ONLINE ISSN 2069-7430 ISSN-L 1841-4737 PRO LIGNO Vol. 13 N° 4 2017 www.proligno.ro pp. 308-315 308 EFFECT OF NANOPARTICLES ON THE WOOD-WATER RELATIONS Miklós BAK University of Sopron, Simonyi Károly Faculty of Engineering, Wood Science and Applied Arts Bajcsy-Zsilinszky u. 4, 9400 Sopron, Hungary Tel: 0036 518 187, Fax: 0036 518 647, E-mail: bak.miklos@uni-sopron.hu Róbert NÉMETH University of Sopron, Simonyi Károly Faculty of Engineering, Wood Science and Applied Arts Bajcsy-Zsilinszky u. 4, 9400 Sopron, Hungary Tel: 0036 518 152, Fax: 0036 518 647, E-mail: nemeth.robert@uni-sopron.hu Ferenc MOLNÁR University of Sopron, Simonyi Károly Faculty of Engineering, Wood Science and Applied Arts Bajcsy-Zsilinszky u. 4, 9400 Sopron, Hungary Tel: 0036 518 187, Fax: 0036 518 647, E-mail: ferimoln@gmail.com Abstract: Results of an experimental research about the effect of different titanate nanoparticles on the wood- water relations are shown in this paper. Different wood species were used for the experiments. Treatment of wood with the nanoparticles was performed by impregnation method. Different concentrations of nanoparticles were used. Investigated properties after treatment were shrinking/swelling coefficient, equilibrium moisture content (EMC), water uptake and moisture permeability. Beside these, colour change (CIELab) and mechanical properties (compression strength and surface hardness) were investigated as well. Overall, we can state according to our investigations so far, that the impregnation with nanoparticles was successful. Shrinking and swelling properties decreased remarkably in case of all the four investigated wood species. As a side effect of the treatments, a slight colour change could be observed as well. No effect on the mechanical properties could be found as a result of the treatment. Key words: nanoparticles; shrinking/swelling; water uptake; EMC; colour change. INTRODUCTION Wood is in contact with air humidity in all utilization fields. In many cases, wood elements are used as space border. Furthermore, during the processing wood undergoes a drying process. In these cases, it is important to know the sorption and diffusion properties of the wood to be able to understand the expected moisture transport processes in the wood during utilization. Diffusion properties of wood are strongly dependent on wood species and anatomical directions, but climatic conditions and sample size are also important factors (Jalaludin et al. 2010, Pfriem et al. 2010). Moisture uptake in wood occurs through diffusion and capillary flow. Below the fibre saturation point moisture can transported as water vapour in the lumens, or as bound water in the cell walls with the diffusion. In this phase of moisture movement can be modelled successfully with a diffusion front moving through the wood, causing smooth moisture content gradients in the different cardinal direc-tions (Droin- Josserand et al. 1988). However, in reality the moisture transport in wood is suspected to be more difficult (Absetz and Koponen 1997). The characteristic of modified woods’ sorption behaviour usually includes slower reaction to relative humidity changes than natural wood; therefore, the moisture uptake is lower and slower (Hill 2006). Changes in wood-water relations due to modification are also strongly influenced, however, by the wood species. The phenomenon of modification is even more complicated, as usually all of the treatment parameters have influence on the wood-water relations (WPG, concentrations, temperature, duration, etc.). The moisture uptake rate can therefore be different after various treatments. The utilization of nanoparticles to improve the properties of wood is not widely investigated recently. On the other hand, a lot of promising results were achieved with the use of nanoparticles in relation to the mechanical, combustion, hydrophobic and some other properties of different polymers, papers or textiles (Wang et al. 2006; Csóka et al. 2007; Chen and Yan 2012; Nypelö et al. 2012; Jiang et al. 2011; Sun et al. 2007; Textor and Mahltig 2010). Recently there is only limited information available about the utilization of nanoparticles to improve the wood properties, but all results are positive. With the use of different nanoparticles the moisture uptake is reducible, UV-protection, mechanical properties and durability is improvable (Rassam et al. 2012; Niemz et al. 2010; Yu et al. 2011; Mahltig et al. 2008). In some cases, fire resistance could be improved as well (Shabir Mahr et al. 2012). According to the careful examination of the