The effect of the molecular weight and polydispersity index on the thermal conductivity of Polyamide 6: A molecular dynamics study. (June 2020) - Ghahramani, Nikoo
Highlight: Reverse non-equilibrium molecular dynamics simulations (RNEMD) is used to investigate thermal conductivity of Polyamide 6. Thermal conductivity of Polyamide 6 increases with the Degree of Polymerization (DOP) and reaches a constant value at high DOPs. Polydispersity Index (PDI) does not have a significant influence on the thermal conductivity of the Polyamide 6. The thermal conductivity increases linearly with the density. The thermal conductivity is highly affected by the Fraction of Free Volume (FFV) of the system. Abstract: In this study, the influence of both molecular weight (expressed as the degree of polymerization (DOP)) and Polydispersity index (PDI) on the thermal conductivity of Polyamide 6 (Nylon 6) were investigated by means of reverse non-equilibrium molecular dynamics simulations (RNEMD). At first, physical properties such as density and the solubility parameter were calculated to confirm the accuracy of the simulation results. Afterwards, variations in thermal conductivity with DOP and PDI were investigated. The simulation results show that the thermal conductivity of Polyamide 6 is 0.25 ± 0.002 W/(mK) which is in good agreement with the experimental data of 0.24–0.25 W/(mK). In addition, based on the simulation results, the thermal conductivity of Polyamide 6 has increased with the DOP and a plateau has been achieved at high DOPs. It was observed that varying PDI does not have a significant effect on the thermal conductivity at a constant value of average molecular weight. The dependency of thermal conductivity to the polymer density was also investigated and it was observed that by enhancing the polymer density, the thermal conductivity increases linearly. It was also concluded that the thermal conductivity is severely affected by system's fraction of free volume.