HPMC and putty powder

1. What is the main function of the application of HPMC in putty powder? Is there any chemical reaction?

——Answer: In the putty powder, HPMC plays three roles of thickening, water retention and construction. Thickening: Cellulose can be thickened to suspend and keep the solution uniform up and down, and resist sagging. Water retention: make the putty powder dry slowly, and assist the ash calcium to react under the action of water. Construction: Cellulose has a lubricating effect, which can make the putty powder have good construction. HPMC does not participate in any chemical reactions, but only plays an auxiliary role. Adding water to the putty powder and putting it on the wall is a chemical reaction, because new substances are formed. If you remove the putty powder on the wall from the wall, grind it into powder, and use it again, it will not work because new substances (calcium carbonate) have been formed. ) too. 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 The role of ash calcium in CO2 in water and air Under this condition, calcium carbonate is generated, while HPMC only retains water, assisting the better reaction of ash calcium, and does not participate in any reaction itself.

2. What is the amount of HPMC added in the putty powder?

——Answer: The amount of HPMC used in practical applications varies depending on the climate, temperature, quality of local ash calcium, formula of putty powder and “quality required by customers”. Generally speaking, between 4 kg and 5 kg. For example: most of the putty powder in Beijing is 5 kg; most of the putty powder in Guizhou is 5 kg in summer and 4.5 kg in winter; the amount of putty in Yunnan is relatively small, generally 3 kg to 4 kg, etc.

3. What is the proper viscosity of HPMC in putty powder?

——Answer: Generally, 100,000 yuan is enough for putty powder, and the requirements for mortar are higher, and 150,000 yuan is required for easy use. Moreover, the most important function of HPMC is water retention, followed by thickening. In the putty powder, as long as the water retention is good and the viscosity is low (70,000-80,000), it is also possible. Of course, the higher the viscosity, the better the relative water retention. When the viscosity exceeds 100,000, the viscosity will affect the water retention. Not much anymore.

4. Why does the putty powder foam?

——Answer: Phenomenon: bubbles are generated during the construction process and after a period of time, the surface of the putty is blistered.

cause:

1. The base is too rough and the plastering speed is too fast;

2. The putty layer in one construction is too thick, greater than 2.0mm;

3. The moisture content of the grassroots is too high, and the density is too large or too small.

4. After a period of construction, the bursting and foaming on the surface is mainly caused by uneven mixing, while HPMC plays a role in water retention, thickening and improving workability in the putty powder, and does not participate in any reaction.

5. What is the reason for the powder removal of putty powder?

——Answer: This is mainly related to the amount and quality of gray calcium added. The low calcium content of gray calcium and the inappropriate ratio of CaO and Ca(OH)2 in gray calcium will cause powder removal. At the same time, it is also related to HPMC. The water retention rate is low, and the ash calcium hydration time is not enough, which will also cause powder removal.

6. Why is the putty heavy in the scraping process?

——Answer: In this case, the viscosity of the cellulose generally used is too high. Some manufacturers use 200,000 cellulose to make putty. The putty produced in this way has a high viscosity, so it feels heavy when scraping. The recommended amount of putty powder for interior walls is 3-5 kg, and the viscosity is 80,000-100,000.