Study of the effect of protective on wood photo-degradation by colour measurements, FT-IR spectroscopy and hyperspectral imaging

The aim of this work is to investigate the effect of protective materials on poplar (Populus spp.) wood modifications as consequence of artificial photo-degradation in controlled environment. Starting from previous results [1-4], this study tried to understand what happens to wood surface under the protective layer. As protective materials, shellac, beeswax and Linfoil® were tested to compare traditional and novel products generally used for wood. The samples covered by these protective layers were artificially aged in Solar Box for 1064 hours. As comparison, also uncovered samples were tested. At chosen times, the samples were investigated by reflectance spectrophotometry, Fourier transform infrared spectroscopy and hyperspectral imaging in order to study the colour and chemical modification occurred to wood both covered and uncovered with the protective products. The obtained data were statistically elaborated in order to verify their significance. Colour measurements highlighted that the protective materials reduced the wood colour changes in respect to un-protected samples. FT-IR spectroscopy demonstrated that photo-degradation caused mainly lignin decomposition with the production of new chromophore groups on wood surface. Also in this case un-covered wood underwent greater modifications in respect to protected one. Hyperspectral imaging in the SWIR range (1000-2500 nm), coupled with chemometric methods, clearly showed the variation between the spectral behavior of poplar wood for ageing time 0 and 1064 hours, with different protective layers. It is interesting to note that protective materials have a partial effect on wood photo-degradation by little reducing the changes. Such results can contribute to evaluate the effect of protective materials on wood during sun exposure.