Effects of plasma treatment and sanding process on surface roughness of wood veneers

Abstract

An ideal veneer surface is crucial for good panel properties in plywood manufacturing. The aim of this study was to compare plasma treatments and sanding (mechanical) processes with respect to the surface roughness of veneers. Rotary-cut veneers with a thickness of 2 mm from Scots pine (Pinus sylvestris) logs were used as material. After rotary peeling, veneer sheets were dried at 110 °C in a veneer dryer. Veneer sheets were divided into 4 main groups. The surfaces of the control veneer sheets were left untreated. Two different grits of sandpaper, 80 and 180, were used for sanding the surfaces of veneers. Plasma treatment was applied to the last veneer group with 3 different gases (oxygen, nitrogen, and ammonia) and 3 different plasma times (1 min, 5 min, and 15 min). The Mitutoyo Surftest SJ-301 instrument was used to determine surface roughness of samples. Average roughness (Ra), mean peak-to-valley height (Rz), and maximum roughness (Rmax) parameters were measured to evaluate the surface roughness of the samples based on DIN 4768. It was found that the smoothest veneer surfaces were obtained with the sanding processes. Surface roughness values (Rz) of veneer sheets sanded with 180 grit sandpaper were lower than those of veneers sanded with 80 grit sandpaper. Compared with the plasma treatment in terms of surface roughness, plasma-treated veneers had higher Rz values. It was also determined that Rz values were the lowest in the veneers treated with nitrogen plasma. Additionally, the surface roughness values of Scots pine veneers treated with ammonia plasma were a little higher than those of veneer sheets treated with oxygen plasma. The effect of plasma treatment time on surface roughness was not found to be statistically significant.