Thermal conductivity and degradation behavior of HDPE/graphene nanocomposites: Pyrolysis, kinetics and mechanism

Abstract

Graphene-filled high-density polyethylene nanocomposites varying filler’s size (5, 10 and 25 × 10−6 m in diameter) were prepared by the melt-mixing method, and their thermal properties are then investigated by TG, Py–GC/MS and thermal conductivity measurements. Thermal and thermo-oxidative degradation temperatures of HDPE/graphene nanocomposites were substantially improved with increment of filler content and graphene size. According to kinetic analysis of thermal decomposition, the thermal degradation mechanism of HDPE/graphene nanocomposites may efficiently be described by an nth-order model with autocatalysis (Cn). Meanwhile, the activation energy values versus the partial mass loss revealed that graphene nanoparticles take up the heat and obstruct transport of HDPE degradation products efficiently. It was also found that the decomposition in nanocomposites is taking place mainly via chain scission reaction, followed by β-scission propagation reactions, radical reactions and the termination process. Graphene nanocomposites achieved significant improvements in thermal conductivity at low filler concentrations, while the experimental data are in good agreement with the Hatta–Taya theoretical model. Summing up the influence of filler size on thermal properties of polymer matrix, graphene nanoparticles with the higher diameter (25 × 10−6 m) affect more than graphene of 5 × 10−6 and 15 × 10−6 m. © 2017, Akadémiai Kiadó, Budapest, Hungary.