Rheological characteristics of petroleum jelly formulations containing organically modified layered double hydroxides

Abstract

The effectiveness of stearic acid modified layered double hydroxides (OLDH) as viscosity modifier and stabilizer in petroleum jelly (PJ) formulations has been studied and its rheological properties evaluated. Mg-Al-LDH was organically modified using stearic acid which is anionic surfactant widely used in topical formulations. Successful incorporation of stearate anion into LDH interlayers was confirmed by XRD, FTIR, SEM, and TGA results. PJ formulations were prepared using different OLDH contents (0.5, 1, 1.5 and 2 wt. %) using a high shear mixer. The incorporation of OLDH significantly increased the viscosity of the PJ formulations which is explained by strong interaction between OLDH particles and hydrocarbon chains of PJ. The percolation threshold was observed to be at 1.5 wt.% of OLDH loading suggesting the presence of a well-developed interface between the filler and the polymer matrix. The non-Newtonian shear thinning indicated the formation of gel-like structure. Dynamic state rheological data of PJ formulations showed a dominance of elastic property imparted by solid phase in OLDH based system. OLDH, therefore, showed great promise as an efficient structural ingredient in cosmetic formulations offering viscosity enhancement as well as shear thinning behaviour which could result in formulation stability, better skin feel and spreadability.