Dissolution and regeneration of cellulose from N-methylmorpholine N-oxide and fabrication of nanofibrillated cellulose
Résumé
Cellulose II nanofibers (R-CNFs) were isolated from Egyptian bleached bagasse pulp fibers via dissolution in N-methylmorpholine N-oxide (NMMO) and regeneration. The quality and features of the R-CNFs suspension were optically and morphologically characterized and compared to those obtained from two conventional CNFs prepared from pretreated native cellulose (enzymatic hydrolysis (E-CNFs) and TEMPO oxidation (T-CNFs)) isolated from the same cellulosic pulp. Optical microscopy images show the effectiveness of nanofibrillation for all samples with few residual fragments and the absence of macrofibers. The grinding process of R-CNFs results in the formation of CNFs in nanometer scale, as confirmed by AFM and TEM studies. Moreover, the nanopapers prepared from R-CNFs showed mechanical properties (tear resistance and Young’s modulus), porosity, and water vapor permeability comparable to those obtained for E-CNFs and T-CNFs. However, R-CNFs suspensions exhibited a lower optical transmittance value (7.5%) and a higher turbidity (315 NTU) against 12.5%, 272 NTU and 25%, 160 NTU for E-CNFs and T-CNFs, respectively ascribed to some CNFs aggregates. The quality index for E-CNFs and T-CNFs was 74.2 and 85.5, respectively, whereas it was only 68.3 for R-CNFs due to the presence of these few fibrillar aggregates after regeneration and fibrillation.