Interactions of a waterborne coating with plasma pre-treated densified beech wood

Abstract

Densification is a modification technique usually applied to low-density wood species to improve the mechanical properties of the wood. However, densification impairs the wettability abilities of the wood surface and has a negative effect on some properties of the coated substrate. In this study, various physical properties of non-densified and densified common beech (Fagus sylvatica L.) wood were investigated. The densification caused the changes in wood density, moisture content, chemical properties and colour. With the aim of overcoming the negative influence of densification on the surface properties and coatability of wood, plasma pre-treatment was performed. Although the densification impaired the wettability of the wood surface, treatment with plasma increased the surface free energy of both non-densified and densified wood. The improved hydrophilicity of the wood after plasma pre-treatment was also reflected in the improved interactions with the liquid coating. Scanning electron microscope analysis of the coated wood surfaces showed reduced penetration of the coating in densified structure of wood, which negatively affected the adhesion of the coating films. However, the negative effect of densification on the coating adhesion was successfully mitigated by pre-treating the wood with plasma. In conclusion, it was shown that plasma treatment is a promising surface modification technique to achieve a better interaction between densified wood and waterborne coating.