The difference between HPMC and CMC
Hydroxypropyl methylcellulose (HPMC)
(1) HPMC is easily soluble in cold water, and it may be difficult to dissolve in hot water. However, its gelation temperature in hot water is significantly higher than that of methyl cellulose. The dissolution in cold water is also much better than methyl cellulose.
(2) The viscosity of HPMC is related to the molecular weight, and the viscosity is high when the molecular weight is large. The temperature also affects its viscosity, the temperature rises, and the viscosity decreases. Its solution is stable at room temperature.
(3) The water retention of HPMC depends on its addition amount, viscosity, etc., and its water retention rate under the same amount is higher than that of methyl cellulose.
(4) HPMC has stability to acid and alkali, and its aqueous solution is very stable in the range of pH=2~12. Caustic soda and lime water do not have much effect on their properties, but alkali accelerates their dissolution rate and increases viscosity.
(5) HPMC can be mixed with a water-soluble polymer compound to form a uniform, higher viscosity solution. Such as polyvinyl alcohol, starch ether, vegetable gum and the like.
(6) HPMC has better enzyme resistance than methyl cellulose, and its solution is less likely to be enzymatically degraded than methyl cellulose. Hydroxypropyl methylcellulose has higher adhesion to mortar than methyl cellulose.
Carboxymethyl cellulose (CMC)
(1) CMC has a large hygroscopicity, and the general condition storage will contain a large amount of water.
(2) The CMC aqueous solution does not produce a gel, and the viscosity decreases as the temperature rises. When the temperature exceeds 50 C, the viscosity is irreversible.
(3) Its stability is greatly affected by pH. Generally used in gypsum-based mortar, it can not be used in cement-based mortar. When it is highly alkaline, it loses its viscosity.
(4) Its water retention is much lower than HPMC. It has a retarding effect on the gypsum-based mortar and reduces its strength. However, the CMC price is significantly lower than HPMC.