Temperature-sensitive and self-healing shape-stable phase change materials containing temperature adjustable ionic liquid for improving the recycling stability and the applicability in cold energy storage

Abstract

Advanced shape-stable phase change materials (SSPCMs) with environment self-adaptation are becoming more meaningful in regulating temperature in diverse applications. In this manuscript, a series of self-healing SSPCMs containing ionic liquids were fabricated by temperature-responsive polymers (PNIPAM) through the free radical polymerization method. 1-ethyl-3-methylimidazolium dicyanamide ([Emim][DCA]) ionic liquid was selected as the cooling agent and PCM. 2-ureido-4[1H]-pyrimidinone (UPy) and chitosan oligosaccharide (COS) were chosen as modifiers. Nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopy were used to determine the chemical structure. The surface morphology of SSPCMs was observed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and polarizing optical microscopy (POM). A rotational rheometer and electronic universal testing machine were used to assess the self-healing effectiveness and mechanical properties of SSPCMs. Thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to examine the thermal characteristics and thermal reliabilities of self-healing SSPCMs. The results indicate that the self-healing efficiency of SSPCM is 91.04 % within 5 min, and compressive strength is improved by 65.7 % by the ionic liquid. The SSPCMs perform thermo-sensitive properties, which allow SSPCMs to maintain a stable shape in response to temperature change and reduce PCMs leakage. Furthermore, the SSPCMs can quickly and effectively recover their mechanical properties after damage thanks to the excellent self-healing properties. Meanwhile, the SSPCMs have a longer lifespan for improving recycling efficiency and are more environmentally friendly. The developed SSPCMs with recycle stability have a high energy density (251.5 J/g) and adjustable phase change temperature properties. The developed SSPCMs can be made to fit various temperature applications by changing the concentration of ionic liquids in the phase change system. Overall, the SSPCMs show promising potential for cold energy storage and thermal management.