Experimental and Numerical Study on the Influence of Solution Spinning Process Parameters on Fluid Cone Morphology

Experimental and numerical investigations are conducted to characterize the polyvinylpyrrolidone (PVP) fluid cone in the solution blow spinning (SBS) process. The fluid cone evolution is captured by an industrial microscope camera. A novel force analysis based on air drag force, outside pressure, inside pressure, and surface tension is performed. Numerical methods are applied to analyze the flow field near the concave cone and spindle. The results show that the ethanol improves the spinnability of PVP solutions by simultaneously increasing viscosity and reducing surface tension. A droplet-to-fluid cone evolution model is observed for the first time in the SBS process, and a thin fluid cone represents the ideal spray pattern for fiber production. The increase in viscosity causes fluid cones to appear under lower air pressure conditions. The fluid cone contracts with increasing air pressure but expands with increased feed ration or solution viscosity. Reducing the average fiber diameter can be achieved by suppressing the fluid cone size. The instability of the fluid cone is mainly attributed to insufficient air drag force, premature solidification, and fiber whipping. The low-speed reverse airflow makes the concave cone favorable for preventing premature solidification. In the SBS process, the formation of the fluid cone results from the interaction of three control parameters: outside pressure, inside pressure, and surface tension.