Effects of borate impregnation on the response of wood strength to heat treatment

Based on the strong correlation between acidity and thermal degradation in wood reported in previous studies, the effect of borate impregnation as an alkali-buffering medium was investigated on the strength properties of thermally modified wood. Wood samples were impregnated with 0.1 M Sodium borate solution (pH=9) before they were subjected to heat treatment at temperatures of 180°C and 200°C for durations of 2 and 4 h. The borate impregnation results in some reductions in the severity of strength loss during heat treatment and this is invariably due to buffering effect of the alkali on the acidity of wood, which could have mitigated the degree of degradation. The positive effects of borate impregnation as a pretreatment on the strength properties of heat-treated wood depend on the degree of heat treatment. Hence, the use of borate impregnation as a pretreatment method for heat treatment is recommended only where a relatively mild heat treatment is involved.