Wettability and Bonding Quality of Paints on Ten Tropical Woods Species

Abstract

Surface properties of wood such as surface roughness, wettability and surface free energy (SFE) are important properties influencing further manufacturing process such as finishing or adhesive strength characteristics. The aim of this research was to determine surface properties such as surface roughness, SFE, and wettability of ten tropical woods and its effect to their bonding quality of paints. The woods tested in this study were fast-growing teak Biotrop variation, afrika, sungkai, mindi, merbau, durian, lamtoro, pulai, acacia and kempas. Wood surfaces were divided into unsanded and sanded using abrasive paper of 120 grits. SFE values were calculated based on the Rabel method. Wettability were measured by based on the contact angle between liquid paint and wood surface using sessile drop method and (S/G) model was used to evaluate the wettability of the surface coatings on the wood. Bonding quality of paints were measured using cross-cut test based on the ASTM 3359-02 standard. The results indicated that sanding decrease the surface roughness presented by Ra (arithmetical mean roughness), wettability and SFE of wood but produce higher equilibrium contact angle. Higher K-Value indicates higher wettability and bonding quality of paints. Afrika had greater wettability of acrylic and alkyd paints than the other wood species. Cross-cut tests showed that bonding quality of paints on ten wood species tend to decreased as the surface became smoother. The oil-based alkyd paint was more wettable and generates better bonding quality compared to the water-based acrylic paint.