A Comparative Study on the Cure Behaviour of Thermal- and Microwave-Processed Epoxy Resin

Abstract

The cure characteristics of the epoxy resin system, LY 3505/XB 3403, is investigated using two different modes of heating. In the first instance, the resin is cured on alumina pans in a multimode microwave oven while near infrared spectra and the temperature of the samples are recorded in real time. The spectra are recorded using a non-contact optical fibre probe while the temperature is measured using a commercially available fibre optic sensor. The temperature profile recorded inside the microwave oven during cure is simulated in a differential scanning calorimeter and the experiment repeated using conventional heat. Comparison is made between the two heating techniques and their effects on the rate of cure, as well as the glass transition temperature, are discussed. The results obtained suggest that there is no “microwave effect”, in other words, the absence of an accelerated rate of conversion of the resin system in a microwave environment. However, the scale-up studies show that the onset of cure is much faster in the case of microwave heating. It is also found that microwaves have a tendency to preferentially heat the more polar amine molecules.