Effect of Overlapping Eco-Friendly Cellulose Nanofibrils and Nanoclay Layers on Mechanical and Barrier Properties of Spray-Coated Papers

This work proposes to evaluate the effect of spray-coating in papers using eco-friendly cellulose nanofibrils (CNFs) and nanoclay (NC) on mechanical and barrier properties for application as reinforced bags. Sack kraft papers of 60 g m-² (C60) were coated with CNFs + CNFs/NC in 4 layers (L5), 40 g m-² of CNFs + CNFs/NC in 3 layers (L4), 30 g m-² with CNFs/NC in 2 layers (L3) and 10 g m-² of CNFs in 1 layer (L2), and compared to uncoated sack kraft papers with basis weight of 60 g m-² (C60), 80 g m-² (C80) and 120 g m-² (C120). The coated papers L2; L3; L4 and L5 obtained a decrease in water vapor transmission rate (WVTR) of 3.5%; 17%; 14% and 14%, respectively, when compared to C60. Comparing L2 and L3, CNF layer induced lower contact angles on the coated paper than CNF/NC layer. When compared coated papers with C120, it was observed an increase of around 66% in tensile strength for L2, around 44% for L3, and decrease of ~ 18% for L5 coated papers. L4 achieved the same tensile strength (when divided by basis weight) than C120. L2 and L3 coated papers led to the highest values of Young’s modulus, with increase of 56% and 38%, respectively, when compared to C60. Spray-coating in the present conditions improved the mechanical and barrier properties of the coated papers, being a possible alternative to produce papers with lower basis weight and using renewable raw materials.