOEpatents

Barton, Thomas J.; Ding, Yiwei

1993-09-07

The present invention provides linear organosilicon polymers including diethynyl-(substituted)arylene units, and a process for their preparation. These novel polymers possess useful properties including electrical conductivity, liquid crystallinity, and/or photoluminescence. These polymers possess good solubility in organic solvents. A preferred example is produced according to the following reaction scheme. ##STR1## These polymers can be solvent-cast to yield excellent films and can also be pulled into fibers from concentrated solutions. All possess substantial crystallinity as revealed by DSC analysis and observation through a polarizing microscope, and possess liquid crystalline properties.

Method of forming a foamed thermoplastic polymer

DOEpatents

Duchane, David V.; Cash, David L.

1986-01-01

A method of forming a foamed thermoplastic polymer. A solid thermoplastic lymer 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 infusant solution permanently entrapped in the polymer. The polymer is then heated to volatilize the blowing agent and expand the polymer into a foamed state.

Morphology control in polymer blend fibers—a high throughput computing approach

NASA Astrophysics Data System (ADS)

Sesha Sarath Pokuri, Balaji; Ganapathysubramanian, Baskar

2016-08-01

Fibers made from polymer blends have conventionally enjoyed wide use, particularly in textiles. This wide applicability is primarily aided by the ease of manufacturing such fibers. More recently, the ability to tailor the internal morphology of polymer blend fibers by carefully designing processing conditions has enabled such fibers to be used in technologically relevant applications. Some examples include anisotropic insulating properties for heat and anisotropic wicking of moisture, coaxial morphologies for optical applications as well as fibers with high internal surface area for filtration and catalysis applications. However, identifying the appropriate processing conditions from the large space of possibilities using conventional trial-and-error approaches is a tedious and resource-intensive process. Here, we illustrate a high throughput computational approach to rapidly explore and characterize how processing conditions (specifically blend ratio and evaporation rates) affect the internal morphology of polymer blends during solvent based fabrication. We focus on a PS: PMMA system and identify two distinct classes of morphologies formed due to variations in the processing conditions. We subsequently map the processing conditions to the morphology class, thus constructing a ‘phase diagram’ that enables rapid identification of processing parameters for specific morphology class. We finally demonstrate the potential for time dependent processing conditions to get desired features of the morphology. This opens up the possibility of rational stage-wise design of processing pathways for tailored fiber morphology using high throughput computing.

Effect of γ irradiation on the properties of basalt fiber reinforced epoxy resin matrix composite

NASA Astrophysics Data System (ADS)

Li, Ran; Gu, Yizhuo; Yang, Zhongjia; Li, Min; Wang, Shaokai; Zhang, Zuoguang

2015-11-01

Gamma-ray (γ-ray) irradiation is a crucial reason for the aging in materials used for nuclear industry. Due to high specific strength and stiffness, light weight and good corrosion resistance, fiber reinforced composites are regarded as an alternative of traditional materials used on nuclear facilities. In this study, basalt fiber (BF)/AG80 epoxy composite laminates were fabricated by autoclave process and treated with 60Co gamma irradiation dose up to 2.0 MGy. Irradiation induced polymer chain scission and oxidation of AG80 resin were detected from physical and chemical analysis. The experimental results show that the tensile and flexural performances of irradiated BF/AG80 composite maintain stable and have a low amplitude attenuation respectively, and the interlaminar shear strength has increased from irradiation dose of 0-1.5 MGy. Furthermore, the comparison between the studied BF composite and reported polymer and composite materials was done for evaluating the γ resistance property of BF composite.

Time-Dependent ATR-FTIR Spectroscopic Studies on Fatty Acid Diffusion and the Formation of Metal Soaps in Oil Paint Model Systems.

PubMed

Baij, Lambert; Hermans, Joen J; Keune, Katrien; Iedema, Piet

2018-06-18

The formation of metal soaps (metal complexes of saturated fatty acids) is a serious problem affecting the appearance and structural integrity of many oil paintings. Tailored model systems for aged oil paint and time-dependent attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy were used to study the diffusion of palmitic acid and subsequent metal soap crystallization. The simultaneous presence of free saturated fatty acids and polymer-bound metal carboxylates leads to rapid metal soap crystallization, following a complex mechanism that involves both acid and metal diffusion. Solvent flow, water, and pigments all enhance metal soap crystallization in the model systems. These results contribute to the development of paint cleaning strategies, a better understanding of oil paint degradation, and highlight the potential of time-dependent ATR-FTIR spectroscopy for studying dynamic processes in polymer films. © 2018 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

