What is the difference between HYDROXYPROPYL METHYLCELLULOSE HPMC and MC?HYDROXYPROPYL METHYL CELLULOSE|METHYL CELLULOSE
MC is methyl cellulose. After the refined cotton is treated with alkali, chloromethane is used as an etherifying agent, and a series of reactions are made to prepare cellulose ether. The degree of substitution is generally 1.6 to 2.0, and the degree of substitution differs depending on the solubility. It belongs to nonionic cellulose ether.
(۱) The water retention of methyl cellulose depends on the amount of addition, viscosity, particle fineness and dissolution rate. Generally, the amount of addition is large, the fineness is small, and the viscosity is large, and the water retention rate is high. The addition amount has the greatest influence on the water retention rate, and the viscosity level is not proportional to the water retention rate. The rate of dissolution depends mainly on the degree of surface modification of the cellulose particles and the fineness of the particles. Among the above cellulose ethers, methyl cellulose and hydroxypropyl methylcellulose have a high water retention rate.
(۲) mc is soluble in cold water, and it is difficult to dissolve in hot water. The aqueous solution is very stable in the range of pH=3~12. It has good compatibility with starch, guar gum and many other surfactants. When the temperature reaches the gelation temperature, a gelation phenomenon occurs.
(۳) The change of temperature will seriously affect the water retention rate of methyl cellulose. Generally, the higher the temperature, the worse the water retention. If the temperature of the mortar exceeds 40 ° C, the water retention of methyl cellulose will be significantly deteriorated, which seriously affects the workability of the mortar.
(۴) Methyl cellulose has a significant effect on the workability and adhesion of the mortar. “Adhesiveness” herein refers to the adhesive force felt between the worker’s application tool and the wall substrate, that is, the shear resistance of the mortar. The adhesion is large, the shear resistance of the mortar is large, the force required by the worker during use is also large, and the workability of the mortar is poor.
Methylcellulose adhesion is intermediate in cellulose ether products.
HPMC is hydroxypropylmethylcellulose, which is a nonionic cellulose mixed ether prepared by a series of reactions using acetal oxide and methyl chloride as an etherifying agent after alkalization of refined cotton. The degree of substitution is generally 1.2 to 2.0. Its nature is different depending on the ratio of methoxyl content and hydroxypropyl content.
(۱) Hydroxypropyl methylcellulose 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. –
(۲) The viscosity of hydroxypropylmethylcellulose is related to the molecular weight thereof, and the viscosity is high when the molecular weight is large. The temperature also affects its viscosity, the temperature rises, and the viscosity decreases. However, its viscosity has a lower temperature than methyl cellulose. Its solution is stable at room temperature.
(۳) hpmc 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 do not have much effect on their properties, but alkali accelerates their dissolution rate and increases viscosity. Hydroxypropyl methylcellulose has stability to general salts, but when the concentration of the salt solution is high, the viscosity of the hydroxypropyl methylcellulose solution tends to increase.
(۴) The water retention of hydroxypropyl methylcellulose depends on the amount of addition, viscosity, etc., and the water retention rate under the same amount is higher than that of methylcellulose.
(۵) Hydroxypropyl methylcellulose 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.
(۶) Hydroxypropyl methylcellulose has higher adhesion to mortar than methyl cellulose.
(۷) Hydroxypropyl methylcellulose has better enzymatic resistance than methylcellulose, and its solution is less likely to be enzymatically degraded than methylcellulose