Barrier, converting, and tray-forming properties of paperboard packaging materials coated with waterborne dispersions

In this work, different food-contact experimental and commercial aqueous polymeric dispersions were applied to paperboard via rod coating technology to achieve <5% non-cellulosic content. Barrier (water, moisture and grease), mechanical (tensile and bending) and converting (heat-sealing and creasing) properties were analysed before tray formation trials on pilot-scale equipment. Dispersion-coated samples were compared against polyethylene terephthalate (PET) extrusion-coated paperboard, the principal industrial material used for food trays. Results show that, within the investigated properties, waterborne dispersions can achieve similar barrier properties compared with PET, yet at lower dry coat grammage (12 g/m² vs. 40 g/m² of PET-coated paperboard). Additionally, the investigated coatings heat-sealed at temperatures as low as 80–90°C, almost 100°C less than PET; however, lower seal forces could be achieved (15–20 N/(25 mm) vs. 23 N/(25 mm) of PET-coated paperboard). Paperboard delamination occurred at the highest seal forces. Dispersion-coated trays were obtained at 4.5–5.0% blank moisture content. Formed trays at industrial processing parameters showed critical coating damage during converting due to tensile stresses. This work shows that milder processing conditions allow a reduction in coat defects.