Interactions Among Temperature, pH, and Agitation May Cause Instability in an Oil-in-water Emulsion

Abstract

Two key features of an emulsion, stability and viscosity, are not only considered dependent on ingredient quantities but also delicately affected by emulsification conditions, such as pH, temperature, and mixing conditions. In the laboratory, we formulated an O/W emulsion made up of 41% water, 9.8% silicon (polydimethylsiloxane), 22.1% liquid sucrose (700 mg/ml), 22.1% light liquid paraffin, and 1.5 to 5% paraffin emulsifier by volume % purposed for large-scale production as a rubber coating for decorative purposes. This emulsion became faulty after large-scale production, while it was fine on the laboratory scale. This study investigated the probability of a complicated interaction among pH, temperature, solutes, and agitation intensity on the stability and viscosity of our emulsion by focusing on sugar degradation effects on these parameters. This emulsion was made in two different temperatures and agitation rates, and the emulsification time was 20 minutes for all samples. The critical roles of appropriate pH regulators or buffers in the stability were also investigated. It was found that applying intense agitations at 1500 rpm during emulsifications in high temperatures may lead to absurdly high emulsion viscosity, accompanied by a sharp pH fall.