Abstract
Widely used for can stocks electrolytically chromium-coated steel (ECCS) laminated with biaxially oriented polyester films is usually subjected to heat treatment in a wet condition such as retort treatment in the filling process. This heat treatment is a factor that decreases the adhesive property for polyester film and ECCS.The effects of heat treatment in a wet condition on the adhesion of a polyethylene terephthalate (PET) film to ECCS were investigated in connection with the structural changes in the PET compared to the changes after annealing in a dry condition. The adhesivity was evaluated with T-peel tests, and the properties of the PET film were appraised using density measurements, X-ray diffraction, an infrared spectroscopic method, and molecular weight measurements.The adhesivity in both wet and dry annealing conditions decreased with the progress of crystallization and degradation at 90°C and 130°C, though it did not change at 50°C. Additionally, the adhesivity in a wet condition was worse than that in a dry condition because the hydrolysis of the PET in a wet condition progressed faster than the thermal degradation in a dry condition.
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