Meaning
The capacity of a polymer layer to prevent the migration of chemical substances from outer layers into packaged goods is critical for ensuring product safety. When recycled plastics or unapproved inks are used, functional barrier efficacy measures the degree to which a primary contact layer restricts the transfer of these contaminants. A complete barrier prevents any detectable migration, while a partial barrier limits migration to a concentration below the legally defined threshold of toxicological concern.
This performance depends on the polymer’s thickness, crystallinity, and temperature.
Material Selection
Denser polymers with high crystallinity, such as polyethylene treasure or ethylene vinyl alcohol, are typically used as barrier layers. Low density polyethylene, by contrast, has a loose molecular structure that offers poor resistance to migration. Multi layer coextrusion is often used to combine a cheap structural layer with a thin barrier layer.
Testing Procedure
Evaluation involves placing a known concentration of a surrogate contaminant behind the barrier layer and monitoring its transfer over time. High performance liquid chromatography or gas chromatography is used to detect any trace substances that penetrate the barrier. The test is conducted at elevated temperatures to accelerate the process.
Defect Consequence
If the barrier layer is too thin or has pinholes, contaminants can leach into the product and cause off-flavors or chemical risks. This leads to product recalls, lost revenue, and damage to the brand’s reputation. Processors must monitor layer distribution during extrusion to prevent this failure.
