描述
Santoprene 251-70W232 is a soft, colorable, flame-retardant thermoplastic vulcanizate from Celanese developed for applications requiring elastomeric flexibility together with enhanced fire performance.
The grade belongs to the Santoprene flame-retardant TPV family and is specifically recommended for applications requiring a UL 94 vertical flame rating. Celanese’s current Product Finder lists Santoprene 251-70W232 as a Natural 75 Shore A flame-retardant grade with UL 94 V-0 performance.
Current grade data lists approximately:
- 75 Shore A hardness
- 550% elongation at break
- 6.3 MPa tensile stress at break
- 2.7 MPa tensile stress at 100% elongation
- 1.270 g/cm³ density
This combination allows the material to remain highly flexible while providing substantially improved flame performance compared with general-purpose TPV grades.
Santoprene 251-70W232 uses a non-ether brominated flame-retardant system and the current Celanese description explicitly states that the grade does not contain metal deactivators.
The material also provides good fluid resistance, making it useful for electrical, automotive and industrial environments where the component may encounter oils, fluids or environmental exposure.
Celanese specifically recommends this grade for applications requiring:
- Flame retardancy
- Excellent flex-fatigue resistance
- Excellent ozone resistance
Santoprene 251-70W232 is shear dependent and can be processed on conventional thermoplastic equipment through injection molding, extrusion or blow molding.
Current Materials Database information also lists multi-injection molding and sheet extrusion.
For more TPV products, visit our TPV Thermoplastic Vulcanizates Product Category →.
For the current Celanese TPV portfolio, see the Official Celanese Santoprene & Geolast Product Finder →.
Key Features of Santoprene 251-70W232
| Feature | Engineering Benefit |
|---|---|
| 75 Shore A Hardness | Provides a flexible but well-supported elastomeric response |
| UL 94 V-0 @ 1.5 mm | Strong vertical-flame performance for electrical and technical applications |
| UL 94 V-2 @ 1.0 mm | Published flame classification at thinner section |
| 550% Elongation at Break | Maintains very high deformation capability |
| 6.3 MPa Tensile Stress at Break | Provides useful mechanical strength |
| 2.7 MPa Stress at 100% Elongation | Supports flexible but controlled deformation |
| Non-Ether Brominated Flame Retardants | Provides flame-retardant functionality |
| Good Fluid Resistance | Useful in automotive and industrial environments |
| Excellent Flex-Fatigue Resistance | Suitable for repeatedly flexed parts |
| Excellent Ozone Resistance | Supports long-term environmental durability |
| Natural / Colorable | Allows customized product colors |
| UL Recognized | Current Celanese listings reference E80017 |
| Injection Moldable | Suitable for complex molded components |
| Extrudable | Suitable for profiles and sheets |
| Blow Moldable | Supports selected hollow components |
| Shear-Dependent Flow | Flow can be optimized through processing shear |
The defining value of Santoprene 251-70W232 is its combination of soft elastomeric flexibility and UL 94 V-0 flame retardancy.
Typical Applications for Santoprene 251-70W232
Santoprene 251-70W232 is particularly suitable for applications requiring both flexibility and flame resistance.
| Application Area | Typical Use |
|---|---|
| Electrical Components | Flexible insulating and protective parts |
| Cable Protection | Flexible boots, strain reliefs and protective sections |
| Connectors | Flame-retardant elastomeric connector components |
| Flexible Housings | Protective electrical and electronic enclosures |
| Telecommunications Equipment | Flexible technical parts requiring flame resistance |
| 5G Equipment Components | Selected flexible dielectric and protective parts |
| Automotive Electrical Parts | Flexible components near electrical systems |
| Appliance Components | Flame-retardant molded and extruded parts |
| Grommets | Cable and mechanical protection |
| Plugs & Covers | Flexible protective components |
| Industrial Electrical Equipment | Resilient protective elastomeric parts |
| Sheet Components | Flame-retardant flexible sheets |
| Blow-Molded Parts | Selected hollow flexible components |
Celanese has also included Santoprene 251-70W232 in its 5G-compatible material portfolio, listing approximately 2.29 dielectric constant at 37 GHz and 0.0014 dielectric loss at 37 GHz, together with UL 94 V-0 performance.
