The difference between HPMC and CMC

Hydroxypropyl methylcellulose (HPMC), a popular gonioscopic solution, can cause discomfort and blurred vision. These side effects have been attributed to the preservative benzalkonium chloride (BAK). Carboxymethylcellulose (CMC), an unpreserved, viscous solution, might well provide adequate patient comfort and cushioning during gonioscopy without producing blur or irritation.

Water retention rate is the measure of how much water can be retained in a material. The key difference between carboxymethyl cellulose and hydroxypropyl methylcellulose is that carboxymethyl cellulose has a lower water retention rate, whereas hydroxypropyl methylcellulose has a higher water retention rate when compared in same amounts.

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.

There are many different uses of carboxymethyl cellulose, and a few of them include use in the food industry under the E number E466 as a viscosity modifier or thickener and is helpful in stabilizing emulsions in various products such as ice cream. Moreover, this substance is included in many non-edible products, including toothpaste, laxatives, diet pills, water-based paints, detergents, textile sizing, paper products, etc.

Among many uses of Hypromellose, the most common applications include using it as tile adhesives, cement renders, gypsum products, pharmaceutical, paints and coatings, food, cosmetics, detergents and cleaners, eye drops, etc.

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