Wood Preservation: Improvement of Mechanical Properties by Vacuum Pressure Process

Md. Fazle Rabbi, Md. Mahmudul Islam, A.N.M. Mizanur Rahman

Wood, being a biological product, is liable to deterioration unless it is properly protected. The main reasons of deterioration of timber in service are decay due to fungal infection, attack by insects (borers and white ants), marine organisms and fire. Protection of wood is carried out from these agents by using preservative which can properly be used by proper design of preservation plant. Proper design of such plant is very essential to increase the lifespan of wood economically. Among the various wood preservation techniques, pressure processes are the most permanent technique around the world today. In the Full cell process, wood is allowed to absorb as much liquid chemicals as possible during the pressure period, thus leaving the maximum concentration of preservatives in the treated area. Usually, water solutions of preservative salts are employed with this process but it is also possible to impregnate wood with oil. The desired retention is achieved by changing the strength of the solution. A Full cell pressure wood preservation system was designed and constructed in Mechanical Engineering Department of KUET and its performance was tested. The pressure cylinder was constructed using locally available materials and different physical properties of wood were measured. It was observed that the weight of wood reduces due to loss of moisture, density, retention, penetration of preservatives into wood due to pressure in the cylinder. The penetration is more or less uniform throughout the surfaces.