CURE BEHAVIOR OF AN EPOXY-NOVOLAC MOLDING COMPOUND

The isothermal cure of an epoxy-novolac molding compound was studied by means of differential scanning calorimetry (DSC). The glass transition temperature (T(g)) of the molding compound increased in an approximately linear manner with conversion (alpha) during the major part of the cure process. Predictions of an empirical kinetic scheme (established earlier from dynamic DSC results) compared favorably with the present isothermal results in the absence of vitrification. In combination with the gel point conversion (alpha(gel)) determined via dynamic rheological analysis and gravimetric measurements, our DSC results indicated that gelation bears no apparent effect on the rate of cure whereas vitrification retards the cure reaction. Based on the measured alpha(gel), the approximate T(g)-alpha-relationship, and the thermokinetic results, the time-temperature-transformation diagram of this molding compound was constructed and discussed.