FOURIER-TRANSFORM INFRARED-ANALYSIS OF POLYCARBONATE EPOXY MIXTURES CURED WITH AN AROMATIC AMINE/

In our previous article, we established that polycarbonate (PC) can re act with the diglycidyl ether of bisphenol-A (DGEBA) at 200 degrees C through transesterification and addition reactions, resulting in degra ded PC chains with phenolic end groups and also in PC/DGEBA copolymers . However, these reactions can be minimized or eliminated at lower tem peratures, below 160 degrees C. In this article, Fourier transform inf rared analysis (FTIR) was used to study the curing kinetics of epoxies in the presence of PC. The curing agent was an aromatic amine, diamin odiphenyl methane (DDM). FTIR results showed that the presence of a sm all amount of PC promoted the amine-epoxide reactions, probably due to the catalytic effect of the phenolic end groups in the PC chains. How ever, the PC did not alter the epoxy cure reaction mechanism. Two diff erent blending processes were used to premix the PC and DGEBA, namely, solution-blending and melt-blending processes, in order to give diffe rent extents of prereactions. If a solution-blending process was used, PC tended to undergo crystallization during an early stage of cure. W hen a melt-blending process was used, no melting peak was observed in the thermograms of the differential scanning calorimeter (DSC) for the modified epoxies; PC chains bonded to DGEBA during prereaction at 200 degrees C, thus inhibiting the crystallization of PC during cure. (C) 1998 John Wiley & Sons, Inc.