Glass fiber reinforced polypropylene and polyamide compounds are among the most demanded engineering materials in the automotive, electrical, and consumer goods industries, yet building the right production line is rarely a matter of buying one machine. Kerke, a Wanplas factory, brings 12+ years of experience, a 19,997+ sqm factory, 2,000+ machines running worldwide, and service in 70+ countries to help producers configure a complete, balanced, and repeatable glass fiber PP PA twin screw compound line. This accumulated field experience across hundreds of glass fiber lines is the practical foundation behind the matching logic in this article, because every numerical recommendation below has been validated on real production compounds rather than taken from a generic catalog. This article presents a complete machine matching scheme that shows exactly which machines go together, why they are matched, and how to size each module for a glass fiber reinforced line. Whether you are compounding GF PP for automotive interior parts or GF PA for structural components, the logic of matching the twin-screw extruder, side feeder, liquid feeder, pelletizing system, and auxiliary equipment remains consistent. The goal is a line that protects glass fiber length, delivers uniform dispersion, removes volatiles through vacuum devolatilization, and produces clean, free-flowing pellets at a predictable output.
A machine matching scheme is different from a plant setup guide. Instead of focusing on factory layout and civil works, this scheme focuses on the technical configuration of the machinery itself: which screw diameter and L/D ratio to choose, where the glass fiber enters, how the coupling agent is dosed, which pelletizing method fits the material, and what supporting equipment keeps the line stable. By the end of this article you will be able to translate a target output and a target glass fiber ratio into a concrete bill of machines, with Kerke KTE series twin-screw extruders as the core and Wanplas shared engineering standards backing every module.
Understanding Glass Fiber Reinforced PP and PA Compounding Requirements
Glass fiber reinforced compounds are defined by three quality pillars that the entire machine scheme must protect: fiber length retention, dispersion quality, and devolatilization. If any one of these pillars fails, the finished compound loses the mechanical performance that justifies its higher cost, and downstream injection molding or extrusion suffers from weak weld lines, surface defects, or inconsistent shrinkage. A correct machine matching scheme begins by translating these material requirements into machine functions, not by selecting a single catalog model.
Fiber length retention is the single most important factor in glass fiber compounds. The reinforcing value of glass fiber comes from its aspect ratio, the ratio of length to diameter, and long fibers carry load far better than short, broken fibers. In a twin-screw process, fibers enter as chopped strands of roughly 4 to 25 millimeters and are progressively cut and oriented by the screw shear. Adding glass fiber too early, at the solid feed throat, forces the dry, abrasive fiber to pass through the high-shear melting zone where it shatters into useless fragments. The machine scheme must therefore place a side feeder downstream of the initial melting zone so fibers meet an already molten, low-viscosity polymer film and are wetted with minimal mechanical abuse. The remaining residence time before the die should be short and gentle.
Dispersion is the second pillar. Good dispersion means each glass fiber is individually coated by the polymer matrix and evenly distributed throughout the melt, with no agglomerates, bundles, or streaks. Dispersion is governed by the kneading block arrangement, the screw speed, and the local shear rate. A co-rotating twin-screw extruder is superior here because its fully intermeshing, self-cleaning screws generate controllable, repeatable shear and wipe the barrel wall clean, preventing stagnant material that would degrade. The machine scheme must specify enough kneading and mixing length, usually in the L/D 36 to 52 range, to fully coat the fibers without overheating the polymer.
Devolatilization is the third pillar and is especially critical for polyamide. PA is hygroscopic and hydrolyzes if moisture remains in the melt, which permanently reduces molecular weight and impact strength. Even after pre-drying, residual moisture and volatiles from coupling agents or processing aids must be removed. The machine scheme must include a dedicated vacuum vent barrel section, ideally two venting ports, with sufficient free volume and a stable melt seal so the vacuum pulls gas without dragging melt into the vacuum line. A well-matched line removes volatiles without losing output or creating foam in the pellet.
Beyond the three pillars, the scheme must respect thermal sensitivity. Glass fiber compounds often include coupling agents, silanes, antioxidants, and flame retardants that degrade if over-heated or over-sheared. The matched line therefore needs precise barrel zone temperature control, a screw design that limits peak temperature, and a cooling strategy for the gearbox and barrel. These requirements directly drive the module choices described in the following sections.
