基于分子模拟的聚醚醚酮拉伸力学行为与改性

Mechanical behavior and modification of poly-ether-ether-ketone using a molecular dynamics method

采用分子动力学方法预测聚醚醚酮(PEEK)的拉伸力学性能,对PEEK分子模型进行各向异性控压的非平衡态拉伸模拟,获得PEEK材料的应力-应变曲线,计算弹性模量、屈服强度等力学性能。分析不同应变率和温度下PEEK的力学性能、自由体积、均方回转半径和体系能量随拉伸应变的变化规律,进而解释PEEK分子链特征与材料宏观性能的关系。结果表明:随着应变率的增加,PEEK的弹性模量和屈服强度大幅提高;随着温度的增加,PEEK的弹性模量和屈服强度大幅降低;在拉伸弹性和屈服阶段体系的自由体积增加较快,分子链的均方回转半径基本不变,体系总势能以非键能为主。非键相互作用是影响PEEK弹性模量和屈服强度的一个主导因素,由此提出氨基修饰PEEK侧链的改性策略,结果表明,氨基官能化PEEK的弹性模量和屈服强度较PEEK分别提升21%和34%。

The molecular dynamics method was employed to predict the tensile mechanical properties of polyether-ether-ketone(PEEK). Non-equilibrium tensile simulation with anisotropic pressure control was employed to obtain the stress-strain curve of PEEK, and to calculate the elastic modulus, yield strength and other mechanical properties. The influences of the strain rate and temperature on the mechanical properties, free volume, mean square radius of gyration(Rg), and energy for PEEK were investigated to explain the relationship between PEEK chain characteristics and macro mechanical properties. The results indicate that the elastic modulus and yield strength of PEEK significantly increase with the increase of strain rate, and significantly decrease with the increase of temperature. In the elastic and yield stage, free volume linearly increases, and Rg of PEEK chains remains steady, and the non-bonded energy results in the amount of the total potential energy increase. The interchain non-bonded interactions play a dominant role in the elastic and yield performance. Therefore, the amino modification strategy is investigated to improve the mechanical property of PEEK. It is found that the elastic modulus and yield strength of PEEK modified by amino are increased by21% and 34% respectively than that of PEEK.