Hydroxy propyl methyl cellulose

About Hydroxy propyl methyl cellulose

Hydroxy propyl methyl cellulose
CAS number [9004-65-3]
 
Hypromellose (INN), short for hydroxypropyl methylcellulose (HPMC), is a semisynthetic, inert, viscoelastic polymer used as an ophthalmic lubricant, as well as an excipient and controlled-delivery component in oral medicaments, found in a variety of commercial products.
 
As a food additive, hypromellose is an emulsifier, thickening and suspending agent, and an alternative to animal gelatin. Its Codex Alimentarius code (E number) is E464.
Hypromellose is a solid, and is a slightly off-white to beige powder in appearance and may be formed into granules. The compound forms colloids when dissolved in water. Although non-toxic, it is combustible and can react vigorously with oxidising agents.
 
Hypromellose in an aqueous solution, unlike methylcellulose, it does not exhibit thermal gelation property. That is, when the solution heats up to a critical temperature, the solution congeals into a non-flowable but semi-flexible mass. Typically, this critical (congealing) temperature is inversely related to both the solution concentration of HPMC and the concentration of the methoxy group within the HPMC molecule (which in turn depends on both the degree of substitution of the methoxy group and the molar substitution. That is, the higher is the concentration of the methoxy group, the lower is the critical temperature. The inflexibility/viscosity of the resulting mass, however, is directly related to the concentration of the methoxy group (the higher is the concentration, the more viscous or less flexible is the resulting mass).