Superior UV Resistance of Unsaturated Polyester Resin by Employing Amorphous e-TiO₂ Nanoparticles for Outdoor Applications

Unsaturated polyester resin (UPR) is widely used in different industries. However, its applications are still limited to indoor applications as it can be degraded under UV radiation. In this study, we report a concept of producing modified UPR by employing amorphous e-TiO 2 nanoparticles (NPs) with high UV resistance, long-term protection, cost-effectiveness, and simple and large-scale production, allowing it to be utilized to develop outdoor applications in an industrial scale. The UPR/e-TiO 2 nanocomposite was produced by in situ polymerization with the presence of e-TiO 2 during the UPR formation. The composite materials were revealed to maintain advanced chemical and mechanical properties of UPR while improving its thermal durability. The glass transition temperature of UPR/e-TiO 2, with e-TiO 2 contents ranging from 0.25 to 1.00%, was measured to be in the range of 98–105 °C, significantly higher than that of UPR (78 °C). More importantly, with the optimal TiO 2 content of 0.50%, the color change value of UPR/e-TiO 2 after 1000 h of UV exposure was calculated to be 77.5% lower than that of the original UPR, indicating a significant improvement in UV resistance of the composite. It was further explained by the poor photocatalytic activity of amorphous e-TiO 2 NPs as the disordered electronic structure of amorphous e-TiO 2 easily led to recombination of electron–hole pairs. Finally, the UPR/e-TiO 2 nanocomposite was employed to produce artificial quartz stone samples, showing the high feasibility of advanced outdoor applications. The UPR/e-TiO 2 nanocomposite could be a suggestion to pave the way toward industrial outdoor applications of UPR-based materials.