Molecular Dynamics Simulations of Polyamide-6 Composite with Covalently Bonded Graphene Network for Thermal Conductivity Enhancement

Abstract

Due to its ultrahigh in-plane thermal conductivity, graphene nanosheet is expected to significantly improve the thermal conductivity of polymer composites. However, it still lacks clarity that how such improvement is quantitatively influenced by the configuration of the graphene nanosheets. In this work, large-scale molecular dynamics simulations are performed to investigate the effect of size and chemical interconnectivity of the graphene nanosheets on the thermal conductivity of a graphene-reinforced polyamide-6 composite. We find that the thermal conductivity of such a composite can be appreciably improved if all of the graphene nanosheets are covalently bonded together and the average size of the graphene nanosheets is large. Fundamentally, the composite thermal conductivity benefits from more heat taking the path of the graphene architecture and less heat dissipating back into the polymer matrix through the graphene− polymer interface. Analytical modeling indicates that the configuration with largesized graphene nanosheets systematically joined by covalent intergraphene junctions is optimal to attract heat into the graphene architecture and restrain the interfacial heat dissipation, leading to better composite thermal conductivity. Our findings are crucial to understanding the physical mechanism of thermal conductivity enhancement of graphene nanosheets within a polymer matrix, which can be applied to develop highly efficient thermal interface materials.

Improved out-of-plane thermal conductivity of boron nitride nanosheet-filled polyamide 6/polyethylene terephthalate composites by a rapid solidification method

“…In the above models, the size of BNNSs is specified as 2.61 × 2.76 nm, PET possesses a hexameric molecular structure, 44 and the PA6 molecule contains six monomers. 45 The PCFF potential 46–49 was used to describe the atomic interactions in the PA6/PET system, and the Tersoff potential 50–53 was used to describe the interactions between BNNS layers. The interactions between the layers of BNNSs, BNNS/PET, and BNNS/PA6 are described by the Lennard-Jones (LJ) potential as follows:where r ij is the distance between atom i and atom j; ε ij is energy constant; σ ij is distance constant.…”

Thermal Conductivity of the Graphene/Polydimethylsiloxane Composite by Manipulating the Network Structure

“…Furthermore, the occurrence of thermal percolation in the polyamide matrix is potentially attributed to the inter-GE interaction transition from van der Waals interaction to chemical bonds . The impact of chemical bonds and size of GE on the thermal conductivity of a GE/polyamide composite is studied, which is significantly enhanced when all the GE with a large size are covalently bonded . However, the functionalization or defects in the GE fillers will lead to a reduction in the intrinsic thermal conductivity of GE, which is due to the shortening of the phonon mean free path. − This subsequently results in a lower heat transport efficiency of the composites.…”

High-Efficiency Preparation of Reduced Graphene Oxide by a Two-Step Reduction Method and Its Synergistic Enhancement of Thermally Conductive and Anticorrosive Performance for Epoxy Coatings

“…Graphene, a two-dimensional carbon material, possesses many outstanding properties, such as high thermal conductivity (∼5300 W/(m·K)), excellent electric conductivity, and being impermeable to corrosive media. − Graphene has been considered as the highest thermal conductive filler and the thinnest anticorrosive filler. Therefore, incorporating graphene or reduced graphene oxide (rGO) filler into an epoxy matrix has two obvious advantages: (1) forming a 3D thermal conductivity network that enhances the heat transfer property of epoxy coating , and (2) an effective labyrinth effect that significantly improves the corrosion protection performances of epoxy coating. , However, most of the research on epoxy/rGO only focuses on thermal conduction or anticorrosion performance, and there are few studies and reports on its synergistic enhancement of thermally conductive and anticorrosive performance.…”