Mittuniversitetet

Expancel microspheres are produced by suspension polymerization of silica-stabilizedemulsions, and poor stabilization causes instabilities in the production. The purpose of this study was to investigate how emulsion stability is affected by, e.g., pH, shear force, flocculating agents, salt, and monomer droplet size. With the aim to improve the stability of these silica-stabilized monomer emulsions.

The study consisted of literature studies, emulsion studies, polymerization, and characterization. Analytical methods used were e.g. microscopy for droplet size assessment, thermomechanical analysis, and gas chromatography to evaluate expansion properties. Emulsions were based on a recipe, of an existing grade of Expancel, modified to suit the method for emulsion studies.

The study showed there are many ways of affecting the stability of silica-stabilizedemulsions. Shear forces decrease the stability significantly, and emulsion stability isgreatly affected by pH. For the type of emulsions used in this study, pH at 2.0 and 4.5-4.6were the most optimal for improved stability.

The study contributes to more knowledge of improving silica stabilized Pickering emulsions, under certain conditions, with the hope of improving the product quality of expandable microspheres.