Grease, Oxygen, and Air Barrier Properties of Cellulose-Coated Copy Paper

Cellulose nanomaterials have been demonstrated to be excellent barriers against grease, oxygen, and other vapors, but their implementation in packaging materials is challenging because of numerous technical and practical challenges. In this work, the oxygen, air, grease, and heptane barrier performance of copy papers coated with cellulose nanocrystals (CNCs), oxidized cellulose nanofibrils (TOCNs), and carboxymethyl cellulose (CMC) weas examined. The effects of different materials and processing conditions were evaluated for their impacts on the resulting barrier properties. TOCN coatings demonstrated significantly better barrier properties than CNC and CMC coatings due to the long-range networked structure of TOCN suspensions eliciting enhanced film formation at the paper surface. Neat coatings of nanocellulose did not readily result in strong oxygen barriers, but the addition of CMC and/or an additional waterborne water barrier coating was found to result in oxygen barriers suitable for packaging applications (1 cm3/m2·day transmission at low humidity with a 10 g/m2 coating). Cast films and thick coatings of CMC were good barriers to oxygen, grease, and air, and its addition to cellulose nanomaterial suspensions aided the coating process and reduced coating defects. In all cases, the incorporation of additional processing aids or coatings was necessary to achieve suitable barrier properties. However, maintaining the strong barrier properties of nanocellulose coatings after creasing remains challenging.