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The necessity of adding cellulose to mortar and gypsum-based products

December 16, 2021by admin0

Hydroxypropyl methylcellulose, abbreviated as HPMC. The appearance is white or almost white powder; the main purpose is to be a dispersant in the production of polyvinyl chloride, the main auxiliary for the preparation of PVC by suspension polymerization. In the construction process of the construction industry, it is mainly used in mechanized construction such as wall building, stucco decoration, and caulking; especially in decorative construction, it is used to paste ceramic tiles, marble, and plastic decoration, which has high bonding strength and can also reduce the amount of cement. . It is used as a thickener in the coating industry, which can make the layer bright and delicate, without powdering, and improve the leveling performance.

In cement mortar and gypsum-based slurry, hydroxypropyl methylcellulose mainly plays the role of water retention and thickening, which can effectively improve the adhesion and sag resistance of the slurry.

Air temperature, temperature and wind pressure and other factors will affect the evaporation rate of water in cement mortar and gypsum-based products. Therefore, in different seasons, the same amount of hydroxypropyl methylcellulose products have different water retention effects.

In the specific construction, the water retention effect of the slurry can be adjusted by increasing or decreasing the amount of HPMC added. Water retention under high temperature conditions is an important indicator to distinguish the quality of cellulose ethers.

In the high temperature season, especially in hot and dry areas and the thin layer construction on the sunny side, high-quality HPMC is needed to improve the water retention of the slurry.

Excellent hydroxypropyl methylcellulose series products can effectively solve the problem of water retention at high temperature.

High-quality HPMC with very good uniformity. Its methoxy and hydroxypropoxy groups are evenly distributed along the cellulose molecular chain, which can improve the ability of oxygen atoms on the hydroxyl and ether bonds to form hydrogen bonds with water. So that free water becomes combined water, which effectively controls the evaporation of water caused by high temperature weather and achieves high water retention.

In order to coagulate cementitious materials such as cement and gypsum, water is needed for hydration. The correct amount of HPMC can maintain the moisture in the mortar for a long enough time so that the setting and hardening process can continue.

The amount of HPMC required to obtain sufficient water retention capacity depends on:

1. Absorption of the base

2. Composition of mortar

3. Thickness of mortar

4. Water demand of mortar

5. Setting time of gelling material

High-quality hydroxypropyl methylcellulose can be uniformly and effectively dispersed in cement mortar and gypsum-based products, and wrap all solid particles, and form a layer of wetting film, the moisture in the base is gradually released over a long time , Hydration reaction with inorganic gelling material, so as to ensure the bonding strength and compressive strength of the material.

Therefore, in the high-temperature summer construction, in order to achieve the effect of water retention, high-quality HPMC products need to be added in accordance with the formula, otherwise, there will be insufficient hydration, strength reduction, cracking, hollowing and shedding due to excessive drying. The problem also increases the difficulty of construction for workers. As the temperature decreases, the amount of HPMC added can be gradually reduced, and the same water retention effect can be achieved.

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