Meaning
Transport mechanisms describe the movement of gas or liquid molecules through tiny defects in a polymer film or protective coating. These microscopic apertures allow substances to bypass the molecular barrier of the resin, leading to contamination or loss of pressure. This defect is a common concern in high performance packaging.
Barrier Failure
Leakage through these small voids occurs at a much faster rate than normal molecular permeation. When pinhole diffusion is present, the shelf life of sensitive products decreases as oxygen or moisture enters the package. The physical size of the hole determines the volume of the bypass flow.
Film Integrity
Manufacturing variables like resin purity and extrusion temperature influence the frequency of these defects. Because pinhole diffusion often results from unmelts or inorganic contaminants in the raw material, filtration at the die is a critical control point. High stress during the stretching process of oriented films can also trigger the formation of these voids.
Leak Detection
Testing methods like vacuum decay or high voltage spark testing identify the location and size of the holes. Since many apertures are too small for visual inspection, automated sensing on the production line is necessary to maintain quality. This monitoring prevents the shipment of defective batches to the customer, ensuring that the final protective layer meets the exact performance requirements for long term storage.
