Nanocomposite coatings on cotton and silk fibers for enhanced electrical conductivity

Abstract

Electrically conducting carbon nanofillers like liquid exfoliated graphite (EG), nanographite (NG), carbon nanotube (CNT) and carbon nanofiber (CNF) were dispersed in thermoplastic polyurethane (TPU) matrix. HRTEM images and SAED patterns confirmed exfoliation of graphite and good dispersion of all nanofillers. The polymer dispersions were used to develop nanocomposite coatings on cotton yarn and silk fibers. These nanocomposite coated fibers showed significant improvements in electrical conductivity. Current-voltage (IV) plots indicated linearity for most of the nanocomposite coated fibers. Among the nanofillers, CNF and CNT have strong potential to impart stable conductivity on such fibers. The electrical conductivity of 10 wt% CNF based nanocomposite coated cotton yarn was 2 S/m; while it was more than 12 S/m for silk filament. 2 wt% CNT dispersed nanocomposite coating on silk also showed very good conductivity of 11 S/m. The large void fraction in coated cotton yarn (~12 %) is attributed for such difference in electrical conductivity. Hence, staple yarns are not suitable to develop such nanocomposite coated fibers. Both the resistance and impedance tests were carried out at different test lengths up to 5 cm and resistance and impedance (at 100 Hz, 120 Hz and 1 kHz) per cm was calculated with variable test length. As variations in test results were not very high it can be concluded that the uniformity in electrical conductivity is achieved through these coatings.