To date, polylactic acid (PLA) composites with a uniform dispersion of fillers have been extensively studied. However, there is little research about the shape memory (SM) behavior of a PLA composite in which the nanoclays have a nonuniform dispersion. In this paper, the alkaline calcium bentonite (ACBT) was first modified by citric acid (CA) to improve the compatibility between bentonite (BT) and PLA. The structure of CA-modified bentonite (CABT) was characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Then the CABT/PLA composite with gradient concentration of CABT in thickness direction was fabricated. Because of the good affinity between the grafted CA and the ester groups, the CABT imposed powerful restrictions on the PLA chains, which contributed to the anisotropic driving force for shape recovery. The relationship between the structure and the properties and the mechanism of anisotropic SM behavior of composite were studied.

中文翻译：

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厚度方向上具有梯度填充剂浓度的聚乳酸/柠檬酸-膨润土复合材料的各向异性形状记忆行为

迄今为止，已经对填充剂均匀分散的聚乳酸（PLA）复合材料进行了广泛的研究。但是，关于纳米粘土具有不均匀分散的PLA复合材料的形状记忆（SM）行为的研究很少。本文首先对柠檬酸钙膨润土（ACBT）进行了柠檬酸（CA）改性，以提高膨润土（BT）与PLA的相容性。通过傅立叶变换红外光谱（FT-IR），热重分析（TGA），X射线衍射（XRD）和扫描电子显微镜（SEM）对CA改性膨润土（CABT）的结构进行了表征。然后制备厚度方向上浓度梯度为CABT的CABT / PLA复合材料。由于接枝的CA与酯基之间的亲和力好，因此CABT对PLA链施加了强大的限制，这有助于形状恢复的各向异性驱动力。研究了复合材料的结构与性能之间的关系以及各向异性SM行为的机理。