In production, fiber length retention is verified by dissolving the pellet in a heated solvent or acid that removes the polymer while leaving the glass intact, then measuring the fiber length distribution under a microscope. A well-matched line keeps the weight-average fiber length above an application-specific target, and the machine scheme is judged by how close it comes to that target at full commercial output rather than only at a gentle laboratory setting. This is why the side feeder position and the downstream residence time are treated as first-class design variables, not as adjustments made after the line is built.
Coupling agent chemistry is the practical fourth requirement that the scheme must serve. Glass fiber is polar and hydrophilic, while polypropylene is non-polar and polyamide is semi-polar, so without a coupling agent the fiber-matrix interface is weak and moisture quickly undermines adhesion. A silane or a maleic anhydride grafted polymer bridges the two phases and lifts both dry and wet mechanical strength. The machine scheme must deliver this additive through the liquid feeder at the correct point so it coats the fiber before the melt cools and solidifies, which is only possible when the extruder has a dedicated liquid injection port matched to the screw layout.
Finally, the scheme must protect product consistency across the full campaign. Glass fiber compounds are abrasive, and screw and barrel wear changes the free volume and shear over time, which slowly shifts the dispersion quality. The matched line therefore pairs wear-resistant barrel liners and screw elements with a planned maintenance interval and a small stock of interchangeable elements, so that the output stays within specification for years rather than months. Consistency, not a one-time good pellet, is what defines a successful glass fiber compounding line.
The Core Principle of Machine Matching for GF Compounding
The core principle of machine matching for glass fiber compounding is to build a continuous, modular train where each machine performs one function at the right place and the whole train is balanced to the target output. The train starts with raw material preparation, moves through gravimetric feeding, melting and fiber incorporation in the twin-screw extruder, devolatilization, pelletizing, and ends with pellet cooling and conveying. The twin-screw extruder is the heart, but an undersized feeder, the wrong pelletizer, or a missing dryer will bottleneck the entire line. Matching means sizing every module to the same hourly throughput.
At the center sits the Kerke KTE series co-rotating parallel twin-screw extruder, available from KTE-16B laboratory models up to KTE-135D production models. For glass fiber PP and PA lines, the workhorse sizes are KTE-50, KTE-65, and KTE-75. These models share a modular barrel with screw diameters of about 50, 65, and 75 millimeters and configurable L/D ratios from 36 to 52. The configuration that matters most for GF compounding is the element layout: a conveying and melting section at the feed end, a kneading and mixing section in the middle, a downstream side feeder port for glass fiber, a liquid injection port for coupling agent, at least one vacuum vent, and a metering section before the die.
The main feeder is a loss-in-weight system that meters resin and filler by mass with high accuracy, independent of bulk density variations. Glass fiber roving or chopped strand is added through a twin-screw side feeder that pulls fiber into the melt at a controlled rate and angle. A liquid feeder injects coupling agent or silane directly into the melt, improving the fiber-matrix interface. Vacuum venting removes moisture and volatiles. The melt then passes to the pelletizing system. Each of these feeders and ports must be matched to the extruder’s free volume and screw speed so that the line runs at a single, stable mass flow.
Torque is the practical limiting factor. Glass fiber compounds are viscous and abrasive, so the gearbox must supply enough torque per screw to process the melt without stalling or overheating. The matched models below are selected so that, at the target glass fiber ratio of 10 to 50 percent, the screw speed and torque land in a safe, efficient window rather than at the mechanical limit. Sizing the extruder one size larger than a marginal calculation is usually the cheaper choice once downtime and scrap are counted.
Screw Element Configuration for Glass Fiber Lines
The KTE series builds its screw from individual elements mounted on the splined shafts, and the arrangement of those elements is the real engineering content of the machine matching scheme. Conveying elements with deep flights move material forward and set the residence time. Kneading blocks, which are lens-shaped discs offset at an angle, generate the shear that disperses filler and wets the glass fiber; their stagger angle and width control how aggressively the melt is worked. Reverse elements and restrictor rings build local pressure that forces the melt to fill the side feeder port and the vacuum vent properly. Mixing elements with intermeshing pins homogenize temperature and composition before the die.
