CIIR A40
Hardness band
A40 = soft grade
Highly plasticized soft compound for low-closure-force gaskets, bladders and vibration pads.
Values for the A40 condition
Other CIIR grades and fills
CIIR is listed in 11 conditions; see the grade overview at CIIR.
Compare all 11 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Closed-cell sponge / expanded compound | Chemically blown closed-cell butyl sponge for acoustic damping, weatherstrip and low-force gasketing. | — | 1 | 250 | 20 Shore A |
A40This page Soft grade | Highly plasticized soft compound for low-closure-force gaskets, bladders and vibration pads. | — | 7 | 700 | 8 Shore D |
Flame-retardant compound | Choose where UL 94 V-0 or low-smoke performance is required in sealing/insulating rubber parts. | — | 7 | 350 | 22 Shore D |
Mineral/clay-filled light-coloured compound | Non-black insulating or colourable compound for electrical parts, white goods and pharma-adjacent sealing. | — | 8 | 450 | 18 Shore D |
Low-temperature / high-plasticizer compound | Ester-plasticized compound for seals that must stay flexible below −50 °C. | — | 8 | 600 | 50 Shore A |
Tire innerliner compound (high-halobutyl, low permeability) | Pick for tubeless tire innerliners, air-retention bladders and inflatable seals where gas permeability governs. | — | 9 | 650 | 12 Shore D |
50 Shore A compound | Soft-medium compound for diaphragms, pharmaceutical stoppers and flexible boots. | — | 10 | 600 | 11 Shore D |
GP-A60Default General-purpose black-filled compound, 60 Shore A | Default ZnO/stearic-acid cured carbon-black compound for seals, diaphragms, sheet and general molded goods. | — | 12 | 500 | 15 Shore D |
80 Shore A compound | High-filler, stiff compound for extrusion-resistant seals, bumpers and rigid mounts. | — | 12 | 280 | 28 Shore D |
70 Shore A compound | Standard sealing hardness for O-rings, valve seats and hose covers under moderate pressure. | — | 13 | 400 | 20 Shore D |
CIIR/NR (or CIIR/SBR-EPDM) co-cure blend | Used where halobutyl must be adhered/co-vulcanized to diene rubber — tire sidewalls, innerliner tie-gum, laminated seals. | — | 15 | 520 | 14 Shore D |
What is CIIR A40?
CIIR A40 is CIIR heat treated to A40 — highly plasticized soft compound for low-closure-force gaskets, bladders and vibration pads. CIIR A40 has a tensile strength of 7 MPa (1.02 ksi), weaker than 82% of polymer grades. Elongation at break is 700% and the elastic modulus is 0 GPa (2.9×10⁻⁴ Msi). CIIR A40 has a density of 1.1 g/cm³ (0.0397 lb/in³), lighter than 66% of polymer grades. Its glass-transition temperature is -60°C (-76 °F). GP-A60 is the default condition FabDigit quotes; A40 is available on request or by drawing note.
Advantages
- Ductile — tolerates forming and impact — 700%, better than 96% of polymer grades
- Forms and bends easily — 90/100, better than 91% of polymer grades
- Good UV / weathering resistance — 88/100, better than 90% of polymer grades
- High service temperature — 135°C (275 °F), better than 75% of polymer grades
Limitations
- Low stiffness — 0 GPa (2.9×10⁻⁴ Msi), worse than 95% 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
- Absorbs moisture — dry before molding — 0.6%, worse than 75% of polymer grades
CIIR A40 properties
Typical room-temperature values for CIIR A40; 17 are specific to this condition. Other listed values are CIIR reference data and may not represent this condition. Bars are the position among polymer grades.
Physical3
CIIR A40 has a density of 1.1 g/cm³ (0.0397 lb/in³), lighter than 66% of polymer grades. Its glass-transition temperature is -60°C (-76 °F).
Mechanical11
CIIR A40 has a tensile strength of 7 MPa (1.02 ksi), weaker than 82% of polymer grades. Elongation at break is 700% and the elastic modulus is 0 GPa (2.9×10⁻⁴ Msi).
Thermal8
CIIR A40 is rated for continuous service to 135°C (275 °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 170 µm/m·K (94.4 µin/in·°F).
