Phase Separation in Thermosetting Blends Studied by Dynamic Dielectric Analysis

Abstract

Phase separation in unreinforced reactive blends has been studied using a variety of experimental techniques. A brief review of such studies is given, followed by a detailed description of the theory and practical applications of the new technique of dynamic dielectric analysis, DDA, as used in this context. Methods of data analysis and the extent of information available from in situ, real-time, measurements by dynamic dielectric analysis are illustrated by examples of results on model blends of simple epoxy/hardener mixtures with CTBN or POP rubber, or thermoplastic PES or PMMA. Deliberate ion doping is shown to enhance the phase separation features in the dielectric signal. Data are also presented on complex commercial thermoset/thermoplastic blends utilized as the resin matrices in carbon fibre pre-preg systems. Phase separation in a blend of epoxy and thermoplastic PEI can be studied by DDA within a glass fibre composite; this presents no additional difficulty compared with the studies of the corresponding unreinforced blend.