Hydroxypropyl methylcellulose is mainly used as a dispersant in the production of polyvinyl chloride, and is the main auxiliary agent for preparing PVC by suspension polymerization. In the construction process of the construction industry, it is mainly used in mechanized construction such as wall building, plastering, caulking, etc.; especially in decorative construction, it is used to paste ceramic tiles, marble, and plastic decorations. It has high bonding strength and can reduce the amount of cement. . It is used as a thickener in the paint industry, which can make the layer bright and delicate, prevent powder removal, improve leveling performance, etc.
In cement mortar and gypsum-based slurry, hydroxypropyl methylcellulose mainly plays the role of water retention and thickening, which can effectively improve the cohesive force and sag resistance of the slurry. 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. In the specific construction, the water retention effect of the slurry can be adjusted by increasing or decreasing the amount of HPMC added. The water retention of methyl cellulose ether under high temperature conditions is an important indicator to distinguish the quality of hydroxypropyl methyl cellulose ether. Excellent 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 HPMC is required to improve the water retention of the slurry.
High-quality hydroxypropyl methylcellulose (HPMC) has very good uniformity. Its methoxy and hydroxypropoxy groups are evenly distributed along the cellulose molecular chain, which can increase the oxygen atoms on the hydroxyl and ether bonds. The ability to associate with water 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. Water is required for hydration in order to set cementitious materials such as cement and gypsum. The correct amount of HPMC can keep the moisture in the mortar for a long enough time so that the setting and hardening process can continue.
The amount of hydroxypropyl methylcellulose (HPMC) required to obtain adequate water retention depends on:
Absorbency of base layer
Composition of Mortar
Mortar layer thickness
Mortar water demand
The setting time of the cementitious material
Hydroxypropyl methylcellulose can be uniformly and effectively dispersed in cement mortar and gypsum-based products, and wrap all solid particles, and form a wetting film, the moisture in the base is gradually released over a long period of time, and it is compatible with inorganic The hydration reaction of the gelled material ensures 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 HPMC products in sufficient quantities according to the formula, otherwise, there will be insufficient hydration, reduced strength, cracking, hollowing and shedding caused by excessive drying. problems, but also increase the construction difficulty of workers. As the temperature drops, the amount of water HPMC added can be gradually reduced, and the same water retention effect can be achieved.
Post time: Apr-10-2023