As one of the important cellulose ether admixtures in dry powder mortar, hydroxypropyl methylcellulose has many functions in mortar. The most important role of hydroxypropyl methylcellulose in cement mortar is water retention and thickening. In addition, due to its interaction with the cement system, it can also play an auxiliary role in entraining air, retarding setting, and improving tensile bond strength. effect.
The most important performance of hydroxypropyl methylcellulose in mortar is water retention. As a cellulose ether admixture in mortar, hydroxypropyl methylcellulose can be used in almost all mortar products, mainly because of its water retention. Generally speaking, the water retention of hydroxypropyl methylcellulose is related to its viscosity, degree of substitution and particle size.
Hydroxypropyl methylcellulose is used as a thickener, and its thickening effect is related to the degree of substitution, particle size, viscosity and degree of modification of hydroxypropyl methylcellulose. Generally speaking, the higher the degree of substitution and viscosity of cellulose ether, and the smaller the particles, the more obvious the thickening effect.
In hydroxypropyl methylcellulose, the introduction of methoxy groups reduces the surface energy of the aqueous solution containing hydroxypropyl methylcellulose, so that hydroxypropyl methylcellulose has an air-entraining effect on cement mortar. Introduce proper air bubbles in the mortar, due to the “ball effect” of the air bubbles,
The construction performance of the mortar is improved, and at the same time, the introduction of air bubbles increases the output rate of the mortar. Of course, the amount of air-entrainment needs to be controlled. Too much air-entrainment will have a negative impact on the strength of the mortar.
Hydroxypropyl methylcellulose will delay the setting process of cement, thereby slowing down the setting and hardening process of cement, and prolonging the opening time of mortar accordingly, but this effect is not good for mortar in colder regions.
As a long-chain polymer substance, hydroxypropyl methylcellulose can improve the bonding performance with the substrate after being added to the cement system under the premise of fully maintaining the moisture in the slurry.
To sum up, the properties of HPMC in mortar mainly include: water retention, thickening, prolonging setting time, entraining air and improving tensile bond strength, etc.
Post time: Apr-01-2023