Hydroxypropyl methyl cellulose gives wet mortar excellent viscity. Which can significantly increase the bonding ability of wet mortar and the base, improve the anti-sagging performance of mortar. And is widely used in plastering mortar, external wall insulation system and surface brick bonding mortar. The thickening effect of cellulose ether can also increase the homogeneity and dispersion resistance of newly mixed cement-based materials. Prevent the stratification, segregation and drainage of mortar and concrete, and can in fibrous concrete, underwater concrete and self-compacting concrete.
The increase of hydroxypropyl methyl cellulose in the viscosity of cement-based material comes from the viscosity of cellulose ether solution. The “viscosity” index is usually use to evaluate the viscosity of the cellulose ether so. With a specified measuring instrument (e. g., a rotating viscosity meter) at a specified temperature (e. g., 20℃) and a shear rate (or rotation rate, such as 20 rpm).
Viscosity is an important parameter to evaluate the performance of cellulose ether. The higher the viscosity of hydroxypropyl methyl cellulose solution, the better the viscosity of cement base material. The adhesive performance of the substrate, the stronger the sagging and dispersion ability, but if its viscosity is too large. It will affect the mobility and operability (such as plastering mortar construction sticky plaster knife). Therefore, the viscosity of cellulose ether used in dry mix mortar is usually 15,000~60,000 mPa.S-1, and the viscosity of self liquid plain mortar. Self-compacting concrete with high liquidity requirements will require lower cellulose ether.
The viscosity of the hydroxypropyl methyl cellulose solution depends on the following factors:
- Molecular weight (or polymerization) and concentration of cellulose ether, solution temperature, shear speed, and test method.
- The higher the polymerization degree of cellulose ether, the greater the molecular weight, the higher the viscosity of its aqueous solution;
- The higher the mixing amount (or concentration) of cellulose ether, the higher the viscosity of its aqueous solution. But attention should choose the appropriate mixing amount when using;
- Like most liquids. The viscosity of cellulose ether solution will decrease with the increase of temperature, and the higher the concentration of cellulose ether.