Electrical heating properties of various electro-circuit patterns coated on cotton fabric using graphene/polymer composites

To investigate the electrical heating performance of two types of electro-circuit patterns, stripe-pattern (SP) and horseshoe-pattern (HP) types were designed by using graphene/poly(vinylidene fluoride- co-hexafluoropropylene) composites to fabricate electrical heating textiles for the inner layers of clothing and gloves to maintain body temperature. To confirm the electrical properties of the pattern shape and area of the coated circuit, the surface resistivity of SP and HP types was measured with various sample lengths, namely 100, 75, and 50 mm, respectively. The surface resistivity of each sample tends to increase linearly with the increasing size of the coated area. In addition, the surface resistivity of the HP is found to be higher than that of the SP. It could be confirmed that the surface resistivity increases as the curvature increases. For the electrical heating properties of the HP, a white-zone and a red-zone appeared clearly, and locally excess heat appeared at the white-zone; the resistive heat can be explained by the collision of the free electrons in the curved shape of the HP area. In order to confirm the applicability of the fabric heating elements, HP100/cotton, HP75/cotton, and HP50/cotton were fabricated by applying the HP to cotton fabric. The difference of surface temperatures at two points of each line of HP100/cotton, HP75/cotton, and HP50/cotton were about 6.0 ± 2.4℃, 6.8 ± 4.5℃, and 3.5 ± 1.7℃, respectively. It has been confirmed that the heating performance is improved, due to the collision of electrons in the curved region with decreasing HP100/cotton to HP50/cotton ratio, and the white-zone is also increased.