Melt Blowing with Louvers and their Effects on Fiber Attenuation and Motion

Abstract

A physical plateau in the air field below a melt blowing die was imposed by airfoil shaped louvers. These louvers prevented air jet spreading and imposed a constant average air velocity on the polymer filament, resulting in greater attenuation. Fibers were collected and measured offline using optical microscopy. Fiber diameters were found to be significantly reduced when louvers are in the air field compared to normal melt blowing conditions. Longer chords expose longer lengths of the fiber threadline to the nondecaying air velocity, causing a greater forwarding force on the fiber and thus greater attenuation and finer diameters. Angled chords act as a nozzle and expose the fiber to an increasing air velocity. This was found to be more beneficial for shorter chords that expose less of the threadline to the nondecaying air velocity. Louvers placed closer to the die resulted in finer diameters and less fiber sticking. High Speed Photography was employed to observe the motion of a melt blown polymer filament when louvers were in the air field. Videos of the fiber were taken with a Redlake HS-4 camera capable of high frame rates. The position of the fiber over time was tracked at different distances below the die, and a code was implemented to calculate the frequency and amplitude of the fiber for various positions, configuration, and louver sizes. A methodology for online fiber temperature measurements with the louvers in the air field is presented.