Evaluation of cooling property of high density polyethylene (HDPE)/titanium dioxide (TiO₂) composites after accelerated ultraviolet (UV) irradiation

Abstract Cool materials targeted to minimize temperature are employed to lower energy consumption and the heat island effect. UV damage of cool materials appears to be inevitable when they serve as outdoor applications. Among researches into cool materials, the effect of UV irradiation on cooling property and stability of materials have been barely considered. In this work, UV irradiation of high density polyethylene (HDPE)/titanium dioxide (TiO₂) composites were performed via the artificial accelerated xenon lamp UV irradiation process. Structural changes were studied by wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR). A spectrometer was applied to measure solar reflectance before and after UV irradiation. The advantage of the high solar reflectance of the specimen remained after UV irradiation. The relationship between UV irradiation and solar reflectance was discussed. The solar reflectance after UV irradiation depended on changes of the crystallinity, surface roughness of composite and the structure of TiO₂. It was interesting to find that the anatase TiO₂ particle could slightly increase the solar reflectance in the near infrared region after UV irradiation, which may provide an approach to achieve high reflectance of polymeric materials in the near infrared region. Finally, the temperature test was conducted to evaluate the effect of UV irradiation on the actual cooling property by a self-designed device, of which, the result was in accordance with the result of solar reflectance.