Correlation of Viscoelastic Functions for Pharmaceutical Semisolids: Comparison of Creep and Oscillatory Tests for Oil-in-Water Creams Stabilized by Mixed Emulsifiers

摘要: Liquid paraffin-in-water emulsions stabilized by mixed emulsifiers of a surfactant (cetrimide or cetomacrogol) and long-chain alcohol were used as model systems to represent pharmaceutical semisolids. They examined in their linear viscoelastic regions using creep oscillatory (Weissenberg rheogoniometer) techniques. Storage loss compliances (J′ J″) over the frequency range 2.5 × 10− 8 1.5 1 Hz. calculated from data numerical formulas. The transformed derive other functions, storage moduli (G′ G″), viscosities (η′ η″), tangent (tan a) at same frequencies. agreement between functions those obtained directly measurements frequencies ranging 7.91 4 was generally good. Discrepancies extremities this result practical difficulties involved when are made very short times (representing high frequencies) evaporation water parallel plates rheogoniometer during low dynamic experiments. Neither small strain technique alone covered entire time necessary for an exhaustive study Creep unavoidably inaccurate frequencies, limitations gear box prevented being extremely unification so provide description extended (10− 8–25 Hz.) is discussed. variations each function with considered reference theory; limiting values shapes plots agreed well theoretical liquids. It concluded that such interconversion techniques applicable valuable interpreting rheological behavior system.