Enhanced stabilisation performance of HDPE via siloxane bonded ZnO with phenolic antioxidants

Abstract

The poor resistance of high-density polyethylene (HDPE) to thermal-oxidative aging and ultraviolet (UV) degradation significantly limits its service life. In this study, the nanocomposite ZnO-AO was synthesized using γ-glycidoxypropyltrimethoxysilane (GPTMS) as a bridging agent, which facilitated the loading of a significant quantity of the hindered phenolic antioxidant (AO) onto the surface of ZnO nanoparticles, and the HDPE/ZnO-AO composites were subsequently prepared by melt blending. The results indicated that the combination of ZnO and AO was synergistic, and the more optimized para-substituent structure of AO significantly reduced the hydroxyl bond dissociation energy (BDE) of the hindered phenols, thereby enhancing antioxidant activity. Additionally, the hydroxyl groups on the surface of ZnO were substituted with AO, which improved the particle dispersion. After 400 h of UV aging, HDPE/ZnO-AO retained 78.36 % and 95.92 % of its elongation at break and impact strength, respectively, compared to only 2.25 % and 6.17 % for pure HDPE. After 28 days of thermal-oxidative aging, the carbonyl index of HDPE/ZnO-AO increased by only 0.18, significantly lower than that of HDPE (0.43). Accordingly, the ZnO and AO, covalently linked by GPTMS, demonstrated enhanced performance compared to individual original capabilities, successfully integrating efficient thermal-oxidative stability and UV protection. This study provides a promising approach for the development of long-lasting HDPE composites.