Typical Properties of Santoprene 251-70W232
Physical & Rheological Properties
| Property | Typical Value | Test Method |
|---|---|---|
| Density | 1270 kg/m³ / 1.270 g/cm³ | ISO 1183 |
| Shore A Hardness, 15 s | 75 | ISO 48-4 / ISO 868 |
| Molding Shrinkage – Parallel | 1.3% | ISO 294-4 / ISO 2577 |
| Molding Shrinkage – Normal | 0.6% | ISO 294-4 / ISO 2577 |
| Resin Identification | TPV | ISO 1043 |
| Part Marking Code | >TPV< | ISO 11469 |
| Product Form | Pellets | Manufacturer information |
| Appearance | Natural / Colorable | Manufacturer information |
The current 2024-12-03 Celanese Materials Database revision reports approximately 1.270 g/cm³ density, which is higher than older data sheets that listed 1.240 g/cm³. For your new page, I recommend using the newer 1.270 g/cm³ value.
Mechanical Properties
| Property | Typical Value | Test Method |
|---|---|---|
| Tensile Stress at 100% Elongation | 2.7 MPa | ISO 37 |
| Tensile Stress at Break | 6.3 MPa | ISO 527-1/-2 or ISO 37 |
| Elongation at Break | 550% | ISO 527-1/-2 or ISO 37 |
| Shore A Hardness | 75 | ISO 48-4 / ISO 868 |
These values show that Santoprene 251-70W232 retains substantial elastomeric flexibility despite its flame-retardant formulation.
Thermal Properties
| Property | Typical Value | Test Method |
|---|---|---|
| RTI Electrical, 1.5 mm | 90°C | UL 746B |
| RTI Electrical, 3.0 mm | 90°C | UL 746B |
| RTI Strength, 1.5 mm | 85°C | UL 746B |
| RTI Strength, 3.0 mm | 90°C | UL 746B |
| Tensile Strength Change, 150°C / 168 h | -21% | ISO 188 |
| Tensile Strain-at-Break Change, 150°C / 168 h | -25% | ISO 188 |
These current heat-aging values are listed in the latest Celanese Materials Database revision.
Flame Retardant Performance
Flame resistance is the primary technical differentiator of Santoprene 251-70W232.
UL 94 & Flammability
| Property | Typical Value | Standard |
|---|---|---|
| Burning Behavior @ 1.5 mm | V-0 | IEC 60695-11-10 / UL 94 |
| Burning Behavior @ 1.0 mm | V-2 | IEC 60695-11-10 / UL 94 |
| UL Recognition | Yes | UL 94 |
| Oxygen Index | 26% | ISO 4589-1/-2 |
| Hot Wire Ignition, 1.5 mm | PLC 3 | UL 746A |
The current Celanese Materials Database lists V-0 at 1.5 mm and V-2 at 1.0 mm.
That thickness distinction is important for product design because UL 94 performance can vary with specimen thickness.
Electrical Properties
| Property | Typical Value | Test Method |
|---|---|---|
| Relative Permittivity @ 60 Hz | 2.5 | IEC 62631-2-1 |
| Electric Strength, 2 mm | 31 kV/mm | ASTM D149 |
| Comparative Tracking Index | PLC 0 | UL 746A |
| Arc Resistance Performance Level | PLC 6 | UL 746B |
| High-Amperage Arc Ignition, 1.5 mm | PLC 0 | UL 746A |
| High-Voltage Arc Tracking Rate | PLC 2 | UL 746A |
These characteristics make the grade useful for flexible protective electrical and electronic components.
Flame-Retardant Formulation
Santoprene 251-70W232 contains non-ether brominated flame retardants.
Celanese also explicitly states that the grade:
does not contain metal deactivators.
This is an important formulation detail because the W232 designation should not be confused with the W236 grades used for copper/metal-catalyzed degradation stabilization.
