TR-10 Elastomer Testing: How Temperature Retraction Predicts Cold Sealing
What TR-10 means for O-Rings and rubber seals: ASTM D1329 / ISO 2921 test method, how to read TR-10 and TR70, static vs dynamic cold limits, and typical values by elastomer family.
TR-10 is the cold number seal people trust most for O-Rings. It comes from a temperature-retraction test that asks a simple question: after you stretch rubber, freeze it, and warm it back up, at what temperature does it start acting like rubber again?
Catalog “minimum temperature” claims often start from TR-10. Some bake in a static margin. Some do not. Reading the raw TR-10 keeps cold gland design honest.
This article expands the TR-10 section in the O-Ring Temperature Guide into a full working explanation: what the test measures, how engineers use it for static and dynamic seals, and how common elastomer families typically compare.
Temperature Guide Material Pages Ask About a Compound
Why low-temperature elasticity matters for seals
Rubber seals because polymer chains can move and push back against the gland. Cold slows that motion. Keep cooling and the compound passes from rubbery behavior into a stiff, plastic-like state. Squeeze force falls. A dynamic lip can crack. A static cover that sealed at room temperature can start to weep after a cold soak and a pressure cycle.
Kinetic elasticity is time and temperature dependent. Crystallization in some polymers complicates the picture further: deformation and dwell at cold temperature can grow ordered regions that delay recovery. A single “brittle point” number does not capture all of that. Temperature retraction does a better job of ranking compounds for compression seals.
What TR-10 is
TR-10 (also written TR10) is the temperature at which a frozen, elongated specimen has retracted 10% of its stretch while warming under the temperature-retraction procedure in ASTM D1329 (and the closely related ISO 2921).
In plain language: TR-10 is where the compound is waking up from the cold. It is beginning to regain resiliency and move from soft-plastic behavior back toward rubber behavior.
Labs also report TR70 (70% retraction). The gap between TR-10 and TR70 tends to widen when a vulcanizate has a stronger tendency to crystallize. TR70 also correlates with low-temperature compression set. TR-10 correlates usefully with brittle-point ranking among polymers of similar type, and the overall retraction rate tracks low-temperature flexibility for both crystallizing and non-crystallizing rubbers.
Temperature-retraction curve (schematic)
As the frozen specimen warms, it recovers stretch. TR-10 is 10% retraction; TR70 is 70%. A wider TR-10–TR70 gap often points to stronger crystallization tendency.
Schematic shape only. Real curves and absolute temperatures depend on the compound and stretch condition (for example TR10/50).
How the TR-10 test works
The procedure is a controlled stretch–freeze–release–warm cycle:
TR-10 test sequence
ASTM D1329 / ISO 2921 temperature-retraction method. Stretch percentage belongs on the report (for example TR10/50).
- 1 Stretch Elongate the specimen (commonly 50%; some methods use 25% or other values).
- 2 Freeze & lock Hold it elongated and cool below the temperature where it can recover.
- 3 Release Free one end. While the rubber is still rigid, it stays elongated.
- 4 Warm Raise chamber temperature at a uniform rate while recording length.
- 5 Read TR-10 / TR70 TR-10 = 10% retraction. TR70 = 70% retraction on the same warm-up curve.
Specimen notes (typical practice)
- Die-cut strips from a cured slab are the usual laboratory path.
- Thickness is commonly about 2.0 mm ± 0.2 mm.
- Working length is often in the 1.5–2.0 in range, limited by elongation and the fixture.
- Run at least three specimens per compound for a usable average.
- Some labs can run the method on finished O-Rings within size limits (for example, modest cross-section and sufficient ID), which is useful when you need data on the actual seal geometry.
Stretch percentage belongs on the report (for example TR10/50). Modulus and specimen geometry can influence results, so compare like with like when you rank compounds.
How seal engineers use TR-10 in practice
Industry practice for O-Rings and similar compression seals:
Duty reading of TR-10
Dynamic duty treats TR-10 as the working floor. Static, low-pressure duty often allows a modest colder band.
TR-10 = working floor
Treat TR-10 as a conservative limit. Plan for useful sealing near TR-10 and warmer. Rods, shafts, and pressurized cycles leave little room colder than the measured value.
Often 10–15°F colder
Many compounds still seal roughly 10–15°F (about 8°C) colder than TR-10 on quiet lids and low-pressure static glands. Confirm the grade before banking on that margin.
Catalog check: Some houses summarize the static rule as “TR-10 in °F minus about 10°F.” Others use a 10–15°F (about 8°C) band. Ask whether a published low-temp rating is raw TR-10 or TR-10 with a static margin already subtracted.
Design takeaways
- Cold start after a long soak is harder than a brief chill with the machine still warm.
- Pressure and motion move you toward the TR-10 floor sooner than a quiet static lid.
- Fluid swell can change cold behavior; a TR-10 measured on dry rubber is a starting point, not a full service proof.
- Pair TR-10 with gland design: squeeze, stretch, and extrusion gap still matter when the rubber is stiff.
