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通过分子动力学模拟对聚乙烯-石墨纳米片复合物的结构、力学和气体输运性质进行计算研究,分析其随模拟温度和石墨纳米片填充量的变化规律,探讨纳米界面形成和复合机制以及结构与特性关系。聚乙烯/石墨纳米片复合物呈现二维结构,石墨纳米片趋向于平面取向排列并通过范德华力和纳米石墨片层表面上的碳氢-π键使周围几个原子尺度内的聚乙烯分子固化为有序原子层,而聚乙烯基体仍然为各向同性的无定形结构。聚乙烯-石墨纳米片界面上纳米复合作用使体系能量降低,与聚乙烯体系相比杨氏模量和泊松比分别显著增高和降低。石墨纳米片平面取向导致力学特性表现出二维各向异性的弹性常数张量,在石墨纳米片层平面方向上的杨氏模量明显增高,并且随温度的降低和石墨纳米片填充量的提高而增大,填充石墨纳米片有效改善了聚乙烯的力学性质。聚乙烯-石墨纳米片复合物的气体输运性质明显受到填充石墨纳米片的气体阻隔和取向的影响并且对三种气体渗透没有明显的选择性。石墨纳米片与基体的纳米复合导致氮气、氧气和二氧化碳的分子输运呈现二维各向异性,随着石墨纳米颗粒填充量的增加,取向石墨纳米片层面方向的扩散系数比垂直方向高5~8倍,可用于气体分子屏障与渗流控制。
Through the molecular dynamics simulation, the structure, mechanics and gas transport properties of polyethylene-graphite nanosheet composites were calculated and studied. The variation regularity with the temperature and the filling amount of graphite nanosheets were analyzed to discuss the mechanism of nanocomposite formation and recombination Structure and characteristics of the relationship. The polyethylene / graphite nanosheet composites showed a two-dimensional structure. The graphite nanosheets tended to be oriented in a planar orientation and the polyethylene molecules in several atomic scales around them were cured by the van der Waals force and the hydrocarbon-π bond on the surface of the nanocrystalline graphite sheets For the ordered atomic layer, while the polyethylene matrix is still isotropic amorphous structure. The nanocomposite effect on the surface of the polyethylene-graphite nanosheets reduced the energy of the system, and the Young’s modulus and Poisson’s ratio of the polyethylene-graphite nanosheets were significantly increased and decreased compared with the polyethylene system. The planar orientation of the graphite nanosheet leads to the two-dimensional anisotropy of the elastic constant tensor and the Young’s modulus in the plane direction of the graphite nanosheet obviously increase. With the decrease of temperature and the increase of the filling amount of the graphite nanosheet, Increasing, filling graphite nanosheets effectively improve the mechanical properties of polyethylene. The gas transport properties of the polyethylene-graphite nanosheet composites are significantly affected by the gas barrier and orientation of the filler graphite nanoplatelets and have no obvious selectivity for the three gas infiltrations. The nanocomposite of graphite nanosheets and matrix lead to two-dimensional anisotropy of molecular transport of nitrogen, oxygen and carbon dioxide. With the increase of graphite nanoparticle loading, the diffusion coefficient of oriented graphite nanosheets in the layer plane direction is 5 ~ 8 times, can be used for gas molecular barrier and seepage control.