Force Reduction
Gradual loss of the bond between two laminated layers over time results in the weakening of a package structure. This peel strength decay is often caused by the migration of additives such as slip agents or plasticizers from the film into the adhesive layer. It is a fundamental factor for flexible pouches used in long-term storage or those exposed to aggressive chemicals.
Laboratory aging tests use elevated temperatures to simulate months of shelf life in a matter of days.
Degradation Path
Environmental factors like humidity and heat accelerate the chemical breakdown of the interface. In a paper-to-film laminate, peel strength decay might occur if the adhesive absorbs moisture and undergoes hydrolysis, which cleaves the polymer chains. This process reduces the force required to separate the layers, potentially leading to the failure of the package seal under the weight of the product.
Monitoring the rate of this decline helps manufacturers set expiration dates for their packaging materials.
Shelf Limit
Finished products that show a rapid drop in adhesion are often the result of incompatible surface treatments or contaminated substrates. If the initial bond is high but the peel strength decay is steep, the cause is likely a physical change at the interface rather than a chemical failure of the adhesive. Regular testing of retain samples ensures that the bond remains within the safety margin for the entire life of the product.
