Hydroxypropyl methylcellulose is one of the important cellulose ether additives in dry mortar and has multiple functions in mortar. The main functions of hydroxypropyl methylcellulose in cement mortar are water retention and thickening. In addition, due to its interaction with the cement system, it can also play a role in entraining air, retarding setting, and improving tensile bond strength. Influence.
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 properties. 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, the smaller the particle size and 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 an appropriate amount of bubbles into the mortar. Due to the “ball effect” of the bubbles,
The construction performance of the mortar is improved, while the introduction of air bubbles increases the yield of the mortar. Of course, the amount of entrained air needs to be controlled. When too much air is entrained, it can negatively affect the strength of the mortar.
Hydroxypropyl methylcellulose will delay the setting process of cement, slow down the setting and hardening process of cement, and extend the opening time of mortar accordingly. However, this effect is not good for mortar in colder areas.
As a long-chain polymer substance, hydroxypropyl methylcellulose can improve the bonding performance with the base material while fully maintaining the moisture content of the slurry when added to the cement system.
The main properties of HPMC in mortar include: water retention, thickening, extending setting time, air entrainment, improving tensile bond strength, etc.
Post time: Feb-06-2024