High Barrier Sustainable Paper Coating Based on Engineered Polysaccharides and Natural Rubber

The demand for paper-based packaging solutions as an alternative to incumbent single-use petroleum-based polymers for food packaging applications is ever-increasing. Paper-based packaging enables direct options for recycling and, in the case of inadvertent leakage, avoids the formation of microplastics through natural biodegradation. However, typical paper-based formats do not offer sufficient barrier performance which meets these sustainability objectives. Replacement of the plastic film with paper formats will reduce product shelf-stability and increase food wastage from farm to table. This work employed enzymatically polymerized microcrystalline glucan (MCG) as a functional additive in natural rubber (NR)-based coating formulations. Typically, NR coating formulations containing 0-50 wt % MCG were fabricated at a constant coating thickness with a constant solid content. The influence of the MCG on the wet and dry strength, rheology, adhesion strength, and barrier properties such as moisture, oxygen, and grease barrier of the formulated coatings was investigated. Also, further study on the effect of solid content and light crosslinking on the barrier properties was conducted. The optimized NR/MCG coating displayed promising mechanical properties as well as oxygen and oil barrier properties. Furthermore, light crosslinking of the NR/MCG coating enhances the barrier properties of the paper coating. Overall, the formulated NR/MCG paper coatings exhibited excellent wet strength in conjuncture with outstanding barrier properties, indicating their potential as a sustainable alternative in the food packaging industry.