Phase change and thermal energy storage properties of polyurethane phase change materials with mixed soft segment and crosslinking structure

Abstract

A series of polyurethane phase change materials (PUPCMs) with different structures were successfully synthesized using polyethylene glycol(PEG), polycarbonate(PCDL), or polytetramethylene ether glycol(PTMG) as single or mixed soft segment, isophorone diisocyanate (IPDI) as the hard segment, and trimethylolpropane(TMP) or neopentyl glycol(NPG) as the chain extender. The structure and functional groups of synthesized PUPCMs were demonstrated by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (1HMR). The properties of PUPCMs were characterized and analyzed by polarizing optical microscope (POM)-hot stage system, X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), infrared camera and hardness test. The results showed that PUPCMs with crosslinking structure presented smaller spherulites than linear PUPCMs and the crosslinking structure had relatively strong effect on crystallization of soft segments. Crystallization mechanism of linear PUPCMs and crosslinking PUPCMs were both homogeneous nucleation. The interaction of different soft segment imposed restrictions on the movement of the mixed soft segment chain. The PUPCMs samples based on three mixed soft segment（PEG/PCDL/PTMG）and TMP as chain extender exhibited the lowest phase transition temperature of 30.23℃ and phase change enthalpies of 54.01 J/g. The synthesized PUPCMs showed excellent thermal stability, reliability and good mechanical properties for application as thermal energy storage materials at medium-low temperature conditions.