Enhanced UV resistance of solar cooling high density polyethylene/titanium dioxide composites for long outdoor life via synergy effect of UV absorber and antioxidant

In this study, the ultraviolet (UV) resistance of high-density polyethylene (HDPE)/titanium dioxide (TiO₂) composites was investigated. It is widely known that UV absorber could efficiently improve the UV resistance of the composites, and prevent the composites from being damaged by UV light. However, a small percentage of UV light still exist that may cause damage to material only with the assistance of UV absorber. Therefore, antioxidant was used in combination with UV absorber to further improve the UV resistance of the materials. Herein, three kinds of main antioxidants were used in combination with one kind of auxiliary antioxidant, and simultaneously UV absorber was added into the matrix material to enhance the UV resistance of the HDPE/TiO₂ composites. It was found that antioxidant could prevent the break of the molecular chains during preparation processing and reduce the rate of the photo-oxygen degradation during UV irradiation. As the aging time increases, the crystallinity of the composites increased, but the control HDPE increased the most. The reflectance of the composites without antioxidant showed a slight decrease after UV irradiation, whereas the reflectance of the composites containing antioxidant still maintained the same level after UV irradiation. With the enhancement of the aging resistance of HDPE/TiO₂ composites, the general characters were highlighted without sacrificing the excellent solar reflectivity and great cooling performance. Besides, with the addition of antioxidant and UV absorber, excellent mechanical properties of the composites can be also achieved after UV irradiation. J. VINYL ADDIT. TECHNOL., 25:303–309, 2019.