Continuous UV cure monitoring and dielectric properties of photocross-linked epoxy–acrylate resins

The changes in viscosity of epoxy–acrylate resins during the photocross-linking process have been monitored continuously. The curing show change of shape and a distinct peak especially at high intensities. The intensity dependence of gel time follows a superlinear power law of the type t_pαI^?1.6 rather than the ½ power law. The dielectric relaxation studies on these photocross-linked films having different compositions of epoxy and n-butyl methacrylate reveal a particular composition range in which various dielectric parameters pass through critical values. These various findings have been explained on the basis of phase separation taking place during the UV curing process but at a submicron level leading to a very small domain size. © 1994 John Wiley & Sons, Inc.