IIR-GP
Grade · default condition
ASTM CIIR, BIIR
IIR-GP = iIR general purpose
Standard butyl compound for inner tubes, vibration damping, weather seals and waterproof sheet.
Values for the IIR-GP 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 |
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-GPDefaultThis page 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-GP?
IIR-GP is IIR in the IIR-GP grade — standard butyl compound for inner tubes, vibration damping, weather seals and waterproof sheet. IIR-GP has a tensile strength of 12 MPa (1.74 ksi), weaker than 76% of polymer grades. Elongation at break is 600% and the elastic modulus is 0.01 GPa (7.25×10⁻⁴ Msi). IIR-GP has a density of 1.12 g/cm³ (0.0405 lb/in³), lighter than 64% of polymer grades. Its glass-transition temperature is -68°C (-90 °F).
Advantages
- Ductile — tolerates forming and impact — 600%, better than 93% of polymer grades
- Good UV / weathering resistance — 80/100, better than 86% of polymer grades
- Forms and bends easily — 80/100, better than 75% of polymer grades
Limitations
- High mold shrinkage — 2.5%, worse than 93% of polymer grades
- Low stiffness — 0.01 GPa (7.25×10⁻⁴ Msi), worse than 89% of polymer grades
- Difficult to weld — 5/100, worse than 89% of polymer grades
- Difficult to machine — 30/100, worse than 87% of polymer grades
- Poor heat conductor — 0.13 W/m·K (0.0751 BTU/hr·ft·°F), worse than 82% of polymer grades
IIR-GP properties
Typical room-temperature values for IIR-GP; 15 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-GP has a density of 1.12 g/cm³ (0.0405 lb/in³), lighter than 64% of polymer grades. Its glass-transition temperature is -68°C (-90 °F).
Mechanical7
IIR-GP has a tensile strength of 12 MPa (1.74 ksi), weaker than 76% of polymer grades. Elongation at break is 600% and the elastic modulus is 0.01 GPa (7.25×10⁻⁴ Msi).
Thermal8
IIR-GP is rated for continuous service to 125°C (257 °F). It conducts heat at 0.13 W/m·K (0.0751 BTU/hr·ft·°F), worse than 82% of polymer grades. Thermal expansion is 180 µm/m·K (100 µin/in·°F).
Electrical5
IIR-GP is an electrical insulator with a dielectric strength of 25 kV/mm (635 V/mil) and a resistivity of 1×10¹¹ Ω·m.
Chemical & Environmental3
Corrosion resistance is very good (75/100), worse than 66% of polymer grades. UV resistance is very good.
Sustainability4
Producing a kilogram of IIR-GP 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-GP's machinability is poor (30/100, worse than 87% of polymer grades); weldability not recommended (5/100); formability very good (80/100).
Common Calculations4
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with IIR-GP
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-GP — frequently asked
What is IIR-GP used for?
IIR-GP 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-GP?
IIR-GP has a typical tensile strength of 12 MPa (1.74 ksi) — weaker than 76% of polymer grades. Strength varies by condition: see the 10 listed tempers.
Is IIR-GP easy to machine?
Not especially — machinability is rated poor (30/100, worse than 87% 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-GP 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-GP?
Deflash by cryogenic tumbling; surfaces can be talc- or lacquer-coated, chlorinated or plasma-treated for lower friction and for bonding/printing.
Can IIR-GP 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-GP?
IIR-GP 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.