engleski

Characterization of wood surface degradation using activation spectra approach

To attain and emphasize natural aesthetic advantages of both native and modified wood, its surface should be protected with transparent or semi transparent finishing systems whose durability should be improved. Particularly the identification of wavelengths of ultraviolet and visible light during weathering that cause the changes in colour and micromechanical properties of wood, was chosen to be the principal interest in this research. Batches of thin strips of fir wood, assembled in packs of matching three strips (thus forming a 240 m thick surface layer), were exposed to irradiation behind a set of cut-on glass filters that transmitted selected regions of the UV and visible spectrum. Disassembling the pack of three strips after withdrawals from exposure enabled monitoring of the relevant changes in each particular strip i.e. in the depth of the wood surface during weathering. Depth profiles of colour and microtensile changes develop in time and are specific to observed properties. Relatively narrow waveband of most active wavelengths is causing greatest proportion of all recorded damages (360 – 435 nm). However, visible light of wavelengths up to 510 nm was shown to contribute significantly to surface damaging. Efficient protection of wood from light would demand screening not only UV light, but also some violet and blue light wavebands. The light protection must be efficient over prolonged periods of time in order to secure long-lasting stability of wood surface.

wood; photodegradation; spectral sensitivity; activation spectra

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