Crystallization mechanism of micro flake Cu particle-filled poly(ethylene glycol) composites

Abstract

Poly(ethylene glycol) (PEG) is used as phase change materials while the low thermal conductivity restricted the thermal storage efficiency. Incorporation of the metal particles (MPs) into PEG could enhance the thermal conductivity while the crystallization kinetic mechanism of the MP-filled PEG composites is altered. Flake MPs are characterized with layer structure and a large aspect ratio, while there are few research works related to the effect of flake MPs on the crystallization kinetic mechanism of flake MP-filled polymer composites. In this work, different micro flake copper (Cu) particles contents were introduced into the PEG matrix via the physical blending method. The Fourier transform infrared instrument (FT-IR) was used to characterize the chemical compatibility of the PEG/Cu composites. The differential scanning calorimetry (DSC) method was to characterize the crystalline kinetic mechanism of the micro flake Cu particle-filled polymer composites by using the isothermal model and non-isothermal model. It was found that the COC conformation of the confined PEG in the composites was altered, and more helical conformations were transferred from the zigzag conformations. The addition of the Cu particles in the PEG matrix enhanced the heterogeneous nucleation meantime hindered the diffusion of the PEG molecular chains. As a result, the crystallization rate of the PEG/Cu composites was optimized only when there was a middle Cu content in the PEG matrix (14.89 wt% in this work). Additionally, the PEG/Cu composites had 3D PEG crystal growth geometry in the isothermal crystallization process while the stronger dependence of the PEG crystal growth geometry on the temperature was found in the non-isothermal crystallization especially when the Cu amount was higher than 14.89 wt%.