Influence of cellulose chemical pretreatment on energy consumption and viscosity of produced cellulose nanofibers (CNF) and mechanical properties of nanopaper
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Lignocellulosic fibers are the main sources for producing nanocellulose, in which mechanical methods are the most appropriate to achieve a high yield and generate low residue. High energy consumption is the major drawback in these processes, although they are the cheapest way to produce nanocellulose. Chemical pretreatment is one approach to further decrease the overall cost during defibrillation; however, the influence over sample viscosity and mechanical properties is yet to be investigated. Here, we study the influence of chemical pretreatments using NaOH and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) on the mechanical, rheological and structural properties of cellulose nanofibers made from bleached eucalyptus pulp. Modification of samples was evidenced by their respective peaks on FTIR spectra. Sample crystallinity increased after partial hemicellulose and amorphous cellulose removal. In addition, a strong correlation between grinding efficiency and lower energy consumption was observed. However, a mild alkaline treatment may improve fiber strength at the expense of suspension stability and energy consumption. Modified nanofibers presented good potential for enhancing mechanical properties and/or improving suspension stability.
KeywordsDisintegration Hemicellulose Pretreatments Processing energy TEMPO-oxidation
The authors would like to thank Conselho Nacional de Desenvolvimento Científico e Tecnológico (National Council of Technological and Scientific Development) and Embrapa Florestas for financially supporting this work. We also thank CME – UFPR (TEM analysis), Physics Department – UFPR (XRD analysis), Dr. Ivo Demiate for granting access to the viscometer analysis at Universidade Estadual de Ponta Grossa (UEPG) and Mrs. Bia Carneiro for providing the English revision of the accepted manuscript.
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