Various heat treatment processes for wood modification have been developed in Europe, resulting in increase of dimensional stability and resistance to biological attack of wood. However, resistance of thermally modified wood against photodegradation remains almost the same and surface finishing of modified wood is still needed. The aim of research was to study compatibility of nine different coatings with thermally modified Scotch pine wood (Pinus sylvestris L.). One-year natural weathering test showed that the durability of coatings was increased when applied on thermally modified wood. This finding was explained by the changed characteristics of thermally modified wood, which, in comparison with unmodified wood, showed lower equilibrium moisture content, lower liquid water permeability, increased dimensional stability, better UV stability and resistance to blue stain fungi. Better wetting of thermally modified wood with coatings and deeper penetration of coatings into modified wood were observed as well. It was also established that after one year of weathering the systems with waterborne coatings showed inferior performance compared to the systems with solventborne finishes, exhibited by film cracking and moulding of the whole system. The addition of photostabilizers into the transparent coating formulation resulted in a decrease of flaking and cracking of the coating. Compared to the transparent systems, the pigmented systems proved as superior. The results of better performance of the systems thermally modified wood - coating compared to the systems unmodified wood - coating showed that adjustment of existing commercial coatings for use on thermally modified wood is not needed.
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