title: Rheological evaluation of petroleum jelly as a base material in ointment and cream formulations: steady shear flow behavior.
abstract: 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 degrees 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 quantitatively 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.
authors.affiliation: Department of Organic Material Science and Engineering, School of Chemical Engineering, Pusan National University, Pusan 609-735, Korea.
authors.forename: Eun-Kyoung
authors.initials: EK
authors.lastname: Park
authors.forename: Ki-Won
authors.initials: KW
authors.lastname: Song
mesh_terms: D000465:Algorithms; D002626:Chemistry, Pharmaceutical; D003358:Cosmetics / Q000737:chemistry; D003460:Crystallization; D004548:Elasticity; D008854:Microscopy, Electron; D008956:Models, Chemical; D009823:Ointment Bases / Q000737:chemistry*; D010232:Paraffin / Q000737:chemistry; D010577:Petrolatum / Q000737:chemistry*; D012212:Rheology; D014783:Viscosity
chemical_list: D003358:Cosmetics; D009823:Ointment Bases; D010232:Paraffin; D010577:Petrolatum