Probing Three Distinct Crystal Polymorphs of Melt-Crystallized Polyamide 6 by an Integrated Fast Scanning Calorimetry Chip System
Probing Three Distinct Crystal Polymorphs of Melt-Crystallized Polyamide 6 by an Integrated Fast Scanning Calorimetry Chip System
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DOI：
10.1021/acs.macromol.1c00811
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发表时间：
2021-08
期刊：
影响因子：
5.5
通讯作者：
Xiaoshi Zhang;A. Gohn;G. Mendis;J. Buzinkai;S. Weigand;A. Rhoades
中科院分区：
文献类型：
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作者：
Xiaoshi Zhang;A. Gohn;G. Mendis;J. Buzinkai;S. Weigand;A. Rhoades
利用先进的快速扫描量热仪(FSC)在较宽的温度范围内研究了尼龙6(PA6)的等温结晶行为。采用微聚焦傅里叶变换红外光谱技术，直接在FSC芯片上采集PA6的温度相关光谱。在酰胺和亚甲基相关带中观察到的变化提供了PA6中熔融结晶的三种结晶修饰的直接证据。发现熔融结晶尼龙6在105℃以下形成介晶β相，在150℃以上形成α相，证实在105~150℃温度范围内，γ相与β或α相共存。在β-相和γ-相之间的过渡区发现了结晶动力学的特殊不连续性。在相同的温度范围内，原子力显微镜捕捉到了从晶体聚集体到球晶形态的突然转变。在等温结晶前，PA6以10~2000K/S的速率冷却，以模拟全方位的加工相关条件。根据动力学数据建立了PA6的时间-温度-转变图，说明PA6的等温结晶对结晶路径很敏感。建立在改性FSC芯片上的新型平台是全面研究加工相关条件下聚合物结晶的有力工具。
Isothermal crystallization of polyamide 6 (PA6) was studied using a state-of-the-art modified fast scanning calorimetry (FSC) chip over a wide temperature range. Microfocus FTIR spectroscopy was carried out to collect temperature-dependent spectra of PA6 directly on the FSC chip. The changes observed in amide- and methylene-related bands provide direct evidence of three crystalline modifications in PA6 from melt crystallization. The melt-crystallized PA6 was found to develop the mesomorphic β-phase below 105 °C and the α-phase above 150 °C. It has been confirmed that the γ-phase coexists with the β- or α-phase in the temperature region between 105 and 150 °C. Isothermal crystallization kinetics of PA6 in a wide temperature range were extracted directly from exothermic peaks and indirectly using the interruption method. A peculiar discontinuity in crystallization kinetics has been found in the transition region between the β- and γ-phases. In the same temperature region, a sudden transition from crystal aggregates to spherulitic morphology was captured by AFM. PA6 was cooled at rates from 10 to 2000 K/s before isothermal crystallization to mimic a full range of processing relevant conditions. A time–temperature–transformation diagram was built based on kinetic data to illustrate that the isothermal crystallization of PA6 is sensitive to the crystallization pathway. The novel platform built on a modified FSC chip is a powerful tool for the comprehensive study of polymer crystallization at processing-relevant conditions.