IR A70
Hardness band
A70 = shore A 70
Pick Shore A 70 as the standard O-ring hardness for the best extrusion and abrasion resistance; modulus rises to about 6 MPa while resilience and elongation fall to 500 %.
Values for the A70 condition
Other IR grades and fills
IR is listed in 9 conditions; see the grade overview at IR.
Compare all 9 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Shore A 80 | Use the hard, high-filler Shore A 80 compound for high-pressure seals, backing plates and bushings; extrusion resistance is highest but elongation drops to 380 % and rebound is clearly lower. | — | 19 | 380 | 30 Shore D |
Shore A 40 | Choose the soft Shore A 40 compound for low-hardness seals, vibration isolators and flexible diaphragms that need up to 800 % elongation and maximum conformability to the mating surface. | — | 20 | 800 | 40 Shore A |
Peroxide-cured, low-extractable | Pick the peroxide cure with no sulfur or accelerators for pharmaceutical and electrical parts: low extractables and nitrosamine risk, better compression set, 20 MPa tensile and 90 °C service. | — | 20 | 650 | 50 Shore A |
GUMDefault Unfilled gum vulcanizate | Pick the unfilled sulfur-cured gum vulcanizate at Shore A 50 as the comparison baseline and for highly transparent, highly elastic parts: 22 MPa tensile, 750 % elongation, lowest heat build-up. | — | 22 | 750 | 50 Shore A |
Shore A 50 | Pick Shore A 50 as the default hardness for general seals and rubber stoppers, balancing elasticity, 23 MPa tensile strength and 700 % elongation with easy processing. | — | 23 | 700 | 50 Shore A |
A70This page Shore A 70 | Pick Shore A 70 as the standard O-ring hardness for the best extrusion and abrasion resistance; modulus rises to about 6 MPa while resilience and elongation fall to 500 %. | — | 23 | 500 | 22 Shore D |
Shore A 60 | Choose the Shore A 60 compound reinforced with carbon black or precipitated silica for O-rings and mounts that need both wear resistance and rebound; 25 MPa tensile, 600 % elongation. | — | 25 | 600 | 60 Shore A |
Synthetic polyisoprene latex | Pick the dipped synthetic latex film for surgical gloves, condoms and bladders that must avoid natural latex protein allergy; 950 % elongation and 27 MPa tensile, but only 70 °C service. | — | 27 | 950 | 35 Shore A |
Carbon-black reinforced | Choose the N330/N550 carbon-black reinforced compound when tensile, abrasion and tear resistance must be highest, as in tyre treads, rubber rollers and industrial goods; 28 MPa tensile. | — | 28 | 550 | 65 Shore A |
What is IR A70?
IR A70 is IR heat treated to A70 — pick Shore A 70 as the standard O-ring hardness for the best extrusion and abrasion resistance; modulus rises to about 6 MPa while resilience and elongation fall to 500 %. IR A70 has a tensile strength of 23 MPa (3.34 ksi), weaker than 69% of polymer grades. Elongation at break is 500% and the elastic modulus is 0.01 GPa (8.7×10⁻⁴ Msi). IR A70 has a density of 1.1 g/cm³ (0.0397 lb/in³), lighter than 66% of polymer grades. Its glass-transition temperature is -70°C (-94 °F). GUM is the default condition FabDigit quotes; A70 is available on request or by drawing note.
Advantages
- Ductile — tolerates forming and impact — 500%, better than 90% of polymer grades
Limitations
- Needs corrosion protection — 52/100, worse than 96% of polymer grades
- Degrades in UV without stabilisers — 20/100, worse than 88% of polymer grades
- Low stiffness — 0.01 GPa (8.7×10⁻⁴ Msi), worse than 86% of polymer grades
- Absorbs moisture — dry before molding — 1%, worse than 84% of polymer grades
- Difficult to machine — 40/100, worse than 82% of polymer grades
IR A70 properties
Typical room-temperature values for IR A70; 16 are specific to this condition. Other listed values are IR reference data and may not represent this condition. Bars are the position among polymer grades.
Physical4
IR A70 has a density of 1.1 g/cm³ (0.0397 lb/in³), lighter than 66% of polymer grades. Its glass-transition temperature is -70°C (-94 °F).
Mechanical9
IR A70 has a tensile strength of 23 MPa (3.34 ksi), weaker than 69% of polymer grades. Elongation at break is 500% and the elastic modulus is 0.01 GPa (8.7×10⁻⁴ Msi).
