The Effect of High Lignin Content on Oxidative Nanofibrillation of Wood Cell Wall

Abstract

Wood from field-grown poplars with different genotypes and varying lignin content (17.4 wt % to 30.0 wt %) were subjected to one-pot 2,2,6,6-Tetramethylpiperidin-1-yl)oxyl catalyzed oxidation and high-pressure homogenization in order to investigate nanofibrillation following simultaneous delignification and cellulose oxidation. When comparing low and high lignin wood it was found that the high lignin wood was more easily fibrillated as indicated by a higher nanofibril yield (68% and 45%) and suspension viscosity (27 and 15 mPa·s). The nanofibrils were monodisperse with diameter ranging between 1.2 and 2.0 nm as measured using atomic force microscopy. Slightly less cellulose oxidation (0.44 and 0.68 mmol·g−1) together with a reduced process yield (36% and 44%) was also found which showed that the removal of a larger amount of lignin increased the efficiency of the homogenization step despite slightly reduced oxidation of the nanofibril surfaces. The surface area of oxidized high lignin wood was also higher than low lignin wood (114 m2·g−1 and 76 m2·g−1) which implicates porosity as a factor that can influence cellulose nanofibril isolation from wood in a beneficial manner.

Mechanisms of Cellulose Fiber Comminution to Nanocellulose by Hyper Inertia Flows

“…The basis of our CM-fibers was dissolving pulp, basically free of hemicelluloses and lignin. Fibrillation toward cellulose nanofibrils was also reported for holocellulose , and lignin-containing wood-fibers, , where a higher lignin content benefited the fibrillation. In the context of bending delamination, lignin can be considered as a matrix in which the cellulose fibrils are embedded as structural beams (illustration of Figure c, where the interface in blue can be of any nature).…”

“…In the context of bending delamination, lignin can be considered as a matrix in which the cellulose fibrils are embedded as structural beams (illustration of Figure c, where the interface in blue can be of any nature). Although an unorthodox description, it allows a mechanical reasoning why a higher lignin content resulted to easier fibrillation and thinner fibrils; plastic deformation is achieved at lower load for a higher lignin content, and delamination is hence expected to be achieved at lower forcing, i.e., weaker bending.…”

Advanced Nanocellulose-Based Materials: Production, Properties, and Applications

“…In fact, wood from poplar trees with high lignin content (30.0 wt.%) was more easily fibrillated as revealed by the higher nanofibril yield (68% and 45%) and suspension viscosity (27 and 15 mPa•s) than low lignin wood (17.4 and 19.7 wt.%). Moreover, the surface area (114 m 2 •g −1 ) and pore size (5.0 nm) of the oxidized high lignin wood were higher than those of low lignin wood (76 m 2 •g −1 and 4.4 nm, respectively), which means that porosity is a factor that can also beneficially impact the isolation of CNFs from wood [12].…”

“…In the domain of CNFs, and as highlighted in the research by Jonasson et al [12], the lignin content influenced the one-pot direct TEMPO-oxidative ) nanofibrillation of wood cell wall. In fact, wood from poplar trees with high lignin content (30.0 wt.%) was more easily fibrillated as revealed by the higher nanofibril yield (68% and 45%) and suspension viscosity (27 and 15 mPa•s) than low lignin wood (17.4 and 19.7 wt.%).…”

“…This Special Issue of Nanomaterials entitled Advanced Nanocellulose-Based Materials: Production, Properties, and Applications, brings together a compilation of original research and review contributions from world-leading scientists working with nanocellulose. Hence, this Special Issue contains a collection of one review paper about the characterization of cellulose nanomaterials [8] and eight research papers focused on the use of BNC [9][10][11], CNFs [12][13][14][15], and CNCs [16] as reinforcements in composites [13][14][15] and to produce ion-exchange membranes for fuel cells [9], patches for tissue engineering and wound healing [10,11], and nanosystems or nanocarriers for cancer treatment [15,16].…”