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Pelletizing · Underwater Hot Die-Face Pelletizing

Underwater Hot Die-Face Pelletizing: How Kerke Builds It

Knives cutting inside a pressurized water chamber — perfectly round, dense pellets for TPE/TPU, hot melt adhesives, EPP beads and every product where shape is part of the spec.

Updated 11 November 2026

Scope TPE/TPU · hot melt · EPP beads

Output 200–2,000 kg/h

Pellet Round, dense

Underwater Hot Die-Face Pelletizing — workshop photo 1, Kerke workshop, Nanjing

Underwater Hot Die-Face Pelletizing — workshop photo 2, Kerke workshop, Nanjing

Underwater Hot Die-Face Pelletizing — workshop photo 3, Kerke workshop, Nanjing

Underwater Hot Die-Face Pelletizing — workshop photo 4, Kerke workshop, Nanjing

Underwater Hot Die-Face Pelletizing — workshop photo 5, Kerke workshop, Nanjing

Underwater Hot Die-Face Pelletizing — workshop photo 6, Kerke workshop, Nanjing

Quick answer

Underwater pelletizing cuts the melt at the die face inside a flooded, pressurized chamber. Pellets are round, dense and dust-free straight out of the water — the required shape for TPE/TPU, hot melt adhesives, EPP expandable beads and spun-grade or foam-grade polymers where irregular pellets would feed unevenly.

200–2,000 kg/hcapacity range

≈1.0pellet roundness

8 bartypical chamber pressure

±2 °Cchamber water band

Workshop photos — shot on our own lines in Nanjing, not stock images.

How the underwater hot die-face pelletizing line works

Melt enters a circular die plate inside the water-filled cutting chamber.
Rotating hub knives cut pellets flush at the die face under water pressure.
Chamber water flow carries pellets up the discharge pipe to a dewatering screen.
Centrifugal drying brings surface moisture below 0.2%.
Start-up is automated: chamber pre-heating and a scrap diversion sequence prevent die freeze-off.

Where this method wins

Underwater wins where pellet geometry is functional: EPP beads must be round to roll evenly in moulds; hot melt adhesives must flow; TPE/TPU blocks when strand-cut because the material is tacky; and spinning or foaming grades need dust-free round pellets. The costs are a more complex start-up and higher maintenance skill — we automate both.

Reference data

**Table 1.** Underwater Hot Die-Face Pelletizing — reference selection data.
Item	Value
Best for	TPE/TPU, hot melt adhesive, EPP beads, round-pellet polymers
Output range	200–2,000 kg/h
Pellet shape	Round, dense, dust-free
Watch out	Water temperature and flow, die freeze-off at start-up

Reference output measured on the stated material family; subject to a material trial. Die hole count sets the capacity ceiling — check the die, not the label.

Selection notes from our floor

Water temperature inside the chamber is material-specific — TPU wants warm water so pellets do not freeze into tails, EPP wants cold water for bead stability. Our standard control loop holds chamber water within ±2 °C and sequences the start-up so the die never sees stagnant water.

FAQ

Why must TPE be underwater?

TPE and TPU stay tacky after the die. On strands they glue to guides and to each other; cut underwater, the surface sets instantly and pellets leave as individual beads.

What happens on an unplanned stop?

Without the start-up sequence, melt in the die holes freezes and blocks them. Our lines divert scrap and keep water circulating during stops, so a restart takes minutes, not hours.

Can one underwater line serve EPP and TPU?

Yes with a changeover kit: die plate, knife speed and water temperature are the change items. Plan half a day including purging.

Where these numbers come from

Output ranges, pellet shapes and watch-outs come from Kerke commissioning records and the pelletizing systems parameter table. Where a catalogue value and a trial value disagree, the trial value is the one we quote.

Reviewed by the Kerke process team, Nanjing. Page updated 11 November 2026.

Not sure which pelletizing method fits your material?

Send 25–50 kg — we return pellets, a video and a report with the parameters we used, in 3–7 days.

Get a quote Send material for trial

Underwater Hot Die-Face Pelletizing — the short version

Underwater cutting delivers spherical, dust-free pellets for TPE, TPU, hot-melt adhesives and EPP beads — the premium choice when pellet appearance and flowability matter, at the cost of a more demanding start-up procedure.