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Sodium Carboxymethyl Cellulose CMC Ether Mechanism Of Action
Edit: Hangzhou Hongbo New Materials Co.,Ltd    Date: Nov 06, 2017

In the composition of dry mortar Sodium Carboxymethyl Cellulose CMC ether is a relatively low addition, but there are significant additives to improve mortar mixing and construction performance. To put it simply, almost all of the mortar wettability that can be seen with the naked eye is provided by cellulose ethers. It is a cellulose derivative obtained from the reaction of wood and cotton cellulose with caustic soda and then etherified with an etherifying agent.

Kind of Sodium Carboxymethyl Cellulose CMC ether

A. Hydroxypropyl Sodium Carboxymethyl Cellulose CMC (HPMC), the main choice of pure high-purity cotton as raw material, in the alkaline conditions made by the special etherification.

B. Hydroxyethylmethylcellulose (HEMC), a non-ionic cellulose ether, has a white appearance and is odorless and tasteless.

C. Hydroxyethyl cellulose (HEC), a non-ionic surfactant, white appearance, odorless and tasteless flowable powder.

The above are non-ionic cellulose ethers and also ionic cellulose ethers such as Sodium Carboxymethyl Cellulose CMC ether (CMC).

In the process of using dry mortar, since ionic cellulose (CMC) is unstable in the presence of calcium ions, it is seldom used in inorganic gelling systems using cement and hydrated lime as cementing materials. In some places in China, The use of modified starch as the main cementing material, Shuangfei powder filler made of some interior wall putty is the use of CMC as a thickener. However, due to this product is easy to moldy, but not water, it gradually eliminated by the market. At present, the main domestic use of cellulose ether is HPMC.

Cellulose ether in cement-based materials mainly as water-retaining agent and thickener.

Its water-holding effect prevents the substrate from absorbing moisture excessively and impedes the evaporation of moisture, thus ensuring that the cement hydrates with sufficient water. For example, wiping the surface with ordinary cement paste, the dry and porous substrate will quickly and largely absorb water from the slurry, and the cement slurry near the base will easily lose the water needed for hydration , So not only can not be formed on the surface of the bond strength of the cement gel, but also prone to tilt and water seepage, so that the surface of the slurry layer is easy to fall off. When the cast slurry is thin, it is also easy to form cracks in the entire slurry. Therefore, in the past wiping operation is usually the first wetting the substrate wetting, but this operation is not only laborious and time-consuming, and the quality of the operation is difficult to control.

In general, the water retention of the slurry increases with the increase of the content of cellulose ethers. The greater the viscosity of the added cellulose ether, the better the water retention.

In addition to water retention and thickening, cellulose ethers also affect other properties of cement mortar, such as retarding, air entrainment, and increased bond strength. Cellulose ethers slow down the process of cement setting and hardening, thereby increasing the operational time. Therefore, it is sometimes used as a coagulant.

With the development of dry mortar, cellulose ether has become an important cement mortar admixture. However, more varieties of cellulose ether specifications, the quality between the batches still fluctuate.


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