Electrical5
CIIR A40 is an electrical insulator with a dielectric strength of 24 kV/mm (609.6 V/mil) and a resistivity of 1×10¹² Ω·m.
Chemical & Environmental3
Corrosion resistance is very good (80/100), worse than 52% of polymer grades. UV resistance is excellent.
Sustainability4
Producing a kilogram of CIIR A40 takes about 115 MJ of energy and emits 3.6 kg of CO₂ — more than 70% of polymer grades. Typical recycled content is 5%.
Manufacturability5
CIIR A40's machinability is poor (25/100, worse than 93% of polymer grades); formability excellent (90/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with CIIR A40
Is CIIR easy to machine?
Cured stock is die-cut, waterjet or cryogenically deflashed; conventional machining smears — use sharp, water-lubricated blades and freeze trimming.
Can CIIR be welded?
Not weldable; parts are joined by co-vulcanized splicing, halobutyl-compatible cement, or over-molding onto a primed substrate.
Can CIIR be formed, bent or molded?
Mix below ~120 °C to avoid scorch (halobutyl is scorch-sensitive with ZnO); compression, transfer or injection mold and press-cure 5–15 min at 165–190 °C, or continuous-cure extrude in salt bath/microwave.
What surface finishes work on CIIR?
Bondability is poor without treatment — chlorination, plasma or a chlorobutyl-based tie gum is needed for adhesion; surfaces can be talc/PTFE-coated or silicone-treated for low tack on stoppers and liners.
CIIR 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 |
|---|---|---|
| isopreneprovides unsaturation/cure sites | 1 – 2.5 | 1.8 |
| Clallylic chlorine cure sites (halogenation level, wt%) | 1 – 1.4 | 1.2 |
| stabilizer (Ca-stearate/epoxidized soybeas supplied in raw bale | 0.5 – 2 | 1.2 |
| carbon black (N550/N660) in default compphr, not wt% of polymer | 40 – 70 | 55 |
| ZnO / stearic acid cure systemphr; MgO added as acid acceptor/scorch control | ≈ 5 | 5 |
| isobutylenepolymer backbone repeat unit | ≥ 96.5 (balance) | — |
CIIR A40 — frequently asked
What is CIIR A40 used for?
CIIR A40 is typically used for tire innerliners, pharmaceutical stoppers, adhesive tapes and chemical hose linings. In short: fast-curing halobutyl; low gas permeability; blends with diene rubbers.
What is the tensile strength of CIIR A40?
CIIR A40 has a typical tensile strength of 7 MPa (1.02 ksi) — weaker than 82% of polymer grades. Strength varies by condition: see the 11 listed tempers.
Is CIIR A40 easy to machine?
Not especially — machinability is rated poor (25/100, worse than 93% of polymer grades). Cured stock is die-cut, waterjet or cryogenically deflashed; conventional machining smears — use sharp, water-lubricated blades and freeze trimming.
Can CIIR A40 be welded?
Not weldable; parts are joined by co-vulcanized splicing, halobutyl-compatible cement, or over-molding onto a primed substrate.
What surface finishes work on CIIR A40?
Bondability is poor without treatment — chlorination, plasma or a chlorobutyl-based tie gum is needed for adhesion; surfaces can be talc/PTFE-coated or silicone-treated for low tack on stoppers and liners.
Can CIIR A40 be formed, bent or molded?
Mix below ~120 °C to avoid scorch (halobutyl is scorch-sensitive with ZnO); compression, transfer or injection mold and press-cure 5–15 min at 165–190 °C, or continuous-cure extrude in salt bath/microwave.
What is the maximum service temperature of CIIR A40?
CIIR A40 is rated for continuous use to about 135°C (275 °F), and briefly to 175°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- Exxon™ Chlorobutyl rubber grades 1066/1068 product and compounding data — ExxonMobil Chemical (2021)
- X_Butyl™ CB chlorobutyl rubber technical information — ARLANXEO (2022)
- ASM Engineered Materials Handbook Vol. 2: Engineering Plastics / Elastomer property tables — ASM International (1988)
- ASTM D2000 — Classification System for Rubber Products in Automotive Applications — ASTM International (2021)
- ASTM D412 / D624 / D395 / D2240 — tensile, tear, compression set, durometer test methods — ASTM International (2021)
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.