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. For particle size, the finer the particle, the better the water retention. After the large particles of cellulose ether come into contact with water. The surface dissolves immediately to form a gel, which wraps the material to prevent the continuous infiltration of water molecules. It greatly affects the water retention effect of its cellulose ether. And solubility is one of the factors for choosing cellulose ether.
Fineness is also an important performance indicator of HPMC. The HPMC used for dry powder mortar is required to be powder, with low water content. And the fineness also requires 20% to 60% of the particle size to be less than 63um. Fineness affects the solubility of HPMC. Coarse HPMC is usually granular, and it is easy to dissolve in water without caking. But the dissolution rate is very slow, so it is not suitable for use in dry mortar.
In dry powder mortar, HPMC is dispersed among cementitious materials such as aggregates, fine fillers and cement. Only fine enough powder can avoid HPMC agglomeration when mixing with water. When HPMC is added with water to dissolve the agglomerates, it is difficult to disperse and dissolve. MC with coarser fineness is not only wasteful. But also reduces the local strength of the mortar. When such dry powder mortar is constructed in a large area, the curing speed of the local dry powder mortar is significantly reduced, and cracking occurs due to different curing times.
For the spray mortar using mechanical construction, due to the shorter stirring time, the fineness is required to be higher. 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.
Talking about Hydroxypropyl Methyl Cellulose Ether (HPMC) for Dry Powder Mortar(1)
Talking about Hydroxypropyl Methyl Cellulose Ether (HPMC) for Dry Powder Mortar(3)
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