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研究了非晶态聚苯乙烯材料应力松弛行为与其固有微观结构非均匀性之间的关联, 从基本Maxwell黏弹性模型出发, 到三参量扩展指数方程, 讨论了变形单元特征时间的分布本质及聚合物应力松弛过程中的链段效应. 结果表明, 非晶态聚苯乙烯应力松弛行为呈现典型非指数特征, 单一特征时间的指数衰减形式与有限特征时间的有限谱方法均无法合理描述聚苯乙烯应力松弛行为, 这是由于非晶态聚合物微观结构非均匀性所导致的特征时间谱连续分布. 此外, 本文进一步探究了物理老化导致的应力松弛行为变化, 老化导致体系向更稳定能量状态迁移, 变形单元难以激活, 因而导致应力松弛过程慢化, 特征时间延长.The relationship between stress relaxation behavior and inherent microstructural heterogeneity in amorphous polystyrene materials is studied in this work. Starting from the basic Maxwell viscoelastic model and extending to the three-parameter stretched exponential equation, the nature of the distribution of characteristic timescales and the segmental effects during polymer stress relaxation are discussed. The results indicate that the stress relaxation behavior of amorphous polymers exhibits non-exponential characteristics. Neither a single characteristic time with exponential decay nor a finite spectrum method with finite characteristic time can adequately describe the stress relaxation behavior of polystyrene due to the continuous distribution of characteristic timescales resulting from microstructural heterogeneity in amorphous polymers. In addition, the changes in stress relaxation behavior caused by physical aging are explored. Aging leads to a transition of the system towards a more stable energy state, making it difficult to activate the relaxation of the individual units, thus slowing down the stress relaxation process and increasing the characteristic time.
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Keywords:
- polystyrene/
- stress relaxation behavior/
- viscoelastic deformation/
- microstructural heterogeneity
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