Enhancement of bamboo surface photostability by application of clear coatings containing a combination of organic/inorganic UV absorbers

Benzotriazole (BTZ), benzophenone (BP), nano-TiO2 (NTiO2), and nano-ZnO (NZnO) are potential components of UV protection coatings due to being UV light absorbers. Herein, the UV-protective effects of four acrylic coatings containing individual organic and inorganic UV light absorbers and another four coatings containing both types of absorbers were determined by employing accelerated bamboo aging tests. Although organic absorbers decomposed during aging, their degradation rate decreased in the presence of inorganic absorbers. Moreover, individual organic absorbers were better suited for color stabilization than inorganic ones, with the best bamboo surface photostability enhancement achieved by BTZ-containing coatings (BTZ, BTZ-NZnO, and BTZ-NTiO2). Furthermore, strong synergistic effects were detected for BTZ-NZnO and BTZ-NTiO2, whereas an antagonistic effect was observed for BP-NTiO2 and BP-NZnO. Thus, combinations of organic and inorganic UV light absorbers efficiently inhibited the degradation of the former, with the performance of clear coatings determined by the type of the organic absorber.