This study analyzed the fracture behavior of poly(lactic acid) (PLA)/polybutylene succinate (PBS)/thermoplastic starch (TPS) blends featuring nanoscale-dispersed core–shell structures using molecular dynamics (MD) simulations, elucidating the toughening mechanisms at the molecular-level. Four models (PLA/TPS25, PLA/PBS/TPS5, PLA/PBS/TPS25, and PLA/PBS/TPS50) with varying core–shell structure parameters were utilized in the MD simulations. The fracture energy relationship obtained from the deformation simulation was PLA/PBS/TPS25 > PLA/PBS/TPS5 > PLA/PBS/TPS50 ≈ PLA/TPS25, which generally reproduced the experimental results of the impact test of the blends. The entire material was fractured by delamination at the TPS/PLA interface in the PLA/TPS25, and at the TPS/PBS interface in the PLA/PBS/TPS50 with the thinnest PBS shell. The PLA/PBS/TPS5 with the thickest PBS shell exhibited a reduced toughening effect due to the formation of numerous voids in the PLA matrix phase during deformation. In PLA/PBS/TPS25 with an intermediate thickness PBS shell, moderate-density voids formed during deformation, releasing strain constraints and effectively strengthening the material. The orientation hardening of PLA and PBS that occurs during deformation also contributes to the deformation energy absorption of PLA/PBS/TPS25. The molecular-level toughening mechanism elucidated in this study is anticipated to contribute to the enhancement of the properties of a wide range of bioplastics containing polysaccharides.

中文翻译：

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从分子角度增韧核壳生物塑料材料的基本原理


本研究使用分子动力学 （MD） 模拟分析了具有纳米级分散核壳结构的聚乳酸 （PLA）/聚丁二酸丁二醇酯 （PBS）/热塑性淀粉 （TPS） 共混物的断裂行为，阐明了分子水平的增韧机制。MD 模拟使用了具有不同核壳结构参数的四种模型 （PLA/TPS25、PLA/PBS/TPS5、PLA/PBS/TPS25 和 PLA/PBS/TPS50）。变形模拟得到的断裂能量关系为PLA/PBS/TPS25 > PLA/PBS/TPS5 > PLA/PBS/TPS50 ≈ PLA/TPS25，总体上再现了共混物冲击试验的实验结果。在 PLA/TPS25 的 TPS/PLA 界面处，以及 PBS 壳最薄的 PLA/PBS/TPS50 中的 TPS/PBS 界面处，通过分层使整个材料断裂。PBS 壳层最厚的 PLA/PBS/TPS5 由于在变形过程中在 PLA 基体相中形成大量空隙，因此增韧效果降低。在具有中等厚度 PBS 壳的 PLA/PBS/TPS25 中，在变形过程中形成中等密度空隙，释放了应变约束并有效地增强了材料。变形过程中发生的 PLA 和 PBS 取向硬化也有助于 PLA/PBS/TPS25 的变形能量吸收。本研究中阐明的分子水平增韧机制有望有助于增强各种含有多糖的生物塑料的性能。