Typical TR-10 values by elastomer family
The chart below shows approximate commercial midpoints on a fixed scale from −70°C to 0°C. Longer bars mean colder (lower) TR-10. Real compounds inside a family scatter. Low-temperature NBR, GLT-type FKM, and specialty silicones can sit well colder than “standard” grades in the same polymer family. Always use the grade datasheet.
Typical TR-10 by elastomer family
Approximate commercial midpoints. Bar length = coldness on a −70°C → 0°C scale. Color: blue (colder TR-10) → teal → green → amber → red (warmer TR-10).
Width % = |TR-10| ÷ 70 on a −70°C to 0°C scale. Color runs cold (blue) → warm (red). Use grade datasheet values for design.
| Family | Typical TR-10 midpoint | Cold-sealing notes |
|---|---|---|
| Silicone (VMQ) | −60°C (−76°F) | Excellent cold flexibility; watch tear, abrasion, and permeation in dynamic glands |
| Fluorosilicone (FVMQ) | −55°C (−67°F) | Cold flex with better fuel/oil resistance than silicone; still a softer family |
| EPDM | −45°C (−49°F) | Strong cold performer for water, steam, and many polar fluids |
| NBR (low-temp grades) | −40°C (−40°F) | Specialty recipes reach much colder than general-purpose nitrile |
| FKM (GLT-type) | −35°C (−31°F) | Low-temp fluorocarbon option when oil/fuel resistance must stay |
| Neoprene (CR) | −35°C (−31°F) | Solid outdoor / refrigerant heritage; confirm grade |
| NBR (general) | −25°C (−13°F) | Everyday oil service; cold limit is often the design constraint |
| HNBR | −25°C (−13°F) | Tougher and hotter than NBR; cold capability is grade-dependent |
| FKM (standard) | −17°C (1°F) | Hot oil and chemical strength; cold is the tradeoff unless you specify a low-temp grade |
| FFKM | −10°C (14°F) | Extreme chemistry first; cold grades exist but vary widely |
| Aflas® (FEPM) | −5°C (23°F) | Steam / amine / sour-service strengths; not a deep-cold specialist |
Once chemistry picks the family (oil, steam, solvent, vacuum), TR-10 testing across candidate compounds in that family is how you finish the cold selection.
TR-10 compared with other cold tests
| Test | What it measures | Best use for seals |
|---|---|---|
| TR-10 (ASTM D1329 / ISO 2921) | Temperature where stretched rubber recovers 10% on warm-up | Primary cold guide for O-Ring and compression-seal selection |
| Glass transition Tg (e.g. DSC) | Polymer transition toward glassy behavior | Materials science baseline; less direct than TR-10 for gland recovery |
| Brittleness / crack tests (e.g. ASTM D2137) | Impact fracture while cold | Abuse and shatter risk; incomplete for squeeze sealing alone |
| Low-temp compression set | Permanent set after cold compression | Complements TR70 / recovery stories for static lids |
For O-Rings, TR-10 sits closest to the question you actually care about: will the rubber push back in the groove when it is cold?
Reading a datasheet without getting fooled
- Find TR-10 and the stretch condition (for example /50).
- Check whether the marketed “minimum temperature” equals TR-10 or TR-10 minus a static allowance.
- Look for TR70 or a TR-10–TR70 gap when crystallization is a concern.
- Match compound grade, not only polymer family.
- Confirm fluid and heat alongside cold. A great TR-10 in the wrong oil is still a failed seal. Use the Chemical Compatibility Chart and Shore A Hardness guidance with the temperature story.
Practical selection checklist
- Write down the coldest soak and whether the seal is static or dynamic.
- Shortlist families that survive the fluid and heat.
- Compare TR-10 (and TR70 when available) on the shortlisted grades.
- For static lids, a modest margin colder than TR-10 may be acceptable; for rods, shafts, and pressurized cycles, stay near TR-10 and warmer.
- Validate critical applications with the real compound in the real gland. Datasheet TR-10 is a ranking tool, not a substitute for application testing.
Quick answers
What does TR-10 mean?
It is the temperature at which a stretched, frozen elastomer specimen has retracted 10%
of its elongation during controlled warm-up in the ASTM D1329 / ISO 2921 temperature-
retraction test.
Is TR-10 the same as the lowest sealing temperature?
For dynamic or pressurized duty, treat TR-10 as a practical floor. For static, low-
pressure duty, many compounds still seal about 10–15°F (about 8°C) colder. Confirm
how your datasheet defines its published minimum.
Why do two FKM grades have different TR-10 numbers?
Polymer architecture and compounding change cold recovery. Low-temperature FKM grades are
built for colder TR-10 while holding fluorocarbon fluid resistance. Family name alone is
not enough.
Where should I go next?
Start with the Temperature Guide, then the
material pages for
Nitrile,
EPDM,
FKM / Viton®,
Silicone, and
Fluorosilicone.
Contact The O-Ring Store with fluid, pressure, static vs dynamic
duty, and the coldest temperature you must survive.
TR-10 values and temperature ratings vary by compound. Use grade-specific data for design decisions, and validate critical seals under the real fluid, pressure, and cold-soak profile.
