Key Insights into the Differences between Bimodal Crystallization Kinetics of Polyamide 66 and Polyamide 6
Key Insights into the Differences between Bimodal Crystallization Kinetics of Polyamide 66 and Polyamide 6
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关于聚酰胺 66 和聚酰胺 6 双峰结晶动力学差异的重要见解
DOI：
10.1021/acs.macromol.2c01059
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发表时间：
2022
期刊：
影响因子：
5.5
通讯作者：
Rhoades, Alicyn
中科院分区：
文献类型：
--
作者：
Zhang, Xiaoshi;Buzinkai, John;Quinn, Evan;Rhoades, Alicyn
聚酰胺66（PA66）和聚酰胺6（PA6）由于其相似的化学结构而具有许多相似的性能。然而，它们的结晶动力学和形态差异并不像其他性质那样被很好地理解。本文采用改进的快速扫描量热法研究了无添加剂的PA66和PA6在深过冷条件下的结晶动力学和结晶形态。两种聚酰胺显示出相似的动力学曲线和形态，但与多晶型物相关的转变发生在不同的温度下。关于动力学，PA66总是比PA6更快地结晶，无论形成的多晶型物如何，由温度依赖性Avrami动力学系数k支持。PA66和PA6均显示双峰动力学曲线，分别在135和110 °C下具有局部结晶速率最小值。除结晶速率外，在结晶速率最小值附近发现结晶放热峰突然变宽。用Avrami指数n从3到2的急剧变化来描述这种加宽。在微观和纳米尺度的聚酰胺的形态，其次是偏光显微镜（POM）和原子力显微镜（AFM）。POM显示，两种聚酰胺在接近速率最小值时从透明变为半透明。温度依赖性的AFM显微照片显示从无定形的形态，菜花状晶体，晶体聚集体，和层状结构afterTc变化从近Tg以上的动力学断裂温度的多步转变。尽管两种聚酰胺具有相似的分子量和相同的酰胺基团含量，但发现PA66中的形态转变总是比PA6高20 °C，这表明它们成核的热力学驱动力不同。在本研究的最后一部分从Avrami分析得出的结论提供了一个普遍的解释，在许多以前研究的热塑性塑料中观察到的急剧峰展宽。
Polyamide 66 (PA66) and polyamide 6 (PA6) share many comparable properties due to their similar chemical structures. However, their crystallization kinetics and morphological differences are not as well understood as other properties. This work establishes the crystallization kinetics and morphology of additive-free PA66 and PA6 at high undercooling conditions using a modified fast scanning calorimetry technique. Two polyamides show similar kinetics profile and morphology, but the transitions associated with polymorphs occur at different temperatures. Regarding kinetics, PA66 always crystallizes faster than PA6 regardless of the polymorphs formed, supported by the temperature-dependent Avrami kinetics coefficientsk. Both PA66 and PA6 show a bimodal kinetics profile with a local crystallization rate minimum at 135 and 110 °C, respectively. Apart from the crystallization rate, a sudden broadening of the exothermic crystallization peak is found near the rate minimum. The broadening is described by a drastic change of the Avrami indexnfrom 3 to 2. The morphology at the micro- and nanoscales of polyamides was followed by a polarized optical microscope (POM) and atomic force microscopy (AFM). The POM reveals that both polyamides turn translucent from transparent near the rate minimum. The temperature-dependent AFM micrographs show multistep transitions from amorphous-like morphology, cauliflower-like crystal, crystal aggregates, and lamellar structure afterTcchanges from nearTgto above the kinetics break temperature. Although two polyamides have similar molecular weight and the same content of amide groups, the morphological transition in PA66 is found to always be 20 °C higher than in PA6, suggesting a difference in their thermodynamic drive to nucleate. The conclusions drawn from the Avrami analysis in the final part of this study provide a universal explanation of the drastic peak broadening observed in many previously studied thermoplastics.
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DOI：
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发表时间：
1977
期刊：
影响因子：
--
作者：
Kazuo Inoue;S. Hoshino
通讯作者：
S. Hoshino
6-聚酰胺的结构、结构和晶体
DOI：
--
发表时间：
1971
期刊：
影响因子：
--
作者：
Von K.;H. Haberkorn
通讯作者：
H. Haberkorn
影响因子：
4.6
作者：
A. Rhoades;Nichole Wonderling;C. Schick;R. Androsch
通讯作者：
A. Rhoades;Nichole Wonderling;C. Schick;R. Androsch
影响因子：
5.5
作者：
A. Rhoades;A. Gohn;Jiho Seo;R. Androsch;R. Colby
通讯作者：
A. Rhoades;A. Gohn;Jiho Seo;R. Androsch;R. Colby
模拟聚酰胺 6 的结晶动力学和所得性能
DOI：
--
发表时间：
2021
期刊：
影响因子：
--
作者：
N. Yaghini;G. Peters
通讯作者：
G. Peters