In other words:
W232 = flame-retardant formulation
while the previously discussed W236 grades are associated with metal-stabilization for plumbing environments.
For Santoprene 251-70W232, the key selection reason is therefore UL 94 flame resistance, not potable-water or copper-stabilization performance.
Flex-Fatigue and Ozone Resistance
Celanese specifically recommends Santoprene 251-70W232 for applications requiring excellent flex-fatigue resistance.
This is useful for components repeatedly subjected to:
- Bending
- Compression
- Twisting
- Vibration
- Assembly movement
- Cable movement
The grade also provides excellent ozone resistance, supporting long-term use in environments where conventional elastomers may experience ozone-induced surface cracking.
This combination is particularly useful for electrical boots, flexible covers, grommets, cable protection and industrial elastomeric parts.
5G & High-Frequency Electrical Properties
Celanese has included Santoprene 251-70W232 in a Santoprene TPV 5G material selection guide.
Published 37 GHz data includes:
| Property | Typical Value | Test Method |
|---|---|---|
| Dielectric Constant @ 37 GHz | 2.29 | ASTM D2520 |
| Dielectric Loss @ 37 GHz | 0.0014 | ASTM D2520 |
The same guide identifies the grade as Colorable, UL 94 V-0, and bondable with PP under the referenced conditions.
These values may be useful for telecom, antenna-adjacent, cable-protection and high-frequency electrical applications.
Why Choose Santoprene 251-70W232?
The main reason to choose Santoprene 251-70W232 is its ability to combine flame resistance with elastomeric flexibility.
At approximately 75 Shore A, the material remains sufficiently soft for flexible housings, grommets, cable protection and resilient technical components.
Its approximately 550% elongation at break allows extensive deformation.
The typical 6.3 MPa tensile stress at break provides useful mechanical strength.
Most importantly, the grade reaches UL 94 V-0 at 1.5 mm, making it particularly relevant where vertical flame resistance is part of the material requirement.
Excellent flex-fatigue and ozone resistance further support applications exposed to repeated movement and environmental aging.
The grade also offers useful electrical characteristics, including approximately 31 kV/mm dielectric strength and PLC 0 comparative tracking index.
For customers requiring a colorable 75A flame-retardant TPV with UL 94 V-0 performance, Santoprene 251-70W232 is an important grade to evaluate.
Processing Guidelines for Santoprene 251-70W232
Current Celanese data lists the following processing methods:
- Injection molding
- Multi-injection molding
- Extrusion
- Sheet extrusion
- Blow molding
Current Grade-Specific Injection Conditions
The latest Celanese Materials Database revision dated 2025-04-21 gives the following guidance:
| Processing Parameter | Celanese Guidance |
|---|---|
| Drying Recommended | Yes |
| Drying Temperature | 80°C |
| Drying Time | ≥3 hours in a dehumidified dryer |
| Processing Moisture Content | ≤0.08% |
| Maximum Regrind Level | 20% |
| Optimum Melt Temperature | 200°C |
| Minimum Melt Temperature | 190°C |
| Maximum Melt Temperature | 210°C |
| Optimum Mold Temperature | 30°C |
| Minimum Mold Temperature | 10°C |
| Maximum Mold Temperature | 50°C |
These are newer than some older Santoprene 251-70W232 sheets that listed a broader optimum around 215°C, so for a new website page I recommend using the 2025 revised 200°C optimum / 190–210°C range.
Injection Molding Notes
Celanese indicates that holding pressure should generally be approximately 50–75% of actual injection pressure.
Processors should optimize:
- Injection speed
- Screw speed
- Holding pressure
- Back pressure
- Melt temperature
- Mold temperature
- Gate design
- Runner dimensions
- Venting
- Cooling time
- Part thickness
- Surface appearance
Extrusion Conditions
| Processing Parameter | Published Guidance |
|---|---|
| Drying Temperature | 82°C |
| Drying Time | 3 hours |
Current Materials Database information continues to recommend drying before extrusion.
