For Recommended Extrusion Temperature Control for LSZH Compounds, begin with a gradual profile rather than one fixed recipe. A practical starting window is approximately 130–180°C across feed, compression, metering, adapter, and die zones, followed by adjustment against the compound datasheet, actual melt temperature, screw geometry, line speed, moisture level, and die design.
| Extrusion zone | Starting temperature range | Primary control objective |
|---|---|---|
| Feed zone | 130–145°C | Convey pellets without premature melting |
| Compression zone | 145–160°C | Initiate controlled melting and filler wetting |
| Metering zone | 155–170°C | Complete plasticization and stabilize flow |
| Adapter zone | 165–175°C | Reduce temperature gradients before the head |
| Die zone | 170–180°C | Maintain surface quality and dimensional stability |
| Actual melt target | 160–180°C | Confirm the material is within its validated processing window |
These values are starting points, not universal settings. The operator must compare controller setpoints with actual melt temperature, shear-generated heat, melt pressure, screw speed, residence time, and the specific LSZH formulation.
LSZH compounds contain a high loading of mineral flame retardants, commonly based on aluminum trihydrate or magnesium hydroxide, together with polyolefin carriers, compatibilizers, lubricants, pigments, and processing additives. This composition gives the material low smoke and halogen-free performance, but it also increases viscosity, raises torque demand, and reduces the margin between incomplete plasticization and thermal damage. Recommended Extrusion Temperature Control for LSZH Compounds therefore requires control of the complete thermal system rather than simply setting higher barrel temperatures.
The controller display is only one part of the process. A barrel zone may show 165°C while the actual melt reaches a higher temperature because of screw shear, excessive screw speed, restricted tooling, or long residence time. For cable manufacturers, the relevant control points include set temperature, actual polymer temperature, adapter temperature, die-head temperature, melt pressure, torque, line speed, haul-off speed, and finished cable dimensions.
This guide explains how to build an LSZH extrusion temperature profile, how to distinguish thermoplastic LSZH from HFFR and irradiation-cross-linked grades, and how to troubleshoot bubbles, rough surfaces, shark skin, melt fracture, dimensional variation, and material degradation. It also provides a commissioning procedure that uses controlled adjustments instead of relying on one universal temperature recipe.
Most thermoplastic LSZH cable compounds can be evaluated initially within a 160–180°C actual melt-temperature window, but the correct value depends on polymer carrier, filler type, filler percentage, cable construction, screw design, and die geometry. A barrel profile may begin near 130–145°C in the feed zone and rise progressively toward 170–180°C at the die. The measured melt temperature should remain below the maximum processing temperature specified by the compound manufacturer.
A lower setting is not automatically safer. If the material is insufficiently plasticized, the extruder may generate additional shear heat as torque increases, producing a melt that is hotter than the controller readings suggest. Conversely, a high die setting can reduce viscosity temporarily while increasing the possibility of moisture release, surface instability, thermal aging, or additive loss.
The correct operating point is the lowest temperature that provides complete plasticization, stable melt pressure, acceptable surface finish, and required cable dimensions. Operators should record the actual melt temperature at the die exit or through a suitable melt-temperature probe rather than using barrel setpoints as the only reference.
LSZH compounds commonly use substantial mineral flame-retardant loading to meet smoke, flame, and oxygen-index requirements. Increasing filler content generally increases melt viscosity and can reduce the available processing window, especially in thin-wall insulation where the material must pass through a narrow flow channel at a controlled rate. This is why an LSZH compound may require more torque than a conventional polyolefin or PVC compound at the same output.
High viscosity also increases pressure sensitivity. A small reduction in die temperature can produce a measurable pressure rise, while a small increase in screw speed can generate additional heat through shear. Operators should therefore change only one major variable at a time and record torque, pressure, melt temperature, and output for at least several minutes after each adjustment.
LSZH compounds are not controlled by heater output alone. Screw speed, compression ratio, mixing elements, screen-pack restriction, and die land length all contribute to shear heating. If a 60 mm extruder operates at 45 rpm and then increases to 60 rpm without a corresponding review of melt temperature, the actual polymer temperature may rise even when barrel settings remain unchanged.
