拉伸诱导氢键密度梯度化聚酰胺的结构演变及力学关联性研究

Due to the existence of a large number of hydrogen bonds between molecular chains in polyamides, the structure evolution induced by stretching is more diverse and complicated compared with that of polyolefin. During the molding process of polyamide fibers, the molecular mechanism of the formation, destruction and reconstruction of hydrogen bonds between molecular chains is not clear, and the deformation mechanism of polyamides and its influencing factors are not clear, which restrains the preparation of polyamide fibers with high performance. The polyamides are used as the research objects, such as polyamide 6, polyamide 612 and polyamide 1212. The structure evolution of polyamides is mainly investigated by in-situ X-ray and in-situ fourier transform infrared spectroscopy (FTIR) techniques during the stretching process. The polyamides with gradient density of hydrogen bonds are prepared, and the molecular mechanism of the formation, destruction and reconstruction of hydrogen bonds between molecular chains is analyzed in depth under temperature and strain fields. The effects of the density and arrangement of hydrogen bonds, stretching temperatures and stretching rates on the structure evolution of polyamides are explored, and the deformation mechanism and effects of influencing factors can be clear. Based on in-situ X-ray and scanning electron microscope (SEM) results, the correlation mechanism of structure evolution, aggregation structure and mechanical properties in polyamides is further established. According to these studies, the intrinsic mechanism of structure evolution of polyamides can be clear, and they can provide experimental basis and theoretical supports for preparation of polyamide fibers with high performance.

由于聚酰胺分子链间存在大量氢键，拉伸诱导其结构演变与传统聚烯烃相比更加多样化、复杂化。聚酰胺纤维材料成型过程中，分子链间氢键形成、破坏与重构的分子机制尚不清晰，材料形变机制及其影响因素尚不明确，这制约着高性能纤维材料的制备。本项目以聚酰胺6、612、1212为研究对象，主要采用原位X射线与原位红外光谱技术研究材料在拉伸过程中的结构演变。制备氢键密度呈梯度变化的聚酰胺材料，在温度场与应变场条件下，深入解析分子链间氢键的形成、破坏与重构的分子机制。研究氢键密度及排布、拉伸温度与拉伸速率对材料结构演变的影响，明确材料的形变机制及影响因素作用规律。基于原位X射线与扫描电镜测试结果，进一步构建聚酰胺材料结构演变与聚集态结构、力学性能之间的关联机制。通过这些研究，既可以清晰聚酰胺结构演变的内在机制，又能为高性能聚酰胺纤维材料制备提供实验依据与理论支撑。

在纺织领域，纤维材料的高性能设计一直是研究的热点与难点。聚酰胺材料被广泛应用于纺织服装领域。值得注意的是，短链聚酰胺（如聚酰胺6、66等）被应用地更为广泛。长链聚酰胺（如聚酰胺612、1212等）具有较短链聚酰胺更为优异的柔韧性、低的吸水率、良好的热加工性能。因此，拓展长链聚酰胺材料的应用领域显得尤其重要。众所周知，短链聚酰胺具有较长链聚酰胺更高的力学性能。这一点成为制约长链聚酰胺应用的关键问题。但是，对于纤维材料而言，材料的强度取决于加工成型工艺。因此，探索加工工艺对材料聚集态结构及其性能的影响规律至关重要。本项目以三种氢键密度呈梯度变化的聚酰胺材料作为研究对象。这三种聚酰胺材料分别是：聚酰胺6、聚酰胺612和聚酰胺1212。对比分析短链与长链聚酰胺在外场作用下的聚集态结构及宏观力学性能变化。N-乙基-对甲苯磺酰胺（N-PTSA）是聚酰胺材料的有效增韧剂，它的加入可以有效改变聚酰胺分子链间的氢键排布方式。采用同步辐射SAXS手段分析了聚酰胺1212在单轴拉伸过程中的结构演变，明确了材料的形变机制。重点探索牵伸温度、牵伸应变对材料宏观性能及微观结构的影响规律。建立材料在外场作用下的结构演变模型。通过上述研究，可以为高性能聚酰胺纤维材料设计提供理论与实验支撑。