Hydroxypropyl methylcellulose HPMC is a non-ionic cellulose ether made from natural polymer material cellulose through a series of chemical processing. They are an odorless, tasteless and nontoxic white powder that swells in cold water to a clear or slightly hazy colloidal solution. It has the properties of thickening, binding, dispersing, emulsifying, film-forming, suspending, adsorbing, gelling, surface-active, retaining moisture and protective colloid. Hydroxypropyl methylcellulose, methylcellulose can be used in building materials, coating industry, synthetic resin, ceramics industry, medicine, food, textile, agriculture, daily chemical and other industries.
The water retention effect and principle of hydroxypropyl methylcellulose HPMC
Cellulose ether HPMC mainly plays the role of water retention and thickening in cement mortar and gypsum-based slurry, which can effectively improve the cohesion and sag resistance of the slurry.
Factors such as air temperature, temperature and wind pressure 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 HPMC 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 at high temperature is an important indicator to distinguish the quality of methyl cellulose ether. Excellent HPMC 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 HPMC, with very good uniformity, its methoxy and hydroxypropoxy groups are evenly distributed along the cellulose molecular chain, which can improve the ability of the oxygen atoms on the hydroxyl and ether bonds to associate with water to form hydrogen bonds , so that free water becomes bound water, so as to effectively control the evaporation of water caused by high temperature weather and achieve high water retention.
High-quality cellulose HPMC can be uniformly and effectively dispersed in cement mortar and gypsum-based products, and encapsulates all solid particles, and forms a wetting film, and the moisture in the base is gradually released over a long period of time. The hydration reaction of the coagulating material occurs, thereby ensuring the bonding strength and compressive strength of the material. Therefore, in high temperature summer construction, in order to achieve the effect of water retention, it is necessary to add high-quality HPMC products according to the formula, otherwise, there will be insufficient hydration, strength reduction, cracking, hollowing and falling off caused by too fast drying. It also increases the difficulty of construction for workers. As the temperature decreases, the addition amount of HPMC can be gradually reduced, and the same water retention effect can be achieved.
The water retention of hydroxypropyl methylcellulose HPMC product itself is often affected by the following factors:
1. Cellulose ether HPMC homogeneity
The uniformly reacted HPMC has uniform distribution of methoxy and hydroxypropoxy groups and high water retention.
2. Cellulose ether HPMC thermal gel temperature
The higher the thermal gel temperature, the higher the water retention rate; otherwise, the lower the water retention rate.
3. Cellulose ether HPMC viscosity
When the viscosity of HPMC increases, the water retention rate also increases; when the viscosity reaches a certain level, the increase of the water retention rate tends to be gentle.
4. Cellulose ether HPMC addition amount
The larger the added amount of cellulose ether HPMC, the higher the water retention rate and the better the water retention effect. In the range of 0.25-0.6%, the water retention rate increases rapidly with the increase of the addition amount; when the addition amount further increases, the increasing trend of the water retention rate becomes slower.