摘要
对位芳纶绝缘纸以其优异的介电性能、力学性能在电气绝缘领域得到广泛应用。为探究不同功能化碳纳米管与对位芳纶共掺的复合材料热力学性能,该文通过分子动力学模拟方法建立了对位芳纶分子体系模型、未功能化碳纳米管以及分别接枝羟基、羧基和氨基官能团的芳纶/功能化碳纳米管复合体系模型。在Materials Studio和LAMMPS中计算了复合材料热导率、玻璃化转变温度、力学性能、结构参数及相对介电常数。结果表明,芳纶复合材料体系各项性能均有不同幅度提升。芳纶/羧基化碳纳米管(PPTA/CNT—COOH)的热导率较掺杂前提升了75.4%,玻璃化转变温度提升了43.29 K。芳纶/羟基化碳纳米管(PPTA/CNT—OH)和芳纶/氨基化碳纳米管(PPTA/CNT—NH2)的热导率依次提升70.2%和63.2%。在力学性能上,复合材料比掺杂前的弹性模量平均增强30%以上,剪切模量增强15%以上。通过计算体系结构参数,从均方位移、自由体积占比、氢键数量与结合强度等分子层面阐释了材料性能增强的内在机理,最终发现PPTA/CNT—COOH在热力学性能上较其他掺杂体系提升最为明显,且碳纳米管的掺入未对材料介电常数引起较大改变,所得结果可为对位芳纶复合绝缘材料的掺杂设计、性能调控提供理论支持。
Para-aramid paper based materials are widely used in the field of electrical insulation because of their excellent dielectric and mechanical properties.However,pure para-aramid materials have poor thermal conductivity,which cannot dissipate the heat generated in the operation of electrical equipment in time.Recently,researchers have doped nanoparticles into para-aramid fiber to improve its thermal conductivity,and carbon nanotubes(CNT)have attracted much attention for the excellent thermal conductivity and mechanical properties,but there are few reports on the properties of functional carbon nanotubes doped para-aramid composite system.This paper constructs the models of pure para-aramid,non-functionalized,hydroxylated,carboxylated and aminated carbon nanotube-doped aramid composites.Materials Studio and LAMMPS were used for molecular dynamics simulation to obtain the thermal conductivity,glass transition temperature,mechanical properties and structural parameters.The properties of different material systems are analyzed and the mechanism explanation is provided from the molecular level.Firstly,NEMD simulation was carried out in LAMMPS to calculate the thermal conductivity.The thermal conductivity of arylon composites doped with carbon nanotubes was significantly improved,among which the thermal conductivity of PPTA/CNT-COOH had the greatest change,and was increased by 75.2%compared with pure PPTA molecules,PPTA/CNT-OH and PPTA/CNT-NH2 were increased by 70.1%and 63.2%respectively.Then,the glass transition temperatures(Tg)of different material models were obtained by specific volume-temperature curve method.The Tg of PPTA/CNT-COOH increased by 43.29 K,and the Tg of PPTA/CNT,PPTA/CNT-NH2 and PPTA/CNT-OH increased by 27.03 K,35.52 K and 39.74 K,respectively.In the calculation of mechanical properties,the static constant strain method is used to press a certain direction of stress on the surface of the material,and Young's modulus E and shear modulus G are solved by the obtained stiffness matrix.The results show that the doping of carbon nanotubes can enhance the elastic modulus of composites by more than 30%and shear modulus by more than 15%,among which the mechanical properties of PPTA/CNT-COOH are enhanced most obviously,and the damage effect of temperature rise on mechanical properties is reduced to a certain extent.In the calculation of structural parameters,the FFV,MSD and the number of hydrogen bonds were calculated respectively,and the reasons for the changes in the above thermodynamic properties were explained from the perspective of intermolecular interaction and molecular chain movement.On the one hand,carbon nanotubes have excellent thermal conductivity and mechanical properties,and doping can promote the performance improvement of the composite system by enhancing the strength of the matrix network skeleton.On the other hand,hydrogen bonds were formed between the functionalized carbon nanotubes and aramid molecules,which enhanced the interaction between molecules and formed a stronger molecular network,and improved the stability of the system.Due to the difference of electronegativity of N and O and the number of grafts,there are PPTA/CNT-COOH>PPTA/CNT-OH>PPTA/CNT-NH2 in the number and strength of hydrogen bonds.The relationship is reflected in the gain variation of thermodynamic properties of the composite system.The results show that the thermodynamic properties of the carboxylated carbon nanotubes aramid composite system are better than those of other functionalized doping systems,and the doping of functionalized carbon nanotubes does not change the dielectric constant of the composite system significantly,hence,it can still provide excellent insulation and protection properties.
作者
张文琦
范晓舟
李宇轩
庾翔
律方成
Zhang Wenqi;Fan Xiaozhou;Li Yuxuan;Yu Xiang;LüFangcheng(College of Electrical and Electronic Engineering North China Electric Power University,Beijing 102206 China;Hebei Key Laboratory of Power Transmission Equipment Security Defense North China Electric Power University,Baoding 071003 China)
出处
《电工技术学报》
EI
CSCD
北大核心
2024年第5期1510-1523,共14页
Transactions of China Electrotechnical Society
基金
国家自然科学基金(51777076)
中央高校基本科研业务费专项资金(2019MS083)资助项目。
关键词
电气绝缘
芳纶
功能化碳纳米管
分子动力学
热力学性能
Electrical insulation
aramid fiber
functionalized carbon nanotubes
molecular dynamics
thermodynamic performance
