Optimization of Oil-in-Water Emulsion Stability: Experimental Design, Multiple Light Scattering, and Acoustic Attenuation Spectroscopy

Abstract

To find an optimal formulation of oil-in-water (O/W) emulsions (φ_o = 0.05), the effect of emulsifier nature and concentration, agitation speed, emulsifying time, storage temperature and their mutual interactions on the properties and behavior of these dispersions is evaluated by means of an experimental design (Nemrodw software). Long-term emulsion stability is monitored by multiple light scattering (Turbiscan ags) and acoustic attenuation spectroscopy (Ultrasizer). After matching surfactant HLB and oil required HLB, a model giving the Sauter diameter as a function of emulsifier concentration, agitation speed and emulsification time is proposed. The highest stability of C₁₂E₄-stabilized O/W emulsions is observed with 1% emulsifier.

Keywords:

• Emulsification
• emulsion stability
• experimental design
• mechanical agitation
• nonionic surfactants
• rheology

The authors thank the Algerian Government (Ministry of Higher Education and Scientific Research) for a scholarship (M. B.) and a grant to the LGC. They acknowledge SEPPIC Co. for gifting the surfactant samples; H. Dihang and Y. Lefeuvre's assistance (Formulaction S.A.) with the stability study performed with the Turbiscan ags; and A. Jedidi and F. Théron for checking the conductivity measurements. Last, deep thanks are extended to S. Schetrite (LGC) for performing measurements and computing the model matrix of the emulsion (H₂O/T22/C₁₂E₄) with the Ultrasizer analyzer.

Notes

^a Hydrophile-lipophile balance.^[1,19]

^b In the formulas of the C_iE_jP_k type, i, j and k represent the average length of the carbon chain C (linear if no prefix, or deriving from Oxo alcohols), the number of moles of ethylene oxide, E, and propylene oxide, P, involved in the alkoxylation, respectively. These commercial surfactants still contain some unreacted alcohol.

^c C₁₈ = oleyl alcohol chain.