POLYCARBONATE-MODIFIED EPOXIES .1. STUDIES ON THE REACTIONS OF EPOXY RESIN POLYCARBONATE BLENDS PRIOR TO CURE/

An epoxy resin based upon the diglycidyl ether of bisphenol-A was modi fied with poly(bisphenol A carbonate) (PC). Prior to aromatic amine cu re, the possible reactions in the epoxy resin/PC blend were investigat ed using GPC and FTIR techniques. It was shown that at 150 degrees C, the epoxy resin acted as a plasticizer and promoted the crystallizatio n of PC. In addition, a transesterification between the secondary hydr oxyl groups in the epoxy resin with the carbonate groups in PC occurre d. This reaction resulted in degraded PC chains with phenolic hydroxyl end groups. There was no evidence of reaction of epoxide groups at 15 0 degrees C in this blend. At 200 degrees C, the secondary hydroxyl gr oups acted as a catalyst converting most of the aromatic-aromatic carb onates to the aromatic-aliphatic and aliphatic-aliphatic carbonates th rough transesterification. At this elevated temperature, the secondary hydroxyl groups were regenerated by the addition reaction between the epoxide groups and the phenolic hydroxyl end groups, either from the transesterification or the hydrolysis of PC. This addition reaction co mbining the PC chains and epoxy chains eventually resulted in a crossl inked polymer if the extent of reaction was high. Thus, by using a mel t blending process at high temperature, e.g., 200 degrees C, a copolym er network structure of PC-modified epoxy could be formed. The fractur e toughness should be increased by increasing the capability for plast ic deformation due to the incorporation of PC chains into the network; results will be reported in a future study. (C) 1996 John Wiley & Son s, Inc.