关键词: 涤纶工业丝, 力学性能, 结晶, 取向, 成型工艺

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