Hydroxypropyl methylcellulose (HPMC) is a thickener, gelling agent and film former commonly used in the pharmaceutical, food, cosmetic and building materials industries. Its viscosity is one of the important parameters affecting its performance, which usually varies according to factors such as solution concentration, solvent type, temperature and molecular weight of HPMC.

The viscosity value of HPMC refers to the fluidity of its solution under certain conditions, usually expressed in mPa·s (millipascal seconds). In the viscosity standard of HPMC, the common concentration is 2% or 4% solution, and the measurement temperature is generally 20°C or 25°C. Depending on the brand and product, the viscosity of HPMC can range from a few hundred mPa·s to a few thousand mPa·s.

The following are the main factors affecting the viscosity of HPMC solution:

Molecular weight: The larger the molecular weight of HPMC, the higher its viscosity. HPMC with a high molecular weight can form more intermolecular interactions in the solution, so it exhibits a higher viscosity.

Hydroxypropyl and methyl substitution: The higher the degree of hydroxypropyl (-OH) and methyl (-CH?) substitution, the higher the water solubility and viscosity of HPMC. The increase in hydroxypropyl substitution can effectively improve the solubility of HPMC, while methylation enhances its viscosity.

Solution concentration: The concentration of HPMC solution directly affects its viscosity. The higher the concentration, the greater the viscosity. Generally speaking, solutions with a concentration between 2% and 5% are more common, and the viscosity of high-concentration solutions will be higher.

Solvent: HPMC dissolves well in water, so its viscosity is usually evaluated based on aqueous solutions. However, different types of solvents can also affect solubility and viscosity.

Temperature: Temperature has a significant effect on the viscosity of HPMC solution. Generally speaking, an increase in temperature will lead to a decrease in solution viscosity because high temperatures will accelerate molecular motion and increase the fluidity of the solution.

HPMC viscosity is often used in the following fields:

Pharmaceutical field: It is used as a sustained-release agent for drugs, a tablet binder, and a component of capsule shells. It can ensure the stable release of drugs in the body by controlling viscosity.

Food industry: Used as a thickener and gelling agent, it can effectively improve the taste and texture of food, such as ice cream, jelly, candy, etc.

Construction industry: Used as a thickener and water retaining agent in building materials such as cement and mortar to improve the fluidity and construction performance of the material.

Cosmetic industry: Used in products such as creams, facial cleansers, eye shadows, etc. to provide good viscosity and stability.

When choosing a suitable HPMC product, it is crucial to understand its specific viscosity characteristics, especially the requirements for fluidity and stability in different applications. If there is a requirement for the specific viscosity value of a certain HPMC, you can refer to the relevant information in the product specification or test it with a viscosity measuring instrument.