STUDY ON VAPOR-PHASE BORATE PRESERVATIVE TREATMENT OF WOOD

Studies on vapor-phase borate preservative treatment of Masson pine ( Pinus massoniana ) and Douglas firPseudotsuga menziesii (Mirbel) Francowood samples had been carried out.The optimum preservative treatment conditions were investigated by using orthogonal experiment as follows: wood sample moisture content 10%, preservative treatment temperature 75℃, reduced-pressure treatment 97.325 kPa, preservative temperature 32℃. Boric acid content of Masson pine sample was 6.13%. Test results of vapor-phase borate preservative treatment on Douglas fir heartwood samples that can hardly be treated indicated: permeability was good. Using electronic microscopy,it was found that boric acid was deposited in both samples by vapor-phase treatment and by liquid treatment. However, boric acid content of samples of the former was higher than that of the later in wood cells. Testing results on mechanical properties and dimensional change of Masson pine samples indicated that impact strength and modulus of elasticity of the treated wood decreased insignificantly. Bending strength of the treated wood was elevated by 4.6%. Dimensions of wood samples changed very small.