1: Shrinkage of wood, that is, the characteristics of the wood to reduce its size when it is dried. Dry shrinkage does not occur during the entire process of wood moisture evaporation, but only at the water content below the fiber saturation point. Below the fiber saturation point, wood shrinkage gradually increases with the decrease of moisture content, and the water content decreases until At zero, the shrinkage reaches its maximum.2: The swell of wood, that is, the property of wood to absorb moisture and increase its size and volume. It starts from when the water content is equal to zero, and increases with the gradual increase of the moisture content of the wood. When the moisture content of the wood reaches the fiber saturation point, the expansion amount reaches its maximum. In the drying process of wood, due to poor drying, it may cause warping and cracking of wood, and other defects. Wood can change its size at any time due to changes in atmospheric humidity. In the production process, reasonable drying techniques and other measures are adopted to reduce the shrinkage and swelling of wood, which is of great significance in the use of wood.The swelling and shrinkage of wood is due to the penetration of water into the microfibrils, which increases the gap between the fibrils, which in turn affects the size of the wood. Under certain conditions, the increase of the microfibril gap is limited. If it is under its full-swelling conditions, it will be able to achieve a stable size by transferring certain substances to the inner space of these gaps and restricting them from returning to the original state when the moisture is reduced. However, only the absorption of water in the wood can cause changes in the size of the wood. This part of the water and the wood are combined in the form of chemical bonds and hydrogen bonds. If the hydrophilic group (mainly an OH) in the wood is removed or reduced, it is reduced. The water absorption of wood can also increase the stability of the wood size."
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