Barrier Layer
Polymer extruded barrier layers applied to paperboard substrates provide moisture, oil, and gas resistance required for food packaging applications. Extrusion of a polyethylene terephthalate coating creates a continuous thermoplastic film over bleached paperboard used in dual ovenable food trays and liquid packaging containers. The polymer layer protects paper fibers from fat migration and water vapor penetration during baking and frozen storage.
High adhesion strength between polymer melt and fiber matrix prevents delamination under extreme thermal changes.
Thermal Stability
Paperboard treated with melt extruded polyester maintains structural integrity across wide temperature ranges from freezing to oven baking above two hundred degrees Celsius. Excellent heat resistance enables food containers to undergo microwave and conventional oven heating without melting or leaching volatile compounds into food contents. The low pinhole density of extruded polyester layers maintains oxygen barrier properties that prolong shelf life for fatty food products.
Corona discharge treatment of the paperboard surface prior to extrusion optimizes polymer anchoring.
Recycling Limitation
Non soluble thermoplastic layers hinder conventional hydrapulping repulping processes by resisting fiber detachment in standard pulper vats. Specialized mechanical screening equipment must separate heavy plastic foil fragments from recovered pulp fibers to prevent sheet defects on recycled paperboard machines.
