Hydroxypropyl methyl cellulose HPMC is used as a dispersant, thickener and binder in construction treatment, and is mainly used in the molding of cement mortar and gypsum products. It is used in cement mortar to increase its adhesion, reduce flocculation, improve viscosity and shrinkage, and have water retention. Reduce the moisture loss and strength of the concrete surface, prevent cracks and weathering of water-soluble salts; hydroxypropyl methylcellulose HPMC has thixotropy and can be formulated for low-fluidity, one-time thick coating of mortar paint on vertical walls; HPMC has improved adhesion and construction performance, so it is suitable for the preparation of easy-flowing spraying mortar for thin-layer painting.
The amount of hydroxypropyl methyl cellulose HPMC in building materials is very small, only 0.1% to 1%, but its effect is great. It can be used as a plasticizer, tackifier, and water-retaining agent for paint, plaster, mortar and cement products Agents, air-entraining agents and retarders, play a role in increasing its workability, water retention or adhesion with the base layer. In addition, it is also in response to environmental protection requirements. When dry mixing mortar, it avoids unstable performance and pollution to the surrounding environment caused by on-site mixing, poor construction environment, and low flow efficiency. In the past, tile adhesives and putty for interior and exterior walls used 107 adhesives. From an environmental perspective, it is ideal to use cellulose ethers, such as HEC and HPMC.
Cement has good bonding performance, but the bonding performance of cement mortar and cement mortar is significantly different due to the performance difference between the bonding layer and the bonded surface during the construction process. When the water absorption performance of the bonding surface is large, it will Causes the dehydration of the bonding surface, the plasticity of the cement mortar is greatly reduced, the adhesion force is reduced, and the bonding strength is greatly reduced. In the past, gypsum or 107 glue was added to the cement mortar, but there are still defects such as inadequate measurement and cumbersome construction techniques. The viscosity-increasing effect of cellulose ether in water and weak alkali.
The effects of adding cellulose ether include:
1. Improve the initial and final setting time of cement;
2. Improve the stress of cement mortar;
3. Improve the water retention capacity of cement and gypsum;
4. The compressive and shear strength of cement mortar is reduced;
5. Improve the bonding performance of mortar.