IMPROVING PAPER BARRIERS WITH CATIONIC NANOCELLULOSE AND 2D SILICATE COATINGS

Food packaging plays a crucial role in modern society as it is essential for the safe consumption and distribution of products.¹ Paper usage in packaging is an environmentally friendly alternative to conventional plastics, as it is a biodegradable and recyclable material. However, paper has low barrier properties to oil, gases, and water vapor, which limits its use.² In this study, we propose to improve paper barrier properties by the application of coatings based on cationic cellulose nanofibrils (cCNF) and lamellar silicates bentonite (B) and kaolin (K), natural materials widely available in nature. To obtain cCNF, a chemical modification introduced groups with positive charges into the cellulose structure, followed by microfluidization to reduce the fibrils to a nanometric scale. Silicates were dispersed in water and mixed with the cCNF suspension in different proportions. cCNF+B or cCNF+K mixtures were applied on cardstock substrates with a bar coater. Scanning electron microscopy images revealed the presence of discontinuous films on the substrates and changes in the paper's porosity after applying the coatings. The permeability of the samples was evaluated using the water vapor transmission rate (WVTR) test. The control group had a WVTR of 753±6 g day⁻¹ m⁻², while the control+water (CW) group showed 806±7 g day⁻¹ m⁻². Papers coated with cCNF+B and cCNF+K reduced WVTR by 5% and 4%, respectively, compared to the CW group. Oil and grease resistance tests demonstrated that samples with cCNF+B significantly enhanced this barrier property. Research is currently being conducted to examine the oxygen transmission rate of coated samples and to elucidate the interactions between cCNF and silicates. The goal is to develop methods that enhance the resistance of paper, particularly in relation to water. 

1. D. Nath et al. Food Packaging and Shelf Life 2022, 31, 100803.  
2. J. Zhang et al. ACS Applied Polymer Materials 2023, 5 (7), 5696-5706.