Timber Dimensional Stability and Treatment Methods

Dimensional stabilization of wood is a treatment method that changes its moisture absorption and shrinkage and swelling properties without destroying the complete structure of wood cell walls. The methods for dimensional stabilization of wood mainly include: ① mechanical inhibition by cross-lamination; ② internal or external coating of waterproof coating; ③ reduction of wood hygroscopicity; Compatibility; ⑤ heat treatment.
①Mechanical inhibition by cross-lamination: For example, plywood is vertically laminated. Since the speed of moisture transmission in the longitudinal and transverse directions of wood is different, vertical arrangement is used to inhibit the rapid spread of longitudinal moisture.
②Waterproofing treatment: apply waterproofing substance on the wood surface, and after one year of outdoor storage, only the water repellent containing wax will be more durable, and the water repellent containing linseed oil (preferably mixed with paraffin), varnish and silicone resin will be more durable. Water agents are less and less effective on outdoor exposure. The waterproof rate of silicone oil, paraffin and other treated materials can reach 75%-90%, and the effect of mixed water repellent is better than that of a single one.
③Moisture-proof treatment: apply resin paint on the wood surface, or dissolve 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 after the solvent volatilizes.
④Chemical cross-linking of wood cell wall components to pre-compatibilize the cell wall: commonly used chemical reagents include phenolic resin, polyethylene glycol, acetyl, etc.
⑤Heat treatment: Hemicellulose, especially polyuronic acid, undergoes chemical changes to form polymers with poor hygroscopicity. At the same time, heat removes adsorbed water, and the distance between molecular chains in the amorphous region of cell wall cellulose is shortened to form new hydrogen bonds. . Use steam, air, nitrogen and other gases or vegetable oil as a medium for heat treatment, and the obtained product is "heat-treated wood", which is customarily called "carbonized wood" by processing enterprises and commercial circulation fields. The picture shows Xingnan wood heat treatment equipment, carbonization kiln and carbonization tank, the carbonization temperature can reach 160~230℃.

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