Meaning
Mass transfer processes cause the movement of low molecular weight compounds from plastic packaging materials into food or pharmaceuticals. This packaging migration involves the diffusion of residual monomers, plasticizers, or stabilizers through the polymer matrix to the contact surface. The rate of this movement is governed by temperature and contact time.
Minimizing this transfer is a primary design goal for food grade and medical grade plastics to ensure consumer safety and product purity.
Chemical Diffusion
Small molecules move through the free volume between polymer chains over time. This migration accelerates at higher temperatures or when the plastic is in contact with fatty or acidic substances that swell the polymer matrix. Choosing resins with higher crystallinity or lower diffusion coefficients can significantly reduce this chemical movement.
Regulatory Limit
Safety authorities establish maximum allowable concentrations for specific migrants in food and drugs. These limits are often measured in parts per million or parts per billion to prevent toxicological risks. Manufacturers must certify that their packaging does not exceed these values under worst case conditions of use.
Testing Protocol
Laboratory analysts use food simulants like ethanol or vegetable oil to measure the quantity of substances that leach out. These simulants are exposed to the plastic under controlled temperature and time profiles that replicate actual storage.
