Knowledge of building materials：hydroxypropyl methylcellulose(HPMC)

Hydroxypropyl methylcellulose(HPMC) is a cellulose variety whose output and consumption have been increasing rapidly in recent years. It is a non-ionic cellulose mixed ether made from refined cotton after alkalization, using propylene oxide and methyl chloride as etherification agent, through a series of reactions. The degree of substitution is generally 1.2~2.0. Its properties are different due to the different ratios of methoxyl content and hydroxypropyl content.
(1) The viscosity of hydroxypropyl methylcellulose(HPMC) is related to its molecular weight, and the larger the molecular weight, the higher the viscosity. Temperature also affects its viscosity, as temperature increases, viscosity decreases. However, its high viscosity has a lower temperature effect than methyl cellulose. Its solution is stable when stored at room temperature.
(2) The water retention of hydroxypropyl methylcellulose(HPMC)depends on its addition amount, viscosity, etc., and its water retention rate under the same addition amount is higher than that of methyl cellulose.
(3) Hydroxypropyl methylcellulose(HPMC)is stable to acid and alkali, 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 speed up its dissolution and increase its viscosity. Hydroxypropyl methylcellulose(HPMC)is stable to common salts, but when the concentration of salt solution is high, the viscosity of hydroxypropyl methylcellulose (HPMC)solution tends to increase.
(4) Hydroxypropyl methylcellulose(HPMC)can be mixed with water-soluble polymer compounds to form a uniform and higher viscosity solution. Such as polyvinyl alcohol, starch ether, vegetable gum, etc.