Toughening bimodal vinyl ester blends using bio-rubber monomers

Abstract

Vinyl ester (VE) resins are commonly used as matrix materials in the manufacture of polymer matrix composites (PMC). However, most commercial VE resins are brittle and contain considerable amounts of styrene (ST) which is a hazardous air pollutant (HAP) as well as a potential carcinogen. VE resins formulated using bimodal blends of vinyl ester monomers offer both an increase in fracture performance while maintaining low viscosities without the addition of extra styrene or other additives. In this work, bio-based rubber modifiers were synthesized and combined with selected bimodal blends of VE. It was found that the addition of bio-rubbers (BR) to bimodal VE systems results in significant fracture toughness improvement by the generation of a rubbery dispersed second phase with characteristic dimensions less than 500 nm. For example, the G1c of a selected VE bimodal blend initially containing 35 wt % styrene increased from 286 J/m2 to 773 J/m2 with the addition of 15 wt% BR. Negligible effects on the resin viscosity (~ 2300) cP were observed, the Tg remained above 100°C and styrene content was reduced to 30%. Addition of a small amount of styrene was found to reduce the viscosity of the resin to levels acceptable for liquid molding applications with minimal effects on toughness and Tg.%%%%M.S., Chemical Engineering – Drexel University, 2011