Views: 0 Author: Site Editor Publish Time: 2020-06-12 Origin: Site
Thickening Function of Cellulose Ether
Cellulose ether gives the wet mortar excellent viscosity, can significantly increase the bonding ability of the wet mortar and the base layer, and improve the sag resistance of the mortar. It is widely used in plastering mortar, external wall insulation system and tile bonding mortar. The thickening effect of cellulose ether can also increase the homogeneity and anti-dispersion ability of freshly mixed cement-based materials, prevent the delamination, segregation and bleeding of mortar and concrete. It can be used in fiber concrete, underwater concrete and self-compacting concrete .
Cellulose ethers increase the viscosity of cement-based materials from the viscosity of cellulose ether solutions. The index of "viscosity" is usually used to evaluate the viscosity of the cellulose ether solution. The viscosity of the cellulose ether generally refers to a certain concentration (such as 2%) of the cellulose ether solution, at a specified temperature (such as 20 ℃) and shear Under the condition of speed (or rotation rate, such as 20 rpm), the viscosity value measured with a specified measuring instrument (such as a rotational viscometer).
Viscosity is an important parameter for evaluating the performance of cellulose ether. The higher the viscosity of the cellulose ether solution, the better the viscosity of the cement-based material, the better the adhesion performance to the substrate, and the stronger the resistance to sag and dispersion, but if If the viscosity is too high, it will affect the fluidity and operability of the cement-based material (such as the plastering knife during the construction of the plastering mortar). Self-leveling mortar and self-compacting concrete, which require high fluidity, require lower viscosity of cellulose ether.
In addition, the thickening effect of cellulose ether will increase the water demand of cement-based materials, thereby increasing the output of mortar.
The viscosity of the cellulose ether solution depends on the following factors:
Cellulose ether molecular weight (or degree of polymerization) and concentration, solution temperature, shear rate and test method.
1 The higher the degree of polymerization of cellulose ether, the greater the molecular weight, the higher the viscosity of its aqueous solution;
2 The higher the amount (or concentration) of cellulose ether, the higher the viscosity of its aqueous solution, but you should pay attention to choose the appropriate amount when using it, so as not to add too much, which will affect the working performance of mortar and concrete;
3 As with most liquids, the viscosity of the cellulose ether solution decreases with increasing temperature, and the higher the concentration of cellulose ether, the greater the influence of temperature;
4 The cellulose ether solution is usually a pseudoplastic body, which has the property of shear thinning. The greater the shear rate during testing, the lower the viscosity.
Therefore, the cohesion of the mortar will be reduced due to external forces, which is conducive to the scraping construction of the mortar, so that the mortar can have good workability and cohesion at the same time. However, the cellulose ether solution exhibits Newtonian fluid characteristics when the concentration is low and the viscosity is very small. When the concentration increases, the solution gradually exhibits pseudoplastic fluid characteristics, and the higher the concentration, the more obvious the pseudoplasticity.