The Properties Of Cellulose Ether
The Properties Of Cellulose Ether
In the ready-mixed mortar, the amount of cellulose ether added is very low, but it can significantly improve the performance of the wet mortar and is a major additive that affects the construction performance of the mortar. Reasonable selection of cellulose ethers of different varieties, different viscosities, different particle sizes, different degrees of viscosity and added amount will have a positive effect on the improvement of the performance of dry mortar. Currently, many masonry and plastering mortars have poor water retention properties, and water slurry separation occurs after a few minutes of standing still. Water retention is an important performance of methyl cellulose ether, and it is also a performance that many domestic dry mortar manufacturers, especially those in areas with higher temperatures in the south, pay attention to. The factors that affect the water retention effect of dry mortar include the amount of MC added, the viscosity of MC, the fineness of particles and the temperature of the environment in which it is used.
1. Concept
Cellulose ethers are a synthetic high molecular polymer made from natural cellulose through chemical modification. Cellulose ether is a derivative of natural cellulose. The production of cellulose ether is different from synthetic polymers. Its most basic material is cellulose, a natural polymer compound. Due to the special structure of natural cellulose, cellulose itself has no ability to react with etherifying agents. However, after the treatment of the swelling agent, the strong hydrogen bonds between the molecular chains and within the chain are destroyed, and the active release of the hydroxyl group becomes alkali cellulose with reactive ability. After the reaction of the etherifying agent, the -OH group is converted into the -OR group. Obtain cellulose ether.
The properties of cellulose ether depend on the type, quantity and distribution of substituents. The classification of cellulose ethers is also based on the types of substituents, the degree of etherification, solubility and related applications. According to the type of substituents on the molecular chain, it can be divided into monoethers and mixed ethers. The MC we usually use is monoether, and Cellulose Ether HPMC is mixed ether.
In terms of solubility, it can be divided into ionic and non-ionic. Water-soluble non-ionic cellulose ethers are mainly composed of two series of alkyl ethers and hydroxyalkyl ethers. Ionic CMC is mainly used in synthetic detergent textile printing and dyeing food and petroleum exploitation. Non-ionic MC,
HPMC, HEMC, etc. are mainly used in building materials, latex coatings, medicine, daily chemistry, etc. Used as a thickener, water-retaining agent, stabilizer, dispersant, and film-forming agent.
2.Water retention of cellulose ether
Water retention of cellulose ether: in the production of building materials, especially dry mortar, cellulose ether plays an irreplaceable role, especially in the production of special mortar (modified mortar), it is an indispensable and important part .
The important role of water-soluble cellulose ether in mortar is mainly in three aspects, one is excellent water retention capacity, the other is the influence on the consistency and thixotropy of mortar, and the third is the interaction with cement. The water retention effect of cellulose ether depends on the water absorption of the base layer, the composition of the mortar, the layer thickness of the mortar, the water demand of the mortar, and the setting time of the coagulating material. The water retention of cellulose ether itself comes from its solubility and dehydration. It is well known that although the cellulose molecular chain contains a large number of highly hydratable OH groups, it is not soluble in water itself. This is because the cellulose structure has a high degree of crystallinity.
