The effect of water repellents on some physical and mechanical properties of thermo-mechanical densified wood materials

The aim of this study is to determine some physical, mechanical and technological properties of wood materials densified by thermo-mechanical method at different temperatures and rates after being impregnated with water repellents. For this purpose, the samples prepared from Uludağ fir (Abies bornmülleriana Mattf.) and aspen (Populus tremula L.) woods were impregnated with paraffin, linseed oil and styrene in an atmospheric pressure environment by pre-vacuum. The impregnated samples were then compressed using thermo-mechanical method at three different temperatures (120 °C, 150 °C and 180 °C) and two different compression ratios (20% and 40%) using a hydraulic press. In the test samples, the spring-back ratio, air-dry density, water absorption and compression direction (radial) swelling ratio were performed to determine the physical properties while static bending strength, modulus of elasticity, compression strength and Janka hardness tests were performed in order to determine mechanical properties. According to the results of the study, impregnation pre-treatment significantly affected all of the selected properties of impregnated fir and poplar samples. Compared to the application of paraffin and linseed oil, more positive results were obtained in the samples treated with styrene. Impregnation was pre-treated and the density of air drying increased up to 174% in the densified samples. Thanks to the impregnation pretreatments in the densified samples, the spring-back, water absorption and compression direction (radial) swelling ratios decreased by 81%, 90% and 91%, respectively. On the other hand, 93% increase was obtained in mechanical strength properties and 636% increase was obtained in hardness values of the impregnated and densified modified samples compared to untreated (control) samples.