BIIR CB-A40
Hardness band
CB-A40 = shore A 40
Pick for vibration isolators, soft gaskets and acoustic damping where maximum hysteresis and conformability are wanted.
Values for the CB-A40 condition
Other BIIR grades and fills
BIIR is listed in 8 conditions; see the grade overview at BIIR.
Compare all 8 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Mineral (clay/talc/CaCO3) filled, non-black compound | Use where colour, electrical insulation or non-marking contact surfaces are needed instead of carbon black reinforcement. | — | 7 | 450 | 15 Shore D |
CB-A40This page Shore A 40 | Pick for vibration isolators, soft gaskets and acoustic damping where maximum hysteresis and conformability are wanted. | — | 8 | 700 | 8 Shore D |
Shore A 50 | Balance of sealing conformability and strength for low-pressure gaskets and bladders. | — | 9 | 600 | 11 Shore D |
Tire innerliner compound (BIIR/NR blend, high air retention) | Calendered sheet compound optimized for minimum air permeability and co-vulcanization/adhesion to carcass skim stock. | — | 10 | 650 | 13 Shore D |
CB-A60Default Carbon-black filled, Shore A 60 | Default general-purpose BIIR compound (N550/N660 black, ZnO/sulfur cure) for seals, diaphragms and damping parts. | — | 11 | 500 | 15 Shore D |
Resin-cured (phenolic resin) heat-resistant compound | Phenolic-resin cure system for tire curing bladders and steam service — best heat ageing and lowest compression set. | — | 11 | 500 | 14 Shore D |
Shore A 70 | Choose for higher-pressure seals, hose covers and parts needing extrusion resistance. | — | 12 | 420 | 22 Shore D |
Shore A 80 | For rigid mounts, backup rings and parts requiring stiffness and low deflection under load. | — | 13 | 300 | 30 Shore D |
What is BIIR CB-A40?
BIIR CB-A40 is BIIR heat treated to CB-A40 — pick for vibration isolators, soft gaskets and acoustic damping where maximum hysteresis and conformability are wanted. BIIR CB-A40 has a tensile strength of 8 MPa (1.09 ksi), weaker than 82% of polymer grades. Elongation at break is 700% and the elastic modulus is 0 GPa (3.19×10⁻⁴ Msi). BIIR CB-A40 has a density of 1.05 g/cm³ (0.0379 lb/in³), lighter than 69% of polymer grades. Its glass-transition temperature is -60°C (-76 °F). CB-A60 is the default condition FabDigit quotes; CB-A40 is available on request or by drawing note.
Advantages
- Forms and bends easily — 94/100, better than 98% of polymer grades
- Ductile — tolerates forming and impact — 700%, better than 96% of polymer grades
- Good UV / weathering resistance — 85/100, better than 88% of polymer grades
Limitations
- Difficult to machine — 20/100, worse than 97% of polymer grades
- High mold shrinkage — 2.6%, worse than 96% of polymer grades
- Low stiffness — 0 GPa (3.19×10⁻⁴ Msi), worse than 94% of polymer grades
BIIR CB-A40 properties
Typical room-temperature values for BIIR CB-A40; 18 are specific to this condition. Other listed values are BIIR reference data and may not represent this condition. Bars are the position among polymer grades.
Physical4
BIIR CB-A40 has a density of 1.05 g/cm³ (0.0379 lb/in³), lighter than 69% of polymer grades. Its glass-transition temperature is -60°C (-76 °F).
Mechanical11
BIIR CB-A40 has a tensile strength of 8 MPa (1.09 ksi), weaker than 82% of polymer grades. Elongation at break is 700% and the elastic modulus is 0 GPa (3.19×10⁻⁴ Msi).
Thermal8
BIIR CB-A40 is rated for continuous service to 125°C (257 °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 180 µm/m·K (100 µin/in·°F).
Electrical5
BIIR CB-A40 is an electrical insulator with a dielectric strength of 25 kV/mm (635 V/mil) and a resistivity of 1×10¹² Ω·m.
Chemical & Environmental3
Corrosion resistance is excellent (85/100), better than 65% of polymer grades. UV resistance is excellent.
