Use of carbonated cellulose micro/nanofibrils in the coating of sack kraft paper

Coating paper with cellulose micro/nanofibrils (CMF/CNF) can improve the performance of paper packaging. However, the cost of the process is high due to the significant energy consumption during the CMF/CNF production process, which can be reduced through pre-treatment of cellulosic fibers. The objective of this work was, therefore, to evaluate the performance of CMF/CNF subjected to accelerated carbonation with different concentrations of calcium hydroxide (5% and 10% m/m) as a paper coating for packaging production in terms of spreading properties of adhesives, air permeability, and water absorption. The CMF/CNF coating was able to fill pores contained in the papers, with the treatment with 10% carbonation (CMF/CNF 10%) being the one that adhered best to the surface. There was a reduction in surface roughness from 1.35 ± 0.53 μm (uncoated paper) to 0.72 ± 0.21 μm (CMF/CNF 10%). Similarly, air permeability in the coated treatments was decreased, indicating good barrier properties and possible CO₂ absorption activity in the carbonated samples. Coated papers showed greater spreading of water, PVA, and PVOH. On the other hand, the Cobb value dropped from 41.55 ± 3.83 g m² (uncoated paper) to 26.26 ± 2.36 g m² (CMF/CNF 10%). CMF/CNF subjected to pre-treatment with accelerated carbonation have the potential for use as a coating material, being recommended for applications in food packaging and those that will be subjected to gluing/coating processes with other materials.