For glass fiber work the classic layout starts with a long conveying and melting zone, places the first kneading block after the polymer is molten, keeps the side feeder port in a low-shear region so fibers enter a gentle melt, then uses a second, milder kneading zone to finish coating, and ends with a metering zone that feeds the die at steady pressure. The L/D ratio of 36 to 52 gives room to fit all these functions plus one or two vents without crowding. Kerke engineers compute the element combination from the resin viscosity, the glass fiber ratio, and the target output, then validate it on a sample run before shipment. This element-level matching is what separates a productive glass fiber line from a generic compounding extruder that merely happens to have a side feeder attached.
A balanced scheme also accounts for changeover. Many producers run GF PP in the morning and GF PA in the afternoon, or shift between 10 percent and 50 percent glass fiber. The modular screw and barrel design of the KTE series lets you re-arrange elements and feeder positions without replacing the machine, which is why the scheme favors co-rotating twin-screw technology over fixed single-screw or batch systems for glass fiber work.
Kerke KTE-65 Twin-Screw Extruder Core Module Specification
The Kerke KTE-65 is the most common core module for medium-capacity glass fiber PP and PA compounding, typically serving lines with a target output of 250 to 450 kg/h at 10 to 50 percent glass fiber. Its screw diameter of roughly 62 to 65 millimeters gives enough free volume for intensive kneading while remaining economical on floor space and energy. The table below lists the representative specification for a GF-optimized KTE-65 configuration.
KTE-65 Representative Specification for GF Compounding
| Parameter | KTE-65 GF Configuration | Engineering Note |
|---|---|---|
| Screw type | Co-rotating parallel twin-screw | Self-cleaning, modular elements |
| Screw diameter | 62.4 mm (nominal 65) | Standard KTE series size |
| L/D ratio | 36 to 52 (configurable) | 52 recommended for full GF + vent |
| Center distance | 52 mm | Determines element interchangeability |
| Main motor power | 90 to 132 kW | Depends on L/D and torque class |
| Max screw speed | 500 to 600 rpm | Controlled by inverter |
| Max torque per shaft | About 1100 Nm | High torque class available |
| Output (GF 10 to 50 percent) | 250 to 450 kg/h | For PP and PA based compounds |
| Side feeder | Twin-screw, downstream | For glass fiber roving or chop |
| Venting | One or two vacuum vents | Devolatilization of PA moisture |
| Liquid port | Yes, for coupling agent | Metered silane injection |
| Control system | PLC and HMI with recipe storage | Closed-loop temperature control |
In a GF PP or GF PA line, the KTE-65 is matched with a loss-in-weight main feeder, a downstream side feeder, a liquid feeder for coupling agent, and a water ring or air-cooled pelletizer depending on output. Its moderate footprint and medium energy draw make it the default choice for producers scaling from lab validation to commercial volumes without committing to the larger KTE-75 footprint.
Kerke KTE-75 Twin-Screw Extruder High-Capacity Module Specification
The Kerke KTE-75 is the high-capacity core module for glass fiber PP and PA compounding when the target output reaches 450 to 800 kg/h. With a screw diameter of about 71 millimeters and a larger free volume per unit length, it sustains higher mass flow while keeping screw speed moderate, which reduces specific energy and fiber breakage. The table below shows the representative specification.
KTE-75 Representative Specification for GF Compounding
| Parameter | KTE-75 GF Configuration | Engineering Note |
|---|---|---|
| Screw type | Co-rotating parallel twin-screw | Self-cleaning, modular elements |
| Screw diameter | 71 mm (nominal 75) | Standard KTE series size |
| L/D ratio | 36 to 52 (configurable) | 52 recommended for PA + two vents |
| Center distance | 60 mm | Uses larger element set |
| Main motor power | 160 to 220 kW | High torque gearbox |
| Max screw speed | 450 to 600 rpm | Lower rpm than KTE-65 at same output |
| Max torque per shaft | About 2000 Nm | Suits high viscosity GF melt |
| Output (GF 10 to 50 percent) | 450 to 800 kg/h | For PP and PA based compounds |
| Side feeder | Twin-screw, downstream | Handles high fiber throughput |
| Venting | Two vacuum vents | Strong devolatilization for PA |
| Liquid port | Yes, for coupling agent | Metered silane injection |
| Control system | PLC and HMI with recipe storage | Closed-loop temperature control |
For high fiber load above 30 percent or for heat-sensitive polyamide grades, the KTE-75 matches best with underwater or water ring pelletizing to keep residence time short and pellets clean. Its larger torque reserve means it can absorb formulation swings, such as a shift from 10 percent to 50 percent glass fiber, without a screw speed change that would otherwise break fibers. The KTE-75 is the recommended core when a single line must serve multiple glass fiber compounds at commercial scale.
