Low temperature microwave processing of silicone resin coatings containing microwave susceptors

Abstract

Microwave (MW) processing was used to cure a sol-gel type silicone resin coating that normally requires thermal curing over 250°C. The study focused on coatings applied on polycarbonate and poly(methyl methacrylate) substrates and processing temperatures did not exceed 100°C when using Silicone Carbide, Carbon, and Aluminium susceptors at 5% concentration by weight. Heating performance of the susceptors in bulk silicone resin matrix as well as in thin layers was compared.The results presented show that the heating response of the additives measured in bulk was significant. However, results for thin layers indicated that the effects of MW heating on the coatings containing the susceptors were limited, and samples microwaved at 800W for 4h imparted insignificant increase of the coating hardness.This outcome was supported by AFM Phase images which revealed no distinctive layer near the susceptor particles. This suggests that the heat dissipation to the substrate and air with limited heating performance of the susceptors does not allow for an effective in-situ curing in thin layer.