Diffusion and reaction of chemical impregnants in solid wood cell walls

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The sustainable use of wood based products depends on their long term and effective performance in a wide range of environmental exposures. Properties of wood that affect its performance, such as decay resistance, dimensional stability, fire resistance and weathering performance, depend on the physical and chemical nature of the cell wall components of the hollow wood fibres. These physical and chemical properties can be changed through treatments whereby inorganic or organic substances in solution are pressure impregnated into the cell lumens or void spaces from which some of the dissolved substances may diffuse into the cell walls. The long-term efficacy of the treatments may be enhanced by strategically reacting or fixing the substances within the cell wall structure. Examples of efficacious inorganic treatments are borates against fungi, insects and fire, phosphates against fire and copper and zinc against micro-organisms. Non metallic substances such as organic wood preservatives and soluble monomers and polymers can also be effective treatments to protect or stabilize wood. Since all modes of wood deterioration are related to physico-chemical changes occurring in the cell walls, it is evident that the amount and distribution of protecting chemicals in the wood substance should affect their performance. However, relatively little is known about the relative rates of diffusion of these substances from the penetrated void space of the wood, into the cell wall material nor of their equilibrium distributions and configurations in the cell wall matrix. The objective of the proposed work is to develop an understanding of the diffusion and reaction of different components in the wood microstructure and their micro-distribution and configuration in the cell walls, as affected by compound or ion type, processing conditions and chemical properties of the wood. Potential benefits of the proposed work include developing approaches to enhancing the performance and effectiveness of chemically treated wood and improving our understanding of cell wall structure and conformation of substances in the cell walls.