聚丙烯/富勒烯复合材料热力学性能分子动力学模拟

Molecular Dynamics Simulation of Thermodynamic Properties of Polypropylene/Fullerene Composites

为了改善聚丙烯(PP)的热力学性能,使其在高压电缆中得到更好的实际应用,从微观层面探讨掺杂富勒烯(C_(60))对PP热力学性能的影响,采用分子动力学方法建立了纯PP,PP/C_(60)及掺杂羟基和氨基修饰的C_(60)复合体系(PP/C_(60)-OH和PP/C_(60)-NH_(2))的4组分子模型,计算了各模型的内聚能密度、溶解度参数、相互作用能、热导率、玻璃化转变温度(T_(g))、自由体积分数、不同温度下的弹性模量和体积模量与剪切模量之比。结果表明,富勒烯C_(60)、经羟基和氨基修饰的C_(60)都与PP有良好的相容性,且均能改善PP的热力学性能。热性能方面,PP/C_(60)-OH和PP/C_(60)-NH_(2)体系的热导率较纯PP体系分别提高了9.18%和15.82%,T_(g)从256 K分别提高到279 K和286 K。力学性能方面,复合材料刚性降低,PP/C_(60)-OH和PP/C_(60)-NH_(2)体系的弹性模量较纯PP分别降低了5.99%和9.51%,韧性增强,PP/C_(60)-NH_(2)体系的增韧效果最好,PP/C_(60)-OH体系次之。综合分析四种体系的热力学仿真结果表明,加入经氨基修饰的C_(60)改善PP的热力学性能最明显,PP/C_(60)-NH_(2)复合材料具有更优异的综合性能,同时为抑制PP热老化及开发环保型电缆材料提供参考。

In order to improve the thermodynamic properties of polypropylene(PP)and make it better applied in high-voltage cables,the effect of doped fullerene(C_(60))on the thermodynamic properties of PP was discussed from the microscopic level.Four molecular models of pure PP,PP/C_(60)and C_(60)composite systems(PP/C_(60)-OH and PP/C_(60)-NH_(2))modified with hydroxyl and amino groups were established by molecular dynamics method.The cohesive energy density,solubility parameter,interaction energy,thermal conductivity,glass transition temperature,free volume fraction,elastic modulus and ratio of volume modulus to shear modulus at different temperatures were calculated for each model.The results show that fullerene C_(60),hydroxyl and amino modified C_(60)has good compatibility with PP,and could improve the thermodynamic properties of PP.In terms of thermal properties,the thermal conductivity of PP/C_(60)-OH and PP/C_(60)-NH_(2)systems is increased by 9.18%and 15.82%,respectively,compared with pure PP systems,and the glass transition temperature is increased from 256 K to 279 K and 286 K respectively.In terms of mechanical properties,the rigidity of the composite decreases,the elastic modulus of PP/C_(60)-OH and PP/C_(60)-NH_(2)system decreases by 5.99%and 9.51%respectively compared with pure PP,and the toughness increases.The toughening effect of PP/C_(60)-NH_(2)system is the best followed by PP/C_(60)-OH system.A comprehensive analysis of the thermodynamic simulation results of the four systems shows that the addition of amino modified C_(60)has the most obvious improvement in the thermodynamic properties of PP,and PP/C_(60)-NH_(2)composite has better comprehensive properties,and provides a reference for inhibiting the thermal aging of PP and developing environmentally friendly cable materials.