Thermal properties of polyethylene glycol/carbon microsphere composite as a novel phase change material.

Polyethylene glycol (PEG) as phase change materials has been extensively studied. However, it is difficult to uniformly disperse the PEG in the unmodified matrix material owing to the impregnation problem. It is therefore challenging to overcome the shortcoming of low thermal conductivity. In order to solve this problem, carbon microspheres (CMPs) prepared by the hydrothermal method is firstly proposed as the supporting matrix for preparation of PEG composite. The PEG/CMPs composite is prepared via a mutual diffusion methodology in a high-temperature environment. The test result shows the CMPs nano-material has rich oxygen-based functional groups and can be uniformly dispersed in the PEG phase. As the carbon content increases, the CMPs become gradually connected in the PEG/CMPs composite, which can result in a network with good thermal conductivity. Compared with the thermal conductivity of pure PEG, the thermal conductivity of the composite is increased by 65.07%. Owing to the existence of hydrogen bonds in the composite, the crystallinity fraction of the PEG is in the range of 102-105%. It means that the test result is higher than the theoretical value of latent heat for the composite. Finally, its cycling performance was measured. After 500 thermal cycles, the phase transition temperature of the composite remains almost constant, and the latent heat values of the melting and freezing decrease by 1.05 and 1.45%, respectively. The PEG/CMPs composite would be a promising material for thermal energy storage applications and can be used in various engineering disciplines. [ABSTRACT FROM AUTHOR]