Questions about You Should Know about HPMCMarch 23rd 2023
The viscosity of hydroxypropyl methylcellulose HPMC, which we usually say, refers to the result of its 2% aqueous solution at a temperature of 20 degrees Celsius. The viscosity of hydroxypropyl methyl cellulose is mainly divided into four categories: low viscosity, medium and low viscosity, medium viscosity and high viscosity. Different viscosities have different uses.
Low viscosity: 400 viscosity, mainly used for self-leveling mortar, but generally imported. Reasons: low viscosity, although poor water retention, but good leveling and high mortar density.
Medium and low viscosity: The viscosity is between 20,000 and 40,000. It is mainly used for tile adhesive, joint filler, anti-cracking mortar, thermal insulation bonding mortar, etc. Reasons: good constructability, less water addition, and high mortar density.
Medium viscosity: The viscosity is between 75000-100000, mainly used for putty. Reason: Good water retention. In the putty powder, HPMC plays three roles of thickening, water retention and construction.
High viscosity: The viscosity is between 150,000 and 200,000. It is mainly used for polystyrene particle thermal insulation mortar powder and vitrified microbead thermal insulation mortar. Reasons: The viscosity is high, the mortar is not easy to fall, and it sags, which improves the construction.
In the putty powder, HPMC plays three roles of thickening, water retention and construction. HPMC does not participate in any chemical reaction, 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 generated, remove the putty powder from the wall and grind it into a powder and reuse it. It will not work because new substances (calcium carbonate have been formed ).
For putty powder, HPMC with a viscosity of 100,000 is generally sufficient. The most important role of HPMC is to retain water, followed by thickening. In putty powder, as long as the water retention is good, the viscosity is lower (70,000 to 80,000), of course, the viscosity is higher, the relative water retention is better, when the viscosity exceeds 100,000, the effect of viscosity on the water retention is Not big.
Of course, the amount of HPMC used in practical applications is different depending on the climate environment, temperature, local gray calcium quality, formula of putty powder and “quality required by customers”. In areas with large temperature difference between summer and winter, it should be noted that it is recommended to use a relatively low viscosity in winter, which is more conducive to construction. Otherwise, the viscosity of cellulose will increase when the temperature is low, and the feel will be heavy when the batch is scraped.