Q1.What are the main uses of hydroxypropyl methylcellulose (HPMC)?

HPMC is widely used in construction materials, coatings, synthetic resins, ceramics, medicine, food, textile, agriculture, cosmetics, tobacco, and other industries.

HPMC can be divided into: construction grade, food-grade, and pharmaceutical grade according to its use.

At present, most of the domestic ones are construction grade. In the construction grade, the amount of putty powder is large, about 90% is used for putty powder, and the rest is used for cement mortar and glue.

Q2. How many types of hydroxypropyl methylcellulose (HPMC) are there and what are the differences in their uses?

HPMC can be divided into instant and hot-soluble types.

The fast-soluble product is rapidly dispersed in cold water and disappears in the water. At this time, the liquid has no viscosity, because HPMC is only dispersed in water, not really dissolved.  About 2 minutes later, the viscosity of the liquid slowly becomes larger and forms a transparent viscous gel.

The instant soluble type has a wide range of applications and can be used in putty powder and mortar, as well as in liquid glue and paint.

Hot-soluble products, which are agglomerated in cold water. Disperses rapidly in hot water and disappears in hot water. When the temperature drops to a certain temperature, the viscosity slowly appears until it forms a transparent viscous gel.

Hot-soluble type can only be used in putty powder and mortar.

Q3.What are the dissolution methods of hydroxypropyl methylcellulose (HPMC)?

Hot water dissolution method: Since hydroxypropyl methylcellulose does not dissolve in hot water, initially HPMC can be dispersed evenly in hot water. Subsequently, it dissolves quickly when it cools down. Two typical methods are described as follows.

a. Put the required amount of hot water in the container and heat it to about 70℃. Gradually add hydroxypropyl methylcellulose with slow stirring, at first HPMC floats on the surface of the water. Then gradually form a slurry, and cool the slurry under stirring.

b. Add 1/3 or 2/3 of the required amount of water in the container and heat to 70°C. Disperse HPMC as described above to prepare a hot water slurry; then add the remaining amount of cold water to the hot water slurry and cool the mixture after stirring.

Powder mixing method: Mix HPMC powder with a large amount of other powdery substances and mix thoroughly with a mixer. Then add water to dissolve, then HPMC can be dissolved without agglomeration. Because each tiny corner, only a little HPMC powder, will be dissolved immediately when it meets water.

Q4.How to determine the quality of hydroxypropyl methylcellulose (HPMC) in a simple and intuitive way?

a. Whiteness: Although the whiteness does not determine whether HPMC is good or not and if the whitening agent is added in the production process, it will affect its quality. However, most of the good products have good whiteness.

b. Fineness: The fineness of HPMC is generally 80 mesh and 100 mesh, 120 mesh is less. The finer the fineness, the better it is in general.

c. Transmittance: put HPMC into the water, after forming a transparent colloid, look at its transmittance. The greater the transmittance, the better, indicating that the insoluble matter inside is less.

d. Specific gravity: the greater the specific gravity, the heavier the better. Specific gravity, generally because of the high content of hydroxypropyl inside, high hydroxypropyl content, the water retention to be better.

Q5.What are the main technical indexes of hydroxypropyl methylcellulose (HPMC)?

Most people are concerned about the hydroxypropyl content and viscosity. With the high content of hydroxypropyl, water retention is generally better. Viscosity, water retention, relative (rather than absolute) is also better. And viscosity, in the cement mortar is better to use some.

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