Propargylated novolac resins for solvent-free technology for high-performance composites

Propargyl substituted novolac phenolic resin diluted with unsaturated bisphenol-A ethers was used for glass fiber solvent-free impregnation for the formation of high-performance composites. The addition of 20% mass of diallyl (DAEBA) or dipropargyl (DPEBA) bisphenol-A to propargyl substituted novolac phenolic resin resulted in viscosity drop from 2000 mPa∙s to 400‒500 mPa∙s at 140 °C. This proved to be enough to achieve complete impregnation of the twisted glass fibers, as illustrated by SEM analysis. This improvement in impregnation was shown to result in increasing both flexural strength and modulus of the unidirectional glass fiber composite material approximately with a factor of two compared to the composite impregnated with resin without bisphenol-A ethers. DPEBA was shown to be more suitable for high-temperate applications since its addition does not seem to result in a decrease of the heat deflection temperature (HDT).