Fabrication and Performance of Shape-Stable Phase Change Composites Supported by Environment-Friendly and Economical Loofah Sponge Fibers for Thermal Energy Storage

Abstract

Exploration of low-cost, short-process, environment-friendly, and well-behaved phase change composites is of great significance. The renewable biomass loofah sponge (LS) fibers exhibit superior characteristics such as unique microtubules, substantial micrometer-scale channels, and exceptionally high porosities and have great potential of being utilized to exploit high-performance phase change composites. Herein, we proposed a facile strategy for fabricating a novel shape-stable phase change composite (PCLS) supported by LS fiber microtubules incorporating polyethylene glycol (PEG). The LS fibers with a porous tubular structure provided superior encapsulation and mechanical support for PEG. Encapsulation capacity of LS fibers for PEG was not affected by the duration of vacuum impregnation but increased with the increase in PEG concentration (lower than 0.24 g/mL) and then tended to the maximum of ∼56.5%. Differential scanning calorimetry results showed that the resultant PCLS had a melting/crystallization temperature of 41.7/32.3 °C and a heat enthalpy of 98.9/86.1 J/g, which contributed to great thermal energy storage/retrieval capability. The fabricated PCLS also featured excellent thermal cycling reliability for long-term use. Thermogravimetric analysis results suggested that there were two steps of degradation process for the resultant PCLS and corresponded to the decomposition of PEG and LS fibers, respectively. Infrared thermal images demonstrated that the resultant PCLS showed good infrared stealth ability and could effectively reduce infrared heat radiation. Self-assembly temperature control performance measurement indicated that the fabricated PCLS displayed superior temperature regulation ability. Such innovative PCLS holds great promise for widespread applications in solar thermal-energy storage, thermal regulation, thermal insulation, and thermal camouflage and stealth.