Newsletter  2017.2  Index

Theme : "The Conference of Fluid Engineering Division"  Preface M.MOTOZAWA, T.HASHIMOTO, S.MATSUDA The Study of Turbulence in the 21st Century Shinichiro YANASE (Okayama University) Research on amorphous actuators utilizing liquid crystal flows Rinko MATSUDA, Tomohiro TSUJI, Shigeomi CHONO (Kochi University of Technology) Flow Structure of Hub-Corner Separation in a Stator Cascade of a Multi-Stage Transonic Axial Compressor Seishiro SAITO（Kyushu University） A levitating droplet over a moving surface Erina SAWAGUCHI, Kai HAMA, Yoshiyuki TAGAWA (Tokyo University of Agriculture and Technology) Innovative Cellulose Material Synthesis by Electrostatic Fibril Alignment Yusuke Takeda (Tohoku University), Christophe Brouzet, Nitesh Mittal, Fredrik Lundell (KTH Royal Institute of Technology, Sweden), Hidemasa Takana (Tohoku University) Developing “Dream Strider”, a machine for the removal of floating materials on the water surface Kota TSUBONE, Yo MUNETA (Hiroshima Kokutaiji Senior High School) The Dreams of Flow Contest Haruka YAMAUCHI (Meisei University)

 

Innovative Cellulose Material Synthesis by Electrostatic Fibril Alignment

Yusuke Takeda Tohoku University Christophe Brouzet KTH Royal Institute of Technology Nitesh Mittal KTH Royal Institute of Technology Fredrik Lundell KTH Royal Institute of Technology Hidemasa Takana Tohoku University

Abstract

In recent years, cellulose nanofibrils (CNF) have attracted significant attention as a novel biomass material. The fibrils are produced by liberating wood fibers to their nano-scale building blocks and have considerable potential to be applied to composite materials due to their outstanding mechanical (high stiffness of the crystalline regions ~ 138 GPa) and thermal properties (low thermal expansion). In order to synthesis a cellulose filament with high mechanical properties from CNF, it is essential to enhance the CNF alignment in a cellulose filament. Recently, flow-focusing method has been proposed as an effective enhancement of the CNF alignment during a cellulose filament synthesis. In this method, the CNF alignment is controlled by extensional flow to be parallel to the flow direction. However, the degree of the CNF alignment obtained by this method is not still high enough to extract the outstanding mechanical properties of CNF. In this study, an innovative method for controlling the CNF alignment has been developed by combining the electrostatic fibril alignment with previously proposed flow-focusing method. Firstly, the response of micro-scale cellulose fibrils was investigated through visualization under AC electric field in a petri dish without flow. It was found that under AC electric field, the fibrils align parallel to the direction of the electric field by electrostatic torque acting on electric dipole of the fibrils by taking approximately 20 seconds. Secondly, this electrostatic fibril alignment method was applied to the dynamic flow-conditions in the flow focusing channel, where three pairs of electrodes are located upstream of the flow-focusing section. The CNF alignment was measured in the downstream of the electrodes in the flow-focusing channel through the optical measurement using the birefringent characteristics of CNF dispersion. It was clearly shown that upstream AC electric field enhances the CNF alignment in the flow-focusing section.

 

Key words

Cellulose Nanofibrils, Cellulose Material Synthesis, Electrostatic Field, Fibril Alignment, Multiphase Flow

 

Figures

(a) 0 V_pp

(b) 1 kV_pp, 5 kHz

Fig. 1 Visualization of micro-scale cellulose fibrils with or without AC electric field.

Fig. 2 Schematic illustration of experimental setup with a flow-focusing channel imposing electrostatic field for the alignment of charged fibrils in the upstream of flow-focusing section.

Fig. 3 Axial distribution of transmitted light intensity for various applied voltages obtained from the averaged CCD image at the square sections shown in the picture.