Influence of Chemical Structures of Emulsifiers on Feasibility of Isopropyl Palmitate Lotion Formation

INTRODUCTION Emulsion formulations are one of hard tasks since there are a lot of emulsifiers which can be selected. To save time in emulsifier selection, the hydrophile-lipohile balance (HLB) system has been used for choosing proper emulsifiers. Lipophilic compounds (oils, fats, and waxes) have an individual value called “required HLB”. An emulsifier or blend of emulsifiers, having an HLB equal to the required HLB of the lipophilic phase will make a more stable emulsion than emulsifiers of any other HLB values. Generally, blends of emulsifiers can provide much higher effective as emulsifiers than any single chemical composition would be because their resulted complex interfacial films can protect the internal droplets from coalescence, leading to more stability. Nevertheless, "right chemical type" is also as important as "right HLB". It was reported that the properties of emulsifier mixtures, i.e. HLB and carbon number of alkyl chain length, affected the stability of asphalt emulsions. Moreover, only total HLB of an emulsifier pair was found to be not enough to formulate a physically stable coconut oil emulsions. Besides normal emulsions, the stability of multiple emulsions was also depended on emulsifier chemistry. Therefore, it is interesting to investigate the influence of few differences in HLB values but large differences in chemical structures of an emulsifier in the emulsifier blends on feasibility of emulsion formation. In this study, isopropyl palmitate (IPP) was formulated in form of lotion using four pairs of different blends of nonionic emulsifiers and evaluate for feasibility of emulsion formation. The required HLB for IPP is 11.5. Four pairs of emulsifier blends with the identical total HLB of 11.5 prepared from different components were investigated.