Preparation and performance of a novel thermoplastics polyurethane solid–solid phase change materials for energy storage

Phase change materials (PCMs) are a series of functional materials with storing and releasing energy properties. PCMs are able to adjust and control the environment around them through storing and releasing energy during phase change process. Based on the phase change theory, bis(1,3-dihydroxypropan-2-yl)4,4′-methylenebis(4,1-phenylene)dicarbamate, a novel tetrahydroxy compound, was designed and synthesized. Depending on the spatial structure of the tetrahydroxy compound, the form-stable thermoplastic polyurethane solid–solid phase change material (TPUPCM) was prepared. In the molecular structure of TPUPCM, polyethylene glycol was employed as the soft segments, and the hard segments were made up of 4,4′-diphenylmethane diisocyanate and tetrahydroxy compound made up multi-benzene ring structure. The composition and structure, crystalline morphology, phase change behaviors, thermal performances and mechanical properties for tetrahydroxy compound and TPUPCM were investigated by using fourier transform infrared spectrometer (FT-IR), 1H nuclear magnetic resonance spectrometer (1H NMR), wide-angle X-ray diffraction (WAXD), polarizing optical microscopy (POM), differential scanning calorimentry (DSC), thermogravimetry analysis system (TGA) and Instron 5566 tensile tester. The TPUPCM's the weight average molecular weight, number average molecular weight, dissolving and mechanical abilities were also tested. The results show that the solid–solid phase-change material possesses excellent phase-change properties and an applicable temperature range. The heating cycle phase-change enthalpy is 137.4 J/g, and the cooling cycle phase-change enthalpy is 127.6 J/g. The decomposition of TPUPCM starts and reaches a maximum at 323.5 °C and 396.2 °C, respectively. Furthermore, the solid–solid phase-change material is dissolvable, meltable and can be processed directly, and has potential applications in thermal energy storage.