Home/Applications/Long Fiber (LFT-G) Impregnation

Application · Long Fiber & Composites

Long Fiber (LFT-G) Impregnation: 20–60% Glass

Long fibre is a pultrusion inside a die: the roving is opened, impregnated under pressure and cut without being chopped twice. Fibre length is set by the die, not by the screw. A reference lft-g impregnation page from Kerke.

Updated 6 November 2026

Output 200–1,000 kg/h

Line type Co-rotating twin screw KTE

Basis parameter table + material trial

Long Fiber LFT-G Impregnation — workshop photo 1, Kerke workshop, Nanjing

Long Fiber LFT-G Impregnation — workshop photo 2, Kerke workshop, Nanjing

Long Fiber LFT-G Impregnation — workshop photo 3, Kerke workshop, Nanjing

Long Fiber LFT-G Impregnation — workshop photo 4, Kerke workshop, Nanjing

Long Fiber LFT-G Impregnation — workshop photo 5, Kerke workshop, Nanjing

Long Fiber LFT-G Impregnation — workshop photo 6, Kerke workshop, Nanjing

Running video — Long Fiber LFT-G Impregnation, Kerke workshop

Quick answer

LFT-G lines impregnate continuous rovings with a polymer melt in a cross-head die, then cut to 11–25 mm pellets. Notched impact strength is typically 2–3× that of short-fibre compounds at equal fibre loading. Output 200–1,000 kg/h.

20–60%glass content

10–25 mmpellet length

LFT-Gprocess

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

What sets the limit

Rovings are preheated and spread, pulled through a cross-head die where the melt impregnates them, cooled, then cut into long pellets by a granulator designed for 11–25 mm lengths.

**Table 1.** Key parameters for long fiber (lft-g) coating & impregnation line. Reference values — confirm on a material trial.
Parameter	Value / range
Process	Continuous roving impregnation (LFT-G)
Pellet length	11–25 mm
Fibre content	20–60%
Impregnation	Cross-head die + spreading pins
Output (reference)	200–1,000 kg/h
Model	KTE-65B + LFT cross-head die

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 packingdie-face or strand pelletizing, see the pelletizing page; 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. Poor fibre spreading leaves dry fibres and the pellets fail impact testing.

Poor fibre spreading leaves dry fibres and the pellets fail impact testing.

2. Standard strand pelletizers cannot cut 11–25 mm pellets; a dedicated granulator is require

Standard strand pelletizers cannot cut 11–25 mm pellets; a dedicated granulator is required.

3. Pulling fibre through the crosshead too fast

Pulling fibre through the crosshead too fast — impregnation happens under controlled back-pressure, not line speed; rush it and the core of the strand stays dry.

FAQ

Can you supply the whole LFT-G line?

Yes — impregnation die, cooling conveyor, puller and long-pellet granulator as one line, with the KTE extruder as the melt source.

What fibre length survives injection moulding?

Pellets at 11–25 mm yield 3–8 mm residual fibre length in the moulded part, which is where the impact gain comes from.

What output can you guarantee for this application?

The reference band is 200–1,000 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

LFT-G impregnation — the short version

Note on lft-g impregnation: 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.