Nonuniform Cooling in Multifilament Melt Spinning of Polypropylene Fibres: Cooling Air Speed Limits and Fibre-to-Fibre Variations
| Title |
Nonuniform Cooling in Multifilament Melt Spinning of Polypropylene Fibres: Cooling Air Speed Limits and Fibre-to-Fibre Variations |
| Publication year |
1995 |
| General note |
DOI 10.1002/app.1995.070580925 |
| Language |
English |
| Author |
Andreassen, Erik |
| Co-Authors |
Grøstad, Kristin - Hinrichsen, Einar L. - Oldervoll, Frøydis - Dale Braathen, Marianne - Myhre, Ole Jan (Norner) |
| Source |
Journal of Applied Polymer Science, 58 (9), 1995, 1619-1632 |
| Abstract |
The cooling of the spinning stage in a commercial compact-spinning line has been studied. A rectangular fibre bundle is extruded from the spinneret and cooled by air entering from one side. The speed of the cooling air is considerably reduced through the fibre bundle. There are practical lower and upper limits for the cooling air entrance speed, corresponding to filament breakage at the leeward and windward sides, respectively. These limits are functions of the material and processing parameters. Due to the non-uniform cooling, fibres sampled at the windward side generally have higher molecular orientation, lower amorphous fraction, higher density, and higher tensile modulus and strength. For most combinations of spinning and material parameters, the structure is either bimodally oriented a-crystalline or uniaxially oriented mesomorphic at all spinneret positions. Fibres with different structure types show opposite windward/leeward side trends with regard to local order and melting behaviour. The structure may be mesomorphic at the leeward side and a-crystalline at the windward side, if the average spinline stress is close to a critical value for orientation-induced crystallisation, and the air speed difference across the spinneret is large. The cooling air speed affects the spinline stress. Hence, the fibre-to-fibre variations due to non-uniform cooling are discussed in terms of the molecular orientation in the melt and the effective time available for arranging molecules into ordered structures. |