As one of the duplicated cases of ultrathin polymer films, multilayer graphite/polymer composites are of great interests in various applications. Graphite/polyethylene (PE) composites with various layer numbers and graphite particle sizes were prepared by lamination. The mechanical and dielectric properties and crystalline behavior of the composites were investigated by scanning electron microscopy, differential scanning calorimetry, tensile test, and dielectric strength test. With the same amount of graphite addition, the tensile strength of the composites increases with decreasing layer thickness, but decreases with increasing graphite particle size. The longitudinal tensile strength is greater than the transverse one. The tensile strength of the 3 6 -layer composites with a particle size of 15 μm has enhancements of 34.76 and 68.39% in the longitudinal and transverse directions compared with that of the single-layer pure PE film. The dielectric constant of the composites nonlinearly increases with decreasing layer thickness, while the dielectric loss is independent of this factor. The dielectric constant of the 3 6 -layer composites with a particle size of 15 μm is about two times as large as that of the single-layer pure PE film. The crystalline peak temperature and the crystallinity of the composites increase with the decrease in layer thickness. Coarsegrained molecular dynamics simulations were also carried out to understand the experimental observations by getting an insight into the microstructure of the multilayer composites. This work would be helpful for the production of optimized of multilayer graphite/polymer composites by lamination for electric energy storage.

As a stacking form of ultrathin polymer films, multilayer nanostructures are of great interest in various applications. Coarse-grained molecular dynamics simulations were carried out to understand the confinement effects on the orientation of graphene sheets in multilayer polymer films during lamination. The influences of position, strain rate, expansion type, and arrangement pattern on the orientation of graphene sheets in the near-boundary and internal layers were considered. It was found that the confinement effects induce the graphene sheets to gradually orient parallel to the plane of the layer during lamination. Such effects are more obvious in the near-boundary layer than in the internal layer. With the same strain, a smaller strain rate gives rise to more obvious effects on the in-plane orientation of graphene sheets in both the near-boundary and internal layers. Biaxial expansion also makes the graphene sheets orient more parallel to the plane of the layer. This work is helpful for better understanding the lamination process and the designing of multilayer nanocomposites.

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