AbstractWe studied the elongational crystallization of poly(ethylene terephthalate) (PET) from the melt using polarizing optical microscope and X-ray observation. We verified that the structure and morphology discontinuously changed from conventional stacked lamellae of folded chain crystals (FCCs) to nano-oriented crystals (NOCs) when the elongational strain rate ($$\dot \varepsilon $$ε°) exceeded a critical value of $$(\dot \varepsilon ^*) \cong 10^2\,{\mathrm{s}}^{ - 1}$$(ε°*)≅102s-1. Therefore, the universality of NOC formation was verified. We found that the NOCs of PET show a novel three-dimensional (3D) structure and morphology: (i) nanocrystals (NCs) were arranged in a monoclinic lattice, which is a specific morphology for NOCs of PET, compared to iPP, and (ii) the unit cell structure of NOCs was a triclinic system with biaxial orientation. We showed the important role of the primary structure of the plate, such as a benzene ring, in the formation of a novel 3D structure and the morphology of the NOCs of PET. We also clarified that the NOCs of PET showed high performance, such as a high heat resistance temperature (Th)$$\ \cong\ $$≅281 °C, a high melting temperature (Tm)$$\ \cong\ $$≅285 °C, high maximum tensile stresses for the machine direction (MD) and transverse direction (TD)$$\ \cong\ $$≅2.8 × 102 and 74 MPa, respectively, and high Young’s moduli for MD and TD $$\ \cong\ $$≅5.4 and 1.7 GPa, respectively.We studied the elongational crystallization of poly(ethylene terephthalate) (PET) from the supercooled melt. We found that the novel three-dimensional (3D) structure of “nano-oriented crystals (NOCs)” was formed, where nanocrystals (NCs) were arranged on monoclinic lattice. We observed the structure and morphology of NOCs by means of polarizing optical microscope and small/wide angle X-ray scatterings. We clarified the important role of a primary structure of the plate-like benzene ring in the formation of the NOCs of PET. We also showed high performance of NOCs of PET, such as high heat resistance temperature and high maximum tensile stress.

中文翻译：

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通过从熔体中拉伸结晶形成的聚（对苯二甲酸乙二醇酯）纳米取向晶体的 3D 结构

摘要我们利用偏光显微镜和 X 射线观察研究了聚对苯二甲酸乙二醇酯 (PET) 从熔体中的拉伸结晶。我们证实，当伸长应变率（$$\dot \varepsilon $$ε°）超过临界值时，结构和形态从折叠链晶体（FCCs）的传统叠层片层不连续地变为纳米取向晶体（NOCs）。 $$(\dot \varepsilon ^*) \cong 10^2\,{\mathrm{s}}^{ - 1}$$(ε°*)≅102s-1。因此，验证了NOC形成的普遍性。我们发现 PET 的 NOCs 显示出一种新的三维 (3D) 结构和形态：(i) 纳米晶体 (NCs) 排列在单斜晶格中，与 iPP 相比，这是 PET 的 NOCs 的特定形态，并且（ ii) NOCs 的晶胞结构是双轴取向的三斜晶系​​。我们展示了板的一级结构（如苯环）在形成新的 3D 结构和 PET 的 NOC 形态中的重要作用。我们还阐明了 PET 的 NOCs 表现出高性能，例如高耐热温度 (Th)$$\\cong\$$≅281 °C，高熔点 (Tm)$$\\cong\$$ ≅285 °C，纵向 (MD) 和横向 (TD) 的最大最大拉伸应力 $$\ \cong\ $$≅2.8 × 102 和 74 MPa，分别为 MD 和 TD $$ 的高杨氏模量\ \cong\ $$≅5.4 和 1.7 GPa，分别。我们研究了聚对苯二甲酸乙二醇酯 (PET) 从过冷熔体中的拉伸结晶。我们发现形成了“纳米取向晶体（NOCs）”的新型三维（3D）结构，其中纳米晶体（NCs）排列在单斜晶格上。我们通过偏光显微镜和小/广角X射线散射观察了NOCs的结构和形态。我们阐明了片状苯环的一级结构在PET NOCs形成中的重要作用。我们还展示了 PET 的 NOC 的高性能，例如高耐热温度和高最大拉伸应力。