The effects of modified carbon nanotubes on the thermal properties of erythritol as phase change materials

•Modified-MWCNTs/Erythritol PCMs were developed and characterized.•The MWCNTs have negligible effects on the melting points and enthalpies of Ery.•The MWCNTs improved greatly the thermal conductivity and supercooling of Ery.•The functional groups on the MWCNTs affect the thermal cycling stability of Ery. Three different methods, acid oxidation, mechanochemical process and ball milling, were used to modify multi-walled carbon nanotubes (MWCNTs). The MWCNTs were dispersed into erythritol (Ery) to prepare composite phase change materials (PCMs). The effects of the MWCNTs on the thermal properties of erythritol-based composite PCMs were studied experimentally. FT-IR and XPS spectroscopy show that hydroxyl groups and carboxylic groups were generated on the surface of the MWCNTs after modification. The pretreatment of MWCNTs can improve their dispersibility in erythritol. When the mass fraction of MWCNTs was 1%, the thermal conductivity of Ery was increased obviously from 0.1956 W/(m·K) to 0.9779 W/(m·K). Besides, the MWCNTs could help improve the supercooling and solidification enthalpy of erythritol significantly. When the mass fraction of A-MWCNTs was only 0.5%, the freezing temperature of PCMs increased from 18.8 °C to 58.15 °C and the solidification enthalpy increased 50 J/g. After 10 heating and cooling cycles, the Ery/A-MWCNTs composites show a very good thermal cycling stability.