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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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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

Process for controlling morphology and improving thermal-mechanical performance of high performance interpenetrating and semi-interpenetrating polymer networks

In the process of the present invention, a non-polar, aprotic solvent is removed from an oligomer/polymer solution by freeze-drying in order to produce IPNs and semi-IPNs. By thermally quenching the solution to a solid in a short length of time, the size of the minor constituent-rich regions is greatly reduced as they are excluded along with the major constituent from the regions of crystallizing solvent. The use of this process sequence of controlling phase morphology provides IPNs and semi-IPNs with improved fracture toughness, microcracking resistance, and other physical-mechanical properties as compared to IPNs and semi-IPNs formed when the solvent is evaporated rather than sublimed.

Pater, Ruth H.↗
NASA NTRS1987

Semi-2-interpenetrating networks of high temperature systems

A semi-2-interpenetrating network of improved qualities which is prepared by combining a linear polymer and a cross-linkable oligomer having identical repeating units is developed. Polymers have been combined in the past into interpenetrating networks in order to gain useful properties from the combination of materials. However, previous semi-interpenetrating networks have only been formed using polymers having different repeating units. This method provides a semi-2-interpenetrating network of improved strength, adhesion, and processability.

Egli, Annmarie O.↗
NASA NTRS1989

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.↗
NASA NTRS1978

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

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

Rembaum, A.↗
NASA NTRS1981

Momentum and energy exchange collision terms for interpenetrating bi-Maxwellian gases

For application to aeronomy and space physics problems involving strongly magnetized plasma flows, we derived momentum and energy exchange collision terms for interpenetrating bi-Maxwellian gases. Collision terms were derived for Coulomb, Maxwell molecule, and constant collision cross-section interaction potentials. The collision terms are valid for arbitrary flow velocity differences and temperature differences between the interacting gases as well as for arbitrary temperature anisotropies. The collision terms had to be evaluated numerically and the appropriate coefficients are presented in tables. However, the collision terms were also fitted with simplified expressions, the accuracy of which depends on both the interaction potential and the temperature anisotropy. In addition, we derived the closed set of transport equations that are associated with the momentum and energy collision terms.

Barakat, A. R.↗
NASA NTRS1985

Semi-2-interpenetrating polymer networks of high temperature systems

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.

Hanky, A. O.↗
NASA NTRS1987

Semi-Interpenetrating Polymer Networks

Desirable qualities achieved by "networking" aromatic and addition polyimides. Novel semi-interpenetrating network (semi-ipn) prepared from two types of polyimides. Semi-ipn results when linear polymer synthesized in presence of cross-linked polymer or vice-versa. Semi-ipn attains certain properties better than those of either polymer alone.

St. Clair, T. L.↗
NASA NTRS1986

Semi-interpenetrating networks of LARC-TPI

In a previous research project at NASA-Langley, a novel semi-2-interpenetrating polymer network (semi-2-IPN) was prepared from the linear, thermoplastic polyimidesulfone, and the more brittle, crosslinked, acetylene-terminated imidesulfone. Synergistic qualities such as improved thermooxidative stability and better processability were achieved from this combination. The novelty of the system lay in the fact that the structures of the linear and crosslinking components were nearly identical. This similarity in structure eliminates any phase separation problems common to many-IPNs. In a similar way, a semi-2-IPN was prepared from linear, thermoplastic LARC-TPI and acetylene-terminated LARC-TPI (ATLARC-TPI). The preparation and characterization of this system will be discussed as well as adhesive and composite data.

