Improvement in Microencapsulation process of Phase Change Materials with Nano-Silicon Dioxide Hydrosol as Emulsifier

Microencapsulated phase change materials (MEPCMs) have the potential to be used for energy storage applications in buildings due to their relatively high latent heat capacities. However, good quality MEPCMs could be affected by the type of emulsifier used in their fabrication. For instance, commonly used organic emulsifiers such as styrene-maleic anhydride copolymer (SMA), Triton X-100 and Brij-30 have limited enhancement effect on the thermal and structural integrity of MEPCMs. Some past investigations have however suggested that nano-colloidal materials could be ideal candidates as emulsifiers since they are capable of enhancing the thermophysical properties and core material content of MEPCMs and also considered to be less toxic than organic emulsifiers. To this end, a nano-colloidal material (nano-silicon dioxide hydrosol) was selected and evaluated in an encapsulation process involving n-octadecane as the core phase change material, melamine as shell monomers, citric acid and ammonium chloride as pH controllers. The analysis of the results showed a significant improvement in the thermal stability temperature of the developed MEPCM sample by approximately 78°C in comparison with samples fabricated with SMA. The maximum core material content achieved with the nano-SiO2 was also 83% as against 59% for the sample fabricated with SMA. There was however a reduction of about 17% in the energy storage capacity and a slight reduction of 0.57°C in its melting temperature as compared with the pure n-octadecane. The nucleating agent also did affect the morphology, particle size distribution and the content of the base materials. Further enhancement studies are therefore being encouraged.