Polylactide (PLA) represents one of the promising biodegradable polymers with great potential to replace petroleum-derived plastic. In the last decade, massive efforts have been devoted to overcoming the brittleness of PLA, expecting comparable mechanical properties to traditional polyolefin and polyester. Introducing oriented texture into PLA has recently been reported to be an effective approach to improve ductility without sacrificing their high strength. However, the understanding of the mechanism is absent. Herein, we study the fracture behaviors of anisotropic PLA with oriented lamellar crystal by employing operando synchrotron X-ray scattering and diffraction. It has been found that the cavities generated parallel with stress direction can restrain the fast failure of PLA. Nevertheless, the load-carrying ability of oriented PLA lamella is still limited. On this basis, we further introduce the flexible nanofibers into an oriented PLA matrix that enables crystals to effectively participate in the stress dissipation, resulting in significant enhancement of the ductility of PLA while maintaining their high strength. Combined with morphological study by scanning electron microscope, we propose a qualitative model to describe the detailed fracture behavior of PLA with oriented texture, which may provide a reliable theoretical guideline towards further optimization of the mechanical properties of PLA.

中文翻译：

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了解空腔演化对定向织构聚丙交酯快速断裂的抑制作用

聚丙交酯（PLA）是一种有前途的可生物降解聚合物，具有替代石油衍生塑料的巨大潜力。在过去的十年中，人们致力于克服 PLA 的脆性，期望其机械性能可与传统聚烯烃和聚酯相媲美。最近有报道称，在 PLA 中引入定向织构是在不牺牲高强度的情况下提高延展性的有效方法。然而，缺乏对该机制的理解。在此，我们利用操作同步加速器X射线散射和衍射研究了具有取向层状晶体的各向异性PLA的断裂行为。研究发现，平行于应力方向产生的空洞可以抑制PLA的快速失效。尽管如此，定向PLA薄片的承载能力仍然有限。在此基础上，我们进一步将柔性纳米纤维引入到定向PLA基体中，使晶体能够有效参与应力耗散，从而在保持高强度的同时显着增强PLA的延展性。结合扫描电子显微镜的形貌研究，我们提出了一个定性模型来描述定向织构PLA的详细断裂行为，这可以为进一步优化PLA的力学性能提供可靠的理论指导。