Effect of graphene nanoplatelets relative size and polyethylene chain length on the enhancement of thermal conductivity of their composite

In this paper, the thermal conductivity of polyethylene (PE) incorporated with graphene nanoplatelets (GNPs) has been studied using equilibrium Molecular Dynamics (eMD) simulations. A systematic MD simulation for PE-GNPs composites was performed with graphene weight percentage (wt.%) up to ∼40% to investigate the effect of the addition of GNPs on the thermal conductivity of PE. A significant improvement of thermal conductivity to around 80–120 W/(m·K) is reported at GNPs weight percentage of ∼40%. Moreover, the effect of chain length of PE at various wt.% of GNPs on the thermal conductivity of PE-GNPs nanocomposite versus the wt.% of GNPs are is studied using linear and second-order polynomial regression analysis. For PE matrix with 20-monomer chain length, which is comparable to the size of filling GNPs, the thermal conductivity has a linear relation when the weight percentage of GNPs is under 15%, and a quadratic polynomial relation over the whole simulated weight percentage. Thermal conductivity of PE matrix with 50 and 100-monomer exhibited two linear regions with respect to the GNPs weight percentage when the weight percentage is under 10% and above 30%. The effect of the GNPs/PE chain length relative size is well-explained using the number of connected polymer chain ends in the PE-GNPs composites. This study concludes that the relative size of the thermal conducting filling materials compared to the polymer chain lengths has distinguish effect on the thermal conductivity.