Natural weathering of sixteen wood species: Changes on surface properties

Abstract

In this study, natural weathering behavior of sixteen different wood species was investigated under the same conditions in order to clarify the resistance against outdoor degrading agents regarding wood color, gloss, surface roughness and surface chemistry. For this purpose, American walnut, ash, cherry, oak, maple, teak, mazel, beli, limba, anigre, tulip, sapele, walnut, eucalyptus, beech and pine samples were exposed to weathering agents on above ground test equipment for a year in Bursa, Turkey, and 36 periodic measurements were carried out from the surfaces during the exposure period. The results showed that the darkest and the greatest color change were found on the surfaces of pine, maple and tulip samples while the least color change was observed on walnut, A. walnut and oak samples. The surface roughness, crack formations and degradation of surface components increased with the increase in exposure period. Gloss property had a tendency to increase on some species such as teak, sapele, walnut, A. walnut, limba and beli while the others lost the gloss, and had a paler surface than the initial stage. In accordance with the color and roughness measurements, FTIR spectra proved that lignin degradation continued on the exposed surfaces during 3 months of natural weathering for all species. Correlation analysis showed that wood species with high density had more stability against color changes. However the roughness and gloss showed nonsignificant correlation between density of samples.