Preparation and Characterisation of Phase Change Material-Loaded Polyurea Microcapsules Several Hundred Micrometres in Diameter

In the present study, we attempted to prepare phase-change material (PCM)-loaded polyurea microcapsules several hundred micrometres in diameter via oil-in-water emulsion polymerisation. An oil phase with two types of isocyanate monomers (2,4-toluene diisocyanate (TDI) and phenyl isocyanate (PI)) and tetradecane as PCM was dispersed in an aqueous phase with hexamethylene diamine (HMD). The polyurea shell of microcapsules was formed by reaction of the isocyanate monomers with the amine groups derived from HMD and hydrolysed isocyanate monomers. A suitably adjusted agitation rate made it possible to prepare the required microcapsules. An increased molar ratio of TDI to PI in oil phase resulted in improvement of microcapsule morphology. Increased weight ratio of tetradecane to the two isocyanate monomers (TDI and PI) led to an increase in the PCM content in the microcapsules, which is preferable for practical applications. An examination using differential scanning calorimetry analyser demonstrated that the polyurea shell of the microcapsules scarcely influenced the thermal properties of encapsulated tetradecane.