Effect of hydrotalcite on the thermal stabilization performance of natural antioxidant vitamin E in Ziegler-Natta polyethylene

Abstract

Residual catalysts in Ziegler-Natta (ZN) polyolefins usually significantly impair the effectiveness of antioxidants and the incorporation of acid scavengers is an effective method to mitigate these detrimental effects. With the increasing use of natural antioxidants like vitamin E (VE) in human-safety applications, whether their stabilizing effectiveness is affected by catalyst residues and whether traditional acid scavengers remain effective have become key issues requiring urgent resolution. This study systematically investigated the impact of hydrotalcite, a conventional acid scavenger, on VE's thermal stabilization performance in ZN polyethylene (ZN-PE). The results demonstrated that combining 500 ppm VE with 500 ppm hydrotalcite significantly extended the oxidation induction time of ZN-PE to 55.7 min at 190 °C, which surpassed the 30.7 min achieved by 1000 ppm VE alone. The changes in chemical structure, mechanical properties, and color of different samples after multiple extrusions and accelerated aging further confirmed the strong synergistic effect of VE and hydrotalcite in enhancing the thermal-oxidative stability of ZN-PE. Mechanistic investigations revealed that hydrotalcite primarily functioned by eliminating the impairment of VE’s antioxidant efficiency caused by the ZN catalyst. Additionally, hydrotalcite exhibited a certain adsorption effect on VE, which could control the release of VE, thereby extending its antioxidant efficiency in ZN-PE. These findings highlight the critical role of acid scavengers in optimizing VE performance, providing an effective strategy to optimize the use of natural antioxidants in ZN polyolefin stabilization.