Three polyurethane films were prepared by adding the antioxidant-1010 and the composite stabilizer to the polyurethane matrix, respectively. The accelerated weathering tests were performed by using self-designed UV/ozone aging test device. The color difference, yellowness index, UV-Vis spectrum, and infrared spectrum were recorded with colorimeter apparatus, UV-Vis spectroscopy, and FT-IR spectroscopy, respectively. The results show that, for the polyurethane film, the composite stabilizer can remarkably decrease UV transmission, the antioxidant-1010 and the composite stabilizer can markedly decrease the photooxidation index and the carbonyl index, respectively, and the antioxidant-1010 can significantly improve the antiyellowing properties after 60 h exposure. With incremental exposure time for the three films, UV-Vis transmission decreases, the photooxidation index, the carbonyl index, color difference, and yellowness index increase gradually. Under current experimental conditions, the order of UV/O3aging resistance from highness to lowness is as follows: the polyurethane film modified by the antioxidant-1010, the polyurethane film modified by composite stabilizer, and the pure polyurethane film.

The pure polyester polyurethane (TPU) film and the modified TPU (M-TPU) film containing 2.0 wt.% inorganic UV absorbers mixture (nano-ZnO/CeO2with weight ratio of 3 : 2) and 0.5 wt.% organic UV absorbers mixture (UV-531/UV-327 with weight ratio of 1 : 1) were prepared by spin-coating technique. The accelerated aging tests of the films exposed to constant UV radiation of 400 ± 20 µW/cm2(313 nm) with an ozone atmosphere of 100 ± 2 ppm were carried out by using a self-designed aging equipment at ambient temperature and relative humidity of 20%. The aging resistance properties of the films were evaluated by UV-Vis spectra, Fourier transform infrared spectra (FT-IR), photooxidation index, and carbonyl index analysis. The results show that the composite UV absorber has better protection for TPU system, which reduces distinctly the degradation of TPU film. O3/UV aging of the films increases with incremental exposure time. PI and CI of TPU and M-TPU films increase with increasing exposure time, respectively. PI and CI of M-TPU films are much lower than that of TPU film after the same time of exposure, respectively. Distinct synergistic aging effect exists between ozone aging and UV aging when PI and CI are used as evaluation index, respectively. Of course, the formula of these additives needs further improvement for industrial application.

In this work, UV-Vis spectra, FT-IR spectra, colour difference, yellowness index, and SEM micrographs were used to study the accelerated ageing behaviour of polyurethane films that exposed to UV radiation, O3 atmosphere, and UV/O3 integrated environment. During 200 hours of exposure in three different environment, the UV absorbance, the colour difference, the yellowness, and the absorption of-NH/-OH and-C=O bands in FT-IR spectra of the films increase gradually with increasing exposure time, respectively, and the films exposed to the three environments have different colour difference, yellowness index, UV-Vis spectra, and FT-IR spectra. The films are vulnerable to degradation and yellowing in the following environment order: O3 < UV < UV/O3. After exposure to UV radiation or O3 atmosphere, some degradation products and blisters are formed on the film surface. After exposure to UV/O3 integrated environment, there are strip blisters and micro-cracks on the film surface, and exists an obvious synergism between UV radiation and O3 atmosphere in accelerating the ageing of the polyurethane films.

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