Herein, high density polyethylene (HDPE) matrix was applied as the polymer matrix for its excellent overall performance and low price. In the study, antioxidants (0.5 phr) and ultraviolet absorber (1 phr) were added into the polymer matrix (100 phr) to investigate their influence on UV resistance, respectively. The macroscopic properties and microstructure changes of the samples were both investigated through the characterizations of Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), mechanical properties and thermogravimetric analysis (TGA). This work also conceived the three methods of capturing free radicals generated by photoaging, decomposing peroxides generated by photoaging, and absorbing ultraviolet light to achieve anti-aging effects. The results showed that the UV absorber improves the UV resistance of the material better than the antioxidant. After irradiation for 600 h under the aging condition of 0.51 w/m2@λ = 340 nm, the samples added with UV absorber also still maintain their mechanical properties at a high level. For comparison, the samples added with antioxidants presents poor mechanical properties only after irradiation for 200 h. Besides, the crystallinity of HDPE and HDPE added with antioxidant significantly increased after irradiation, but the crystallinity of HDPE introduced with UV absorber presents slight changes before and after irradiation. Meanwhile, all the irradiated samples also maintained the original excellent thermal stability. According to the obtained results, the aging mechanism was also analyzed.

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UV resistance of versatile plastics has been received attention for a long time, especially of high‐density polyethylene (HDPE). It was studied systematically that hindered amine light stabilizer (HALS) with different molecular structures had an effect on the UV resistance of HDPE. The molecular weights of the two HALS were 423.7 and 2100–3000 g/mol, respectively. It was found that the low‐molecular‐weight HALS outperforms the polymeric one of HDPE matrix in UV resistances due to the different molecular structures. HDPE‐containing HALS with different molecular structures followed different degradation mechanisms during artificial accelerated aging. In addition, HDPE matrix composites with low‐molecular‐weight HALS show better mechanical properties than the polymeric one because of the decrease of delay of molecular chain fracture during irradiation. Therefore, HDPE matrix composites with low‐molecular‐weight HALS have better UV degradation resistance. However, polymeric HALS has the advantage of hard to move out of the sample surface.

In order to improve the aging resistance of HDPE, antioxidants (Irganox1010 and Irgafos168) are combined with UV absorber (UV‐326 or UV‐531). Analyses of ultraviolet–visible (UV–vis) and Fourier transform infrared spectroscopy show that UV‐326 has a better capacity of UV absorbance, but easier to migrate to the HDPE surface due to the bigger difference of solubility parameter with HDPE than UV‐531. The mechanical property indicates a better synergistic effect between UV‐531 and antioxidants. With the single addition of antioxidant, the mechanical property sharply decreased to low level during irradiation for 200 h. With single addition of UV absorber, the elongation at break of the sample can still be maintained at about 700% until irradiation for 600 h. When two different UV absorbers are used in combination with antioxidants, HDPE with UV‐326 maintains high mechanical property when irradiated for 1200 h, while the samples containing UV‐531 still maintain good mechanical property when irradiated for 1600 h.

In this study, the ultraviolet (UV) resistance of highdensity polyethylene (HDPE)/titanium dioxide (TiO 2 ) 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/TiO 2 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/TiO 2 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.

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A high near-infrared (NIR) reflective cooling compound with flame retardant characteristics was fabricated by incorporating antimony trioxide (Sb 2 O 3 ) and decabrominated diphenyl ethane (DBDPE) into ethylene-vinyl acetate copolymer (EVA). The solar reflectivity and cooling capacities of the control sample and EVA compounds with either Sb 2 O 3 or DBDPE, and EVA composites embedded with Sb 2 O 3 and DBDPE, were evaluated by ultraviolet-visible-near infrared analysis and temperature tests. The effect of Sb 2 O 3 and DBDPE on the flammability, thermal behavior, and mechanical properties of EVA copolymer were determined via the UL-94 burning test, limiting oxygen index (LOI), differential scanning calorimetry, thermogravimetric analysis, and tensile and tearing tests. Compared with the glass blank, EVA compound filled with 10 wt% Sb 2 O 3 and 30 wt% DBDPE showed a roughly 17.3 C and 38.0 C decrease during sunlight exposure and in indoors, respectively, accompanied by the maximum NIR reflectivity of 68.8% in all as-prepared blends. Moreover, this as-prepared compound met a UL-94 V-0 classification and reached a LOI value of 29.3%. Notably, the singular addition of either Sb 2 O 3 or DBDPE improved the cooling capability of EVA but rarely fulfilled the fire retardant demand. In contrast, the incorporation of Sb 2 O 3 and DBDPE improved the desirable cooling and flame retardant properties.