Dynamic Z Direction Tensile Stress Propagation in Recycled Fibers during High Speed Creasing
High speed creasing generates Z-direction tensile stress waves that fracture short recycled fibers unless matrix clearance absorbs elastic strain energy.
PET Lamination
Barrier Coating
Application of a thin layer of polyethylene terephthalate film to a paperboard substrate provides an effective moisture, grease, and chemical barrier for protective packaging. This PET lamination is commonly used for liquid packaging cartons, bakery trays, and cosmetics boxes where barrier properties and gloss are required. The resulting composite combines the structural stiffness of the paperboard with the chemical resistance of the polymer.
Package Protection
Adhesion between the film and the board must withstand subsequent converting processes like die-cutting, folding, and gluing. Heat and pressure are applied during lamination to ensure a uniform bond across the entire surface of the sheet. If the bonding is weak, the film may peel away at the cut edges, exposing the paperboard to moisture or oils.
Constant monitoring of surface tension and adhesive application rates prevents these adhesion failures. The thickness of the polymer layer must be kept uniform to avoid curling of the laminated sheet.
Recyclability Impact
Environmental considerations have led to advanced recovery methods to separate the plastic film from the underlying cellulose fibers. During repulping, the board is agitated in water, and the paper fibers dissolve while the film remains intact. Special screens then separate the plastic residue from the pulp.