What are the hard skills of HPMC in cement mortar?
In premixed mortar, only a little HPMC can significantly improve the performance of wet mortar, which shows that HPMC is a major additive affecting the construction performance of mortar.
Selection of different varieties, different viscosity, different particle size, different degree of viscosity and addition of hydroxypropyl methyl cellulose have different effects on the performance of dry mortar. At present, many masonry and plastering mortars have poor water retention performance. Slightly standing for a few minutes will lead to the separation of water slurry. So it is very important to add HPMC in cement mortar.
Next, let’s see in detail what hard skills HPMC has in cement mortar.
Hydroxypropyl methyl cellulose-water retention is an important property of methyl hydroxypropyl methyl cellulose.
In the production of building materials, especially dry mortar, HPMC plays an irreplaceable role, especially in the production of special mortar (modified mortar), it is an indispensable and important part.
The viscosity, content, ambient temperature and molecular structure of HPMC have great influence on its water retention. Under the same conditions, the higher the viscosity of HPMC, the better the water retention; the higher the content of HPMC, the better the water retention. Often, HPMC with little amount of HPMC can greatly improve the water retention of mortar. When the amount of HPMC reaches a certain level, the increasing trend of water retention becomes slower; when the ambient temperature rises, the water retention of cellulose ether usually decreases, but some modified hydroxypropyl ether can greatly improve the water retention of mortar. Methyl cellulose also has better water retention at high temperature, and hydroxypropyl methyl cellulose with lower degree of substitution has better water retention.
Oxygen atoms on hydroxyl and ether bonds of hydroxypropyl methyl cellulose molecules can associate with water molecules to form hydrogen bonds, which make free water become bound water, thus playing a good role in water retention. The interaction between water molecules and hydroxypropyl methyl cellulose molecular chains makes water molecules enter into the internal chain of hydroxypropyl methyl cellulose macromolecules and are strongly constrained, thus forming self-contained molecules. The water retention of cement slurry is improved by water and winding water. Hydroxypropyl methyl cellulose improves the rheological properties, porous network structure and osmotic pressure of fresh cement slurry, or the film forming property of hydroxypropyl methyl cellulose hinders the diffusion of water.