Factors Affecting Water Retention of Cellulose ether
The greater the viscosity of cellulose ether is, the better the water retention property will be. The viscosity is an important parameter of HPMC performance. At present, different HPMC manufacturers use different methods and apparatus to measure the viscosity of HPMC, and the main methods are Haake Rotovisko, Hoppler, Ubbelohde and Brookfield. For the same product, the results of the viscosity measured by different methods vary greatly, and some are even multiplied differences. Therefore, the comparison of the viscosity must be made by he same test method, including the temperature, rotor, etc.
In general, the higher the viscosity is, the better the water retention effects will be. However, When the viscosity and the molecular weight of HPMC are higher, its dissolution performance will be reduced accordingly, which has a negative impact on the strength and construction performance of mortar. The higher the viscosity is, the more obvious the thickening effects on the mortar will be, but it is not a proportional relationship. The higher the viscosity is, the more sticky the wet mortar will be. That is, it will show stickiness to the scraper and high adhesion to the substrate. But it is of little help for increasing the structural strength of the wet mortar itself. During construction, it shows that the anti-sag performance is not obvious. Conversely, some methyl cellulose ethers with low viscosity but after modification can have excellent performance in improving the structural strength of the wet mortar.
The greater the addition of cellulose ether in the mortar is, the better the water retention properties will be; the higher the viscosity is, the better the water retention properties will be.