Phosphorylated polymer/anionic surfactant doped polypyrrole in waterborne epoxy matrix toward enhanced mechanical and chemical resistance

Abstract

The compatibility between polypyrrole (PPy) and waterborne epoxy coating (EP) remains the main challenge. Here, phosphorylated poly (vinyl alcohol) (PPVA) and p-toluene sulfonic acid sodium (p-TSA) were simultaneously utilized as dopants to modify PPy and prepare water dispersible PPVA/p-TSA/PPy (PPVAT/PPy) solution. Additionally, poly (vinyl alcohol) (PVA) and TSA were also adopted to prepare PVA/p-TSA/PPy (PVAT/PPy) for comparison. Denser film with granular morphology was observed for PPVAT/PPy nanocomposite film. Compared with PVAT/PPy-40 %, the tensile strength of PPVAT-8.0 %/PPy-40 % increased from 248.8–283.9 MPa. PPVAT/PPy displayed higher compatibility and interactions with EP compared to PPy-TSA and PVAT/PPy. Compared with EP, the impedance modulus of PVAT/PPy+EP and PPVAT/PPy+EP increased from 3.17×105 to 1.07×108 and 1.62×109 Ω·cm2; corrosion current density Icorr decreased from 1.49×10−6 to 7.72×10-8 and 4.01×10-9 A·cm-2; corrosion potential Ecorr displayed a positive shift of 230 mV and 269 mV, respectively. The corrosion inhibition efficiency of PPVAT/PPy+EP reached 99.83 %, which is much higher than that of PVAT/PPy+EP (93.97 %). PPVAT/PPy+EP nanocomposite coating has been proved to have preferable long-term corrosion resistance based on electrochemical impedance spectra (EIS), polarization curves and salt water spray test. The simultaneous incorporation of phosphate anions, sulfate ions and PPy into EP was beneficial to fabricate high-performance anticorrosion coating.