General Processing Notes
Santoprene TPV is shear dependent.
The manufacturer also provides a broader Santoprene processing window of approximately 175–230°C, although the grade-specific 2025 injection guidance for 251-70W232 is narrower.
Material Compatibility
Santoprene TPV is incompatible with acetal (POM) and PVC.
Equipment should be thoroughly purged when switching between these materials and Santoprene 251-70W232.
Related Products
We supply Santoprene TPV grades for different flame-retardancy, hardness, electrical and processing requirements.
Typical Santoprene product families include:
- Santoprene 251 Series
- Santoprene flame-retardant TPV grades
- Santoprene electrical grades
- Santoprene telecom grades
- Santoprene 151 flame-retardant grades
- Santoprene general-purpose grades
- Santoprene specialty TPV grades
View More TPV Thermoplastic Vulcanizates →
If you need grade-selection support, send us your required UL flame rating, thickness, Shore hardness, electrical properties, processing method and application.
Technical Documents for Santoprene 251-70W232
| Document Type | Description |
|---|---|
| TDS | Current physical, mechanical, flame-retardant, electrical and processing data |
| SDS | Safety Data Sheet |
| UL Information | QMFZ2.E80017 / QMFZ8.E80017 recognition |
| UL 94 Information | V-0 at 1.5 mm and V-2 at 1.0 mm |
| Electrical Data | Dielectric strength, CTI and arc-resistance information |
| Processing Guide | Injection molding, extrusion and blow-molding guidance |
| Santoprene Product Finder | Celanese grade portfolio and positioning |
| COA | Batch-specific quality information where available |
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FAQ About Santoprene 251-70W232
Q1: What is Santoprene 251-70W232?
Santoprene 251-70W232 is a soft, colorable, flame-retardant TPV from Celanese designed for applications requiring flexibility together with vertical-flame resistance.
Q2: What is the hardness of Santoprene 251-70W232?
The current typical hardness is approximately 75 Shore A.
Q3: Is Santoprene 251-70W232 UL 94 V-0?
Yes. Current Celanese data lists UL 94 V-0 at 1.5 mm.
Q4: What is the flame rating at 1.0 mm?
Current data lists approximately UL 94 V-2 at 1.0 mm.
Q5: What is the elongation at break?
The typical value is approximately 550%.
Q6: What is the tensile stress at break?
The typical tensile stress at break is approximately 6.3 MPa.
Q7: What is the tensile stress at 100% elongation?
The typical value is approximately 2.7 MPa.
Q8: What is the density?
The latest Celanese Materials Database revision lists approximately 1.270 g/cm³.
Q9: What flame retardants are used?
Celanese describes the grade as containing non-ether brominated flame retardants.
Q10: Does Santoprene 251-70W232 contain metal deactivators?
No. Current Celanese product information explicitly states that it does not contain metal deactivators.
Q11: Is Santoprene 251-70W232 resistant to ozone?
Yes. Excellent ozone resistance is one of the published key features.
Q12: Is it suitable for repeated flexing?
Yes. Celanese recommends the grade for applications requiring excellent flex-fatigue resistance.
Q13: Can Santoprene 251-70W232 be injection molded?
Yes. Injection molding and multi-injection molding are listed processing methods.
Q14: Can Santoprene 251-70W232 be extruded?
Yes. Extrusion and sheet extrusion are supported.
Q15: What injection melt temperature is recommended?
The latest 2025 Celanese Materials Database revision gives approximately 200°C optimum, with a grade-specific range of approximately 190–210°C.
Q16: What mold temperature is recommended?
The latest grade-specific guidance lists approximately 30°C optimum, with a range of approximately 10–50°C.
Request Santoprene 251-70W232 Price & Technical Support
For pricing, availability, technical documents or application support for Santoprene 251-70W232, please provide:
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- Electrical, automotive, appliance or telecom application
- Required UL flame rating
- Minimum wall thickness
- Required Shore hardness
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- Fluid or chemical exposure
- Injection-molding, extrusion or blow-molding process
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