Barrier Verification
A standardized testing procedure detects pinholes and surface defects in the polymer coatings applied to liquid packaging board. Defined by the EN 13676 dye test, this method involves applying a colored solution to the plastic-coated side of the paperboard to see if it penetrates the substrate. A visible stain on the cardboard backing confirms that the protective barrier has been compromised, highlighting areas where liquid could seep through.
Chemical Application
Testing requires a specific solution containing a dye and a wetting agent, which is brushed or poured onto the coated surface. This mixture sits for a designated duration before being wiped away to reveal any penetration points. Testers then examine the reverse side of the board or the board’s cross-section to locate dye pathways.
Quality Assurance
Maintaining a perfect polymer barrier is essential for liquid-tight cartons that hold milk or juice. If the barrier has defects, the packaged liquid will soften the paperboard, causing the carton to fail on the retail shelf. Packaging converters run this analysis at regular intervals during co-extrusion coating to verify that extruder temperatures, line speeds, and resin distributions are optimized to yield a continuous, defect-free polymer film that protects both the product and the carton’s structural integrity.
