ISSN   1004-0595

CN  62-1095/O4

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尹宇航, 雷浩, 宋敬伏, 赵盖, 丁庆军. 改性石墨烯增强聚四氟乙烯摩擦学性能的分子模拟研究[J]. 摩擦学学报, 2022, 42(3): 598-608. DOI: 10.16078/j.tribology.2021139
引用本文: 尹宇航, 雷浩, 宋敬伏, 赵盖, 丁庆军. 改性石墨烯增强聚四氟乙烯摩擦学性能的分子模拟研究[J]. 摩擦学学报, 2022, 42(3): 598-608. DOI: 10.16078/j.tribology.2021139
YIN Yuhang, LEI Hao, SONG Jingfu, ZHAO Gai, DING Qingjun. Molecular Dynamics Simulation on the Tribological Properties of Polytetrafluoroethylene Reinforced with Modified Graphene[J]. TRIBOLOGY, 2022, 42(3): 598-608. DOI: 10.16078/j.tribology.2021139
Citation: YIN Yuhang, LEI Hao, SONG Jingfu, ZHAO Gai, DING Qingjun. Molecular Dynamics Simulation on the Tribological Properties of Polytetrafluoroethylene Reinforced with Modified Graphene[J]. TRIBOLOGY, 2022, 42(3): 598-608. DOI: 10.16078/j.tribology.2021139

改性石墨烯增强聚四氟乙烯摩擦学性能的分子模拟研究

Molecular Dynamics Simulation on the Tribological Properties of Polytetrafluoroethylene Reinforced with Modified Graphene

  • 摘要: 采用分子动力学模拟研究了接枝改性氧化石墨烯对聚四氟乙烯(PTFE)的增强作用与摩擦学性能的影响,首先选用KH550、KH560和KH570三种硅烷偶联剂接枝氧化石墨烯(GO),在填入纯聚四氟乙烯后计算其机械性能与摩擦性能. 对比得出KH560的增强效果最好,杨氏模量和剪切模量分别提高了205%和116%,摩擦系数提高了39.6%. 然后选用聚酰亚胺(PI)接枝氧化石墨烯,对比了接枝改性与物理共混两种方式对增强效果的影响,结果表明接枝改性的增强效果优于物理共混. 最后通过分析界面间相互作用力、结合能、原子相对浓度和原子运动速度等方式揭示了接枝氧化石墨烯对聚四氟乙烯基体的增强机理.

     

    Abstract: Improving the performance of polytetrafluoroethylene (PTFE) becomes a popular research area, which plays an important role on the actual application in the aerospace, machinery, chemical industry field, and so on. The common enhancement methods for polymer are filling fibers, nanosheets and micro-nano particles. However, the reinforced mechanism has not been fully understood, especially under an atomic level due to experimental measurement limitation. In this study, we employed a molecular dynamics (MD) simulation to study the tribological properties of PTFE reinforced by modified graphene with excellent mechanical strength in order to explore the reinforced mechanism from a molecular view. Firstly, graphene oxidation (GO), as a reinforced filler, was grafted by three different silane coupling agents, KH550, KH560 and KH570, to improve the interfacial compatibility with PTFE matrix, respectively. The calculation results indicated that PTFE composites filled by KH560-GO had the highest Young's modulus and shear modulus, which was increased by 205% and 116%, respectively. Then, the frictional model of PTFE composites sliding against copper based on the contact of ultrasonic motors was built and the tribological properties was evaluated. The simulated results showed that the friction coefficient of PTFE was increased by 39.6% after filling the KH560-GO. The shear deformation was also greatly reduced after filling GO modified by silane coupling agents. Besides, the polyimide (PI) with high rigidity was selected to modify GO to further improve the mechanical strength of PTFE. The ungrafted GO and single PI molecular were also filled in the PTFE matrix to compare the effect of modification. It was obviously found that the PI grafted GO had the higher Young’s modulus and shear modulus than that just filling GO blended with single PI molecular, increased by 71.2% and 56.9%, respectively. Finally, the reinforcement mechanism was systematically analyzed by observing the dynamic evolution of whole shear process and extracting the variation information of the interface characteristics. Visually, silane coupling agents and PI molecular had the favorable compatibility with PTFE molecular which resulted in the strong interfacial interaction due to mechanical interlocking effect. The PI chains were grafted almost vertically on the surface of GO. Thus, the silane coupling agents and PI grafted GO had the higher interaction potential energy with PTFE than single graphene or PI blends. More PTFE molecular were adsorbed on the surface of modified GO under the van der waals, electrostatic adsorption and other forces, which contributed to high mechanical strength and shear modulus. Under the same shear condition, silane coupling agents and PI modified GO reinforced PTFE had a smaller shear deformation than pure PTFE and graphene nanosheets (GNS) reinforced PTFE. After further analysis on the frictional interface, it can be easily found that the temperature, velocity, relative concentration variation and interaction energy with counterpart was different after filling different GO. On the frictional interface, pure PTFE had higher atomic velocity, relative concentration and interaction energy because of strong intermolecular forces with copper atoms. After reinforced with modified GO, more PTFE chains were adsorbed on the surface of GO, which reduced the interaction with counterpart. It was consistent with friction reduction, wear resistance and mechanical performance improvement. This study revealed the enhancement mechanism of modified GO on the PTFE using MD simulations from an atomic level, which had a helpful guidance for designing other polymer composites reinforced by different fillers.

     

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