The wide usage of petroleum-based plastic products over the last five decades has created an irreplaceable and unrecoverable impact on the planet. Therefore, developing green, sustainable, and high-performance cellulose-based paper materials to replace plastics in thin film packaging applications is both promising and essential. Herein, a novel starch-cellulose nanofibril multilayer coated paper with excellent oxygen and improved water barrier properties was developed. The aim of this work was to use the cheaper starch as a base layer to fill in the porous structure in paper materials, thereby reducing the amount of functional TEMPO-oxidized cellulose nanofibrils (TCNFs) required. To this end, the effects of viscosity and surface tension of coating solutions with different plasticizers on the roughness of coated paper were explored. The results show that low viscosity and surface tension contributed to reduced roughness. As a result, the coating weight of TCNF was reduced from 9.4±0.9 g/m² to 3.1±0.4 g/m² while maintaining its functionality when the starch layer coating weight was 10.9 ±1.2 g/m². Notably, the addition of starch also aids in reducing WVTR (50% reduction) and creates a composite system that maintains a functional oxygen barrier at high humidity (33.3 cm³ m^-2 day^-1at 80% RH and 23 degree) when compared to TCNF alone (130.6 cm³ m^-2 day^-1at 80% RH and 23 degree). This indicates that the starch-TCNF multilayer coating significantly improves the water and oxygen barrier properties at high RH, making a breakthrough in this field. This study provides a new, sustainable, and versatile approach for the large-scale production of fully bio-based, recyclable, and biodegradable paper materials, offering highly promising applications in the food packaging industry.

Nicole Sark

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