关键词: 含不锈钢丝弹力包覆纱, 氨纶预牵伸倍数, 模糊综合评判, 可拉伸电磁屏蔽织物, 屏蔽效能

Abstract: Recently, the demand of protective and comfortable performances of personal protective equipment is gradually increasing. For electromagnetic shielding fabrics, most of the existing surface-coated electromagnetic shielding protective materials have certain disadvantages such as inelasticity, poor shape retention, poor washing resistance, and uncomfortable characteristics. The development of a new material having the characteristics of mechanically stretchability, controllable structure, flexible manufacturing, and electromagnetic shielding durability has become the first choice for the next generation of textile-based electromagnetic shielding materials. To fabricate high-performance yarns with excellent elasticity and shielding capability is a necessary prerequisite for the preparation of intrinsically stretchable electromagnetic shielding textile fabrics. Given this, the intrinsically stretchable electromagnetic shielding fabrics were constructed from the double level of “elastic yarn-elastic fabric” in this study. Specifically, elastic wrapped yarns containing metal wire were fabricated based on a hollow-spindle wrap spinning system with elastane filament (EF) as the core, stainless steel wire as the first wrapping layer and cotton ply yarn as the second wrapping layer. The effect of the pre-draft ratio of EF on the tensile and elastic behaviors of wrapped yarns was systematically investigated, and the processing parameter were optimized by using the fuzzy comprehensive evaluation method. After that, a weft stretch woven fabric having the characteristics of high stretchability and robust electromagnetic shielding effectiveness was produced, and the key factors influencing the shielding efficiency were systematically clarified.
In this work, the flexibility of relatively rigid stainless steel wire can be realized by using two sets of hollow spindle device in series, the design of yarn structure and the configuration of the components within a wrapped yarn are responsible for the above results. The as-fabricated wrapped yarns are well wrapped by cotton ply yarn, and no stainless steel wire and EF components can be visibly seen. Further, taking the pre-draft ratio of EF 2.5 as an example, the resultant wrapped yarn has a more bulking surface profile compared with the straighten one, which facilitates its elastic elongation rate to 240.5% without distortion. Importantly, the macroscopically observable stretchability is closely related to the pre-draft ratio of EF, and the electrical conductivity of the wrapped yarns can keep maintained during the stretching process. The experimental results demonstrate that the pre-draft ratio of EF has significant influence on the related properties of the resultant wrapped yarns. With the increase of the pre-draft ratio of EF, the breaking strength of yarns gradually increases while the extension at break decreases. From the tensile curves of the resultant wrapped yarns with varying pre-draft ratios of EF we can see that, the fracture mode has converted from multiple breaks to single break with an increase of the pre-draft ratio. Also, the superior elastic properties of wrapped yarns can be obtained when the pre-draft ratio of EF is between 2.5 and 3.0. In addition, the optimized process parameter for fabricating such wrapped yarns can be obtained via fuzzy comprehensive evaluation method, that is, the pre-draft ratio of EF 2.5 within the predetermined scope in this work. Finally, a weft stretch woven fabric was manufactured with cotton ply yarn and wrapped yarn with optimized process parameter as warp and weft respectively. It is found that the effective electromagnetic shielding can be realized when the direction of stainless steel wire within the fabric is consistent with the direction of electric field vibration, and vice versa. The electromagnetic shielding capability of fabric gradually increases with an increase of tensile strain of fabric in weft direction.
The relevant research of this paper will not only provide technical support and realize the optimization of key process parameter for the fabrication of multifunctional wrapped yarns, but also provide certain theoretical basis and practical guidance for the scientific design of fabric-based electromagnetic shielding materials.

Key words: elastic wrapped yarn containing metal wire, spandex stretch, fuzzy comprehensive evaluation, elastic electromagnetic shielding textile fabric, shielding effectiveness