Boron-Based Mildew Preventive and Ultraviolet Absorbent Modification of Waterborne Polyurethane Coatings on Laminated Bamboo

In order to improve the outdoor exposure performance of laminated bamboo, boric acid/borax and UV absorbents, including triazole (UV1130), nano–TiO2, and nano–SiO2, were used to modify waterborne polyurethane (WPU) coatings, respectively. The physical and chemical properties of the coatings with and without modification were evaluated by adhesion strength, contact angle, wear, and temperature-resistance experiments. The antimildew properties of the coatings were evaluated by the bacteriostatic zone method, and the pyrolysis characteristics were investigated through TG–FTIR analysis. The results showed that, when compared with the unmodified WPU coating, the coatings with different modifications had stronger wear resistance; the mass loss of the best C4 coating was only 0.0078 g, which was 0.0203 g less than that of the unmodified C0 coating. However, when compared to the unmodified coating, the wettability of the modified coating increased to different degrees, and the contact angle of the C4 coating with the most obvious effect was only 36.50°. During the curing process of the modified coatings, the UV absorbents and boric acid/borax would interact with the C–N, C–O, and C=O bonds in the coating and change the molecular structure of the WPU. The thermal stability of the coatings with different modifications was enhanced. The best result, a 76.27% weight loss, was observed in the modified coating with boric acid/borax and 1.0% nano–TiO2. Different modified coatings had a certain degree of control effect on Aspergillus Niger, and the reason for this was considered the combined effect of boric acid/borax and UV absorbents.