RENEWABLE PAPER COATING BASED ON CATIONIC CELLULOSE NANOFIBERS AND NATURAL RUBBER LATEX

The development of packaging using renewable and biodegradable materials is urgently demanded to reduce environmental issues caused by plastics. The combination of natural rubber latex (NRL) and cellulose nanofibers (CNFs) are promising alternatives since CNFs have excellent barrier properties to oxygen and oil, while NRL substantially reduces water vapor transmission. In this work, cationic CNF (0.5 wt.%) and NRL (50 wt.%) dispersions were spread on paper as multilayer coatings by the standard tape-casting method, and the barrier against water vapor (WVTR at 23°C and 50% RH) and grease were evaluated as a function of deposited layers. The CNF/NRL coating with five alternate layers (CNF/NRL/CNF/NRL/CNF) reduced ca 300% the paper´s water vapor transmission rate (from 257 to 59 g/m2/24h). The resistance to oil and grease reached kit rating 12, i.e., the higher barrier level. Besides, the outer cationic CNF layer must confer antimicrobial activity to the coating due to the positively charged groups, this is a relevant property for food packing and will soon be evaluated. Overall, this study indicated that the CNF/NRL coating layers present competitive barrier properties while providing a renewable potential to be recycled with paper.