Excessive shear can create localized overheating, especially around mixing sections, adapter restrictions, or partially blocked screens. A stable process often requires a moderate screw speed, sufficient conveying capacity, and a screw design that disperses mineral filler without producing unnecessary frictional heat. The suitable L/D ratio and screw geometry should be confirmed with the compound supplier because thermoplastic LSZH, HFFR, and cross-linkable grades do not respond identically.
Mineral flame retardants can retain surface moisture, and inadequate storage or drying can lead to bubbles, voids, pinholes, and rough surfaces. Pre-drying requirements vary by formulation, so the supplier’s processing instructions should define whether drying is required, the drying temperature, and the maximum allowable residence time in the dryer. A dryer temperature that is too high can create premature oxidation or pellet blocking, while insufficient drying leaves moisture available for release during extrusion.
Moisture control should be verified with a documented method rather than judged only by visual inspection. Useful controls include sealed packaging, humidity-controlled storage, first-in-first-out material handling, dryer dew-point checks, and periodic moisture testing. When bubbles appear, operators should inspect moisture, venting, feed-throat cooling, and residence time before raising the temperature.
A temperature profile should be established from the feed section toward the die, with each zone assigned a specific function. The feed zone should promote solid conveying, while later zones should provide gradual melting, filler wetting, homogenization, and stable pressure development. A profile with abrupt temperature jumps can create local melting, poor dispersion, or unstable throughput.
Begin with a feed-zone setting around 130–145°C, depending on pellet shape, feed-throat cooling, and the compound’s melting behavior. The feed section should not become so hot that pellets bridge, smear, or lose conveying efficiency. If feeding becomes irregular, check hopper temperature, throat cooling, pellet moisture, and bulk density before increasing the feed-zone temperature.
Set the compression zone approximately 10–20°C above the feed zone as an initial trial. This encourages progressive melting and filler wetting without forcing the entire charge to melt immediately at the screw inlet. Monitor torque and pressure during this stage because a steep rise may indicate insufficient plasticization, excessive filler loading, restricted screens, or an unsuitable screw profile.
The metering zone commonly begins around 155–170°C for a thermoplastic LSZH trial. Its purpose is to complete melting and produce a consistent mixture before the adapter. A stable metering zone should show a gradual pressure trend, limited torque fluctuation, and no visible unmelted particles in a controlled purge sample.
If pressure remains high while the melt appears rough or contains unmelted material, a 5°C increase in the metering zone may be evaluated. The operator should wait for the material to reach thermal equilibrium before judging the result, because the delay depends on extruder size, output, and residence time. Large temperature changes can mask the underlying cause and increase the risk of overprocessing.
The adapter and die zones control the final flow condition and are especially important for cable insulation and LSZH Sheath Compound applications. A starting adapter range of 165–175°C and die range of 170–180°C can help reduce viscosity near the tooling, but the correct settings depend on die land length, tip clearance, cable diameter, and line speed.
The die should not simply be set to the highest temperature in the profile. Excessive die heat may reduce apparent viscosity while increasing sag, surface drag, plate-out, odor, discoloration, or dimensional instability. If the surface remains rough at a stable melt temperature, inspect die alignment, die land condition, screen-pack cleanliness, and cooling conditions rather than assuming more heat is required.
The actual melt temperature should be measured after the material has reached steady state. A practical stabilization period may range from 10 to 30 minutes, depending on extruder size, output, formulation, and residence time. Record the temperature together with screw speed, motor load, melt pressure, output rate, cable diameter, insulation thickness, and haul-off speed.
A controller setpoint and actual melt temperature can differ by more than several degrees when shear heat is significant. The difference becomes more important at higher output rates, with restrictive tooling, or when the compound has high mineral loading. If the actual melt temperature rises while barrel settings remain unchanged, reduce screw speed or output before lowering every heater zone.
Barrel and die temperature control for LSZH extrusion should be treated as a coordinated system. Barrel heaters manage the thermal condition of the screw and cylinder, while the adapter and die determine the final flow temperature and pressure response. Independent control of these sections is necessary because a stable barrel does not guarantee a stable die-head temperature.
Thermocouples should be positioned to measure the metal temperature close to the material flow path without being exposed to direct heater influence. Poor placement can produce false stability, with the controller cycling normally while the polymer experiences temperature swings. Installations should be checked for sensor contact, insertion depth, calibration status, and response time.
