Preparation and characterization of thermoplastic poly(urethane‐urea) solid–solid phase‐change materials for thermal energy storage

Three kinds of thermoplastic poly(urethane‐urea) PCMs were synthesized by two‐step condensation polymerization for thermal energy storage. Polyethylene glycol (PEG) was employed as the phase‐change functional chain, and three kinds of diamine compounds were individually adopted as chain extender. The chemical structure, crystalline properties, phase‐change behaviors, thermal stabilities, and reliabilities were studied by Fourier transform infrared spectroscopy, X‐ray diffraction, polarizing optical microscopy, and thermogravimetric, respectively. The crystalline structure of synthesized thermoplastic PCMs is identical to pure PEG, but the spherulite size decreases to some extent due to the confined crystalline region. The synthesized thermoplastic PCMs have proper phase‐change temperature with high phase‐change enthalpy of about 88 J/g. The synthesized thermoplastic PCMs are stable at their processing and working temperature with the onset degradation temperature higher than 250°C, and tensile strength reaches 20.59 MPa. Thus, the synthesized thermoplastic PCMs can be processed into desirable shape for the special applications in energy storage.