Miscibility and mechanical properties of epoxy resin polysulfone blends

Bisphenol A-based polysulfone (PSF) was found to be miscible with uncured bisphenol A-type epoxy resin, i.e. diglycidyl ether of bisphenol A (DGEBA), as shown by the existence of a single glass transition temperature (T-g) within the whole composition range. Miscibility between PSF and DGEBA is considered to be due mainly to entropy contribution. Furthermore, PSF was judged to be miscible with the 4,4'-diaminodiphenylmethane (DDM)-cured epoxy resin (ER) as revealed by the means of differential scanning calorimetry (d.s.c.), dynamic mechanical analysis (d.m.a.) and scanning electron microscopy (SEM). D.s.c. and d.m.a. studies showed that the DDM-cured ER/PSF blends had only one T-g. SEM observation revealed that the DDM-cured ER/PSF blends was homogeneous. Both tensile and flexural properties of the DDM-cured ER/PSF blends slightly improved compared to those of the pure DDM-cured ER. Both fracture toughness (K-IC) and fracture energy (G(IC)) increased by ca. 20% with the addition of PSF to the system. Morphological investigation of the K-IC fracture surface suggests typical characteristics of brittle fracture. (C) 1997 Elsevier Science Ltd.