The effect of electrically conducting carbon materials on the conductivity and morphology of poly(vinyl butyral) and chitosan blend composite for application in anti-corrosive coatings

Abstract

In this study, the morphology and conductivity of composites containing poly (vinyl butyral), poly (ethylene glycol), chitosan and electrically conducting carbon material (CCM), including mesoporous carbon (carbon meso), tergo (graphene) and graphite, were investigated. The aim is to determine if such composites are beneficial as coating materials as the electron conduction inhibits corrosion by limiting galvanic potentials. Given the combination of ingredients, nine samples were produced with CCM loading being the main variable. As a result, we find that the addition of any CCM in the blend increases its conductivity and at the same time affects its morphology. The blend modified with carbon meso has the highest conductivity and the blend modified with graphite has the lowest. This is attributed to the higher miscibility of the blend with carbon meso compared to tergo and graphite modified blends, which results in better dispersion in the polymer matrix and thus an improvement in the percolation path for electrons. As far as the morphology is concerned, partial miscibility was observed with the blend modified with tergo and graphite, while the morphology of the carbon meso blend composite is compatible. The hydrophilicity of the blend is improved by addition of just 1% of the carbon material, with carbon meso blend performing better than the tergo and graphite modified blend. A co-continuous morphology was observed with the blend modified with carbon meso, which may be ascribed to a favourable interaction between the polymers in the composition and influenced by the carbon material. The 3% carbon meso modified blend showed optimum performance and was upscaled for the corrosion studies. Visual analysis indicates that the degree of rust is decreased by 90% after the application of the composite on the mild steel substrate. This is confirmed by electrochemical analysis. The corrosion rate of the steel coated with the neat blend and composite achieves a protection efficiency of 30% and 44% respectively. Therefore, the blend composite provides a promising strategy to overcome the corrosion problem in the coating industry. The blend has potential to be used in many coatings applications.