Hydroxypropyl methylcellulose (HPMC) is a non-ionic cellulose ether made from natural polymer material cellulose through a series of chemical processes. They are an odorless, tasteless and nontoxic white powder that swells into a clear or slightly cloudy colloidal solution in cold water. It has thickening, binding, dispersing, emulsifying, film-forming, suspending, adsorbing, gelling, surface active, moisture-retaining and protective colloid properties. Hydroxypropyl methylcellulose and methylcellulose can be used in building materials, paint industry, synthetic resin, ceramic industry, medicine, food, textile, agriculture, daily chemical and other industries.
Hydroxypropyl methylcellulose HPMC chemical equation:
[C6H7O2(OH)3-m-n(OCH3)m(OCH2CH(OH)CH3)n]x
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, and 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 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 under high temperature conditions 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 has very good uniformity. Its methoxyl and hydroxypropoxyl 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 wrap all solid particles, and form a wetting film, the moisture in the base is gradually released for a long time, and the inorganic glue The hydration reaction of the coagulated material will ensure 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.
The water retention of hydroxypropyl methylcellulose HPMC product itself is often affected by the following factors:
1. Uniformity of cellulose ether HPMC
Evenly reacted HPMC, methoxyl and hydroxypropoxyl are evenly distributed, and the water retention rate is high.
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 in water retention rate tends to be gentle.
4. Addition amount of cellulose ether HPMC
The greater the amount of cellulose ether HPMC added, the higher the water retention rate and the better the water retention effect. In the range of 0.25-0.6% addition, the water retention rate increases rapidly with the increase of the addition amount; when the addition amount further increases, the increase trend of the water retention rate slows down.