Properties of Glass Laminates of Novolac Epoxy -Diallyl Bisphenol A -Bismaleimide Resins

The high temperature properties of a novolac epoxy (EPN) – 2,2 ' diallyl bisphenol A (DABA) resin system was improved on co-curing it with bisphenol A bismaleimide (BMI). The concentration of BMI in the stochiometric blend of EPN and DABA was varied from 0.5 to 2.0 per equivalent of allylphenol. This ternary blend was used for processing glass laminates and their performance was evaluated through thermal, mechanical and dynamic mechanical characterisation. The incorporation of BMI in an epoxy-phenol system yielded a matrix system with comparable mechanical properties, improved high temperature stability and high temperature strength retention. The increase in BMI concentration beyond the stochiometric equivalent caused deterioration in mechanical properties including fracture toughness, and stress relaxation of the laminate. But the high temperature performance of the system evaluated through the interlaminar shear strength retention of their glass laminates showed systematic improvement with increase in BMI concentration. Toughening with polyethersulphone improved its mechanical properties, with a marginal penalty on its glass transition temperature.