Microencapsulation of low melting phase change materials for cold storage applications

Microencapsulation is a proven viable method for the containment and retention of phase change material (PCM) in tiny shells. However, it must be well encapsulated to be effective. This work employed a photo-induced suspension polymerisation technique to encapsulate low melting PCM using an ultraviolet perfluoroalkoxy (UV PFA) coiled tube reactor. Commercially available Pure Temp (PT) 6 (Tpeak melting = 6.2 °C and ΔH = 150.1 kJ/kg) and cross-linked polymethyl methacrylate were used as PCM and shell material, respectively. The effect of different synthesis parameters such as polymerisation time and optimum core-shell mass ratio were thoroughly investigated. The morphology, chemical stability, thermal properties, and microcapsules produced at the optimal yield were examined and surface morphology analysis showed the absence of distortions and complete PCM core entrapment. The developed microencapsulated PCM (m-PCM) had a peak melting temperature of 8.2 °C and an average latent heat of 131.1 kJ/kg, representing 87.4% PCM content. Thermogravimetric analysis showed that the microcapsules degraded above 440 °C, whereas PT6 completely evaporated at 240 °C. The mass loss of the synthesised m-PCMs stabilised after 8 days of heating at 40 °C with only 0.6 % mass loss after 30 days. By contrast, the pure PCM lost about 6.6% within the same period under similar test conditions. The m-PCM showed good thermal reliability after multiple heating/cooling cycles, indicating of a well-contained PCM. The successful synthesis of low-temperature PCM microcapsules in a low-intensity UV PFA coiled tube reactor is an important energy and time-saving approach for producing microcapsules of high thermal properties, making them suitable for cold storage application and holds the potential for their production on a large scale.