Meaning
Mass transfer events occur when substances migrate through a protective layer into a sensitive medium. functional barrier penetration describes the point at which contaminants from recycled resin or external sources bypass a virgin polymer layer to reach food contact surfaces, defining the limit where a multilayer structure no longer ensures safety.
Diffusion Rate
Migrants move through the polymer matrix at a speed determined by the size of the molecule and the crystallinity of the plastic. Smaller molecules like solvents or monomers pass through amorphous regions more easily than through tightly packed crystalline structures. Higher temperatures accelerate this movement by increasing the free volume between polymer chains.
Layer Integrity
Barrier effectiveness depends on the thickness and the chemical nature of the protective skin. A layer of virgin polyethylene must be thick enough to delay the arrival of contaminants for the entire shelf life of the product. Any pinhole or thinning in the layer during the blow molding process creates a shortcut for migration.
Safety Compliance
Testing protocols use specific stimulants to measure how much material crosses the barrier over time. Regulatory bodies set strict limits on the concentration of non-intentionally added substances allowed to reach the product. If the penetration level exceeds these limits, the packaging fails to meet the requirements for food contact.
