Fatima Rasool, Haris Rizwan and Haji Muhammad Shoaib Khan
Punjab University College of Pharmacy, University of the Punjab Lahore, Pakistan
The field of emulsion rheology is developing rapidly due to investigations involving mono-dispersed emulsions having narrow droplet size distributions. Most of the cosmetics and pharmaceuticals are associated with complex flow of materials such as selection of ingredients, formulation preparation, packaging and shelf storage. The object of the study was to evaluate the rheological studies of four different creams available in market. Two brands of cold and two of vanishing creams were selected. The rheological parameters of these creams were tested by storing them at different accelerated temperatures i.e. 4C, 25°C, 40°C, 40°C & 75% RH. The readings were taken after a period of 15 days for the period of 135 days. A computerized cone plate Rheometer was used in this study. The temperature of rheometer was maintained at 25°C. These results indicated that creams behaved as a non-Newtonian fluid (Pseudo plastic fluid) at all temperatures. Creams showed a decline in viscosity with the increase in temperature. A stress strain relationship was also established for these creams and it was also demonstrated that conditions of high temperature and moisture affect the flow properties which in turn affect the desired properties of such creams. It is concluded that there is marked dependence of rheology on the storage conditions like temperature and humidity. Statistical analysis demonstrated a significant difference in the flow behavior of creams with respect to variation in temperature.
Keywords: Rheology, Viscosity, Non-Newtonian fluid, Creams.