Effect of fluorination of multiwalled carbon nanotubes (MWCNTs) on the surface properties of fouling-release silicone/MWCNTs coatings

Abstract

The characterisation of poly(dimethylsiloxane) (PDMS)-based fouling-release coatings filled with pristine and fluorinated multiwalled carbon nanotubes (MWCNTs) are reported. The fluorination of MWCNTs was performed via a three-step procedure, which consisted of oxidation in an acid mixture, reduction by diisobutylaluminium hydride and silanisation by (heptadecafluoro-1,1,2,2-tetrahydrodecyl)triethoxysilane. Characterisation of MWCNTs by Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy and thermogravimetric analyses showed the formation of functional groups in each step of the modification process. The coatings were prepared by filling the PDMS with pristine and fluorinated MWCNTs in three weight percentages (0.05, 0.1 and 0.2wt.%). The surface chemistry and structure of the coatings were studied using critical surface energy determination and atomic force microscopy. The results showed that both types of nanotubes led to changes in some surface properties of the coatings, even when present in low amounts. However, the measurements of mechanical properties via tensile tests showed that the modulus and tensile strength of the coatings did not change in the presence of either pristine or fluorinated MWCNTs. The effect of the presence of the fluorinated MWCNTs on the surface of the coatings improved the fouling-release properties by reducing the pseudobarnacle adhesion strength by 67% compared to that of the unfilled sample. The results also revealed a 47% decrease in the adhesion strength of pseudobarnacles on the coatings filled with the pristine MWCNTs.