A Rapid Method for Low Temperature Microencapsulation of Phase Change Materials (PCMs) Using a Coiled Tube Ultraviolet Reactor

Abstract

Microencapsulation of phase change materials (PCMs) remain a suitable option within building materials, as they contribute to the thermal mass and provide an energy buffer, an added benefit. This paper presents a novel method for the rapid fabrication of microencapsulated phase change materials (PCMs) at ambient conditions in a perfluoroalkoxy (PFA) coiled tube ultraviolet (UV) reactor. The objective of this study was to optimize key parameters such as the product yield and quality of the as-prepared microcapsules. Rubitherm® RT-21™ PCM was microencapsulated within shells of poly-methyl-methacrylate (PMMA) through a suspension emulsion polymerization approach, where the crosslinking of polymers was driven by UV radiations with an appropriate photoinitiator. The characteristics of the resulting PCM microcapsules were found to be affected by the volumetric flow rate of the emulsion inside the coiled tube reactor. Higher volumetric flow rates led to higher PCM contents and higher microencapsulation efficiency, resulting in an average particle size of 6.5 µm. Furthermore, the effect of curing time on the PCM microcapsule properties was investigated. The optimum encapsulation yield, conversion, efficiency and PCM content were observed after 10 min of polymerization time. The thermal analysis indicated that the developed process had an efficiency of 85.8%, and the capsules were characterized with excellent thermal properties. Compared to the conventional thermal microencapsulation processes, the use of a coiled tube UV reactor with an appropriate photoinitiator enables the encapsulation of heat-sensitive PCMs at ambient conditions, and reduces the microencapsulation time dramatically. As a result, this novel microencapsulation approach can lead to a wider scope of PCM encapsulation and enable rapid, continuous and potentially large-scale industrial production of PCM microcapsules with low energy consumption.

Combined “Renewable Energy–Thermal Energy Storage (RE–TES)” Systems: A Review

“…There is a body of research that has focused extensively on PCMs preparations and potential applications [125,127,128,[131][132][133][134][135]. Moreover, an innovative solution was developed by Yan Cao et al to address leakage and high flammability in PCMs through the creation of a series of leakage-proof phase change composites (PCCs) with excellent solar thermal conversion capabilities and superior flame retardancy.…”

One-Step Bulk-Suspension Polymerization of Polyethylene Glycol-Based Copolymer Microspheres for Phase Change Textiles

“…It could be seen that the decomposition of SMA-g-PEG started at 340.2 °C and reached the highest weight loss rate at 402.2 °C. In Figure 6a, the 3.7% thermal weight loss before 200 °C was mainly due to thermal decomposition of PVA on the surface of the copolymer, which was not completely washed off [33], and 5.3% thermal weight loss in a range of 200-320 °C was mainly due to the thermal decomposition of the anhydride group (in SMA) to carbon dioxide [34,35]. In Figure 6b, the decomposition of SMA started at 280.8 °C and reached the highest weight loss rate (3.5%/°C) at 400.1 °C.…”

Methods for the Synthesis of Phase Change Material Microcapsules with Enhanced Thermophysical Properties—A State-of-the-Art Review

“…This method is a heterogenous radical polymerization process that is used for the production of many common commercial resins, such as polyvinyl chloride (PVC) [94] polystyrene [95], and poly(methyl methacrylate) (PMMA) [96]. Over time, suspension polymerization has been used comprehensively for the synthesis of functional micro spheres [97] and for the fabrication of PCM microcapsules [43][44][45][46]. Figure 9a shows the formation process of mPCMs via free radical suspension polymerization.…”

“…Beyond this, they require a considerable reaction time, especially when considered for large-scale production. In that sense, suspension polymerization with the UV irradiation-initiated approach offers a better alternative to thermal treatment by reducing the polymerization time and energy consumption [45]. The technique also helps to retain the thermophysical properties of temperature-sensitive PCMs.…”

“…Other studies in this area have encapsulated PCMs of a higher melting temperature with an encapsulation efficiency not exceeding 70% [110]. Investigators from The University of Auckland (New Zealand) established a rapid, scalable, and energy-efficient way for the low-temperature microencapsulation of PCMs using both thin film UV reactor [111] and coiled-tube UV reactor [45]. Figure 10a,b show the schematic representation and experimental set up of the UV coiled-tube reactor.…”