Influence of Epoxy Nature on the Properties of an Epoxy– Diallylbisphenol A–Bismaleimide Matrix System

Abstract

The ternary matrix system comprising a reactive blend of epoxy, diallylbisphenol A, and bisphenol A bismaleimide (EPB) was found to be comparable with the epoxy–phenol (EP) system in terms of its mechanical properties, and superior to it in terms of its high-temperature performance. The influence of structural variations of the epoxy resin on the thermal, physical, and mechanical properties of the ternary blend was examined. EPB compositions were prepared using a combination of bisphenol A bismaleimide and diallylbisphenol A with three different epoxy resin systems, namely novolac epoxy (E1), bisphenol A diglycidyl ether (E2), and tris(4-glycidyloxyphenyl)methane (E3). Cure characterisation of these reactive blends (EPB–E1, EPB–E2 and EPB–E3) was carried out using IR spectroscopy, differential scanning calorimetry, and rheological analysis. The trend in their thermal stability, based on the temperature of the onset of decomposition, is EPB–E3 > EPB–E1 > EPB–E2. The mechanical properties – compressive, flexural, and interlaminar shear strength – of the glass composites of these matrices were found to depend on the epoxy structure. The higher crosslink density of the trifunctional epoxy improved the high-temperature properties of the system. The ternary system served as a very good adhesive, where its strength as well as its retention at high temperature increased in proportion to the functionality of the resin. In general, the maximum strength values were observed for the system containing the novolac epoxy.