Effect of Process Conditions on Waterborne Wood Coating Performance Applied by Dipping

Abstract

Bio-based commercial coating systems are still not widely used to protect wooden elements and constructions used outdoors. In some cases, this is due to insufficient information about the technology and conditions of the film formation process. The present research aims to determine the influence of the process conditions on the properties of a coating applied by dipping on spruce, beech, and beech plywood surfaces. A waterborne one component bio-based varnish system was used. The study researched the following parameters: the amount of varnish applied, varnish penetration into the wood, and roughness of the surfaces after coating and drying. The variables investigated were the dipping orientation to the grain direction in the wood specimens, the wood surface treatment before coating, and the dipping time. Polynomial regression models were derived. It was established that with a single dip for 5 seconds, surfaces with a good appearance were obtained, but the varnish amount exceeded the norms recommended by the manufacturer several times. When axially dipping spruce and beech specimens, the varnish amount was the least when the surfaces were sanded with P150 grit-sized sandpaper. For the plywood specimens, the treatment had no effect. In tangential dipping, the characteristics of the wood species determined the varnish amount and the roughness parameter values. The sanding process had a more significant influence than the sandpaper grit size. The penetration was affected by the wood species characteristics, the wood surface treatment before coating, and the dipping time. In axial dipping, the penetration was times greater than in tangential dipping.