Pelletizing System Matching: Air-Cooled Strand, Water Ring, Underwater
Pelletizing is the downstream module that converts the homogeneous glass fiber melt into a stable, free-flowing product, and the choice of method must match the material and output. Kerke supplies a full range of cutting and pelletizing systems: air-cooled strand pelletizing, water ring die face hot cutting, underwater granulation, and related variants. The three most relevant for GF PP and GF PA are air-cooled strand, water ring die face, and underwater granulation. Each has a clear operating window.
Air-cooled strand pelletizing pulls several extruded strands through a water bath and a dryer, then cuts them with a rotary knife into cylindrical pellets. It is the most flexible and lowest-cost option, ideal for lab lines, pilot lines, and small to medium commercial lines that change formulation frequently. Its downside is a higher labor and strand-break risk at very high output, and the strand bath can dull glass fiber at the pellet cut, though this is acceptable for most compounds.
Water ring die face pelletizing cuts the melt at the die face while a ring of water carries the pellets away and cools them. It runs continuously, produces uniform round pellets, and handles medium to high output with low dust. For GF PA and GF PP at 250 to 600 kg/h, the water ring system is often the best balance of cost, cleanliness, and uptime.
Underwater granulation cuts the melt below the water surface at the die face and is the premium choice for high output above 500 kg/h and for heat-sensitive or highly filled compounds. It delivers the most uniform, spherical, low-fines pellets and supports the longest uninterrupted runs, which is why it is matched to the KTE-75 at full capacity. The table below matches the pelletizing method to material and line size.
Pelletizing Selection by Material and Output
| Method | Best Output Range | Material Fit | Key Advantage |
|---|---|---|---|
| Air-cooled strand | Lab to 300 kg/h | GF PP, GF PA, masterbatch | Flexible, low cost, easy changeover |
| Water ring die face | 250 to 600 kg/h | GF PP, GF PA, filled compounds | Continuous, low dust, uniform round pellets |
| Underwater granulation | 500 to 1200 kg/h | High GF PA, heat-sensitive compounds | Spherical pellets, longest runs, best hygiene |
From a cost perspective the three methods follow a clear ladder. Air-cooled strand pelletizing carries a Low procurement cost and Medium operating cost, which is why it dominates pilot and small lines. Water ring die face pelletizing sits at Medium procurement cost and Low to Medium operating cost thanks to continuous running and low labor. Underwater granulation has a High to Very High procurement cost and Medium operating cost, but its yield, pellet uniformity, and uptime often make it the lowest total cost at large scale. The machine matching scheme selects the method by output and material first, then confirms the choice fits the buyer’s cost tolerance using these relative labels rather than a fixed price.
In all three methods, the matched line includes a pellet dryer and a vibrating screener to remove fines and oversized pellets before silo or bagging. For glass fiber compounds, controlling fines matters because fiber dust irritates downstream handling and weakens the bulk density of the pellet. The pelletizing choice should be locked at the same time as the extruder size, not decided afterward, because the die and melt pump interface depend on it.
Auxiliary Equipment Matching
A glass fiber twin-screw compounding line is only as stable as its weakest support module. The auxiliary equipment matching scheme covers the machines around the extruder that prepare material, recover scrap, condition temperature, and protect the process. Kerke supplies a complete auxiliary range: high-speed mixer, plastic granulator, pulverizer, water chiller, and dryer, all matched to the extruder throughput.
