Research on a novel sheath core-wrap staple yarn based on the ring spinning frame with special-shaped roller

This work explored a novel method for producing sheath core-wrap staple yarn on a modified ring spinning machine. The sheath core-wrap staple yarn is a new composite yarn whose core layer and sheath layer are both composed of staple fibers. In this paper, the conventional front roller on the ring spinning machine was replaced by a special-shaped roller, named a coaxial front roller of different diameters. In the spinning process, two colored cotton rovings were fed into the back roller. Then they are conveyed to the coaxial front roller of different diameters and output at different speeds. Finally, they were spun in a sheath core-wrap staple yarn under the twist effect. The covering effect and properties of sheath core-wrap staple yarn are the critical concerns in this article. Mathematical equations have been derived to calculate the ideal twist multiplier. It is most favorable for the core fiber to be covered at the ideal twist multiplier 408. The effects of the twist multiplier and core proportion on core exposure ratio and yarn properties (tensile properties, abrasion resistance, evenness, and hairiness) were investigated. The results showed that the core exposure ratio of all sheath core-wrap staple yarns were less than 2%, and the minimum core exposure ratio was obtained at the twist multiplier 400. The results also demonstrated that the tensile property, abrasion resistance, evenness, and hairiness improved with the increase of the twist multiplier and the core proportion. The proposed method provides new insight for researchers to fully understand the production process of sheath core-warp staple yarn and improve the yarn quality.