An ionic liquid-gated polymer thin film transistor with exceptionally low "on" resistance

NASA Astrophysics Data System (ADS)

Algarni, Saud A.; Althagafi, Talal M.; Smith, Patrick J.; Grell, Martin

2014-05-01

We report the ionic liquid (IL) gating of a solution processed semiconducting polymer, poly(2,5-bis(3-hexadecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT). IL gating relies on the poor solubility of PBTTT, which requires hot chlorinated benzenes for solution processing. PBTTT, thus, resists dissolution even in IL, which otherwise rapidly dissolves semiconducting polymers. The resulting organic thin film transistors (OTFTs) display low threshold, very high carrier mobility (>3 cm2/Vs), and deliver high currents (in the order of 1 mA) at low operational voltages. Such OTFTs are interesting both practically, for the addressing of current-driven devices (e.g., organic LEDs), and for the study of charge transport in semiconducting polymers at very high carrier density.

Liquid crystalline polymers

NASA Technical Reports Server (NTRS)

1990-01-01

The remarkable mechanical properties and thermal stability of fibers fabricated from liquid crystalline polymers (LCPs) have led to the use of these materials in structural applications where weight savings are critical. Advances in processing of LCPs could permit the incorporation of these polymers into other than uniaxial designs and extend their utility into new areas such as nonlinear optical devices. However, the unique feature of LCPs (intrinsic orientation order) is itself problematic, and current understanding of processing with control of orientation falls short of allowing manipulation of macroscopic orientation (except for the case of uniaxial fibers). The current and desirable characteristics of LCPs are reviewed and specific problems are identified along with issues that must be addressed so that advances in the use of these unique polymers can be expedited.

Tuning relaxation dynamics and mechanical properties of polymer films of identical thickness

NASA Astrophysics Data System (ADS)

Kchaou, Marwa; Alcouffe, Pierre; Chandran, Sivasurender; Cassagnau, Philippe; Reiter, Günter; Al Akhrass, Samer

2018-03-01

Using dewetting as a characterization tool, we demonstrate that physical properties of thin polymer films can be regulated and tuned by employing variable processing conditions. For different molecular weights, the variable behavior of polystyrene films of identical thickness, prepared along systematically altered pathways, became predictable through a single parameter P , defined as the ratio of time required over time available for the equilibration of polymers. In particular, preparation-induced residual stresses, the corresponding relaxation times as well as the rupture probability of such films (of identical thickness) varied by orders of magnitude following scaling relations with P . Our experimental findings suggest that we can predictably enhance properties and hence maximize the performance of thin polymer films via appropriately chosen processing conditions.

Using a micro-molding process to fabricate polymeric wavelength filters

NASA Astrophysics Data System (ADS)

Chuang, Wei-Ching; Lee, An-Chen; Ho, Chi-Ting

2008-08-01

A procedure for fabricating a high aspect ratio periodic structure on a UV polymer at submicron order using holographic interferometry and molding processes is described. First, holographic interferometry using a He-Cd (325 nm) laser was used to create the master of the periodic line structure on an i-line sub-micron positive photoresist film. A 20 nm nickel thin film was then sputtered on the photoresist. The final line pattern on a UV polymer was obtained from casting against the master mold. Finally, a SU8 polymer was spun on the polymer grating to form a planar waveguide or a channel waveguide. The measurement results show that the waveguide length could be reduced for the waveguide having gratings with a high aspect ratio.

Diorganosilacetylene-alt-diorganosilvinylene polymers and a process densifying porous silicon-carbide bodies

DOEpatents

Barton, T.J.; Ijadi-Maghsoodi, S.; Pang, Y.

1994-05-17

The present invention provides linear organosilicon polymers including acetylene and vinylene moieties, and a process for their preparation. These diorganosilacetylene-alt-diorganosilvinylene linear polymers can be represented by the formula: --[--(R[sup 1])(R[sup 2])Si--C[triple bond]C-(R[sup 3])(R[sup 4])Si--CH[double bond]CH--][sub n]--, wherein n[>=]2; and each R[sup 1], R[sup 2], R[sup 3], and R[sup 4] is independently selected from the group consisting of hydrogen, halogen, alkyl, alkenyl, aryl, and aralkyl radicals. The polymers are soluble in organic solvents, air stable, and can be pulled into fibers or cast into films. They can be thermally converted into silicon carbide ceramic materials.

