Preparation of free radical/cationic hybrid UV-cured silicone materials with reducing oxygen inhibition via silyl radicals

Abstract

UV-curing technology is a new, green technology with the advantages of being efficient, energy-saving, and environmentally friendly; however, there is a general oxygen-inhibition problem during the UV-curing process, especially when silicone acrylates are applied to the UV-curing treatment. Herein, epoxy-based silicone prepolymers (ESP) containing Si-H bonds were prepared through the hydrosilylation reaction of poly(dimethylsiloxane-co-methylhydrosiloxane) (PDMS-PHMS) and allyl glycidyl ether (AGE) to graft epoxy groups onto silicone segments while retaining part of the Si-H bond. The epoxy groups in the prepolymers are capable of cationic photopolymerization, and the retained Si-H bonds in the prepolymers can generate highly reactive silyl radicals for initiating free-radical photopolymerization. The anti-oxygen inhibition ability of silicone acrylates was enhanced with the addition of ESPs. Through experimental investigation, it was found that ESP-3 grafted with 0.30% epoxy groups had the best effect on reducing oxygen inhibition, and the silicone acrylates were able to undergo UV curing in air without sticky surfaces when the added amounts of ESP-3 were at 20 wt%. The addition of ESP-3 has no major impact on the transparency and thermal performance of the UV-cured coatings and further enhances their hydrophobic properties. The free radical/cationic hybrid UV-cured silicone materials reduce the problem of oxygen inhibition, and the UV-cured silicone materials have great potential as hydrophobic and self-cleaning materials.