IR
IR is a synthetic cis-1,4-polyisoprene elastomer with the same backbone as natural rubber, supplied as gum, carbon-black-filled or peroxide-cured compounds and in medical, FDA and latex grades.
Reference datasheet — IR is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the GUM condition
IR grades and fills
IR is supplied in 9 conditions, soft to hard. GUM is the default FabDigit quotes; the values on this page are for it.
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 | |
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 |
Supply forms, finishes and certifications
Ways IR is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
FDA | Food-contact / white non-marking compound | Certification |
MED | Medical / pharmacopoeia grade | Certification |
AO | Antiozonant / weather-stabilized compound | Grade option |
What is IR?
IR is a synthetic cis-1,4-polyisoprene elastomer with the same backbone as natural rubber, supplied as gum, carbon-black-filled or peroxide-cured compounds and in medical, FDA and latex grades. It is chosen for high elongation (750 %) and 22 MPa tensile strength with more consistent purity and lower non-rubber content than NR, in moulded seals, extruded tubing, pharmaceutical closures and dipped latex goods. Density is 0.93 g/cm³ and service is limited to about 80 °C, with poor resistance to oils, fuels and ozone; NBR or CR suit oil service, and natural rubber remains cheaper where building tack matters. IR has a density of 0.93 g/cm³ (0.0336 lb/in³), lighter than 78% of polymer grades. Its glass-transition temperature is -70°C (-94 °F). IR has a tensile strength of 22 MPa (3.19 ksi), weaker than 69% of polymer grades. Elongation at break is 750% and the elastic modulus is 0 GPa (2.61×10⁻⁴ Msi).
What is IR used for?
- medical tubing
- pharmaceutical stoppers
- tires
- adhesives
Advantages
- Ductile — tolerates forming and impact — 750%, better than 99% of polymer grades
- Forms and bends easily — 95/100, better than 99% of polymer grades
- Lightweight — 0.93 g/cm³ (0.0336 lb/in³), better than 78% of polymer grades
Limitations
- Needs corrosion protection — 50/100, worse than 97% of polymer grades
- Low stiffness — 0 GPa (2.61×10⁻⁴ Msi), worse than 96% of polymer grades
- Difficult to machine — 25/100, worse than 93% of polymer grades
- High mold shrinkage — 2.3%, worse than 89% of polymer grades
- Degrades in UV without stabilisers — 20/100, worse than 88% of polymer grades
IR properties
Typical room-temperature values for IR-GUM; bars are the position among polymer grades.
Physical4
IR has a density of 0.93 g/cm³ (0.0336 lb/in³), lighter than 78% of polymer grades. Its glass-transition temperature is -70°C (-94 °F).
Mechanical9
IR has a tensile strength of 22 MPa (3.19 ksi), weaker than 69% of polymer grades. Elongation at break is 750% and the elastic modulus is 0 GPa (2.61×10⁻⁴ Msi).
Thermal8
IR is rated for continuous service to 80°C (176 °F). It conducts heat at 0.14 W/m·K (0.0809 BTU/hr·ft·°F), worse than 81% of polymer grades. Thermal expansion is 220 µm/m·K (122.2 µin/in·°F).
Electrical5
IR is an electrical insulator with a dielectric strength of 22 kV/mm (558.8 V/mil) and a resistivity of 1×10¹³ Ω·m.
Chemical & Environmental3
Corrosion resistance is fair (50/100), worse than 97% of polymer grades. UV resistance is poor.
Sustainability4
Producing a kilogram of IR 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's machinability is poor (25/100, worse than 93% of polymer grades); formability excellent (95/100).
Common Calculations4
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the polymer family
Yield strength against density for every polymer grade FabDigit runs. IR is highlighted; hover a dot for its name, or open the interactive family chart.
Working with IR
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.
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) |
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.
How much does IR cost?
IR is a standard-cost polymer ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
IR — frequently asked
What is IR used for?
IR is typically used for medical tubing, pharmaceutical stoppers, tires and adhesives. In short: high-purity synthetic natural rubber; 750 % elongation elastomer; medical and FDA grades.
What is the tensile strength of IR?
IR has a typical tensile strength of 22 MPa (3.19 ksi) — weaker than 69% of polymer grades. Strength varies by condition: see the 9 listed tempers.
Is IR easy to machine?
Not especially — machinability is rated poor (25/100, worse than 93% of polymer grades). Vulcanised IR is cut rather than machined: use waterjet, steel-rule die cutting or sharp thin blades at low speed with water lubrication. Freeze or back up the part to limit heat build-up and blade sticking.
Can IR be welded?
Not melt-weldable. Splice with uncured gum stock and re-vulcanise, or bond cured parts with cyanoacrylate or chloroprene contact adhesive after halogenation or plasma treatment of the surface.
What surface finishes work on IR?
Cryogenic deflashing is standard; chlorination reduces surface friction and silicone oil or specialty inks can be applied. Surfaces are prone to ozone cracking, so use antiozonant (AO) compounds or a protective coating for outdoor service.
Can IR be formed, bent or molded?
Compound on an open mill or internal mixer, then calender, extrude, or injection/compression mould and cure at mould temperatures of 150–190 °C. Watch scorch time and allow roughly 2 % mould shrinkage in tool sizing.
What is the maximum service temperature of IR?
IR is rated for continuous use to about 80°C (176 °F), and briefly to 110°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does IR cost?
IR is a standard-cost polymer ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
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; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.