A Coating Change That Invalidates a Food Contact Declaration
A raw material shift in barrier coatings alters chemical migration profiles, instantly invalidating food contact declarations and risking complete job quarantine.
Pinholing Defects
Coating Imperfection
Microscopic voids in a continuous coating layer expose the underlying paperboard substrate to the environment. These gaps allow liquids and gases to bypass the protective barrier, compromising the function of the package. In the production of barrier boards, pinholing defects are a primary cause of quality rejection because they directly reduce the shelf life of packaged food.
Defect Cause
During the coating process, pinholing defects occur when air bubbles or dust particles disrupt the wet polymer layer. Poor wetting of the board surface can also cause the liquid coating to pull away from certain spots, leaving them unprotected. Regular maintenance of the coating equipment and filtration of the coating slurry are necessary steps to minimize these occurrences on the paper machine.
Performance Failure
Measuring the integrity of the barrier layer using dye penetration tests identifies these defects before the board is converted. In grease-resistant or liquid-packaging boards, even a small number of pinholes will cause the package to leak, leading to staining and loss of structural strength. Ensuring a continuous and defect-free barrier layer is therefore essential to maintain the protective performance of the paperboard during storage.
Quality control laboratories execute these tests on production samples to ensure that no compromised material reaches the high-speed filling line where such leaks would cause immediate downtime.