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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。
The structure, thermodynamics and mechanical properties of carbon nanotube / polyethylene composites were simulated by molecular dynamics method, and their changes with the simulation temperature and the filling rate of carbon nanotubes were analyzed. The simulation results show that the carbon nanotubes / polyethylene composites are isotropic amorphous structure, the polyethylene and the carbon nanotubes are bonded together by the strong Van der Waal’s effect. Under the action of the polyethylene matrix, Periodicity of the arrangement of carbon atoms decreased, bending and wrinkling. In terms of energy, the composites with higher filling rate are more stable. Carbon nanotubes / polyethylene composites have higher isocannatic heat capacity than polyethylene system and negative heat pressure coefficient opposite to polyethylene system. The heat capacity changes little with the filling rate of carbon nanotubes. However, Increased significantly and decreased significantly, with significant temperature effect. The change of thermal pressure coefficient with temperature was smaller and the temperature stability was better than that of polyethylene, but decreased with the increase of filling rate. The mechanical properties of carbon nanotube / polyethylene composites show elastic constant tensor, elastic modulus and Poisson’s ratio of isotropic materials are much higher than that of pure polyethylene system, and both increase with temperature and content of carbon nanotubes Lower and lower, indicating that adding carbon nanotubes can significantly improve the mechanical properties of polyethylene.