Miscibility of a DGEBA Based Epoxy Resin Blended with Thermoplastic Mixtures of Poly(styrene) and Block Copolymers: Influence of the Copolymer Content and Chemical Nature

The miscibility and phase behavior of ternary systems formed by a DGEBA based epoxy resin, polystyrene (PS), and diblock copolymers has been investigated through phase diagrams experimentally obtained by using a light transmission device. The analysis has been done in the absence and in the presence of a curing agent. In both cases, the influence of the copolymer content and chemical nature (PS-b-PMMA or PS-b-PHEMA) has been discussed. The results show that miscibility is enhanced as the copolymer content in the ternary blend is increased, due to specific H-bonding interactions between the H-donor hydroxyl groups on the epoxy resin and the H-acceptor carbonyl groups in the copolymer, the effect being more pronounced with PMMA than with PHEMA. Experimental results have been fitted with the Flory-Huggins theoretical model by using interaction parameters depending both on temperature and composition. The morphological evolution of the epoxy networks has been examined by scanning electron microscopy (SEM).