Rheological Properties of Highly Dense Dispersions of Poly (oxyethylene) hydrogenated Castor Oil Determined by Oscillation Rheometry

The rheological behaviour of poly (oxyethylene) (10) hydrogenated castor oil dispersions was investigated by oscillation rheometry at 25°C as a function of dispersion concentration and frequency. HCO-10 dispersions were characterized in terms of viscoelastic parameters such as complex viscosity (η*), storage modulus (G') and loss modulus (G″). Based on the results, the following conclusions were drawn.The complex viscosity of HCO-10 dispersions is maximum around 70 wt%. Below this value, storage modulus is greater than that of loss modulus having a gel-like character. Above 70 wt%, loss modulus is greater than that of storage modulus, indicating possibly a liquid-like character.In addition, the viscoelastic parameters were compared with the results of aN' and S33 by ESR spin labelling, T1 relaxation time by NMR and long spacing by small angle X-ray diffraction. It became clear that immobilization of free water in the bilayer of HCO-10 vesicles is indispensable to the gel-formation of HCO-10 dispersions.