Modified Solid Wood Products

Although wood is used for many applications because of its excellent material properties, it can show disadvantages with undesirable effects in specific application areas too. Prominent examples are the variation in dimensional stability as a result of altering atmospheric conditions or the low natural durability of many domestic wood species. Wood modification has also become a topic of renewed interest because of increasing environmental considerations, e.g. some modified woods can substitute tropical hardwoods due to their darker colours and higher durability. Wood modification represents a process that is used to improve the material properties of wood, but produces a material that does not show at the end of a product life-cycle a higher environmental hazard than the unmodified wood during the disposal. 

Improvement of important application properties (higher dimensional stability, higher durability)  

Increasing demand for outdoor applications of wood (higher durability) Substitution of tropical wood species (higher durability and/or darker colours)  

Alternatives for chemically preserved wood (durable and low-maintenance assortments of domestic wood). 

This chapter can give only a short insight into some important aspects. A comprehensive overview with further and detailed information can be found in the literature.  

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To assure that new products meet or exceed existing requirements for use as building components, and to avoid confusion for the consumer, newly developed WPC products are likely to be evaluated against performance criteria for existing solid wood products. In some cases it will be necessary to modify existing standards, or develop new standards to evaluate these newly developed products. 

Hill, C.A.S., Forster, S.C., Farahani, M.R.M., Hale, M.D.C., Ormondroyd, G.A., Williams, G.R. An investigation of cell wall micropore blocking as a possible mechanism for the decay resistance of anhydride modified wood. Int. Biodeterior. Biodegrad. 55,69-76 (2005) Papadopoulos, A.N. Chemical modification of solid wood and wood raw material for composites production with linear chain carboxylic acid anhydrides a brief review. BioResources 5, 499-506 (2010)... 

The physical characteristics of wood can exert a considerable effect over the carbonization process and products. Water present in wood solids influences heat transfer the evaporation of the water requires a significant part of the heat and limits the increase of temperature of the solid material. This results in a longer process of carbonization fl-3], lower mass and energy yields (2, 4, 8], and the quality of charcoal is modified [1,4],... 

Effluents from pulp, paper and board mills contain wood materials in solid, colloidal and dissolved form. The effluents also contain some chemicals used in the production process, either in their original or modified form. The principal mechanical methods used to remove these compounds are filtration (including membrane and nanotechnology), sedimentation and/or flotation. All these methods require very good flocculation and coagulation of these undesirable substances in the effluent. Only then can they be separated from the clear water. The main chemicals used for coagulation are aluminum salts (e. g. Al2(S04)s), iron salts (e.g. FeCU or Fe2(S04)s or FeS04) and hme with addition rates of 100-500 g m effluent To achieve optimum flocculation results, it is often necessary to feed a suitable... 

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