Polypyrrole as a protective pigment in organic coatings

This study deals with the preparation and characterization of polypyrrole (PPy) using ferric chloride and ammonium dichromate as oxidants and also with the addition of a common surfactant in aqueous solution. The combination of oxidant and surfactant in the preparation of PPy has shown that there is an enhancement in conductivity and also in the yield of the PPy. The deprotonated PPy exhibits a better stability with decreasing conductivity. Fourier transform infrared spectroscopy (FTIR) confirmed that the surfactant radical sulphoxide got incorporated into the PPy as a dopant and also the presence of chromate radical was indicated by the appearance of peak at 459 cm−1. Thermo Gravimetric Analysis (TGA) indicates that the weight losses for PPy-Cl and PPy-CrO4 are 97% and 35-50% at 1000 °C, respectively. X-ray diffraction (XRD) studies also give an idea about the size and shape of the polymer. The corrosion resistance property of PPy-incorporated coatings on mild steel substrate in sodium chloride solution indicates that the PPy-CrO4/epoxy-polyamide coating gives maximum duration of protection compared with other systems.