Auxiliary Matching Table
| Auxiliary | Function in GF Line | Matching Rule |
|---|---|---|
| High-speed mixer | Pre-blend resin, filler, additives | Batch volume sized to 1 to 2 hours of feed |
| Dehumidifying dryer | Dry PA below 0.1 percent moisture | Throughput matches loss-in-weight feeder |
| Plastic granulator | Reclaim off-spec strand or scrap | Rotor width matched to scrap rate |
| Pulverizer | Size-reduce flakes or regrind | For re-introduction as filler |
| Water chiller | Cool gearbox and barrel, control temp | Capacity sized to heat load of motor |
| Vacuum loader | Convey material to feeders | Matched to feeder demand |
The dehumidifying dryer deserves special attention for GF PA. Polyamide absorbs moisture from ambient air within hours, so the dryer must sit close to the loss-in-weight feeder and the transfer line must be sealed. A water chiller is not optional for high torque lines; it removes the heat generated by the gearbox and barrel friction, keeping the screw speed stable under load. The matched scheme treats these auxiliaries as part of the line, not as afterthoughts, because a failed dryer or chiller stops the whole train.
A vacuum loader and, for larger lines, a central feeding system, keep the loss-in-weight feeder supplied without operator intervention. Glass fiber lines run for long shifts, and an empty feeder for even a minute creates a composition step that ruins a batch and forces a purge. Matching the loader capacity to the feeder demand, and placing a day bin between dryer and feeder, removes this risk and lets the line run unattended through a full shift. The auxiliary matching scheme therefore treats material transport as a controlled, metered stage rather than a casual scoop-and-pour step.
Process Parameter Matching for GF PP and GF PA
Process parameters translate the machine scheme into a running recipe. The table below gives representative barrel zone temperatures, screw speed range, and fiber addition point for GF PP and GF PA at 30 percent glass fiber on a KTE-65 or KTE-75 with L/D 48. These values are starting points; the exact recipe must be optimized on the actual material during commissioning and validated by mechanical testing.
Representative Process Parameter Table (GF 30 percent)
| Parameter | GF PP (30 percent) | GF PA6 (30 percent) | GF PA66 (30 percent) |
|---|---|---|---|
| Feed zone temperature | 180 to 200 deg C | 220 to 240 deg C | 250 to 270 deg C |
| Melting zone temperature | 200 to 220 deg C | 240 to 260 deg C | 270 to 290 deg C |
| Mixing zone temperature | 210 to 230 deg C | 250 to 270 deg C | 280 to 300 deg C |
| Fiber addition point | Side feeder, zone 5 to 6 | Side feeder, zone 5 to 6 | Side feeder, zone 5 to 6 |
| Vent zone temperature | 200 to 220 deg C | 240 to 260 deg C | 270 to 290 deg C |
| Die temperature | 210 to 230 deg C | 250 to 270 deg C | 280 to 300 deg C |
| Screw speed | 300 to 500 rpm | 300 to 500 rpm | 300 to 450 rpm |
| Vacuum level | -0.06 to -0.09 MPa | -0.08 to -0.095 MPa | -0.08 to -0.095 MPa |
The fiber addition point at zone 5 or 6 leaves just enough downstream length for coating and devolatilization without over-shearing the fiber. Polyamide grades need the higher temperatures and stronger vacuum because of their melting point and moisture sensitivity. Keeping the melt temperature rise controllable through the mixing zone protects both the coupling agent and the polymer from thermal degradation. The recipe is stored in the PLC so that every production run repeats the same profile.
During commissioning the recipe is optimized step by step rather than set in one move. The team first establishes a stable melt at low screw speed with no glass fiber, confirms the vacuum holds, then introduces fiber gradually while watching motor load, melt pressure, and pellet appearance. Screw speed is the main lever for output, but raising it also shortens residence time and can reduce dispersion or increase fiber breakage, so the optimum is found where output, dispersion, and fiber length all meet target. Temperature is tuned to keep the melt homogeneous without crossing the degradation threshold of the coupling agent, and the final recipe is locked into the PLC recipe library for repeat runs across every shift and every operator.
Complete Model Selection Scheme by Output and Glass Fiber Ratio
The following selection scheme converts a customer requirement into a matched bill of machines. It pairs the target output and glass fiber ratio with a Kerke KTE core model and a pelletizing method, and assumes the full feeder and auxiliary package described above. This table is the practical payoff of the machine matching scheme: a procurement-ready configuration rather than a vague recommendation.
