相对简单地了解 PLLA 相当复杂的结晶动力学,Polymers

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相对简单地了解 PLLA 相当复杂的结晶动力学
Polymers ( IF 4.7 ) Pub Date : 2023-04-14 , DOI: 10.3390/polym15081880
Jorge López-Beceiro ₁ , Ana-María Díaz-Díaz ₁ , Enrique Fernández-Pérez ₁ , Ignatius Ferreira ₂ , Walter W Focke ₂ , Ramón Artiaga ₁

Affiliation

这项工作表明，尽管存在大量关于 PLA 结晶的工作，但仍然有一种相对简单的方法，与已经描述的方法不同，可以观察到其复杂的动力学。此处提供的 X 射线衍射 (XRD) 结果证实，所研究的 PLLA 主要以 α 和 α' 形式结晶。一个有趣的观察是，在所研究的图案范围内的任何温度下，X 射线反射都稳定在给定的形状和给定的角度，每个温度都不同。这意味着 α 和 α' 形式共存并在相同温度下稳定，因此每种图案的形状均由两种结构产生。然而，在每个温度下获得的图案是不同的，因为一种晶型优于另一种晶型取决于温度。因此，提出了一个双组分动力学模型来解释两种晶体形式。该方法涉及使用两个逻辑导数函数对放热 DSC 峰进行反卷积。除了两种晶型之外，刚性无定形部分（RAF）的存在增加了整个结晶过程的复杂性。然而，此处显示的结果表明，双组分动力学模型可以在很宽的温度范围内很好地再现整个结晶过程。此处用于 PLLA 的方法可用于描述其他聚合物的等温结晶过程。除了两种晶型之外，刚性无定形部分（RAF）的存在增加了整个结晶过程的复杂性。然而，此处显示的结果表明，双组分动力学模型可以在很宽的温度范围内很好地再现整个结晶过程。此处用于 PLLA 的方法可用于描述其他聚合物的等温结晶过程。除了两种晶型之外，刚性无定形部分（RAF）的存在增加了整个结晶过程的复杂性。然而，此处显示的结果表明，双组分动力学模型可以在很宽的温度范围内很好地再现整个结晶过程。此处用于 PLLA 的方法可用于描述其他聚合物的等温结晶过程。

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A Relatively Simple Look at the Rather Complex Crystallization Kinetics of PLLA

This work demonstrates that, despite the existence of a significant number of works on PLA crystallization, there is still a relatively simple way, different from those already described, in which its complex kinetics can be observed. The X-ray diffraction (XRD) results presented here confirm that the PLLA under study crystallizes mostly in the α and α′ forms. An interesting observation is that at any temperature in the studied range of the patterns, the X-ray reflections stabilize with a given shape and at a given angle, different for each temperature. That means that both α and α′ forms coexist and are stable at the same temperatures so that the shape of each pattern results from both structures. However, the patterns obtained at each temperature are different because the predominance of one crystal form over the other depends on temperature. Thus, a two-component kinetic model is proposed to account for both crystal forms. The method involves the deconvolution of the exothermic DSC peaks using two logistic derivative functions. The existence of the rigid amorphous fraction (RAF) in addition to the two crystal forms increases the complexity of the whole crystallization process. However, the results presented here show that a two-component kinetic model can reproduce the overall crystallization process fairly well over a broad range of temperatures. The method used here for PLLA may be useful for describing the isothermal crystallization processes of other polymers.

更新日期：2023-04-14

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