LLDPE/TiO₂ composites with high UV aging resistance and mechanical properties by controlling the alumina coating on TiO₂

Abstract For preparing high performance LLDPE film, the photocatalytic activity and the UV absorption capacity of TiO₂ were regulated by the alumina coating content on the surface of TiO₂. Alumina‐coated TiO₂ was prepared by the chemical liquid deposition method, and characterized by element analysis, TGA, FTIR, and morphology observation. The alumina coating layer had been proven to covalently bind to the surface of TiO₂ through AlOTi bonds, which formed a continuous and dense coating layer, followed by forming a loose flocculent coating layer with the increase of alumina content. The alumina coating layer could significantly reduce the formation of carbonyl group on the LLDPE chains, and enhance UV aging resistance of LLDPE by inhibiting the photocatalytic activity of TiO₂. Moreover, the dispersion of alumina‐coated TiO₂ in the LLDPE matrix was improved. Thus, the transmittance of LLDPE/alumina‐coated TiO₂ composites was reduced and the whiteness was improved. Importantly, the continuous and dense alumina coating layer was enough to inhibit the photocatalysis effect of TiO₂ on LLDPE. The further increase of alumina coating content reduced the UV absorption capacity of alumina‐coated TiO₂ and its compatibility with the LLDPE matrix. Therefore, the best alumina coating content on the surface of TiO₂ was 1.46 wt% for preparing high performance LLDPE/TiO₂ composites. Highlights Alumina‐coated TiO₂ with controllable coating thickness was successfully synthesized. LLDPE/alumina‐coated TiO₂ has excellent UV aging resistance and mechanical properties. The photocatalytic activity and UV absorption capacity of TiO₂ could be regulated. 1.46 wt% of alumina coating is the best content for high performance LLDPE/TiO₂ composites.