Modification process results in boosted durability
The root cause of expansion and contraction of wood is that wood is a hygroscopic material. Its hygroscopicity is mainly caused by the free hydroxyl groups (OH) in the three main polymers that make up wood: cellulose, hemicellulose and lignin. These hydroxyl groups can form hydrogen bonds with water molecules. In addition to the wood in the hemicellulose, lignin and other substances can also absorb water molecules; water molecules into the wood components of the distance between the molecules increased, the wood is swelling, resulting in dimensional instability.Take cellulose (C6H10O5)n for example: Calculation of the water content of cellulose - 3 x 18/162 = 33.33% (3: the number of water on each base ring; 18: the relative mass of water molecules, 162: the relative molecular mass of a base ring)
To improve the dimensional stability and reduce moisture absorption of wood, during the modification process, modifiers deposit and cure within the intercellular layers, cell lumens, and cell walls of the thin-walled cells, forming mechanical bonds. The modifiers redistribute throughout and fill the cell lumens and voids, penetrating into the cell walls, thereby stabilizing compressed cell lumens and bonding with cell wall substances. Cross-linking reactions occur between the wood and modifiers, as well as among the modifiers themselves, leading to a decrease in surface oxygen-to-carbon ratio and hydroxyl content, resulting in chemical bonding.
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