Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “polymer additive”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS2020

Novel High Barrier Films for Packaging Food and Medicine

Long manned missions require food packaging to maintain food safety, nutrition, and acceptability for the length of 3-5 years1,2 while the shelf life assigned by NASA for current provisions is 18-24 months1. The focus of this design project was to make a polymer film specifically to function as a high oxygen barrier to later be included in an improved multi-layer packaging system of other specialized polymers with capabilities to allow for a 5-year shelf-life. To qualify as a high oxygen barrier film and to be a successful design for the future packaging, the resulting film is required to have an oxygen transmission rate (OTR) less than 0.06 cc/ m2/24 hr/atm, the standard for the current packaging3. This new film was designed to have a decreased permeability by increasing the “tortuous path” a gas molecule travels to permeate through a film. The increase in the “tortuous path” of a gas molecule is accomplished by introducing a 2D material additive. The additive chosen for this project was hexagonal boron nitride (h-BN) which exfoliates into boron nitride nanosheets (BNNs). Nylon 6 was chosen as the candidate for the matrix. This project is required to determine the best methods to synthesize the sample film and then to test the OTR of the film to determine if this design was successful. This project examined methods for pulverizing polymer resin pellets, h-BN exfoliation, and film fabrication using a hot press. This report includes the exfoliation and analysis of h-BN, procedural preparations for films, and a modeling study of estimated OTR of the h-BN/Nylon. The work in this report did not yield a high barrier composite film because of the laboratory closure in response to COVID -19 guidance but provides a concise method of the additive preparation and film synthesis. This gives a good starting point for future research in high barrier films by 2D additive composites.

Polymer, Nylon, PET, boron nitride, nanocomposite↗
NASA NTRS2024

Effects of Specimen Geometry on Flatwise Tensile Strength

The through-thickness or flatwise strength of a uniaxial polymer matrix composite was investigated with several test specimen geometries and starting plate thicknesses. The use of thinner plates is desirable to save material and lower costs during materials development programs. The various configurations gave similar results with the exception of thin, straight-sided specimens. Thin specimens tended to provide invalid results per ASTM International D7291; however, the addition of a large, shallow radius improved the results. The Weibull distribution provided a good fit to the combined data.

Polymer matrix composite↗
NASA NTRS1987

Polyether-polyester graft copolymer

Described is a polyether graft polymer having improved solvent resistance and crystalline thermally reversible crosslinks. The copolymer is prepared by a novel process of anionic copolymerization. These polymers exhibit good solvent resistance and are well suited for aircraft parts. Previous aromatic polyethers, also known as polyphenylene oxides, have certain deficiencies which detract from their usefulness. These commercial polymers are often soluble in common solvents including the halocarbon and aromatic hydrocarbon types of paint thinners and removers. This limitation prevents the use of these polyethers in structural articles requiring frequent painting. In addition, the most popular commercially available polyether is a very high melting plastic. This makes it considerably more difficult to fabricate finished parts from this material. These problems are solved by providing an aromatic polyether graft copolymer with improved solvent resistance and crystalline thermally reversible crosslinks. The graft copolymer is formed by converting the carboxyl groups of a carboxylated polyphenylene oxide polymer to ionic carbonyl groups in a suitable solvent, reacting pivalolactone with the dissolved polymer, and adding acid to the solution to produce the graft copolymer.

Bell, Vernon L.↗
NASA NTRS1978

Study of dynamic emission spectra from lubricant films in an elastohydrodynamic contact using Fourier transform spectroscopy

Infrared emission spectra were obtained through a diamond window from lubricating fluids in an operating sliding elastohydrodynamic contact and analyzed by comparison with static absorption spectra under similar pressures. Different loads, shear rates and temperatures were used. Most of the spectra exhibited polarization characteristics, indicating directional alignment of the lubricant in the EHD contact. Among the fluids studied were a "traction" fluid, an advanced ester, and their mixtures, a synthetic paraffin, a naphthenic reference fluid (N-1), both neat and containing 1 percent of p-tricresyl phosphate as an anti-wear additive, and a C-ether. Traction properties were found to be nearly proportional to mixture composition for traction fluid and ester mixtures. The anti-wear additive reduced traction and fluid temperature under low loads but increased them under higher loads, giving rise to formation of a friction polymer.

