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Types of cellulose ethers and mechanism of action (III)

Views:1     Author:Site Editor     Publish Time: 2021-11-09      Origin:Site

Following the previous article, we continue to introduce HEC and CMC in the classification of cellulose ethers. 

1.1.3 Hydroxyethyl cellulose (HEC) 

It is made from refined cotton treated with alkali and reacted with ethylene oxide as etherizing agent in the presence of acetone. Its substitution degree is generally 1.5~2.0. It has strong hydrophilicity and is easy to absorb moisture. 

(1) hydroxyethyl cellulose can be dissolved in cold water, hot water dissolution is more difficult. Its solution is stable at high temperature and does not have gel. It can be used for a longer time under high temperature in mortar, but the water retention is lower than that of methyl cellulose. 

(2) hydroxyethyl cellulose has stability to general acid and alkali, alkali can accelerate its dissolution, and slightly improve the viscosity, its dispersibility in water is slightly worse than methyl cellulose and hydroxypropyl methyl cellulose. 

(3) hydroxyethyl cellulose has good performance on mortar anti-draping, but the slow setting time of cement is longer.

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1.1.4 Carboxymethyl cellulose (CMC)\[C6H7O2(OH)2och2COONa\]n 

Made from natural fibers (cotton, etc.) after alkali treatment, with sodium monochloroacetate as etherizing agent, after a series of reaction processing and made of ionic cellulose ether. The degree of substitution is generally 0.4~1.4, and its performance is greatly affected by the degree of substitution. 

(1) Carboxymethyl cellulose is more hygroscopic, general conditions of storage will contain large water.

 (2) Carboxymethyl cellulose aqueous solution does not produce gel, with the temperature and viscosity decreases. When the temperature exceeds 50℃, the viscosity is irreversible. 

(3) Its stability is greatly affected by pH. Generally it can be used in gypsum-based mortar, not in cement-based mortar. At high alkalinity, it will lose viscosity. 

(4) Its water retention is much lower than that of methyl cellulose. It has retarding effect on gypsum-based mortar and reduces its strength. However, the price of carboxymethyl cellulose is significantly lower than that of methyl cellulose. Landcel has many years of experience in developing and producing HEC and CMC, and the CMC produced and developed are used in various applications such as construction and food.

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