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Nylon Thread: Melt-Spun Monofilament, Cold-Drawn Between Two Drums, Carothers
Nylon sewing thread is a single clear strand, a monofilament. Carothers' patent (1938) spins nylon 66 straight from the melt at 285–295 °C, with oxygen kept out, and catches the strand on a drum. A second, faster drum then stretches it (cold drawing), which makes it strong.
The picture: our own drawing.
Advanced
1 day
Instructions
1
1
Load the pot under nitrogen
Load the pot under nitrogen
Fill the melt-spinning pot with dry nylon 66 pellets and close it. Flush it with nitrogen and keep it under nitrogen: oxygen must stay out of the molten polymer.
Materials for this step:
Nylon Pellets500 gTools needed:
Melt-Spinning Pot
Nitrogen
Pressure Gas Cylinder2
2
Melt at 285–295 °C
Melt at 285–295 °C
Heat to 285–295 °C, the best spinning heat for nylon 66. Cooler gives poorer filament; hotter makes it too runny, and it may break down.
Tools needed:
Melt-Spinning Pot
Thermocouple with Readout3
3
Extrude and catch it
Extrude and catch it
Press the melt out through the hole with nitrogen pressure (Carothers' example used 50 lb/in²). Catch the strand on a motor-driven drum. A larger hole gives a thicker strand; hotter melt and faster winding give a finer one.
Tools needed:
NitrogenPressure Gas Cylinder
Take-Up Drum
Electric Motor4
4
Cold-draw onto a faster drum
Cold-draw onto a faster drum
Run the strand from the first drum onto a second drum turning faster, which stretches it. In Carothers' example the drums ran at 300 and 1020 ft/min. Keep the strand wet: wet filament draws better and holds no static.
Tools needed:
Take-Up DrumElectric Motor
Water5
5
Help a thick strand
Help a thick strand
Thick strands are harder to draw. Soak them in water, or warm them to about 100 °C, before drawing.
Tools needed:
SaucepanWaterMaterials
1- 500 gPlaceholder
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