Breaking graphite through a ball-milling process: the thermal conductivity and mechanical properties of polyethylene composites

Abstract

Exfoliated graphite platelets (EGPs) have attracted extensive attention owing to their exceptional combinations of thermal conductivity and mechanical properties. Mechanical exfoliation is a facile and high-throughput approach to produce single-layer or few-layer graphite platelets. Herein, octadecylamine (ODA)-grafted EGP (ODA@EGP) and subsequent polyethylene/ODA@EGP (PE/ODA@EGP) composites with different contents of ODA@EGPs were successfully prepared via ball-milling and melt-mixing methods, respectively. The thermal conductivity, crystallinity, and mechanical properties of the composites were investigated using tensile tests, the hot-wire method, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, and thermogravimetric analysis (TGA). The results demonstrated that the thermal conductivity, mechanical properties, and thermal stability of the composites can be improved by regulating the additive contents of ODA@EGPs. When the content of ODA@EGPs was 10 wt%, the thermal conductivity of the composite reached up to 1.276 W (m^-1 K^-1), which is 216% higher than that of bare PE, while the tensile strength of the composite was 38.4% higher than that of PE. Additionally, thermal decomposition temperature increased by 16.2 °C. Therefore, the PE/ODA@EGP nanocomposites have great application potential in thermal management.

Fig. 1. SEM images of GP platelets: (a) GP and (b) ODA@EGP.

Fig. 2. (a) FTIR spectra and (b) TGA curves of GP and ODA@EGP.

Fig. 3. Raman spectra of GP and ODA@EGP.

Fig. 4. XRD patterns of the ODA@EGP, PE, and PE/ODA@EGP composites with different ODA@EGP contents.

Fig. 5. DSC curves for PE and PE/ODA@EGP composites: (a) reheating and (b) cooling.

Fig. 6. TGA curves of PE and PE/ODA@EGP composites with different ODA@EGP contents.

Fig. 7. (a) Thermal conductivity and (b) enhancement ratio of the PE/GP composites with different GP contents.

Fig. 8. SEM images of the frozen fracture surfaces of the composites with different ODA@EGP contents: (a) 0 wt%, (b) 2 wt%, (c) 4 wt%, (d) 6 wt%, (e) 8 wt%, and (f) 10 wt%.