RHEOLOGICAL AND DIELECTRIC CHANGES DURING ISOTHERMAL EPOXY-AMINE CURE

Dynamic viscosity and ionic conductivity were measured simultaneously during the cure of a digylcidyl ether of bisphenol-A (DGEBA) epoxy res in with diamino-diphenyl sulfone (DDS) by mounting a microdielectric s ensor into the plates of a rheometer. Two different cure temperatures were examined. Periodically, throughout the cure, samples were removed from the plates of the rheometer, quenched, and analyzed for the glas s transition temperature and epoxide conversion. The relationship betw een conductivity and viscosity appeared to be independent of cure temp erature. A linear relation with a slope of -1 was observed between the natural logarithms of conductivity and viscosity during the cure up t o approximately 85% cure conversion. It was hypothesized that the reac tion rate was hindered by diffusion at this stage in the polymerizatio n. A free volume relationship was used to successfully correlate condu ctivity with viscosity up to the diffusion limited region. (C) 1995 Jo hn Wiley & Sons, Inc.