The reduced graphene oxide reinforced silicone-acrylate resin composite films (rGO/SAR composite films) were prepared by in situ synthesis method. The structure of rGO/SAR composite films was characterized by Raman spectrum, atomic force microscope, scanning electron microscopy, and thermogravimetric analyzer. The results showed that the rGO were uniformly dispersed in silicone-acrylate resin matrix. Furthermore, the effect of rGO loading on mechanical properties of composite films was investigated by bulge test. A significant enhancement (ca. 290% and 320%) in Young’s modulus and yield stress was obtained by adding the rGO to silicone-acrylate resin. At the same time, the adhesive energy between the composite films and metal substrate was also improved to be about 200%. Moreover, the erosion resistance of the composite films was also investigated as function of rGO loading. The rGO had great effect on the erosion resistance of the composite films, in which the
An intense effort is underway to find coatings that inhibit the process of metal corrosion, a problem costing US industries more than $200 billion annually [
In this study, the GNS reinforced silicone-acrylate resin composite thin film was prepared by the in situ synthesis method. Furthermore, their mechanical properties (i.e., elastic modulus, yield stress, and adhesive energy) were characterized by the modified bulge test. Moreover, erosion resistance of GNS-based silicone-acrylate resin coating was also investigated by electrochemical measurements. These results are very important to improve the mechanical properties and erosion resistance of polymer coating, which is used as a stable protective layer applied in metal corrosion.
Nature graphite flakes (325 mesh, 99.8%), sodium hydroxide emulsion (37.0 wt%), and other chemicals and reagents used in this work are of analytical grade. Deionized water was used for preparation, dilution, and analytical purpose.
rGO was prepared from natural graphite by our own group, and the preparation process was shown in previous work [
Raman spectrum was collected on a Jobin-Yvon LabRam HR800 Raman spectroscope equipped with a 514.5 nm laser source.
AFM images were taken of rGO by a NTMDT NTEGRA SPM instrument with NSG03 noncontact “golden” cantilevers.
The morphology of samples was observed by scanning electron microscopy (SEM) (Su-1500, HITACHI, Japan) with an accelerating voltage of 20 kV.
Thermogravimetric analysis (TGA) was carried out using a TA Q600 instrument in a temperature range from 20 to 600°C with a heating rate of 10°C min−1 in air.
Mechanical properties of polymeric coating were characterized by the bulge test as shown in Scheme
The bulge test setup used in present work.
Preparation of sample used in bulge test was shown in Scheme
Schematic illustration for the stepwise preparation of the sample used in bulge test.
The generalized equation for bulge test has been established by Huang et al. [
For the small strain case, the yield stress expression can be expressed as [
For the elastic strain case, the adhesive energy expressions can be expressed as [
As a typical procedure to prepare samples for corrosion measurements, freshly the rGO/silicone-acrylate resin mixture solution was coated onto the Zn plate (2.0 cm × 2.0 cm) and the rGO/silicone-acrylate resin composite film dried for 2 h at 80°C. The rGO/silicone-acrylate resin composite film with Zn plate substrate was then mounted to the working electrode. The other uncoated side and edges of Zn plate were sealed with super-fast epoxy cement (SPARR).
All the electrochemical measurements of corrosion potential and corrosion current were performed on a Volta Lab model 21 Potentiostat/Galvanostat in a standard corrosion test cell equipped with a saturated calomel reference electrode (SCE) and a working electrode, and all experimental data were repeated at least three times. The electrolyte was an aqueous solution containing 3.5 wt% of sodium chloride. Open circuit potential (OCP) at the equilibrium state of the system was recorded as the corrosion potential [
The Raman spectrum of rGO/silicone-acrylate resin composite film was shown in Figure
(a) Raman spectrum and (b) AFM of polymer composite film.
The structure of rGO/silicone-acrylate resin composite film was investigated by the SEM as shown in Figure
SEM of polymer composite film with various rGO contents of (a) 0, (b) 0.27 wt%, (c) 1.1 wt%, and (d) 1.93 wt%. The insets show the photographs of polymer composite films.
Figure
TG curves of polymer composite films with various rGO contents of (a) 0, (b) 0.27 wt%, (c) 1.1 wt%, and (d) 1.93 wt%.
Figure
The mechanical properties of the polymer composite film measured by the bulge test.
Loading (wt%) | Biaxial modulus (GPa) | Young’s modulus (GPa) | Residual stress (MPa) | Yielded stress (MPa) |
|
---|---|---|---|---|---|
0 | 0.08 | 0.05 | 4.6 | 8.2 | 5.5 |
0.27 | 0.13 | 0.07 | 10.3 | 14.8 | 6.1 |
1.10 | 0.25 | 0.14 | 10.5 | 24.1 | 11.4 |
1.93 | 0.20 | 0.11 | 12.2 | 22.7 | 12.3 |
The bulge test data of polymer composite films with various rGO contents of (a) 0, (b) 0.27 wt%, (c) 1.1 wt%, and (d) 1.93 wt%.
Adhesion energy of rGO/silicone-acrylate resin composite film against the rGO content was calculated by (
The corrosion protection of Zn plates by rGO/silicone-acrylate resin composite film was investigated by electrochemical impedance spectroscopy as shown in Figure
Anticorrosive performance of polymer composite film measured from electrochemical measurements.
Loading |
|
|
|
---|---|---|---|
0 | −327 | 13.8 | 28.7 |
0.27% | −878 | 6.2 | 4.6 |
1.1% | −585 | 0.45 | 0.8 |
1.93% | −976 | 6.7 | 5.0 |
The Tafel plots for polymer composite films with various rGO contents of (a) 0, (b) 0.27 wt%, (c) 1.1 wt%, and (d) 1.93 wt%.
Figure
SEM images of uncoated Zn plate (a) before and (b) after corrosion; Zn plate coated polymer composite films with various rGO contents of (c) 0, (d) 0.27 wt%, (e) 1.1 wt%, and (f) 1.93 wt%.
The rGO/silicone-acrylate resin composite films were prepared by in situ synthesis method and the rGO was well dispersed in the silicone-acrylate resin matrix and had good adhesion with silicone-acrylate resin matrix. Furthermore, the bulge tests were used to investigate the mechanical properties of rGO/silicone-acrylate resin composite films. The result measured by the bulge tests clearly showed that elastic modulus, yield stress, and adhesive energy of silicone-acrylate resin films were obviously improved by the introduction of rGO. Moreover, the erosion resistance of rGO/silicone-acrylate resin composite film was also better comparing to the pure silicone-acrylate resin film. These results provide a novel route for studying and improving mechanical properties of rGO/polymer composite film with good erosion resistance. And the further investigations in erosion resistance of rGO/silicone-acrylate resin composite film under mechanic-corrosion coupled field have been carried out by our group.
The authors declare that there is no conflict of interests regarding the publication of this paper.
The authors are grateful for the support by National Natural Science Foundation of China (under Grants 11202006 and 11202007), University’s Science and Technology Exploiture of Shanxi Province (20121010), and the Shanxi Provincial Natural Science Foundation of China (2014021018-6).