Soluble hydroxypropyl methyl cellulose (HPMC) is a kind of non-ionic cellulose ether, which is made from natural polymer cellulose through a series of chemical processing. Hypromellose (HPMC) is a white powder that dissolves in cold water to form a transparent, viscous solution. It has the properties of thickening, adhesion, dispersion, emulsification, film forming, suspension, adsorption, gelation, surface activity, water retention and colloid protection. Water retention is an important property of hypromellose HPMC, which is also concerned by many wet-mixed mortar manufacturers in China. The factors affecting the water retention of wet-mixed mortar include the amount of HPMC, the viscosity of HPMC, the particle size and the temperature of the environment. The hypromellose HPMC plays an important role in mortar in three aspects: its excellent water retention, its effect on mortar consistency and thixotropy, and its interaction with cement. The water-retaining function of cellulose ether depends on the water absorption of the base, the composition of mortar, the thickness of mortar, the water demand of mortar and the setting time of the setting material. The more transparent the hypromellose, the better the water retention.
The factors affecting the water retention of mortar include the viscosity of cellulose ether, the addition amount, the particle fineness and the service temperature. The greater the viscosity of cellulose ether, the better the water retention. Viscosity is an important parameter of HPMC performance. For the same product, measured by different methods of viscosity results vary greatly, and some even double the difference. Therefore, when comparing viscosity, must be in the same test method between, including temperature, rotor and so on. Generally speaking, the higher the viscosity, the better the water retention effect. However, the higher the viscosity is, the higher the molecular weight of HPMC is, the solubility of HPMC will decrease accordingly, which has a negative effect on the strength and construction performance of mortar. The higher the viscosity, the better the thickening effect of mortar, but it is not proportional to the relationship. The higher the viscosity, the more viscous the wet mortar will be, both for construction, the performance of sticking scraper and high adhesion to the substrate. But it is not helpful to increase the structural strength of wet mortar itself. Both construction, performance for anti-sagging performance. In contrast, some modified hypromellose with low to medium viscosity have shown excellent performance in improving the structural strength of wet mortars. The higher the content of cellulose ether in mortar, the better the water-holding property, the higher the viscosity and the better the water-holding property. Fineness is also an important performance indicator for hypromellose. The fineness of the hypromellose also has a certain impact on its water holding capacity. In general, for hypromellose with the same viscosity but different fineness, under the same addition amount, the finer the fineness, the better the water retention effect.
In wet-mixed mortar, the addition of cellulose ether HPMC is very low, but it can improve the construction performance of wet-mixed mortar. Proper selection of hypromellose has a great effect on the performance of wet-mixed mortar.
Post time: Jul-27-2023