Synthesis of conducting PANi/SiO₂ nanocomposites and their effect on electrical and mechanical properties of antistatic waterborne epoxy coating

Polyaniline (PANi) has been intensively incorporated in epoxy coatings as a conducting material. However, epoxy coatings containing PANi have poor mechanical properties. In this study, polyaniline/silica (PANi/SiO₂) nanocomposites with different contents of silica were prepared via in situ chemical oxidative polymerization method. Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), and zeta potential measurements were used to examine the structure and the morphology of synthesized PANi/SiO₂ nanocomposites. The thermal and electrical properties of the nanocomposite were studied by thermogravimetric analysis (TGA) and standard four-probe electrode method. It was shown that silica (SiO₂) nanoparticles were covered by PANi in PANi/SiO₂ nanocomposites and the electrical conductivity of nanocomposites decreased with the increase in SiO₂ content. The PANi/SiO₂ nanocomposite with 4.1 wt% SiO₂ had a conductivity of 7.6 × 10⁻² S/cm and that of PANi was 8.7 × 10⁻² S/cm. Consequently, epoxy coatings containing 30 wt% PANi/SiO₂ nanocomposites displayed a higher surface and volume resistance than the one containing pure PANi. In contrast, the increase in SiO₂ content in PANi/SiO₂ nanocomposite enhanced the mechanical properties of the epoxy coating, compared to epoxy coating containing pure PANi. The coating containing PANi/SiO₂ nanocomposite with 17.2 wt% silica presented good mechanical properties (20 L/mil abrasion resistance, 100 kg cm impact strength) and admissible surface and volume resistivity (1.3 × 10¹¹ Ω/cm² and 6.6 × 10¹⁰ Ω cm, respectively) for antistatic coatings.