Nanocrystalline (CNC) and nanofibrillated (CNF) cellulose can be obtained from renewable resources, such as lignocellulosic materials. CNC is traditionally produced by acid hydrolysis, while a significant mechanical process to isolate neighboring cellulose nanofibrils is needed to obtain CNFs. This disassembling process can be facilitated by previous treatments that impart electrostatic repulsion between surface charged groups. In this work, sugarcane bagasse and eucalyptus chips pretreated and bleached were oxidized using a 2,2,6,6 tetramethylpiperidine-1-oxyl (TEMPO)-mediated system with different amounts of oxidizing agent (5, 25, and 50 mmol (NaClO)/g cellulose. Atomic Force Microscopy (AFM) results showed that sugarcane bagasse pulps oxidized with 5 mmol/g of cellulose were partially disaggregated, while fibers oxidized with 25 and 50 mmol/g disassembled directly after oxidation, without the need for high-energy mechanical treatments, and formed CNFs with kinks and diameters in the 3-5 nm range. The same result was not achieved in eucalyptus chips due to the higher recalcitrance of this biomass. After a sonication step, sugarcane bagasse CNFs were broken down into cellulose nanocrystals (CNC) due to the cleavage of interchain interactions.<br/>Underwater mechanical properties of casting films prepared from TEMPO-oxidized nanocelluloses depend on the aspect ratio and surface charge of CNFs. Ionic crosslink with CaCl<sub>2</sub> considerably improved the wet stability of highly charged nanocelluloses.

Mechanical treatment-free cellulose nanofibers and their application for wet films

ACS Spring Meeting 2021

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