In this study, the effect of UV irradiation on some technological properties of three different polyurethane varnishes coated plywood panels produced from Scots pine (Pinus sylvestris L.) and Maritime pine (Pinus pinaster L.) veneers manuactured and dried at different temperatures was studied. Accordingly, 32°C log peeling temperature and three different veneer drying temperatures (110, 140 and 160°C) were chosen. Five-ply-plywood panels with 10 mm thick were manufactured by using melamine-urea formaldehyde glue resin with 54% solid content. UV irradiation process, bonding strength, color measurement and surface roughness tests were conducted on plywood panels according to ASTM G53, EN 314, ISO 7724-2 and DIN 4768 standards, respectively. Polyurethane varnish (ingredients: 37% polyurethane, 63% water) coated plywood panels manufactured from Maritime pine (Pinus pinaster L.) veneers dried at 160°C showed the lowest color change values. The best protection on bonding strength was obtained from the polyurethane varnish (ingredients: 60% polyurethane, 11% xylene, 9% ethyl benzene, 20% 3-methoxybutyl acetate, 1% toluene-2,4-disocianate ) coated plywood panels manufactured from Scots pine (Pinus sylvestris L.) veneers dried at 110°C against UV irradiation.

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