Changes in Porosity, Electrical and Surface Properties after Laundering of Heat-treated AgNW/PDMS/PU Nanofiber-web

In this study, to investigate the effects of heat treatment and polydimethylsiloxane (PDMS) coating on durability to laundering, the changes in the porosity, electrical resistance, and surface property of the heat-treated silver nanowire (AgNW)/PDMS/polyurethane (PU) nanofiber-web before and after laundering were examined. To prepare the conductive specimens, PU nanofiber-web, 1 wt% of AgNW dispersion in ethanol, and two types of PDMS precursors were used. A total of four specimens were prepared: Specimen A (The AgNW/PU nanofiber-web), Specimen AH (The heat-treated AgNW/PU nanofiber-web), Specimen AP (The PDMS-coated AgNW/PU nanofiber-web), and Specimen AHP (The heat-treated AgNW/PDMS/PU nanofiber-web). The specimen was rinsed and dehydrated after laundering under the conditions according to ISO 6330. To investigate the changes of porosity after a single washing cycle, mean pore diameter and pore size distribution were measured. Linear electrical resistance and microscopic surface view of the specimen were evaluated. As a result, many micro-pores were distributed in Specimen AH because of the heat treatment. After laundering, Specimen AH still had the micro-pores, and thus, the heat treatment improved the durability to laundering. Also, the electrical resistance of Specimen AH was only changed slightly even after laundering, which was because the heat treatment strengthened the bonding between the nanofibers and the silver nanowires, thus the silver nanowires sufficiently remained on the specimen surface even after laundering. And, Specimen AH showed that the silver nanowires formed a network even after laundering and were evenly covered with silver nanowires onto the specimen surface. This result affected the aforementioned electrical performance, and in fact, the electrical resistance of Specimen AH was the lowest regardless of laundering. However, it was impossible to measure the porosity of Specimen AP and Specimen AHP due to the PDMS coating. Therefore, the heat treatment affected the durability to laundering as well as the electrical conductivity to increase, but PDMS coating blocked the micro-pores of the nanofiber-web and enabled higher initial resistance.