How to Process TPE Particles in Injection Molding and Extrusion

2026-06-04 10:05:35

　　Processing TPE (Thermoplastic Elastomer) particles in injection molding and extrusion requires attention to their unique properties: they are shear-sensitive, require low compression, and have high viscosity melt.

　　Below is a step-by-step guide for both processes.

　　1. General Pre-Processing (Common to Both)

　　Drying

　　Most TPEs are not hygroscopic, but some grades (e.g., SEBS-based) may absorb surface moisture.

　　Rule of thumb: Dry if exposed to humidity > 70% or stored > 6 months.

　　Drying conditions: 60–80°C (140–176°F) for 2–4 hours.

　　Avoid overdrying – can degrade soft TPEs.

　　Material Handling

　　Use low-shear conveying (vacuum or gentle auger).

　　Avoid contamination with PVC, oils, or dissimilar polymers.

　　2. Processing TPE in Injection Molding

　　Machine Setup

　　ParameterTypical Range

　　Barrel temp (feed zone)160–200°C (320–392°F)

　　Barrel temp (metering)180–220°C (356–428°F)

　　Nozzle temp180–210°C (356–410°F)

　　Mold temp20–60°C (68–140°F) – depends on hardness

　　Back pressureLow: 2–7 bar (30–100 psi)

　　Screw speedLow to moderate: 40–80 rpm

　　Soft TPEs (shore A < 40) → lower temperatures (140–180°C) to avoid degradation.

　　Injection Parameters

　　Injection speed: Medium to fast – helps fill thin walls, but avoid jetting.

　　Hold pressure: Low to medium – excessive pressure causes flash.

　　Screw cushion: 2–5 mm to prevent compression degradation.

　　Mold Design Tips

　　Venting: Essential – 0.02–0.04 mm depth (TPEs outgas).

　　Draft angles: 2–3° for soft, 1–2° for hard TPE.

　　Gate type: Fan or edge gate preferable to tunnel gate (soft TPE can shear).

　　Troubleshooting

　　ProblemLikely CauseFix

　　FlashToo high injection pressureReduce hold pressure

　　Splay marksMoisture or degraded meltDry material, lower barrel temp

　　Poor surface finishLow mold tempIncrease to 30–50°C

　　3. Processing TPE in Extrusion (Profile, Sheet, Tubing)

　　Extruder Setup

　　ParameterTypical Range

　　Barrel zones150–200°C (302–392°F)

　　Adapter & die170–210°C (338–410°F)

　　Screw design24:1–30:1 L/D, low compression ratio (2:1 to 2.5:1)

　　Screw speed20–60 rpm (higher for small diameter)

　　Melt temp180–200°C (max 230°C for some alloys)

　　Critical Points

　　Use a metering screw – mixing screws can over-shear TPE.

　　Screen pack: 40–80 mesh – prevents unmelted particles.

　　Cooling: Water bath (10–25°C) – support soft extrusions to prevent stretching.

　　Die & Haul-Off

　　Die land length: Short (2–5 mm) to reduce pressure drop.

　　Haul-off speed: Match extruder output exactly – TPEs stretch easily.

　　Air wipe before water bath – helps dimensional stability for soft TPEs.

　　Troubleshooting

　　ProblemLikely CauseFix

　　Melt fractureHigh shear rateLower screw speed, larger die gap

　　Dimensional variationUneven cooling or haul-offAdjust cooling length, use caterpillar puller

　　Surface sharkskinDie exit stressIncrease die temp, reduce output

　　4. Key Differences Between Injection & Extrusion for TPE

　　AspectInjection MoldingExtrusion

　　Screw compression1.5:1 – 2:12:1 – 2.5:1

　　Back pressureLow (2–7 bar)Not used

　　CoolingMold cooling (fast)Water bath (gradual)

　　Shear sensitivityModerate (short cycle)High (continuous)

　　Regrind useUp to 30% (if same grade)Up to 20% (risk of gel)

　　5. Safety & Quality Notes

　　Regrind: Can be reused if not thermally degraded – dry before reuse.

　　Color matching: TPEs absorb pigment differently than rigid thermoplastics – use TPE-specific masterbatch.

　　Purge material: Use LDPE or dedicated TPE purging compound – avoid polypropylene (can leave residues).

　　Would you like a printable checklist or specific settings for a common TPE grade (e.g., SEBS, TPU, or TPV)?