Hydroxypropylmethylcellulose (HPMC) is a popular polymer used in industries such as pharmaceuticals, construction, food and personal care. It is a modified form of cellulose obtained by reacting methylcellulose with propylene oxide. HPMC is a white or off-white, odorless, tasteless powder, easily soluble in water, ethanol and other organic solvents. This paper discusses the main technical indicators of HPMC.
viscosity
Viscosity is the most important technical index of HPMC, which determines its flow behavior and application in various industries. HPMC has a high viscosity, which means it has a thick, honey-like texture. The viscosity of HPMC can be adjusted by changing the degree of substitution of hydroxyl groups. The higher the degree of substitution, the higher the viscosity.
Degree of substitution
The degree of substitution (DS) is another important technical indicator of HPMC, which refers to the number of hydroxyl groups replaced by hydroxypropyl groups and methyl groups. The DS of HPMC typically ranges from 0.1 to 1.7, with higher DS indicating greater modification. The DS of HPMC affects its solubility, viscosity and gel properties.
molecular weight
The molecular weight of HPMC is also an important technical index that affects its physical and chemical properties such as solubility, viscosity, and gelation. HPMC typically has a molecular weight of 10,000 to 1,000,000 Daltons, with higher molecular weights indicating longer polymer chains. The molecular weight of HPMC affects its thickening efficiency, film forming ability and water holding capacity.
PH value
The pH value of HPMC is an important technical index affecting its solubility and viscosity. HPMC is soluble in acidic and alkaline solutions, but its viscosity is higher under acidic conditions. The pH of HPMC can be adjusted by adding acid or base. HPMC typically has a pH between 4 and 9.
moisture content
The moisture content of HPMC is an important technical index that affects its storage stability and processing performance. HPMC is hygroscopic, which means it absorbs moisture from the air. The moisture content of HPMC should be kept below 7% to ensure its stability and quality. High moisture content can lead to polymer caking, clumping and degradation.
Ash content
The ash content of HPMC is an important technical index affecting its purity and quality. Ash refers to the inorganic residue left after HPMC is burned. The ash content of HPMC should be less than 7% to ensure its purity and quality. A high ash content may indicate the presence of impurities or contamination in the polymer.
Gelation temperature
The gel temperature of HPMC is an important technical index that affects its gel performance. HPMC can gel under certain temperature and concentration conditions. The gelation temperature of HPMC can be adjusted by changing the degree of substitution and molecular weight. The gelling temperature of HPMC is typically 50 to 90°C.
in conclusion
Hydroxypropylmethylcellulose (HPMC) is a multifunctional polymer with a wide range of specifications. The main technical indicators of HPMC include viscosity, degree of substitution, molecular weight, pH value, moisture content, ash content, gelation temperature, etc. These technical indicators affect the physical and chemical properties of HPMC and determine its performance in various industries. By knowing these specifications, we can choose the right type of HPMC for our specific application and ensure its quality and stability.