Application · Recycling & PET
PET Pelletizing & Sheet: Keep the IV
PET is judged on one number after pelletizing: intrinsic viscosity. Water and heat destroy it, so drying, low-shear screw design and the right pelletizer are not options but the specification. A reference pet pelletizing page from Kerke.
PET Pelletizing & Sheet — workshop photo 1, Kerke workshop, Nanjing
PET Pelletizing & Sheet — workshop photo 2, Kerke workshop, Nanjing
PET Pelletizing & Sheet — workshop photo 3, Kerke workshop, Nanjing
PET Pelletizing & Sheet — workshop photo 4, Kerke workshop, Nanjing
PET Pelletizing & Sheet — workshop photo 5, Kerke workshop, Nanjing
PET Pelletizing & Sheet — workshop photo 6, Kerke workshop, NanjingQuick answer
PET bottle flake recycling requires pre-drying at 160 °C for 4–6 hours, low-shear melting to protect intrinsic viscosity, vacuum devolatilization and water-ring strand pelletizing. Output 300–2,000 kg/h; IV loss per pass is typically 0.02–0.05 dL/g when the flake is dry.
Workshop photos and a running video — shot on our own lines, not stock images.
What sets the limit
Flake is de-dusted, crystallized and dried, then melt-filtered (60–80 µm), devolatilized, optionally chain-extended and strand-pelletized. The whole line is designed around moisture and IV, not throughput.
| Parameter | Value / range |
|---|---|
| Feed | PET bottle flake, washed, < 100 ppm moisture after drying |
| Pre-drying | 160 °C × 4–6 h (crystallizer + dryer) |
| L/D | 36–44 (low shear) |
| Devolatilization | 2-stage vacuum, optional chain extender (ADR) |
| Pelletizing | Water-ring strand |
| Output (reference) | 300–2,000 kg/h |
Output figures are measured on the reference material stated above. Filler grade, bulk density and moisture move output by ±15% — that is why every quotation we issue is tied to a trial report.
Process flow, step by step
- FeedingLoss-in-weight dosing of polymer and filler; side feeder or liquid injection where the formulation needs it.
- Melting and dispersingScrew geometry with 45°/90° kneading blocks; barrel profile set by the polymer.
- DevolatilizationVacuum vent at −0.06 to −0.09 MPa removes moisture and volatiles before the die.
- Pressure build-upThrottle or discharge section stabilises die pressure; a melt pump where gauge control matters.
- Pelletizing and packingWater-ring strand; then centrifugal dryer, vibrating screen and bagging.
Equipment configuration
| Stage | Equipment | Why this choice |
|---|---|---|
| Main machine | Co-Rotating Twin Screw Extruder | Architecture follows the filling level and the mixing duty, not the required tonnage. |
| Screw geometry | Building-block elements, W6Mo5Cr4V2, bimetallic liner | Wear package for abrasive filler; mixing blocks only where dispersion demands them. |
| Feeding | Loss-in-weight feeder, side feeder where needed | Recipe accuracy: ±0.5% short term on the weighed component. |
| Pelletizing | Pelletizing system | Chosen by polymer and filler ceiling — water contact is the deciding column. |
| Downstream | Centrifugal dryer, vibrating screen, bagging | Fines below 2% and moisture below the specification of your downstream process. |
Output by model
| Model | Dia. (mm) | Speed (rpm) | Motor (kW) | Torque (N·m) | Output (kg/h) |
|---|---|---|---|---|---|
| KTE-50B | 50.5 | 500–600 | 55–75 | 2×525 | 80–200 |
| KTE-50D | 50.5 | 300–800 | 75–90 | 2×860 | 100–300 |
| KTE-52B | 51.4 | 500–600 | 55–75 | 2×720 | 80–200 |
| KTE-52D | 51.4 | 500–600 | 75–110 | 2×1050 | 100–400 |
| KTE-65B | 62.4 | 500–600 | 90–110 | 2×860 | 200–450 |
| KTE-65D | 62.4 | 300–800 | 132–160 | 2×1530 | 350–600 |
| KTE-75B | 71 | 500–600 | 132–160 | 2×1530 | 300–800 |
| KTE-75D | 71 | 300–800 | 200–315 | 2×2100 | 500–1000 |
| KTE-85B | 85 | 500–600 | 220–315 | 2×2100 | 550–1000 |
| KTE-95B | 93 | 500–600 | 250–315 | 2×3000 | 800–1500 |
| KTE-95D | 93 | 500–800 | 315–500 | 2×4800 | 1000–2000 |
| KTE-135B | 135 | 500–600 | 315–500 | 2×4800 | 1500–3000 |
| KTE-135D | 135 | 500–800 | 500–1000 | 2×7800 | 1500–4000 |
Three mistakes that cost the most
1. Skipping crystallization: amorphous flake fuses into a solid mass in the dryer.
Skipping crystallization: amorphous flake fuses into a solid mass in the dryer.
2. High shear screw: IV drops 0.1+ per pass and the pellets fail the downstream spec.
High shear screw: IV drops 0.1+ per pass and the pellets fail the downstream spec.
3. No fine filtration: paper and label residue end up as specks in the filament.
No fine filtration: paper and label residue end up as specks in the filament.
FAQ
How much IV loss per pass?
0.02–0.05 dL/g with dry flake and a low-shear screw. If you see more, check flake moisture first, then melt temperature.
Do I need a chain extender?
Only if the incoming IV is below 0.70 or you need food-grade IV above 0.80. ADR adds cost and needs careful dosing.
What about food-grade rPET?
That requires a certified process (EFSA/FDA letter of no objection), usually with a vacuum devolatilization stage and documented residence time — we design the mechanical part, certification is with your process auditor.
Can the line run bottle flake and film scrap?
Bottle flake yes; film needs a different feeding and compaction stage, so it is normally a separate line configuration.
What output can you guarantee for this application?
The reference band is 300–2,000 kg/h, measured on the stated material. We quote a guaranteed figure only after a trial on your own material, because filler grade, bulk density and moisture move output by ±15%.
Can we run our material before ordering?
Yes — send 25–50 kg. We return pellets, a running video and a report with temperatures, screw speed, feeder settings and output per hour. The trial is free; you cover the freight.
What is the delivery time?
30–45 working days for standard configurations, 45–70 for custom screw geometry and ODM work. Voltage and frequency are built for the destination country.
Where these numbers come from
Parameters are taken from the Kerke product parameter table and the product master data sheet, and cross-checked against commissioning records for lines in the same application. Formulations and temperature windows are typical industry values, not a recommendation for your specific compound — every figure marked reference must be confirmed on a material trial before it becomes a contractual number.
Reviewed by the Kerke process team, Nanjing. Page updated 6 November 2026.
Send 25–50 kg and we run it on our lab extruder: pellets, running video and a capacity report back in 3–7 days.
PET pelletizing — the short version
Note on pet pelletizing: the numbers above are reference ranges from Kerke's own trial runs, not catalogue promises. Screw geometry, wear package and pelletizing method are set on the trial bench first, so the output you compare is the output you get. If your grade is not in the tables, send it — the closest configuration is usually a change of screw set, not a different machine.
Related on this site: Machine range: KTE-50B to 135D · Pelletizing methods compared · quotation and free trial · Wikipedia: Masterbatch