The Importance of Water Retention of HPMC
April 24th 2024
1. Problems that often occur in putty powder
Fast drying: This is mainly related to the amount of gray calcium powder added (too large, you can appropriately reduce the amount of gray calcium powder in the putty formula) and the water retention rate of the fiber, and it is also related to the dryness of the wall.
Peel and roll. This is related to the water retention rate. Low cellulose viscosity is prone to this situation or the addition amount is small.
Depowder of internal wall putty powder: This is related to the addition of gray calcium powder (the amount of gray calcium powder in the putty formula is too small or the purity of the gray calcium powder is too low, appropriately increase the amount of gray calcium powder in the putty powder formula) At the same time, it is also related to the amount and quality of cellulose, which is reflected in the water retention rate of the product. The water retention rate is low, and the gray calcium powder (the calcium oxide in the gray calcium powder is not fully converted to calcium hydroxide for hydration) time is not enough ,caused.
Foaming: This is related to the dry humidity and flatness of the wall, and also related to the construction.
Needle points appear. This is related to cellulose, which has poor film-forming properties. At the same time, impurities in the cellulose react slightly with gray calcium. If the reaction is violent, the putty powder will be in the state of tofu. It can’t be walled, and it has no cohesiveness. In addition, cellulose is mixed with carboxymethyl and other products.
Volcanic caves and pinholes appear: This is obviously related to the water surface tension of the hydroxypropyl methylcellulose aqueous solution. The surface tension of the hydroxyethyl aqueous solution is not obvious. It will be fine for light collection.
Putty is easy to crack and yellow after drying: This is related to the amount of gray calcium powder added. Too much gray calcium powder increases the hardness of the putty powder after drying. Only the hardness is not flexible and it is easy to crack, especially It is easier to crack when subjected to external forces. It is also related to the high content of calcium oxide in ash calcium powder.
Second, why the putty powder becomes thinner after adding water
Cellulose is used as a thickener and water-retaining agent for greasy. Due to the thixotropy of cellulose itself, the addition of cellulose in putty powder also causes putty to produce thixotropy after adding water. This thixotropy is caused by the destruction of the loosely combined structure of the components in the putty powder. This structure is produced at rest and disassembled under stress. That is to say, the viscosity decreases under stirring, and the viscosity recovers at rest.
3. Why is the putty heavier in the scraping process?
In this case, the viscosity of the cellulose generally used is too high. Some manufacturers use 200,000 to make putty. The putty made by doing this has a high viscosity, so it feels heavy when scraping. The recommended amount of putty for interior wall is 3-5 kg, and the viscosity is 80-100,000.
4. Why does cellulose feel different viscosity when using the same viscosity in winter and summer?
Due to the thermal gelation of the product, it is determined that the viscosity of the putty and mortar will gradually decrease as the temperature rises. When the temperature exceeds the product gel temperature, the product will precipitate out of the water and lose its viscosity. The room temperature in summer is generally above 30 degrees, which is much different from the temperature in winter, so the viscosity is lower. It is recommended to choose a product with a higher product viscosity or increase the amount of cellulose when applying the product in summer, and then choose a product with a high gel temperature. In summer, try not to use hydroxypropyl methyl cellulose. The glue temperature is around 55 degrees, and the temperature is slightly higher, its viscosity will be greatly affected.
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