Hydroxypropyl methylcellulose (HPMC) is a non-ionic cellulose ether widely used in many industries such as construction, medicine, food, cosmetics, coatings, ceramics, etc. It is a high molecular polymer obtained by chemical modification with natural cellulose as raw material. It has good water solubility, thickening, film-forming, adhesion, emulsification, lubricity and stability.

1. Solubility and water solubility
HPMC has excellent water solubility and can be quickly dissolved in cold water to form a transparent or slightly turbid colloidal solution. Its solubility is affected by the degree of substitution and molecular weight. Different types of HPMC may have different dissolution rates in water. In addition, HPMC can also be dissolved in certain organic solvents, such as ethanol, water and organic solvent mixtures.

2. Thermal gelation
HPMC has thermal gelation properties, that is, its aqueous solution will become a gel state at a certain temperature, and it can be dissolved again after cooling. HPMC with different viscosities and degrees of substitution has different gelation temperatures, usually between 50-90°C. This characteristic makes HPMC have important application value in the fields of architectural coatings, pharmaceutical excipients (such as sustained-release tablets), etc.

3. Viscosity and thickening
The viscosity of HPMC is one of its important physical properties, which depends on its molecular weight and concentration. Its aqueous solution has a higher viscosity at a lower concentration, so it can be used as a thickener. In building materials (such as mortar and putty powder), the thickening effect of HPMC can improve the construction performance, improve the rheology, lubricity and construction convenience of the material.

4. Surface activity
Because HPMC molecules contain hydroxypropyl and methoxy groups, they give it a certain surface activity, which can play the role of emulsification, dispersion and stabilization. Therefore, HPMC can be used in emulsion coatings, cosmetics and food industries to help evenly disperse incompatible substances.

5. Water retention
HPMC has excellent water retention properties and can effectively reduce water evaporation. In particular, adding HPMC to building materials (such as cement mortar and gypsum products) can prevent the mortar from cracking and reducing strength due to excessive water loss, and improve construction operability.

6. Film-forming property
HPMC can form flexible and transparent films, which is very important in the pharmaceutical (such as tablet coating), food (such as food coating) and coating industries. Its film-forming property makes it a good protective agent to improve the water resistance and mechanical strength of the material.

7. Chemical stability
HPMC has strong chemical stability, acid and alkali resistance, and is not easily affected by microorganisms. In the pH range of 3-11, its performance is relatively stable and not easy to degrade, so it can be used in a variety of environmental conditions.

8. Safety and biocompatibility
HPMC is non-toxic, non-irritating, and has good biocompatibility, so it is widely used in the food and pharmaceutical industries. In the pharmaceutical field, it can be used as a disintegrant, binder and sustained-release material for tablets, and is considered to be a safe pharmaceutical excipient. In the food industry, HPMC can also be used as a thickener and emulsifier stabilizer, such as ice cream, baked goods, etc.

9. Resistance to enzymolysis
HPMC exhibits good resistance to enzymolysis in certain environments and is not easily decomposed by enzymes. Therefore, it has advantages in some special application scenarios (such as pharmaceutical sustained-release systems).

10. Application fields
Due to its excellent physical and chemical properties, HPMC is widely used in many industries:
Construction industry: as a thickener and water-retaining agent for cement mortar to improve construction performance; in gypsum products, putty powder, and coatings, it plays a role in improving rheology and adhesion.
Pharmaceutical industry: used as pharmaceutical excipients, such as tablet coatings, sustained-release tablets, and the main ingredients of capsules.
Food industry: used as a thickener, emulsifier, stabilizer, and food coating material to improve the taste and stability of food.
Cosmetics industry: used in skin care products, shampoo, toothpaste and other products as a thickener, emulsifier and stabilizer.
Coatings and ink industry: enhance the film-forming property of coatings and improve rheology and adhesion.

11. Storage and Usage Precautions
HPMC is hygroscopic and should be stored in a cool, dry, ventilated place away from direct sunlight. When using, the appropriate model and viscosity should be selected according to different application requirements to achieve the best effect.

Hydroxypropyl methylcellulose (HPMC) is widely used in many industries due to its unique physical and chemical properties, such as water solubility, thickening, water retention, film-forming and chemical stability. Its non-toxic, harmless and good biocompatibility make it particularly important in the food and pharmaceutical fields. In the fields of construction, coatings, cosmetics, etc., HPMC, as a functional additive, not only improves product performance, but also optimizes processing and construction performance. Therefore, HPMC is an important polymer material with broad application prospects.