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61 records · Page 4

All sources NASA NTRS DOE OSTI

NASA NTRS1973

Phenylquinoxaline copolymers

The preparation of a series of homopolymers and block and random type phenylquinoxaline copolymers is described together with their important characteristics and preliminary measurements of composite properties. Phenylquinoxaline homopolymers consisting of low, intermediate, and high molecular weight versions were prepared from the reaction of 3,3'-diaminobenzidine (DAB) and 3,3',4,4'-tetraaminobenzophenone (TAB), each with p-bis(phenylglyoxalyl)benzene as solutions (18% solids content) in a 1:1 mixture of m-cresol and xylene. Three random and three block copolymers were prepared from the reaction of various amounts of DAB and TAB with p-bis(phenylglyoxalyl)benzene. The copolymers were prepared with DAB to TAB distribution ratios of 3:1, 1:1, and 1:3. The work was performed primarily to determine if phenylquinoxaline copolymers exhibit any advantage over the homopolymers for use as functional or structural resins, especially as a matrix material in combination with a high-modulus graphite fiber reinforcement.

Hergenrother, P. M.↗

NASA NTRS2005

Mechanically Resilient Polymeric Films Doped with a Lithium Compound

This invention is a series of mechanically resilient polymeric films, comprising rod-coil block polyimide copolymers, which are doped with a lithium compound providing lithium ion conductivity, that are easy to fabricate into mechanically resilient films with acceptable ionic or protonic conductivity at a variety of temperatures. The copolymers consists of short-rigid polyimide rod segments alternating with polyether coil segments. The rods and coil segments can be linear, branched or mixtures of linear and branched segments. The highly incompatible rods and coil segments phase separate, providing nanoscale channels for ion conduction. The polyimide segments provide dimensional and mechanical stability and can be functionalized in a number of ways to provide specialized functions for a given application. These rod-coil black polyimide copolymers are particularly useful in the preparation of ion conductive membranes for use in the manufacture of fuel cells and lithium based polymer batteries.

Mary Ann B Meador↗

NASA NTRS1991

Imide/Arylene Ether Copolymers

New imide/arylene ether copolymers prepared by reacting anhydride-terminated poly(amic acids) with amine-terminated poly(arylene ethers) in polar aprotic solvents. Each resulting copolymer may have one glass-transition temperature or two, depending on chemical structure and/or compatibility of block units. Most of copolymers form tough, solvent-resistant films with high tensile properties. Films cast from solution tough and flexible, and exhibit useful thermal and mechanical properties. Potentially useful as moldings, adhesives, or composite matrices. Because of flexible arylene ether blocks, these copolymers easier to process than polyimides.

Jensen, Brian J.↗

NASA NTRS1986

Synthesis of diamino terminated poly(arylene ether sulfone) oligomers as reactive intermediates in copolymer systems

Reactive diamino terminated oligomers of pre-determined molecular weights can be prepared by either of two synthetic routes depending upon the compound used to introduce the amine functionality. After characterization by spectroscopic and thermal methods, these oligomers can be used in several post-reactions to yield novel block and segmented copolymer systems. A potential application for these poly(arylene ether sulfone) oligomers exists in the curing or co-curing of epoxy resins for improving toughness. They can also be used to prepare toughened bismaleimide systems as well as producing copolymers with improved solvent resistance, especially with respect to chlorinated solvents.

Jurek, M. J.↗

NASA NTRS1968

Polymeric Schiff bases. XVII.

Block tractable azomethine copolymers prepared by reaction of insoluble oligomers with monomers or of two different fusible oligomers, noting high thermal stability

Dalelio, G. F.↗

NASA NTRS2012

Synthesis, Characterization, Topographical Modification, and Surface Properties of Copoly(Imide Siloxane)s

Novel copoly(imide siloxane)s were synthesized from commercially available aminopropyl terminated siloxane oligomers, aromatic dianhydrides, and diamines. This synthetic approach produced copolymers with well-defined siloxane blocks linked with imide units in a random fashion. The copoly(amide acid)s were characterized by solution viscosity and subsequently used to cast thin films followed by thermal imidization in an inert atmosphere. Thin films were characterized using contact angle goniometry, attenuated total reflection Fourier transform infrared spectroscopy, confocal and optical microscopy, and tensile testing. Adhesion of micronsized particles was determined quantitatively using a sonication device. The polydimethylsiloxane (PDMS) moieties lowered the copolymer surface energy due to migration of siloxane moieties to the film s surface, resulting in a notable reduction in particle adhesion. A further reduction in particle adhesion was achieved by introducing topographical features on a scale of several to tens of microns by a laser ablation technique.

Wohl, Christopher J.↗

NASA NTRS1987

Micro and macro approaches to tough polymers for composites

The progress to date on the development of techniques to toughen continuous thermoplastic composites is summarized. The work, using the approach of toughening the polycarbonate composite matrix with rubber particles, has focused on determining the differences between Double Cantilever Beam (DCB) samples molded inhouse and those molded by NASA. Specifically, an effort was made to account for the differences in fracture toughness observed between the various specimens. In addition, preliminary results of tensile dilatometry tests are described; these tests suggest that processes leading to increased volume and enhanced shear banding are occurring within the rubber toughened system. The results of the effort using another approach, the preparation of random block copolycarbonates, are presented. The synthetic route to these species was modified so that higher molecular weights of these materials can be obtained. In addition, an attempt is being made to determine the exact block length or the number of functional groups in the oligomers since this procedure also should lead to high molecular weight materials. Dynamic mechanical analysis of the copolymer prepared so far indicates that the scale of cooperative molecular motion of the PBA polycarbonate at sub-Tg temperatures is larger than five monomer units. Efforts to find a suitable rubber-toughener for a thermoset system (bismaleimides) is also discussed. Included is a description of the various tougheners intended for use or currently being used.

Yee, Albert F.↗