How to improve the water retention of HPMC?

How to improve the water retention of HPMC?

 

 

HPMC is one of the most commonly used additives in dry mortar, and it also plays an important role in dry mortar. After the HPMC in the mortar is dissolved in water, the surface activity ensures that the cementitious material is effectively and uniformly distributed in the system, and HPMC as a protective colloid, "encapsulates" the solid particles and forms a layer of lubrication on its outer surface. The film makes the mortar system more stable, and also improves the fluidity of the mortar during the mixing process and the smoothness of the construction.

 

 

How to improve the water retention of HPMC

 

 

 

Maissen's HPMC has excellent water retention, which can prevent the premature evaporation of water in the wet mortar or be absorbed by the base layer, ensure that the cement is fully hydrated, and thus ultimately guarantee the mechanical properties of the mortar, which is especially beneficial for thin-layer mortar and water absorption The base layer or the mortar applied in high temperature and dry conditions. The water retention effect of Maissen's HPMC can change the traditional construction process and improve the construction progress. For example, plastering can be carried out without pre-wetting on the water-absorbing substrate.

 

 

 

The viscosity, dosage, ambient temperature and molecular structure of HPMC have a great influence on its water retention performance. Under the same conditions, the higher the viscosity of HPMC, the better the water retention; the higher the dosage, the better the water retention. Usually, a small amount of HPMC can greatly improve the water retention rate of the mortar. When the dosage reaches a certain level, the water retention The water retention rate of HPMC tends to increase slowly; as the ambient temperature increases, the water retention of HPMC generally decreases, but HPMC of Maissen has better water retention at high temperature, and cellulose ethers with lower degrees of substitution have better water retention performance.

 

The hydroxyl group on the HPMC molecule and the oxygen atom on the ether bond will associate with the water molecule to form a hydrogen bond, so that the free water becomes bound water, which has a good water retention effect; the mutual diffusion between the water molecule and the cellulose ether molecular chain The action allows water molecules to enter the interior of the HPMC macrochain, and is subject to strong binding force, thereby forming free water and entangled water, which improves the water retention of the mud; HPMC improves the rheological properties and porous network structure of the fresh cement paste. and osmotic pressure or the film-forming properties of HPMC hinder the diffusion of water. However, the current HPMC has poor water retention performance, which makes the mortar poor in adhesion and poor in construction performance. After construction, the mortar is prone to cracking, hollowing and falling off.


article from website: https://www.chinahpmccellulose.com/cellulose/hpmc/