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KMID : 0043320100330010141
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Archives of Pharmacal Research
2010 Volume.33 No. 1 p.141 ~ p.150
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Rheological Evaluation of Petroleum Jelly as a Base Material in Ointment and Cream Formulations: Steady Shear Flow Behavior
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Song Ki-Won
Park Eun-Kyoung
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Abstract
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The objective of the present study is to systematically characterize a nonlinear rheological behavior of petroleum jelly (petrolatum) in steady shear flow fields correspondent to the spreading condition onto the human body. With this aim, using a strain-controlled rheometer, the steady shear flow properties of commercially available petroleum jelly have been measured at 37°C (body temperature) over a wide range of shear rates. In this article, the shear rate dependence of steady shear flow behavior was reported from the experimentally obtained data. In particular, the existence of a yield stress and a non-Newtonian flow behavior were discussed in depth with a special emphasis on their importance in actual application onto the human body. In addition, several inelastic-viscoplastic flow models including a yield stress parameter were employed to make a quantitative description of the steady shear flow behavior, and then the applicability of these models was examined in detail. Main findings obtained from this study can be summarized as follows : (1) Petroleum jelly exhibits a finite magnitude of yield stress. The appearance of a yield stress is attributed to its three-dimensional network structure that can show a resistance to flow and plays an important role in determining a storage stability and sensory feature of the product. (2) Petroleum jelly demonstrates a pronounced non-Newtonian shear-thinning flow behavior which is well described by a power-law equation and may be interpreted by the disruption of a crystalline network under the influence of mechanical shear deformation. This rheological feature enhances sensory qualities of pharmaceutical and cosmetic products in which petroleum jelly is used as a base material during their actual usage. (3) The Casson, Mizrahi-Berk, Heinz-Casson and Herschel-Bulkley models are all applicable and have almost an equivalent ability to quatitatively describe the steady shear flow behavior of petroleum jelly whereas the Bingham model does not give a good validity. Among these flow models, the Herschel-Bulkley model provides the best applicability.
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KEYWORD
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Petroleum jelly (petrolatum), Rheology, Steady shear flow behavior, Yield stress, Non-Newtonian shear-thinning viscosity, Viscoplastic flow models
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