Studies of electrically conductive textile coatings with PEDOT:PSS

Licentiate thesis, 2012

This study investigates electrically conductive coatings of textiles, obtained with a direct coating and the addition of poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS) dispersion to a thickened polyurethane (PU)-based formulation. Textiles with enhanced electrical conductivity have potential applications in antistatic, electrostatic discharge protective, electromagnetic interference shielding, sensoric and temperature-regulating products. The composition of the coating formulation will have a large impact on the obtained coated textiles. Firstly, the amount solids (polymer content) of the components will affect the shear viscosity which is amongst other important for the level of penetration of the coating. In this work, different coating formulations have been studied with steady state shear viscometry. It was found that the viscosity during knife coating to a large extent could be controlled by the addition of a hydrophobically modified ethoxylated urethane (HEUR) rheology modifier. Secondly, the level of conductivity will depend on the amount conductive material, in this case PEDOT:PSS, that is present in the coating, indicating percolation behaviour of the system. Conductivity was evaluated with two-point and four-point surface resistivity measurements. Addition of a high-boiling solvent, i.e. ethylene glycol, was however imperative for low surface resistivity. Thirdly, tear strength measurements, performed with the dynamic pendulum method, and investigations of bending rigidity, with the Kawabata evaluation system for fabrics, KES-F-2, showed that samples coated with formulations containing larger amounts of PEDOT:PSS and ethylene glycol were significantly softer and more ductile than samples coated with formulations containing more binder. A decrease in surface resistivity could also be obtained by increasing the amount deposited coating on the substrate. This decrease was however counteracted by the concurrent increase of insulating binder polymers in the coating. The increased coating deposit resulted in stiffer samples with lower tear strength due to increased brittleness. The influence of kinetics during film formation on the surface resistivity was also studied but was found to be close to insignificant. Abrasion resistance was investigated for all samples with a modified Martindale method and the samples showed less impact from this than expected.