This contribution shows the results from the study of the behaviour of Ayous (Triplochiton scleroxylon K. Shum) wood, untreated and industrially heat-treated, with the subsequent application of a mono-component polyurethane coating. The coating was applied by brush and spray, according to the indications supplied in the technical data sheet, to verify the most effective modality. The samples were artificially aged under simulated solar irradiation to verify the behaviour over time of the protective and of the unprotected wood, untreated and heat-treated. To investigate the behaviour of the specimens, micro-hardness, wettability, wearing, colour and roughness were measured and compared before and after artificial ageing in the SolarBox chamber.
The obtained data highlighted that the coating improve the surface characteristics of Ayous wood by increasing the hydrophobicity, the homogeneity of the surfaces, the micro-hardness, and, the resistance to wearing. Concerning the colour, the effect of coating acts mainly on the untreated wood by causing a little increase of b* parameter (little yellowing of wood surface).
The ageing process under simulated solar radiation causes some relevant changes in the surface properties, generally getting worse the wood surface characteristics especially in the uncoated samples. Specifically, hydrophobicity decreases significantly in the heat-treated uncoated samples, whereas in the same samples but coated the hydrophobicity is maintained thanks to the presence of the polyurethane layer. Micro-hardness undergoes little decrease in all samples, because of ageing. The main one is observed in the control samples, i.e. untreated thermally and uncoated. The effect of coating is particularly relevant on the wearing resistance. In fact, samples with coatings are much more resistant to wearing in respect to uncoated ones and they also suffer less colour changes. This result demonstrates the good performance of the polyurethane coating and its effectiveness in the protection of wood exposed to outdoor conditions.
