Synthesis of epoxy-based silicone prepolymers with UV/moisture dual curability for applications in anti-graffiti coatings

Abstract

Ultraviolet (UV) photocuring technology has gained importance in crosslinking of polymers, as it allows fast curing rate, low energy consumption and no volatile organic compounds (VOCs). However, the photopolymerization of very thick films and in shadow areas where the light penetration is inhibited (e. g. in filled, pigmented, dispersed samples) remains a huge challenge. As reported herein, a simple hydrosilylation reaction was employed to synthesize epoxy-based silicone prepolymers. Firstly, the structures of the synthesized epoxy-based silicone prepolymers were characterized by Fourier-transform infrared (FT-IR) and proton nuclear magnetic resonance (1H NMR) spectroscopy techniques, thus confirming the successful synthesis of these prepolymers. The epoxy group of prepolymers could be crosslinked under UV irradiation, and its silicone methoxy group (-SiOCH3) was condensed under moisture ambient, so as to acquire both thick coatings and pigmented coatings due to the dual-curing approach. Moreover, water droplets exhibit water contact angles between 103° and 108° on these coatings, and surface energies of the these coatings are from 25.27 to 22.67 mN/m. The transparency of these coatings is over 90%. They remain stable at temperatures reaching up to 332.2 to 344.8 °C, thus demonstrating that they have excellent heat resistance. The coatings exhibited good mechanical properties with a tensile strength >4.57 MPa. Finally, the coatings have good anti-smudge and anti-fingerprint properties, and the overall results show that these films have potential applications as anti-smudge coatings.