Ballistic Performance of Polyimide Aerogels
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Sadeq Malakooti↗
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Results for “polyimide”
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.
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Spray-deposition of graphene/polymer thin coatings on polyimide sheets for lunar dust adhesion mitigation
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Keith L. Gordon↗
Data-Driven Degradation Study of Interfacial Adhesion Under Accelerated Aging: Adhesively Bonded Cu and Polyimide in Flexible Printed Circuit Boards (PCBs)
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Chemistry - Inorganic, organic, physical and analy↗
Advanced Polymers Containing the Phenyltrifluoroethylidene Connecting Group
A new, lower cost fluorinated dianhydride based on the phenyltrifluoroethylidene (3F) connecting linkage was invented by the principal author in the early 1980's. New 3F condensation and addition cured polyimides were synthesized with the newly discovered 3F dianhydride and the previously known 3F diamine. As controls, polyimides based on the somewhat analogous higher cost hexafluoroisopropylidene (6F) linkage were also prepared. The short term thermal oxidative stability (TOS), determined by thermal gravimetric analysis (TGA), and the glass transition temperatures (Tg) of 3F dianhydride polyimides were found to be similar to 6F dianhydride polyimides, but the Tg was slightly higher for 3F diamine polyimides than 6F diamine polyimides. Unfortunately, in real time testing, long term TOS of 3F polymers was clearly inferior to 6F polymers. This was due to a 3 to 5 fold greater rate of loss of trifluoromethyl group from 3F versus 6F linkages. However, at shorter times or lower temperatures, 3F TOS was almost comparable to 6F TOS. The wide scope of the 3F technology was also demonstrated to have distinct unique advantages over 6F technology through the use of the 3F pendant phenyl ring as a synthetic site to introduce other functional groups. These groups have been used for the control or modification of polymer properties; an advantage lacking within 6F technology. The synthetic ease by which 3F can be introduced into various types of monomers has lead to the explosion of advanced 3F polyimides and other high performance advanced 3F polymers in the prior decade of 3F polymer literature as cited herein; covering polyimides, substituted polyimides, at least ten types of nonpolyimide 3F polymer modifications, and also the government's nine 3F U.S. patents and corporations' nine 3F U.S. patents.
Alstron, William B.↗
High-Flow PMR-Polymide Composites Developed With Mechanical Properties Comparable to Other High-Temperature Systems
PMR polyimides, in particular PMR-15, are well known for their excellent high-temperature stability and performance, and solvent resistance. However, the processing of these materials is limited, for the most part, to prepreg-based methods, such as compression or autoclave processing. These methods involve substantial amounts of hand labor, and as a result, manufacturing costs for components made from PMR polyimides can be high. In cost-sensitive applications, these high manufacturing costs can make the use of PMR polyimide-based components cost prohibitive. Lower cost manufacturing methods, such as resin transfer molding (RTM) and resin film infusion, have been demonstrated to reduce manufacturing costs by as much as 50 percent over prepreg-based methods. However, these processes are only amenable to materials with melt viscosities below 30 poise. Most PMR polyimides have melt viscosities on the order of 100 poise or higher. Recent efforts at the NASA Glenn Research Center have focused on chemical modifications to PMR polyimides to reduce their melt viscosity to the point where they could be processed by these low-cost manufacturing methods without adversely affecting their high-temperature properties and performance. These efforts have led to a new family of PMR polyimides that have melt viscosities significantly lower than that of PMR-15. Reductions in melt viscosity are brought about through the introduction of molecular twists in the polymer backbone. Carbon fiber (T650- 35) composites were prepared from one of these polyimides, designated PMR-Flex, by compression molding. The properties of these composites are presented below and compared with comparable composites made from PMR-15 and PETI-RTM, a new low-melt-viscosity polyimide.
