A Study of the Physical and Mechanical Properties of Modified Wood

By means of the thermochemical method of wood modification it is possible to achieve a comprehensive improvement of wood properties—to significantly increase its strength properties and hygroscopicity. During deep and through impregnation with a colored solution, wood is colored due to the solution moving inside the wood through the cavities of cells having a tubular structure. Having penetrated inside the wood through the capillaries of vessels, tracheids and medullary rays, the dye colors the cell walls, diffusing into their intercapillary spaces. In this case, the cell walls are colored more intensively than the cell cavities. The increase in the strength of modified wood is explained by insufficient water adsorption due to a decrease in the diameter of tracheids filled with the modifier solution; apparently, this is also associated with a decrease in the contact area with water of the glue–wood boundary layer due to a decrease in the size of the cell cavities. The shear strength along the fibers corresponds to the European standard EN205 D4. The increase in water resistance of modified wood is due to the fact that urea compacts the wood and gives it increased dimensional stability.