2026-02-09- readingsHydroxypropyl methylcellulose (HPMC) is a nonionic cellulose mixed ether. Due to variations in the substitution ratio of methoxy and hydroxypropyl groups and the total degree of substitution in its molecular chain, a series of varieties with different properties can be formed. Compared to ionic cellulose ethers, HPMC exhibits good chemical inertness and does not react with heavy metal ions.
Main Performance Overview
1. Solubility Characteristics
HPMC has good solubility in cold water, but gels in hot water. Due to the introduction of hydroxypropyl groups into its molecule, its gelation temperature is typically significantly higher than that of methylcellulose; some highly substituted products can have gel points approaching 100℃, broadening its application window in high-temperature environments. In organic solvents, HPMC with a specific degree of substitution is soluble in methanol, ethanol, acetone, and some chlorinated hydrocarbons, exhibiting better organic solvent compatibility than conventional water-soluble cellulose ethers.
2. Viscosity Characteristics
The viscosity of HPMC solutions mainly depends on its molecular weight, solution concentration, and temperature. Viscosity increases with increasing concentration and molecular weight. Increasing temperature leads to a decrease in viscosity, but a sharp increase occurs at a specific gelation temperature. Its solutions exhibit pseudoplastic fluid behavior, demonstrating excellent storage stability at room temperature and resistance to chemical degradation.
3. Chemical Stability
HPMC remains stable over a wide pH range (typically 2-12) and is resistant to common weak acids and alkalis. Strong acids may cause a decrease in viscosity, while strong alkalis may cause a short-term increase followed by a slow decrease in viscosity. This characteristic makes it suitable for formulation systems in various acidic and alkaline environments.
4. Compatibility
HPMC is well-compatible with many water-soluble polymers (such as polyvinyl alcohol, other cellulose ethers, and natural colloids), forming homogeneous and transparent mixed solutions. It can also be used in combination with plasticizers such as polyols (such as glycerol and sorbitol) to improve its film-forming flexibility.
5. Resistance to Enzymatic Hydrolysis
Due to the uniform coverage of substituents on the cellulose backbone, HPMC exhibits excellent resistance to enzymatic hydrolysis. Its solutions are not easily degraded by microorganisms, allowing for long-term storage in many aqueous systems without the addition of preservatives, thus enhancing product safety and environmental friendliness.
6. Film-forming Properties
HPMC forms transparent, tough films with good moisture resistance and thermal stability. By adding appropriate plasticizers, the film's flexibility, tensile strength, and hygroscopicity can be further adjusted to meet the needs of different coating and encapsulation processes.
7. Crosslinking Modification
HPMC can undergo controlled crosslinking with aldehydes (such as glyoxal) under acidic conditions, transforming it into a water-insoluble form. This property can be used to prepare water-resistant coatings or special separation membranes, and its solubility can be restored under alkaline conditions.
In summary, HPMC, with its tunable solubility, stable viscosity, wide pH adaptability, good compatibility, and excellent film-forming and anti-enzymatic properties, has become a multifunctional and reliable polymer material, playing a crucial role in numerous industrial fields.