Egli, Annemarie H.↗
NASA NTRS1988

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

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

Pater, Ruth H.↗
NASA NTRS1988

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

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

Hansen, Marion Glenn↗
NASA NTRS1989

Interpenetrating polymer networks from acetylene terminated materials

As part of a program to develop high temperature/high performance structural resins for aerospace applications, the chemistry and properties of a novel class of interpenetrating polymer networks (IPNs) were investigated. These IPNs consist of a simple diacetylenic compound (aspartimide) blended with an acetylene terminated arylene ether oligomer. Various compositional blends were prepared and thermally cured to evaluate the effect of crosslink density on resin properties. The cured IPNs exhibited glass transition temperatures ranging from 197 to 254 C depending upon the composition and cure temperature. The solvent resistance, fracture toughness and coefficient of thermal expansion of the cured blends were related to the crosslink density. Isothermal aging of neat resin moldings, adhesive and composite specimens showed a postcure effect which resulted in improved elevated temperature properties. The chemistry, physical and mechanical properties of these materials will be discussed.

Connell, J. W.↗
NASA NTRS1990

Plastic deformation mechanisms in polyimide resins and their semi-interpenetrating networks

High-performance thermoset resins and composites are critical to the future growth of space, aircraft, and defense industries in the USA. However, the processing-structure-property relationships in these materials remain poorly understood. In the present ASEE/NASA Summer Research Program, the plastic deformation modes and toughening mechanisms in single-phase and multiphase thermoset resins were investigated. Both thermoplastic and thermoset polyimide resins and their interpenetrating networks (IPNs and semi-IPNs) were included. The fundamental tendency to undergo strain localization (crazing and shear banding) as opposed to a more diffuse (or homogeneous) deformation in these polymers were evaluated. Other possible toughening mechanisms in multiphase thermoset resins were also examined. The topological features of network chain configuration/conformation and the multiplicity of phase morphology in INPs and semi-IPNs provide unprecedented opportunities for studying the toughening mechanisms in multiphase thermoset polymers and their fiber composites.

Jang, Bor Z.↗
NASA NTRS1992

High-Performance, Semi-Interpenetrating Polymer Network

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.

Pater, Ruth H.↗
NASA NTRS1991

Toughening of PMR composites by semi-interpenetrating networks

Polymerization of monomer reactants (PMR-15) type polyimide and RP46 prepregs were drum wound using IM-7 fibers. Prepregging and processing conditions were optimized to yield good quality laminates with fiber volume fractions of 60 percent (+/- 2 percent). Samples were fabricated and tested to determine comprehensive engineering properties of both systems. These included 0 deg flexure, short beam shear, transverse flexure and tension, 0 deg tension and compression, intralaminar shear, short block compression, mode 1 and 2 fracture toughness, and compression after impact properties. Semi-2-IPN (interpenetrating polymer networks) toughened PMR-15 and RP46 laminates were also fabricated and tested for the same properties.

Tiwari, S. N.↗
NASA NTRS1992

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

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

Pater, Ruth H.↗
NASA NTRS1990

Improving processing and toughness of a high performance composite matrix through an interpenetrating polymer network. VI

A simultaneous semi-interpenetrating polymer network (semi-IPN) concept is presented which combines easy-to-process, but brittle, thermosetting polyimides with tough, but difficult to process, linear thermoplastic polyimides. The combination results in a semi-IPN with the easy processability of a thermoset and good toughness of a thermoplastic. Four simultaneous semi-IPN systems were developed from commercially available NR-150B2 combined with each of the four Thermid materials (LR-600, AL-600, MC-600, and FA-700). It is concluded that there is a significant improvement in resin fracture toughness of Thermid-polyimide-based semi-IPN systems and some improvement in composite microcracking resistance compared to Thermid LR-600. Excellent composite mechanical properties have been achieved. These new semi-IPN materials have the potential to be used as composite matrices, adhesives, and molding materials.

Pater, Ruth H.↗
NASA NTRS1994

Tough, processable semi-interpenetrating polymer networks from monomer reactants

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.

Pater, Ruth H.↗
NASA NTRS1994

Tough, processable simultaneous semi-interpenetrating polyimides

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 a thermosetting polyimide with a thermoplastic monomer precursor solution (NR150B2) and allowing them to react 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 endcapped polyimides which were previously inherently brittle and difficult to process.

Pater, Ruth H.↗