Two phase separation polymer-solvent systems were studied: polypropylene-paraffin wax, and polypropylene-naphthalene. A tube-in-orifice spinneret design was used.

All attempts to spin hollow fibers using the polypropyleneparaffin wax system failed. Initial attempts to produce hollow fibers from polypropylene-naphthalene solutions resulted in fiber samples with outside diameters ranging from 60 to 297 microns, and inside diameters ranging from 15 to 90 microns. However, subsequent spinning trials resulting in unpredictable solution flow behavior through the spinneret or drastic polymer degradation. A review of spinning procedures and pertinent literature led to the conclusion that chain scission of the polymer molecules was being catalyzed by contact of the polymer with certain metals (e.g. copper and iron) during solution preparation. However, with the use of a non-metallic mixing vessel and stirrer, the use of a nitrogen atmosphere, and the addition of proper stabilizers, this problem should be prevented in future studies.

From observations made by optical and scanning electron microscopes, and mercury intrusion pore size distribution measurements, it was concluded that the structure of the fibers consisted of fine networks of interconnecting voids or pores. The significant majority of these pores had diameters of less than one micron.

Among the suggested areas for further study in the development of hollow fibers spun from polypropylene-naphthalene solutions were spinning condition effects on pore size distribution and the possibility of using a controlled temperature liquid quench bath in the spinning process.