Effect of the hemicellulose in the properties of nanopaper.

The foldable, low thermal expansion, and optically transparent are main properties of paper produced with cellulose nanofibers (nanopaper), being able to be used ifl the development of flexible circuit technologies. In this context, this work evaluates the importance of hemicellulose in the properties of nanofiber paper (NFP). The hemicellulose extraction from Pinus sp bleached cellulose pulp was performed with NaOH 17.5% for 1.5 h. Thereafter, the pulp was washed with 8.3% NaOH, then was add 10% acetic acid until neutralization, and washed with water. The nanofibrils were obtained by mechanical defibrillation in a Super Masscoloider Masuko Sangyo mill. The NFP with the grammage of 40 and 50 g/m2 were produced by filtration and drying under pressure. The extraction process reduced 80% of xylose, 40% of mannose and 40% of galactose compared of the bleached cellulosic pulp. The NFPs with around 15% of hemicellulose are homogeneous and transparent, the interstices between the fibers, observed by scanning electron microscopy, are small enough to avoid light scattering, making the cellulosic material transparent. The NFP of 40 and 50 g/m2 had a thickness of 45 J..Im,water absorption of 63 and 34 g/m2, respectively. They did not present air permeability. NFP of 40 and 50 g/m2 without hemicellulose had a thickness of 76 and 87 um, water absorption of 128 g/m2 and air permeability of 202 and 384 s/100 em", respectively. The spaces created by the coalescence of the cellulose nanofibrils after the extraction of the hemicellulose result in the dispersion of the light and consequently in the opacity of the NFP. Extraction of hemicellulose reduced the tensile and bursting strength by 80%. Therefore, hemicellulose acts as an inhibitor of the coalescence of microfibrils, providing adhesion and increase of the mechanical properties.