What is the difference between HPMC and MC?
MC is a kind of methyl cellulose, which is obtained by treating refined cotton with alkali and using MC as etherification agent through a series of reactions to generate cellulose ether.The degree of substitution is generally 1.6 to 2.0, depending on the solubility.Nonionic cellulose ether.
(1) the water retention of MC depends on the amount of addition, viscosity, particle fineness and dissolution rate.
In general, the amount of addition has the greatest influence on the water retention rate, and the viscosity level is not proportional to the water retention rate.The dissolution rate mainly depends on the surface modification degree and particle fineness of cellulose particles.
In the cellulose ether, methyl cellulose and hydroxypropyl methyl cellulose have higher water retention.
(2) MCis is soluble in cold water, not hot water.
Aqueous solutions are very stable in the pH range of 3 to 12.It has good compatibility with starch, guar gum and other surfactants.
(3) temperature change will seriously affect the water retention rate of MC.
Generally speaking, the higher the temperature, the worse the water retention effect.When the mortar temperature exceeds 40℃, the water retention of methyl cellulose will deteriorate significantly.
(4) MC has a significant impact on the workability and adhesion of mortar.
The adhesion here refers to the adhesive force felt between the tools used by workers and the wall substrate. MC adhesive force is an intermediate in cellulose ether products.
HPMC is hydroxypropyl methyl cellulose
, is refined cotton alkalization, with acetal oxide and methyl chloride etherification agent, through a series of reactions synthesis of non-ionic cellulose mixed ether.The degree of substitution is generally 1.2 to 2.0.
Its properties vary with the content of methoxy and hydroxypropyl.
(1) the solubility in cold water is much better than MC.
Hydroxypropyl methyl cellulose is easy to dissolve in cold water, not easy to dissolve in hot water.However, its gelation temperature in hot water was significantly higher than that of methyl cellulose.
(2) the viscosity of HPMC
is related to molecular weight.
When the viscosity is high and the molecular weight is high.Temperature also affects viscosity, increasing temperature and decreasing viscosity.However, its viscosity is lower than the temperature of methyl cellulose.
(3) hydroxypropyl methyl cellulose 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 their properties, but alkali accelerates their dissolution rate and increases their viscosity.Hydroxypropyl methyl cellulose has stability to common salts, but when the concentration of salt solution is higher, the viscosity of hydroxypropyl methyl cellulose solution tends to increase.
(4) water retention rate under the same dosage is higher than MC.
Hydroxypropyl methyl cellulose water retention depends on the amount of addition, viscosity and other factors,
(5) HPMCC can be mixed with water-soluble polymer compounds to form uniform high-viscosity solution.
Such as polyvinyl alcohol, starch ether, vegetable glue, etc.
(6) the adhesion of HPMC to mortar is higher than that of methyl cellulose.
(7) the enzymatic hydrolysis resistance of HPMC is better than that of methyl cellulose, and the possibility of enzymatic hydrolysis of HPMC solution is less than that of methyl cellulose.