Cellulose ethers can be monoethers or mixed ethers, and there are certain differences in their performance. On the macromolecules of cellulose, the low-substituted hydrophilic group such as hydroxy ethyl groups, can give the product a certain degree of water solubility. However, for water permeable groups such as methyl, ethyl, etc., only a moderate degree of substitution can give the product a certain degree of water solubility, and low-substituted products can just swell in water or dissolve in dilute alkali solution.
According to kinds of the substituents, ionization and solubility differences, cellulose ethers can be classified. In mixed ethers, the effects of the group on the dissolving properties follows the usual rules below.
1. It can increase the content of the hydrophobic group in the products, improve the hydrophobicity of ethers, lower the gel point;
2. It can increase the content of the hydrophilic group, and enhance the gel point;
3. The hydroxypropyl group is special, so appropriate hydroxypropylation helps to reduce the gelling temperature of the product. The gelling temperature of moderate hydroxypropylated product will be on the rise, while the substitution of high level will reduce the gel point. With high substitution, polymerization will occur on the side roup and the relative content of hydroxyl will decrease. Furthermore, hydrophobicity will be improved but its solubility will be reduced.
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