Meador, Michael A.↗
Helping Aircraft Engines Lighten Up
High-temperature polyimide/carbon fiber matrix composites are developed by the Polymers Branch at NASA's Glenn Research Center. These materials can withstand high temperatures and have good processing properties, which make them particularly useful for jet and rocket engines and for components such as fan blades, bushings, and duct segments. Applying polyimide composites as components for aerospace structures can lead to substantial vehicle weight reductions. A typical polyimide composite is made up of layers of carbon or glass fibers glued together by a high-temperature polymer to make the material strong, stiff, and lightweight. Organic molecules containing carbon, nitrogen, oxygen, and hydrogen within the polyimide keep the material s density low, resulting in the light weight. The strength of a component or part made from a polyimide comes mainly from the reinforcing high-strength fibers. The strength of the carbon fibers coupled with the stiffness of polyimides allows engineers to make a very rigid structure without it being massive. Another benefit of a polyimide s suitability for aerospace applications is its reduced need for machining. When polyimide parts are removed from a mold, they are nearly in their final shape. Usually, very little machining is needed before a part is ready for use.
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A review of processable high temperature resistant addition-type laminating resins
An important finding that resulted from research that was conducted to develop improved ablative resins was the discovery of a novel approach to synthesize processable high temperature resistant polymers. Low molecular weight polyimide prepolymers end-capped with norbornene groups were polymerized into thermo-oxidatively stable modified polyimides without the evolution of void producing volatile materials. This paper reviews basic studies that were performed using model compounds to elucidate the polymerization mechanism of the so-called addition-type polyimides. The fabrication and properties of polyimide/graphite fiber composites using A-type polyimide prepolymer as the matrix are described. An alternate method for preparing processable A-type polyimides by means of in situ polymerization of monomeric reactants on the fiber reinforcement is also described. Polyimide/graphite fiber composite performance at elevated temperatures is presented for A-type polyimides.
Serafini, T. T.↗
New High Temperature Cross Linking Monomers
This report describes the results of a one-year program designed to synthesize new, nonvolatile crosslinking monomers and to prove their feasibility in the development of lower temperature curing PMR-polyimide resins with high temperature capability. The objective of this program is to develop PMR-polyimide resins capable of being processed at a maximum temperature of 232C to 288C (450F to 500F) without sacrifice of the high temperature 316C (600F) capability of the state-of-the-art PMR-15 polyimide resin. Four monomethyl esters were synthesized and characterized for use in the crosslinking studies. It was found that all four crosslinkers were capable of entering into a crosslinking reaction to produce polymer specimens which were strong, dense and free of voids. The infrared and DSC studies of each crosslinker with monomers 4,4'-methylenedianiline (MDA) and the dimethyl ester of 3,3',4,4'-benzophenonetetracarboxylic acid (BTDE) comprising the resin systems, crosslinker/MDA/BTDE suggested that curing could be accomplished at 288C (550F). However, fabrication of dense, void free polymer specimens required a temperature of 316C (600F) and a pressure of 0.69 MPa (100 psi). The crosslinkers, monomethyl ester of 2,5-bicyclo[2.2.1]heptadiene-2,3-dicarboxylic acid (NDE) and monomethyl ester of maleic acid (MAE) were selected for evaluation in Celion 6000/PMR polyimide composites. These composites were characterized at RT, 288C (550F) and 316C (600F) initially and after isothermal aging at 288C (550F) and 316C (600F) for several hundred hours. The results of the isothermal aging studies suggested that both PMR systems NDE-MDA-BTDE and MAE-MDA-BTDE are promising candidates as matrices for addition type polyimide composites. These studies demonstrated that alternate crosslinkers to NE/MDA/BTDE are feasible, but mechanisms to lower the crosslinking temperature must be developed to provide lower temperature processing PMR-type polyimides.
Scola, Daniel A.↗
Flexible Microstrip Circuits for Superconducting Electronics
Flexible circuits with superconducting wiring atop polyimide thin films are being studied to connect large numbers of wires between stages in cryogenic apparatus with low heat load. The feasibility of a full microstrip process, consisting of two layers of superconducting material separated by a thin dielectric layer on 5 mil (approximately 0.13 mm) Kapton sheets, where manageable residual stress remains in the polyimide film after processing, has been demonstrated. The goal is a 2-mil (approximately 0.051-mm) process using spin-on polyimide to take advantage of the smoother polyimide surface for achieving highquality metal films. Integration of microstrip wiring with this polyimide film may require high-temperature bakes to relax the stress in the polyimide film between metallization steps.
