Müller Uwe, Rätzsch Manfred, Schwanninger Manfred, Steiner Melanie, Zöbl Harald
Competence Centre for Wood Composites and Wood Chemistry (Wood K plus), St-Peter-Strasse 25, 4021 Linz, Austria.
J Photochem Photobiol B. 2003 Feb;69(2):97-105. doi: 10.1016/s1011-1344(02)00412-8.
The yellowing and IR-changes of spruce wood as a result of UV-irradiation were studied using two different types of xenon lamps (lambda>300 nm; I(o)=50 mW cm(-2) and lambda>280 nm; I(o)=17.5 mW cm(-2)). Changes in the IR spectra as well as the yellowing of the irradiated wood surfaces show the influence of UV light on the wood modules. The UV-irradiation (72 h; lambda>300 nm; I(o)=50 mW cm(-2)) decreased the lignin content on the surface by up to 20% of the original values. The colour difference of yellowing (deltaE) exhibited a systematic trend to higher values with increasing irradiation time. Our results show that the photoyellowing (UV-Vis detection) correlates very well with lignin degradation (IR detection). This result is in agreement with the quinone formation as the chromophoric reaction product of lignin decay. The degradation, yellowing, and oxidation kinetics differed only little using different light sources. The absorbed light intensity, which depends on wavelength, the intensity distribution of the light source and the absorption spectrum of lignin, influenced the degradation rate. Under the current experimental conditions, the absorption spectrum of lignin was the most important factor. Therefore, irradiation with lambda>280 nm is useful for rapidly monitoring the UV-degradation of wood
使用两种不同类型的氙灯（λ>300 nm；I₀=50 mW cm⁻²和λ>280 nm；I₀=17.5 mW cm⁻²）研究了云杉木因紫外线照射而变黄和红外变化的情况。红外光谱的变化以及被照射木材表面的变黄情况显示了紫外线对木材组件的影响。紫外线照射（72小时；λ>300 nm；I₀=50 mW cm⁻²）使表面木质素含量降低了高达原始值的20%。变黄的色差（ΔE）随着照射时间的增加呈现出系统性地向更高值发展的趋势。我们的结果表明，光致变黄（紫外-可见检测）与木质素降解（红外检测）具有很好的相关性。这一结果与作为木质素衰变发色反应产物的醌的形成相一致。使用不同光源时，降解、变黄和氧化动力学仅有微小差异。取决于波长、光源强度分布和木质素吸收光谱的吸收光强度影响了降解速率。在当前实验条件下，木质素的吸收光谱是最重要的因素。因此，用λ>280 nm进行照射有助于快速监测木材的紫外线降解情况
