IIR A40
Hardness band
ASTM CIIR, BIIR
A40 = shore A 40
Soft gaskets, damping pads and low-clamp-force seals.
Values for the A40 condition
Other IIR grades and fills
IIR is listed in 10 conditions; see the grade overview at IIR.
Compare all 10 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Closed-cell butyl sponge / foam | Low-density compressible weather and acoustic sealing with very low water/vapour transmission. | — | 1 | 200 | 15 Shore A |
A40This page Shore A 40 | Soft gaskets, damping pads and low-clamp-force seals. | — | 8 | 750 | 40 Shore A |
Electrical insulation grade | Cable insulation, splicing tape and mastics where high resistivity plus moisture barrier are required. | — | 9 | 550 | 12 Shore D |
Shore A 50 | General static seals and pharmaceutical stoppers needing needle penetration and reseal. | — | 10 | 680 | 50 Shore A |
IIR-GPDefault IIR general purpose | Standard butyl compound for inner tubes, vibration damping, weather seals and waterproof sheet. | — | 12 | 600 | 60 Shore A |
Chlorobutyl (≈1.2 % Cl), fast/versatile cure, blendable with NR/SBR | Pick when butyl must be co-vulcanized or bonded to diene rubbers, e.g. tire inner liners and tubeless liners. | — | 12 | 600 | 60 Shore A |
Bromobutyl (≈2 % Br), fastest cure, best liner impermeability and… | Choose for tubeless tire inner liners and premium pharmaceutical closures needing fast, low-extractable cure. | — | 13 | 600 | 60 Shore A |
phenolic resin vulcanization, heat/steam resistant (curing bladders) | Use for tire curing bladders, steam hose and diaphragms exposed to superheated steam above 150 °C. | — | 13 | 500 | 60 Shore A |
Shore A 70 | Default hardness for O-rings and pressure-holding seals in brake fluid or steam service. | — | 13 | 450 | 22 Shore D |
Shore A 80 | High-pressure seals, rollers and abrasion/extrusion-resistant parts. | — | 14 | 330 | 30 Shore D |
What is IIR A40?
IIR A40 is IIR heat treated to A40 — soft gaskets, damping pads and low-clamp-force seals. IIR A40 has a tensile strength of 8 MPa (1.16 ksi), weaker than 81% of polymer grades. Elongation at break is 750% and the elastic modulus is 0 GPa (2.61×10⁻⁴ Msi). IIR A40 has a density of 1.05 g/cm³ (0.0379 lb/in³), lighter than 69% of polymer grades. Its glass-transition temperature is -68°C (-90 °F). IIR-GP is the default condition FabDigit quotes; A40 is available on request or by drawing note.
Advantages
- Ductile — tolerates forming and impact — 750%, better than 99% of polymer grades
- Forms and bends easily — 90/100, better than 91% of polymer grades
- Good UV / weathering resistance — 80/100, better than 86% of polymer grades
Limitations
- Difficult to machine — 20/100, worse than 97% of polymer grades
- High mold shrinkage — 3%, worse than 97% of polymer grades
- Low stiffness — 0 GPa (2.61×10⁻⁴ Msi), worse than 96% of polymer grades
- Difficult to weld — 5/100, worse than 89% of polymer grades
- Poor heat conductor — 0.11 W/m·K (0.0636 BTU/hr·ft·°F), worse than 83% of polymer grades
IIR A40 properties
Typical room-temperature values for IIR A40; 16 are specific to this condition. Other listed values are IIR reference data and may not represent this condition. Bars are the position among polymer grades.
Physical3
IIR A40 has a density of 1.05 g/cm³ (0.0379 lb/in³), lighter than 69% of polymer grades. Its glass-transition temperature is -68°C (-90 °F).
Mechanical7
IIR A40 has a tensile strength of 8 MPa (1.16 ksi), weaker than 81% of polymer grades. Elongation at break is 750% and the elastic modulus is 0 GPa (2.61×10⁻⁴ Msi).
Thermal8
IIR A40 is rated for continuous service to 125°C (257 °F). It conducts heat at 0.11 W/m·K (0.0636 BTU/hr·ft·°F), worse than 83% of polymer grades. Thermal expansion is 180 µm/m·K (100 µin/in·°F).
