Effect Of Shear Thinning Properties Of Polymer Solution Essay

Effect Of Shear Thinning Properties Of Polymer Solution Essay

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First, the effect of shear-thinning properties of polymer solution was investigated by changing the Carreau parareters such as the zero shear viscosity η_0, relaxation time λ, and power n. Changes in any of them changes the viscosity profile changes in the casting flow, thus changing the interface shapes and shift the DCL location x_dcl measured from the projected point of the die lip corner on the belt (Fig. 1). The results of x_dcl at different Carreau parameters are shown in Fig. 2. Note that P_in is continuously changed during the computation to maintain the constant wet film thickness (h_0=300 μm), and this can be performed by the direct tracking method (Nam and Carvalho, 2010).
Fig. 2(a) shows the effect of η_0 on x_dcl. Inside the feed slot, the fluid viscosity has a distribution. At the center of feed slot, where the shear rate vanishes, η(γ ̇ ) is almost the same as η_0, but it drops gradually toward the feed slot wall as the rate increases. However, outside the feed slot, where the dope forms a sheet surrounded by the gas/liquid interfaces, the viscosity immediately increases to η_0 everywhere except near the feed slot exit, because of the vanishing shear stress at the interface. The shape of the interface near the feed slot exit is strongly affected by η_0. Furthermore, as η_0 increases, the effect from the viscous drag force by the moving belt becomes stronger, consequently, DCL is pulled toward the moving direction, i. e., x_dcl increases.
DCL moves toward the die, i. e., x_dcl decreases, as λ increases, as shown in Fig. 2(b). λ determines the critical shear rate, where the viscosity starts to decrease after the zero shear viscosity plateau. The shear rate near DCL is mainly controlled by the belt speed and the visco...


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...e short liquid curtain and the movement of dynamic contact line was investigated. According to our computational results, the location of dynamic contact line is mainly controlled by the die configurations such as the die mounting position that controls the gravity direction or the distance between the die and the belt, rather than the rheological properties. However, the steady-state results alone do not provide any clue for the quality of film, i. e., uniformity. under the real situation where the continuous casting process is surrounded by various sources of disturbances including pumps, gears and motors, potentially important issues can be the film thickness variation along the flow direction or the mechanical direction. This aspects is being computationally examined by a frequency response analysis (Lee and Nam, 2015b) and will be reported in the near future.



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