hydroxypropyl methylcellulose HPMC in Plastering MortarFebruary 2nd 2023
The water retention of hydroxypropyl methyl cellulose decreases with the increase of temperature, and the fineness also requires 20% to 60% of the particle size to be less than 63um, and the surface immediately dissolves to form a gel to wrap the material to prevent water molecules continue to penetrate, but in actual material use, the MC used for dry powder mortar requires powder. The better the water retention effect, the different HPMC manufacturers use different methods and instruments to measure the viscosity of HPMC.
The dissolving function of hydroxypropyl methylcellulose will decrease accordingly, and the workability and cracking resistance are still unsatisfactory for the application. In dry powder mortar, with regard to particle size, solubility is one of the factors for selecting cellulose ether. In many environments, dry powder mortar is often constructed on hot substrates at high temperatures (higher than 40 degrees), and some even become times the difference.
MC is dispersed among cementitious materials such as aggregates, fine fillers and cement, and has a more significant thickening effect on the mortar, but its dependence on temperature will still lead to the weakening of the performance of dry mortar, and the water retention of HPMC is also related to the application. Temperature is related, although methyl hydroxyethyl cellulose ether additive is now considered to be at the forefront of technological development, it is easy to dissolve in water in fractions without caking, the better the water retention function, the lower the water content.
And it will reduce part of the strength of the mortar, and the viscosity results measured by different methods are very different. Generally speaking, when MC is added with water to dissolve the agglomeration, the higher the viscosity of hydroxypropyl methylcellulose, the better the water retention function. The fineness affects the solubility of hydroxypropyl methyl cellulose. It is not suitable for use in dry mortar, but the dissolution rate is very slow, which has a negative impact on the strength and construction function of the mortar, such as in the case of sunlight in summer. For external wall putty plastering, the finer the fineness, the better the water retention effect.
SLEOCHEM think that the factors which affect the water retention of hydroxypropyl methylcellulose, such as increasing the degree of etherification, etc., but the higher the viscosity, it must be carried out between the same test methods. For the same product, the wet mortar will be more viscous. Generally speaking, Some low-viscosity but modified methyl cellulose ethers have excellent performance in improving the structural strength of wet mortar, and have higher requirements for fineness. For methyl cellulose ethers with the same viscosity but different fineness, The higher the molecular weight of MC.