Effect of Flow Channel Configuration on Nano Fibril Alignment by Elongational Flow

Abstract

Cellulose Nano-fibrils (CNFs) are the fundamental building blocks extracted from wood fibers and have gained great attentions as a novel biological material. It is known that the outstanding mechanical properties of cellulose filament made of CNFs can be obtained with their orientation inside the filament, the orientation control of CNFs is essential in the material fabrication. In this study, the effect of channel configuration on the orientation of CNFs by elongational flow are clarified both by numerical simulation and experiment. The higher CNF orientation parameter can be obtained for the channel with the focusing angle of 45 degrees compared to that with 90 degrees and also by increasing the flow rate ratio of downstream sheath flow to the upstream one. The ultimate tensile strength and toughness of cellulose filament increases by 11 % and 59 %, respectively by increasing flow rate ratio from 1.0 to 3.0 with 45 degrees focusing angle as predicted from the numerical simulation results.