# Fabrication of Low-Twist and High-Strength Metallic Fibre Hybrid Spun Yarns
## 1 Introduction  
Stainless-steel fibre hybrid spun yarns are becoming increasingly popular due to their wide range of applications. In this aspect, the cost-effective and scalable processing of such yarns is highly important. The processing of metallic fibre yarns has widely been reported because of their numerous applications in technical, industrial, multifunctional, health care, fashion and artistic textiles [1, 2, 3, 4]. Among numerous types of such yarns, the metallic fibre hybrid spun yarns are preferred because of their novel combination of mechanical, comfort and functional properties, especially desired in wearable applications [5, 6, 7, 8, 9]. The spun hybrid yarns, carrying metallic fibres are gaining a lot of interest owing to their myriad potential applications such as, electrostatic discharge protection, electromagneticinterference shielding, flexible strain sensors and actuators, wearable electronics, as well as technical, functional, and smart textiles [10; 11; 12; 13; 14; 15]. Among various types of metallic fibres, the use of copper wire, stainless-steel wire, and stainless-steel staples fibres (SSSF) have been widely reported in the literature [16; 17]. However, in contrast to copper wire and stainless-steel wire, the staple fibre hybrid yarns constituting SSSF are more flexible, soft, and easy to integrate into fabric by well-established fabric manufacturing techniques such as weaving and knitting [18; 19; 20]. There are numerous ways of incorporating metallic fibres into conventional textile fibres to produce metallic fibre hybrid spun yarns [21; 22]. The manufacturing of SSSF hybrid spun yarn is mostly carried out either by advanced friction spinning technique or conventional ring spinning process. The use of friction spinning machines (DREF II and III) was reported to produce the core-sheath yarns of stainless-steel wire, polyester fibres and SSSF for the construction of electromagnetic and electrostatic protective textiles, but without narrating the tensile properties of yarn produced [23; 24]. The use of conventional ring spinning for the processing of SSSF hybrid spun yarns have been reported by some researchers. [PERSON] used polyester and stainless-steel fibres blended ring-spun yarns to study the electromagnetic shielding properties of knitted fabrics [25]. Similarly, other researchers have revealed the development of hybrid ring-spun yarn composed of polypropylene and SSSF to analyse the physical, mechanical and electrical properties of these yarns [26; 27]. [PERSON] et.al, reported the use of the conventional ring spinning technique for the production and electro-mechanical characterization of SSSF hybrid spun yarns [3; 18]. From the state-of-the-art review, it can be concluded that the scholars have discussed mostly the properties and applications of metallic fibre yarns and less work has been carried out on the method of their fabrication, especially low twist and high strength, thus an energy-efficient and cost-effective way of processing. In the processing of staple spinning, with the right choice of spinning technique and optimised process parameters, better yarn quality at a higher production rate can be achieved economically. Strategies favouring the relatively lower production speeds, less wastage of materials and lower ends down rates, can bring down the cost of maintenance as well as electrical energy consumption. Consequently, an economical and sustainable method of yarn production can be approached. The twist of yarn is the most crucial processing parameter, governing the production rate, quality of yarn and cost of production. Keeping in view, this work is primarily focussed on investigating the process parameters of various spinning methods to explore the low twist, high strength and bulk production of stainless-steel fibre hybrid spun yarns in a cost-effective and sustainable approach.