Generally speaking, the higher the viscosity, the better the water retention effect. However, the higher the viscosity, the higher the molecular weight of MC, and its solubility will be reduced accordingly, which has a negative impact on the strength and construction performance of mortar. The higher the viscosity, the more obvious the thickening effect on the mortar, but it is not a positive relationship. The higher the viscosity, the stickier the wet mortar will be, both in construction, as shown by the sticky scraper and the high adhesion to the substrate. However, it does not help much to increase the structural strength of the wet mortar itself. That is, when constructing, it shows that the anti-sagging performance is not obvious. On the contrary, some low to medium viscosity but modified methyl cellulose ethers have excellent performance in improving the structural strength of the wet mortar.
The water retention of HPMC is also related to the temperature of use, and the water retention of methyl cellulose ether decreases with the increase of temperature. However, in practical material applications, many environments dry mortars are often applied at high temperatures (above 40 degrees) on hot substrates, such as exterior wall putty plasters in summer with sunny conditions, which often accelerates the curing of the cement and the hardening of the dry mortar. This decrease in water retention leads to a perceptible decrease in workability and cracking resistance, and it is particularly important to reduce the influence of temperature in such conditions. In this regard, methyl hydroxyethyl cellulose ether additives are currently considered to be at the forefront of technological development. Despite the increase in the amount of MC (summer formulation), the workability and cracking resistance are still not sufficient for the application. The water retention effect of MC can be kept better at higher temperature by some special treatment, such as increasing the degree of etherification, so that it can provide better performance under severe conditions.
Generally HPMC has gel temperature, which can be roughly divided into 60 type, 65 type and 75 type. For common ready-mixed mortar using river sand, it is better to use type 75 HPMC with high gel temperature. The amount of HPMC should not be too high, too high will increase the water requirement of mortar, but also sticky trowel, too long setting time, affecting the constructability. Different mortar products use different viscosity of HPMC, do not just use high viscosity HPMC.
Therefore, although hydroxypropyl methylcellulose products are good, but only when used well, the choice of suitable HPMC is the primary responsibility of the enterprise laboratory personnel. At present, there are many unscrupulous dealers in compounding HPMC, the quality is quite poor, the laboratory should do a good experiment when choosing a certain cellulose, to ensure the stability of mortar products, do not be greedy for cheap, causing unnecessary losses.
Landcel’s hydroxypropyl methylcellulose products are developed and experimented by professional researchers to ensure that the products meet the standards. High quality and high cost performance.