Influence of epoxy hardener on miscibility of blends of poly(methyl methacrylate) and epoxy networks

In this paper, we investigate poly(methyl methacrylate) (PMMA)-modified epoxy thermoset based on DGEBA before and after curing of the epoxy with various aromatic amines by means of different techniques: Differential Scanning Calorimetry (DSC), Size Exclusion Chromatography (SEC), Infra-Red Spectroscopy (FT-IR), Dynamic Mechanical Analysis (DMA) and Transmission Electron Microscopy (TEM). The DSC analyses demonstrate the complete miscibility between PMMA and DGEBA. Neither specific interaction nor transesterification reaction is revealed by SEC and FT-IR between these components. With respect to reactive blends, the nature of the curing agent affects the polymerization kinetics and the structure of the PMMA-modified epoxy network. The usual polymerization induced phase separation occurs using DDS or MDA leading to a material with a two-phase structure revealed by TEM and DMA. On the other hand, the use of MCDEA as curing agent does not entail any noticeable phase separation during curing even if cured samples appear slightly turbid. No acceleration of the epoxy-amine reaction can be observed contrary to DDS and MDA based blends presenting the usual acceleration of the reaction just after the phase separation. In the case of blends using MCDEA as the hardener, we really have what some call a semi-TPN. (C) 2000 Elsevier Science Ltd. All rights reserved.