Coating Continuity
Microscopic gaps in a protective layer allow gases or liquids to penetrate the barrier of a substrate. Pinholing often occurs when air bubbles become trapped during the liquid application phase or when the coating fails to wet the surface evenly. These interruptions in coverage reduce the barrier performance of packaging materials and lead to premature degradation of the contents.
Production Mechanism
Moisture trapped within the fibres vaporizes during the drying stage and forces a pathway through the hardening film. Excessive heating triggers this release too quickly for the coating to heal the resulting break. Low surface energy on the base sheet prevents the chemistry from spreading into a continuous film.
High solvent evaporation rates also contribute to the phenomenon by pulling the fluid away from small irregularities before solidification occurs. Proper control of drying temperatures and substrate tension prevents these defects from forming during high speed coating runs.
Performance Impact
Barrier integrity depends entirely on the absence of these voids across the entire surface area. Products stored in film with high porosity experience loss of shelf life because the oxygen transfer rate climbs disproportionately to the number of openings. Filling lines demand perfectly sealed substrates to maintain vacuum levels for sensitive goods.
A sheet with poor coat weight consistency fails under pressure testing even when the material thickness seems sufficient for the application. Defects in the coating layer compromise the commercial viability of high barrier flexible packaging.
