PET fabric/polypyrrole composite with high electrical conductivity for EMI shielding

Polypyrrole (PPy) was polymerized chemically and electrochemically in sequence on a polyester (PET) woven fabric, giving rise to PET fabric/PPy composite with high electrical conductivity. In the chemical polymerization, pyrrole dissolved in an aqueous solution without or with polyvinyl alcohol as a surfactant was first sprayed on the PET fabric and oxidized by spraying an aqueous solution of an oxidant and a dopant. Electrochemical polymerization was carried out in an aqueous electrolyte solution by applying a constant current density to the PET fabric coated with chemically polymerized PPy and a stainless steel plate as the working and the counter electrodes, respectively. We investigated the effects of the chemical or the electrochemical polymerization conditions on the properties of the resulting composite such as surface morphology, electrical conductivity, environmental stability, and electromagnetic interference shielding effectiveness (EMI SE). We found that the composite shielded EMI by absorption as well as reflection and that EMI shielding through reflection increased with the electrical conductivity. The specific volume resistivity of the composite prepared in this study was extremely low as 0.2 52 cm and EMI SE was in the practically useful range of about 36 dB over a wide frequency range up to 1.5 GHz. (C) 2002 Elsevier Science B.V. All rights reserved.