Investigation of the adhesion interface obtained through two-component injection molding

NASA Astrophysics Data System (ADS)

Fetecau, Catalin; Stan, Felicia; Dobrea, Daniel

2011-01-01

In this paper we study the interface strength obtained through two-component (2C) injection molding of LDPE-HDPE polymers. First, numerical simulation of the over-molding process is carried out using Moldflow technology. Second, butt-joint specimens were produced by over-molding under different process condition, and tested. Two injection sequences were considered, injection of LDPE on HDPE polymer, and HDLE on LDPE, respectively. To investigate the effects of the mold surface roughness on the polymers adhesion at interface, different inserts with different roughness are employed.

Process to produce lithium-polymer batteries

DOEpatents

MacFadden, K.O.

1998-06-30

A polymer bonded sheet product is described suitable for use as an electrode in a non-aqueous battery system. A porous electrode sheet is impregnated with a solid polymer electrolyte, so as to diffuse into the pores of the electrode. The composite is allowed to cool, and the electrolyte is entrapped in the porous electrode. The sheet products composed have the solid polymer electrolyte composition diffused into the active electrode material by melt-application of the solid polymer electrolyte composition into the porous electrode material sheet. The solid polymer electrolyte is maintained at a temperature that allows for rapid diffusion into the pores of the electrode. The composite electrolyte-electrode sheets are formed on current collectors and can be coated with solid polymer electrolyte prior to battery assembly. The interface between the solid polymer electrolyte composite electrodes and the solid polymer electrolyte coating has low resistance. 1 fig.

Very low band gap thiadiazoloquinoxaline donor-acceptor polymers as multi-tool conjugated polymers.

PubMed

Steckler, Timothy T; Henriksson, Patrik; Mollinger, Sonya; Lundin, Angelica; Salleo, Alberto; Andersson, Mats R

2014-01-29

Here we report on the synthesis of two novel very low band gap (VLG) donor-acceptor polymers (Eg ≤ 1 eV) and an oligomer based on the thiadiazoloquinoxaline acceptor. Both polymers demonstrate decent ambipolar mobilities, with P1 showing the best performance of ∼10(-2) cm(2) V(-1) s(-1) for p- and n-type operation. These polymers are among the lowest band gap polymers (≲0.7 eV) reported, with a neutral λmax = 1476 nm (P2), which is the farthest red-shifted λmax reported to date for a soluble processable polymer. Very little has been done to characterize the electrochromic aspects of VLG polymers; interestingly, these polymers actually show a bleaching of their neutral absorptions in the near-infrared region and have an electrochromic contrast up to 30% at a switching speed of 3 s.

Low molecular weight components of polymers used in packaging.

PubMed Central

Gilbert, S G

1975-01-01

The increasing use of polymers in packaging of foods and drugs focuses attention on the possible chronic toxicity relations of migrants from these polymers to the contents. Such migrants can arise from residues and additives in the polymers from manufacturing processes used in fabrication of packages. The origin and chemical nature of potential migrants, the methods of transfer, and principles involved in development of safety criteria for their regulation are discussed. PMID:1236793

Low density microcellular foams

DOEpatents

Aubert, James H.; Clough, Roger L.; Curro, John G.; Quintana, Carlos A.; Russick, Edward M.; Shaw, Montgomery T.

1987-01-01

Low density, microporous polymer foams are provided by a process which comprises forming a solution of polymer and a suitable solvent followed by rapid cooling of the solution to form a phase-separated system and freeze the phase-separated system. The phase-separated system comprises a polymer phase and a solvent phase, each of which is substantially continuous within the other. The morphology of the polymer phase prior to and subsequent to freezing determine the morphology of the resultant foam. Both isotropic and anisotropic foams can be produced. If isotropic foams are produced, the polymer and solvent are tailored such that the solution spontaneously phase-separates prior to the point at which any component freezes. The morphology of the resultant polymer phase determines the morphology of the resultant foam and the morphology of the polymer phase is retained by cooling the system at a rate sufficient to freeze one or both components of the system before a change in morphology can occur. Anisotropic foams are produced by forming a solution of polymer and solvent that will not phase separate prior to freezing of one or both components of the solution. In such a process, the solvent typically freezes before phase separation occurs. The morphology of the resultant frozen two-phase system determines the morphology of the resultant foam. The process involves subjecting the solution to essentially one-dimensional cooling. Means for subjecting such a solvent to one-dimensional cooling are also provided. Foams having a density of less than 0.1 g/cc and a uniform cell size of less than 10 .mu.m and a volume such that the foams have a length greater than 1 cm are provided.

