Dimensional stability and treatment of wood
The dimensional stabilization of wood is a treatment method to change its hygroscopic and hygroscopic properties without destroying the complete structure of the wood cell wall.The main methods for dimensional stabilization of wood are: ①Mechanical inhibition by cross-lamination; ②Interior or exterior finishing of waterproof coatings; ③Reduce hygroscopicity of wood; ④Chemical crosslinking of wood cell wall components Compatibility; ⑤ heat treatment.
①Mechanical inhibition by cross-lamination: For example, plywood adopts the method of vertical lamination. Due to the difference in the transmission speed of longitudinal and transverse moisture of wood, vertical arrangement is used to inhibit the rapid spread of longitudinal moisture.
②Waterproofing treatment: Apply the waterproofing substance on the wood surface and leave it outdoors for a year, only the water repellent containing wax is more durable, and the water repellent containing linseed oil (preferably mixed with paraffin), varnish and silicone resin is more durable. The effectiveness of water agents in outdoor exposure is getting worse and worse. The waterproof rate of silicone oil, paraffin and other treated materials can reach 75%-90%, and the mixed water repellent is better than a single one.
③Anti-moisture treatment: Apply resin paint on the wood surface, or dissolve the water-repellent material in a volatile solvent to make a solution with low viscosity and good fluidity, inject it into the wood, and leave it on the inner surface of the wood when the solvent evaporates.
④ To chemically cross-link the wood cell wall components to make the cell wall compatibilized in advance: the commonly used chemical reagents are phenolic resin, polyethylene glycol, acetyl and so on.
⑤ Heat treatment: Hemicellulose, especially polyuronic acid, undergoes chemical changes to form polymers with poor hygroscopicity. At the same time, heating removes absorbed water, and the distance between molecular chains in the amorphous region of cell wall cellulose shortens to form new hydrogen bonds. . Using steam, air, nitrogen and other gases or vegetable oil as a medium to heat treatment, the obtained product is "heat-treated wood", which is commonly called "carbonized wood" in processing enterprises and commercial circulation fields. Wood heat treatment equipment, carbonization kiln and carbonization tank, the carbonization temperature can reach 160~230℃.Heat treated material is processed without any chemicals, unbonded or painted, non-toxic, and can be used indoors and outdoors. Therefore, heat-treated material products are environmentally friendly products. In addition, the stability and corrosion resistance of wood are significantly improved after heat treatment.
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