Lauer, J. L.↗
NASA NTRS1991

LDEF fiber optic exposure experiment

Ten fiber optic cable samples of different types were exposed in low Earth orbit for over 5.5 years on the Long Duration Exposure Facility (LDEF). Four of the samples were mounted externally, and the remaining six were internal, under approximately .5 gc/sq m of aluminum. The experiment was recovered in January of 1990, and laboratory evaluation of the effects of the exposure has continued since. An increase in loss, presumed to be from radiation darkening, aging effects on polymer materials used in cabling, unique contamination effects on connector terminations, and micrometeoroid impacts were observed on some of the samples. In addition, the dependence of sample loss was measured as a function of temperature before and after the flight. All cable samples were functional, and the best exhibited no measurable change in performance, indicating that conventional fiber optic cables can perform satisfactorily in spacecraft. Experimental results obtained to date will be presented and discussed.

Johnston, Alan R.↗
NASA NTRS1992

Effects of a noncoplanar biphenyldiamine on the processing and properties of addition polyimides

Addition curing polyimides, prepared from noncoplanar 2,2'-bis(trifluoromethyl) 4,4' diaminobiphenyl (BTDB) with various dianhydrides were evaluated as high temperature polymer matrix materials. T sub g of these polymers were measured by mechanical methods as well as by thermal mechanical analysis. Physical and mechanical properties as well as the thermo-oxidative stability of neat resins and the corresponding G40-600 graphite fiber reinforced composites were compared to that of PMR-II-50 and V-CAP-75.

Chuang, Kathy C.↗
NASA NTRS1996

Low Crossover Polymer Electrolyte Membranes for Direct Methanol Fuel Cells

Direct Methanol Fuel Cells (DMFC's) using polymer electrolyte membranes are promising power sources for portable and vehicular applications. State of the art technology using Nafion(R) 117 membranes (Dupont) are limited by high methanol permeability and cost, resulting in reduced fuel cell efficiencies and impractical commercialization. Therefore, much research in the fuel cell field is focused on the preparation and testing of low crossover and cost efficient polymer electrolyte membranes. The University of Southern California in cooperation with the Jet Propulsion Laboratory is focused on development of such materials. Interpenetrating polymer networks are an effective method used to blend polymer systems without forming chemical links. They provide the ability to modify physical and chemical properties of polymers by optimizing blend compositions. We have developed a novel interpenetrating polymer network based on poly (vinyl - difluoride)/cross-linked polystyrenesulfonic acid polymer composites (PVDF PSSA). Sulfonation of polystyrene accounts for protonic conductivity while the non-polar, PVDF backbone provides structural integrity in addition to methanol rejection. Precursor materials were prepared and analyzed to characterize membrane crystallinity, stability and degree of interpenetration. USC JPL PVDF-PSSA membranes were also characterized to determine methanol permeability, protonic conductivity and sulfur distribution. Membranes were fabricated into membrane electrode assemblies (MEA) and tested for single cell performance. Tests include cell performance over a wide range of temperatures (20 C - 90 C) and cathode conditions (ambient Air/O2). Methanol crossover values are measured in situ using an in-line CO2 analyzer.

Prakash, G. K. Surya↗
NASA NTRS1999

Sulfuric acid on Europa and the radiolytic sulfur cycle

A comparison of laboratory spectra with Galileo data indicates that hydrated sulfuric acid is present and is a major component of Europa's surface. In addition, this moon's visually dark surface material, which spatially correlates with the sulfuric acid concentration, is identified as radiolytically altered sulfur polymers. Radiolysis of the surface by magnetospheric plasma bombardment continuously cycles sulfur between three forms: sulfuric acid, sulfur dioxide, and sulfur polymers, with sulfuric acid being about 50 times as abundant as the other forms. Enhanced sulfuric acid concentrations are found in Europa's geologically young terrains, suggesting that low-temperature, liquid sulfuric acid may influence geological processes.

unmanned↗
NASA NTRS1998

Oceanic protection of prebiotic organic compounds from UV radiation

It is frequently stated that UV light would cause massive destruction of prebiotic organic compounds because of the absence of an ozone layer. The elevated UV flux of the early sun compounds this problem. This applies to organic compounds of both terrestrial and extraterrestrial origin. Attempts to deal with this problem generally involve atmospheric absorbers. We show here that prebiotic organic polymers as well as several inorganic compounds are sufficient to protect oceanic organic molecules from UV degradation. This aqueous protection is in addition to any atmospheric UV absorbers and should be a ubiquitous planetary phenomenon serving to increase the size of planetary habitable zones.

