Investigating the electromagnetic wave-absorbing, water repellency, and flame-retardant effectiveness of nickel–iron/PPTA-blended knitted fabrics

In recent decades, electromagnetic wave pollution has become more and more serious. In order to reduce the adverse effects of these waves, the nickel–iron/polymers of p-phenylene terephthamide (PPTA)–blended single yarn and plied yarn were manufactured, and the nickel–iron fibers with various contents (10%, 15%, and 20%) as raw materials were used. Nickel–iron/PPTA-blended yarns were knitted with three knit structures and three looped deep (11.25, 11.50, and 12.00 mm). The electromagnetic absorption effect was examined using the reflectance arch method at a frequency range between 2 and 18 GHz. The results show that the fabric with plied yarn, nickel–iron fiber content of 10%, looped deep of 12.00 mm, and loop notation of structure C has the best electromagnetic wave absorption performance, which can reach −30 dB reflectivity at 5.1 GHz, and the bandwidth with reflectivity lower than −5 dB reaches 2.5 GHz. In order to make the fabric obtain more functions, water-repellent treatment of the fabric is carried out. The results show that the best finishing effect can be obtained by using 40% water repellent and drying at 170°C for 5 min so that the sample can resist the hydrostatic pressure of 49.1 kPa. Finally, through the vertical burning test, the flame retardancy of the fabric can reach level B1.