Dispersion Barrier Performance under Crease Compression in Folding Boxboard
Wide matrix channels and shallow penetration depth prevent polymer micro-fractures in dispersion-coated folding boxboard during creasing.
Pinhole Generation
Void Formation
Creation of microscopic holes through a functional coating or film layer compromises the protective qualities of a packaging material. Pinhole generation often occurs during the drying process if air bubbles or solvent vapors escape too violently from the wet layer. These tiny apertures are often invisible to the naked eye but allow gases and liquids to bypass the barrier.
Production Variable
High viscosity in the coating can trap air that eventually pops and leaves a crater as the film sets. Contamination on the base sheet (such as oil or dust) can also prevent the coating from wetting the surface properly, leading to localized bare spots. Maintaining a clean environment and using de-foaming agents are standard practices to minimize these defects.
Variation in the coating application pressure can also force air into the liquid, which then expands under the heat of the infrared dryers.
Quality Assurance
Detecting these failures requires specialized testing like the turpentine test or electrical conductivity checks. A single pinhole in a foil laminate or a greaseproof coating can lead to product spoilage or unsightly oil stains on the outer carton. Ensuring a 100 percent solid film is the goal for any high barrier application.