Non-NASA Center↗
NASA NTRS2012

A "Warm Formamide" Scenario for the Origins of Life Might not be so Hot: Comment on "Formamide and the Origin of Life"

In this review, Saladino et al. present an intriguing hypothesis surrounding the role of formamide in the origins of life on Earth, backed by experimental results supporting each step from formamide to RNA polymers. The overall premise is that, from formamide and inorganic phosphate, RNA molecules over 100 nucleotides in length can be produced. In addition, many carboxylic acids likely relevant to prebiotic metabolism, are formed along the way. Thus, from a rather simple organic molecule that has been observed in outer space (formamide), you can generate many of the compounds necessary for the origins of life. However, because high temperatures (160 C) are required for the formamide reactions, it remains unclear where the "warm formamide" scenario could have occurred. Low-temperature, aqueous hydrogen cyanide-based prebiotic chemistry that we know actually happened has been shown to produce many of the molecules invoked in the formamide hypothesis: amino acids, carboxylic acids, sugar acids, and nucleobases have all been found in meteorites recovered on Earth, providing a plausible route for their synthesis and delivery. In contrast, a large portion of the formamide hypothesis is based on relatively hightemperature reactions, A plausible milieu for high-temperature reactions with concentrated formamide is yet to be described, and is critical for this hypothesis to be validated. Hydrothermal vents are attractive heat sources, and the higher boiling point of formamide has been invoked as a mechanism to concentrate it from an aqueous solution, Unless the water can actually evaporate, however, there would be no net enrichment. For example, in the context of a deep-sea vent, any water "removed" by heating would be quickly replaced. Some of the individual reactions underpinning the present hypothesis have been met with skepticism because they go against conventional wisdom, To name a few of the surprising results: the observation that nucleosides can be converted to cyclic phosphates when heated in the presence of minerals and inorganie phosphate; that 3'-5' cGMP and cAMP nucleotides polymerize rapidly into RNA oligomers, even in the absence of monovalent counterions and that end-to-end ligation reactions between RNA oligomers occur in essentially pure water, without requiring any activating groups or counterions. Because the polymerization reactions are simply transesterification reactions, that they readily occur in the absence of cations makes one wonder why nearly all ribozyme-catalyzed transesterification reactions are metal-ion dependent; similarly, that the end-to-end ligation reactions do not require activation runs counter to the observation that all protein-catalyzed ligation and polymerization reactions of RNA and DNA require activated substrates. Detailed mechanistic studies of the reported reactions are warranted and could provide important insights for understanding the chemistry behind the origins of life. Because the authors have produced many of the experimental results supporting their hypothesis, they could demonstrate the validity of their hypothesis by converting formamide into approx 100 nucleotide RNA oligomers, using the products of one reaction as the reactants for the next reaction, under specific conditions plausible on the pre-biotic Earth. Such a demonstration would represent a milestone for our understanding of the origins of life.

Burton, Aaron S.↗
NASA NTRS2012

A 'Warm Formamide' Scenario for the Origins of Life Might Not Be so Hot Comment on 'Formamide and the Origin of Life' by E. Di Mauro Et Al.