Need to Model Selection Table
| Target Output | Glass Fiber Ratio | Matched Core Model | Matched Pelletizing | Key Feeders |
|---|---|---|---|---|
| Lab or R and D, 5 to 30 kg/h | 10 to 50 percent | KTE-16B or KTE-25 | Air-cooled strand | Loss-in-weight, side feeder |
| 150 to 250 kg/h | 10 to 30 percent | KTE-50 | Air-cooled strand | Loss-in-weight, side feeder, liquid |
| 250 to 450 kg/h | 10 to 50 percent | KTE-65 | Water ring die face | Loss-in-weight, side feeder, liquid, vacuum |
| 450 to 800 kg/h | 10 to 50 percent | KTE-75 | Underwater granulation | Loss-in-weight, side feeder, liquid, two vacuum |
| 800 to 1500 kg/h | 10 to 50 percent | KTE-95 or larger | Underwater granulation | Multiple side feeders, liquid, two vacuum |
The scheme also plans for growth. A producer starting at 250 kg/h on a KTE-65 can later add a second side feeder or move to a KTE-75 on the same building footprint and auxiliary package, because both models share feeder interfaces, pelletizer mounts, and control architecture within the Wanplas engineering standard. This protects the initial investment and lets capacity scale in steps rather than requiring a completely new line. The selection table should therefore be read not only for today’s order but for the next two product generations the buyer expects to run, so the first machine purchased remains the core of an expanding train.
This scheme is deliberately conservative on screw speed. Running a KTE-65 at 450 kg/h of 50 percent GF is possible but pushes shear and fiber breakage upward; the scheme prefers the KTE-75 for that duty. The logic is to match the model to the hardest case in your product mix, not the average, so the line keeps running when you switch from 10 percent to 50 percent glass fiber or from PP to PA.
Application Industries for the GF PP PA Compounding Line
The matched glass fiber PP and PA line serves a wide band of industries because reinforced engineering plastics replace metal, reduce weight, and survive demanding environments. Kerke, as a Wanplas factory, serves these application industries with the same KTE twin-screw platform, so the machine matching scheme scales from a single compound to a full product portfolio.
In the automotive sector, GF PP is used for bumper beams, door panels, and under-hood components, while GF PA serves intake manifolds, cooling system parts, and structural clips. The line must hold tight color and mechanical consistency because parts are often painted or assembled to metal. In electrical and electronics, GF PA provides flame-retarded housings and connectors where dimensional stability under heat is mandatory. In consumer goods and power tools, GF compounds deliver the stiffness and impact resistance needed for housings and gears.
Beyond engineering plastics, the same scheme supports masterbatch production, where the twin-screw extruder disperses color, filler, or additives into a carrier resin, and biodegradable compounds, where the gentle, well-vented screw protects heat-sensitive biopolymers. Cable compounding uses the same feeder and vent logic to embed flame retardants and fillers uniformly. The scheme therefore doubles as a versatile compounding platform, not a single-product line.
Within these industries the reinforced compounds appear in concrete end products that define the quality bar. In automotive, a GF PA intake manifold must survive continuous under-hood heat and aggressive fluids while holding tight dimensions, so the line’s devolatilization and dispersion directly affect warranty returns. In electronics, a flame-retarded GF PA connector must keep its shape through wave soldering, which ties back to consistent glass fiber distribution. In building and consumer goods, GF PP profiles must avoid warpage and surface glass bloom, which depends on fiber wetting and pellet cleanliness. The machine matching scheme is ultimately judged by these end-product performances, not by extruder horsepower alone, and that is why the feeder, vent, and pelletizer choices are made together rather than in isolation.
Service and Support for Your Compounding Line
Machine matching does not end at shipment. Kerke, a Wanplas factory, applies the shared Wanplas group service commitment to every glass fiber PP PA compounding line. The policy includes USD 500 free parts per year, free replacement of damaged parts within warranty, pre-shipment testing, on-site installation and commissioning, operator training, and remote technical support. These commitments protect the uptime of the matched line after it leaves the factory.
The open factory policy welcomes customers to visit the 19,997 plus square meter facility, witness a running line, and conduct sample trial runs on their own material before purchase. This is especially valuable for glass fiber compounds, where seeing fiber length retention and pellet quality firsthand removes guesswork. The shared Wanplas promise of quality standards with refund and compensation backing gives buyers confidence that the matched configuration will meet the stated capacity and quality.
