Analyzing the acido-basicity of anodically treated carbon fibers using inverse gas chromatography at infinite dilution

Surface treatment is crucial for enhancing the performance of carbon fibers (CFs) within a matrix, necessitating a detailed examination of varying treatment effects on surface energetics. In this study, high-strength CFs (Toray T-300, 3 K fibers) underwent electrochemical treatment in a sodium hydroxide solution, applying increasing current densities to modify surface properties. The surface properties, including surface free energy and acid–base characteristics, were analyzed using inverse gas chromatography at infinite dilution. The results showed that weak acidic probes, such as carbon tetrachloride or chloroform, are ineffective for accurate assessment of acid–base properties of solid surfaces. Experimental data showed that all CF surfaces exhibited amphoteric behavior, with increased basicity under the experimental conditions. Increased current intensity of the electrochemical treatment from 90 to 300 mA enhanced surface acidity and basicity; however, no significant changes were observed beyond 300 mA. This suggested that a moderate treatment at 90 mA is optimal for achieving the desired acid–base properties, improving the integration of CFs into polar organic matrices and potentially enhancing efficient fiber-resin bonding.