In the composition of dry mortar, hydroxypropyl methylcellulose 13 is an important additive with a relatively low addition amount, but it can significantly improve the mixing and construction performance of mortar. Simply put, almost all the wet mixability of mortars visible to the naked eye is provided by cellulose ethers. It is a cellulose derivative obtained by reacting with caustic soda and etherifying with an etherifying agent using cellulose from wood and cotton. What types of cellulose ethers are there? 1. Hydroxypropyl methyl cellulose (HPMC) 2, hydroxyethyl methyl cellulose (HEMC) 3, hydroxyethyl cellulose (HEC) three are nonionic cellulose ethers. HPMC is a highly pure refined cotton as raw material, specially etherified under alkaline conditions; HEMC is a nonionic cellulose ether, the appearance is white powder, odorless and tasteless; HEC is nonionic Surfactant, white in appearance, odorless, odorless and easy to flow powder. The other is ionic cellulose ethers, such as carboxymethyl cellulose (CMC). In the use of dry mortar, since ionic cellulose (CMC) is unstable in the presence of calcium ions, it is rarely used in inorganic cementing systems using cement and slaked lime as the cementing material. In some places in China, some interior wall putty processed using modified starch as the main cementing material and Shuangfei powder as the filler uses CMC as a thickener, but since this product is prone to mold point, and it's not water-resistant, so it's gradually being eliminated from the market. Currently, the cellulose ether that is mainly used domestically is HPMC. Water retention and thickening properties of cellulose ethers Water retention: the hydroxyl group on the cellulose ether molecule and the oxygen atom on the ether bond will associate with the water molecule to form a hydrogen bond, so that the free water becomes binding water, which plays a good water retention role; the mutual diffusion between the water molecule and the cellulose ether molecular chain allows the water molecules to enter the cellulose ether macromolecular chain and is strongly bound, thus forming free water, entangling water, improving water Mud Cellulose ethers improve the rheological properties of freshly mixed cement slurry, porous network structure, and osmotic pressure or film-forming performance of cellulose ethers hinder the diffusion of water. Generally speaking, the water retention of cement slurry increases with the increase of cellulose ether content. The greater the viscosity of the added cellulose ether, the better the water retention. Thickening effect: Cellulose ether gives the wet mortar excellent viscosity, can significantly increase the bonding ability of wet mortar and the base layer, improve the sagging resistance of the mortar, and is widely used in plastering mortar, surface brick bonding mortar and exterior wall insulation system. The thickening effect of cellulose ether can also increase the dispersion resistance and homogeneity of freshly mixed materials, prevent material stratification, separation and bleeding, and can be used in fiber concrete, underwater concrete and self-compacting concrete. In addition to water retention and thickening, cellulose ethers also affect other properties of cement mortars, such as retarding coagulation, and increasing bond strength. Cellulose ethers are sometimes used as a coagulant, as the cement solidification hardening process slows down, thereby prolonging the operational time. With the development of dry mortar, cellulose ethers have become an important cement mortar admixture. However, there are many varieties and specifications of cellulose ethers, and there are still fluctuations in quality between batches. You also need to pay attention to when using it: 1. The working characteristics of modified mortar are closely related to the viscosity development of cellulose ethers. Although products with high nominal viscosity, the final viscosity is relatively large, but due to slow dissolution, it takes a long time to obtain the final viscosity; in addition, cellulose ethers with thicker particles also take longer to obtain the final viscosity, so products with larger viscosity must obtain better working characteristics. 2. Due to restrictions on the polymerization of cellulose ethers raw materials, the maximum viscosity of cellulose ethers is also limited. 3. It is necessary to take good care of the purchase, production process and factory inspection to avoid quality fluctuations.