Influence of the Copolymer Content on the Miscibility, Phase Behaviour and Morphology of a DGEBA/Polystyrene/Styrene‐co‐Maleic Anhydride Ternary Blend

Abstract

The miscibility, phase behaviour and morphology of ternary systems, formed by a DGEBA‐based epoxy resin, polystyrene (PS) and styrene‐co‐maleic anhydride (SMA) copolymers have been investigated through phase diagrams. The analysis has been done in the absence and in the presence of 4,4′‐methylene bis(2,6‐diethyl aniline) (MDEA) as curing agent. In both cases, the influence of the copolymer content on blend compatibility, has been discussed. The results show that miscibility is enhanced by the presence of SMA copolymer in the blend and as the MA content in the copolymer is increased (from 7 to 14 wt.‐%), 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. Experimental results have been fitted with a thermodynamic model based on the classical Flory–Huggins lattice theory, by using interaction parameters, depending both on temperature and composition. The presence of MDEA cross‐linking agent, yielded microphase‐separated materials. The morphological evolution of this epoxy networks, with and without PS + SMA thermoplastic modifier, has been examined by scanning electron microscopy (SEM).magnified image