Gan Diansong, Liu Yuejun, Hu Tianhui, Fan Shuhong, Cui Lingna, Liao Guangkai, Xie Zhenyan, Zhu Xiaoyu, Yang Kejian
Key Laboratory of Advanced Packaging Materials and Technology of Hunan Province, School of Packaging and Materials Engineering, Hunan University of Technology, Zhuzhou 412007, China.
Zhuzhou Times Engineering Plastics Industrial Co., Ltd., Zhuzhou 412008, China.
Polymers (Basel). 2024 Apr 22;16(8):1176. doi: 10.3390/polym16081176.
The biaxially-oriented PA56/512 has excellent mechanical strength, extensibility and water-oxygen barrier properties and has broad application prospects in green packaging, lithium battery diaphragm and medical equipment materials. The correlation between the aggregation structure evolution and macroscopic comprehensive properties of copolymer PA56/512 under biaxial stretching has been demonstrated in this work. The structure of the random copolymerization sequence was characterized by C Nuclear magnetic resonance (NMR). The typical isodimorphism behavior of the co-crystallization system of PA56/512 and its BOPA-56/512 films was revealed by differential scanning calorimetry (DSC) and X-ray diffraction (XRD) tests. And the aggregation structure, including the hydrogen bond arrangement, crystal structure and crystal morphology of PA56/512 before and after biaxial stretching, was investigated by XRD, Fourier-transform infrared spectroscopy (FTIR) and polarized optical microscopy (POM) tests. Furthermore, the effect of the biaxially-oriented stretching process on the mechanical properties of PA56/512 has been demonstrated. In addition, a deep insight into the influence of the structure on the crystallization process and physical-mechanical performance has been presented. The lowest melting point at a 512 content of 60 mol% is regarded as a "eutectic" point of the isodimorphism system. Due to the high disorder of the structural units in the polymer chain, the transition degree of the folded chain (gauche conformation) is relatively lowest when it is straightened to form an extended chain (trans conformation) during biaxially-oriented stretching, and part of the folded chain can be retained. This explains why biaxially stretched PA56/512 has high strength, outstanding toughness and excellent barrier properties at the pseudo-eutectic point. In this study, using the unique multi-scale aggregation structure characteristics of a heterohomodymite polyamide at the pseudo-eutectic point, combined with the new material design scheme and the idea of biaxial-stretching processing, a new idea for customized design of high-performance multifunctional polyamide synthetic materials is provided.
双向拉伸的PA56/512具有优异的机械强度、拉伸性和水氧阻隔性能，在绿色包装、锂电池隔膜和医疗设备材料等方面具有广阔的应用前景。本工作揭示了共聚物PA56/512在双向拉伸下聚集结构演变与宏观综合性能之间的相关性。通过碳核磁共振（NMR）对无规共聚序列结构进行了表征。通过差示扫描量热法（DSC）和X射线衍射（XRD）测试揭示了PA56/512及其双向拉伸聚酰胺56薄膜（BOPA-56/512）共结晶体系典型的等双变性行为。通过XRD、傅里叶变换红外光谱（FTIR）和偏光显微镜（POM）测试研究了PA56/512双向拉伸前后的聚集结构（包括氢键排列方式、晶体结构和晶体形态）。此外，还揭示了双向拉伸过程对PA56/512力学性能的影响。另外，深入探讨了结构对结晶过程和物理力学性能的影响。512含量为60 mol%时的最低熔点被视为等双变性体系的“共晶”点。由于聚合物链中结构单元的高无序性，在双向拉伸过程中，折叠链（gauche构象）伸直形成伸展链（trans构象）时，其转变程度相对最低，部分折叠链得以保留。这解释了为什么双向拉伸的PA56/512在假共晶点具有高强度、出色的韧性和优异的阻隔性能。在本研究中，利用假共晶点处杂同异形聚酰胺独特的多尺度聚集结构特征，结合新材料设计方案和双向拉伸加工理念，为高性能多功能聚酰胺合成材料的定制设计提供了新思路。
