Hydroxypropyl Methylcellulose (HPMC) provides excellent water retention in mortar, significantly enhancing the bond between the mortar and the substrate while improving anti-sagging performance. As a result, it is widely used in plastering mortars, gypsum-based mortars, and external thermal insulation composite systems (ETICS). In addition, the thickening effect of HPMC reinforces the homogeneity and anti-washout ability of cementitious materials, effectively preventing segregation, bleeding, and delamination in mortar and concrete. This makes it suitable for fiber-reinforced concrete, underwater concrete, and self-compacting concrete applications.
The viscosity of HPMC is essentially the viscosity of the cellulose ether solution. “Viscosity” is commonly used as the key indicator to evaluate this property. It refers to the value measured under specific conditions—typically a defined concentration (e.g., 2%), a set temperature (e.g., 20°C), a fixed rotational speed (e.g., 20 rpm), and with a standardized instrument such as a rotational viscometer.
Viscosity is a critical parameter for assessing cellulose ether performance. The higher the viscosity of the HPMC solution, the stronger its thickening effect on cementitious materials, the better its adhesion to the substrate, and the more effective its anti-sagging and anti-washout properties. However, excessive viscosity can negatively impact the flowability and workability of cementitious systems. To address various application needs, Kemox & Mixeon has developed a range of products. If you encounter any challenges during construction, feel free to contact us—we’re here to help. Additionally, the thickening action of HPMC increases the water demand of cementitious materials, which in turn improves mortar yield.
The viscosity of HPMC is influenced by the following factors:
- Degree of Polymerization and Molecular Weight: Higher polymerization and molecular weight result in higher solution viscosity.
- Dosage or Concentration: Increasing the dosage or concentration of HPMC leads to higher solution viscosity. However, careful dosage selection is necessary in practice to avoid negatively impacting the workability of mortar and concrete.
- Temperature: Like most liquids, the viscosity of HPMC solution decreases as temperature rises. The higher the concentration, the more pronounced the temperature effect.
- Shear Behavior: HPMC solutions are typically pseudoplastic and exhibit shear-thinning behavior. The higher the shear rate during measurement, the lower the measured viscosity.
Note: The viscosity of mortar temporarily decreases under applied force, which facilitates smooth troweling and allows the mortar to maintain both good workability and adequate consistency. At very low concentrations and viscosities, the cellulose ether solution behaves as a Newtonian fluid. As concentration increases, the solution gradually exhibits pseudoplastic fluid characteristics, with pseudoplasticity becoming more evident at higher concentrations.
