Processing and properties of new high-temperature, lightweight composites based on foam polyimide binder

Yudin, V. E.; Otaigbe, J. U.; Artemieva, V. N.

Department of Materials Science and Engineering

Iowa State University of Science and Technology

Ames, IA USA

Abstract

A method for fabrication of lightwt. ( r = 0.3-1.1 kg/dm3) composites based on high-temp. foam polyimide binder, carbon fibers, and org. fibers was developed. The polyimide foam binder was prepd. by direct thermal imidization of H bond complexes of 3,3',4,4'-benzophenonetetracarboxylic dialkyl esters (R = CH3, C2H5, C3H7, C4H9) and diamines, without intermediate stage of pre-polymer (polyamic acid or polyamidoester formation). The polyimide fibers were Aramid T and Oxalon which were combined with carbon fibers to form a felt for prepregging. The d. and mech. properties of the foam composite can be varied over a relatively wide range, depending on the vol. content of fiber and air pores. The high glass transition temp. of 260 ° of the resin, coupled with the high thermal stability of carbon or polyimide fibers, contributes to the excellent retention of mech. properties at elevated temps. The temp. at the beginning of wt. loss is not lower than 570 ° and depends on the kind of fiber felt. The combination of thermal and specific mech. properties of foam composites and the exceptional thermal stability and processability on conventional molding equipment provide for high performance in applications involving advanced materials and structures.