Thermal Properties of Graphene Nanoplatelets Reinforced Crosslinked and Short Chain Branched Polyethylenes for Geothermal Pipe Applications

Two types of polyethylenes, the crosslinked high-density polyethylene (PEX) and the short-chain branched medium-density polyethylene (polyethylene of raised temperature resistance [PE-RT]), are selected as matrices for graphene nanoplatelets (GNPs) nanocomposites preparation (PEX/GNPs, PE-RT/GNPs). The melt-mixing technique is used to synthesize the nanocomposites containing various loadings of GNPs. Differential scanning calorimetry (DSC) is employed to study the effect of the GNPs on the melting and crystallization behavior of the prepared materials. The thermal stability of the nanocomposites was evaluated by thermogravimetric analysis (TGA). Laser flash analysis (LFA) is used to estimate the thermal conductivity of both PEX and PE-RT/GNPs nanocomposites. TGA measurements reveal that PEX nanocomposites present decreased thermal stability with increasing filler content. The DSC results show that the crystallinity of both matrices increases with increasing filler content. PEX/GNPs nanocomposites show more significant thermal conductivity augmentation compared to the corresponding PE-RT nanocomposites.