Highly soluble phenylethynyl-terminated imide oligomers based on KAPTON-type backbone structures for carbon fiber-reinforced composites with high heat resistance

Abstract

Novel addition-type phenylethynyl-containing imide oligomers (degree of polymerization: n=1–10) derived from 1,2,4,5-benzenetetracarboxylic dianhydride or pyromellitic dianhydride (PMDA), 2-phenyl-(4,4′-diaminodiphenyl ether) (p-ODA) and 4-phenylethynylphthalic anhydride (PEPA) were prepared and evaluated as a matrix resin for high heat-resistant carbon fiber-reinforced composites. The uncured imide oligomers showed good solubility (>30 wt%) in N-methyl-2-pyrrolidone and very low melt viscosities. These imide oligomers were successfully converted to crosslinked structures after curing at 370 °C. The glass transition temperature (Tg) and the elongation at break (ɛb) of the cured imide resin were found to be excellent (almost 340 °C and >15%, respectively). The carbon fiber prepreg was prepared from the imide oligomer solution and used to fabricate void-free laminates with high Tg. The thermal and mechanical properties of the laminates were determined at ambient temperature.