碳纳米管/聚乙烯复合物分子动力学模拟研究

采用分子动力学方法模拟了碳纳米管/聚乙烯复合物的结构、热力学和力学特性，分析其随模拟温度和碳纳米管填充率的变化。模拟结果表明，碳纳米管/聚乙烯复合物为各向同性的无定形结构，聚乙烯和碳纳米管通过较强的范德华作用结合在一起，在聚乙烯基体作用下，碳纳米管壁上的碳原子排列的周期性下降，出现弯曲和褶皱。从能量上看，填充率较高的复合物更加稳定。碳纳米管/聚乙烯复合物具有比聚乙烯体系更高的等容热容和与聚乙烯体系相反的负值热压力系数，热容随碳纳米管填充率的变化较小，但随温度的升高而明显减小，具有显著的温度效应；热压力系数随温度的变化较小，温度稳定性比聚乙烯更好，但随填充率增加而减小。碳纳米管/聚乙烯复合物的力学特性表现出各向同性材料的弹性常数张量，弹性模量和泊松比比纯聚乙烯体系高得多，并且都随温度的升高和碳纳米管含量的降低而减小，说明加入碳纳米管可显著改善聚乙烯的力学性质。

Molecular dynamics simulation study of carbon nanotube/polyethylene nanocomposites

Molecular dynamics simulations of carbon nanotube/polyethylene composites have been implemented to calculate the structures, thermodynamical and mechanical properties, investigating their relationship with the filling rate and simulation temperature. The results show that carbon nanotube/polyethylene composites are in isotropic amorphous structures, with the polyethylene and carbon nanotubes combining together by intense van der Waals force. The periodicity of carbon atomic arrangement on carbon nanotube wall declines within the effects of polyethylene matrix, representing flexural and plicate deformations. Based on the energy consideration, the higher stability can be obtained with more carbon nanotube filling in composites. The carbon nanotube/polyethylene composites also exhibit higher isometric heat capacities, and negative thermal pressure coefficients with better temperature stability, which decrease explicitly with increased temperature and composite filling rate respectively, compared with polyethylene system. The mechanical properties of carbon nanotube/polyethylene composites present isotropic elastic constant tensors with substantially higher elastic modulus and Poisson ratio than those of polyethylene system, both of which decline with elevated temperature and reduced carbon filling simultaneously, indicating the extraordinary improvement in mechanical properties with the carbon nanotube filler.