In this review, Saladino et al. present an intriguing hypothesis surrounding the role of formamide in the originsof life on Earth, backed by experimental results supporting each step from formamide to RNA polymers [1]. The overall premise is that, from formamide and inorganic phosphate, RNA molecules over 100 nucleotides in length canbe produced. In addition, many carboxylic acids likely relevant to prebiotic metabolism are formed along the way. Thus, from a rather simple organic molecule that has been observed in outer space (formamide), you can generatemany of the compounds necessary for the origins of life. However, because high temperatures (160 C) are requiredfor the formamide reactions, it remains unclear where the warm formamide scenario could have occurred.Low-temperature, aqueous hydrogen counter to the observation that all protein-catalyzed ligation and polymerization reactions of RNA and DNA requireactivated substrates. Detailed mechanistic studies of the reported reactions are warranted and could provide important insights for understanding the chemistry behind the origins of life.Because the authors have produced many of the experimental results supporting their hypothesis, they coulddemonstrate the validity of their hypothesis by converting formamide into 100 nucleotide RNA oligomers, usingthe products of one reaction as the reactants for the next reaction, under specific conditions plausible on the pre-bioticEarth. Such a demonstration would represent a milestone for our understanding of the origins of life.cyanide-based prebiotic chemistry that we know actually happened has beenshown to produce many of the molecules invoked in the formamide hypothesis: amino acids, carboxylic acids, sugaracids, and nucleobases have all been found in meteorites recovered on Earth [e.g. [24]], providing a plausible routefor their synthesis and delivery. In contrast, a large portion of the formamide hypothesis is based on relatively high-temperature reactions. A plausible milieu for high-temperature reactions with concentrated formamide is yet to bedescribed, and is critical for this hypothesis to be validated. Hydrothermal vents are attractive heat sources, and the higher boiling point of formamide has been invoked as a mechanism to concentrate it from an aqueous solution.Unless the water can actually evaporate, however, there would be no net enrichment. For example, in the context of a deep-sea vent, any water removed by heating would be quickly replaced.Some of the individual reactions underpinning the present hypothesis [1] have been met with skepticism becausethey go against conventional wisdom. To name a few of the surprising results: the observation that nucleosides can beconverted to cyclic phosphates when heated in the presence of minerals and inorganic phosphate [5]; that 35 cGMPand cAMP nucleotides polymerize rapidly into RNA oligomers, even in the absence of monovalent counterions [6];and that end-to-end ligation reactions between RNA oligomers occur in essentially pure water, without requiring any activating groups or counterions [7,8]. Because the polymerization reactions are simply transesterification reactions,that they readily occur in the absence of cations makes one wonder why nearly all ribozyme-catalyzed transesterification reactions are metal-ion dependent; similarly, that the end-to-end ligation reactions do not require activation runs.

life↗
NASA NTRS2026

Manufacturing Process Development of a Carbon Fiber Reinforced Polymer Composite Shaft for Electric Motors

Electric aircraft applications require electric motors with increased specific power and efficiency. Composite structural components in motors are a potential solution for reducing motor mass, reducing magnetic losses, and limiting undesired conduction paths for fault, electromagnetic interference, or common-mode currents. In this report, manufacturing trials for a high-speed carbon fiber reinforced polymer composite motor shaft are presented. Four prototype shafts were produced using a hybrid biaxial/triaxial fabric that was circumferentially wrapped onto an additively manufactured high-temperature washout mandrel. An additional traditional overbraid approach was also evaluated and shows promise for high-rate, high-performance parts using automated manufacturing. This paper discusses the shaft design, manufacturing methods explored, material selection, the manufacturing trials, and the lessons learned. The results of this manufacturing investigation show feasibility for manufacturing composite shafts for electric motors.

