Electric heated cotton fabrics with durable conductivity and self-cleaning properties

Abstract

This study was carried out to improve durability and reduce conductivity degradation of polypyrrole-deposited cotton fabrics by introducting a superhydrophobic surface. An in situ polymerization method was used to polymerize the polypyrrole on the cotton fabric, and the surface energy was lowered using n-dodecyltrimethoxysilane to create a superhydrophobic surface. In particular, to investigate the durability of the conductivity according to the superhydrophobic surface, the changes of surface resistance were examined after repeated exposure to air, moisture, and friction. The polypyrrole-deposited cotton fabric displayed excellent electrical heating features originating from the conductive polymer, although the surface resistance was somewhat increased by the superhydrophobic coating. In addition, nano-roughness was obtained by the pyrrol-deposition on the fabric surface, creating a dual-roughness property required for the superhydrophobic surface. Accordingly, the conductive superhydrophobic cotton fabric had a contact angle of more than 150° and a shedding angle of less than 10°, maintaining superhydrophobicity even during electrical heating. Above all, the superhydrophobic layer contributed to the functional durability of the conductive fabrics by protecting the conductive layer. After atmospheric aging for 20 weeks, undergoing a water spray test for 20 cycles, and a rubbing test with tape, the increment of surface resistance of the superhydrophobic coated cotton fabrics with polypyrrole was increased by up to 30% compared to the polypyrrole treated specimen without the coating, which showed a decrease of conductivity of over 74%. It is confirmed that the self-cleaning properties can easily remove dirt on the cotton fabric surface by roll-off of water droplets, thereby preventing the degradation of conductivity due to moisture and contamination.

Fig. 1. Scheme of the experimental process.

Fig. 2. Photo of polypyrrole deposited cotton samples.

Fig. 3. SEM images of pristine cotton (a and b), polypyrrole deposited cotton (c and d) and polypyrrole deposited and hydrophobic coated cotton (e and f).

Fig. 4. Photos of LED lamps connected to the polypyrrole deposited and hydrophobic coated cotton fabric.

Fig. 5. Surface temperature increment of polypyrrole deposited and hydrophobic coated cotton fabrics (a) and infrared thermal images at 10 min (b).

Fig. 6. Water contact angles and shedding angles of the cotton fabrics after polypyrrole deposition and hydrophobic coating.

Fig. 7. The photo (a) and infrared thermal image (b) of sample with electro heating effect and superhydrophobicity.

Fig. 8. Images of self-cleaning effect by water at tilting angle (a) 10°, (b) 7°, and (c) 5°.

Fig. 9. Schematic view of water droplet on a tilted surface.

Fig. 10. Photos of the polypyrrole deposited and hydrophobic coated cotton fabric after scattering silicon carbide particles on the surface and cleaning with water droplet.

Fig. 11. Effect of atmospheric ageing on the surface resistivity of cotton fabrics treated with polypyrrole deposition and hydrophobic coating.

Fig. 12. The rubbing fastness (a), and contact angles and shedding angles (b) of the cotton fabrics treated with polypyrrole deposition and hydrophobic coating after testing with roll tape cleaner.

Fig. 13. Water attack at an α-carbon on a pyrrole ring leading to chain opening.

Fig. 14. Effect of moisture on the surface resistivity of the cotton fabrics treated with polypyrrole deposition and hydrophobic coating.