How Thermoplastic Elastomer (TPE) Properties Define Product Performance

What Are Thermoplastic Elastomers?

Thermoplastic Elastomers (TPEs) are a class of materials that combine the elastic, rubber-like performance of vulcanized thermoset rubbers with the processing versatility of thermoplastics — providing the best of both worlds. Unlike conventional rubber, which must be permanently cross-linked (vulcanized) during manufacturing, TPEs are physically cross-linked through phase separation—meaning they can be melted, reprocessed, and recycled like any thermoplastic while behaving like soft, flexible rubber at service temperatures.

This unique combination of processability and rubber-like performance has made TPEs one of the fastest-growing material families in the polymer industry — replacing thermoset rubbers in countless applications where recyclability, reduced manufacturing complexity, and design flexibility are valued.

How TPEs Work — The Physical Cross-Link Mechanism

Most TPEs derive their rubber-like behavior from a two-phase microstructure:

• Hard segments (blocks): Provide dimensional stability and physical cross-linking — typically crystalline or glassy domains that remain rigid at service temperature
• Soft segments (blocks): Provide elasticity and flexibility — typically amorphous, low-Tg domains that are above their glass transition at room temperature

When the TPE is heated above the hard segment’s melting or softening point, both phases soften — the material flows like a thermoplastic. It can be processed by injection molding, extrusion, or blow molding. Upon cooling, the hard segments re-solidify and reform physical cross-links — restoring rubber-like behavior without any chemical vulcanization reaction.

Major TPE Families

Styrenic Block Copolymers (SBC — SBS, SEBS, SIS)

The largest TPE family by volume. Polystyrene hard segments and polybutadiene (SBS), polyisoprene (SIS), or hydrogenated polyethylene/polybutylene (SEBS) soft segments.

SBS (Styrene-Butadiene-Styrene): Lower cost — used in footwear, adhesives, bitumen modification, and film applications. Susceptible to UV and oxidative degradation without stabilization.

SEBS (Styrene-Ethylene-Butylene-Styrene): Hydrogenated version of SBS — significantly better heat, UV, and chemical resistance. Used in overmolding, medical devices, soft-touch grips, and automotive seals.

Thermoplastic Polyurethanes (TPU)

Urethane hard segments and polyester or polyether soft segments. High-performance TPE with excellent abrasion resistance, oil resistance, and mechanical properties. Used in footwear soles, hose and tubing, automotive instrument panels, film, and medical device components.

Thermoplastic Vulcanizates (TPV)

Dynamically vulcanized blends of rubber (EPDM) and thermoplastic (PP) — the rubber phase is fine-dispersed and partially cross-linked during melt blending. TPVs (e.g., Santoprene®) offer better heat, compression set, and fluid resistance than SBC TPEs — used in automotive seals, weather-stripping, and industrial hose applications.

Copolyester Elastomers (COPE/TPC-ET)

Polybutylene terephthalate hard segments and polyether or polyester soft segments (e.g., Hytrel®). High-performance TPE with excellent heat resistance (continuous use to 150°C+), chemical resistance, and fatigue endurance. Used in automotive CV joint boots, pneumatic tubing, wire, and cable jacketing.

Polyamide-Based TPEs (PEBA/TPA)

Polyamide hard segments and polyether soft segments (e.g., PEBAX®). Unique combination of low density, low-temperature flexibility, and chemical resistance. Used in ski boots, running shoe midsoles, catheters, and fine-pitch wiring.

Key Properties and Testing of TPEs

Hardness (ASTM D2240 — Shore A and Shore D)

The primary performance specifications for TPE are Shore A (0–100 for softer grades) and Shore D (for harder grades). Hardness governs the tactile feel, grip, and deformation resistance of TPE products. Testing at ambient and elevated temperatures characterizes the hardness-temperature relationship.

Tensile Properties (ASTM D412, D638)

Tensile strength, elongation at break, and modulus — critical for applications where TPEs experience stretching forces. ASTM D412 (elastomeric materials) is preferred for softer, more elastic TPE grades; ASTM D638 for harder, stiffer grades.

Compression Set (ASTM D395)

Measures permanent deformation after sustained compression — the most important test for TPE seals, gaskets, and vibration isolators. Low compression set indicates good elastic recovery. TPVs exhibit significantly greater compression-set resistance than SBC TPEs at elevated temperatures.

Tear Strength (ASTM D624)

Die C and die B tear strength — characterizing resistance to tearing from a nick or defect initiation point. Critical for TPE hoses, tubing, and thin-walled components subject to sharp-edge contact.

Heat Resistance

Oven aging (ASTM D573): Tensile properties before and after heat aging at a defined temperature and time — quantifying thermal degradation. TPUs and COPEs maintain properties up to 150 °C; SBS degrades significantly above 80°C.

Vicat Softening Point (ASTM D1525): Upper service temperature indicator for harder TPE grades.

Chemical and Fluid Resistance (ASTM D471, D543)

TPE compatibility with specific service fluids (oils, fuels, solvents, cleaning agents) — critical for automotive seals, industrial hoses, and chemical handling applications.

Low-Temperature Flexibility

Brittleness Temperature (ASTM D746): The temperature at which the TPE specimen fractures under impact — the lower limit for cold-temperature applications.

TR-10 (ASTM D1329): Temperature at which 10% retraction of a stretched specimen occurs — a practical low-temperature performance indicator for TPE seals and tubing.

Industry Applications

Automotive: TPV weather-stripping, TPU instrument panel skins, SEBS overmolded grips, COPE CV joint boots, and PEBA fuel line hoses exploit each TPE family’s specific combination of seal performance, heat resistance, and processing economy.

Medical Devices: SEBS and TPU medical-grade compounds are used for catheter tubing, syringe components, and device overmolding — combining biocompatibility, sterilization resistance, and processing flexibility.

Consumer Products: Soft-touch grips on power tools, toothbrush handles, remote controls, and sporting goods use SEBS or TPV overmolding for ergonomic tactile performance.

Wire and Cable: COPE and TPU jacketing for industrial control cables, data cables, and automotive wiring provides flexibility, abrasion resistance, and temperature performance in a recyclable material system

Conclusion

Thermoplastic elastomer (TPE) testing — incorporating methods such as ASTM D2240, D412/D638, D395, D624, D573, and D471 — provides a comprehensive evaluation of mechanical performance, thermal stability, chemical resistance, and elastic recovery across diverse TPE families. These tests ensure that materials meet application-specific requirements for flexibility, durability, and environmental resistance in automotive, medical, consumer, and industrial applications. Selecting the appropriate testing protocols based on TPE type, service conditions, and performance expectations is essential to ensure reliable material behavior and product quality, making the testing strategy as important as the performance results themselves.

Why Choose Infinita Lab for TPE Testing?

Infinita Lab is a leading provider of thermoplastic elastomer testing services — hardness, tensile, compression set, tear, heat aging, chemical resistance, and low-temperature testing — across its vast network of 2,000+ accredited partner labs in the United States. With access to over 10,000 test types and a Single Point of Contact model, Infinita Lab accelerates your TPE material qualification and product development programs.

Looking for a trusted partner to achieve your research goals? Schedule a meeting with us, send us a request, or call us at (888) 878-3090 to learn more about our services and how we can support you. Request a Quote.

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