Moisture Barrier
Extrusion-grade low-density polyethylene applied to a base of unbleached softwood pulp creates a composite material designed for heavy-duty containment. This poly-coated kraft protects contents from liquid seepage and environmental humidity while providing the structural integrity required for shipping industrial components or bulk food products. Barrier weight is typically specified in pounds per ream or grams per square meter to ensure the coating thickness aligns with the expected duration of exposure to damp conditions.
Production Mechanism
Converting lines utilize high-heat extrusion stations where the thermoplastic resin flows onto the moving web under precise tension. The roller nip temperature determines the mechanical bond strength between the paper fibres and the polymer film. Uniform cooling prevents the development of pinholes that allow moisture migration across the protective layer during long periods of static storage.
Quality control personnel measure the adhesion using standardized peel tests to confirm the polymer remains firmly anchored to the substrate despite handling stress.
Operational Performance
Sealing performance depends on the thermal sensitivity of the coating when subjected to heated crimping or ultrasonic welding. Fabricators utilize the heat-sealable nature of the outer layer to close sacks and wrap bundles without the application of additional adhesives. Excessive heat application causes the polymer to retract from the paper edges, which compromises the seal integrity and leaves the absorbent fibres vulnerable.
Standardized performance metrics confirm that the proper application of poly-coated kraft maintains a dry internal environment under fluctuating pressure conditions.
