The water retention from hydroxypropyl methylcellulose is one of the important properties of hydroxypropyl methylcellulose. Factors such as air temperature, temperature and wind pressure speed will affect the volatilization rate of water in cement mortar and gypsum-based products. Therefore, in different seasons, there are some differences in the water retention effect of products with the same amount of hydroxypropyl methylcellulose added.
Generally, the higher the viscosity of hydroxypropyl methylcellulose, the better the water retention effect will be, but the effect of viscosity on water retention will be reduced when the viscosity exceeds 100,000 mpa.s. For hydroxypropyl methylcellulose with a viscosity of more than 100,000, it is necessary to increase the amount of hydroxypropyl methylcellulose to significantly increase the water retention rate.
In the specific construction, the water retention effect of the slurry can be adjusted by increasing or decreasing the amount of hydroxypropyl methylcellulose. Hydroxypropyl methylcellulose series products can effectively solve the problem of water retention under high temperature. In high temperature seasons, especially in hot and dry areas and thin-layer construction on the sunny side, high-quality hydroxypropyl methylcellulose is required to improve the water retention of the slurry.
High-quality hydroxypropyl methylcellulose has very good uniformity. Its methoxyl and hydroxypropoxyl groups are evenly distributed along the cellulose molecular chain. It can improve the oxygen atoms on the hydroxyl and ether bonds. The ability of water association to form hydrogen bonds turns free water into bound water, thereby effectively controlling water evaporation caused by high-temperature weather and achieving high water retention.
High-quality hydroxypropyl methylcellulose can evenly and effectively disperse in cement mortar and gypsum-based products, wrap all solid particles, and form a moist film, and the moisture in the base will be released gradually over a long period of time. A hydration reaction occurs with the inorganic gelling material, thereby ensuring the bond strength and compressive strength of the material. Therefore, in high-temperature summer construction, in order to achieve the water retention effect, it is necessary to add high-quality hydroxypropyl methylcellulose products in sufficient quantities according to the formula, otherwise, insufficient hydration, reduced strength, and cracking will occur due to excessive drying. Quality problems such as hollowing, hollowing and falling also increase the difficulty of construction for workers. As the temperature drops, the amount of hydroxypropyl methylcellulose added can be gradually reduced, and the same water retention effect can be achieved.