Li Bowen, Liao Guangkai, Liu Yuejun, Cao Kaikai, Li Yuankang, Xie Zhenyan, Yin Haomin, Cui Lingna
Key Laboratory of Advanced Packaging Materials and Technology of Hunan Province, Hunan University of Technology, Zhuzhou, 412007, China.
Zhuzhou Times Engineering Plastics Industrial Co., Ltd, Zhuzhou, 412008, China.
Sci Rep. 2024 Sep 27;14(1):22169. doi: 10.1038/s41598-024-73513-6.
Polyamide 6 (PA6) films with significant α relaxation process was selected as the model system. The creep behavior and rheological mechanism during deformation in the amorphous regions of semi-crystalline polymers are systematically investigated by carrying out creep experiments. Based on the quasi point defect (QPD) theory, the complete physical process of PA6 film creep behavior from elasticity to viscoelasticity and viscoplasticity was analyzed and modeled from the perspective of structural heterogeneity. The results demonstrate that the creep deformation of PA6 film is a typical thermo-mechanical coupling and nonlinear mechanics process, and potential creep mechanisms corresponds to stress-induced local shear deformation enhancement and thermal activation-induced particle flow diffusion. The elastic-plastic transition involved in the creep deformation process of semi-crystalline polymer originates from the activation of quasi-point defective sites in the amorphous region, the expansion of sheared micro-domains and irreversible fusion. The generalized fractional Kelvin (GFK) model is proposed, and the physical meaning of parameters is explained by combining the quasi point defect theory and creep delay spectrum(L(τ)). Finally, the effectiveness of the GFK model and the QPD theory in studying the deformation behavior of PA6 films was validated by comparing experimental data with theoretical results, which theoretically reveals the structural evolution of PA6 film during creep process.
选择具有显著α松弛过程的聚酰胺6（PA6）薄膜作为模型体系。通过进行蠕变实验，系统地研究了半结晶聚合物非晶区在变形过程中的蠕变行为和流变机理。基于准点缺陷（QPD）理论，从结构非均匀性的角度分析并建立了PA6薄膜从弹性到粘弹性和粘塑性蠕变行为的完整物理过程模型。结果表明，PA6薄膜的蠕变变形是典型的热-机械耦合和非线性力学过程，潜在的蠕变机制对应于应力诱导的局部剪切变形增强和热激活诱导的颗粒流扩散。半结晶聚合物蠕变变形过程中涉及的弹塑性转变源于非晶区准点缺陷位点的激活、剪切微区的扩展和不可逆融合。提出了广义分数开尔文（GFK）模型，并结合准点缺陷理论和蠕变延迟谱（L(τ)）解释了参数的物理意义。最后，通过将实验数据与理论结果进行比较，验证了GFK模型和QPD理论在研究PA6薄膜变形行为方面的有效性，从理论上揭示了PA6薄膜在蠕变过程中的结构演变。
