In situ encapsulation of tetradecane droplets in oil-in-water emulsions using amino resins

Microcapsules of tetradecane enclosed by a polymeric wall of amino resin were synthesized by the in situ polymerization using melamine-formaldehyde pre-condensates. It was found that resin concentrations of 60240 g L-1 for a phase volume fraction of 0.14 and 0.29 and concentrations of 50-240 g L-1 for a phase volume fraction of 0.43 lead to stable microcapsules. Furthermore, the dependence of the shell thickness from the resin concentration for a phase volume fraction of 0.29 was investigated whereas the shell thickness was calculated from the density and the mean diameter of the capsules. It was found that below a concentration of 100 g L-1 the density and thus the shell thickness increases linear with the resin concentration whereas at higher concentrations it almost remains constant and only the amount of the resin precipitated in solution increases. Additionally, it was shown that the mean droplet size (which is almost equal to the capsule size) in dependence of the stirring speed can be derived from the theory of droplet disruption. Thereby the coherence beginning with the stirring speed and the mean diameter to the total surface and the shell thickness is described.