Investigation on the effect of different methods of applying transparent coatings on adhesion strength of coating in wooden surfaces

In present study the effect of different methods of applying transparent coatings on adhesion strength of coating in Walnut (Juglans regia), Maple (Acer velutinum) and Pine (Pinus eldarica) species was investigated. For this purpose, samples prepared with dimension of 200×100×20 mm and 8% moisture content. Samples’ surfaces were sanded with 100, 120 and 180 grate sizes sandpaper significantly. Then after preparation wooden samples with sealer, their surfaces covered with clear and acid catalyzed transparent finish in separate process by using spray gun and applicator. Adhesion strength of coating was measured with Pull-Off method based on ASTM D4541 standard. Fluorescence microscopy test used for investigation coating penetration in spray gun and applicator method. Results showed that the method of applying coating on wooden surfaces has significantly affected adhesion strength, and highest adhesion strength between all samples, observed in samples coated with applicator method. Investigation of coating penetration indicated that applicator method had good penetration in wood substrate in comparison spray gun method. Highest differences in adhesion strength of coating between spray gun and applicator method were observed in Walnut and Maple’s samples. In general, highest adhesion strength of coating was found in Walnut samples covered with acid catalyzed transparent finish by using applicator method.