Protective colloidal effects of hydroxypropyl methyl cellulose on the stability of silicone oil emulsions

Oil in water emulsions were prepared by dispersion of silicone oil in aqueous solutions of hydroxypropyl methyl cellulose (HPMC) with various molecular weights. The resulting emulsions were characterized by a combination of size measurement and rheology techniques as a function of time elapsed after the preparation. The size and size distribution of the oil droplets showed little changes with the elapsed time, indicating the resulting emulsions are stable. The size of the oil droplet increased with the molecular weight of HPMC at a fixed concentration of HPMC, whereas it decreased with an increase in HPMC concentration at a constant molecular weight HPMC. All emulsions showed pseudoplastic flow and solidlike viscoelastic responses; their steady-state shear viscosity coefficients and dynamic moduli increased with an increase in the effective volume fraction of oil droplets in the emulsion.