Development of Polyurethane/r-GO Nanocomposites with Improved Self-healing Properties*

In recent years, self-healing coatings have been the subject of increasing research interest due to their ability to self-repair local damages caused by external forces. Polymeric materials comprise one of the most promising materials to use towards this direction. At the same time, incorporation of nanoadditives within a polymeric matrix is a common strategy to improve their mechanical, thermal and self-healing properties. In the current work, reduced graphene oxide (rGO) was incorporated within a waterborne polyurethane dispersion to develop nanocomposites in different compositions and investigate its effect on the self-healing properties. The polyurethane was based on a polycarbonate polyol whereas graphene oxide (GO) was synthesized via a modified Hummers method from graphite; subsequent reduction using hydroiodic acid (HI) as a reducing agent produced the rGO used. The presence of rGO enhanced the self-healing of the polyurethane coatings with a healing rate much higher compared to that of the pure polymer, as confirmed by microscopic techniques. This was mainly due to better heat dissipation where the high heat conductivity of rGO allowed for the improvement of the self-healing ability with the incorporation of just a small amount of the additive. The effect of the presence of rGO on the mechanical properties of the nanocomposites after healing was investigated, as well.