Thickening and thixotropy of cellulose ethers

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Thickening and thixotropy of cellulose ethers: the second role of cellulose ethers-thickening depends on the degree of polymerization of cellulose ethers, solution concentration, shear rate, temperature and other conditions. The gelling properties of the solution are unique to the alkyl cellulose and its modified derivatives. The gelation characteristics were related to the degree of substitution, solution concentration and additives. For hydroxyalkyl modified derivatives, the gel characteristics are also related to the degree of modification of the hydroxyalkyl group. For cellulose and HP cellulose with low viscosity solution concentration, 10%-15% concentration solution can be prepared, medium viscosity cellulose and HP cellulose can be prepared with 5%-10% solution, while high viscosity cellulose and HP cellulose can only be prepared with 2%-3% solution, and the viscosity classification of cellulose ether is usually classified with 1%-2% solution. High molecular weight cellulose ether thickening efficiency, the same concentration solution, different molecular weight polymers have different viscosity, viscosity and molecular weight can be expressed between the following,[η]= 2.92 × 10-2(DPn)0.905,DPn is the average degree of polymerization of high. The low molecular weight cellulose ether can be added in a large amount to achieve the target viscosity. The viscosity is less dependent on the shear rate, the high viscosity reaches the target viscosity, the required addition is small, and the viscosity is determined by the thickening efficiency. So to achieve a certain consistency must ensure a certain amount of cellulose ether (solution concentration) and solution viscosity. The gel temperature of the solution also decreases linearly with the increase of the concentration of the solution, and the gelation at room temperature after reaching a certain concentration. The gelling concentration of HP cellulose is higher at room temperature.

The consistency can also be adjusted by selecting the particle size and selecting cellulose ethers of different degrees of modification. The so-called modification, is the introduction of a certain degree of substitution of hydroxyalkyl in the backbone structure of cellulose. By changing the relative substitution values of the two substituents, that is, the DS and ms relative substitution values of methoxy and hydroxyalkyl. The requirements for various properties of the cellulose ether are obtained by varying the relative substitution values of the two substituents.

The relationship between consistency and modification: the addition of cellulose ether affects the water consumption of mortar, and changes the water-cement ratio of water and cement, which is the thickening effect. The higher the dosage, the higher the water consumption.

Cellulose ethers used in powdered building materials must dissolve rapidly in cold water and provide a suitable consistency for the system. If given a certain shear rate is still flocculent and colloidal block, this is unqualified or poor quality products.

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