Curing kinetics and characterization of dual-curable thiol-acrylate-epoxy thermosets with latent reactivity

摘要

A new dual-curing scheme was developed for thiol-acrylate-epoxy mixtures. A photo-initiated latent catalytic system was used to carry out thiol-acrylate Michael addition at 35 degrees C (Stage 1) followed by thiol-epoxy click reaction (Stage 2) at 80-110 degrees C. The intermediate materials were shown to have several days of storage stability. The use of a radical inhibitor has suppressed radical mediated acrylate homopolymerization which would otherwise lead to unreacted thiols remaining. Kinetics of Stage 2 was analyzed mathematically using iso-conversional differential method and Kamal model regression. Glass transition temperatures (T-g) of samples with varying contents of epoxy and different types of acrylates were measured. Epoxy-rich formulations gave the highest final T-g. Although not as influential as the epoxy content, using higher functional and more rigid acrylate monomers resulted in higher intermediate and final T-g. The proposed curing scheme and the resulting materials could be useful in applications such as adhesives, industrial coatings with high chemical resistance, optical and electronic materials.