How does surfactant affect the hydrophobicity of wax-coated wood?

Abstract

To investigate the role of surfactants in affecting the hydrophobicity of wax-coated wood, six groups of wax emulsions with different surfactant contents (0, 5%, 10%, 20%, 40%, and 60%) were prepared by ultrasonication to modify wood. The hydrophobicity and moisture buffering capacity of the wax-coated wood as well as the mechanical stability of wax coating on wood surface were characterized by dynamic contact angle measurement, moisture buffering experiment, sandpaper abrasion test, and simulated rain test. Combined with the analysis of the surface microstructure and chemical composition by SEM and XPS, the relationship between the surfactant content and the properties of the wax-coated wood was clarified. The results indicate that the surfactants not only reduced the long-term hydrophobicity of wax-coated wood, but also improved the mechanical stability of wax coating. As the content of surfactants increased from 5% to 60%, the water contact angle decreased from 145.7° to 135.5°. The droplets spread quickly on the wood surface, and the decrease in contact angle after the rain test reduced from 4.8% to 1.3%. However, the effect of surfactant content on the moisture buffering capacity of the wax-coated wood first increased and then decreased. The change in the properties of wax-coated wood is directly related to the change in the surface micro/nano rough structure and chemical composition caused by the surfactant content.