Anomalies between microwave and thermal cure kinetics of epoxy-amine resinsystems

The cure of the epoxy systems MY721/27% DDS at 160 degrees C and MY721/32% DDM at 120 degrees C have been investigated in both rectangular and cylindr ical microwave cavities and thermally. The cure rates were monitored by FT- NIR spectroscopy over the region 4750-7250 cm(-1). The rates of cure in the microwave cavities, estimated from both the primary and epoxy group concen trations, were found to be different, and different from the rate observed for thermal cure in a heated aluminium block. This anomalous behaviour has been attributed to spatial inhomogeneity in the temperature of the epoxy sa mples, arising from inhomogeneity in the microwave field in the cavity, rat her than to specific absorptions of the microwave radiation by the reactive groups in the epoxy samples, as has been suggested previously by some othe r authors.