Abstract:

Objective The application of conductive yarns in flexible and wearable smart devices has attracted extensive attention from many researchers. The key objectives of this research included preparing elastic and conductive yarns with excellent textile properties such as color attributes, wearing comfort, and environmental friendliness.
Method In order to prepare a conductive yarn with favorable textile properties, cotton roving, silver wire and spandex were selected as the raw materials. By designing the feeding of raw materials and attaching a positioning device between the front roller and the yarn guide in the ring spinning machine, an elastic conductive core yarn with spandex as the core, silver yarn and cotton fibers as the sheath with cotton fibers on the surface of the yarn was produced to investigate the influence of yarn twist on the elasticity, conductivity, abrasion resistance and breaking strength of the core spun yarn. Using the model of silver wire tightly wrapped around the spandex surface (Fig.2), the theoretical value of the length of silver wire wrapped around the spandex surface in the core spun yarn with different yarn twist was calculated.
Results The experimental results showed that the elasticity of core spun yarn varied with yarn twist, and the elasticity of core spun yarn at constant elongation and at constant load was larger at a yarn twist of 70 twist/(10 cm) than yarns with other yarn twists (Fig.4). In the unstretched straight state of the core spun yarn, the measured resistance of the yarn increased with the increase of yarn twist (Tab. 2), because increasing the yarn twist causes the pitch of the wrapping silver wire to decrease and the length of the silver wire in the unit length of core spun yarn to increase. At 10% elongation of the core spun yarn, the measured resistance of the yarn was smaller than that of the same length of core spun yarn in the unstretched state, and the difference between the measured resistance of the same length of core yarn in the elongated state and in the unstretched state was smaller at a twist of 75 twist/(10 cm) (Tab. 3). At 10% elongation of the core spun yarn, the measured resistance of the core yarn per unit length was greater than the theoretical resistance of the straight silver wire, indicating that when the core spun yarn elongation is at 10%, the silver wire in the yarn was not at the completely straightened state, and the yarn elongation caused the pitch of the silver wire over the spandex became larger and the actual length of the silver wire in the core spun yarn per unit length became smaller. At 75 twist/(10 cm), the core spun yarn showed higher wear resistance. Because when the twist is too high, the torque of cotton fibers in the yarn is high, the fiber stress increases, causing the cotton fibers to be easily worn off and the wear resistance of the core spun yarn is reduced.
Conclusion The elasticity and conductivity of core spun yarn are closely related to the yarn twist level. For the actual core spun yarns, the silver wire is not tightly wrapped around the surface of the spandex core, and there are cotton fibers between the spandex and the silver wire, causing the theoretical resistance value per unit length to be smaller than the measured resistance value. Since cotton fibers can be dyed in different colors and the cotton fibers are distributed on the surface of the core spun yarn, this work can be used to further develop elastic and conductive yarns in different colors and comfortable to wear for the transmission of electrical signals in smart wearable textiles, powering electronic textiles, and electrical heating devices. The preparation process of this core spun yarn is environmental friendly. In the application of flexible and wearable smart devices, such elastic and conductive core spun yarsn have a good development prospect.

Key words: core spun yarn, conductive yarn, silver wire, spandex, yarn twist, electrical conductivity