TOUGHENING OF HIGHLY CROSS-LINKED EPOXY-RESINS BY REACTIVE BLENDING WITH BISPHENOL-A POLYCARBONATE .2. YIELD AND FRACTURE-BEHAVIOR

The yield and fracture behavior of highly crosslinked epoxy resin modi fied by a reactive blending process carried out in the presence of bis phenol A polycarbonate has been studied. It was found that the fractur e toughness of this blend system increases markedly with increasing PC content in the blend. Scanning electron microscopy of the fractured s urfaces indicated a crack blunting mechanism as the main source of ene rgy dissipation in the various investigated blend compositions. No evi dence of phase separation of the minor component during the curing and postcuring steps was observed. The yield data were correlated with th e fracture toughness data to evaluate the extent of crack-tip blunting . (C) 1994 John Wiley & Sons, Inc.