Evaluation of Launderability of Electrically Conductive Fabrics for E-Textile Applications

This article presents the studies on the launderability of conductive fabrics with four types of metal coatings (Cu, Ag, Ni/Cu, or Ni/Cu/Co), respectively, which are laminated to three common fabrics (spandex, nylon, and denim) using thermoplastic urethane (TPU) film. The electrical resistance as a function of laundry cycles is used to characterize the performance of these conductive materials. The laundry procedure follows the AATCC M6 test standard by using the AATCC compliant washer and dryer with control factors such as detergent, temperature, agitation speed, and spin speed. After the intended wash and dry cycles, the electrical resistance of the conductive fabrics is measured using a four-point probe method. The resistance stability over the laundry cycles is compared between these conductive fabrics with four metal coatings, respectively. In general, all the conductive fabrics show an increase in electrical resistance with laundry cycles, and the extent of the increase depends on the metal coating and the base fabrics to which the conductive fabrics are laminated. Further, the soaking test reveals that the AATCC certified detergent does not have a measurable effect on the performance of the conductive fabrics. To obtain an insight on the degradation of the conductive fabrics during laundry, further inspection and analysis are performed, including 3-D optical microscopy, scanning electronic microscopy (SEM), cross sectioning, and X-ray fluorescence (XRF). A significant peeling and fracture of metal coating layers, due to mechanical tumble or agitation stresses during laundry, are observed for the conductive fabrics with Cu, Ni/Cu, and Ni/Cu/Co coatings, leading to electrical resistance increase or even electrical open, whereas the conductive fabrics with Ag coating show a metal scratch instead of peeling and fracture, possibly due to silver's superior flexibility, ductility, and adhesion with the base fiber. Besides metal coatings, the mechanical properties of the base fabrics appear to significantly affect the laundry performance of the conductive fabrics, in which the more rigid base fabric causes higher mechanical stresses on the metal coating, leading to more damages and accordingly higher increases in resistances.