纳米SiO2增强脲醛树脂机械性能的分子模拟研究

介电材料广泛应用于现代电网,但容易出现开裂现象,引起局部放电、电树枝等危害。将芯材为双环戊二烯,壁材为脲醛树脂(PUF)的自修复微胶囊掺杂进介电材料,可实现材料的自修复。但PUF微胶囊硬度不足,其机械性能需要增强。文中采用分子模拟方法建立3组模型,每组分别包括一个纯PUF模型和一个掺杂纳米SiO2的PUF模型,经过计算后分析其密度、自由体积分数、机械性能,建立PUF/SiO2界面相互作用模型以挖掘其内部机理。结果发现,掺杂纳米SiO2有利于增大PUF材料的密度,减小自由体积分数、增强其机械性能。原因是PUF链上的极性原子和纳米SiO2表面的羟基、O原子之间存在氢键相互作用。文中采用分子模拟技术揭示了纳米SiO2增强PUF机械性能的内部机理。

Molecular simulation study on mechanical properties of poly (urea-formaldehyde) reinforced by nano-SiO2

Dielectric materials are widely used in modern power grids. However, cracking phenomena easily occurs in the us-ing process, and it may lead to partial discharge, electrical treeing, and even system failure. Micro-cracks are diffi-cult to detect, and the replacement of dielectric materials requires a lot of manpower, material resources, and fi-nancial resources. Therefore, self-healing materials came into being. The self-healing of dielectric materials can be realized by doping with self-healing microcapsules of which dicyclopentadiene as core material and poly (urea-formaldehyde) (PUF) as wall material. However, PUF microcapsules have insufficient hardness and mechanical properties need to be enhanced. In this paper, three sets of models were established by molecular simulation. Each group included a pure PUF model and a PUF model doped with nano-SiO2. The density, fractional free volume and mechanical properties were analyzed after molecular dynamics calculation. Results showed that doping nano-SiO2 is beneficial to increase the density of PUF materials, reduce the fractional free volume and enhance the mechanical properties. It was found that there are hydrogen bonds interactions between the polar atoms of PUF chain and hydroxyl as well as O atoms on the surface of nano-SiO2 by analyzing the interaction mechanism of PUF/SiO2 inter-face.