Molecular Simulation of Amorphous Polymer and Its Carbon Nanotube Based Composites

Abstract

Since their discovery in 1991, carbon nanotubes (CNTs) have been the focus of considerable research due to their remarkable physical and mechanical properties reported. This form of carbon has potential applications in numerous conventional and new areas - light-weight structural materials being just one of them. The strength to weight ratio of CNTs is higher than any currently known material; hence their use to reinforce polymers has been of great interest. Due to the highly expensive testing equipment and limited scope of experimental techniques, atomistic and continuum simulations are being used for characterization of CNTs and CNT based nanomaterials. This research concentrates on molecular dynamics simulations (MDS) of amorphous polyethylene and CNT- polyethylene composites. The composite being investigated consist of amorphous polyethylene with embedded single-walled CNT. The CNT is modeled by the Brenner potential while united-atom approach is used for modeling the polymer chains CH2 (methylene) group as a single united atom in the polymer system. The van der Waals interaction between the nanotube and polymer is modeled using Lennard-Jones potential. All the systems were subjected to quasi-static tensile loading. For simplicity, no cross-link chemical bond between the CNT and polyethylene matrix in the nanocomposites is considered. Here, mechanical properties of amorphous polymer and its CNT reinforced composites have been investigated using MDS. The effects of polymer density, polymer chain length and temperature on the mechanical properties of polymer have been studied. In case of composite the effects of CNTs volume fraction on the mechanical properties of CNT-Polyethylene composite have been checked and compared with the existing theoretical formula. The load transfer scenario through the interfacial region has also been investigated here and compared with the existing theoretical Cox’s model.