Surface Modification of Carbon Nanotubes in Silicone–Polyurethane for Improved Mechanical and Anticorrosion Properties

Carbon nanotubes (CNT) were dispersed into homemade silicone–polyurethane (SPU) resin in order to enhance their mechanical and anticorrosion ability. Before mixing with SPU, CNT were modified by four different approaches to improve their dispersion in SPU, and the surface of CNT were covered by SiO2–TiO2 nanoparticles, -NH2 groups, epoxy groups or isocyanate groups, respectively. The structures of the modified CNTs were checked by XRD, FTIR, and SEM. After being dispersed in SPU to form a composite coating, the one with SiO2–TiO2 nanoparticles modified CNT exhibited the best mechanical properties and chemical resistance (low water absorption), and its corrosion current density (icorr) was only 9.246 × 10−9 A cm2, which is four orders of magnitude lower than the icorr value of the coating with unmodified CNT (1.599 × 10−5 A/cm2). This may be because the covered SiO2–TiO2 nanoparticle increased the roughness of the CNT surface, which can improve their dispersion in SPU resin.