Mechanism of wood fiber in powder


Release time:

2020-05-18

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Mechanism of wood fiber in powder
 
Wood fiber is a multifunctional additive which can be used in cement, gypsum, lime and other powder materials. Wood fiber is extracted from wood pulp. It is chopped, neutralized, bleached, and crushed, and the lignin and hemicellulose in wood pulp are completely separated, because these two elements have side effects on the hydration and strength of cement and gypsum. It is then sieved into finished products with different fiber lengths and coarseness to meet the needs of different application materials. Some functions of wood fiber, such as thickening, thickening, etc., are similar to cellulose ethers, but wood fiber is a natural material that is insoluble in water (cellulose ethers are soluble in water), so it is more effective for powder materials., And from the price point of view, it is much cheaper than cellulose ethers.
 
Wood fiber has a variety of grades (such as fiber length, density, purity), fiber length from 10um to 2000um. The density of wood fibers is about 0.8-1.3g/cm3. Wood fiber fiber is very strong, the fiber surface is also very similar to asbestos, and completely non-toxic harmless, wood fiber saturated moisture content is about 10 ~ 12%, the normal moisture content between 4 ~ 8%, so it needs to be stored in a dry place, wood fiber does not absorb moisture in the air and affect its performance. Insoluble in water and organic solvents, resistant to dilute acid and acid and alkali. The alkaline of cement will not cause any harm to it and affect the performance of powder materials. Wood fiber is very inert, it will not react with any other materials in the powder material, only play a physical role. Wood fiber has frost resistance (no frost effect).
 
Mechanism of wood fiber in powder
 
1. Strong thickening effect. Wood fiber has a strong cross-linking function. After it is mixed with other materials, the fibers immediately overlap like a blanket. This three-dimensional structure can lock water or other liquids in between. The longer the fibers, the greater the thickening effect.
 
2. The structural stickiness of the wood fibers improves handling performance. When shear forces act on it (e. g. scraping, stirring, pumping), part of the liquid will be thrown from the fiber structure into the matrix, resulting in a decrease in viscosity and an increase in workability. When the shear force ceases, the fiber structure recovers again very quickly and absorbs the moisture back and restores the original viscosity.
 
3. Good liquid force. Wood fiber itself can absorb 100 to 200 percent of the weight of the liquid, and use its structure to absorb 2 to 6 times the weight of the liquid.
 
4. Cracking resistance. The mechanical energy generated during curing or drying is attenuated by the fiber bars.
 
5. Low shrinkage. The dimensional stability of wood fibers is very good, which means that the mixture does not undergo shrinkage settlement and improves its crack resistance.
 
6. Anti-sagging. There will be no falling phenomenon during the construction operation and drying process, which makes the thicker plastering can be completed at one time, and the wood fiber has good thermal stability even under high temperature conditions.
 
7. Extended opening hours. Due to the capillary action of the fiber structure, the internal water can be quickly transmitted to the surface and interface of the slurry, so that the water inside the slurry system is evenly distributed, the crust phenomenon can be significantly reduced, and the bonding strength and surface strength can be significantly improved. This mechanism also plays a role in cracking resistance due to the reduction of tension in the drying process.
 

Key words:

Wood fiber