FT-IR STUDIES OF WEATHERING EFFECTS IN WESTERN REDCEDAR AND SOUTHERN PINE

Diffuse reflectance infrared spectroscopy has been used to monitor the changes in functional groups on the surface of two woods (western red cedar and southern pine) when they are subjected to a range of artific ial weathering conditions. The effects of light only, water only, and light plus water have been studied for a variety of exposure times. Th e changes in the chemical composition of the wood caused by light plus water is considerably greater than that caused by light only, whereas water alone causes no permanent chemical changes. The effects of some of these weathering conditions have been investigated for wood protec ted by varnish, for earlywood and latewood and for tangentially, radia lly, and cross-sectionally cut wood samples. The application of two co ats of varnish was found to considerably reduce the weathering effects caused by UV radiation; earlywood undergoes light-only degradation fa ster than late wood; and the effect of weathering was found to be grea test for cross-sectional cut samples and least for radially cut sample s. The weathering profile with depth of penetration has been studied i n some detail for western redcedar, and our results show that, after 3 00 h of continual artificial weathering, the chemical changes are conf ined to the first 200 mum.