BIIR
BIIR is brominated butyl rubber, a halogenated isobutylene-isoprene elastomer with faster cure and better co-vulcanization with diene rubbers than chlorobutyl, while retaining butyl's low air permeability.
Reference datasheet — BIIR 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 CB-A60 condition
BIIR grades and fills
BIIR is supplied in 8 conditions, soft to hard. CB-A60 is the default FabDigit quotes; the values on this page are for it.
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 | |
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 |
Supply forms, finishes and certifications
Ways BIIR 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 grade | Certification |
PHARMA | Pharmaceutical closure grade | Certification |
What is BIIR?
BIIR is brominated butyl rubber, a halogenated isobutylene-isoprene elastomer with faster cure and better co-vulcanization with diene rubbers than chlorobutyl, while retaining butyl's low air permeability. Default compound values are 11 MPa tensile strength, 500% elongation, 1.13 g/cm3 density and about 0.004 GPa modulus, with service to 130 °C; forms include innerliner calendered sheet, molded closures, bladders and sealant stocks. Cure systems are ZnO-based and scorch-sensitive, and the stock must be kept clear of sulfur-rich compounds. CIIR is the choice where a slower, more forgiving cure suits the process. BIIR has a density of 1.13 g/cm³ (0.0408 lb/in³), lighter than 62% of polymer grades. Its glass-transition temperature is -60°C (-76 °F). BIIR has a tensile strength of 11 MPa (1.6 ksi), weaker than 78% of polymer grades. Elongation at break is 500% and the elastic modulus is 0 GPa (5.8×10⁻⁴ Msi).
What is BIIR used for?
- Tire innerliners
- Pharmaceutical closures
- Curing bladders
- Sealants
Advantages
- Ductile — tolerates forming and impact — 500%, better than 90% of polymer grades
- Good UV / weathering resistance — 85/100, better than 88% of polymer grades
- Forms and bends easily — 88/100, better than 85% of polymer grades
Limitations
- Low stiffness — 0 GPa (5.8×10⁻⁴ Msi), worse than 91% of polymer grades
- Difficult to machine — 30/100, worse than 87% of polymer grades
- High mold shrinkage — 2.2%, worse than 87% of polymer grades
BIIR properties
Typical room-temperature values for BIIR-CB-A60; bars are the position among polymer grades.
Physical4
BIIR has a density of 1.13 g/cm³ (0.0408 lb/in³), lighter than 62% of polymer grades. Its glass-transition temperature is -60°C (-76 °F).
Mechanical11
BIIR has a tensile strength of 11 MPa (1.6 ksi), weaker than 78% of polymer grades. Elongation at break is 500% and the elastic modulus is 0 GPa (5.8×10⁻⁴ Msi).
Thermal8
BIIR is rated for continuous service to 130°C (266 °F). It conducts heat at 0.22 W/m·K (0.127 BTU/hr·ft·°F), better than 60% of polymer grades. Thermal expansion is 180 µm/m·K (100 µin/in·°F).
Electrical5
BIIR is an electrical insulator with a dielectric strength of 25 kV/mm (635 V/mil) and a resistivity of 1×10¹⁰ 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 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's machinability is poor (30/100, worse than 87% of polymer grades); weldability poor (25/100); formability excellent (88/100).
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. BIIR is highlighted; hover a dot for its name, or open the interactive family chart.
Working with BIIR
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.
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) |
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.
How much does BIIR cost?
BIIR is a standard-cost polymer ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
BIIR — frequently asked
What is BIIR used for?
BIIR is typically used for tire innerliners, pharmaceutical closures, curing bladders and sealants. In short: fastest-curing halobutyl; best butyl air retention; pharma closure grade.
What is the tensile strength of BIIR?
BIIR has a typical tensile strength of 11 MPa (1.6 ksi) — weaker than 78% of polymer grades. Strength varies by condition: see the 8 listed tempers.
Is BIIR easy to machine?
Not especially — machinability is rated poor (30/100, worse than 87% of polymer grades). Only die cutting, waterjet or cryogenic deflashing are practical; vulcanized BIIR is gummy and heat-sensitive for conventional machining.
Can BIIR be welded?
Not readily — weldability is rated poor (25/100). Not weldable — parts are joined by uncured splicing then co-vulcanization, or by adhesive bonding after chlorinated/plasma surface activation.
What surface finishes work on BIIR?
Surfaces are naturally low-friction and non-paintable; use chlorination, halogenation or plasma treatment before painting/bonding, and post-cure or wash for pharma/food closures.
Can BIIR be formed, bent or molded?
Mix cool (drop <115 °C) to avoid scorch, then calender/extrude and cure 8–20 min at 160–180 °C; avoid contamination with sulfur-rich stocks and use ZnO-based halobutyl cure systems.
What is the maximum service temperature of BIIR?
BIIR is rated for continuous use to about 130°C (266 °F), and briefly to 170°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does BIIR cost?
BIIR is a standard-cost polymer ($$), 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
- 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; 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.