What are the requirements for steel sheets intended for PVC film lamination?

Laminating PVC film onto steel sheets entails specific requirements for the substrate: Cold-rolled sheets, hot-dip galvanized sheets, or Al-Zn coated steel sheets with a thickness of 0.2–1.0 mm are preferred. The sheet surface must be flat and free from warping, oil, or rust, with residual surface stresses fully relieved to prevent deformation during subsequent shearing. The steel sheet must undergo cleaning and degreasing, followed by passivation using a zinc phosphate or iron phosphate solution to form a uniform base conversion coating; this significantly enhances adhesion between the PVC film and the steel, preventing issues such as blistering or delamination later on. A specialized thermoplastic polyester laminating adhesive must be used. The peel strength between the PVC film and the steel sheet must be ≥70 N/20 mm, and the adhesive must be suitable for a thermal lamination environment of approximately 200°C to ensure a secure, heat-fused bond during the hot-pressing process. The steel sheet must achieve an Erichsen cupping test value greater than 9 mm, demonstrating excellent resistance to deep drawing and bending, ensuring that the PVC film does not crack or delaminate during secondary stamping or bending operations.