12 - 14 October, Lyon, France
Rapid emulsifier selection and evaluation of emulsion stability for reformulation
T. Sobisch, D. Lerche, LUM
Rudower Chaussee 29 (OWZ) 12489
info@lum-gmbh.de, www.lum-gmbh.com
Abstract
Selection of emulsifiers and evaluation of emulsion stability is a frequent task. This relates to practical issues like formulation of emulsions, optimization of preparation conditions, quality control, shelf life estimation and breaking of emulsions. Due to European legislation (REACH) many companies are facing the problem to replace proven components in their formulations (low volume speciality compounds or problematic chemicals). This also applies to emulsifiers and emulsion based products.
A multisample technique based on analytical centrifugation is presented which allows for an accelerated study of creaming, sedimentation and of separation of oil and water phases. Not only information on the extent of phase separation is provided but also the kinetics are measured directly in-situ.
The method was applied to check for alternatives to nonyl phenol based surfactants as emulsifiers for silicone oil emulsions. Different commercial products were evaluated. It proved to be a very efficient screening method, which can be also applied in every day formulation work.
Due to the multisample approach one centrifugal run with 12 different samples was sufficient to identify more environmentally benign emulsifiers with identical or better performance. In a second run the efficiency of emulsifier combinations was tested. The primary destabilization mechanism for all emulsions was creaming, however, most emulsions showed phase inversion when a critical phase ratio was reached inside the cream layer. By increasing the polarity of the alternative emulsifiers the risk of phase inversion could be rigorously reduced.
Keywords: reformulation, REACH, emulsifier selection, silicon oil-in-water emulsions, creaming kinetics, analytical centrifugation
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