Selection of HPMC viscosity when producing putty powder dry-mixed mortar?

Methyl cellulose MC and hydroxypropyl methyl cellulose (HPMC) have stable chemical properties, mildew resistance, and the best water retention effects, and are not affected by changes in pH value. It is not that the higher the viscosity, the better. The viscosity is inversely proportional to the bond strength. The higher the viscosity, the smaller the strength. The production of putty powder is generally between 50,000 and 100,000 viscosities. The external thermal insulation dry-mixed mortar is more suitable for 15-20 10,000 viscosity, mainly to increase leveling and construction, can reduce the amount of cement. Another effect is that the cement mortar has a solidification period, during which it needs to be cured and water needs to be kept moist. Due to the water retention effect of cellulose, the water required for cement mortar solidification is guaranteed from the water retention of cellulose, so the solidification effect can be achieved without maintenance.

Regarding the quality of cellulose, mainly the viscosity, it can be tested with a rotational viscometer, and can also be compared with a simple method. When comparing, take 1 gram of cellulose with the same viscosity, add 100 grams of water, put it in a disposable cup, and pour it in at the same time, and observe which one dissolves faster, has better transparency, and has a better thickening effect. The better the transparency, the less impurities.

Carboxymethyl cellulose CMC and sodium carboxymethyl starch (CMS) are relatively cheap. They are used in low-grade putty powder for interior walls. Used in insulating dry mixes. Because these cellulose will react with cement, calcium lime powder, gypsum powder, and inorganic binders.

Many people think that these celluloses are alkaline. Generally, cement and lime calcium powder are also alkaline, and they think they can be used in combination. However, CMC and CMS are not single elements. The chloroacetic acid used in the production process is acidic. The remaining substances in the process react with cement and lime calcium powder, so they cannot be combined. Many manufacturers have suffered great losses due to this, so attention should be paid.