Fundamentals of twin-screw extrusion polymer melting: Common pitfalls and how to avoid them

NASA Astrophysics Data System (ADS)

Andersen, Paul

2015-05-01

The process for compounding engineered polymer formulations is comprised of several unit operations. These typically include, but are not limited to: feedstock introduction, polymer melt-mixing, distributive/dispersive mixing of minerals/fibers, removal of volatiles, and pressurization for discharge. While each unit operation has an impact on process productivity and the quality of the finished product, polymer melt-mixing has a significantly greater impact than the others. First, it consumes 50, 60 or higher percent of the total system energy. Second, it generates the highest radial as well as particle-particle interactive pressure of any unit operation. Third, the negative impact on the process of any design flaws in the melt-mixing configuration is transmitted downstream to all subsequent unit operations. For example, a melt-mixing design that is too intense may degrade the polymer while one that is too weak may result in excessive breakage of glass fiber being fed downstream due to the polymer solidifying on the glass fiber and subsequently being re-melted. Another example of the impact of an incorrect melt-mixing configuration would be excessive abrasive wear. Adhesive wear is also possible as well as deformation on both barrel wall and screw elements due to high radial forces. Additionally, non-melting material present during the melt-mixing process could be compacted into "briquettes" by the high radial pressure and would have to be dispersed by subsequent downstream unit operations. Other potential issues associated with a non-optimal melting section are pre-mature and incomplete melting. The former is more of a concern with melting of powder feed stock while the latter is more probable with feed stock comprised of a broad range of particle sizes. However, the consequence of both is to convey unmolten polymer beyond the melting section. While this may not be perceived as a significant issue for most processes, it is an issue if the sole purpose of the process is to uniformly melt the feedstock. This is case for powder to pellet conversion of polyolefins and melt spinning of mono-filament.

Gibbs Ensemble Simulations of the Solvent Swelling of Polymer Films

NASA Astrophysics Data System (ADS)

Gartner, Thomas; Epps, Thomas, III; Jayaraman, Arthi

Solvent vapor annealing (SVA) is a useful technique to tune the morphology of block polymer, polymer blend, and polymer nanocomposite films. Despite SVA's utility, standardized SVA protocols have not been established, partly due to a lack of fundamental knowledge regarding the interplay between the polymer(s), solvent, substrate, and free-surface during solvent annealing and evaporation. An understanding of how to tune polymer film properties in a controllable manner through SVA processes is needed. Herein, the thermodynamic implications of the presence of solvent in the swollen polymer film is explored through two alternative Gibbs ensemble simulation methods that we have developed and extended: Gibbs ensemble molecular dynamics (GEMD) and hybrid Monte Carlo (MC)/molecular dynamics (MD). In this poster, we will describe these simulation methods and demonstrate their application to polystyrene films swollen by toluene and n-hexane. Polymer film swelling experiments, Gibbs ensemble molecular simulations, and polymer reference interaction site model (PRISM) theory are combined to calculate an effective Flory-Huggins χ (χeff) for polymer-solvent mixtures. The effects of solvent chemistry, solvent content, polymer molecular weight, and polymer architecture on χeff are examined, providing a platform to control and understand the thermodynamics of polymer film swelling.

Residual stresses in injection molded shape memory polymer parts

NASA Astrophysics Data System (ADS)

Katmer, Sukran; Esen, Huseyin; Karatas, Cetin

2016-03-01

Shape memory polymers (SMPs) are materials which have shape memory effect (SME). SME is a property which has the ability to change shape when induced by a stimulator such as temperature, moisture, pH, electric current, magnetic field, light, etc. A process, known as programming, is applied to SMP parts in order to alter them from their permanent shape to their temporary shape. In this study we investigated effects of injection molding and programming processes on residual stresses in molded thermoplastic polyurethane shape memory polymer, experimentally. The residual stresses were measured by layer removal method. The study shows that injection molding and programming process conditions have significantly influence on residual stresses in molded shape memory polyurethane parts.

An overview of the nonequilibrium behavior of polymer glasses

NASA Technical Reports Server (NTRS)

Tant, M. R.; Wilkes, G. L.

1981-01-01

It is pointed out that research efforts are at present being directed in two areas, one comprising experimental studies of this phenomenon in various glassy polymer systems and the other involving the development of a quantitative theory capable of satisfactorily predicting aging behavior for a variety of polymer materials under different conditions. Recent work in both these areas is surveyed. The basic principles of nonequilibrium behavior are outlined, with emphasis placed on changes in material properties with annealing below the glass transition temperature. Free volume theory and thermodynamic theory are discussed.

Hydrophilic Polymer-associated Ischemic Enterocolitis.

