Failure Mode
Structural failure in multi-layer packaging substrates occurs when the cohesive or adhesive bonds between the barrier foil and the polymer web separate. This separation, known as barrier laminate delamination, compromises the protective barrier by allowing moisture or oxygen to penetrate the package. The loss of adhesion typically happens due to chemical incompatibility, inadequate adhesive curing, or external stress during thermal processing.
When the layers detach, the structural integrity of the pouch or carton is lost, which makes the package unusable for food or pharmaceutical applications. This defect occurs either during post-lamination storage or after exposure to vacuum testing.
Physical Mechanism
Adhesion failure occurs when environmental stressors or chemical agents attack the adhesive layer. High temperature or humidity accelerates this degradation, which destabilizes the polymeric bonds at the interface. During sterilization, thermal expansion differences between the metal foil and plastic films create shear stress.
This shear stress exceeds the bond strength of the cured adhesive, leading to separation.
Production Impact
Degradation of the packaging barrier shortens the product shelf life and causes product spoilage. On filling lines, the mechanical stress of sealing can trigger immediate splitting of the layers, which stops the production run. Preventing this defect requires careful monitoring of adhesive application weight and web tension during the lamination process.
