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Production of nanofibrillated cellulose (CNF) has gained increasing attention during the last decades with its recent industrialization, but such a process consumes still too high of an amount of energy. Here, cellulose nanofibrils at high solid content (20−25 wt %) and consuming 60% less energy compared to conventional processes were produced from enzymatic and TEMPO-oxidized cellulose fibers thanks to a twin screw extruder equipped with kneading disks and fully flighted conveying screws. The morphology and properties of the produced CNF were characterized using optical microscopy, atomic force microscopy (AFM), mechanical properties, and light transmittance. CNF with a width in the range of 20−30 nm and mechanical properties close to those obtained with commercial CNF (Young's modulus around 15 GPa) were produced. However, results from the degree of polymerization and crystallinity showed that twin screw extrusion (TSE) degrades the fibers as far as the supermasscolloider grinder is concerned. TSE appears as a new mechanical treatment that allows producing CNF at high solid contents and with low energy demand, which is a real asset for nanocellulose industrialization.

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The aim of this work is to study and compare the influence of different nanofibrillation processes on the properties of cellulose nanofibers from wheat straw, and analyze the effect of the lignin in the nanocellulose quality and on the characteristics of the films produced. Wheat straw was subjected to a soda (NaOH) pulping process to obtain unbleached cellulosic pulp. The cellulosic pulp was bleached with NaClO 2 in order to remove the lignin of the fiber. Both bleached and unbleached pulps were used to obtain nanocellulose using mechanical pretreatment (PFI refining) and treatments, (high pressure homogenization, twin-screw extruder and ultrafine friction grinder). The effect of the nanofibrillation treatments and the residual lignin content on cellulose nanofiber production was analyzed by means of a deep characterization. A multi-factorial quality index was used to score the cellulose nanofibers produced to enable a benchmarking study between different sources, processes and characteristics. In addition, an energetic study of the production process was carried out for the different treatments. The different nanofibers were used to produce cellulose nanofiber-based films and characterized in order to establish a relationship between the characteristics of cellulose nanofibers and the characteristics of the final product.

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