Nanocellulose Production by Twin-Screw Extrusion: Simulation of the Screw Profile To Increase the Productivity

Cellulose nanofibrils (CNFs) have gained increased attention since the last 15 years and can now be produced at high solid content in an energy-efficient way using twin-screw extrusion. In this study, a screw profile was optimized using simulation software in order to produce high-quality CNFs in one pass through the twin-screw extruder, instead of several passes as reported in other studies, decreasing the energy consumption, improving the productivity, and hence making the industrialization of such a process more probable. An optimized profile was designed using the software according to previous studies, and an enzymatic cellulose pulp was experimentally nanofibrillated. Produced CNFs were characterized using several techniques such as optical microscopy, mechanical properties, turbidity, nanosized fraction, or quality index. The optimized screw profile contains six blocks of kneading disks with left-handed staggering and imparts high levels of shear, strain, and energy in the first pass. CNFs were successfully produced in a single pass with equivalent quality than the CNF produced in at least four passes using a classic profile, without changing the energy consumption. Produced CNFs present high transparency and a Young's modulus of around 13 GPa.