The water-retention function and principle of hydroxypropyl methyl cellulose HPMC:
Cellulose ether HPMC in cement mortar and gypsum base slurry, mainly to protect water and thickening effect, can effectively improve the bonding strength and sag resistance.
Air temperature, temperature and wind pressure can affect the moisture content of cement mortar and gypsum base. Therefore, in different seasons, adding HPMC the same amount of product water conservation effect there are some differences. In the concrete construction, we can adjust the water retention effect of the slurry by adding and subtracting the amount of HPMC. The water retention of methyl cellulose ether under high temperature condition is an important index to distinguish the quality of methyl cellulose ether. Excellent HPMC products can effectively solve the problem of water conservation under high temperature. High quality HPMC is needed to improve the water retention of the slurry in the high temperature season, especially in the hot and dry areas and the thin layer construction of the surface. High-quality hpmc with very good uniformity, its methoxy and hydroxypropyl chi groups are evenly distributed along the chain of cellulose molecules, can improve the hydroxyl and ether bond oxygen atom and water association to form hydrogen bonding capacity, so that free water into a combination of water, so as to effectively control the high temperature caused by the evaporation of water, to reach a high moisture retention.
High-quality cellulose hpmc can be evenly and effectively dispersed in cement mortar and gypsum base products, and wrap all the solid particles, and form a layer of wetting film, the water in the base is gradually released over a long period of time, and inorganic cementitious material hydration reaction, thus ensuring the bonding strength and compressive strength of the material. Therefore, in the high temperature in the summer construction, in order to achieve water conservation effect, the need to add high quality of HPMC products in accordance with the formula, otherwise, will appear dry too fast and caused by insufficient hydration, strength reduction, cracking, hollowing and shedding quality problems, but also increase the difficulty of construction workers. As the temperature decreases, the added amount of HPMC can be reduced gradually, and the same water retention effect can be achieved.
The water retention of hydroxypropyl methyl cellulose HPMC products is affected by temperature and the following factors:
1. Uniformity of cellulose ether HPMC
The homogeneous reaction of HPMC, methoxy and hydroxypropyl oxygen is evenly distributed and the water retention rate is high.
2. Cellulose ether HPMC Thermal gel temperature
The coagulation gum temperature is high, the water retention rate is high, conversely, the water retention rate is low.
3. Cellulose ether HPMC viscosity
When the viscosity of HPMC increases, the water retention rate increases, and when the viscosity reaches a certain degree, the increase of water retention rate tends to be gentle.
4. Cellulose ether HPMC added amount
The greater the amount of cellulose ether hpmc, the higher the water retention rate, the better the water retention effect. In the range of 0.25-0.6%, the water retention rate increases rapidly with the increase of adding quantity, and the increasing trend of water retention rate is slowed down when the added amount increases.