Development of bio-based coatings incorporating microfibrillated cellulose, lignin and ionomer dispersions for food contact applications

The study aims at developing a bio-based coating to improve barrier properties of paper by combining microfibrillated cellulose and lignin, which can act synergistically, and adding a low level of ionomeric thermoplastic dispersion to further enhance processability and impart sealability. Coatings based on microfibrillated cellulose and lignin, at different concentrations and compatibilized with a polyelectrolyte, were applied directly on paper or after incorporation in the ionomeric resin. The effect of starch and calendering after coating was tested. The samples were characterised for barrier, surface, optical and physic-mechanical properties. Microfibrillated cellulose significantly increased the air barrier (up to 70%), and oil absorption decreased from 24 to 4 g m⁻². The addition of lignin compromised such functional properties, and the improvement was more limited. This also holds true for the combination of ionomer with microfibrillated cellulose. Unlike lignin, starch was seen to induce better barrier properties. The surface morphology also suggests microfibrillated cellulose coatings as more compact and uniform. Incorporation of starch significantly decreased the Young's modulus of the coated paper. Other components of the coatings did not cause a high impact on the mechanical properties. The results are promising, but a multilayer strategy instead of blending the components must be further tested.