Rheological estimation of the spreading characteristics of pharmaceutical semisolids

A Ferranti-Shirley cone and plate viscometer was utilized to characterize the spreading properties of white petrolatum U.S.P., white ointment U.S.P., and anhydrous lanolin U.S.P. Data were obtained for structural breakdown during repetitive cycling and for structural breakdown at constant shear. The problem of slippage at the revolving cone/sample interface is discussed. An attempt is made to relate rheological differences and molecular structure.