STUDYING THE INFLUENCE OF DESIGN PARAMETERS IN CARBON BLACK/NANOCLAY SELF-HEALING COMPOSITES BASED ON DIELS-ALDER POLYMER NETWORKS: STUDYING THE INFLUENCE OF DESIGN PARAMETERS IN CARBON BLACK/NANOCLAY SELF-HEALING COMPOSITES BASED ON DIELS-ALDER POLYMER NETWORKS

The addition of an organo-modified nanoclay to a carbon black-based electrically conductive self-healing composite showed a synergistic improvement of the electrical conductivity and healing ability in a Diels-Alder polymer network. The impact of other design parameters on this synergy was investigated. In the first step, it was found that magnetic stirring of nanoclay particles over a longer time yields the desired morphology of hybrid fillers in which carbon black particles are organized around the partially exfoliated nanoclay platelets, while sonication with high amplitude for a short time results in loss of the healing ability and also partial loss of the electrical conductivity of the hybrid composites. Moreover, the synergy caused by incorporating nanoclay platelets in a Diels-Alder network is governed by the compatibility of their organic modifier either with the polymer network or carbon black particles as well as their interlayer spacing. That is why the incorporation of Cloisite 15A with an apolar modifier in a polypropylene oxide-based Diels-Alder network results in decent electrical conductivity and self-healing properties. Filled with a constant combination of fillers, finally, different networks were studied by varying their chemistry and crosslinking density. The study revealed that using a compatible nanoclay such as Cloisite 30B containing a more polar modifier in a polyethylene oxide-based network renders the largest improvement of the mechanical properties while deteriorating the electrical conductivity and self-healing properties. In addition, it was concluded that for a constant stoichiometric ratio of furan and maleimide reacting groups, the final properties of the hybrid composites and in particular the synergy caused by combining carbon black and nanoclay rely on the number of crosslinks. It was proved that there is an optimum stoichiometric ratio at which the effect of secondary filler is more pronounced.