HPMC (Hydroxypropyl Methylcellulose) is a multifunctional polymer material widely used in construction, pharmaceuticals, food, cosmetics and other fields. As a cellulose ether, HPMC has good solubility, thickening, film-forming and adhesive properties and is therefore made into different types to suit various application needs.

1. Classification by viscosity
HPMC is available in a wide range of viscosities and is usually expressed as the viscosity of a 2% aqueous solution in mPa·s (milliPascal seconds). According to different viscosity grades, HPMC can be divided into low, medium and high viscosity types.

Low viscosity HPMC: Low viscosity HPMC is mainly used in applications that require good fluidity and permeability, such as pharmaceutical injections and some food additives. It improves the uniformity of the solution without significantly increasing the viscosity of the liquid.

Medium viscosity HPMC: Medium viscosity HPMC is commonly used in building materials, coatings and some cosmetics. It can provide a moderate thickening effect, enhance the material’s adhesion and film-forming properties, while maintaining a certain fluidity.

High viscosity HPMC: High viscosity HPMC is often used in applications that require significant thickening and stabilization, such as sustained release agents for tablets and construction mortars. It can significantly increase the viscosity of the system at lower concentrations and form stable gels or films.

2. Classification by degree of substitution
The chemical properties of HPMC are closely related to their degree of substitution, which is the average number of hydroxypropyl and methyl substituents per glucose unit. Different degrees of substitution affect the solubility, gel temperature, and film-forming properties of HPMC.

Low-substitution HPMC: Low-substitution HPMC generally exhibits higher gel temperatures and has better solubility at low temperatures. This type is often used in applications requiring heat-sensitive properties, such as some special formulations in the pharmaceutical and food industries.

HPMC with medium degree of substitution: HPMC with medium degree of substitution has more balanced properties and is widely used in construction, coatings and cosmetics. Their gel temperature and solubility are moderate, allowing for stable performance in a variety of environments.

Highly substituted HPMC: Highly substituted HPMC has a lower gel temperature and is more likely to form gels or films at low temperatures. This type of HPMC is typically used in applications that require rapid gel or film formation at room or cryogenic temperatures, such as pharmaceutical capsule shells or food coatings.

3. Classification by solubility
The solubility of HPMC is affected by its substituent type and molecular weight, and can be divided into cold water soluble type and hot water soluble type.

Cold water soluble HPMC: This type of HPMC dissolves quickly in cold water to form a clear solution that is often used in paints, glues and building materials to provide an immediate thickening effect.

Hot water soluble HPMC: This type of HPMC needs to be dissolved in hot water, and the solution will form a transparent gel after cooling. Usually used in areas that require thermal stability, such as heat-sensitive coatings or food processing.

4. Classification by application areas
According to specific application fields, HPMC can also be divided into different types such as construction, pharmaceutical, food and cosmetics.

HPMC for construction: In the construction field, HPMC is mainly used in cement mortar, putty powder, gypsum products and tile adhesives. It can improve the water retention, crack resistance and construction performance of the material, while improving the surface quality after construction.

HPMC for pharmaceutical use: HPMC used in the pharmaceutical industry requires high purity, good solubility, non-toxic and harmless, and is often used as binders, sustained-release agents and capsule shells for tablets. It can adjust the release rate of drugs and improve the stability of drugs.

Food-grade HPMC: Food-grade HPMC needs to comply with food additive standards and is commonly used as thickeners, emulsifiers and stabilizers in food. It can improve the taste, stability and shelf life of food, and has good thermal stability.

HPMC for cosmetics: In cosmetics, HPMC is used as a thickener, emulsifier and film-forming agent in skin care products, shampoos, shower gels and other products. It can improve the viscosity, stability and use feel of the product, while being gentle and non-irritating to the skin.

5. Classification by special functions
In addition to the above classifications, HPMC can also be made into types with special properties according to specific functional requirements, such as waterproof type, high temperature resistance type, low ash type, etc.

Waterproof HPMC: This type of HPMC is used as a waterproofing agent in construction and coatings to improve the water resistance and weather resistance of the material and extend its service life.

High temperature resistant HPMC: High temperature resistant HPMC can be used to maintain stable performance in high temperature environments, such as in some industrial coatings and high temperature building materials.

Low-ash HPMC: This type of HPMC is particularly suitable for applications that require higher purity, such as pharmaceuticals and food additives, and can reduce ash residue.

The diversity of HPMC allows it to be adapted to different industrial needs. By adjusting its viscosity, degree of substitution and solubility, HPMC can be designed into products suitable for different applications, thereby playing an important role in construction, pharmaceuticals, food, cosmetics and other fields.