Morphology profiles obtained by reaction-induced phase separation in epoxy/polysulfone/poly(ether imide) systems

Abstract

The reaction-induced phase separation in epoxy/aromatic diamine formulations simultaneously modified with two immiscible thermoplastics (TPs), poly(ether imide) (PEI) and polysulfone (PSF), has been studied. The epoxy monomer was based on the diglycidyl ether of bisphenol A (DGEBA) and the aromatic diamine was 4,4′-methylenebis(3-chloro 2,6-diethylaniline) (MCDEA). Phase-separation conversions are reported for various PSF/PEI proportions for blends containing 10 wt% total TP. On the basis of phase-separation results, a conversion–composition phase diagram at 200 °C was compiled. This diagram was used to design particular cure cycles in order to generate different morphologies during the phase-separation process. It was found that, depending on the PSF/PEI ratio employed, a particulate or a morphology characterized by a distribution of irregular PEI-rich domains dispersed in an epoxy-rich phase was obtained for initially miscible blends. Scanning electron microscopy (SEM) characterization revealed that the PEI-rich phase exhibits a phase-inverted structure and the epoxy-rich matrix presents a bimodal size distribution of TP-rich particles. For PSF/PEI ratios near the miscibility limit, slight temperature change result in morphology profiles.