In the past, attempts have been made to clarify the working mechanism of methyl cellulose (MC). Early works from Schweizer et al. present the effect of cellulose ethers on water retention and rheology of cementitious mortars and gypsum-based machinery plasters [15], [16]. They demonstrate that adsorption of methyl cellulose is clearly dependent on the degree of substitution (DS). At DS values of > 1.6 which are typical for MC products used in the building industry, only a minor amount (~ 20%) of the MC powder adsorbs. In a very skillful experiment the authors show that during the drying process of a gypsum-based render, MC migrates with the water to the surface of the render and is not retained by adsorption. Thus, they conclude that MC does not adsorb on the binder or its hydrates. Similar observations have been made by Yammamuro et al. [17].

The higher the clarity of hydroxypropyl methyl cellulose, the better the water solubility. The factors that affect the water solubility of wet cement mortar include the viscosity of cellulose ether, the addition amount, particle size and application temperature. The higher the viscosity of cellulose ether, the better the water solubility. Viscosity is the key parameter of HPMC. Compared with the same commodity, the viscosity measured in different ways is huge, tiny or even twice the distance. Therefore, in terms of viscosity, it is necessary to carry out in the same test standard. Including temperature, motor rotor, etc. Generally speaking, the higher the viscosity, the better the actual effect.
Hydroxypropyl methyl cellulose, known as “industrial monosodium glutamate”, is widely used. Hydroxypropyl methyl cellulose itself also has different types, which are divided into cold water instant type and hot-melt type. Cold water instant HPMC is widely used, and can be used in interior wall putty powder, cement mortar, liquid building paint, daily chemicals, etc. Heat soluble HPMC is generally used for dry powder products, which are directly mixed with dry powder, such as putty powder and mortar. Cold water instant products are inferior to hot-melt products in water retention and product stability, so different types should be selected according to different uses.
However, the higher the viscosity, the higher the HPMC content, and the lower the solubility of HPMC. This has a negative impact on the compressive strength and construction characteristics of cement mortar. The higher the viscosity, the more obvious the thickening effect of cement mortar. However, different from the ground, the higher the viscosity is, the higher the viscosity of cement mortar is. In addition to application, it will also show the information of self-adhesive knife and its high sensitivity to plates. But it is useless to improve the compressive strength of wet cement mortar itself.