TPE — Thermoplastic Elastomer
Thermoplastic Elastomer
TPE (thermoplastic elastomer), of the styrenic or TPV type (Santoprene, Thermolast K, Dryflex), combines the elasticity of rubber with the processability of thermoplastics. Soft and recyclable, it is the reference for overmolding and soft-touch parts (grips, seals, handholds).
- Mold temperature: 20-50°C
- Melt temperature: 180-230°C
- Shrinkage: 0.5-2.0%
- Density: 0.90-1.25
- Manufacturer grades: Santoprene 101-73 (Celanese), Thermolast K (Kraiburg TPE), Dryflex (HEXPOL)
Processing
TPE generally requires little or no drying depending on the grade, which simplifies processing. Run the melt between 180 and 230 °C with a mold regulated between 20 and 50 °C. Its low viscosity and softness demand good mold clamping and well-designed vents to avoid flash, and special care for adhesion during two-shot overmolding.
Advantages
- Rubber elasticity with thermoplastic processing
- Ideal for overmolding and soft-touch surfaces
- Recyclable, unlike vulcanized rubbers
- Wide Shore A hardness range depending on the grade
Limitations
- Soft, low-viscosity material: prone to flash
- Lower temperature and creep resistance than vulcanized elastomers
- Overmolding adhesion to validate against the substrate
- Limited mechanical strength of the softest grades
Common injection molding defects
- Flash — Soft, low-viscosity material: lower pressure, improve mold clamping and venting
- Weld lines — Cooled melt front: raise melt temperature and injection speed
- Sink marks — On thick sections: increase holding pressure and time
Typical applications
Grips, seals, overmolding, flexible parts, handles