Rheological Approach to the Capillary Penetration of Coating Into Wood

By Mari de Meijer, Barend van de Velde, Militz

The penetration of water- and solventborne bind-ers into the capillaries of wood was studied as a function of the viscosity, surface tension, and capillary pressure according to the Washburn equation. During the penetration, water is selectively removed from the coating, which causes a strong increase in viscosity that limits the penetration.

Waterborne dispersions and emulsions showed a rapid increase in viscosity with increasing solid matter content. Surface tension of the binder and the adsorption of surfactants to the wood have an additional influence on the maximum penetration.