The role of olive leaf extract and nanoparticles incorporation in polyacrylate coating structure on surface properties of heat treated wood during natural weathering

Document Type : Research Paper


1 PhD Student in Wood and Paper Sciences

2 Assoc., Prof., Department of wood and paper science, Faculty of Natural Resources, University of Tarbiat Modares, Noor, I.R. Iran

3 Assoc., Prof., Department of Paint and Coating, Faculty of Polymer & Color Engineering, University of Amirkabir, Tehran, I.R. Iran

4 Prof. , Department of Wood Science and Technology, Faculty of Biotechnical, University of Ljubljana, Ljubljana, Slovenia


Wood coating with clear coats such as polyacrylate have a short service life since solar radiations pass through the coat and cause subsequent discoloration of wood surface. These phenomena can be decreased by using suitable UV absorbants in the coats. Therefore, in this research, olive leaf extract in combination with nano-particles of titanium dioxide (TiO2) and zinc oxide (ZnO) were added to the polyacrylate coat as the substrate to study the possible effects of different formulated coats on surface properties of the thermally modified wood after exposure to the natural weathering for a long period. The surface properties of the coated wood such as color change, surface roughness and wettability of the coated wood were studied during the weathering period. The microscopy was carried out on the coated wood to evaluate any morphological changes of wood surface as well as any mold growth. The results showed less color changes in the coated thermally modified wood. Also, surface roughness increased due to the weathering in all coats. However, roughness increased in all samples including control and treated ones, showing the highest roughness in uncoated samples. The result of contact angle showed that the polyacrylate coated samples kept their low wettability during the weathering periods. However, the wettability was increased in the control samples. It could also be concluded that olive leaf extract caused less mold growth and less color changes due to its anti-oxidant and bioresistance properties.


[1]. Temiz, A., Yildiz,U., Aydin, I., Eikenes, M., Alfredsen, G., Çolakoglü, G. (2005). Surface roughness and color characteristics of wood treated with preservatives after accelerated weathering test. Journal of Applied Surface Science, 250: 35-42.
[2]. George, B., Suttie, E., Merlin, A., Deglise, X. (2005). Photo degradation and photostabilisation of wood the state of the art. Polymer Degradation and Stability, 88: 268-274.
[3]. Dawson, B.S.W., Singh, A.P., Kroese, H.W., Schwitzer, M.A. S., Gallagher, S.J., Riddiough, S. Wu. (2008). Enhancing exterior performance of clear coatings through photostabilisation of wooden surfaces. Part 2: coating and weathering performance. Journal of Coatings Technology and Research, 5: 207–219.
[4]. Evans, P.D., Hasse, J.G., Shakri, A., Seman, B.M., Kiguchi, M. (2015). The search for durable exterior clear coatings for wood. Journal of Coatings, 5: 830-864.
[5]. Schuh, A.E. Theuerer, H.C. (1937). Effect of film thickness on physical properties and exposure behavior. Industrial and Engineering Chemistry, 29: 182-189.
[6]. Aloui, F., Ahajji, A., Irmouli, Y., George, B., Charrier, B., Merlin, A. (2007). Inorganic UV absorbers for the photostabilisation of wood-clear coating systems: comparison with organic UV absorbers. Applied Surface Science, 253: 3737–3745.
[7]. Hill, C.A.S. (2006). Wood modification: chemical, thermal and other processes, Belgium.
[8]. Cao, Y., Jiang, J., Lu, J., Huang, R., Jiang, J.I., Wu, Y. (2012). Color change of chinese fir through steam-heat treatment. BioResources, 7 (3):2809-2819.
[9]. Miklečic, J., Lučic Blagojevič, S., Petrič, M., Jirouš-Rajkovi, V. (2015). Influence of TiO2 and ZnO nanoparticles on properties of waterborne polyacrylate coating exposed to outdoor conditions. Progress in Organic Coatings, 89: 67-74.
[10]. Militz, H., (2002). Thermal treatment of wood. In: European Process and Their Background, the International Research Group on Wood Preservation. IRG:/WP 02-40241, Cardiff, Wales.
[11]. Sow, C., Riedl, B., Blanchet, P. (2010). UV-waterborne polyurethane-acrylate nano composite coatings containing alumina and silica nanoparticles for wood: mechanical, optical, and thermal properties assessment. Journal of Coat Technology Research, 8: 211–221.
[12]. Standard Practice for Atmospheric Environmental Exposure Testing of Nonmetallic Materials, Annual Book of ASTM Standard, G7-97, 2003.
[13]. Standard Practice for Calculation of Color Tolerances and Color Differences from Instrumentally Measured Color Coordinates, Annual Book of ASTM Standard, D2224-02, 2016
[14].Standard Test Method for Evaluating Degree of Surface Disfigurement of Paint Films by Microbial (Fungal or Algal) Growth or Soil and Dirt Accumulation.Annual Book of ASTM Standard, D3274-95.
[15]. Saha, S. Kocaefe, D. Boluk, Y. Pichette, A. (2011). Enhancing exterior durability of Jack Pine by photo-stabilization of acrylic polyurethane coating using bark extract. Part 1: Effect of UV on color change and ATR–FT-IR analysis. Progress in Organic Coatings, 70: 376-382.
[16]. Yildiz, S., Yildiz, U., Cafer, T., Eylem, D. (2011). The effects of natural weathering on the properties of heat-treated alder wood. Journal of Bio resources, 6: 2504- 2521.
[17]. Pandey, K. K., Srinivas, K. (2015). Performance of polyurethane coatings on acetylated and benzoylated rubber wood. European Journal Wood Product, 73: 111-120.
[18]. Saha, S., Kocaefea, D., Boluk, Y., Pichettea, A. (2013). Surface degradation of CeO2 stabilized acrylic polyurethane coated thermally treated jack pine during accelerated weathering. Applied Surface Science, 276: 86-94.
[19]. Shi, L. E., Li, Z. H., Zheng, W., Zhao,Y. F., Jin, Y. F., Tang, Z.-X. (2014). Synthesis, antibacterial activity, antibacterial mechanism and food applications of ZnO nanoparticles. Food Additives and Contaminates, 31: 173-186.
[20]. Korukluoglu, M., Sahan, Y., Yigit, A. (2008). Antifungal properties of olive leaf extracts and their phenolic compounds. Journal of Food. Safety, 28: 76-87.