Various polymorphs of calcium carbonate and poly(ethylene) glycol as thermal energy storage materials

The present study investigates, thermal properties of polyethylene glycol (PEG) and various polymorphs of calcium carbonate (CaCO 3 ) as blends. The prepared calcite, aragonite, and vaterite forms of CaCO 3 were confirmed by x‐ray diffraction (XRD). Differential scanning calorimeter (DSC) revealed that, PEG‐calcite blend (composition 40/60 wt%), exhibited maximum enthalpy (112.9 ± 0.87 J/g). Aragonite and vaterite blends of similar composition displayed lower enthalpies (73.7 ± 0.61 J/g and 61.3 ± 0.75 J/g), which can be attributed to irregularities in crystal lattice and secondary interactions. Thermal gravimetric analysis (TGA) of PEG‐calcite revealed its impressive thermal stability, as blend was stable up to 423°C, higher than decomposition temperature of PEG. DSC analysis of PEG‐calcite after 50 cycles showcased excellent thermal reliability of blend, with enthalpy decreasing to only 108.5 ± 0.52 J/g. Stability of material was further supported by Fourier transform infrared spectroscopy (FTIR), where position and shape of peaks were found to be intact, suggesting no new compound formation. Field emission scanning electron microscopy (FESEM) suggested strong adhesion and wrapping of PEG around calcite particles, facilitated by cross‐hydrogen bonding between carbonate group and PEG. PEG‐calcite blend exhibited high thermal conductivity (0.74 ± 0.05 W/mK), highlighting potential applications in thermal management systems.