Abstract
In this study, novel silane functionalized graphene oxide (PVSQ-GO) composite material is synthesized through the hydrolysis condensation reaction of vinyl triethoxysilane monomers occurred at the surface of graphene oxide. Results obtained from FTIR, Raman, X-ray photoelectronic spectroscopy (XPS), XRD and TGA measurements reveal that polyvinyl sesquisiloxane microspheres adhere to graphene oxide lamellae in the form of chemical bonds. Meanwhile, it is intuitive that abundant polyvinyl sesquisiloxane microspheres stick to the surface of graphene oxide and increase the thickness of the flake. Modified graphene oxide changes from hydrophilicity to hydrophobicity were owing to the existence of polyvinyl sesquisiloxane microspheres on the surface of graphene oxide (GO). PVSQ-GO composite exhibited good dispersion in eco-friendly waterborne polyurethane coating. Electrochemical impedance spectroscopy manifested that the anti-corrosion performance of waterborne polyurethane (WPU) coating embedded at 0.5 wt.% PVSQ-GO composite improved effectively. Tafel curves reveal that 0.5 wt.% PVSQ-GO/WPU coating specimen shows the lowest corrosion rate of 8.95 × 10−5 mm/year when compared with the other coating specimens. The good anti-corrosion abilities of PVSQ-GO composite coating can be interpreted as the good compatibility between PVSQ-GO composite and waterborne polyurethane, however, the intrinsic hydrophobicity of PVSQ-GO composite is beneficial to inhibit the permeation of corrosive medium and thus slows down the corrosion rate.
Highlights
Graphene, a novel two-dimensional carbon nanomaterial with a special single-atom-thick lamellar structure, which urges with graphene, possesses some superior properties, such as thermal stability [1], good conductivity [2], excellent mechanical properties [3,4], high specific surface area [5] and impermeability, [6] etc
graphene oxide (GO) and polyvinyl sesquisiloxane (PVSQ)-GO were well dispersed after ultrasonication for 30 min (Figure 2a), but after 24 h storage, GO aqueous solution was partly deposited at the bottom of the bottle, while there was no obvious stratification phenomenon in PVSQ-GO aqueous solution (Figure 2b)
The surface of GO was wrinkled and uneven, and the contact angle of GO was about 70.2◦. It exhibited a hydrophilic property because there were amounts of oxygen-containing functional groups on the surface of the GO sheet, but after being modified, a large number of microspheres covered the surface of the prepared PVSQ-GO hybrids (Figure 4b), which was attributed to the hydrolysis and condensation reaction of vinyltriethoxysilane which took place on the surface of GO
Summary
A novel two-dimensional carbon nanomaterial with a special single-atom-thick lamellar structure, which urges with graphene, possesses some superior properties, such as thermal stability [1], good conductivity [2], excellent mechanical properties [3,4], high specific surface area [5] and impermeability, [6] etc. There are reports that graphene grown on copper may accelerate the oxidation of copper under ambient conditions because it provides an additional electron channel that induces the rapid formation of oxygen ions at the air/oxide interface [7,13] It would be a great failure for graphene coating to offer a long period of anti-corrosion effects owing to the existence of microgalvanic corrosion once a defect has formed [14,15]. Encapsulated graphene sheets in insulating materials (3-aminopropyl)-triethoxysilane (APTES) to form a reduced graphene oxide@APTES sandwich structure composite, the barrier properties of the polyvinyl butyral coating improved remarkably by embedding appropriate amounts of the composite in the coating and the corrosion-promotion activity of graphene was completely inhibited They investigated the functionalization degree of graphene which would influence the anti-corrosive performance of the composite coatings. The results showed that addition of 0.5 wt.% PVSQ-GO composite coating exhibited better barrier properties
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