Miscibility and cure kinetics of nylon/epoxy resin reactive blends

Abstract

The miscibility, phase behavior and cure kinetics of the reactive blends of an alcohol-soluble nylon with an epoxy resin, i.e. diglycidyl ether of bisphenol A (DGEBA), were studied by differential scanning calorimetry (d.s.c.) and Fourier transform infra-red spectroscopy (FTi.r.). Differential scanning calorimetry (d.s.c.) studies showed that all the uncured nylon/DGEBA blends were crystallizable and exhibited two glass transition temperatures (Tgs). The lower Tg is independent of composition and is due to the glass transition of DGEBA phase. The higher Tg varies with composition and is attributable to the glass transition of the nylon-rich phase. Nylon is partially miscible with DGEBA, and the extent of miscibility is dependent on the blend composition. Nylon and DGEBA in all the uncured blends can react with each other above 200°C. The curing reaction of nylon with DGEBA is dependent on the blend composition. The nucleophilic attack on oxirane ring by amide nitrogen of nylon is dominant curing reaction in low DGEBA compositions, and another type of curing reaction with relatively large activation energy and frequency factor also occurred which becomes dominant when the DGEBA content reaches 63 wt% or more. FTi.r. studies revealed three does exist two types of reactions during curing of nylon with DGEBA. All the cured nylon/DGEBA blends show a composition-independent Tg, which is the glass transition of cured nylon-DGEBA network. All other blends are uncrystallizable after curing except for the 9010 and 8020 nylon/DGEBA blends. The curing greatly destroyed the crystallinity of the blends.