Electric moto shaft↗
NASA NTRS2007

Ion-Conducting Organic/Inorganic Polymers

Ion-conducting polymers that are hybrids of organic and inorganic moieties and that are suitable for forming into solid-electrolyte membranes have been invented in an effort to improve upon the polymeric materials that have been used previously for such membranes. Examples of the prior materials include perfluorosulfonic acid-based formulations, polybenzimidazoles, sulfonated polyetherketone, sulfonated naphthalenic polyimides, and polyethylene oxide (PEO)-based formulations. Relative to the prior materials, the polymers of the present invention offer greater dimensional stability, greater ease of formation into mechanically resilient films, and acceptably high ionic conductivities over wider temperature ranges. Devices in which films made of these ion-conducting organic/inorganic polymers could be used include fuel cells, lithium batteries, chemical sensors, electrochemical capacitors, electrochromic windows and display devices, and analog memory devices. The synthesis of a polymer of this type (see Figure 1) starts with a reaction between an epoxide-functionalized alkoxysilane and a diamine. The product of this reaction is polymerized by hydrolysis and condensation of the alkoxysilane group, producing a molecular network that contains both organic and inorganic (silica) links. The silica in the network contributes to the ionic conductivity and to the desired thermal and mechanical properties. Examples of other diamines that have been used in the reaction sequence of Figure 1 are shown in Figure 2. One can use any of these diamines or any combination of them in proportions chosen to impart desired properties to the finished product. Alternatively or in addition, one could similarly vary the functionality of the alkoxysilane to obtain desired properties. The variety of available alkoxysilanes and diamines thus affords flexibility to optimize the organic/inorganic polymer for a given application.

Kinder, James D.↗
NASA NTRS2007

Micromechanics of Spray-On Foam Insulation

Understanding the thermo-mechanical response of the Space Shuttle External Tank spray-on foam insulation (SOFI) material is critical, to NASA's Return to Flight effort. This closed-cell rigid polymeric foam is used to insulate the metallic Space Shuttle External Tank, which is at cryogenic temperatures immediately prior to and during lift off. The shedding of the SOFI during ascent led to the loss of the Columbia, and eliminating/minimizing foam lass from the tank has become a priority for NASA as it seeks to resume scheduled space shuttle missions. Determining the nature of the SOFI material behavior in response to both thermal and mechanical loading plays an important role as any structural modeling of the shedding phenomenon k predicated on knowledge of the constitutive behavior of the foam. In this paper, the SOFI material has been analyzed using the High-Fidelity Generalized Method of Cells (HFGMC) micromechanics model, which has recently been extended to admit a triply-periodic 3-D repeating unit cell (RUC). Additional theoretical extensions that mere made in order to enable modeling of the closed-cell-foam material include the ability to represent internal boundaries within the RUC (to simulated internal pores) and the ability to impose an internal pressure within the simulated pores. This latter extension is crucial as two sources contribute to significant internal pressure changes within the SOFI pores. First, gas trapped in the pores during the spray process will expand or contract due to temperature changes. Second, the pore pressure will increase due to outgassing of water and other species present in the foam skeleton polymer material. With HFGMC's new pore pressure modeling capabilities, a nonlinear pressure change within the simulated pore can be imposed that accounts for both of these sources, in addition to stmdar&-thermal and mechanical loading; The triply-periodic HFGMC micromechanics model described above was implemented within NASA GRC's MAC/GMC software package, giving the model access to a range of nonlinear constitutive models for the polymeric foam skeleton material. A repeating unit cell architecture was constructed that, while relatively simple, still accounts for the geometric anisotropy of the porous foam microstructure and its thin walls and thicker edges. With the lack of reliable polymeric foam skeleton materia1 properties, many simulations were executed aimed at backing out these material properties. Then, using these properties, predictions of the thermo-mechanical behavior of the foam, including calculated internal applied pressure profiles, were performed and compared with appropriate experimental data.

Bednarcyk, Brett A.↗
NASA NTRS2004

Development of a Self-calibrating Dissolved Oxygen Microsensor Array for the Monitoring and Control of Plant Growth in a Space Environment

Plant experiments in space will require active nutrient delivery concepts in which water and nutrients are replenished on a continuous basis for long-term growth. The goal of this study is to develop a novel microsensor array to provide information on the dissolved oxygen environment in the plant root zone for the optimum control of plant cultivation systems in the space environment. Control of water and oxygen is limited by the current state-of-the-art in sensor technology. Two capabilities of the new microsensor array were tested. First, a novel in situ self-diagnosis/self-calibration capability for the microsensor was explored by dynamically controlling the oxygen microenvironment in close proximity to an amperometric dissolved oxygen microsensors. A pair of integrated electrochemical actuator electrodes provided the microenvironments based on water electrolysis. Miniaturized thin film dissolved oxygen microsensors on a flexible polyimide (Kapton(Registered Trademark)? substrate were fabricated and their performances were tested. Secondly, measurements of dissolved oxygen in two representative plant growth systems were made, which had not been performed previously due to lack of proper sensing technology. The responses of the oxygen microsensor array on a flexible polymer substrate properly reflected the oxygen contents on the surface of a porous tube nutrient delivery system and within a particulate substrate system. Additionally, we demonstrated the feasibility of using a 4-point thin film microprobe for water contents measurements for both plant growth systems. mechanical flexibility, and self-diagnosis. The proposed technology is anticipated to provide a reliable sensor feedback plant growth nutrient delivery systems in both terrestrial environment and the microgravity environment during long term space missions. The unique features of the sensor include small size and volume, multiple-point sensing,

