Effects of extractives on the physical and mechanical properties of clear coating varnishes on the wooden furniture surfaces

The main goal of present work was to study the effect of extractives of ironwood (Zelko carpinofolia) on the adhesion strength and surface wettability using two different clear varnish coatings namely, polyester and polyurethane (urethane alkyd). Removal of extractive materials was followed Tappi Test Methods using hot water, acetone, and ethanol. Pull-off adhesion and dynamic absorption test were used to assess adhesion and performance of the two clear varnish coatings. According to the research results, it was found that the removal of extractives had a significant effect on increasing of the pull-off adhesion and wettability. Varnish coating significantly reduced the water diffusibility of wood within a given time. However, the level of repellence was slightly higher for heartwood compared with sapwood. Based on the results of this study, it can be pointed out that the highest adhesion was obtained by two-part polyurethane varnish