Single-step coating of cellulose nanofibrils on paper for sustainable food packaging

Cellulose nanofibrils (CNFs) offer impressive barriers against oil, grease, and gas when applied as a layer on paper or as a standalone film; however, coating CNFs onto paper with conventional equipment at useful coat weights in a single step is not currently possible. Here, we present a method to coat CNFs onto paper using an easily scalable vacuum-assisted approach which removes the water-rich layer that forms at the interface during the coating process. With the water layer removed, coat weights of 12–28 g CNFs/m² are achievable in a single step, depending on parameters including vacuum strength and initial cellulose concentration. The CNF-coated paper was found to nearly eliminate air permeability, reduce water uptake, and provide a high degree of resistance to oil, even after folding. This work opens the door for industrial-scale manufacture of CNF coated paper that can displace plastics in some food packaging applications.