A comparative study of linear polyurea and crosslinked polyurea as supports to stabilize polyethylene glycol for thermal energy storage

Abstract To reveal the influence of organic polymer supports on the properties of shape stabilized phase change materials (ssPCMs), a linear polyurea (LP) and crosslinked polyurea (CP) were synthesized for stabilizing polyethylene glycol (PEG) for thermal energy storage. Though the surface area of LP are about 25 times of that of CP, the shape stability of CP for melt PEG is better than that of LP. Due to the crosslinked network, CP has much stronger interactions with PEG, which could promote the adsorption capacity of PEG. The highest PEG loading capability of LP and CP without liquid leakage above melting point is 70 wt% and 80 wt% respectively, and the corresponding melting enthalpy is 95.42 J/g and 107.60 J/g respectively. However, the heat storage efficiency of PEG/LP ssPCMs is higher than that of PEG/CP ssPCMs with the same PEG content, which caused by the weak restrictions of free movement of PEG chains from LP. Both types of ssPCMs exhibit good reusability from thermal cycle test and good thermal stability from thermal analysis, and the thermal conductivity of ssPCMs can effectively enhance after adding some carbon materials. The study supplied an inspiration to select proper polymer matrix for ssPCMs.