TOUGHENING OF VINYL ESTER RESINS WITH MODIFIED POLYBUTADIENES

This study is of toughening some vinyl ester resins with low-molecular -weight butadiene-based polymers. Liquid polybutadiene and copolymers with acrylonitrile are immiscible with the commonly used vinyl ester r esin, Derakane 411-45. Despite this incompatibility, some toughening i s seen in blends with this vinyl ester resin. Modification of hydroxy- terminated polybutadiene through reaction with a diisocyanate and vari ous alcohols renders the polymer more compatible but not miscible with the resin. With increasing length of the end-groups, the ability to p rovide a tougher cured resin improves such that the energy to propagat e a slow crack increases more than 10 times. Addition of 5 wt% of a bu tadiene polymer resulted in a disperse-phase volume fraction greater t han 10%. Blends with Derakane 411-45 showed greater toughness than tha t of the toughened resin Derakane 8084, which was also improved by add ition of butadiene copolymers.