Cationic surfactant modified cellulose nanocrystals for corrosion protective nanocomposite surface coatings

Cellulose nanocrystals (CNCs), a robust renewable and green nanomaterial, has potential as an excellent reinforcing and multifunctional filler for polymers used in coating and other applications. However, the high polarity of CNCs limits its interfacial interaction and dispersibility with several non-polar polymers. These limitations severely constrain it from transferring its functional attributes to polymeric materials. In this paper, three differentiated cationic surfactants: cetyltetramethylammoniumbromide (CTAB, C16 single chain), dimethyldidodecylammonium bromide (DDAB, C12 double chains) and dimethyldihexadecylammonium (DHAB, C16 double chains) were used to modify the surface of CNCs. The modifications were confirmed using Fourier-Transform Infrared Spectroscopy (FTIR) and elemental analysis. X-ray diffraction (XRD) and thermogravimetric analysis (TGA) of the samples revealed that the crystallinities and the thermal stabilities of the modified CNCs were preserved. Corrosion protection studies of epoxy nanocomposites containing the native and surfactant modified CNCs were conducted using model steel specimens via salt spray and electrochemical test methods. The results reported herein indicated that the use of surfactant modified CNCs resulted in an enhanced dispersibility in the epoxy matrices as compared to native CNCs. The improved dispersion assisted in retardation of the penetration of electrolyte that caused a remarkable improvement in the metal corrosion protection performance, as compared to unfilled or native CNC filled epoxy coatings.