Extruder Design and Melt Rheology
topic
Single-screw extruders (L/D ratio 24:1 to 30:1) melt PET chips through compression, melting, and metering zones. PET melt at 280–295°C is a viscoelastic pseudoplastic fluid; melt viscosity follows power-law model η = K·γ̇ⁿ⁻¹ (n ≈ 0.6 for PET). Shear rate in spinneret holes: 1000–10,000 s⁻¹. Gear pump provides precise melt metering (±0.5% throughput variation).
Role
Extruder design and melt rheology control are fundamental to consistent filament denier, minimising thermal degradation, and preventing pressure fluctuations that cause filament breaks and uneven spinning.