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The objective of the present work was to evaluate the use of Raman microspectroscopy analysis to assess changes in cellulose micro/nanofibril structure from fibers subjected to different pre-treatments. Pulp fibers were pre-treated with 5 wt% NaOH for 2 h, 10 wt% NaOH for 1 h, and endoglucanase-type enzymes to improve nanofibrilation. After the pre-treatments, the fibers were mechanically fibrillated to produce cellulose micro/nanofibrils, which were made into films to be analyzed. Fibers pre-treated with 5 wt% NaOH produced 59% micro/nanofibrils with average diameter less than 30 nm, for Eucalyptus, and 46% of micro/nanofibrils, with the same diameter, for Pinus. However, the enzymatic pre-treatment was the most efficient, resulting in 83% of micro/nanofibrils for Eucalyptus and 78% for Pinus. This corroborates with the lowest values of the 1.096/2.896 ratio and degree of polymerization, indicating chain shortening in cellulose. X-ray diffraction and Raman microspectroscopy crystallinity results presented similar tendencies, with increased crystallinity caused by all pre-treatments, being 5 wt% NaOH for 2 h the highest, with 70%, for Eucalyptus and Pinus. Enzymatic pre-treatment has produced the best fibrillation and greater crystallinity. The present work has shown a reliable way of assessing cellulose structure using Raman microspectroscopy. [ABSTRACT FROM AUTHOR]

The cell wall of plant fibers may contain irregular regions called dislocations. This study evaluated the effect of chemical pretreatment as a mechanochemical dislocation initiator in unbleached and bleached Eucalyptus sp. fibers. Accordingly, bleached and unbleached pulps of eucalyptus were subjected to chemical pretreatments with sodium hydroxide at concentrations of 5% for 2 h, 10% for 1 h and 10% for 2 h or with hydrogen peroxide. The extent of dislocations was evaluated by polarized light microscopy. Based on the observation, an index of dislocations (ID) expressing their ratio of cell wall as per two-dimensional (2D) imaging and their angle relative to the longitudinal direction of the fiber were estimated. Chemical pretreatments increased the ID for bleached and unbleached fibers as well as increased the changes in the curl of bleached and unbleached fibers for chemical pretreatments. Chemical pretreatment extracted the hemicellulose of the fiber cell wall causing some fiber to curl, which in turn generated new dislocations and modifications in the dislocation angles which may be useful for improving the deconstruction process of the cellulose fibers. [ABSTRACT FROM AUTHOR]

Energy expenditure is a limiting factor for the production of cellulose micro/nanofibrils in mechanical processing. This study evaluated the effect of novel alkaline pretreatments on unbleached Eucalyptus sp. pulps (hardwood) and Pinus sp. cellulose (softwood) to facilitate the production of cellulose nanofibrils by mechanical fibrillation and reduce the energy consumed by the mill. Pretreatments with NaOH in concentrations of 5% for 2 h and 10% for 1 h and 2 h and a hybrid pretreatment with 5%/16% NaOH/H2O2 for 2 h were evaluated. The 10% pre-treatment was done at 1 h and 2 h to evaluate the effect of the less aggressive treatment (1 h). The morphology, chemical composition, turbidity of the fibers/suspensions, mechanical properties, fibrillation quality index and energy expended during the fibrillation were evaluated for each pretreatment. The less aggressive pretreatments produced micro/nanofibrils with fewer passes of the pulp through the fibrillator, which effectively facilitated extraction with lower energy consumption. The hybrid pretreatment did not show satisfactory results in reducing energy consumption, and the quality of the nanofibrils produced by this pretreatment was inferior to the others. This study showed innovation in performing novel and efficient NaOH and hybrid (NaOH/H202) pretreatments on commercial unbleached pulps to obtain pulp micro/nanofibrils. [ABSTRACT FROM AUTHOR]