Spare parts strategy is built into the scheme. The KTE series uses standardized, interchangeable screw and barrel elements, so a small stock of common kneading blocks and barrel liners covers most maintenance needs. Combined with the USD 500 free parts per year allowance, the operating cost of the line stays predictable. Training covers screw element assembly, feeder calibration, vacuum system operation, and pelletizer adjustment so the customer team can run changeovers independently.
Frequently Asked Questions
Why is a co-rotating twin-screw extruder preferred for glass fiber PP and PA compounding?
A co-rotating parallel twin-screw extruder provides intensive, controllable shear and excellent self-cleaning that lets you distribute glass fiber uniformly while limiting fiber breakage. The modular barrel and screw layout supports a downstream side feeder for fiber, a vacuum vent for devolatilization, and a liquid port for coupling agent, which a single-screw machine cannot combine in one pass.
Where should glass fiber be added in the screw configuration?
Glass fiber is added through a side feeder positioned downstream of the initial melt and homogenization zones, typically at barrel zone 5 or 6 of an L/D 36 to 52 system. By that point the polymer is already molten and the melt film is thick enough to wet the fibers, so the short remaining residence time minimizes fiber breakage and protects fiber length retention.
How do I choose between air-cooled strand, water ring die face, and underwater pelletizing?
Air-cooled strand pelletizing is the most flexible for lab and small to medium lines with frequent formulation changes. Water ring die face pelletizing suits medium to high output of PA and PP with low dust and continuous operation. Underwater pelletizing is the best choice for high capacity above 500 kg/h and heat-sensitive or highly filled compounds that need clean, uniform, spherical pellets.
What output can I expect from a KTE-65 or KTE-75 GF compounding line?
For glass fiber loading between 10 percent and 50 percent, a Kerke KTE-65 typically delivers 250 to 450 kg/h depending on screw speed and L/D, while a KTE-75 delivers 450 to 800 kg/h. Actual output depends on resin type, glass fiber ratio, filler load, and whether a side feeder and liquid port are used.
Do I need a dehumidifying dryer for PA before feeding the extruder?
Yes. Polyamide is strongly hygroscopic and even small moisture causes hydrolysis that destroys molecular weight and weakens the compound. A dehumidifying dryer should bring PA to a moisture content below 0.1 percent before it enters the loss-in-weight feeder, and a vacuum vent on the extruder removes residual volatiles during processing.
What is the role of the liquid feeder in a GF PA or GF PP line?
The liquid feeder injects coupling agent, silane, or other processing aids directly into the melt in a metered way. This improves the interface between the polar glass fiber and the non-polar or semi-polar polymer matrix, lifting mechanical properties such as tensile strength and impact strength without overloading the main feeder.
How does Kerke support commissioning and spare parts for the line?
Kerke, as a Wanplas factory, provides a shared group policy of USD 500 free parts per year, warranty replacement for damaged parts, pre-shipment testing, on-site installation and commissioning, operator training, and an open factory policy that welcomes customer visits and sample trial runs.
Can the same machine matching scheme serve masterbatch and biodegradable compounds?
Yes. The same KTE twin-screw platform with modular screw and barrel elements also serves color and filler masterbatch, biodegradable compounds, cable compounds, and PVC or thermoplastic elastomer compounding by swapping screw element combinations, barrel venting, and feeder layouts. The matching logic of feeder, vent, pelletizer, and auxiliary stays consistent.
Conclusion
A glass fiber PP PA twin screw compound line is a system, not a single machine, and the complete machine matching scheme presented here shows how to balance the Kerke KTE twin-screw extruder, downstream side feeder, loss-in-weight and liquid feeders, vacuum devolatilization, pelletizing system, and auxiliary equipment into one repeatable train. By protecting fiber length retention, dispersion, and devolatilization through correct screw design, fiber addition point, and venting, the matched line delivers consistent, high-quality reinforced compounds at predictable output from 150 to 800 kg/h and beyond.
Kerke, a Wanplas factory with more than 12 years of experience, a 19,997 plus square meter factory, over 2,000 machines running worldwide, and service in more than 70 countries, stands ready to configure the exact KTE model, pelletizer, and auxiliary package for your glass fiber polypropylene and polyamide products. We invite you to share your target output, glass fiber ratio, and resin grade so our engineering team can prepare a tailored machine matching scheme, arrange a sample trial run, and welcome you to our open factory for a live demonstration of the line running on your material.
