Triarylphosphine Oxide Containing Nylon 6,6 Copolymers

Abstract

A hydrolytically stable triarylphosphine oxide containing dicarboxylic acid monomer, bis(4-carboxyphenyl) phenyl phosphine oxide P(O)(Ph)(C6H4COOH)2, was synthesized via Friedel-Crafts reactions and chemically incorporated into the poly(hexamethylene adipamide) backbone to produce melt processible, improved flame-resistant copolymers. The content of triarylphosphine oxide comonomer in the melt synthesized copolymers was controlled from 0-30 mole%. The copolymers were crystallizable at 10 and 20 mole% incorporation of the phosphine oxide comonomer and produced tough solvent resistant films. The crystallinity was totally disrupted at 30 mole%, but the Tg values systematically increased from 58°C to 89°C. Dynamic TGA results in air at 10°C/minute showed that the char yield increased with phosphine oxide content. Cone calorimetric tests in a constant heat environment (40 kW/m2) were employed to investigate the fundamental flame retardancy behavior of the copolymers. Significantly depressed heat release rates were observed for the copolymers containing phosphine oxide, although carbon monoxide values appeared to increase. ESCA studies of the char show that the phosphorus surface concentration was significantly increased relative to copolymer composition. It was concluded that the triaryl phosphine oxide containing nylon 6,6 copolymers had improved flame resistance and that tough melt processible films and fibers could be produced from these modified copolyamides.