Electropolymerization of acrylic acid on carbon fibers for improved epoxy/fiber adhesion

This study focuses on the electropolymerization of acrylic acid as a surface technology for carbon fibers. The deposition process of the polyacrylic acid is assisted by the co-deposition of Zn2+ ions. The structural properties and final characteristics in respect of adhesion and the barrier coating of the resulting deposited coatings were investigated by means of AFM, FT-IRRAS and XPS. The role of the Zn2+ and inhibitors in the electrolyte during the electropolymerization process was established. The electrodeposition mechanism of polyacrylic acid onto surfaces can be divided up into three steps. (1) A Zn(2+)AA complex is adsorbed on the surface and reduced to Zn. The electron excess in the vicinity of the interface consumes the inhibitor molecules present in the acrylic solution. (2) Once the inhibitor has been depleted, polymer activation and growth starts through the transfer of electrons from the Zn2+-AA complex. (3) The length of the PM chains increases until the supply of electrons from the surface is hindered. The chemical stability of the electropolymerized coating was proven by FT-IRRAS spectroscopy. Wet adhesion to the composite is examined by means of a peel test. The wet adhesion studies reveal a two-fold improvement in the adhesion factor when the PM is electropolymerized onto CFRP. (C) 2017 Elsevier B.V. All rights reserved.