Melt-spun fiber degradation

J. A. Cicero, J. R. Dorgan, S. F. Dec, D. M. Knauss, Phosphite stabilization effects on two-step melt-spun fibers of polylactide. Polym. Degrad. Stab. 2002, 78, 95-105. 

The physical properties of the polymer often dictate the spinning method that must be used for fiber formation. For example, if the melt temperature is above the thermal degradation temperature, the polymers cannot be melt spun. Such polymers must be liquified with... 

Nishimura et al. (2005) produced PLLA fibers using a melt spinning process. PLLA was first dried in vacuum at 70 °C, melted and extraded at a melt temperature of 220 °C in order to avoid thermal degradation. Pellets were extruded with a single-screw extruder, at the end of which a spinning nozzle with 12 holes was placed. Extrusion took place in a water bath kept at 45 °C, and spun fibers were drawn at 98 °C in order to have enough energy to achieve solvent evaporation. The mechanical and other properties of the PLLA fibers were preserved. 

Because the polymer is soluble in dimethylacetamide containing 5% LiCl, fibers can be spun directly from solution. This polyamide melts at 371 with degradation. It is fire resistant. The fibers are sold under a trade name of Nomex. 

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