Polydopamine/polyethyleneimine co-crosslinked graphene oxide for the enhanced tribological performance of epoxy resin coatings

To enhance the wear resistance of graphene oxide (GO) nano-filled epoxy resin (EP) coatings with excellent dispersion, GO were modified using a co-crosslinking strategy between polydopamine (PDA) and polyethyleneimine (PEI) through an environmentally friendly, simple and low-cost process. High-density amino-branched PEI and highly adhesive PDA formed covalent bond cross-links with GO (PDA/PEI-GO) through the Michael addition and Schiff base reactions. With the introduction of amino active sites, the PDA self-polymerization reaction time was significantly shorted from 24 to 6 h. The covalently cross-linked network increased the lamellar spacing of GO and enhanced the interfacial bonds between the PDA/PEI-GO lamellae and EP matrix. Due to the improved dispersion and surface activity of GO, the PDA/PEI-GO nano-filled EP coating exhibited excellent wear resistance. Reciprocating friction with GCr15 stainless steel ball, the average friction coefficient and wear rate of the coating were reduced by 31.9% and 62.7%, respectively, compared to the pure EP coating. In addition, the wear mechanism of the PDA/PEI-GO/EP coating changed from adhesive and fatigue wear to abrasive wear, and it maintained good wear resistance by forming a GO lubrication transfer film on the counterpart surface. Therefore, this study may provide a new strategy for improving the dispersion of graphene in wear-resistant polymer materials for practical applications.