Chervenak, James↗
High Temperature Resin Matrix Composites for Aerospace Structures
Accomplishments and the outlook for graphite-polyimide composite structures are briefly outlined. Laminates, skin-stiffened and honeycomb sandwich panels, chopped fiber moldings, and structural components were fabricated with Celion/LARC-160 and Celion/PMR-15 composite materials. Interlaminar shear and flexure strength data obtained on as-fabricated specimens and specimens that were exposed for 125 hours at 589 K indicate that epoxy sized and polyimide sized Celion graphite fibers exhibit essentially the same behavior in a PMR-15 matrix composite. Analyses and tests of graphite-polyimide compression and shear panels indicate that utilization in moderately loaded applications offers the potential for achieving a 30 to 50 percent reduction in structural mass compared to conventional aluminum panels. Data on effects of moisture, temperature, thermal cycling, and shuttle fluids on mechanical properties indicate that both LARC-160 and PMR-15 are suitable matrix materials for a graphite-polyimide aft body flap. No technical road blocks to building a graphite-polyimide composite aft body flap are identified.
Davis, J. G., Jr.↗
High-temperature resins
The basic chemistry, cure processes, properties, and applications of high temperature resins known as polyimides are surveyed. Condensation aromatic polymides are prepared by reacting aromatic diamines with aromatic dianhydrides, aromatic tetracarboxylic acids, or with dialkyl esters of aromatic tetracarboxylic acids, depending on the intended end use. The first is for coatings or films while the latter two are more suitable for polyimide matrix resins. Prepreg solutions are made by dissolving reactants in an aprotic solvent, and advances in the addition of a diamine on the double bond and radical polymerization of the double bond are noted to have yielded a final cure product with void-free characteristics. Attention is given to properties of the Skybond, Pyralin, and NR-150B polyimide prepreg materials and characteristics of aging in the NP-150 polyimides. Finally, features of the NASA-developed PMR polyimides are reviewed.
Serafini, T. T.↗
Development of an impact- and solvent-resistant thermoplastic composite matrix
Synthesis, moldability and chloroform, acetone and tricresyl phosphate resistance of 16 polymer compositions are described. These aliphatic heterocyclic polymers include polyimides, polybenzimidazoles, and N-arylenepolybenzimidazoles. A solution condensation (cresol) method to prepare imidized aliphaic polyimides is described. Two polyimides and one polybenzimidazole demonstrate no crazing or cracking during 500 hr exposure to the cited solvents under stress. Modification of one aliphatic polyimide with several aromatic amines suggests that m-phenylenediamine is singular in its behavior to improve the chloroform resistance of that class of polyimides.
Delano, C. B.↗
A tough performance simultaneous semi-interpenetrating polymer network
A semi-interpenetrating polyimide (semi-IPN) network and methods for making and using the same are disclosed. The semi-IPN system comprises a high performance thermosetting polyimide having an acetylene-terminated group acting as a crosslinking site and a high performance linear thermoplastic polyimide. The polymer is made by combining low viscosity precursors and low molecular weight polymers of the thermosetting and thermoplastic polyimides and allowing them to react in the immediate presence of each other to form a simultaneous semi-interpenetrating polyimide network. Provided is a high temperature system having significantly improved processability and damage tolerance while maintaining excellent thermo-oxidative stability, mechanical properties and resistance to humidity, when compared with the commercial high temperature resin, Thermid 600. This material is particularly adapted for use as a molding, adhesive and advanced composite matrix for aerospace structural and electronic applications.
Pater, Ruth H.↗
Microstructural Characterization of Semi-Interpenetrating Polymer Networks by Positron Lifetime Spectroscopy
Thermoset and thermoplastic polyimides have complementary physical and mechanical properties. Whereas thermoset polyimides are brittle and generally easier to process, thermoplastic polyimides are tough but harder to process. A combination of these two types of polyimides may help produce polymers more suitable for aerospace applications. Semi-Interpenetrating Polymer Networks (S-IPN) of thermoset LaRC(TM)-RP46 and thermoplastic LaRC(TM)-IA polyimides were prepared in weight percent ratios ranging from 100:0 to 0:100. Positron lifetime measurements were made in these samples to correlate their free volume features with physical and mechanical properties. As expected, positronium atoms are not formed in these samples. The second lifetime component has been used to infer the positron trap dimensions. The 'free volume' goes through a minimum at a ratio of about 50:50, and this suggests that S-IPN samples are not merely solid solutions of the two polymers. These data and related structural properties of the S-IPN samples are discussed.
