Preparation and properties of UV-curable polyurethane acrylate / SiO2 composite hard coatings

Abstract To achieve the high dispersion of SiO2 nanoparticles in polyurethane acrylate resin, the titanate coupling agent, PN-102, was used as the surface modifier to prepare the modified SiO2 nanoparticles (Si-PN102-5) with small particle size and good dispersion ability in PUA-6 resin. Accordingly, hydrophilic SiO2 (Si-380) and hydrophobic SiO2 (Si-115) were introduced into PUA-6 resin to prepare the corresponding composite coatings, so as to investigate the effects of SiO2 nanoparticles modified with different surface modifiers on the properties of PUA / SiO2 composite coatings. The properties of PUA / SiO2 composite coatings were characterized by the tests of FT-IR, AFM, SEM, DMA, TG and so on. The FT-IR and XPS results show that PN-102 had functionalized the Si-PN102-5 particle surface successfully. The TEM test displays that the particle size of SiO2 was almost unchanged before and after modification, maintaining at about 20–30 nm. The SEM, DMA and tensile test reveal that Si-PN102-5 not only blocks the interaction and accumulation of nanoparticles, but also enhances the interface interaction with polymer chains through chain entanglement, which endows Si-PN102-5-5% composite coatings with highest mechanical strength among the other prepared coatings, reaching to 11.0 ± 0.1 MPa in tensile strength and 9.4 ± 3.0% in elongation at break. The pencil hardness of the prepared Si-PN102-5-5% composite coating could reach to 5H which is higher than the commercial PUA-6 based coating, and it also displayed good adhesion (4B) and flexibility (3 mm). The TG results show that all of prepared composite coatings display good thermal stability with a decomposition temperature of higher than 250 °C.