Study of electrical percolation of hybrid polyester nanocomposites with carbon black and carbon nanotubes

This work investigated the role of carbon nanotubes (CNTs) and carbon black (CB) nanoparticles in a polyester resin matrix. The objective was to develop nanocomposites that integrated these nanoparticles, aiming to overcome the electrical insulation of the resins and enabled the electrophoretic deposition of paint on metallic surfaces. Nanocomposites at different mass fractions (w/w) of CNTs and/or CB were prepared by means of in-situ high-energy sonication/polymerization. Several techniques were employed to characterize the nanocomposites, such as FTIR, FESEM, TEM, impedance spectroscopy, DSC, and nano-indentation. For the nanocomposites of polyester with carbon black, the studied compositions were 1.5, 3.0, 5.0, 6.0, and 7.0 wt%, and for nanocomposites with carbon nanotubes, mixtures with compositions of 0.1, 0.2, 0.3, 0.5, 1.0, 1.5, and 2.0 wt% were prepared in both cases in w/w basis. According to the measurements, the percolation threshold was reached at 0.3 w/w% for CNTs and at 3.0% for carbon black. Before the percolation threshold, the glass transition temperature for both series of nanocomposites showed a depression and, after that, a recovery. A similar behavior was observed for Young’s modulus near the glass transition temperature. The simultaneous mixture of both nanomaterials resulted in significant synergy, increasing the electrical conductivity of the samples up to 100-fold compared to those samples having only carbon nanotubes. It was observed that carbon black nanoparticles filled the empty spaces between the carbon nanotubes, favoring the interactions among them and contributing to the improvement of the electrical properties.

Graphical abstract