Substrate Thermal Shrinkage/Deformation

The substrate shrinks or deforms after being heated in the coating curing oven. When this defect appears in coating-formed products, it is usually closely related to the coating head precision, the rheological properties of the coating liquid, the substrate surface condition, or the curing process conditions. The distribution characteristics of coating defects (transverse/longitudinal/random) provide important clues for diagnosing coating head and curing system problems. Continuous occurrence will cause the functional performance of the coating to fall below standard, and coordinated troubleshooting is required from three aspects: coating liquid formulation, coating equipment, and curing process.

1. Material/formulation factor: the curing temperature exceeds the heat resistance temperature or heat deflection temperature of the substrate. 2. Material/formulation factor: the substrate already has internal stress from the manufacturing process, which is released after heating. 3. Mold/tooling factor: when the substrate thickness is thin and the tension is large, it is elongated at high temperature and then set.

1. Process parameter optimization and adjustment: lower the curing temperature or increase the line speed to reduce the heating time. 2. Mold/tooling improvement and maintenance: use a substrate grade with better heat resistance. 3. Equipment inspection and system maintenance: preheat the substrate to release internal stress before coating. 4. Material/formulation optimization: control the substrate tension at a low level. 6. Preventive management: establish standardized process parameter cards and quality control limits for each mold/product, and regularly conduct process capability index (CPK) evaluations. For recurring problems, use fishbone diagrams or the 5Why analysis method to trace the root cause, and solidify the countermeasures as PFMEA control points. Establish a regular equipment maintenance system, and implement life management for key tooling such as dies/spinnerets/calender rolls/coating heads.

This problem is a typical manifestation of substrate thermal shrinkage/deformation in coating forming. The core of the solution lies in ensuring the substrate surface condition, optimizing the rheological properties of the coating liquid, and precisely controlling the curing process conditions. It is recommended to start from the two aspects of substrate and coating liquid, and gradually troubleshoot to the coating equipment and curing system.