Enhanced outdoor durability of polyurethane nanocomposite coatings with green reduced graphene oxide nanoplatelets

Obtaining the highest possible level of weathering resistance to protect the polymeric composites against sunlight and free radicals is the primary function of every exterior composite, such as polyurethane (PU). In this paper, a typical PU matrix was modified by two differently reduced graphene oxide nanosheets to enhance longterm weathering stability. The synthesized graphene oxide nanosheets were reduced by Nettle leaves extract as a green reductant and hydrazine as a typical reducing agent. The graphene oxide and two reduced species were embedded in PU to investigate their impact on weathering stability. Several techniques were employed to assess the weathering performance during 1400 h exposure to artificially accelerated conditions. Achieving superior weathering performance approved the effective role of reduced graphene oxide (especially green reduced) in elevating weathering stability of PU nanocomposites. The active mechanisms involved in such improvement were extensively discussed.