High Water Retention Agent Construction Grade HPMC Used in Drymix MortarJune 7th 2023
There are different types of viscometers used to measure the viscosity of a cellulose ether solution. The widely adopted viscometers are: HoppIer falling ball viscometer, Haake rotation Rheometer and Brookfield rotation viscometer. The viscometer commonly used in China is NDJ series.
The viscometers adopted by different cellulose ether manufacturers are different in the market. With the same solution, testing in different viscometers, the outcome differs much, even thousands of times; Adopting same viscometer to test different concentrations of solution, the viscosity value can also differ thousands of times or even tens of thousands of times; Using same viscometer to test the same solution under different testing environments, the viscosity value also has a very big difference.
Viscosity is an important parameter of cellulose ether performance. The comparison of viscosity must be carried out with the same instrument, the same viscometer method and the same test environment.
Cellulose ether is easily affected by cellulase and microorganism. These microorganisms preferentially attack the unreplaced dehydrated glucose units, leading to hydrolysis leading to chain breakage and degradation. Etherified substituents provide protection for the main chain. Therefore, with the increase of Degree of Substitution or substitution uniformity, the stability of cellulose ether increases. The difference of the stability of cellulose ether replies on the degree of etherification and the uniformity of substitution.
Due to the difference of etherification degree and substitution uniformity of cellulose ether, the water retention rate of cellulose ether in dry mixed mortar products is different.
In actual application, mortar is often used in high temperature condition (above 35oC), and the temperature of substrates is high too. Due to the dual effect of weather and substrate, the water retention rate of mortar decreases, leading to rapid water loss and affecting the hydration of cement. The strength of mortar decreases, and the construction and cracking resistance are affected. In this case, cellulose ether with good water retention should be selected at high temperature.
The active ingredient of cellulose ether refers to the active component of cellulose ether. The higher the active component of cellulose ether is, the greater the effective amount it can be used in mortar, which is usually above 92% for quality cellulose ethers.