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The status of high-temperature fuel tank sealants for military and potentially commercial supersonic aircraft is examined. The interrelationships of NASA's sealants program comprise synthesis and development of new fluoroether elastomers, sealant prediction studies, flight simulation and actual flight testing of best state-of-the-art fluorosilicone sealants. The technical accomplishments of these projects are reviewed.

Composites synthesized from bismaleimide have superior strength and oxidation resistance at elevated temperatures when compared with similar composites prepared with epoxy or silicon polymers of similar cost. Polyimide synthesis technique and processing method yield essentially void-free fiber-glass reinforced composites.

The preparation of chemically resistant and flame retardant foams from polyfunctional aromatic carboxylic acid derivatives and organic polyisocyanates is outlined. It was found that polyimide foams of reproducible density above 1 lb./ft. and below 6 lbs./cu ft. can be obtained by employing in the reaction of least 2% by weight of siloxane-glycol copolymer as a surfactant which acts as a specific density control agent. Polyimide foams into which reinforcing fibers such as silicon dioxide and carbon fibers may be incorporated were also produced.

It is shown that bismaleimide/woven fiberglass composites molded at moderate pressures (100 psi) yield void-free laminates of good integrity. The strength of the laminates at room temperature compares favorably with epoxy/glass laminates; at 260 C, the laminates are far superior in oxidative aging to epoxy and silicon laminates. The synthesis, processing, and fabrication of a bismaleide polymer are discussed.

Chemical reactions to produce polyimide foams for application as thermal insulation and fire prevention materials are discussed. Thermal and physical properties of the polyimides are described. Methods for improving basic formulations to produce desired qualitites are included.