Preparation and characterization of polyethylene glycol/polyurea composites for shape stabilized phase change materials

A linear polyurea (LPU) and a crosslinked polyurea (CPU) were respectively synthesized by condensation between 4,4′-diaminodiphenyl methane and multivariate isocyanates, and then were used as supporting material to load polyethylene glycol (PEG) for shape-stabilized phase change materials (ssPCMs). LPU has an incompact flocculent morphology with higher surface area and pore volume than CPU, and CPU is composed of contiguous bead particles with many interspaces. The shape stability of PEG/CPU ssPCMs is better than that of PEG/LPU ssPCMs with the same PEG mass fraction due to the different molecular interactions between PEG and the polymer matrix. The maximum PEG mass fraction in PEG/LPU and PEG/CPU ssPCMs LPU are 65% and 75%, respectively, and the corresponding melting phase change enthalpies are 82.66 J/g and 98.13 J/g, respectively. The heat storage efficiency of PEG/CPU ssPCMs is smaller than that of PEG/LPU ssPCMs with the same PEG content, caused by the greater movement restriction of PEG chains from the crosslinked network of CPU. The prepared ssPCMs have favorable reusability after 100 heating–cooling thermal cycles and have good thermal stability below 250°C, which is helpful to widen extent of application for latent heat storage.