[The rheology properties of common hydrophilic gel excipients]

To investigate theological properties of common hydrophilic gel excipients such as Carbopol based on viscosity, the viscosity was determined by rotation method and falling-ball method. Linear regression was made between ln(eta) and concentration, the slope of which was used to explore the relation between viscosity and concentration of different excipients. The viscosity flow active energy (E(eta)) was calculated according to Arrhenius equation and was used to investigate the relation between viscosity and temperature of different excipients. The results showed that viscosities measured by two methods were consistent. Concentration of guargum (GG) and hydroxypropylmethyl cellulose (HPMC) solution had a great influence on the viscosity, k > 5; while concentration of polyvinylpyrrolidone-K30 (PVP-K30) and polyethylene glycol 6000 (PEG6000) exerted a less effect on viscosity, k < 0.2; viscosity flow active energy of different excipients were close, which ranged from 30 to 40 kJ x mol(-1). Therefore, theological properties study could provide the basis for application of excipients and establish a foundation for the research of relation between excipients structure, property and function.