Phase Change Microcapsules with a Polystyrene/Boron Nitride Nanosheet Hybrid Shell for Enhanced Thermal Management of Electronics.

Organic shell material and phase change material (PCM) have low thermal conductivity, which reduces the heat absorption and release rate of microencapsulated phase change materials (MEPCMs). Boron nitride nanosheets (BNNSs) with high thermal conductivity can not only stabilize the oil phase as the Pickering emulsifier but also improve the thermal conductivity of MEPCMs as one of the shell components, thus facilitating the heat conduction in the microcapsule system. Herein, MEPCM with paraffin wax (PW) as the core material and polystyrene (PS) modified by BNNSs as the shell material (PW@PS/BNNS MEPCMs) are synthesized via Pickering emulsion polymerization. The structure of PW@PS/BNNS MEPCMs can be regulated by tuning the PW and BNNS contents, to achieve high latent heat and thermal conductivity. In comparison to pure PW, the thermal conductivity of MEPCMs-5 wt % BNNSs increases by 63.76% at 25 °C. The PW@PS/BNNS powder possesses a latent heat capacity of 166.3 J/g, corresponding to a high encapsulation ratio of 80.77%. These properties endow the prepared MEPCMs with excellent thermal regulation properties. We also propose the formation mechanism of PW@PS/BNNS MEPCMs via Pickering emulsion polymerization for the first time, which will guide the MEPCM fabrication toward a reliable direction.