The Study on the Stress-Photooxidation Aging of Polyethylene Cable Sheath under Different Processing Conditions Xiancheng Ren1 1College of Polymer Science and Engineering, Sichuan University, Chengdu 610065, Sichuan, China Polyethylene sheath materials were under stress, ultraviolet light, heat and other comprehensive factors in the process of actual use. Different molding process had influence on the state of aggregation structure and internal stress of polyethylene sheath materials, which lead to the difference of product aging resistant performance. The long-term stress-photooxidative aging behavior of highdensity polyethylene (HDPE) under different processing conditions was studied using a stress-aging apparatus. The aging behavior was investigated through the methods of the surface morphology observation, fourier transform infrared spectroscopy, differential scanning calorimetry and X-ray diffraction. It was found that the aging resistance of sheath had been associated with sheath surface layer crystallinity. Sample in the lower extrusion temperature system and higher extrusion speed had lower surface layer crystallinity, which the aging resistance was the best. In addition, the stress-photooxidation aging mechanism had been explored, there were two stages in the stress-photooxidation aging, reflected in the surface layer crystallinity increased at first and then decreased. Through the service life of cable sheath estimated, it was found that the service life of sheath material was effected by the extrusion technology and materials largely. This study may be useful for the rational selection of HDPE for the sheath material of bridge cable.