Thermal and electrical properties of glass fiber reinforced o-cresol novolac epoxy composites cured with allylated phenol novolac hardener

An allyl group was introduced into a phenol novolac hardener to improve the thermal and electrical properties of glass fiber reinforced o-cresol novolac epoxy composites. Based on 1H NMR analysis, it was found that the degree of allylation was measured as 12.5% and 15.3% of allylated moieties underwent Claisen rearrangement. Thermal and electrical properties of the prepared composites were investigated by thermal mechanical analysis, dynamic mechanical analysis and dielectric measurements. Their thermal expansion coefficient and glass transition temperature measured by thermal mechanical analysis varied from 20.1 to 18.0 ppm K-1 and 132.5 to 170.9 degrees C, respectively, due to allylation of the phenol novolac hardener. From the storage modulus at the rubbery plateau, it was confirmed that these improvements were mainly caused by an increase in the crosslink density of the matrix resin owing to allyl groups. The electrical properties of the composites, however, showed no noticeable changes by allylation of the phenol novolac hardener. Copyright (c) 2012 Society of Chemical Industry