Infrared Studies of Wood Weathering. Part I: Softwoods

Infrared spectra, in the diffuse reflectance mode, are presented for three common softwoods (Western redcedar, southern pine, and Douglas fir) that have been subjected to a variety of artificial weathering conditions. The surface spectra of the three unweathered woods have distinctly different characteristic features, but after 2400 hours of full artificial weathering the surface features are virtually identical and correspond closely with those of the cellulosic polymer components. Weathering with light alone has a less pronounced effect on the wood surfaces, whereas weathering with water alone has virtually no effect in comparison to the result of both light and water used in conjunction. A photochemically induced reaction pathway for the weathering process, consistent with the experimental findings, is discussed.