Investigation of Chemical Changes in the Structure of Thermally Modified Wood

Abstract

Thermal modification beneficially alters several technological parameters of wood. The changes in the physical parameters are due to the significant alterations of the structure and the chemical composition of wood, which take place during the modification process. These changes are complex and some aspects are still far from being completely understood. Various industrially important hardwoods and softwoods have been treated in an autoclave in N 2 atmosphere. The physical (density, L-value, moisture content, bending strength, MOE) and chemical (pH, hemicellulose-, total phenol-and soluble carbohydrate content) parameters have been measured and evaluated. By establishing linear correlations between physical and chemical parameters the chemical changes affecting the physical properties could be investigated and tracked. Very good correlations have been found for hardwood samples, whereas for softwoods only poor correlations have been established. Results could contribute to a better understanding of the reactions of thermal modification, and could furthermore provide a basis for wood species dependent technology optimization in the future.

Impact of Selected Technological, Technical, and Material Factors on the Quality of Machined Surface at Face Milling of Thermally Modified Pine Wood

“…These changes improve wood's properties, such as resistance to insects, reduction of wood hygroscopicity, shape stability (based on the relationship of wood to water), etc. (Barcík and Homola 2004;Niemz et al 2010). Thermally modified wood is a relatively new type of material, with an innovative structure for thermal modification at temperatures from 150 °C to 260 °C.…”

Effects of Boron Impregnation and Heat Treatment on Some Mechanical Properties of Oak (Quercus petraea Liebl.) Wood

“…Heat treatment, as a wood modification method, serves to improve the natural properties of the wood, such as dimensional stability (Esteves et al 2008b;Todorovic et al 2012) and resistance to bio-deterioration, as well as bestowing the wood material with new properties (Altinok et al 2010). The modification treatment is always performed in the temperature range of 180 to 240 °C (Niemz et al 2010). Heat treatment, especially at temperatures over 150 °C permanently changes the physical, mechanical, and chemical properties of wood (Mitchell 1988;Yildiz et al 2006;Gunduz et al 2008).…”

Physical Properties of Boards Manufactured with Hygrothermally Treated Tepa (Laureliopsis Philippiana Looser) Particles

“…L. philippiana wood exhibits high pH values (5.7 to 7.4), which is not favorable for the production of boards using acidic setting adhesives (UF) (Poblete, 2001). Wood pH decreases after high temperature thermal treatment (Niemz et al, 2010). Thermal treatments cause decomposition of hemicelluloses and acidify the wood (Poblete, 1983), which could favor setting of the UF and improve physical properties of the board.…”

“…High temperature heat treatment (thermo-modification) is known to improve dimensional stability of wood as well as its resistance to rot (Niemz et al, 2010). Thermal modifi cation drives structural and chemical changes in wood constituents, which may signifi cantly alter their properties when compared to non-treated wood (Arnold, 2010).…”