PubMed

Chavez, Jesus A; Chen, Wei; Frankel, Wendy L; Arnold, Christina A

2017-02-01

Hydrophilic polymer coating of medical devices serves to lubricate the device and prevent device-related complications. The coating can be mechanically disrupted and result in downstream injury via presumed thromboembolism. This process has been reported in the brain, heart, lung, and skin, and has been replicated through animal studies and in vitro histologic processing of the polymer coating. We report the first description of hydrophilic polymer-associated ischemic enterocolitis in a series of 7 specimens (small bowel=2, colon=4, aortic thrombus=1) from 3 patients. We report a 4% incidence among all patients with an ischemic bowel resection between April 29, 2014 and August 8, 2016. All patients developed bowel ischemia within 1 day of aortic repair, and all bowel resection specimens showed polymers, mainly in the submucosal vessels in areas of extensive ischemia. The polymers appeared as basophilic, intravascular, serpiginous structures. In a patient who developed acute paralysis after the aortic repair, identical polymers were identified in the aortic thrombus and the ischemic bowel segment. We demonstrate that the polymers display an altered morphology over time and with various graft types, and that the degrading polymers are associated with a foreign body giant cell reaction. Special stains can aid in diagnosis, with the polymers turquoise on a colloidal iron stain, pink on von Kossa and mucicarmine stains, and pale blue on trichrome. Clinical follow-up was available up to 115 weeks: 1 patient died, and 2 are alive and well. In summary, we report a new diagnostic entity to be considered in the differential diagnosis of iatrogenic ischemic injuries in the gastrointestinal tract. Awareness of this entity is important to elucidate the cause of ischemia and to prevent misdiagnosis of the polymers and their associated giant cell reaction as a parasitic infection, granulomatous vasculitis, sarcoidosis, and idiopathic inflammatory bowel disease.

Processing of Thermotropic Liquid Crystalline Polymers and Their Blends

DTIC Science & Technology

1990-02-23

Dziemianowicz, J. Romanski and W. Werber , Polym. Eng. Sci., 28(12), 785 (1988). 22. C. U. Ko and G. L. Wilkes, J. Appi. Polym. Sci., 37, 3063 (1989). 23. K...Virginia 22217-5000 NSTL, Mississippi 39529 Dr. Bernard Dauda 1 Naval Weapons Center Naval Weapons Support Center Attn: Dr. Ron Atkins Code UKC Chemistry

Evaluation of hybrid polymers for high-precision manufacturing of 3D optical interconnects by two-photon absorption lithography

NASA Astrophysics Data System (ADS)

Schleunitz, A.; Klein, J. J.; Krupp, A.; Stender, B.; Houbertz, R.; Gruetzner, G.

2017-02-01

The fabrication of optical interconnects has been widely investigated for the generation of optical circuit boards. Twophoton absorption (TPA) lithography (or high-precision 3D printing) as an innovative production method for direct manufacture of individual 3D photonic structures gains more and more attention when optical polymers are employed. In this regard, we have evaluated novel ORMOCER-based hybrid polymers tailored for the manufacture of optical waveguides by means of high-precision 3D printing. In order to facilitate future industrial implementation, the processability was evaluated and the optical performance of embedded waveguides was assessed. The results illustrate that hybrid polymers are not only viable consumables for industrial manufacture of polymeric micro-optics using generic processes such as UV molding. They also are potential candidates to fabricate optical waveguide systems down to the chip level where TPA-based emerging manufacturing techniques are engaged. Hence, it is shown that hybrid polymers continue to meet the increasing expectations of dynamically growing markets of micro-optics and optical interconnects due to the flexibility of the employed polymer material concept.

Direct formation of nano-pillar arrays by phase separation of polymer blend for the enhanced out-coupling of organic light emitting diodes with low pixel blurring.

PubMed

Lee, Cholho; Han, Kyung-Hoon; Kim, Kwon-Hyeon; Kim, Jang-Joo

2016-03-21

We have demonstrated a simple and efficient method to fabricate OLEDs with enhanced out-coupling efficiencies and with low pixel blurring by inserting nano-pillar arrays prepared through the lateral phase separation of two immiscible polymers in a blend film. By selecting a proper solvent for the polymer and controlling the composition of the polymer blend, the nano-pillar arrays were formed directly after spin-coating of the polymer blend and selective removal of one phase, needing no complicated processes such as nano-imprint lithography. Pattern size and distribution were easily controlled by changing the composition and thickness of the polymer blend film. Phosphorescent OLEDs using the internal light extraction layer containing the nano-pillar arrays showed a 30% enhancement of the power efficiency, no spectral variation with the viewing angle, and only a small increment in pixel blurring. With these advantages, this newly developed method can be adopted for the commercial fabrication process of OLEDs for lighting and display applications.