Preparation of PLA with High Impact-Toughness and Reduced Internal Stress via Formation of Laminated, Bimodal Structure with Micro/Nanocells,Macromolecular Materials and Engineering

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Preparation of PLA with High Impact-Toughness and Reduced Internal Stress via Formation of Laminated, Bimodal Structure with Micro/Nanocells
Macromolecular Materials and Engineering ( IF 4.2 ) Pub Date : 2021-09-12 , DOI: 10.1002/mame.202100426
Pei Xiang ₁ , Siwen Bi ₁ , Fang Mei ₁ , Chang Deng ₁ , Dongdong Yu ₁ , Xuhang Chen ₁ , Peng Yu ₁

Affiliation

The pressure-induced-flow (PIF) processing method is used to fabricate oriented, self-toughening poly(lactic acid) (PIF-PLA) with excellent mechanical properties. However, residual internal stress in PIF-PLA may lead to their deformation and cracking. Hence, to eliminate internal stress, solid-state supercritical carbon dioxide foaming (sc-CO₂ foaming) is applied to PIF-PLA, with the resultant structure being called FOAM-PLA. The microstructure and mechanical properties of the PLAs are characterized pre- and post-foaming. Scanning electron microscopy results show PIF-PLA to exhibit oriented texture structures composed of staggered microfibers. Following sc-CO₂ foaming, the PIF-PLA is converted into a bimodal cellular structure consisting of micro and nano-cells. According to the 2D wide-angle X-ray diffraction and Raman spectra results, this structure of the FOAM-PLA can, through a marginal reduction of orientation, release significant amounts of internal stress. Moreover, the impact strength of FOAM-PLA is found to be 32.7 kJ m⁻², which is 10.2 times higher than that of crystalline PLA. This paper depicts the evolution of the PLA microstructure through the stages of PIF-processing and the subsequent solid-state sc-CO₂ foaming. Meanwhile, the mechanism of the internal stress reduction is promoted.

中文翻译：

通过形成具有微/纳米细胞的叠层双峰结构制备具有高冲击韧性和降低内应力的 PLA

压力诱导流动 (PIF) 加工方法用于制造具有优异机械性能的定向、自韧聚乳酸 (PIF-PLA)。然而，PIF-PLA 中的残余内应力可能导致其变形和开裂。因此，为了消除内应力，将固态超临界二氧化碳发泡（sc-CO ₂发泡）应用于PIF-PLA，所得结构称为FOAM-PLA。PLA 的微观结构和机械性能在发泡前和发泡后表征。扫描电子显微镜结果显示 PIF-PLA 表现出由交错的微纤维组成的定向纹理结构。继 sc-CO ₂发泡后，PIF-PLA 被转化为由微孔和纳米孔组成的双峰蜂窝结构。根据 2D 广角 X 射线衍射和拉曼光谱结果，FOAM-PLA 的这种结构可以通过略微减少取向来释放大量内应力。此外，发现 FOAM-PLA 的冲击强度为 32.7 kJ m ^-2，比结晶 PLA的冲击强度高 10.2 倍。本文描述了 PLA 微观结构通过 PIF 加工和随后的固态 sc-CO ₂发泡阶段的演变。同时，促进了内应力降低的机制。

更新日期：2021-11-15

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