Significance of wood drying
Wood drying is the process of heating the wood under the condition of controlling the medium temperature and relative humidity, so that the internal moisture of the wood moves to the surface, the surface moisture evaporates to the outside, and the process of gradually removing moisture from the wood. In order to achieve effective drying quality, it is necessary to control the temperature and humidity of the drying medium, and adopt a reasonable drying process and operation method. The more common method used at present is the method of convection drying.So what are the benefits of drying wood? There are mainly the following aspects:
1. Improve the stability of wood and wood products. We know that tree growth not only grows along the height of the tree, but also grows horizontally to increase the diameter of the trunk, so the wood processed from the tree is an anisotropic material. When the wood is exposed to the air for a long time, the moisture in it will change with the change of the relative humidity of the air, and the wood will expand with the increase of air humidity and shrink with the decrease of air humidity. The swelling and shrinkage of the wood caused by uneven moisture in the wood often causes cracking and deformation of the wood, thereby affecting the use and causing waste. The common problems of solid wood flooring are seams and warping, which are mostly related to the dry quality of the wood. For example, some wood floors have large gaps between the slats after a few days of laying, which is mostly related to the water content of the floor before laying. The rate is too high, and it shrinks due to indoor high temperature or air drying; the warping is mainly caused by the fact that the solid wood floor has not been properly dried. If the production unit dries the wood to the required moisture content before use, it can ensure the stability of the wood product structure, make the appearance beautiful and durable.
2. Increases the strength of wood and wooden parts. We know that wood is processed from trees, and the growth of trees is formed by the continuous growth of thousands of cells, so the wood we use is formed by the regular arrangement of thousands of cells. Cells are composed of cell walls and cell lumens. When the water in wood exists only in the wood cell walls, we call it absorbed water; when there is water not only in the wood cell walls but also in the cell lumens, we call this water free water. When there is no moisture in the wood cell cavity, and the moisture only exists in the cell wall, the strength of the wood increases with the decrease of the moisture content of the wood. It can be seen that when the wood is dried and reaches the required moisture content, not only the cutting performance of the wood can be improved, but also the strength of the wood structure parts, the bonding strength and the surface decoration quality of the wood products can be improved. Wood's thermal and insulating properties reduce thermal and electrical conductivity.
3. Prevents degradation and decay of wood. Wood is a natural polymer aggregate, mainly composed of cellulose, hemicellulose and lignin, and also contains a small amount of resin, gum, pigment and other inclusions. Wet lumber can become prone to decay or insect infestation if it is stacked in the open air for long periods of time without proper protection. Therefore, after the wood is dried at a temperature of about 60°C, when the moisture content of the wood is reduced to below 20%, the damage and damage of fungi and pests can be greatly reduced. Some production units dry the wood to a moisture content of about 8-15%, which not only ensures the inherent properties and strength of the wood, but also improves the corrosion resistance of the wood.
4. Reduce the weight of wood. Since the initial moisture content of raw wood is very high, even exceeding its own weight, after short-term storage and natural drying, the weight of wood can be reduced.
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