Effect of Secondary Particles on Self-Healing and Electromechanical Properties of Polymer Composites Based on Carbon Black and a Diels-Alder Network

The addition of an organomodified nanoclay to a carbon-based electrically conductive self-healing composite showed a synergistic improvement of the electrical conductivity and self-healing ability of the formed hybrid composites. The effect on the electrical, viscoelastic, and self-healing properties was studied for Diels-Alder-based reversible polymer networks with a maleimide-to-furan stoichiometric ratio of 0.6, with different loadings of carbon black Ensaco 360G and nanoclay Cloisite 15A. Hybrid composites were prepared with carbon black contents from 5 to 15 wt % and nanoclay loading up to 1.5 wt %. The percolating network of conductive particles led to decent electrical conductivity of the order of 0.46 S m(-1) at carbon black loadings of 7.5 wt % and higher. The increase in electrical conductivity was most pronounced at the lowest carbon black loadings, while the improvement of the self-healing properties was most pronounced just above the percolation threshold. The resulting structure-property relations enabled optimization of the filler composition to achieve the best combination of electrical and self-healing properties by exploiting the synergistic effect of the secondary filler. Finally, the electromechanical properties of selected hybrid composites with the best combinations of the two fillers were studied for sensor applications. Self-healing strain sensors showed distinct responses depending on the combination of fillers with decent recovery after the damage-healing process. These promising results suggest the use of the studied electrically conductive and self-healing hybrid composites for deformation and damage-sensing applications in flexible electronics and soft robotics.