Sustainability4
Producing a kilogram of BIIR CB-A40 takes about 105 MJ of energy and emits 3.6 kg of CO₂ — more than 54% of polymer grades. Typical recycled content is 5%.
Manufacturability5
BIIR CB-A40's machinability is poor (20/100, worse than 97% of polymer grades); weldability poor (28/100); formability excellent (94/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with BIIR CB-A40
Is BIIR easy to machine?
Only die cutting, waterjet or cryogenic deflashing are practical; vulcanized BIIR is gummy and heat-sensitive for conventional machining.
Can BIIR be welded?
Not weldable — parts are joined by uncured splicing then co-vulcanization, or by adhesive bonding after chlorinated/plasma surface activation.
Can BIIR be formed, bent or molded?
Mix cool (drop <115 °C) to avoid scorch, then calender/extrude and cure 8–20 min at 160–180 °C; avoid contamination with sulfur-rich stocks and use ZnO-based halobutyl cure systems.
What surface finishes work on BIIR?
Surfaces are naturally low-friction and non-paintable; use chlorination, halogenation or plasma treatment before painting/bonding, and post-cure or wash for pharma/food closures.
BIIR 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 |
|---|---|---|
| isoprene (repeat unit)unsaturation site for halogenation/cure | 1.5 – 2.5 | 2 |
| Brbound bromine on polymer, e.g. Bromobutyl 2222 ≈ 2.0 % | 1.6 – 2.3 | 2 |
| carbon black (N550/N660)phr in default vulcanizate, not wt% of polymer | 30 – 60 | 50 |
| ZnO / stearic acid / cure packagephr; ZnO-activated halobutyl cure | 1 – 5 | 3 |
| process oil / tackifierphr, paraffinic | 5 – 20 | 10 |
| isobutylene (repeat unit)polymer backbone | ≥ 96 (balance) | — |
BIIR CB-A40 — frequently asked
What is BIIR CB-A40 used for?
BIIR CB-A40 is typically used for tire innerliners, pharmaceutical closures, curing bladders and sealants. In short: fastest-curing halobutyl; best butyl air retention; pharma closure grade.
What is the tensile strength of BIIR CB-A40?
BIIR CB-A40 has a typical tensile strength of 8 MPa (1.09 ksi) — weaker than 82% of polymer grades. Strength varies by condition: see the 8 listed tempers.
Is BIIR CB-A40 easy to machine?
Not especially — machinability is rated poor (20/100, worse than 97% of polymer grades). Only die cutting, waterjet or cryogenic deflashing are practical; vulcanized BIIR is gummy and heat-sensitive for conventional machining.
Can BIIR CB-A40 be welded?
Not readily — weldability is rated poor (28/100). Not weldable — parts are joined by uncured splicing then co-vulcanization, or by adhesive bonding after chlorinated/plasma surface activation.
What surface finishes work on BIIR CB-A40?
Surfaces are naturally low-friction and non-paintable; use chlorination, halogenation or plasma treatment before painting/bonding, and post-cure or wash for pharma/food closures.
Can BIIR CB-A40 be formed, bent or molded?
Mix cool (drop <115 °C) to avoid scorch, then calender/extrude and cure 8–20 min at 160–180 °C; avoid contamination with sulfur-rich stocks and use ZnO-based halobutyl cure systems.
What is the maximum service temperature of BIIR CB-A40?
BIIR CB-A40 is rated for continuous use to about 125°C (257 °F), and briefly to 170°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- ExxonMobil Bromobutyl 2222/2255 product and compounding bulletins — ExxonMobil Chemical (2021)
- X_Butyl BB 2030/BB X2 halobutyl rubber data sheets — ARLANXEO / Lanxess (2022)
- Engineered Materials Handbook Vol. 2 — Engineering Plastics & Elastomers — ASM International (1988)
- ASTM D2000 — Classification System for Rubber Products in Automotive Applications — ASTM (2020)
- ISO 8871 / USP <381> Elastomeric parts for parenterals — ISO / USP (2020)
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.