At minimum, monitor the feed, compression, metering, adapter, and die zones separately. For production lines with frequent grade changes or thin-wall insulation, add melt-pressure monitoring and a direct melt-temperature measurement point near the head. The goal is to identify whether instability originates in the barrel, screw, adapter, tooling, or cooling system.
Melt pressure is a useful secondary indicator of thermal stability. When temperature is too low, viscosity often increases and pressure rises; when temperature is too high, pressure may fall while output becomes less stable or surface defects develop. Pressure oscillations may also indicate inconsistent feeding, moisture, filler agglomeration, screen blockage, screw surging, or die restriction.
Torque provides a second process signal. A sustained torque increase of approximately 10–15% from the established baseline should trigger an inspection of feed consistency, material moisture, screen-pack condition, screw speed, and temperature profile. The exact alarm limit should be based on the extruder motor rating and the compound’s normal operating range.
Thermoplastic LSZH and HFFR compounds may appear similar because both use halogen-free flame-retardant systems, but their carrier polymers, filler packages, and processing windows can differ. A formulation based on a softer polyolefin may require lower shear and lower die temperature than a higher-viscosity grade designed for abrasion resistance or thin-wall cable insulation. The product datasheet, not a generic LSZH chart, should determine the final profile.
Irradiation-cross-linked LSZH compounds also require separate treatment. They are extruded in a thermoplastic state, but the final cross-linking step changes the material’s performance after irradiation. Excessive extrusion heat can affect surface condition, additive balance, dimensional stability, or the pre-cross-linking state, while insufficient heat can result in poor dispersion and inconsistent wall thickness.
| Material type | Typical process focus | Main temperature risk |
|---|---|---|
| Thermoplastic LSZH | Stable plasticization and cable surface control | Incomplete melting or excessive shear heat |
| HFFR compound | High filler dispersion and pressure stability | High torque, moisture release, and die pressure |
| Irradiation-cross-linked LSZH | Controlled extrusion before irradiation | Dimensional variation and thermal overprocessing |
| ATH-based formulation | Lower thermal exposure and moisture control | Water release, bubbles, and degradation |
| MDH-based formulation | Higher-temperature processing tolerance may be possible | Grade-specific decomposition and filler interaction |
The decomposition behavior of ATH or MDH must be treated as formulation-specific. Operators should not use a single assumed decomposition temperature for every compound because particle treatment, polymer carrier, additives, and test method can shift the practical limit. The process should remain below the supplier’s validated maximum melt temperature and below any observed onset of gas release, discoloration, or pressure instability.
Insufficient temperature can cause incomplete plasticization, unmelted particles, rough surfaces, high torque, elevated melt pressure, and poor filler dispersion. In cable extrusion, these conditions may appear as uneven insulation thickness, irregular eccentricity, surface lines, or reduced mechanical consistency. A low die temperature can also increase die pressure and produce shark skin or melt fracture.
The correct response is not always to increase every zone. First check whether the feed zone is conveying consistently, whether moisture is present, whether the screw is overloaded, and whether the screen pack or die is restricted. A staged increase of 3–5°C in one downstream zone is safer than a sudden 15–20°C increase across the entire machine.
Excessive temperature can reduce viscosity temporarily but create bubbles, discoloration, surface gloss changes, odor, additive migration, and thermal degradation. Long residence time makes the risk greater because the material remains exposed to heat after it has already achieved sufficient plasticization. Dead spots in the adapter or die can worsen degradation even when the average melt temperature appears acceptable.
Warning signs include a rising actual melt temperature, unexplained pressure decline, dark specks, smoke, unstable surface texture, and material remaining in the barrel during stoppages. When these signs appear, reduce screw speed or heater settings in a controlled manner, purge the machine if required, and inspect the die and adapter for stagnant material.
