Performance testing of modified waterborne polyurethane coating applied on laminated bamboo

The effects of different UV absorbents and preservatives on the weatherability of modified waterborne polyurethane (WPU) printed laminated bamboo were investigated. Three types of UV absorbents including 2-hydroxy-4-n-octoxy-benzophenone (UV-531), 2-(2 H-benzotriazol-2-yl)-4-(1,1,3,3 tetramethylbutyl) phenol (UV-329), and nano-TiO2, and four types of preservatives including boric acid (BA), borax (BX), ammonium polyphosphate (APP), and disodium octaborate tetrahydrate (DOT) were selected to modify WPU coatings. The printed laminated bamboo was tested to evaluate the coating physical and chemical properties and dimensional stability. Thirteen coating types were tested. The results showed that the 0 (20% WPU), 5 (UV-531-BA/BX), 6 (UV-531-BA/BX/APP), 7 (UV-531-BA/BX/DOT), 8 (UV-531-BA/BX/APP/DOT), and 9 (nano-TiO2/BA/BX) samples performed well in adhesion, abrasion resistance, hardness, and temperature denaturation. Fourier transform infrared (FT-IR) spectra analyses and dimensional stability analysis were carried out on the six kinds of coatings screened out. FT-IR spectra analyses showed the successful introduction of UV light absorbers and flame retardants, whereas test results of hygroscopicity showed that the coated test material improved the dimensional stability performance. Test material 8(UV-531-BA/BX/APP/DOT) had the best dimensional stability performance.