Coating peeling / poor adhesion

The coating separates from the substrate in sheets or adhesion tests (such as peel force, cross-cut method) fail standards, with coating edges lifting or large-area detachment. Poor adhesion is the most fatal defect of coated products — even if the coating itself has excellent performance, poor bonding with the substrate means losing all function. Insufficient adhesion is quickly exposed in subsequent processing (laminating, die-cutting) and use (bending, heating), causing product scrapping.

1. Process parameter factors: Poor substrate surface treatment (insufficient corona treatment, low surface tension). 2. Material/formulation factors: Substrate surface contamination (release agent, oil, dust). 3. Material/formulation factors: Poor wettability between coating liquid and substrate surface. 4. Comprehensive factors: Improper curing process not achieving optimal crosslinking.

1. Process parameter optimization and adjustment: Test and increase substrate surface tension (e.g., corona treat PE film to 38-42 dyn/cm). 2. Mold/tooling improvement and maintenance: Clean the substrate surface. 3. Equipment inspection and system maintenance: Add appropriate wetting agent to the coating liquid. 4. Material/formulation optimization: Optimize curing temperature and line speed to ensure full crosslinking. 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 5Why analysis to trace the root cause, and solidify 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.

The essence of poor coating adhesion is insufficient intermolecular bonding force at the coating-substrate interface. The core solution approach is "surface activation + interface matching": increase substrate surface tension through corona/plasma treatment, select coating liquid systems compatible with the substrate, and ensure sufficient curing to complete interfacial chemical bonding.