Enhancement of the dimensional stability of natural wood by impregnates

Purpose To investigate the effects of acetylation process as a chemical treatment method to improve the dimensional stability of wood, or as a pre-treatment step to enhance the dimensional stability of wood by impregnates. Design/methodology/approach - Esterification of two species of wood were carried out by vapour and liquid phase acetylation processes. With the vapour phase acetylation process, wood with different acetyl contents were obtained by changing the length of time of treatment. With the liquid phase acetylation, different acetyl content were obtained by changing the acetylating mixture or by activating wood with acetic acid for different periods of time and at different temperatures prior to the acetylation processes. The acetyl content and the conditions of impregnation improving the dimensional stability were modelled and optimised. The success of acetylation process for improving the affinity of wood towards the impregnation was also demonstrated. Findings - Vapour phase acetylation process was preferable over liquid phase acetylation for improving both water resistance and dimensional stability of wood species examined. Liquid acetylating of wood, as a pre-treatment step enhanced the effect of impregnates, especially the linseed oil to improve relevant wood properties. The greater improvement was obtained at 3 h impregnation time and 190 degrees C curing temperature for 1 h. Research limitations/implications - Despite the success in improving the affinity of wood species to novolac by pre-acetylation, increasing the curing time and curing temperature led to deterioration of the water resistance and dimensional stability. Practical implications - Pre-acetylation of the wood provided a practical solution to rendering the natural wood greater water resistance property using commercial impregnates. Originality/value - The method for acetylation of wood prior to impregnation was novel and could be used for inhibiting wood against moisture absorption during storage.