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Application · Biodegradable & PLA

Biodegradable Plastic Extrusion: Protect the Molecules

Q: Why air-cooled strand?

PLA and starch-based compounds are hygroscopic; air cooling avoids re-absorbing water and losing molecular weight.

Q: Can the line run 60% starch?

Yes, with a dedicated screw configuration and a side feeder for starch; the limiting factor is usually starch dryness, not the machine.

Q: What output can you guarantee for this application?

The reference band is 100–1,000 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%.

Q: 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.

Q: 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.

PLA, PBAT and starch blends degrade twice: once in the environment, which is the point, and once in the extruder, which is a scrap batch. The whole line is designed around the second one. A reference biodegradable plastic extrusion page from Kerke.

Updated 6 November 2026

Output 100–1,000 kg/h

Line type Co-rotating twin screw KTE

Basis parameter table + material trial

Biodegradable Plastic Extrusion — workshop photo 1, Kerke workshop, Nanjing

Biodegradable Plastic Extrusion — workshop photo 2, Kerke workshop, Nanjing

Biodegradable Plastic Extrusion — workshop photo 3, Kerke workshop, Nanjing

Biodegradable Plastic Extrusion — workshop photo 4, Kerke workshop, Nanjing

Biodegradable Plastic Extrusion — workshop photo 5, Kerke workshop, Nanjing

Biodegradable Plastic Extrusion — workshop photo 6, Kerke workshop, Nanjing

Running video — Biodegradable Plastic Extrusion, Kerke workshop

Quick answer

Biodegradable compounds (PLA, starch-based, PBAT, PBAT/PLA blends) run at 120–180 °C with L/D 40–48 and gentle screw designs that protect molecular weight. Output 100–1,000 kg/h. Air-cooled strand pelletizing is preferred over water cooling to avoid hydrolysis.

170–200 °CPLA window

<0.05%moisture

140–200 kg/hKTE-65

Workshop photos and a running video — shot on our own lines, not stock images.

What sets the limit

Starch or PLA is dried to below 300 ppm, metered with plasticizer and compatibilizer, compounded at low shear, devolatilized and strand-pelletized with air cooling.

**Table 1.** Key parameters for biodegradable plastic extrusion line. Reference values — confirm on a material trial.
Parameter	Value / range
Materials	PLA, starch-based, PBAT, PBS, blends
Temperature	120–180 °C (PLA degrades above 200 °C)
L/D	40–48
Pelletizing	Air-cooled strand (protects molecular weight)
Output (reference)	100–1,000 kg/h
Model	KTE-50B, KTE-65B

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 120–180 °C (PLA degrades above 200 °C).
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 packingAir-cooled strand (protects molecular weight); then centrifugal dryer, vibrating screen and bagging.

Equipment configuration

**Table 2.** What the line is made of, and why each part is specified that way.
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

**Table 3.** Co-rotating twin screw KTE — reference output. Full range on the machine page.
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. Wet starch: steam flashes in the barrel and the strand breaks constantly.

Wet starch: steam flashes in the barrel and the strand breaks constantly.

2. Water bath cooling absorbs moisture back into PLA and hydrolyses it during storage.

Water bath cooling absorbs moisture back into PLA and hydrolyses it during storage.

3. Barrel profile copied from PP masterbatch

Barrel profile copied from PP masterbatch — PLA above 200–210 °C and starch blends drop molecular weight in a step; keep it short (36–40D) and cool, not long and hot.

FAQ

Why air-cooled strand?

PLA and starch-based compounds are hygroscopic; air cooling avoids re-absorbing water and losing molecular weight.

Can the line run 60% starch?

Yes, with a dedicated screw configuration and a side feeder for starch; the limiting factor is usually starch dryness, not the machine.

What output can you guarantee for this application?

The reference band is 100–1,000 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.

Tell us your material — we will tell you the line

Send 25–50 kg and we run it on our lab extruder: pellets, running video and a capacity report back in 3–7 days.

Get a quote Send material for trial

Biodegradable plastic extrusion — the short version

Note on biodegradable plastic extrusion: 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.