Room-temperature fast-curing polybenzoxazine hybrid thermosets via UV irradiation

Room-temperature fast-curing polybenzoxazine hybrid thermosets were synthesized by crosslinking allyl-containing benzoxazine oligomer (O-ABZ) and thiol-containing siloxane oligomer (O-TS) under UV irradiation via thiol-ene click reaction. The O-ABZ was synthesized through the thermally-activated ring-opening polymerization of mono-functional benzoxazine (ABZ) obtained via Mannich reaction of the p -cresol, allylamine, and paraformaldehyde. The O-TS was synthesized by the co-hydrolysis and condensation of 3-mercaptopropylmethyldimethoxysilane with dimethyldimethoxysilane. The structures and molecular weights of O-ABZ and O-TS were characterized by FT-IR, 1 H NMR, and SEC. The kinetics of thiol-ene click reaction were studied by FT-IR spectroscopy. The results showed that the curing reaction of polybenzoxazine/polysiloxane hybrid resin proceeded rapidly at room temperature under UV irradiation. The conversions of thiol and allyl groups were 56.6% and 58.3% in the first 30 s, respectively. Nearly complete curing was obtained after 3 min of UV irradiation. Meanwhile, the gel contents of the resulting resin were greater than 95%. On the other hand, the crosslinking density of the hybrids could be tuned by adjusting the thiol content of the siloxane oligomers. Their physical states transformed from rubber to plastic.