Melt spinning limitations

Fig. 9.11. Ribbons or wires of amorphous metal con be mode by melt spinning. There is on upper limit on the thickness of the ribbon if it is too thick it will not cool quickly enough and the liquid will crystallise.

Undesirable adhesion to metal surfaces may cause a problem in injection molding, melt spinning, and thermoforming. In the melt spinning of PAS a variety of adhesion-related problems have been observed. These problems include the build up of polymer on spinneret surfaces resulting from both initial filament extrusion and lick-back from filament breaks. These adhesion-related problems lead to prematme spin pack failure and equipment down-time to replace spent spinneret packs, and can limit the use of PAS in certain melt spinning operations. 

The manufacture of large monofilaments, certainly larger than 100 denier, must be carried out in a water-quench process because of the inherent limitation of forced convective heat-transfer with gases. Conventional screw extruders are used for melting and conveying the polypropylene resin, just as in the case of the melt-spinning processes described above. Often, however, there are no metering pumps used in the process. 

Fig. 4.9. Steady-state limits of the reduced orientation distribution of the chain segments, 4 7tw. y>), vs. orientation angle. computed from (4.30) at several values of the processing time for melt spinning of PET with the axial elongation rate shown in Fig. 4.1 and N = 100...

Ziabicki A., Jarecki L. (2007). Crystallization-controlled limitations of melt spinning. Journal of Applied Polymer Science, Vol. 105, p>p. 215-223, ISSN 1097-4628... 

Due to the process characteristics only polymers with high decomposition temperatures and low melt viscosities can be used in melt spinning. Thus, the range of biopolymers is limited due to denaturation or decomposition of those sensitive materials. 

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