Investigating the effects of silanized graphene based nanocomposite coatings on fiber reinforced composites exposed to UV light and salt fog environments

Abstract

This report presents the development of a nanocomposite coating using nano graphene platelets associated with an epoxy primer to improve the coating resistance against corrosion and weathering. It was hypothesized that coatings containing nanoadditives would be more resistant to degradation than coatings without nanoadditives; but also that by modifying the graphene particles through a surface modification technique called 'silanization' before inclusion in the coating, the stability of the graphene particles would be improved and hence improve the resistance of the polymer coating against degradation to a greater extent than if unmodified graphene was used. The performance of the nanocomposite coating was assessed by exposing it to UV light and salt fog for different time spans. The specimens were alternatively placed in the corrosion and UV chamber in intervals of 24 hours for 20 days. The coating performance analyses were carried out using atomic force microscopy, Fourier transform infrared spectrometer, thickness measurements, water contact angle, and electro-chemical impedance spectroscopy testing. It was found that after 20 days' exposure to UV and salt fog degradation, a 17.15% reduction in coating thickness is observed for coating containing silanized graphene, while for coating with unmodified graphene a 20.60% reduction is seen. Contact angle values showed that in the case of silanized graphene, the addition of a higher percentage of the nanoadditives significantly improved the performance of the coating, while for unmodified graphene up to 6% can be added to the coating to see improvement. EIS studies showed that nanocomposite coatings containing unmodified graphene had a higher corrosion rate (38.71E-06 mpy), and a lower impedance value (75,040 ohms) than nanocomposite coatings containing silanized graphene boasting a corrosion rate of 12.11E-06 mpy and an impedance value of 140,000 ohms, hence confirming the positive effects of silanization of graphene.