Kim, Chang-Soo↗
NASA NTRS1999

Nondestructive Evaluation Correlated with Finite Element Analysis

Advanced materials are being developed for use in high-temperature gas turbine applications. For these new materials to be fully utilized, their deformation properties, their nondestructive evaluation (NDE) quality and material durability, and their creep and fatigue fracture characteristics need to be determined by suitable experiments. The experimental findings must be analyzed, characterized, modeled and translated into constitutive equations for stress analysis and life prediction. Only when these ingredients - together with the appropriate computational tools - are available, can durability analysis be performed in the design stage, long before the component is built. One of the many structural components being evaluated by the NDE group at the NASA Lewis Research Center is the flywheel system. It is being considered as an energy storage device for advanced space vehicles. Such devices offer advantages over electrochemical batteries in situations demanding high power delivery and high energy storage per unit weight. In addition, flywheels have potentially higher efficiency and longer lifetimes with proper motor-generator and rotor design. Flywheels made of fiber-reinforced polymer composite material show great promise for energy applications because of the high energy and power densities that they can achieve along with a burst failure mode that is relatively benign in comparison to those of flywheels made of metallic materials Therefore, to help improve durability and reduce structural uncertainties, we are developing a comprehensive analytical approach to predict the reliability and life of these components under these harsh loading conditions. The combination of NDE and two- and three-dimensional finite element analyses (e.g., stress analyses and fracture mechanics) is expected to set a standardized procedure to accurately assess the applicability of using various composite materials to design a suitable rotor/flywheel assembly.

Abdul-Azid, Ali↗
NASA NTRS2009

Electrically conductive, optically transparent polymer/carbon nanotube composites and process for preparation thereof

The present invention is directed to the effective dispersion of carbon nanotubes (CNTs) into polymer matrices. The nanocomposites are prepared using polymer matrices and exhibit a unique combination of properties, most notably, high retention of optical transparency in the visible range (i.e., 400 800 nm), electrical conductivity, and high thermal stability. By appropriate selection of the matrix resin, additional properties such as vacuum ultraviolet radiation resistance, atomic oxygen resistance, high glass transition (T.sub.g) temperatures, and excellent toughness can be attained. The resulting nanocomposites can be used to fabricate or formulate a variety of articles such as coatings on a variety of substrates, films, foams, fibers, threads, adhesives and fiber coated prepreg. The properties of the nanocomposites can be adjusted by selection of the polymer matrix and CNT to fabricate articles that possess high optical transparency and antistatic behavior.

Park, Cheol↗
NASA NTRS2011

Electrically Conductive, Optically Transparent Polymer/Carbon Nanotube Composites and Process for Preparation Thereof

The present invention is directed to the effective dispersion of carbon nanotubes (CNTs) into polymer matrices. The nanocomposites are prepared using polymer matrices and exhibit a unique combination of properties, most notably, high retention of optical transparency in the visible range (i.e., 400-800 nm), electrical conductivity, and high thermal stability. By appropriate selection of the matrix resin, additional properties such as vacuum ultraviolet radiation resistance, atomic oxygen resistance, high glass transition (T.sub.g) temperatures, and excellent toughness can be attained. The resulting nanocomposites can be used to fabricate or formulate a variety of articles such as coatings on a variety of substrates, films, foams, fibers, threads, adhesives and fiber coated prepreg. The properties of the nanocomposites can be adjusted by selection of the polymer matrix and CNT to fabricate articles that possess high optical transparency and antistatic behavior.

Connell, John W.↗