Junichi Kitagawa

Effect of the Surface Free Energy of the Film Laminated Steel Sheet on Content Release Properties

Polyethylene terephthalate (PET) film laminated steel sheets, which have excellent properties of formability, corrosion resistance, and adhesion to steel sheets, have become widely used for beverage cans. To expand their application, we have sought to develop a new PET film laminated steel sheet for use in food cans. For this application, content release properties are necessary to ease removal of can contents. However, PET film laminated steel sheets have extremely poor content release properties. Prior investigations of properties have revealed dependence on the strength of adhesion between films and contents. The surface free energy of PET films has been inferred as the main factor. Using films with widely diverse surface free energy values, we studied the surface free energy effects on the properties of the materials contacting the cans. Results show that the properties are closely related to the surface free energy of the material and that the materials with surface free energy of less than 23 (mN/m) or more than 44 (mN/m) show excellent properties. Content release properties can be expressed as a function of adhesion in water between the material and protein. Reducing adhesion can significantly improve content release properties.