Emulsion polymerization of styrene with sodium hexadecyl sulphate/hexadecanol mixtures as emulsifiers. Initiation in monomer droplets

Abstract

Abstract Part 1 describes the emulsification of styrene with mixtures of sodium hexadecyl sulphate (SHS), and hexadecanol (HD). Addition of HD led to a much better emulsification than with the anionic emulsifier alone. The effect of the fatty alcohol depended strongly upon the method of preparation of the emulsion. To obtain a fine dispersion of styrene it was necessary to treat the anionic emulsifier and the fatty alcohol with water at an elevated temperature prior to the addition of styrene. In this way emulsions with droplet sizes in the range of 0,5–1 μm could be prepared with relatively small amounts of fatty alcohol and with moderate stirring. The finely dispersed monomer emulsions produced by this method were capable of adsorbing the major part of the anionic emulsifier. Part 2 describes emulsion polymerization experiments with mixtures of SHS and HD. With emulsifier systems providing the most effective emulsification, the monomer droplets became the main loci for particle initiation and polymerization. Evidence for this hypothesis was provided by the bimodal dispersion of the latex particles, the major part being particles with a size distribution similar to that of the monomer droplet emulsion. The results of the kinetic investigations provided additional arguments for a mechanism involving initiation and polymerization in monomer droplets.