Hydroxypropyl methyl cellulose is a cellulose variety with rapidly increasing production and consumption. It is a non-ionic cellulose mixed ether made from refined cotton through a series of reactions after alkalization, using propylene oxide and methyl chloride as etherification agents. The degree of substitution is generally 1.2~2.0. Its properties are different due to the proportion of methoxy content and hydroxypropyl content.
1. Hydroxypropyl methyl cellulose is easy to dissolve in cold water, but it is difficult to dissolve in hot water. However, its gel temperature in hot water is significantly higher than that of methyl cellulose. The solubility in cold water is also greatly improved than that of methyl cellulose.
2. The viscosity of HPMC is related to its molecular weight, and the viscosity is high when its molecular weight is large. Temperature will also affect its viscosity. As the temperature increases, the viscosity decreases. However, the effect of high viscosity and temperature is lower than that of methyl cellulose. Its solution is stable when stored at room temperature.
3. The water retention of HPMC depends on its dosage, viscosity, etc. The water retention rate of HPMC at the same dosage is higher than that of MC.
4. Hydroxypropyl methyl cellulose is stable to acids and bases, and its aqueous solution is very stable in the range of pH=2-12. Caustic soda and lime water have little effect on its performance, but alkali can accelerate its dissolution rate and improve its viscosity. Hydroxypropylmethylcellulose is stable to general salts, but when the concentration of salt solution is high, the viscosity of hydroxypropylmethylcellulose solution tends to increase.
5. Hydroxypropyl methyl cellulose can be mixed with water-soluble polymer compounds to form a uniform solution with higher viscosity. Such as polyvinyl alcohol, starch ether, vegetable gum, etc.
6. Hydroxypropyl methyl cellulose has better enzyme resistance than methyl cellulose, and the possibility of enzymatic degradation of its solution is lower than that of methyl cellulose.
7. The adhesion of hydroxypropyl methyl cellulose to mortar construction is higher than that of methyl cellulose.
