Influence of operation conditions on the microencapsulation of PCMs by means of suspension-like polymerization

Microcapsules containing PRS(R) paraffin wax (core) and a polystyrene shell were prepared by suspension-like polymerization. The influence of reaction temperature, stirring rate, and mass ratio of paraffin wax to styrene on the properties of phase change materials microcapsules was studied. The reaction temperature had not a significant effect on the size of the microcapsules but an increase of molecular weight and a narrow molecular weight distribution of polystyrene shell were observed when reaction temperature was increased. An exponential relationship between the stirring rate and the mean particle diameter in number has been found. It was observed that paraffin is difficultly encapsulated when the paraffin/polymer mass ratio was higher than 2.00, as a consequence of a shortage of polymer that could not completely cover the amount of paraffin added. However, when a large proportion of monomer was employed, the polymer tended to polymerize inside the droplets during the microencapsulation process forming complex inner structures. The microcapsules obtained have an interesting energy storage capacity of 153.5 J/g that makes them suitable for different applications.