How does the change of water absorption rate of wood affect its performance?
The water absorption rate of wood is called the change of water content in the industry. The change of water content of wood is not caused by water absorption in most cases, because wood products are rarely put into water in the process of use. So the change of wood moisture content is mainly attracted by moisture absorption and desorption, that is, according to the change of relative humidity in the surrounding environment.
First, wood naturally has the characteristics of dry shrinkage and wet expansion. Wood with higher moisture content will expand in different directions. Generally, chord direction is larger than radial direction, and wood with lower moisture content will shrink and become smaller in size. So there are mostly expansion joints around solid wood furniture panels and panels.
Secondly, wood decay occurs when its moisture content is high, which is related to the growth characteristics of decaying fungi. That is, the specific moisture content range is suitable for its growth and reproduction, but too high and too low moisture content can play a role in preservation. Therefore, wood is generally dried to reduce moisture content, while logs can be stored in water or continuously dripped.
Third, the electrical conductivity, thermal conductivity and moisture content of wood are also related, but this has no impact on daily life.
Fourthly, many mechanical properties of wood are related to moisture content. The lower the moisture content, the better the bending resistance and the greater the strength of wood.
Fifth, when the moisture content is below the fiber saturation point, the strength of wood decreases with the increase of moisture content, which is due to the softening of wood cell wall with the increase of adsorbed water. When the moisture content of wood is above the fiber saturation point, the strength and other properties of wood are basically stable, and do not change with the change of moisture content. Moisture content has a great influence on the compressive and flexural strength along grain, but has no effect on the tensile strength along grain. According to the standard of our country, the strength value at 15% moisture content is taken as the standard, and the strength at other moisture content can be converted by formula.