Polyaspartic polyurea/graphene nanocomposites for multifunctionality: Self-healing, mechanical resilience, electrical and thermal conductivities, and resistance to corrosion and impact

Polyurea elastomers have attracted increasingly more attention due to excellent mechanical performance, and their wide industrial applications are in need of multifunctionality such as thermal conductivity. We herein prepared polyaspartic polyurea elastomers with optimal tensile strength and fracture strain by adjusting the isocyanate index and free isocyanate content. As a class of nanofiller, isocyanate-modified graphene nanoplatelets (IP-GNPs) were developed and they formed a stable, robust interface with the polyurea matrix, resulting in mechanical reinforcement and multifunctionality. The nanocomposite at 0.05 vol% of IP-GNPs revealed a tensile strength of 15.72 ± 0.67 MPa, representing an increment of 108.21% over pure polyurea, with excellent resistance to acidic and alkali corrosion. After 9 h of post-maintenance at 60 °C, the nanocomposite reached a healing efficiency up to 80.10% as driven by hydrogen bonds. An electrical percolation threshold was observed at 3.61 vol% of IP-GNP for the nanocomposites. The thermal conductivity reached 38.49 W/m K at 7.00 vol% due to the formation of the IP-GNP network in polyurea, where the electron thermal conductivity plays a dominant role. In comparison with those high thermal conductivity values obtained by back-filling polymers into a network established beforehand, this facile approach would be highly favored in industry for the development of elastomer nanocomposites with multifunctionality for many applications, e.g. smart sensors, protective coatings, energy harvesting, etc.