Phase change microcapsules with high encapsulation efficiency using Janus silica particles as stabilizers and their application in cement

Abstract

This study reports the preparation of phase change microcapsules (PCMs) which possess high encapsulation efficiency, this is achieved by using Janus silica particles (JSPs) as stabilizers in combination with Pickering emulsion and suspension polymerization methods. The inner shell and outer shell of the PCMs are polyacrylate and JSPs respectively. The morphologies and particle sizes of the PCMs can be controlled well, as evidenced by SEM and optical microscopy characterization. The amount of JSPs and functional monomer methacrylic acid play key roles in controlling the morphologies of the PCMs. The encapsulation ratio of PCMs can be adjusted with the encapsulation efficiency reaching as high as 99.6%. The phase change enthalpy of the PCMs is 175.1 J/g when the core/inner shell/outer shell weight ratio of n-octadecane/polyacrylate/silica microcapsules is 70:21:1. The TGA result indicates that the PCM is stable up to 150 °C. The enthalpy of PCM remains almost unchanged after 7560 phase change cycles, illustrating the PCM exhibits excellent thermal reliability and durability. The PCM-modified cement plate shows a remarkable cooling effect, which means that this type of PCM has promising applications in the construction field.