Abstract:

Objective The advent of intelligent wearable products has given rise to novel demands for conductive yarns, wherein high flexibility and remarkable adaptability to the human body are indispensable attributes. Flexible textile circuit made of metal wire ensures reliable electrical conduction but faces challenges in terms of wearing comfort and processability. The aim of this research is to prepare an innovative conductive nanofiber core-spun yarn with superior textile properties, and to investigate the influence of core yarn types on the performance of conductive nanofiber core-spun yarns.

Method A homemade electrostatic spinning device was established for continuous preparation of nanofiber core-spun yarns. During the preparing process, three conventional yarns including polyester yarn, aramid yarn, and polyester-cotton blended yarn were selected as the core yarn, and polyacrylonitrile (PAN) nanofibers were enwrapped on the core yarn through electrospinning. As such, the nanofiber core-spun yarn possessed both high specific surface area of nanofibers and robust mechanical properties of conventional yarn. The conductive nanofiber core-spun yarn with surface supported polypyrrole (PPy) was successfully prepared by further in-situ polymerization of pyrrole. The morphologies, mechanical properties and electrical properties of PPy/PAN nanofiber core-spun yarns were analyzed and characterized. Finally, the PPy/PAN nanofiber core-spun yarns was wrapped on polyurethane yarns and then subjected to 2 000 cycles of stretch deformation at 10% strain to further study the long-term stability under repetitive strain cycles.

Results The morphology of the core yarn was found to have a significant influence on the morphology of the conductive nanofiber core-spun yarn. A lower level of hairiness and stiffness of the core yarn resulted in a superior fit with the nanofibers. In comparison with that of aramid and polyester-cotton blended yarn, nanofibers enwrapped most suitable on polyester core yarn. Especially, the arrangement and orientation of the nanofibers were more superior with polyester as the core yarn. The increased hairiness of the core yarn, however, brought about a notable enhancement in the weight-gain rate of the conductive nanofiber core-spun yarn. Compared with that of conductive PPy/PAN nanofiber/polyester core-spun yarn having 39.29% weight-gain rate, the weight-gain rates of the conductive PPy/PAN nanofiber/aramid core-spun yarn and the conductive PPy/PAN nanofiber/polyester-cotton core-spun yarn were 53.49% and 52.63% respectively. The yarn with polyester core exhibited obvious uniformity and aesthetic appeal after enwrapped with PAN nanofibers, which could be attributed to the significant decrease of the hairiness. The mechanical properties of the core yarn had a decisive effect on the mechanical properties of the conductive nanofiber core-spun yarn, while enwrapping nanofibers loaded with PPy could further enhanced the yarn's breaking strength and elongation at break. Compared with that of the core yarn covered with PPy directly, the electrical properties of the conductive PPy/PAN nanofiber core-spun yarns were significantly improved. The conductivity of the PPy/PAN nanofiber/polyester-cotton core-spun yarn reached 293.39 mS/cm, which was 9.4 times higher than that of polyester yarn covered with PPy directly. The PPy/PAN nanofiber core-spun yarn was further wrapped around the polyurethane yarn and subjected to 2 000 cycles of stretch deformation at 10% strain. Its electrical signal response demonstrated stability, suggesting good consistent electro-mechanical properties and durability over multiple cycles.

Conclusion The morphologies, mechanical properties and electrical properties of PPy/PAN nanofiber core-spun yarns are closely related to the core yarn type. In order to obtain high-strength yarns, it is recommended to selecting aramid yarn as the core material. Polyester yarn may be selected for the purpose of enhancing the elongation at break. Polyester-cotten blended yarn can be employed as the core yarn to improve the conductivity of PPy/PAN nanofiber core-spun yarn. The present work can be adopted to further develop conductive PPy/PAN nanofiber core-spun yarns into different core yarn types, which can be widely used in various fields such as sensors, signal transmission, and interactive textiles. This kind of conductive yarns also has a promising future in the application of flexible and wearable smart devices.

Key words: conductive yarn, core yarn type, polyacrylonitrile, nanofiber, core-spun yarn, polypyrrole, electrospinning