Swelling of Pinewood (Pinus Sylvestris) in Binary Aqueous Solutions of Organic Substances

Abstract

Samples of pine (Pinus Sylvestris) sapwood were swelled in binary mixtures. Binary mixtures used in this study were aqueous solutions of ethanol, isopropanol, acetone and dimethylformamide. The tangential, radial and longitudinal swelling was measured and volumetric swelling of oven-dried samples was determined. The synergic effects of swelling in aqueous solutions were observed. The properties of binary liquid systems have a major influence on the swelling of wood. Microscopy studies of wood samples show that after swelling in water the cells are densely packed and the compound middle lamellae (CML) has arranged in a form of continuous ribbon around the cells. The swelling of wood in ethanol-water mixtures has a dramatic effect on the wood structure through dissolving a main part of lignin from CML and released individual cells at sectioning. Acetone and acetone-water mixtures have an insignificant effect on the cell wall structure and its bonding to the CML. The swelling in DMF opened up the location of the primary wall layer and S3 layer. There is no substantial difference in the influence on the cell structure between pure DMF and its mixture with water.