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This paper presents the research of influence of wood surface preparation on the wetting ability of polyurethane coatings, by the method of contact angle. The samples were made of two species of Paulownia (Paulownia elongata and Paulownia fortunei). All the samples were processed by planing (molding). After molding, the samples were arranged in groups and sanded. In relation with wood grain direction, each group had a particular system of sanding, based on the numbering of sanding paper, program of displacement of sanding papers with different numbering and the direction of sanding. The quality of wood surface after sanding was expressed by the values of roughness parameters in the system 'M': Ra, Rz, Rv, Rp and Rt. The contact angle was measured using transparent polyurethane (PU) coating and distilled water. The influence of the system of sanding on the values of contact angle was analyzed by roughness parameter Ra.

This paper presents the research of influence of sanding, staining and the use of polyurethane and acrylic coating on the adhesion, scratch resistance and abrasion resistance of the coating. Objective was to determine the most important mechanical properties of lacquered surfaces, considering the application of Paulownia elongata and Paulownia fortunei, by using different systems of surface finishing. Cross cut method was used for measurement of adhesion. More accurate view of coating adhesion was obtained by measuring the scratch resistance. Abrasion resistance was tested by the method of free falling of abrasive particles. The applied system of sanding had no effect on the examined mechanical properties. Stained samples lacquered with PU coating showed better adhesion to the non-stained samples. Impact of staining on scratch resistance is not established. Stained samples showed greater resistance to abrasion for both wood species. Samples lacquered with PU coating showed the higher values of mechanical properties compared with samples lacquered with UV acrylic coating. Application of PU coating for surface finishing of Paulownia elongata and Paulownia fortunei is more adequate than the application of UV acrylic coatings, from the point of scratch resistance and abrasion resistance.