Masters Theses

Date of Award

5-1994

Degree Type

Thesis

Degree Name

Master of Science

Major

Aerospace Engineering

Major Professor

Mancil W. Milligan

Committee Members

Harvey J. Wilkerson, Rao V. Arimilli

Abstract

A comprehensive experimental investigation was conducted to determine the effect that the processing parameters have on the fiber diameter of micro fibers produced in the melt blowing process. The UTK single hole die melt blowing facility was used during this research and only 650 MFR polypropylene was utilized. Among the processing parameters that were investigated were the die geometry (air gap, setback, and air jet injection angle), polymer throughput, air jet exit velocity, and collection distance. Also, data was collected to establish the independent effect that both the air jet temperature and polymer temperature have on the diameter of the fibers.

Increasing the air jet momentum decreased the average fiber diameter. This increase in air jet momentum was attained by: increasing the air jet exit velocity, increasing the air gap, reducing the setback, or by decreasing the air jet injection angle. Also, a decrease in the polymer flow rate produced smaller fibers. The variation in the average fiber diameter for samples collected from 10 to 40 inches from the die tip was within the uncertainty of the fiber diameter measuring technique. Polymer temperature showed a strong effect on the average fiber diameter; an increase in polymer temperature produced smaller fiber for a constant air jet temperature. The air jet temperature however, showed a negligible effect on the diameter of the fibers.

Single fibers were collected to determine the effect that the air jet temperature had on fiber strength. A trend of producing stronger fibers at lower air jet temperatures was found. The difference in the strength of these fibers however, was very small even for large differences in air jet temperatures.

Several empirical models were developed using the experimental data collected during this research. The dimensionless variables used in developing these models accounted for the most important parameters that describe the melt blowing process: die geometry, air jet and polymer temperature, air flow rate, and polymer throughput and viscosity. These models successfully predicted the average fiber diameter within 2 microns not only for samples processed at the UTK single hole die, but also for samples processed at the UTK 20 inch multiple hole die.

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