Heating filament with Self-Regulation Temperature by Coating a Metallic Yarn with a Conductive Polymer Composite

Nowadays, the heating textiles are used in many fields of applications as medicine or comfort. The heating property for the most part of these textiles was ensured by electrical conductive fiber as metallic yarn thanks to Joule Effect. A challenge for heating textile is to have an electrical conductive fiber which has a temperature self-regulation at the comfort temperature. Thanks to this temperature self-regulation, the heating textile reaches more autonomy. To develop this kind of textile, conductive polymer composite (CPC), which is the combination between an insulating polymer and electrical conductivity nanofillers [1], is made by melt spinning. The temperature self-regulation is provided by the positive temperature coefficient (PTC) effect, which allows switching between an electrical conductivity state and an insulating state when the CPC is close to a transition phase temperature (glass transition temperature or melt temperature). However, when the PTC effect can take place at the melting point, the mechanical properties are not involved. So to maintain the final product an immiscible polymer blend was used: one polymer was the CPC and the second polymer was an insulating polymer with a higher melting point than the target temperature. In fact, the CPC involve the electrical conductivity and the PTC effect, whereas the insulating polymer involves the mechanical properties. However, a high electrical conductivity is necessary to reach the comfort temperature (defined around 42°) by Joule Effect. So to reach this temperature, the coating on a metallic yarn by the conductive immiscible polymer blend was used. The electrical conductivity of this product was improved by the metallic yarn and the self-regulating temperature by the PTC effect of the immiscible polymer blend (figure 1). In this paper the immiscible polymer blend used is a polycaprolactone (PCL) filled with multiwall carbon nanotubes (MWCNT) and a polypropylene (PP). In fact, in a previous paper the co-continuity and the selective localisation of the fillers in the PCL for this blend was studied [2]. The influence of the thickness CPC coating and the influence of the structure of metallic yarn were studied on the electrical conductivity, the Joule Effect and PTC effect.