Why This Matters for Textile Professionals
Synthetic fiber spinning transforms raw polymers
into usable fibers—determining strength, elasticity, and end-use performance.
Understanding these methods is essential for fiber engineers, product
developers, and textile students.
1. Melt Spinning (Thermoplastic Polymers)
Principle: Extrusion
of molten polymer through spinneret followed by rapid cooling.
Key Fibers Produced:
- Polyester (PET) – Apparel, home textiles
- Nylon 6 & Nylon 6,6 – Hosiery, sportswear
- Polypropylene (PP) – Nonwovens, ropes
- PLA (Polylactic Acid) – Biodegradable textiles
Technical Highlights:
- Temperature Control Critical (PET: 260-290°C, Nylon: 220-265°C)
- Shear Rate Effects – Higher extrusion speeds reduce viscosity
- Quenching Air Velocity – 0.5-2 m/s for uniform crystallinity
*(Industry Fact: Accounts for 75%+ of
synthetic fiber production due to speed & cost efficiency.)*
2. Dry Spinning (Solvent-Based, Volatile
Removal)
Principle: Dissolved
polymer extruded into hot gas to evaporate solvent.
Key Fibers Produced:
- Acrylic – Sweaters, faux fur
- Spandex (Lycra®) – Stretch fabrics
- Vinyon (PVC-based) – Filter fabrics
Technical Highlights:
- Solvent Choice is Critical (DMF for acrylic, DMAc for spandex)
- Mass Transfer Limitation – Diffusion rate of solvent in air (~10⁻⁵ m²/s)
- Residual Solvent – Must be <1% for textile safety
(Pro Tip: Used when polymers
degrade before melting.)
3. Wet Spinning (Coagulation Chemistry)
Principle: Polymer
solution extruded into liquid bath for phase separation.
Key Fibers Produced:
- Viscose Rayon – Dresses, linings
- Acrylic (Alternative Process) – Outdoor fabrics
- Aramid (Kevlar®) – Bulletproof vests
- Modal & Lyocell – Sustainable cellulosics
Technical Highlights:
- Bath Composition Dictates Fiber Structure (e.g., H₂SO₄ for rayon)
- Skin-Core Morphology – Controlled by coagulation rate
- Environmental Challenge – Solvent recovery systems mandatory
*(Emerging Trend: Closed-loop Lyocell
process recovers 99% solvent.)*
4. Gel Spinning (Ultra-High Molecular
Weight)
Principle: Semi-dilute
polymer solution stretched to align molecules.
Key Fibers Produced:
- UHMWPE (Dyneema®) – Body armor, marine ropes
- PBO (Zylon®) – Firefighter gear
- High-Strength PAN – Carbon fiber precursor
Technical Highlights:
- Ultra-Low Concentration (0.5-2% polymer)
- Superdrawing – Draw ratios up to 100:1
- Crystallinity Matters – Up to 95% for maximum strength
(Performance Benchmark: Dyneema®
is 15x stronger than steel by weight.)
Quick-Reference Comparison Table
|
Method |
Principle |
Key Fibers |
Throughput |
Strength (g/den) |
|
Melt |
Melt → Extrude → Cool |
PET, Nylon, PP |
Very High |
3-9 |
|
Dry |
Dissolve → Evaporate |
Acrylic, Spandex |
Medium |
2-5 |
|
Wet |
Dissolve → Coagulate |
Rayon, Aramid |
Low |
3-8 |
|
Gel |
Gel → Ultra-Draw |
UHMWPE, PBO |
Very Low |
15-35 |
1.
Melt spinning dominates due
to speed, but limited to thermoplastics.
2.
Dry spinning costs more but
essential for heat-sensitive polymers.
3.
Wet spinning enables cellulose
regenerated fibers (eco-alternatives).
4.
Gel spinning creates the strongest
fibers but has low productivity.
5. Fiber cross-section shapes (round, trilobal, hollow) depend on spinneret design.