Study on modified phenolic resin. II. Modification with <i>p</i>‐hydroxyphenylmaleimide/styrene copolymer

Abstract

Abstract The improvement of heat resistance and mechanical properties of phenolic resin was examined with the blend of novolac and copolymers prepared from p ‐hydroxyphenylmaleimide (HPMI) and styrene. Copolymers of HPMI and styrene with various molecular weights were synthesized. Glass transition ( T g ) and thermal decomposition temperatures of the copolymers were measured by differential scanning calorimetry (DSC) and thermogravimetry (TG), respectively. The miscibility of the copolymers with novolac was examined by DSC. It was found that the copolymers had a good heat resistance and a good miscibility with novolac. Molding compounds were prepared by hot roll‐kneading of mixtures that involved novolac, copolymer, hexamethylenetetramine (hexamine), and glass fiber. It was found that the test pieces prepared by transfer molding from the molding compounds showed a good heat resistance and better mechanical properties than phenolic resin modified with HPMI homopolymer.