Abstract
Graphene, the typical two-dimensional sp2 hybridized carbon allotrope, is widely used as a filler for improving the mechanical performance of polymers. However, its superhydrophobic surface makes it a big challenge to obtain stable graphene dispersions, especially in water-borne systems. On the contrary, graphene oxide (GO) shows excellent dispersibility in water, but strong oxidants and acids destroy its structure and degrade its mechanical properties. This largely limits its application in water-borne coatings. In this work, graphene from mechanical exfoliation was surface modified by p-aminophenol derived diazonium salt to achieve a homogenous dispersion. Moreover, the hydroxyl groups in p-aminophenol are able to combine with epoxy resins during the curing process to improve mechanical performance of the final coatings. The result shows that functionalized graphene shows a lower coefficient of friction and better abrasion resistance compared to GO.
Highlights
Epoxy resins (ER) are an important engineering material featuring outstanding corrosion resistance, high mechanical strength, and strong adhesion to heterogeneous substrates [1,2]
TEM was used to observe the influence of functionalization on graphene morphology
Exfoliated graphene was surface modified using an aryl diazonium salt in order to improve its dispersibility in water
Summary
Epoxy resins (ER) are an important engineering material featuring outstanding corrosion resistance, high mechanical strength, and strong adhesion to heterogeneous substrates [1,2]. When used in water-borne coating systems, the primary challenges is to produce stable homogenous graphene dispersions To address this issue, surface modifications, involving covalent and noncovalent hydroxyl and carboxyl functionalization, have been performed on the surface of graphene through the edges or defect sites to improve graphene’s dispersibility [3,13]. Epoxy groups are able to react with the functional groups grafted onto graphene, including hydroxyl, amino, etc., [14] to build a stable crosslinked network between functional graphene and an epoxy binder [15] Such crosslinking is favorable for the mechanical performance of graphene-filled composites. The hydroxyl groups are able to further react with the epoxy groups to build a strong bonding between the graphene flakes and the epoxy binder, significantly improving the tribological properties of the epoxy coating. Compared with graphene oxide (GO), the functionalized graphene (FG) sample exhibits a lower coefficient of friction and higher abrasion resistance
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