Water-uptake ability of Longitudinally Compressed (Accordionisated) Wood

What is it about?

Examinations showed the effect of longitudinal wood compression on hygroscopicity. The compression-relaxation process influenced moisture-related behaviour, but there were only small differences. Due to compression and relaxation, the fibre-saturation point is about 6% (MC%) lower at desorption compared to the native wood. However, after adsorption the fibre-saturation point is the same for treated and control beech wood. Steaming reduced the equilibrium moisture content at the beginning of the desorption by 3.7% (MC%). The difference later decreased, while at equilibrium moisture content below 10%, all moisture contents were the same. Compression causes up to 1% (MC%) deviation of adsorption between control and compressed samples. Compressing lowers, while steaming increases the speed of the humidity uptake. Under the same circumstance, the moisture content of the longitudinally compressed wood is never higher than the moisture content of the longitudinally compressed wood. This could be due to the partial degradation of hemicelluloses. Compressed material adapts to new climatic conditions faster at first desorption, so the drying process of treated wood can be performed in less time. The moisture adsorption of compressed wood is slower. This can be considered a positive property because wood in use shrinks and swells less in varied air conditions, making it more stable and more resilient to cracking. This assumption will be the subject of a later study.

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Why is it important?

Knowledge of wood moisture content and the change of MC are important because these provide answers to many questions about the behaviour of wood during later use. With the change of MC, there is considerable variation in strength and elasticity characteristics, density, shrinkage and swelling as well as anisotropic properties, surface adsorption, optical properties, resistance to insects and fungi, etc., between the absolute dry state and the fibre-saturation point.

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