Effect of Resin Content on the Surface Wettability of Engineering Bamboo Scrimbers

Bamboo scrimber refers to a lignocellulosic structural material, which is usually attacked by water, ultraviolet radiation and fungus. Surface coating is an effective way to protect it, and its coating properties depend on surface wettability. In this study, the surface wettability of bamboo scrimbers with varying resin content was investigated via the comprehensive analysis of surface roughness, surface contact angle, surface free energy, surface chemical composition and coating properties. The resultant scrimbers had a similar profile with low roughness. Their surface was hydrophilic, but the hydrophilicity decreased with the increase in resin content. High resin content gave rise to low total free energy, in which the Lifshitz–van der Waals component was dominant and it decreased with the increasing resin content. Meanwhile, the ratio of the electron-accepting component to the electron-donating component becomes higher. This was due to the decreasing hydrophilic groups (e.g., -OH and -COOH groups) and the increasing oxygen-free groups (e.g., C-H and -CH2 groups) on the scrimber surface. The resin content affected the adhesion by decreasing the surface wettability, but the coating adhesion still reached the level of 2 for all bamboo scrimbers. The results will provide a theoretical reference for the surface coating of bamboo scrimbers in the structural application for good coating durability.