丁苯橡胶应力软化的全原子分子动力学模拟

doi:10.16085/j.issn.1000-6613.2024-2113

摘要/Abstract

摘要：

橡胶材料的应力软化是指经多次循环加载（拉伸-恢复）后应力降低的现象，是影响相关工程应用效果和工程安全的重要因素。利用全原子分子动力学模拟方法，本文研究了丁苯橡胶材料的应力软化现象，从分子尺度探索和总结了应力软化的微观特征和关键影响因素。研究发现，丁苯橡胶的应力软化是由链间相互作用决定的，高分子总动能和势能分布是描述链间相互作用的重要方法。苯环基单元在丁苯橡胶总动能分布和总势能分布中发挥着主导作用。这是因为它们在丁苯橡胶分子中以侧支链的形式存在，且具有较大的体积。丁烯基单元在总动能分布中也发挥着主要作用，却几乎不影响总势能分布。乙烯基单元不是影响总动能、总势能分布的主要因素。在相同应变下，体系中自由体积随着循环拉伸次数增加而增大，并逐渐形成集中而连续的空腔，这些空腔是应力软化现象的重要微观结构特征。

关键词: 丁苯橡胶, 应力软化, 马林斯效应, 微观动力学, 分子模拟

Abstract:

Stress softening of rubber materials refers to the phenomenon of stress reduction after multiple cycles of loading (tension-recovery). This phenomenon is a critical factor affecting the effectiveness of related engineering applications and engineering safety. The present study investigated the stress softening phenomenon of styrene-butadiene rubber materials by using all-atoms molecular dynamics simulations. The study explored and summarized the microscopic features and critical factors of stress softening from the molecular scale. The results indicated that the stress softening of styrene-butadiene rubber was determined by interchain interactions. The total kinetic and potential energy distributions of macromolecules were critical for the characterization of interchain interactions. Styrene group units played a dominant role in the total kinetic energy distribution and the total potential energy distribution of SBR,due to the presence in the SBR molecule as side-branched chains and the large size. The butenyl group units exerted a significant influence on the total kinetic energy distribution. However, its impact on the total potential energy distribution was negligible. In contrast, the vinyl group unit played a negligible role in both the total kinetic energy and total potential energy distributions. At the same strain, the free volume in the system increased with the number of cyclic strains and gradually formed concentrated and continuous cavities. These cavities were important microstructural features of the stress softening phenomenon.

Key words: styrene-butadiene rubber, stress-softening, Mullins effect, micro-dynamics, molecular simulation

中图分类号:

O631.2⁺1

刘力涵, 王琪君, 王轩, 彭阳峰, 徐小飞. 丁苯橡胶应力软化的全原子分子动力学模拟[J]. 化工进展, 2025, 44(8): 4331-4340.

LIU Lihan, WANG Qijun, WANG Xuan, PENG Yangfeng, XU Xiaofei. All-atom molecular dynamics simulation on stress softening of styrene-butadiene rubber[J]. Chemical Industry and Engineering Progress, 2025, 44(8): 4331-4340.

图/表 6

图1 丁苯橡胶模型示意图白色球体—氢原子；绿色球体—碳原子

图2 循环加载时的丁苯橡胶材料力学行为（链长为120）

图3 各橡胶分子单元的动能和势能（εmax=2）

图4 循环加载过程中自由体积变化率

图5 多次循环加载过程中自由体积分布（应变固定为0，链长为60）

图6 循环加载过程中主要单元的特征键角自相关函数和定义方式

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