Abstract:

Objective There are some performance defects in wool yarn itself, such as low breaking strength and excessive yarn hairiness, which affect its processability and fabric wearability, for example, low strength makes it unable to withstand larger weaving tension, and excessive hairiness leads to yarn entanglement during weaving and fabric pilling. This article explores the feasibility of using filament yarn to wrap wool yarn by hollow spindle covering to improve its processability and fabric wearability, as well as the impact of the main wrapping process on the technical effect, aiming at providing reference for the development of covered wool yarn and its fabric products.
Method Four twist levels of single-covered and cross-wrapped double-covered composite yarns were applied to the yarns using the hollow spindle covering machine, where 26.3 tex black wool worsted yarn was used as the core yarn, and 44.4 dtex(34 f) polyamide white Fully-Drawn-Yarn(FDY)filament yarn was used as the outer wrapping yarn. The structure of the two types of composite yarns were observed by magnification, the tensile properties, hairiness, evenness and yarn defects were tested according to corresponding standards and comparatively analyzed, and the application of wool yarn covering processing was discussed.
Results The spinning principle of single-covered and double-covered yarn were shown (Fig. 1), and the structure models of the two types of covered yarn were given correspondingly (Fig. 2), as well as the partial enlarged views of the two types of composite yarns(Fig. 3), so as to observe and compare their composite structures. The package appearance (Fig. 4) and the photos of the yarn card (Fig. 5) of the two types of composite yarns were presented respectively to show the appearance characteristics. A partial enlarged picture of 750 twists/m single covered yarn was provided (Fig. 6) for presenting the obvious twist irregularity of single covered composite yarn. In order to compare and analyze the influence of covering processing and its parameters on the tensile performance of the wool yarns, the total tensile fracture curves of 50 times of polyamide wrapped yarn(Fig. 7(a)), wool core yarn (Fig. 7(b)), four twist levels were applied to the single-wrapped composite yarn (Fig. 8) and the typical double-wrapped composite yarn (Fig. 9), and the tensile strength of all raw yarns, single-covered yarns and double-covered yarns were listed (Tab. 1), including breaking strengths/tenacities and their CV value, break elongations and their CV value, and the failure of the core and cover yarns. The hairiness test results of the wool yarn and two type of composite yarn were exhibited (Tab. 2), and the test results for evenness and yarn defects were provided (Tab. 3). The performance changes of composite yarn compared with the wool yarn and the influence of different twist configurations were compared and analyzed, and based on this, the industrial application and requirements of wool yarn covering processing were discussed.
Conclusion The composite yarn has a mixed color appearance of the color of core yarn and outer wrapping yarn. The single-covered composite yarn has the characteristics of uneven distribution of twist, the twist on the thick place is smaller, and the twist on the thin place is larger. The breaking strength of the composite yarn is greater than that of the wool yarn, and the double-covered yarn is greater than the single-covered yarn. The elongation at break of the composite yarn is significantly higher than that of the wool yarn, and the double-covered yarn is greater than that of the single-covered yarn. The covering composite yarns can significantly reduce the hairiness of wool yarn and improve wool yarn evenness and reduce yarn defects. Taking wool yarn as the core yarn, reasonably selecting the type and specification of wrapping yarn and the covering process can improve the processability of wool yarn and change the style and performance of fabric products.

Key words: wool yarn, covered yarn, covering process, single-covered, double-covered, composite structure, yarn property, polyamide filament