Meaning
Demonstrating that a specific polymer layer prevents the migration of contaminants from recycled plastics into food-contact surfaces is a standard procedure in packaging engineering. This evaluation, known as functional barrier verification, confirms that a virgin polymer or high-barrier layer effectively blocks chemical transfer under intended use conditions. It ensures that post-consumer recycled resin can be safely used in multi-layer structures.
Barrier Mechanism
Polyethylene terephthalate and ethylene vinyl alcohol possess dense molecular structures that restrict the diffusion of organic molecules. This property prevents contaminants from migrating.
Testing Protocol
Verification involves spiking the recycled layer with surrogate contaminants of various molecular weights and polarities before co-extrusion. The finished multi-layer film is then subjected to migration testing to see if any of the spiked surrogates pass through the barrier. A barrier is verified if the concentration of migrants on the food-contact side remains below detection limits.
Process Control
Maintaining the continuous thickness of the barrier layer during co-extrusion is essential, as any thin spots or pinholes can compromise performance. Online thickness monitoring systems are used to verify uniformity across the entire film roll. Consistent layer distribution prevents localized migration failures and ensures that the final packaging complies with public health standards.
