Cellulosic nanofibril and nanoclay as coating on paper substrate for packaging

Abstract

The objective of this work was evaluate the effects of cellulose nanofibrils (CNF) and nanoclay (NC) spray coating on basis weight, thickness, tensile strength, water vapor transmission rate (WVTR), and wettability of the coated papers. Suspensions of CNF and a mixture of CNF and NC (CNF/NC) were sprayed on a 60 g/m² extensible kraft paper surface as base substrate. Coated papers were oven dried at 100±5°C for 3 h. Coated papers with addiction of 60g/m² of CNF/NC with 5 layers (L5), 40 g/m² of CNF/NC with 4 layers (L4), 30g/m² with CNF/NC in 3 layers (L3) and 10g/m² of CNF with 1 Layer (L2) was produced and compared with uncoated 60 g/m² (C60) , 80 g/m² (C80) and 120 g/m² (C120) papers. Scanning electron microscopy images showed that the application of layers of cellulosic nanofibrils and nanoaclay contributed to the reduction of the WVTR (4%; 17%; 14% and 14% of WVTR decrease to L2, L3, L4 and C60, respectively), however contact angle results showed a wettability increase of CNF (4%) and CNF/NC(1%) coated surface with C60. When compared with C60, all treatments presented decrease of tensile strength. However, when compared with C120, it was observed a increase of 66% of tensile strength for L2, 44% for L3, a decrease of 18% for L5. L4 reached ate the same value of tensile strength divided by basis weight than C120. L2 and L3 achieved highest values of elastic modulus, was observed a increase of 56% and 38%, when compared with C60, for L2 and L3 respectively, while it was observed 7% of decrease for L4 and 30% for L5. Also was observed a elongation at break decrease (60%; 50%; 50% and 40% to L2, L3, L4 and L5, respectively) in comparison with uncoated paper references. Thus mechanical and barrier results demonstrate the effectiveness of CNF and NC use as coating for paper to confection of multilayer package.