Electrical conductivity in biocomposites via polypyrrole coating

The aim of this work was to create a biocomposite material with controllable electrical resistance for lightweight engineering made from regenerated cellulose-based fibers and a partially biobased epoxy resin. In this feasibility study viscose fabrics were coated with polypyrrole (PPy) by in situ polymerization of pyrrole (Py) and iron(III)-chloride as an oxidizing agent for the insertion of an electrical conductivity. Para-toluene sulfonic acid (pTSA) and 9,10-anthraquinone-2,6-disulfonic acid disodium salt (AQSA) were used as dopant agents to induce the conductivity. The treated viscose fabrics were incorporated into an epoxy matrix via vacuum infusion process and the resulting biocomposites were afterwards analyzed by electrical four-point measurement and three-point bending test. The surface of the coated fibers and the fracture surface after the bending test were analyzed via scanning electron microscopy (SEM). Through varying the pyrrole concentration between 3 and 6 g/l and the oxidizing/dopant agent ratio between 2:1 and 2:4, a significant reduction of electrical resistance was obtained. The lowest electrical resistance, 50 Ω/sq by the coated viscose fabrics and 7 Ω/sq by the corresponding biocomposites, was achieved by using the dopant/oxidizing ratio of 2:2. These results showed that the coating with pyrrole is a promising approach for the manufacture of electrically conductive biocomposite materials.