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Heat-treatment of solid wood to increase its dimensional stability and durability is well known and established in the industry. To enhance the application of wood-based panels (e.g. for exterior application) their durability against moisture and fungal decay has to be improved. In this paper a possibility is shown, how to adapt a heat treatment process on wood-based panels. Two different temperatures were applied on strands of Scots pine, before hot-pressing oriented strand board. The mechanical properties show an influence of the applied temperature on the strands and of the adhesive used for the panel. The thickness swelling is reduced (Fig. 3), resulting in increased dimensional stability. The process temperature has a major influence; with an increased pre-treatment temperature the thickness swelling is reduced. The internal bond strength was not affected by the pre-treatment

Steam pre-treatment can effectively improve the dimensional stability of panel products such as particleboard and fiberboard. At temperatures above 200-210 degrees C steam pre-treatment might result in a significant reduction of the bond strength of the panel product. The results of an effective two stage heat pre-treatment process, in which treatment temperatures below 200 degrees C are used, are given in this paper. The variations in process conditions which affect the particleboard properties are described in detail. A two-stage heat pre-treatment with temperatures below 200 degrees C appears to improve the dimensional stability of panel products. The process conditions used have an effect on thickness swelling and internal bond properties of the particleboard prepared, especially during the first process stage (hydrothermolysis). The best results were obtained with wood particles which were only thermolysed (without curing)

An oriented strand board (OSB) made of Scots pine (Pinus sylvestris L.) was tested for volatile organic compound (VOC) emissions 24 h after the hot-pressing process over a period of 2 months. The predominant emissions from the OSB were monoterpenes and aldehydes. Terpene emissions decreased continuously, whereas aldehyde concentrations initially increased and subsequently decayed. Aldehydes are formed by the autoxidative splitting of unsaturated fatty acids contained in the wood. Due to the delayed release of aldehydes, a comparison of different emission test results is only possible if age and storage conditions are clearly specified. For a reduction in VOC emissions from wood-based materials, wood properties, manufacturing process, and storage conditions have to be considered.

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Most adhesive studies employing wood veneer as the substrate assume that it is a relatively uniform material if wood species and veneer thickness are constant. In the present study, veneers from rotary cut birch (Betula pendula Roth) were produced from logs harvested in spring, autumn and winter, and soaked at 20°C and 70°C prior to peeling. Firstly, veneers produced from logs felled in autumn were dried at 103°C for 24 h and subsequently half of these veneers were heat-treated at 180°C for 3 h. In addition, veneers produced from logs felled in all three seasons were dried at 160°C for 3.5 min to simulate industrial drying. The wettability of veneers was evaluated goniometrically, and bonding strength was evaluated with an automated bonding evaluation system (ABES). The results show that soaking birch logs at 70°C rather than at 20°C before peeling, or harvesting trees in the spring rather than in the autumn or winter, gives rise to veneers with enhanced wettability and higher bond strengths with a phenol-formaldehyde adhesive. Changes in the preparation and history of a veneer surface may have a profound effect on the development of adhesive bonds.

Pine and spruce heartwood and sapwood were milled to wood particles and the volatile organic compounds (VOCs) of the wood particles were tested against four bacterial strains. To study the influence of relative humidity on the antibacterial effect, both dry and wet wood particles were tested. Twenty microliters of the bacterial dilution with a concentration of 1.5×107CFU ml−1was cultured on glass surfaces in the presence of VOCs and the amount of viable bacteria was studied after 2, 4, and 24 h. The volatile emissions were evaluated by GC/MS and the results were compared with the results from the bacterial trial. VOCs had an antibacterial effect onEscherichia coli, Streptococcus pneumoniaeand slightly onSalmonella entericaserovar Typhimurium. But the effect onStaphylococcus aureuswas minute even after 3 days’ incubation. The dry wood particles generally had a stronger antibacterial effect, though the amount of VOCs from the wet wood was higher. Pine heartwood had the strongest antibacterial effect and also the highest emissions of VOCs. However, the interaction between different bacterial strains and wood species shows some variations.

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