Abstract Currently Polyethylene terephthalate (PET) foam is the most promising structural core materials, and the tensile mechanical properties are one of its important application indicators. Herein, environmental-friendly supercritical CO2 (ScCO2) extrusion foaming was adopted to prepare PET foam. Aiming at investigating the influence of crystals on the mechanical properties, isothermal treatment in the post-process was used to improve the crystallization process of PET foams. Due to the crystal perfection proceeds via migration and rejection of the structural defects at the crystallites induced by slow crystallization, the crystallinity increased rapidly with the rise of isothermal temperature, especially above the glass transition temperature (Tg). Qualitatively, it can be concluded that the crystalline phase contents have an intimate positive correlation with the tensile modulus, meanwhile, the shape ratio of the crystal have no significant effects on the tensile modulus. In addition, a coupling scheme of aggregate two-layered composite inclusion model and Simone-Gibson equation was first proposed to quantify the mathematical relationship between crystallization and tensile modulus of PET foam, which realized basic agreement.

中文翻译：

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结晶对PET泡沫拉伸力学性能的影响：实验与模型预测

摘要 聚对苯二甲酸乙二醇酯（PET）泡沫是目前最有发展前景的结构芯材，拉伸力学性能是其重要的应用指标之一。在此，采用环保型超临界 CO2 (ScCO2) 挤出发泡制备 PET 泡沫。为研究结晶对力学性能的影响，在后工序中采用等温处理来改进PET泡沫的结晶过程。由于通过迁移和排斥缓慢结晶引起的微晶处的结构缺陷来实现晶体完美，因此结晶度随着等温温度的升高而迅速增加，尤其是在玻璃化转变温度（Tg）之上。定性地，可以得出结论，晶相含量与拉伸模量呈密切的正相关，同时晶体的形状比对拉伸模量没有显着影响。此外，首次提出了骨料两层复合夹杂模型与Simone-Gibson方程的耦合方案，量化了PET泡沫结晶与拉伸模量之间的数学关系，实现了基本一致。