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

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 FTIR, AFM, SEM, DMA, TG and so on. The FT-IR and XPS results show that PN-102 had functionalized the SiPN102-5 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 degrees C.