| Observed defect | Likely temperature-related cause | Additional variables to check | Corrective action |
|---|---|---|---|
| Bubbles or pinholes | Moisture release or excessive melt temperature | Pellet storage, dryer, venting, residence time | Dry or isolate material; reduce heat after confirming moisture |
| Shark skin | Die temperature too low or shear rate too high | Screw speed, die land, output, screen pack | Raise die temperature 3–5°C or reduce output |
| Rough surface | Incomplete plasticization or filler agglomeration | Torque, pressure, dispersion, die alignment | Adjust metering temperature and inspect tooling |
| Melt fracture | High shear stress and excessive pressure | Die restriction, screw speed, tip clearance | Reduce speed, increase downstream temperature gradually |
| Discoloration | Thermal degradation or long residence time | Dead spots, stoppage duration, melt temperature | Lower thermal exposure and purge stagnant material |
| Diameter fluctuation | Temperature or pressure surging | Feeding, haul-off, cooling, die centering | Stabilize pressure and verify cooling-water temperature |
| High torque | Melt too cold, moisture, or excessive filler loading | Feed rate, screen blockage, screw geometry | Increase one zone slightly or reduce output |
| Pressure oscillation | Feeding variation, moisture, or uneven melting | Hopper, dryer, screen pack, screw wear | Correct material flow and inspect restriction points |
When troubleshooting unstable LSZH extrusion temperatures, collect at least five synchronized readings: barrel setpoint, actual melt temperature, melt pressure, motor torque, and screw speed. Add haul-off speed, output rate, cable diameter, and insulation thickness for cable production. This data makes it possible to distinguish a thermal problem from a mechanical, material-handling, or tooling problem.
Bubbles should be investigated through moisture management before temperature is increased. Inspect unopened and opened pellet bags, storage humidity, dryer performance, vent vacuum, and the time material has remained in the hopper. If bubbles appear only after a speed increase, the additional shear heat may be releasing absorbed moisture or creating local overheating.
Shark skin and melt fracture are often linked to excessive shear at the die entrance. Lowering screw speed by 5–10%, reducing output temporarily, or increasing die temperature by 3–5°C can show whether the defect is shear-related. If the defect remains after the material flow stress is reduced, inspect die land finish, die centering, tip clearance, screen-pack configuration, and polymer buildup.
Rough surfaces can result from insufficient plasticization, filler agglomeration, poor dispersion, or a damaged die. A slight increase in the metering or die zone may help, but excessive heat can worsen the problem by increasing degradation and plate-out. Use a purge sample, pressure trend, microscopic inspection of the compound if available, and dimensional measurements to identify whether the defect begins in the melt or at the tooling.
Record the compound grade, recommended processing range, maximum melt temperature, drying instructions, intended cable application, flame-retardant system, and applicable compliance requirements. Confirm whether the material is intended for insulation, sheath, optical cable, power cable, automotive wiring, or another construction. SUNUA’s product portfolio includes LSZH FR polyolefin insulation and sheath compounds, so the selected product documentation should be matched to the exact application rather than treated as interchangeable.
Start at the lower half of the approved processing range and use a gradual five-zone profile. Allow the machine to reach thermal equilibrium before feeding material, then operate at a moderate screw speed that avoids excessive torque. Record baseline pressure, torque, actual melt temperature, output, and cable dimensions.
If pressure is high, adjust one downstream temperature zone by 3–5°C and observe the result for a defined period. If melt temperature rises without a heater change, reduce screw speed or output rather than adding cooling to every zone. If the surface improves but dimensions become unstable, review haul-off speed and cooling conditions before accepting the setting.
Check conductor centering, insulation or sheath thickness, ovality, surface condition, spark-test performance, tensile strength, elongation, aging behavior, and flame performance according to the applicable specification. IEC 60811 methods are commonly used for cable material mechanical and environmental testing, while IEC 60332 series requirements may apply to flame performance. The exact test program must match the product standard, customer specification, and cable category.
A production setting should include a target and an allowable range for each critical variable. For example, the control plan may specify actual melt temperature, melt pressure, torque, screw speed, output, haul-off speed, and finished diameter with separate warning and stop limits. Store the validated profile by compound grade and cable construction so operators do not reuse settings from a different ATH, MDH, insulation, or sheath formulation.
Temperature control cannot compensate for inconsistent compound characteristics. Supplier evaluation should include lot-to-lot melt-flow data, moisture limits, flame-retardant performance, mechanical test results, packaging specifications, technical support, and documented change control. Delivery risk should also be assessed through lead-time records, minimum order quantities, safety-stock recommendations, and the supplier’s ability to provide repeatable production lots.
SUNUA identifies itself as Hebei Sunua Advanced Material Co., Ltd. and lists LSZH FR polyolefin insulation compound, LSZH FR polyolefin sheath compound, and polyethylene sheath compound among its product categories. The company also presents ISO 9001, ISO 14001, and ISO 45001 certifications, together with product-related compliance information such as REACH and SGS documentation. Buyers should request current certificates, product-specific technical datasheets, batch test reports, and sample validation results before approving a material for production.
