Synergistic Multi‐Layer Renewable Barrier Coatings on Porous Packaging Materials Using Enhanced Anionic Cellulose‐Based Biopolymers and Chitosan

ABSTRACT In this work, we examine ways to advance sustainability in material packaging by applying scalable, dual‐layer coating techniques for generating thin biopolymer barrier films on paper substrates. Unbleached kraft paper and supercalendered glassine paper are used as substrates, and cellulose nanocrystals (CNC) and chitosan (CS) are used for coatings. CNC and CS are applied on the substrates using single‐layer (multi‐pass) or dual‐layer slot die coating on a roll‐to‐roll (R2R), with similar grammage coated under the same conditions. The effect of CNC suspension pH is also examined. Coated papers are characterized to determine oxygen permeability (OP) and water vapor transmission rate (WVTR) at 50% and 80% RH as well as mechanical properties. Single‐layer multi‐pass coated paper exhibits improved OP and WVTR compared to coated kraft paper. Glassine paper coated with a coat weight of 20.6 ± 1.0 g/m 2 of CNC at a suspension pH of 3 has the lowest OP value of 3.9 ± 1.0 cm 3 ·µm/m 2 /d/kPa. The use of dual‐layer slot die coating produces similar OP values at a large coat weight as single‐layer multi‐pass coating. We demonstrate the viability of scalable fabrication of multilayer renewable bioproducts for packaging by using processes amenable to sequential or simultaneous coating on a R2R.