It is well known that the natural wood surfaces, finished with transparent coatings has a shorter service life and aesthetic view comparing to the wood surfaces, coated with stain. Transparent coatings, used for outdoors, fail within a short time, because the solar ultraviolet (UV) radiation can readily penetrate through the coatings and reach the wood underneath, causing the degradation of the cell walls as well as the organic coating by itself. One of the solution to change the performance of the transparent coating on wood can be enhanced using inorganic metal oxide nano additives. The main objective of this research was to reduce UV transmittance through water-based clear acrylic (AK) wood coating, using cerium dioxide (CeO2) nanoparticles. Tangential and radial cut planed pine (Pinus sylvestris L.) wood samples were impregnated against biological pests and finished with AK varnish containing five different concentrations of the CeO2 nanoparticles (up to 7 %). Coated wood samples were exposed for ten months in natural weathering conditions in Kaunas, Lithuania. The colour change of the coated wood samples were evaluated accordingly to CIE-L*a*b* system. During the natural weathering, moisture and visual change of wood samples were observed. The adhesion strength of the coating to the surface of wood was examined before and after 5 months of the natural aging. In order to determine the change of UV absorption of the coatings, the UV-VIS spectroscopy was performed. It was noticed, that increasing the concentration of CeO2 nanoparticles in the coating, the absorption of UV radiation of the coatings also increases. However, increased CeO2 concentration caused yellowing of the coatings and the lightness parameter ΔL started to decrease. During the time of exposure, coatings with CeO2 nanoparticles had a raising trend of redness (+Δa) and yellowness (+Δb). Despite the fact that CeO2 gives yellow undertone for coating, it keeps durability and UV resistance.
Keywords: pine wood, acrylic coating, CeO2 nanoparticles, natural weathering, UV resistance
Authors
Uselė U.
Department of Materials Engineering, Kaunas University of Technology, Kaunas
Ukvalbergienė K.
Department of Materials Engineering, Kaunas University of Technology, Kaunas
Lazėnė J.
Department of Materials Engineering, Kaunas University of Technology, Kaunas
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