Modification of Acid Anhydridecured Epoxy Resins By N-Phenyl- maleimideStyrene Copolymers and N-PhenylmaleimideStyrene p-Hydroxystyrene Terpolymers

Abstract

N-Phenylmaleimide-styrene copolymers (PMS) and reactive N-phenylmaleimide-styrene-p-hydroxystyrene (HSt) terpolymers (PMSH) containing p-hydroxyphenyl groups were used to improve the toughness of bisphenol A diglycidyl ether epoxy resin cured with methyl hexahydrophthalic anhydride. PMS and PMSH were effective modifiers for epoxies. The morphologies of the modified resins depended on modifier structure and content. The most effective modification for the cured resins was attained because of the co-continuous structure of the modified resins in both PMS and PMSH modification systems. When using 15 wt% of PMS (M W 125000), the fracture toughness, K IC , for the modified resin increased by 230%, with retention of flexural modulus and glass transition temperature, but with a loss of flexural strength, compared with the values for the unmodified epoxy resin. When using PMSH as the reactive modifier, the efficiency decreased with increase in HSt content, because of the increasing extent of dispersion of the PMSH-rich continuous phases. In the modification with 10wt% PMSH (1.0 mol% HSt unit, M W 294000), the modified resin had balanced physical properties.