The finished product of hydroxypropyl methylcellulose is in the form of white powder or white loose fibrous solid, and the particle size passes through an 80-mesh sieve. The finished product has different ratios of methoxy content and hydroxypropyl content and different viscosities, which result in different varieties with different performances. It has the characteristics of being soluble in cold water and insoluble in hot water, similar to methylcellulose, and its solubility in organic solvents exceeds its solubility in water. It can be dissolved in anhydrous methanol and ethanol, and can also be dissolved in chlorinated hydrocarbons such as dichloromethane, trichloroethane, and organic solvents such as acetone, isopropanol and diacetone alcohol. When dissolved in water, it will combine with water molecules to form a colloid. It is stable to acids and alkalis and is not affected in the range of pH = 2 to 12. Although hydroxypropyl methylcellulose is non-toxic, it is flammable and will produce violent chemical reactions with oxidants.
The viscosity of HPMC products increases with increasing concentration and molecular weight, and when the temperature rises, its viscosity begins to decrease. When it reaches a certain temperature, the viscosity suddenly rises and gelation occurs. The gelation temperature of low-viscosity products is higher than that of high-viscosity products. Its aqueous solution is stable at room temperature, and except for being degraded by enzymes, there is no general viscosity degradation phenomenon. It has special thermal gelation properties, good film-forming properties and surface activity.
