Thermal and mechanical durability of starch-based dual polymer coatings in the press forming of paperboard

The runnability and convertibility of biopolymer dispersion–coated paperboard were determined using a novel adjustable packaging line equipped with a tray-pressing mould. Commercial paperboard was dispersion barrier coated on the back-side using a dual polymer system containing both a synthetic and a renewable biopolymer, of which the latter was the main component in the dispersion. The effect of the addition of a high-aspect-ratio platy pigment and synthetic polymer on both the grease resistance and the convertibility of the product was evaluated in addition to the evaluation of runnability and crack resistance in tray pressing and die cutting. The addition of synthetic polymer into bio-based dispersion improved the elastic properties, plasticity and, subsequently, mechanical convertibility of the product. Moderate additions of the synthetic polymer provided improved grease resistance for the biopolymer coatings. It revealed that the addition of synthetic polymer was sufficient in providing improved barrier properties, although the chemical compatibility and process window for the convertibility need to be considered. In addition to mechanical stability, the heat stability of the substrate needs to be investigated. Copyright © 2013 John Wiley & Sons, Ltd.