Electrical Heating Performance of Electro-Conductive Para-aramid Knit Manufactured by Dip-Coating in a Graphene/Waterborne Polyurethane Composite

Abstract

An electro-conductive para-aramid knit was manufactured by a dip-coating in a graphene/waterborne polyurethane(WPU) composite for confirming to use as a fabric heating element applicable to a protective clothing requiring durability. The para-aramid knit was dipped in 8 wt% graphene/WPU composite solution up to five-coat cycles. As a result of electro-conductive textile by number of dip-coating cycles, the electrical, and specifically electrical heating performances were increased number of cycles from one to five. The sample with the best electrical and electrical heating performance was the five-coat sample, and to improve those properties it was hot-pressed at 100 °C, 120 °C, 140 °C and 160 °C. After hot pressing, the entire surface of the sample was filled with graphene/WPU composite and indicated smoothly surface, thus the electrical and electrical heating performance was improved than the five-coat sample. The best performance of was indicated hot-pressed at 140 °C, with a surface resistivity and capacitance of 7.5 × 10⁴ Ω/sq and 89.4 pF, respectively. When a voltage of 50 V was applied, the surface temperature reached 54.8 °C. The five-coat sample with hot-pressed at 140 °C could be applied to a heat-resistant para-aramid knit glove with the touch screen of a mobile phone and electric heating performance.

Figure 1

(a) Digital images and (b) morphology of graphene/WPU dip-coated para-aramid knits, (c) Weight increase and surface resistivity of electro-conductive textile (insert image shows using the three, four, and five-coat samples to light up two LEDs) (d) Capacitance of dip-coated electro-conductive textiles, (e) Using the five-coat samples to touch a screen, (f) Electrical heating properties of the electro-conductive textile (insert image indicates IR thermal image of four and five coat samples when applied 50 V), (g) Electrical heating behavior of samples by number of coating cycles with applied 50V.

Figure 2

Scanning electron microscopy (SEM) micrograph of the surface of the five-coat knits with different hot-press temperatures (a) at 300x magnification, 50x magnification (inserted image), and (b) 20,000x magnification and (c) XRD patterns.

Figure 3

(a) Surface resistivity of para-aramid knit dip-coated with graphene/WPU composite and the electrical conductivity for the five-coat samples for different hot press temperatures (insert images). (b) Capacitance of the coated knit hot-pressed at 140 °C on a touchscreen (insert image). (c) Surface temperature of coated knit with different hot press temperatures and applied voltages. (d) Thermal image of five-coat knit with 50 V applied and (e) Electrical heating behavior of samples by different hot-press temperature with applied 50 V.

Figure 4

Digital photograph of a graphene/WPU dip-coated glove obtained by (a) direct coating and (b) sewing. The coating on the glove can be detected well by the touchscreen with both the (c) direct coating and (d) sewing methods. (e) Thermal image of the gloves with voltage applied.

Figure 5

Illustration of the fabrication process for graphene/WPU dip-coated on para-aramid knit, which consists of three steps: (a) Preparation of graphene/WPU composite solution, (b) Dip-coating para-aramid knit with various coating cycles, and (c) Hot-pressing with different temperatures.