Continuous shear, viscoelastic and spreading properties of a new topical vehicle, FAPG base

Abstract

Abstract The rheology of a new topical vehicle FAPG base was investigated over the temperature ranges of 25–37°. Continuous shear rheograms obtained with a Ferranti-Shirley cone and plate viscometer were hysteresis loops with spur points; loop areas, yield values and apparent viscosities decreased with increase in temperature and an activation energy for viscous flow of 10.4 kcal mol−1 (43.5 kJ mol−1) was derived. In creep (concentric cylinder geometry) the base was viscoelastic with a low limit of linearity with respect to strain. Creep compliance curves showed an initial elastic response, a region of retarded elasticity and a viscous region; compliances increased and viscosities decreased with temperature rise. Patient acceptance of skin spreadability of the base was assessed using a master curve concept; the spreading properties were close to the preferred values for maximum patient acceptance. It is concluded that FAPG base deserves further study as a vehicle for dermatological use.