TPE/TPV Santoprene: Overmolding & Soft-Touch Design Guide
Published: 2026-06-02
Thermoplastic vulcanizates (TPVs), such as Santoprene (Celanese), are dynamically vulcanized EPDM rubber particles dispersed in a polypropylene matrix. This structure provides rubber-like elasticity with thermoplastic processability — parts can...
Thermoplastic vulcanizates (TPVs), such as Santoprene (Celanese), are dynamically vulcanized EPDM rubber particles dispersed in a polypropylene matrix. This structure provides rubber-like elasticity with thermoplastic processability — parts can be injection molded with standard equipment, and scrap is fully recyclable. Santoprene is the dominant TPV for automotive weather seals, appliance gaskets, and soft-touch overmolding. Hardness ranges from 35 Shore A (very soft gel-like) to 50 Shore D (semi-rigid).
Overmolding design guidelines: TPV bonds well to PP via melt fusion (same matrix material); bonds poorly to PA66, POM, and PBT without mechanical interlock. Substrate surface temperature at the point of TPV injection must be above the TPV's crystallization temperature (~110°C) to achieve bond strength — this typically requires the rigid substrate mold temperature to be elevated 10-20°C above standard settings. For chemical bonding to engineering plastics (PA, PC/ABS, PBT), TPE-U (thermoplastic polyurethane) or TPE-E (COPE) grades offer superior adhesion to polar substrates.
Technical Properties
| Density | 0.97 g/cm³ |
|---|---|
| Tensile Strength | 5-15 MPa (grade dependent) |
| Melting Point | TPV: melt processable at 190-230°C |
| Shrinkage Rate | 1.5-2.5% |
| Flexural Modulus | 0.01-0.3 GPa |
| Hdt | Not applicable (elastomeric) |
Engineering Tool: Shrinkage & Cost Estimator
Calculate part weight, mold cavity dimensions accounting for shrinkage, and material cost — all locally in your browser.
Equivalents & Cross-References
| Equivalent / Alternate | Action |
|---|---|
| Santoprene | |
| Sarlink | |
| Forprene |
Frequently Asked Questions
Can Santoprene be overmolded onto nylon?
TPV (Santoprene) bonds poorly to PA66/PA6 — the PP matrix is non-polar and does not form chemical bonds with nylon's polar amide groups. Specify TPE-U (polyurethane TPE, e.g., Desmopan) or TPE-E (copolyester TPE, e.g., Hytrel) for overmolding onto nylon, PC, or ABS substrates.
What is the maximum service temperature for Santoprene?
Santoprene grades are rated for continuous use at 135°C (general purpose) to 150°C (high-heat grades). Above these temperatures, the PP matrix softens and the EPDM rubber phase accelerates oxidative degradation. Short-term exposure to 165°C is acceptable for minutes (e.g., paint bake ovens).
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References & Industry Standards
- ASTM International. Standard Specifications for Engineering Plastics & Thermoplastics. astm.org
- UL Prospector. Plastics & Elastomers Material Database. ulprospector.com
- MatWeb. Material Property Data for Engineering Thermoplastics. matweb.com
- ISO 1043. Plastics — Symbols and Abbreviated Terms. iso.org