Singh, Jag J.↗
Nuclear Instruments and Methods in Physics Research: Microstructural Characterization of Semi-Interpenetrating Polymer Networks by Positron Lifetime Spectroscopy - Section B
Thermoset and thermoplastic polyimides have complementary physical/mechanical properties. Whereas thermoset polyimides are brittle and generally easier to process, thermoplastic polyimides are tough but harder to process. It is expected that a combination of these two types of polyimides may help produce polymers more suitable for aerospace applications. Semi-Interpenetrating Polymer Networks (S-IPNs) of thermoset LaRC(Trademark)-RP46 and thermoplastic LARC(Trademark)-IA polyimides were prepared in weight percent ratios ranging from 100:0 to 0: 100. Positron lifetime measurements were made in these samples to correlate their free volume features with physical/mechanical properties. As expected, positronium atoms are not formed in these samples. The second life time component has been used to infer the positron trap dimensions. The "free volume" goes through a minimum at about 50:50 ratio, suggesting that S-IPN samples are not merely solid solutions of the two polymers. These data and related structural properties of the S-IPN samples have been discussed in this paper.
Singh, Jag J.↗
Composition and Process for Retarding the Premature Aging of PMR Monomer Solutions and PMR Prepegs
Polyimides are derived from solutions of at least one low-boiling organic solvent, e.g. isopropanol containing a mixture of polyimide-forming monomers. The monomeric solutions have an extended shelf life at ambient (room) temperatures as high as 80 C, and consist essentially of a mixture of monoalkyl ester-acids, alkyl diester-diacids and aromatic polyamines wherein the alkyl radicals of the esteracids are derived from lower molecular weight aliphatic secondary alcohols having 3 to 5 carbon atoms per molecule such as isopropanol, secondary butanol, 2-methyl-3-butanol, 2 pentanol or 3-pentanol. The solutions of the polyimide-forming monomers have a substantially improved shelf-life and are particularly useful in the aerospace and aeronautical industry for the preparation of polyimide reinforced fiber composites such as the polyimide cured carbon composites used in jet engines, missiles, and for other high temperature applications.
Alston, William B.↗
Surface Evaluation by XPS of High Performance Foams After Exposure to Oxygen Plasma
This report will present the results of a study done during a 10-week summer faculty fellowship during the summer of 2001 working with Ms. Martha Williams of the Testbeds Group at Kennedy Space Center. The work was in a new area for this faculty and was both interesting and enjoyable. An imide is a compound in which nitrogen is bonded directly to an R group and to two other R groups through carbonyls. Polyimides have a number of properties that make them highly desirable materials for use on structures that are exposed to extreme conditions. They are strong, fire resistant, minimally outgasing, stable over a large temperature range, resistant to chemical attack, transparent to infrared and microwaves, and have a low density. One polyimide, solimide, commercially available as a foam, retains resiliency from -300 F to +500 F, is highly flame retardant, and decomposes with virtually no smoke or toxic byproduct formation. The density of this product is such that its use in place of fiberglass in the lower lobe of a 747 saves 400 lb. Shipboard applications have resulted in literally tons of weight reduction. While polyimide films have been used in structures to be placed in low earth orbit (LEO) for many years, polyimide foams have found only minimal application in this realm. NASA Langley Research Center has developed new technology that allows for the processing of new polyimide foams. The resulting increased availability of these materials, along with their highly desirable properties, has prompted a study to determine the suitability of these materials for use in structures to be placed in LEO.
Hampton, Michael D.↗
Thin Film...Large Payoff
SRS Technologies is currently the only company licensed by Langley Research Center to produce colorless polyimides. They currently produce two polyimides, the LaRC-CP1 and LaRC-CP2 developed by Langley Research Center. These polyimides offer many advantages over other commercially available materials including excellent thermal stability, radiation resistance, solubility, and transparency. The SRS polyimides can be used in laminates, films, molded parts, and stock shapes. The polyimide technology has also helped the company further their development of solar arrays.
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