Abstract:

Objective This research investigates the combination patterns and corresponding composite multi-yarns that can be produced using hollow spindle wrapping technology. It explores the techniques for achieving diverse combination patterns, as well as the influence of these composite structures on the appearance, tensile properties, and structural stability of the resulting composite yarn.

Method Beginning with the mechanism exploration of the hollow spindle system for preparing wrapping composites, the study analyzes feeding requirements and methods. It also examines the twist direction when utilizing multiple sets of hollow spindles, aiming to diversify the composite structures through varied feeding methods and twist direction adjustments. By taking four yarns as an example, the research analyzes the combination patterns and structures produced under various configurations of hollow spindle numbers, yarn feeding methods, and wrapping twist directions. Four different colored polyester textured yarns served as raw materials to create covered yarns with distinct composite structures, which were subsequently tested and compared concerning their appearance, tensile properties, and structural stability.

Results The analysis of the feeding and output characteristics of the hollow spindle system revealed performance requirements for both the core and outer wrapping of a cover yarn, and two basic rules regarding yarn feeding were derived: 1) the feeding of the core yarn was not limited to a single strand; 2) additional core yarn could be introduced after the first set of hollow spindles. The study presented methods for expressing combination patterns and structures based on varying wrapping times, feeding methods, and twist directions. Four combination patterns and nine distinct composite structures were identified, including ″three-core single-wrapping″, ″two-core twice-wrapping″, ″additional-core twice-wrapping″, and ″single-core triple-wrapping″. These structures were produced by employing different yarn feeding techniques and configurations of wrapping twist direction when utilizing one, two, or three sets of hollow spindles. Additionally, methodologies for feeding additional core yarns and guiding the yarn for achieving triple wraps were provided using existing hollow spindle covering machines, enabling the production of nine specified composite yarn structures. A comparative analysis of appearance and color mixing characteristics, along with covering effects, was conducted based on photographs of the yarn bobbins and the nine composite yarns. The tensile performance results and snarl indexes of both the four types of raw yarns and the nine kinds of composite yarns were presented and analyzed.

Conclusion The hollow spindle covering technology allows for wrapping multiple yarns in a single processing. By varying the number of hollow spindles, yarn feeding methods, and twist direction configurations, a range of composite methods and structures have been achieved, resulting in composite yarns with distinct appearances (covering effects) and properties. The first set of hollow spindles can accommodate one or multiple core yarns, while the subsequent spindles may also introduce ″additional core yarns″, thus facilitating greater structural diversity. Owing to the differences in composite structures, significant variations exist in the appearance, tensile performance, and structural stability of the composite yarns. Feeding more than one core yarn and additional core yarn can produce a segmented color effect, although wrapped twice may diminish this characteristic. Additionally, the strength utilization rate of composite yarns with the ″single-core triple-wrapping″ is lower than that of other structural configurations, while those with the last two wraps twisting in opposing directions demonstrate stable structures and low snarl indexes. By carefully selecting combination patterns and optimizing wrapping twists, it is possible to achieve composite structures and performance that meet diverse requirements.

Key words: covered yarn, combination pattern, combination structure, quadratically-fed, tensile property, structural stability