Investigation of Coating Adhesion to Wax Added Film Laminated Steel Sheets by Surface Free Energy

Abstract

Wax-added films are used as exterior films of laminated steel sheets for severe can-forming use. However, one difficulty in using wax-added film laminated steel sheets is the decreased coating adhesion which accompanies wax addition. Therefore, wax addition effects on coating adhesion were investigated using the surface free energy. Results demonstrated that wax on the polyethylene terephthalate（PET）film surface decreases the dipole force component（γ^p）of the surface free energy. The decrease in γ^p of the laminated film decreases the work of adhesion between the film and the coating. X-Ray photoelectron spectroscopy analysis revealed that the decrease in γ^p is attributable to a decrease in the ester bonds of PET that occurs along with increase of the wax ratio on the film surface. Furthermore, the laminated steel sheet coating adhesion was found to be related to the work of adhesion between the film and the coating, suggesting that the decreased coating adhesion caused by wax addition is explainable by the decrease in γ^p of the laminated film caused by the increase of the wax ratio on the film surface.