Electrical5
IIR A40 is an electrical insulator with a dielectric strength of 25 kV/mm (635 V/mil) and a resistivity of 1×10¹³ Ω·m.
Chemical & Environmental3
Corrosion resistance is very good (74/100), worse than 68% of polymer grades. UV resistance is very good.
Sustainability4
Producing a kilogram of IIR A40 takes about 105 MJ of energy and emits 4 kg of CO₂ — more than 54% of polymer grades. Typical recycled content is 5%.
Manufacturability6
IIR A40's machinability is poor (20/100, worse than 97% of polymer grades); weldability not recommended (5/100); formability excellent (90/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with IIR A40
Is IIR easy to machine?
Cured butyl is not machined conventionally — use die cutting, water-jet or cryogenic trimming; grinding smears and heats the part.
Can IIR be welded?
Not weldable as a thermoset; join by uncured-to-uncured co-vulcanization, butyl splicing tape/mastic, or cyanoacrylate/chlorinated-surface adhesives after abrasion.
Can IIR be formed, bent or molded?
Mix on mill/Banbury below scorch, then compression, transfer or injection mould at 160–190 °C; halobutyl cures much faster and bonds better to NR/SBR carcasses.
What surface finishes work on IIR?
Deflash by cryogenic tumbling; surfaces can be talc- or lacquer-coated, chlorinated or plasma-treated for lower friction and for bonding/printing.
IIR 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 |
|---|---|---|
| isopreneunsaturation for sulfur cure; often quoted as 0.6–2.2 mol % | 0.5 – 3 | 1.7 |
| chlorineCIIR (chlorobutyl) variant only | 1.1 – 1.3 | 1.2 |
| bromineBIIR (bromobutyl) variant only | 1.8 – 2.1 | 2 |
| carbon blacktypical compound loading 40–60 phr (≈25–35 wt %) | ≈ 30 | 30 |
| processing oil / plasticizerparaffinic oil in the compound | ≈ 8 | 8 |
| zinc oxide / stearic acid / sulfur / acccure system | ≈ 4 | 4 |
| isobutylenepolymer backbone (2-methylpropene) | ≥ 97 (balance) | — |
IIR A40 — frequently asked
What is IIR A40 used for?
IIR A40 is typically used for tire inner liners, pharma vial stoppers, vibration dampers and roofing. In short: lowest gas permeability elastomer; high damping, steam resistant; standard pharma closure rubber.
What is the tensile strength of IIR A40?
IIR A40 has a typical tensile strength of 8 MPa (1.16 ksi) — weaker than 81% of polymer grades. Strength varies by condition: see the 10 listed tempers.
Is IIR A40 easy to machine?
Not especially — machinability is rated poor (20/100, worse than 97% of polymer grades). Cured butyl is not machined conventionally — use die cutting, water-jet or cryogenic trimming; grinding smears and heats the part.
Can IIR A40 be welded?
Not readily — weldability is rated not recommended (5/100). Not weldable as a thermoset; join by uncured-to-uncured co-vulcanization, butyl splicing tape/mastic, or cyanoacrylate/chlorinated-surface adhesives after abrasion.
What surface finishes work on IIR A40?
Deflash by cryogenic tumbling; surfaces can be talc- or lacquer-coated, chlorinated or plasma-treated for lower friction and for bonding/printing.
Can IIR A40 be formed, bent or molded?
Mix on mill/Banbury below scorch, then compression, transfer or injection mould at 160–190 °C; halobutyl cures much faster and bonds better to NR/SBR carcasses.
What is the maximum service temperature of IIR A40?
IIR A40 is rated for continuous use to about 125°C (257 °F), and briefly to 165°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- Butyl and Halobutyl Rubber Product Data (Exxon Butyl / Bromobutyl) — ExxonMobil Chemical (2021)
- Engineered Materials Handbook Vol. 2 — Engineering Plastics/Elastomers — ASM International (1988)
- ASTM D2000 — Classification System for Rubber Products in Automotive Applications — ASTM (2020)
- GB/T 8657 (IIR) — SAC (2018)
- ISO 8871 — Elastomeric parts for parenterals — ISO (2020)
- Rubber Technology Handbook (Hofmann) / Vanderbilt Rubber Handbook — Hanser / R.T. Vanderbilt (2010)
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.