Comparison of exterior performance of two coating systems based polyurethane applied Pinus sylvestris L. and Picea orientalis L. wood
Ö Özgenç, Û Cafer Yıldız
Some surface changes in sapwood and heartwood of two species before applying clear-coating were characterized after accelerated weathering time. Wood specimens covered with two types polyurethane (PU) films were also observed in accelerated weathering exposure. In this study, changes on the wood surface were compared of between wood specimens covered with two types polyurethane (PU) films after irradiation. The study was carried out on sapwoods and heartwoods two wood species; Fagus sylvatica L., Pinus sylvestris L. The artificial weathering experiment was performed by cycles of 2 hours UV-light irradiation followed by water spray for 18 minutes according to ASTM G 53-96. The surface changes of the weathered sapwood and heartwood samples applied clear-coating were characterized by surface roughness and color measurements. Color measurements were made by a with a Konica Minolta CM-600d (Canada) at several intervals (0-24-72-168-240-336-408-504-600-672 hours) in artificial weathering of treated and untreated wood. Additionally surface roughness was measured on the surface of all wood samples, unweathered and after 672 hours of weathering by a Mitutoyo Surfest SJ-301 instrument. According to the results, the scots pine and spruce sapwood samples provided better protection color changes than the scots pine and spruce heartwood samples showed lower color changes. The highest increasing surface roughness values were on the wood samples applied 2.system clear-coating (Y) by reason of the wood surfaces contain several checks, splits and cracks caused by weathering. The wood surface applied 1.system clear-coating (X) showed that no high cracks and substantially surface properties changes were observed significantly due to weathering.