Thermal8
IR A70 is rated for continuous service to 80°C (176 °F). It conducts heat at 0.2 W/m·K (0.116 BTU/hr·ft·°F), worse than 56% of polymer grades. Thermal expansion is 220 µm/m·K (122.2 µin/in·°F).
Electrical5
IR A70 is an electrical insulator with a dielectric strength of 22 kV/mm (558.8 V/mil) and a resistivity of 1×10⁹ Ω·m.
Chemical & Environmental3
Corrosion resistance is fair (52/100), worse than 96% of polymer grades. UV resistance is poor.
Sustainability4
Producing a kilogram of IR A70 takes about 95 MJ of energy and emits 3.5 kg of CO₂ — less than 70% of polymer grades. Typical recycled content is 0%.
Manufacturability4
IR A70's machinability is fair (40/100, worse than 82% of polymer grades); formability very good (78/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with IR A70
Is IR easy to machine?
Vulcanised IR is cut rather than machined: use waterjet, steel-rule die cutting or sharp thin blades at low speed with water lubrication. Freeze or back up the part to limit heat build-up and blade sticking.
Can IR be welded?
Not melt-weldable. Splice with uncured gum stock and re-vulcanise, or bond cured parts with cyanoacrylate or chloroprene contact adhesive after halogenation or plasma treatment of the surface.
Can IR be formed, bent or molded?
Compound on an open mill or internal mixer, then calender, extrude, or injection/compression mould and cure at mould temperatures of 150–190 °C. Watch scorch time and allow roughly 2 % mould shrinkage in tool sizing.
What surface finishes work on IR?
Cryogenic deflashing is standard; chlorination reduces surface friction and silicone oil or specialty inks can be applied. Surfaces are prone to ozone cracking, so use antiozonant (AO) compounds or a protective coating for outdoor service.
IR chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| 3,4- and trans-polyisoprene unitsstructural defect units | 1 – 4 | 2 |
| sulfur (vulcanizing agent)compounded in phr; 0 in peroxide cure systems | 0.5 – 2.5 | 1.5 |
| zinc oxide + stearic acid (activator)phr | 3 – 6 | 5 |
| carbon black / silica filler0 in gum stocks; 30–50 phr in reinforced compounds | 0 – 50 | 0 |
| antioxidant / antiozonantphr, amine or phenolic type | 1 – 3 | 2 |
| cis-1,4-polyisoprene (isoprene monomer)Ti or Nd/Li solution polymerized; high cis strain-crystallizing | ≥ 96 (balance) | — |
IR A70 — frequently asked
What is IR A70 used for?
IR A70 is typically used for medical tubing, pharmaceutical stoppers, tires and adhesives. In short: high-purity synthetic natural rubber; 750 % elongation elastomer; medical and FDA grades.
What is the tensile strength of IR A70?
IR A70 has a typical tensile strength of 23 MPa (3.34 ksi) — weaker than 69% of polymer grades. Strength varies by condition: see the 9 listed tempers.
Is IR A70 easy to machine?
Not especially — machinability is rated fair (40/100, worse than 82% of polymer grades). Vulcanised IR is cut rather than machined: use waterjet, steel-rule die cutting or sharp thin blades at low speed with water lubrication. Freeze or back up the part to limit heat build-up and blade sticking.
Can IR A70 be welded?
Not melt-weldable. Splice with uncured gum stock and re-vulcanise, or bond cured parts with cyanoacrylate or chloroprene contact adhesive after halogenation or plasma treatment of the surface.
What surface finishes work on IR A70?
Cryogenic deflashing is standard; chlorination reduces surface friction and silicone oil or specialty inks can be applied. Surfaces are prone to ozone cracking, so use antiozonant (AO) compounds or a protective coating for outdoor service.
Can IR A70 be formed, bent or molded?
Compound on an open mill or internal mixer, then calender, extrude, or injection/compression mould and cure at mould temperatures of 150–190 °C. Watch scorch time and allow roughly 2 % mould shrinkage in tool sizing.
What is the maximum service temperature of IR A70?
IR A70 is rated for continuous use to about 80°C (176 °F), and briefly to 110°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- ASTM D2000 — Classification System for Rubber Products in Automotive Applications — ASTM (2020)
- ISO 1629 — Rubber and lattices: nomenclature — ISO (2013)
- GB/T 8657 (IR) — SAC (2019)
- Rubber Technology (Morton) / Science and Technology of Rubber — Springer / Elsevier (2013)
- ASM Engineered Materials Handbook Vol.2 — Engineering Plastics & Elastomers — ASM International (1988)
- Synthetic polyisoprene rubber grades (Kraton IR, Zeon Nipol IR, SIBUR SKI-3) — producers (2023)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.