Cross Border Polymer Migration Testing Standard Parameters
Cross-border polymer migration compliance requires testing finished articles under verified worst-case simulants, contact times, and surface-to-volume ratios.
Third Exposure Rule
Meaning
Standardized regulatory conditions for testing reusable plastic articles require that the compliance limits are met on the final phase of a multi-step extraction test. In migration testing for repeat-use items, the third exposure rule dictates that the concentration of chemical substances in the third extract must not exceed the specified migration limit. This rule applies to kitchenware, cups, and food-processing equipment made from polymers.
It ensures that the plastic continues to be safe for food contact after multiple washes and uses.
Testing Sequence
The plastic sample is exposed to three fresh portions of food simulant in succession under identical time and temperature conditions. The first two extracts are discarded or analyzed for research, while only the third extract is used to determine compliance. This simulates the long-term behavior of the product.
Migration Behavior
For most plastics, the migration of additives and monomers decreases with each successive exposure. If the migration increases instead, it indicates that the polymer is degrading or that the additives are highly mobile. This increase in migration would result in a compliance failure.
Molding Consideration
To pass this test, the molding process must be optimized to ensure complete polymerization and cure. Residual monomer must be minimized, and additives must be selected for their resistance to leaching. Improper molding conditions can lead to premature degradation and failure.