Surface modification of aramid fiber with acrylic acid assisted by supercritical carbon dioxide

Aramid fiber (AF) has a limited application as reinforced composite due to its smooth and inert surface properties. To improve the interfacial properties of AF in reinforced composite applications, we developed a surface modification of AF using acrylic acid (AA) in supercritical carbon dioxide (scCO2). In this study, scCO2 was adopted as an alternative to conventional organic solvents in the modified reaction media. AA was then introduced onto the surface of AF by free radical grafting polymerization using scCO2. The modified AF observed by scanning electron microscopy had a rough surface with a dense polymer coating. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis revealed that the AF surface was decorated by –COOH groups through covalent bonding (C–N). The interfacial shear strength as a fiber-matrix interfacial property was increased by 53.4 % while effectively maintaining the strength of AF after surface modification.