Meaning
Multilayer packaging configurations incorporate specific material zones to prevent chemical migration into sensitive products. A layer acting as functional barriers prevents the migration of substances like plasticizers, solvents, and mineral oils from recycled paperboard or adhesive layers into food or medical products. This protection must remain effective under the specified storage conditions and across the expected shelf life of the product.
The term defines a performance-based standard rather than a specific material class.
Migration Control
Diffusion rates through different polymer layers dictate the effectiveness of the protection. High-density polymers with high crystallinity can function as functional barriers by slowing the movement of migrating chemical species. The thickness and temperature of the barrier layer are critical variables that determine the time it takes for a contaminant to break through.
Molders and extruders must ensure that the barrier layer is continuous and free of pinholes or thickness variations that would compromise its integrity.
Material Selection
Polymer chemistry determines which material is suited for a given barrier application. Common choices for functional barriers include ethylene vinyl alcohol, polyamides, and specialized polyester resins. These materials are often coextruded with polyolefins using tie layers to combine structural strength, moisture resistance, and chemical block properties.
Virgin polymers are typically placed on the food-contact side, while recycled materials or scraps are embedded behind the barrier layer to optimize costs.
Regulatory Standard
Compliance with international safety regulations requires rigorous testing of the multilayer structure. In polymer sourcing, specifying functional barriers involves documenting migration limits under simulated conditions of use. Agencies like the European Food Safety Authority and the United States Food and Drug Administration define testing protocols to verify that no harmful migration occurs.
This certification is necessary for recycled resin economics, as it allows the use of less expensive recycled polymers in close proximity to food products without risking contamination.
