The addition of hydroxypropyl methyl cellulose(HPMC) to the cementitious material has a thickening effect and the amount added determines the water requirement of the cementitious material and therefore affects the yield of the mortar.

Several factors affecting the viscosity of hydroxypropyl methyl cellulose(HPMC):

  1. The higher the degree of polymerisation of the cellulose ether, the higher its molecular weight and the higher the viscosity of the aqueous solution.
  2. The higher the intake (or concentration) of cellulose ether, the higher the viscosity of its aqueous solution, but attention needs to be paid to the selection of a suitable intake when applying it to avoid excessive intake, which affects the working characteristics of mortar and concrete.
  3. The same as most liquids, the viscosity of cellulose ether solution will fall with the rise of temperature, and the higher the concentration of cellulose ether, the greater the influence of temperature.
  4. Hydroxypropyl methyl cellulose(HPMC) solutions are usually pseudoplastic and have a shear thinning property; the higher the shear rate when tested, the lower the viscosity.

As a result, the cohesive properties of the mortar are reduced by external forces. This facilitates the scraping of the mortar and enables it to have good workability and cohesion at the same time.

Hydroxypropyl methyl cellulose(HPMC) solutions exhibit Newtonian fluid properties at very low concentrations and low viscosities. It is only at higher concentrations that the solution gradually exhibits pseudoplastic fluid properties, and the higher the concentration, the more pronounced the pseudoplasticity.