WoodEMA 2015 – Forest Products Society 2015, Dubrovnik, Croatia 241 DETERMINING THE EFFECT OF POPULUS TREMULA DENSIFICATION ON THE DEFORMATION TENSION CHARACTERISTICS UNDER PRESSURE PERPENDICULAR TO THE RADIAL DIRECTION FIBERS Tomáš Svoboda, Milan Gaff, Tomáš Brutovský ABSTRACT The paper is oriented to determining the effect of densification (10% and 30%) of Populus tremula wood-pulp on the evaluated characteristics, which are the deformation tension characteristics under pressure perpendicular to the radial direction fibers. Aim of the paper was to determine the behavior of densified (10%, 30%) and non-densified Populus tremula up to the proportional limit for the purpose of creating materials of specific characteristics for given application intent. The resulting values of the tests were graphically processed and evaluated by the form of tables. Keywords: densification, Populus tremula, proportional limit 1. INTRODUCTION As a consequence of improved properties and excellent mechanical properties of composite wood-based materials, the wood finds ever wider utilization as an ecological and renewable material. Thanks to composite materialsĽ such as glued laminated beams (Sviták et al., 2014), it ascends among leading positions of utilization, ahead of other construction materials, which until now have shown better technical properties compared to untreated wood. We can assume, that its properties will improve up to some point of surface pressing, and after the violation of this limit, great differences in created deformations may occur, by which the structure and integrity of the wood begins to disrupt (Gaff, M., ZemiarĽ J.Ľ KoristovἠE.Ľ 2ŃńŃ). By this reason we are trying to dete rmine the limit up to which is possible to consider the densification as an enhancement to the examined wood characteristics. The state, in which the wood achieves the highest level of plasticity, however, with the lignine – saccharide matrice compounds of the wood undamaged as much as possible, is convenient for the technology of molding (Gaff, M. , Zemiar J., 2008). The process of surface densification by pressing generally takes place in three phases. Those are plasticization, actual pressing and conditioning (żaffĽ M.Ľ żáboríkĽ J.Ľ 2ŃŃř). The results of the authors' work (GAFF, M. , ZEMIAR J., 2006) showed that for the process of densification, the moisture higher than 12% is better than a lower one, and on that account we examined the effect of the mentioned factors at 12% moisture. With wood-based materials, contrary to the actual wood, we can regulate the level of anisotropy, for example the size and orientation of the wood particles. This is a significant advantage of these materials, considering we can control their properties in individual areas according to demands on the final utilization. Non-negligible fact is also the option to utilize a raw material of lower quality for the production of high quality product. In construction industry and lumber industry we encounter with increasing frequency material designs, properties of which have to be examined before they are actually created. An example of this could be floorings, on which specific demands are made. Flooring should be resistant to mechanical damage, which should be ensured by upper treading layer, and also flexible and resistant to dynamic stressing.