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

Abstract

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.

Designing Flexible and Self-Healing Electronics Using Hybrid Carbon Black/Nanoclay Composites Based on Diels–Alder Dynamic Covalent Networks

“…The electrical conductivity of the hybrid composites based on 10 wt % CB360G and Cloisite 15A was previously shown to be higher than that of the CB-filled composite Figure c shows how the electrical conductivity of the hybrid composite with 1 wt % of C15A is about 50% higher than that of the reference CB composite.…”

“…Previous studies proved that the addition of an organo-modified nanoclay to a carbon black-based electrically conductive self-healing composite shows a synergistic improvement of the electrical conductivity and healing ability . Nevertheless, striking a balance between these two aspects requires careful material design in terms of the selection of appropriate materials as well as consideration of the different design parameters in such a complex polymer system.…”

“…It was previously reported that the hybrid composite DPBM-FT5000_r0.6_10%CB360_1%C15A prepared by magnetic stirring showed a higher electrical conductivity compared to its CB-filled composite, without a secondary filler . Etika et al suggested a theory about how carbon black and nanoclay platelets are arranged in their hybrid network .…”

“…As a primary filler, carbon black reinforces the Diels–Alder network DPBM-FT5000_r0.6. Besides, it was shown that the introduction of Cloisite 15A as a secondary filler leads to further enhancement of the mechanical properties . The sonication process for the dispersion of nanoclay platelets slightly increases the stiffness of the hybrid composites at larger deformations, but their overall mechanical performance remains unchained.…”

“…Designing flexible and self-healing electronics using conductive composites based on Diels–Alder polymer networks is concerned with the trade-off between self-healing properties and electrical conductivity. A critical consideration involves finding a balance between two competing factors such as electrical properties or mechanical properties and self-healing properties in polymer composites. , It was reported in a previous work that using an organo-modified nanoclay Cloisite 15A as a secondary filler synergistically improves the electrical conductivity and self-healing behavior of carbon black composites . The self-healing polymer matrix is based on the reversible Diels–Alder cycloaddition of a furan-functionalized Jeffamine FT5000 that is cross-linked by bismaleimide DPBM with a maleimide-to-furan stoichiometric ratio r of 0.6.…”