A total-cost review should include more than the compound purchase price. A material that causes 2% scrap on a 10,000 kg monthly production line creates 200 kg of lost material each month, before accounting for labor, electricity, rework, downtime, and customer claims. If better process stability reduces scrap from 2% to 0.8%, the recovered material equals 120 kg per month, which can be converted into a measurable annual value using the company’s actual compound cost and contribution margin.
Delivery risk should be expressed in operational terms. Record average lead time, maximum observed delay, supplier response time, replacement-lot availability, and the number of days of safety stock required. A technically suitable supplier with incomplete documentation or uncertain replenishment may create more financial exposure than a supplier with a slightly higher unit price but stable batch records, clear processing guidance, and predictable delivery performance.
The processing profile should be validated against both production requirements and the final cable standard. Typical checks include dimensional tolerances, conductor centering, elongation, tensile strength, heat aging, low-temperature performance, volume resistivity where applicable, spark testing, flame propagation, smoke behavior, and halogen-related requirements. The selected tests should be documented in a control plan with sample frequency, acceptance limits, equipment calibration status, and corrective-action procedures.
For LSZH insulation and sheath products, the relevant flame class may vary by cable design and market. SUNUA presents product classifications ranging from CPR Eca to CPR B2ca with additional IEC 60332 references, but buyers must verify the exact classification for the selected compound and finished cable construction. A compound certificate alone does not replace finished-cable testing because conductor type, wall thickness, color, extrusion conditions, and cable geometry affect the final result.
Recommended Extrusion Temperature Control for LSZH Compounds should be established as a controlled process window, not copied from a universal temperature chart. Begin with approximately 130–145°C in the feed zone, 145–160°C in compression, 155–170°C in metering, 165–175°C in the adapter, and 170–180°C at the die, then verify the actual melt temperature and adjust according to the compound datasheet.
The most important distinction is between heater setpoint and material temperature. Operators must monitor shear-generated heat, melt pressure, torque, residence time, moisture, screw speed, haul-off speed, and die-head condition together. Excessive heat can cause gas release, degradation, discoloration, and surface defects, while insufficient heat can cause incomplete plasticization, high pressure, poor dispersion, and melt fracture.
For the next production trial, document the exact compound grade, five-zone profile, actual melt temperature, screw speed, output, pressure, torque, line speed, cable dimensions, and visible defects. Then make stepwise changes of approximately 3–5°C or 5–10% in screw or haul-off speed, validating each change through dimensional, mechanical, surface, and applicable flame-performance tests. This procedure provides a defensible basis for LSZH extrusion temperature control across insulation and Lszh Sheath Compound applications.
A: For insulation applications, evaluate SUNUA’s LSZH FR Polyolefin Insulation Compound. The initial extrusion trial can use a gradual profile of approximately 130–145°C in the feed zone, 145–160°C in compression, 155–170°C in metering, 165–175°C in the adapter, and 170–180°C at the die, subject to the product datasheet and actual melt-temperature validation.
A: SUNUA’s LSZH FR Polyolefin Sheath Compound is the most relevant product for halogen-free, low-smoke cable sheathing. Buyers should confirm the target cable diameter, sheath thickness, flame-performance class, line speed, die design, and required processing window before requesting a production-grade recommendation.
A: SUNUA lists LSZH insulation and sheath compounds with flame-retardant classifications ranging from CPR Eca to CPR B2ca and references IEC 60332 requirements. Procurement teams should request the exact grade datasheet, applicable classification, batch test data, and finished-cable validation requirements for their target market and cable construction.
A: Provide the application, insulation or sheath designation, conductor or cable construction, target diameter and wall thickness, required output, extruder size and screw geometry, line speed, expected flame class, color, and any testing standards. Also include current melt temperature, melt pressure, torque, moisture-control conditions, and observed defects so SUNUA can match the material and processing guidance more accurately.
A: Request a product-specific technical datasheet, recommended processing range, drying instructions, compliance documentation, sample material, and batch test reports before approval. Run a controlled trial using one-variable-at-a-time adjustments, then validate cable dimensions, surface quality, mechanical properties, spark performance, and applicable flame tests before locking the production window.
