The most important characteristic of hydroxypropyl methylcellulose is its water retention capacity in building materials. Maintain sufficient water in the mortar for a long time to meet the workability, and water also plays a role of lubrication and mixing in the inorganic composition. In this way, the thin layer mortar is easy to be combed or the plaster mortar is easy to be leveled repeatedly. In addition, due to the addition of cellulose in the mortar, the wall does not need to be wetted, so it can be constructed more efficiently.
Due to the water retention effect of hydroxypropyl methylcellulose, the water retained by a certain amount of cellulose in the mortar has a long enough time to promote the continuous hydration of the cement and improve the adhesion of the mortar to the substrate.
The impact of all parties on water retention
The effect of hydroxypropyl methyl cellulose viscosity and content on water retention: the same content of hydroxypropyl methyl cellulose increases the water retention of mortar with the increase of viscosity; the increase of cellulose content and viscosity increase the water retention of mortar The rate increases. When the cellulose content exceeds 0.3%, the water retention rate of the mortar hardly changes and tends to be balanced.
Mortar water retention depends on the amount of cellulose: the water absorption of the substrate, the composition of the mortar, the thickness of the mortar layer, the water requirement of the mortar, the setting time of the binder and other factors determine the hydroxypropyl methylcellulose content in the mortar. Doping.
The method for determining the water retention rate of cellulose in mortar: The water retention rate depends on the total water required to keep the mortar mixed for a fixed period of time. In order to simulate the absorption substrate, the water retention rate was measured by the filter paper method and the vacuum filtration method.
The effect of etherification degree and temperature of hydroxypropyl methylcellulose on water retention: The solubility and temperature of cellulose in water depend on the degree of etherification. The higher the temperature, the lower the water retention, and the higher the degree of etherification of cellulose, the fiber The better the high-temperature water retention of the element.