Epoxy resins modified with poly(vinyl acetate)

Miscibility and curing behaviour have been studied in blends of poly(vinyl acetate) (PVAc) with diglycidyl ether of bisphenol A (DGEBA) resin and 4,4′-diaminodiphenylsulphone (DDS) used as curing agent. The PVAc component was used as a potential toughness modifier. Binary mixtures DGEBA+PVAc show complete miscibility over the whole composition range. Ternary mixture DGEBA+DDS in stoichiometric ratio +10% (w/w) PVAc behaves also as homogeneous phase. However PVAc was found to be inmmiscible with the highly amine-cross-linked epoxy resin. It was found that phase separation in DGEBA+DDS+PVAc blends occurred as the conversion reaches a value close to 40%. In the final cured material two phases are present: an epoxy phase and a PVAc phase. It was also found a slow down of the reaction when PVAc was present.