Structural and rheological insights of oxidized cellulose nanofibers in aqueous suspensions

Today, nanosized components derived from the most plentiful and renewable resource, cellulose, are increasingly being used in a wide range of modern technologies. Aside from cellulosic nanocrystals, cellulose nanofibers (CNFs) have exceptional properties that make it grow in demand for technological applications. Intrigued by this remarkable trend, our work aims to consider four different types of commercially available cellulose (microcrystalline (MCC), eucalyptus (EYPT), alpha-cellulose (α-CEL), and cotton linters (CL)), as reproducible sources to extract the CNFs. The proposed procedure uses the disintegration of the fibers using the oxidation mediated by the stable radical TEMPO applied to the previously activated samples by a combined alkaline-acidic treatment. The four varieties of CNFs that resulted were analyzed based on electrokinetic potential and carboxylic group loading. Their morphology has been thoroughly investigated utilizing electron microscopic techniques like SEM and AFM revealing that the produced nanofibers had a uniform configuration, with a width of 48–90 nm and length of about 108–445 nm. Rheological investigations revealed high viscosity and yield stress values for CNFs sample isolated from α-CEL. In addition, this sample exhibits thixotropy and high ability to recover rapidly its structure after very high levels of deformation.