The Importance of Water Retention of HPMC
April 24th 2024
Instant hydroxypropyl methyl cellulose (HPMC) is a non-ionic cellulose ether obtained from natural polymer material cellulose through a series of chemical processing. Hydroxypropyl methylcellulose (HPMC) is a white powder that dissolves in cold water to form a clear, viscous solution. It has the properties of thickening, binding, dispersing, emulsifying, film-forming, suspending, adsorbing, gelling, surface-active, retaining moisture and protecting colloids.
Water retention is an important property of hydroxypropyl methylcellulose HPMC, and it is also a property that many domestic wet-mix mortar manufacturers pay attention to. The factors that affect the water retention effect of wet-mixed mortar include the amount of HPMC added, the viscosity of HPMC, the fineness of particles and the temperature of the use environment.
The important role of hydroxypropyl methyl cellulose HPMC in mortar is mainly in three aspects, one is the excellent water retention capacity, the second is the effect on the consistency and thixotropy of the mortar, and the third is the interaction with the cement. The water retention effect of cellulose ether depends on the water absorption of the base layer, the composition of the mortar, the layer thickness of the mortar, the water demand of the mortar, and the setting time of the coagulating material. The higher the transparency of hydroxypropyl methylcellulose, the better the water retention.
Factors that affect the water retention of mortar include cellulose ether viscosity, addition amount, particle fineness and use temperature. The higher the viscosity of the cellulose ether, the better the water retention performance. Viscosity is an important parameter for HPMC performance. For the same product, the viscosity results measured by different methods are very different, and some even double the difference. Therefore, when comparing viscosity, be sure to do it 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 and the higher the molecular weight of HPMC, the corresponding reduction in its solubility, which has a negative impact on the strength and construction properties of the mortar. The higher the viscosity, the better the thickening effect of the mortar, but it is not proportional. The higher the viscosity, the more sticky the wet mortar will be. During construction, it will stick to the scraper and have high adhesion to the substrate. But it does little to increase the structural strength of the wet mortar itself. During construction, it shows anti-sagging performance. On the contrary, some low-viscosity but modified hydroxypropyl methyl cellulose has excellent performance in improving the structural strength of wet mortar.
The larger the amount of cellulose ether added in the mortar, the better the water retention performance, the higher the viscosity, the better the water retention performance. Fineness is also an important performance index of hydroxypropyl methylcellulose. The fineness of hydroxypropyl methylcellulose also has a certain influence on its water retention. Generally speaking, for hydroxypropyl methylcellulose with the same viscosity but different fineness, the finer the fineness under the same amount of addition. The water retention effect is better.
In wet-mixed mortar, the addition amount of cellulose ether HPMC is very low, but it can improve the construction performance of wet-mixed mortar and is a major additive that affects the construction performance of mortar. Reasonable selection of the correct hydroxypropyl methyl cellulose has a great influence on the improvement of the performance of wet-mixed mortar.
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