The relationship between the powder drop of putty powder and HPMC

Is there any relationship between the powder drop of putty powder and HPMC？

HPMC is widely used in building materials, coatings, synthetic resins, ceramics, medicine, food, textile, agriculture, cosmetics, tobacco and other industries. HPMC can be divided into: construction grade, food grade and pharmaceutical grade according to the application. At present, most of the domestic products are construction grade. In the construction grade, the amount of putty powder is very large, about 90% is used to make putty powder, and the rest is used for cement mortar and glue. In practical applications, the powder drop phenomenon of putty powder is a very common problem.

The powder drop of putty powder is mainly related to the quality of ash calcium, and has little to do with HPMC. The low calcium content of ash calcium and the inappropriate ratio of CaO and Ca(OH)2 in ash calcium will cause powder drop. If it has something to do with HPMC, then the poor water retention of HPMC will also cause powder loss. The specific reasons also include whether the chemical reaction of HPMC occurs in the putty powder.

What is the main function of HPMC in putty powder, and is there any chemical effect?

HPMC plays three roles in the putty powder, including thickening, water retention and construction. Thickening: Cellulose can be thickened to suspend, keep the solution uniform, and resist sagging. Water retention: Make the putty powder dry slowly, and assist the reaction of ash calcium under the action of water. Construction: Cellulose has a lubricating effect, which can make the putty powder have good workability. HPMC does not participate in any chemical reaction and only plays an auxiliary role. Putty powder added to the water wall is a chemical reaction. Because of the formation of new substances, take the putty powder on the wall off the wall, grind it into powder, and then use it again, it will not work, because new substances (calcium carbonate) have been formed. . The main components of ash calcium powder are: a mixture of Ca(OH)2,CaO and a small amount of CaCO3, CaO+H2O=Ca(OH)2—Ca(OH)2+CO2=CaCO3↓+H2O Ash calcium in water and air Under the action of CO2, calcium carbonate is generated, while HPMC only retains water and assists ash calcium to react better. It does not participate in any reaction itself, so the powder drop of putty powder has nothing to do with HPMC.

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Article editing：Easen Hao (easen@mailose.com)