Selection of Putty Powder
Release Time:
2020-12-22
Source:
Why does putty powder become thinner and thinner the more you stir it after adding water?
Cellulose is used as a thickening and water-retaining agent in putty formulations. Due to cellulose’s inherent thixotropic properties, its addition to the putty powder imparts thixotropy to the mixture upon hydration. This thixotropy arises from the disruption of the loosely bonded structural network among the components in the putty powder; such a structure forms under static conditions but disintegrates under applied stress. In other words, the viscosity decreases during mixing and recovers when the mixture is allowed to stand.
Why is the putty relatively heavy during the application and scraping process?
This situation typically occurs when the cellulose viscosity is too high. Some manufacturers use a product with a viscosity of 200,000 for putty, which results in a putty that feels heavy and sluggish during application due to its excessive viscosity. For interior wall putty, the recommended addition level is 3–5 kilograms, with a viscosity of 80,000–100,000.
Why does putty and mortar made with the same viscosity cellulose feel differently viscous in winter versus summer?
Due to the thermogelling properties of the product, its viscosity decreases gradually as temperature rises. Once the temperature exceeds the product’s gelation temperature, it will precipitate out of the water, thereby losing its viscosity. In summer, room temperatures typically exceed 30°C, a significant difference from winter temperatures, which is why the viscosity feels lower. It is recommended that, during summer applications, you either select a product with a higher viscosity grade or increase the dosage of cellulose ether. Alternatively, choose a product with a higher gelation temperature—preferably an MK-grade formulation, which generally has a gelation temperature above 70°C. Avoid using methyl cellulose in summer, as its gelation temperature is around 55°C; even a slight rise in temperature can substantially reduce its viscosity.
