Flow-Induced Orientation of Fiber-Suspensions in a Molding Process Flow

Abstract

We investigated birefringence of suspended cellulose nanofiber (CNF) liquids with constant flow rate owing to flow-induced orientation change of the suspensions passing through a rectangular channel with a tapered contraction. For rheological properties, non-Newtonian viscosity and gel-like behavior of CNF-suspensions exhibited. Velocity in the flow direction and elongational rate increased around the inlet of contraction. The experimental results of CNF-suspensions were independence of tapered angle for the contraction. However, overshoot behavior of tapered angle = 120° alone exhibited. Moreover, the resultant birefringence was dependence of the tapered angle. For understanding the experimental results, we discussed flow behavior (flow path line) and relationship between velocity and birefringence. Possibility of existence of corner-vortex before contraction was discussed. Furthermore, the experimental results were compared with those of a polymer solution (aqueous solution of Xanthan-Gum). The difference between two test fluids was obtained.