关键词: 羊绒包芯纱, 扭矩平衡模型, 芯纱反向加捻, 纱线性能, 歪斜角度

Abstract:

Objective Due to the fine diameter and short length of cashmere fibers， cashmere yarns tend to exhibit high residual twist and a high number of snarls during production. This paper proposes a core-spun yarn structure with opposite twist directions in the inner and outer layers， which allows the twists in the core and outer layers to cancel the torque in each other during the yarn-forming stage， thereby reducing residual twist and snarls.

Method This paper presents a model for torque-balanced core-spun yarn. Using cashmere yarn as the outer layer and nylon yarn as the core， low-twist cashmere core-spun yarn with torque-balancing properties was produced through a design utilizing the combination of counter-twist directions between the core and outer layers （S-twist core and Z-twist outer layer）.

Results The employment of opposite twist direction in the core and cover layer of a core-spun yarn were found to reduce the residual twist of cashmere yarn. As the twist of the core yarn increased， the residual twist of the core-spun yarn showed a gradual downward trend. When the nylon core yarn was twisted to 900 twists per metre （S-twist） and the outer cashmere cover was twisted of 300 twists per metre （Z-twist）， the twist between the cover and core reached equilibrium， indicating that this core-spun yarn structure can effectively control the residual twist of the yarn. When the equilibrium twist was ≤19 twists/（25 cm）， the breaking strength was 142.70 cN， the evenness coefficient of variation （CV） was 7.84%， and the number of 3 mm neps was 43 per 10 meters. Compared with conventional core-spun yarn， this torque-balance yarn reduced the loop skew angle of knitted fabrics by 4.2°. In the constructed torque-balanced model， the torque values generated by the core yarn at different twist levels， the torque values of the cashmere sheath yarn， and the torque values of the core-spun yarn were calculated and compared with the experimental results. The findings indicated that the snarl count of the yarn is consistent with the residual torque of the core-spun yarn， that is， a lower residual torque corresponds to a fewer number of snarls.

Conclusion This research results show that the residual torque calculated by the torque-balanced model is in good agreement with the actual snarl formation of the yarn. When the residual torque between the core and sheath layers approaches equilibrium， the cohesion between the filament and cashmere fibers is enhanced， and the number of snarls and objectionable hairiness is correspondingly reduced. By controlling the twist direction and twist ratio （1∶1.9 - 1∶2）， the torque-balanced core-spun yarn structure achieves internal cancellation of residual torque to a certain extent， which helps reduce fabric curling， skewness， and cutting distortion， thereby improving the dimensional stability of garments. This study provides a reference for the torque-balanced design of cashmere core-spun yarn during the yarn-forming stage. Future work may further optimize the twist ratio and extend this approach to a broader range of fiber systems， exploring its large-scale application in high-performance knitted fabrics and low-carbon spinning systems to support the development of cashmere products toward improved dimensional stability.

Key words: cashmere core-spun yarn, torque balance model, reverse twisting of core yarn, yarn property, skew angle