Investigating the Convertibility and Barrier Performance of a Novel Suberin Dispersion Coating During the Paperboard Creasing Process

Packaging plastics are being substituted by more sustainable materials to satisfy modern-life requirements. For example, utilisation of biocoated paperboards for packaging is one of the options; however, certain challenges exist in maintaining the integrity of the coated surface. In this study, the barrier formation and convertibility properties of a novel suberin dispersion coating were examined and compared with those of six commercial coatings by measuring their oil and grease resistance and using scanning electron microscopy (SEM) before and after creasing. Even before creasing, SEM revealed deep cavities on the coated surfaces, with the potential to impair the material barrier properties. Furthermore, finite element modelling provided evidence that creasing stresses emerged under the rules and in nearby areas. These outer stresses with internal fibre structure realignment caused the formation of surface defects such as grazes, microcracks and coating ruptures. The deepest defects, which critically reduce the barrier properties, were oriented parallel to the machine direction of the materials. In contrast, the cross-machine direction-oriented defects were bridged by the substrate fibres and did not penetrate that deeply into the coating thickness. The amount and severity of the surface damage revealed by SEM were correlated with the actual oil resistance measured for each material. The results indicate that the suberin dispersion exhibits promising barrier performance as a paperboard coating but requires further development to enhance its resistance to the conversion stresses.