Natural rubber, cellulose micro/nanofibrils and carnauba wax: renewable and low-cost coatings improving the barrier properties in papers

In the search for packaging that causes lower environmental damage, paper has been widely targeted to increase its use in the packaging industries. Still, the water and oil barrier characteristics need to be improved. To correct such deficiencies, different formulations of natural rubber incorporated with cellulose micro/nanofibrils, and carnauba wax were evaluated as alternative coatings of renewable and biodegradable origin on kraftliner and paperboard in the oil and water barrier properties at different grammage (5, 10 and 15 g/m²). The contact angle showed the hydrophobic characteristics of coated papers with angle values of 105° for rubber coatings with micro/nanofibrils and the stability of the water drop with the evaluation of wettability with values close to zero (0.01°/s). The results of Cobb 120 confirmed the hydrophobicity of the coated papers with values close to zero and close to those found by the polyacrylate varnish and the reduction of water vapor permeation by up to 65%. In addition to decreased affinity for water, the papers were also resistant to oil, reaching the maximum resistance value (kit-oil n° 12). Because of these results, natural rubber presents itself as a possible substitute for synthetic materials for covering papers and, together with the micro/nanofibrils of cellulose and carnauba wax, can correct the barrier deficiencies of the papers.