Abstract
Thermal modification of wood has gained its niche in the production of materials that are mainly used for outdoor applications, where the stability of aesthetic appearances is very important. In the present research, spectral sensitivity to discoloration of thermally modified (TM) aspen wood was assessed and, based on these results, the possibility to delay discoloration due to weathering by non-film forming coating containing transparent iron oxides in the formulation was studied. The effect of including organic light stabilizers (UVA and HALS) in coatings as well as pretreatment with lignin stabilizer (HALS) was evaluated. Artificial and outdoor weathering was used for testing the efficiency of different coating formulations on TM wood discoloration. For color measurements and discoloration assessment, the CIELAB color model was used. Significant differences between the spectral sensitivity of unmodified and TM wood was observed by implying that different strategies could be effective for their photostabilization. From the studied concepts, the inclusion of the transparent red iron oxide into the base formulation of the non-film forming coating was found to be the most effective approach for enhancing TM wood photostability against discoloration due to weathering.
Highlights
Thermal treatment has been found to be a feasible modification method for increasing wood hydrophobicity, biological durability, and dimensional stability [1,2,3]
thermally modified (TM) wood spectral sensitivity to photodiscoloration was evaluated since such data are important for the designing of effective protective coatings but hardly any information is reported in the literature
One of the consequences of wood subjection to high temperature treatment is the changed composition of its chromophores, imparting wood the characteristic brown color (Figure 1), which is a result of intense visible light absorption
Summary
Thermal treatment has been found to be a feasible modification method for increasing wood hydrophobicity, biological durability, and dimensional stability [1,2,3]. The most widely used UV-absorbing inorganic additives are zinc oxide (ZnO) and titanium dioxide (TiO2 ) due to their high absorption of radiation mainly in the UV range, providing good retention of the natural wood color after application of coating [15,20,21]. Another available inorganic UVA are iron oxides. TM wood spectral sensitivity to photodiscoloration was evaluated since such data are important for the designing of effective protective coatings but hardly any information is reported in the literature Such knowledge provides the possibility to tailor coating formulation matching TM wood peculiarities. European aspen (Populus tremula L.) was used for the experiment as it is a fast-growing species with inadequate commercial value and thermal modification could be considered a potential way to increase its market share
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
