Permeation Resistance
The protective layer applied to paper substrates to impede the transmission of moisture through the packaging defines a critical component in food preservation. This water vapor transport barrier prevents dry products from absorbing ambient moisture, while also keeping moist products from drying out. It is created using polymer films or wax coatings.
Barrier Mechanism
Performance of the protection layer depends on the density and molecular structure of the applied barrier material. Polyethylene and cyclic olefin copolymers are commonly used because their hydrophobic nature and tight molecular packing provide high resistance to water molecule diffusion. Pinholes, scratches or cracks in the coating layer can create pathways for moisture to bypass the barrier, significantly reducing its effectiveness.
Maintaining a uniform coating weight across the entire width of the web during the extrusion or coating process is essential to ensure consistent protection.
Performance Testing
Verifying the performance of these barriers is carried out by measuring the rate of moisture transmission under controlled temperature and humidity conditions. High-performance barrier boards are essential for products with long shelf lives or those distributed in tropical climates where high humidity accelerates degradation. Selecting the correct barrier level allows packaging designers to optimize the packaging weight while ensuring the product remains fresh.
