Abstract: Polyester industrial yarns have excellent mechanical properties, good aging resistance and chemical resistance, etc. They are widely used in hoses, sewing thread, cables, tire cord, geogrid, advertising light box cloth and conveyor belts. With the progress of science and technology and the continuous development of society, the use of industrial polyester fibers with the largest demand is increasing, the field of application continues to expand, and at the same time the production level of Chinese industrial polyester fibers is also constantly improving.
The key to producing high-quality, differentiated polyester fibers for industrial use with different properties lies in mastering the relationship between processing - structure - properties of polyester industrial yarns. The post-processing of polyester industrial yarns directly affects the structure of the molecules in the aggregation state, such as crystallization and orientation, and thus determines the mechanical properties of the fiber. Most of the studies on the structure and properties of polyester industrial yarns are based on laboratory platforms with low deformation rates and long heat treatments, which are significantly different from the high-speed spinning and rapid molding of polyester industrial yarns in actual production processing. There are insufficient studies on the evolution of the structure and properties of the aggregation state during the multistage drawing and heat-setting stages of the post-processing of industrial filaments in production.
In order to analyze the evolution of the aggregation state structure and properties of fibers during the multi-stage drawing and heat-setting process on the production of high-strength polyester industrial yarns, fiber samples were collected in segments, the aggregation state structure of fibers at different molding stages in terms of thermology, crystalline, orientation, lamellar crystal, and long-periodic structure was systematically investigated by using the analytical methods, such as DSC, DMA, WAXD, and SAXS, and the correlation between variations of the mechanical properties of the fibers with the fiber structure was analyzed. The results show that the first-stage hot drawing promotes the crystallization of molecular chain orientation in the amorphous zone, which improves the breaking strength of the fiber and reduces the thermal shrinkage; the second-stage hot drawing further improves the degree of orientation of the amorphous molecular chain, which leads to the reorganization of the grains and the formation of the rigid amorphous fraction (RAF), the degree of crystallinity increases significantly, the breaking strength of the fiber is significantly improved and the shrinkage is significantly reduced. In the subsequent two-stage relaxation heat-setting stage, the amorphous molecular chains are more active and easy to be built into the lattice, which further leads to the increase of crystallinity and RAF, and at the same time, localized disorientation occurs, resulting in the fiber fracture strength and shrinkage decreasing with the increase of the degree of amorphous molecular chain disorientation. This study analyzed the crystalline structure and orientation of the fibers, illustrated the evolution of the aggregation state structure and mechanical properties of polyester industrial yarns during post-spinning processes, and provided a reference for the property regulation of industrial polyester industrial yarns and the development of new products.
Based on the analysis of fiber crystalline structure and orientation, this paper illustrates in detail the evolution of polyester industrial yarns’ aggregation state structure and mechanical properties with the post-spinning processing, which provides theoretical references for the production of differentiated polyester industrial yarns.

Key words: polyester industrial yarns, mechanical properties, crystallization, orientation, molding process

摘要： 为解析高强涤纶工业丝生产上多级牵伸和热定型过程中纤维的聚集态结构与性能演变，分段采集纤维样品，利用DSC、DMA、WAXD和SAXS等分析方法，系统研究纤维在不同成型阶段的热学、结晶、取向、片晶和长周期结构等聚集态结构，并将纤维力学性能的变化与纤维结构进行关联分析。结果表明：一级热牵伸促进了非晶区分子链取向结晶，使得纤维的断裂强度提升而热收缩率降低；二级热牵伸进一步提升了非晶分子链取向度，促使晶粒重组并形成刚性非晶部分（Rigid amorphous fraction, RAF），结晶度明显升高，纤维的断裂强度显著提升而收缩率显著降低；在随后的两级松弛热定型阶段，非晶区分子链活动能力较强，易于砌入晶格，进一步促使结晶度提高、RAF的增大，同时局部发生解取向，导致纤维断裂强度和收缩率随非晶区分子链解取向程度的增加不断减小。该研究分析了纤维的结晶结构和取向，阐明了涤纶工业丝聚集态结构与力学性能在纺丝后加工过程中的演变规律，可为产业用涤纶工业丝的性能调控和新产品的开发提供参考。

关键词: 涤纶工业丝, 力学性能, 结晶, 取向, 成型工艺