The greater the viscosity of the cellulose ether, the better the water retention performance. Viscosity is an important parameter of MC performance. At present, different HPMC manufacturers use different methods and instruments to determine the viscosity of MC.
The main methods are Haake Rotovisko, Hoppler, Ubbelohde, and Brookfield. For the same product, the viscosity results measured by different methods are very different, and some are even doubled. Therefore, when comparing the viscosity, it must be done between the same test methods, including temperature, rotor, etc.
Generally speaking, the higher the viscosity, the better the water retention effect. However, the higher the viscosity, the higher the molecular weight of HPMC and its dissolution performance will be correspondingly reduced, which has a negative impact on the strength and construction performance of the mortar.
The higher the viscosity, the more obvious the thickening effect on the mortar, but it is not proportional. The higher the viscosity, the more viscous the wet mortar will be, which is manifested by the sticking of the scraper and the high adhesion to the substrate during construction. But it does not help much to increase the structural strength of the wet mortar itself. During construction, the performance of anti-sagging performance is not obvious.
On the contrary, some modified methyl cellulose ethers with medium and low viscosity have excellent performance in improving the structural strength of wet mortar. The greater the amount of cellulose ether added to the mortar, the better the water retention performance, and the higher the viscosity, the better the water retention performance.