Structure and thermal properties of octadecane/expanded graphite composites as shape-stabilized phase change materials

• OD/WEPG composites were prepared using a kneader mixing technique.
• OD was homogeneous mixed and effectively confined in the porous and layered structure of WEPG.
• The OD/WEPG composite with 30% WEPG content showed good thermal properties and shape-stability.

A series of shape-stabilized phase change materials (PCMs), composed of octadecane (OD) and expanded graphite (WEPG) (OD/WEPG), were prepared by using a kneader mixing technique. Chemical and morphological structure, shape-stability, thermal properties, and thermal stability of the OD/WEPG composites were investigated and characterized by Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmet–Teller (BET) analysis, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Composite properties were strongly dependent on the weight ratio of OD to WEPG. SEM and BET analysis showed that OD was adsorbed into the WEPG pores and uniformly covered the surfaces of WEPG, which helped to prevent leakage of melted OD during phase change from solid to liquid. Among the OD/WEPG composites, the OD/WEPG composite with 30% WEPG content showed good thermal properties and shape-stability. Based on these results, we anticipate that the OD/WEPG composites can be used in packaging materials to counteract the negative effects induced by unwanted temperature changes.