Synthesis of UV rapid curing silicone coatings via photoinitiated thiol-ene click polymerization for pressure-sensitive adhesive

UV-curable silicone pressure-sensitive adhesive (SPSA) is composed of silicone rubber and silicone resin. Generally, the C[dbnd]C double bond in acryloyloxy group provides a photocurable group for SPSA. However, oxygen inhibition of acryloyloxy group block the degree of cure and C[dbnd]C double bond conversion of SPSA during the photopolymerization. Therefore, efficient photocurable groups for UV curing SPSA is particularly important to be developed. Thiol-ene click polymerizations have been widely used in photocrosslinked polymers due to the rapid efficiency of reactions. In this study, sulfhydryl functionalized silicone resin (SFSR) and methacrylate functionalized amino silicone rubber (MFASR) were synthesized to prepare a SPSA via photoinitiated thiol-ene click polymerization. The double bond in MSASR and sulfhydryl in SFSR were characterized by FT-IR spectroscopy and ¹H NMR spectroscopy. The double bond conversion of SPSA was calculated after polymerization. The cohesion of SPSA was improved by SFSR, while the crosslinking degree was improved by thiol-ene. The loop tack of SPSA with 50 wt% SFSR was 9.01 N, and the 180° peel strength was 11.37 N/25 mm. The SPSA maintained good bonding adhesion to steel at various temperature.