Vapor Resistance
Protective surface treatments are applied to paper and board to inhibit the transmission of water vapor through the fibrous structure. Creating an effective moisture barrier prevents the dry food inside a carton from absorbing ambient humidity, and conversely, prevents wet food from drying out. This protection is measured by the water vapor transmission rate under specified temperature and humidity conditions.
Choosing the right material ensures the packaged product achieves its intended shelf life.
Protective Coating
Packaging lines require that the protective layers remain intact through creasing, folding, and heat-sealing operations. A modern moisture barrier often consists of co-extruded polymers, water-based dispersions, or biodegradable biopolymers applied directly to the paperboard. These coatings must be flexible enough to bend around tight carton corners without micro-cracking.
If the barrier layer cracks, water vapor will penetrate the board, causing it to lose its stiffness and stackability. For this reason, converters test the cracked barrier under high-humidity conditions to simulate real-world transport and warehouse stresses.
Performance Standard
Recycling processes are complicated by thick plastic coatings that are difficult to separate from the paper fibers in standard repulping systems. Many mills are shifting toward water-based dispersion coatings that break down more easily during recycling. This transition balances the environmental demand for circular packaging with the technical requirement for product protection.
