Preparation of a novel PEG composite with halogen-free flame retardant supporting matrix for thermal energy storage application

► Fire retardant shape-stabilized PEG composite was prepared by in situ sol–gel method. ► Composite was composed of inorganic–organic hybrid flame retardant supporting matrix. ► PEG composite had large latent heat and good thermal reliability. ► Novel supporting matrix increased fire retardancy and thermal stability of composite. ► PEG composite had potential to be utilized in thermal energy storage application. Poly (ethylene glycol) (PEG)/silsesquioxane composite was prepared by in situ sol–gel process. The structure of composite was characterized by solid state 31P and 29Si nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FT-IR). N2 adsorption–desorption measurement was used to investigate the porous structure of supporting matrix. Thermal and flame retardancy properties were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and pyrolysis combustion flow calorimetry (PCFC). Results indicated the PEG composite showed large latent heat (124.7kJ/kg). After thermal cycling for 1000cycles, the composite still had large latent heat of 124.1kJ/kg, showing the composite had good thermal reliability property. The composite had obvious increased intrinsic thermal stability through analysis of integral procedural decomposition temperature (IPDT). The peak of heat release rate (PHRR) of composite was decreased by 38.6% compared with pure PEG. And the time to PHRR was increased by 31s compared with pure PEG. The novel shape-stabilized PEG composite had potential to become halogen-free fire resistance phase change composite for thermal energy storage application.