Preparation of polyimides from mixtures of monomeric diamines and esters of polycarboxylic acids

Abstract

Abstract Polyimides having high thermal and oxidative stability are prepared by the reaction, with application of heat, of a mixture of monomers comprising (a) a dialkyl or tetraalkyl ester of an aromatic tetracarboxylic acid, (b) an aromatic diamine, and (c) a monoalkyl or dialkyl ester of a dicarboxylic acid wherein the ratio of a:b:c is n:(n+1):2, wherein n has a value of from 1 to 20. The mixture of monomers is prepared in a 30 to 70 percent by weight solution of an organic solvent, a substrate impregnated with the solution and heated at 50* to 205*C to remove said solvent and form a low molecular weight prepolymer, and thereafter heated at 275* to 350*C to cure to a high molecular weight polyimide. In a specific embodiment, graphite fiber is impregnated with a solution of 60 percent by weight of a mixture of 2,5-dicarbomethoxyterephthalic acid, methylenedianiline, and 5-norbornene-2,3-dicarboxylic acid monomethyl ester in dimethyl formamide, the impregnated fiber heated at 50* to 120*C to remove solvent, and thereafter heated at about 205*C to form imidized prepolymer and then at 315*C to form a high molecular weight thermally stable polyimide.

Inventors

• 👤 T Serafini
• 👤 P Delvigs
• 👤 G Lightsey

Bibliographic Details