Features of Wood Impregnation with Water-Soluble Protective Agents

Wood impregnation with water-soluble agents is widely used in various industries. For example, in shipbuilding, this method of preparing raw materials is common in the manufacture of scaffolding: they are treated with fire retardants to meet fire safety requirements. Impregnation can be performed faster and more efficiently under pressure. Taking into account the data on the conditional compressive strength across fibers for pine and spruce, as well as the characteristics of impregnation stands upgraded at enterprises, it is of practical interest to study the impregnation process under hydraulic pressure of 1...5 MPa. For this purpose, an experimental setup has been developed and samples of spruce have been made, having equal dimensions, weight and moisture content, but differing in the type of wood (heartwood, sapwood and mixed), as well as in the arrangement of annual rings (radial or tangential). During the experiment, the dependence of the depth of wood impregnation for wood samples of 6 groups on excess pressure and duration of exposure has been studied. A methylene blue solution has been used as the impregnation solution, which has made it possible to estimate the depth of impregnation of the samples. The preservation of the shape of laboratory samples after exposure to high hydraulic pressure has also been recorded. Based on the results of the study, it seems most appropriate to increase the solution pressure in the impregnation cylinder to 3 MPa; a further increase does not lead to significant changes. No noticeable effect of hydraulic pressure on the shape of laboratory samples has been observed. The obtained dependencies indicate the possibility of significantly reducing the duration of wood impregnation with water-soluble protective agents, which, in turn, contributes to increased productivity and lower cost of final products.