超临界二氧化碳流场作用下线型聚乙烯剪切塑化行为的分子动力学模拟研究

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中文摘要：通过非平衡分子动力学模拟探讨了聚乙烯(PE)及其与超临界二氧化碳(scCO2)共混体系在剪切流下的热力学和构象性质.发现scCO2的增塑作用可显著改变PE的热力学和构象性质,如降低分子间作用力、减少体系剪切应力、降低体系黏度、减少分子链构象参数、提高PE链gauche plus构象,从而增加分子链的卷曲和自由体积,减少剪切下的分子取向排列.scCO2还显著降低了体系的弛豫时间,加强了PE分子链抵抗剪切的能力,从而增强了动态性质和热稳定性.这些发现为scCO2在PE体系中的作用提供了微观见解,为调控scCO2辅助聚合物加工工艺,开发高性能聚合物材料提供了理论依据.

外文标题：Molecular Dynamics Simulation Study on the Shear Plasticizing Behavior of Linear Polyethylene under the Influence of Supercritical Carbon Dioxide Flow Field

外文摘要：This research comprehensively examines the thermodynamic behavior and conformational changes in polyethylene(PE)and its blends with supercritical carbon dioxide(scCO2)under shear flow conditions using non-equilibrium molecular dynamics(NEMD)simulations,which uncovers the influence of scCO2,acting as a plasticizer,on the thermodynamic and conformational properties of PE.The study reveals that scCO2 diminishes intermolecular forces and shear stress within the system,leading to a reduction in viscosity and alterations in the conformational parameters of PE molecular chains.These changes result in an increased free volume and curling of the molecular chains,with a notable decrease in molecular orientation alignment under shear,thereby,enhancing the system's dynamic properties and thermal stability.By analyzing parameters such as stress(τxy and σv)-strain(γ)curves,mean square end-to-end distance(Rete),radius of gyration(Rg),orientation parameters(P2θ),and the autocorrelation function of the relaxation process under three shear flow,the peak shear stress τxy decreased from 0.18 in the PE system to 0.068 in the PE+scCO2 system at(γ)=4.686×10-1 τ-1,and both Rete and Rg decreased.The persistence length lp of the PE chains is three times that of the PE+scCO2 system.Additionally,the distribution of the molecular chain dihedral angle's gauche plus conformation is reduced,and the trans conformation distribution has increased.The research elucidates that the presence of scCO2 reduces the system's Rouse time τR by approximately 3.9 times,highlighting the plasticizing effect of scCO2,which could effectively promote the conformational freedom and mechanical adaptability of PE under shear flow.This work not only provides deep insights into the complex interactions between PE and scCO2,but also showcases the potential of utilizing scCO2 as a sustainable processing aid in the development of high-performance polymer materials.The findings offer a theoretical foundation for regulating scCO2-assisted polymer processing techniques and advancing the understanding of the dynamic response of polymer systems to external shear.

外文关键词：

Linear polymerSupercritical carbon dioxideNon-equilibrium molecular dynamicsShear orientationShear flowPlasticizing effect

作者：

崔文豪、顾瑞星、米皓阳

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作者单位：

郑州大学橡塑模具国家工程研究中心郑州 450000

关键词：

线型聚合物超临界二氧化碳非平衡分子动力学剪切取向剪切流增塑作用

基金：

国家自然科学基金河南省科技研发计划联合基金优势学科培育项目中国博士后面上基金

项目编号：

521730492223014200322021M701797

出版年：

2024

DOI：

10.11777/j.issn1000-3304.2024.24076

高分子学报

中国科学院化学研究所中国化学会

高分子学报

CSTPCD北大核心

影响因子：0.844

ISSN：1000-3304

年,卷(期)：2024.55(10)