BR
BR is high-cis polybutadiene produced on Ni, Nd, Li or Co catalyst systems, normally used as a blend component with NR or SBR rather than on its own.
Reference datasheet — BR 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 HI-CIS-NI condition
BR grades and fills
BR is supplied in 9 conditions, soft to hard. HI-CIS-NI is the default FabDigit quotes; the values on this page are for it.
Compare all 9 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Shore A 50 compound | Soft, highly resilient BR compound for damping pads, low-temperature seals and soling with maximum rebound. | 10 | 550 | 10 Shore D | |
Lithium-catalysed low-cis | Choose for HIPS/ABS impact modification and easier mill processing (less cold flow) rather than for maximum abrasion. | 12 | 500 | 10 Shore D | |
Oil-extended BR | Pick when high-molecular-weight BR must be processed at low mixing energy or when soft, high-filler tread compounds are needed. | 12 | 520 | 9 Shore D | |
HI-CIS-NIDefault High-cis BR, Ni/Co-catalysed (BR9000 / BR1502 type) | Default workhorse high-cis BR (≈96 % cis) for tire treads/sidewalls, belt covers and shoe soles blended with NR/SBR. | 15 | 450 | 12 Shore D | |
Shore A 60 compound | Standard reinforced BR vulcanizate — the reference compound for datasheet mechanical values. | 15 | 450 | 13 Shore D | |
High-vinyl BR | Use where wet grip and damping matter more than low hysteresis — high-performance tread blends with S-SBR. | 16 | 420 | 13 Shore D | |
neodymium-catalysed very high cis (≥96–99 %) | Pick for the best abrasion resistance and lowest rolling-resistance hysteresis in premium truck and passenger tire treads. | 17 | 480 | 12 Shore D | |
Shore A 70 compound | Harder, more abrasion-resistant BR compound for belt covers, tread bases and industrial wheels. | 18 | 350 | 20 Shore D | |
High-trans polybutadiene | Specialty semi-crystalline BR for golf-ball cores, high green-strength tire components and NR-substitute blends. | 20 | 400 | 22 Shore D |
What is BR?
BR is high-cis polybutadiene produced on Ni, Nd, Li or Co catalyst systems, normally used as a blend component with NR or SBR rather than on its own. It adds resilience, low hysteresis and abrasion resistance, with a glass transition of -105 °C that keeps blends flexible in the cold; cured compounds reach 15 MPa tensile strength and 450 % elongation with service to 90 °C. Raw BR cold-flows and has poor green strength, so mill handling and building tack are difficult, and oil, fuel and ozone resistance are poor; SBR is the usual alternative when processing matters more than rebound. BR has a density of 0.93 g/cm³ (0.0336 lb/in³), lighter than 78% of polymer grades. Its glass-transition temperature is -105°C (-157 °F). BR has a tensile strength of 15 MPa (2.18 ksi), weaker than 74% of polymer grades. Elongation at break is 450% and the elastic modulus is 0 GPa (5.8×10⁻⁴ Msi).
What is BR used for?
- tire sidewalls
- golf ball cores
- conveyor belts
- rubber blends
Advantages
- Ductile — tolerates forming and impact — 450%, better than 88% of polymer grades
- Forms and bends easily — 85/100, better than 81% of polymer grades
- Low embodied carbon — 3.2 kg CO₂/kg, better than 81% of polymer grades
- Lightweight — 0.93 g/cm³ (0.0336 lb/in³), better than 78% of polymer grades
Limitations
- Needs corrosion protection — 45/100, worse than 98% of polymer grades
- Difficult to machine — 25/100, worse than 93% of polymer grades
- Low stiffness — 0 GPa (5.8×10⁻⁴ Msi), worse than 91% of polymer grades
- Degrades in UV without stabilisers — 20/100, worse than 88% of polymer grades
- High mold shrinkage — 2%, worse than 81% of polymer grades
BR properties
Typical room-temperature values for BR-HI-CIS-NI; bars are the position among polymer grades.
Physical4
BR has a density of 0.93 g/cm³ (0.0336 lb/in³), lighter than 78% of polymer grades. Its glass-transition temperature is -105°C (-157 °F).
Mechanical10
BR has a tensile strength of 15 MPa (2.18 ksi), weaker than 74% of polymer grades. Elongation at break is 450% and the elastic modulus is 0 GPa (5.8×10⁻⁴ Msi).
Thermal8
BR is rated for continuous service to 90°C (194 °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 220 µm/m·K (122.2 µin/in·°F).
Electrical5
BR is an electrical insulator with a dielectric strength of 22 kV/mm (558.8 V/mil) and a resistivity of 1×10¹³ Ω·m.
Chemical & Environmental3
Corrosion resistance is fair (45/100), worse than 98% of polymer grades. UV resistance is poor.
Sustainability4
Producing a kilogram of BR takes about 96 MJ of energy and emits 3.2 kg of CO₂ — less than 67% of polymer grades. Typical recycled content is 0%.
Manufacturability6
BR's machinability is poor (25/100, worse than 93% of polymer grades); weldability poor (20/100); formability excellent (85/100).
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. BR is highlighted; hover a dot for its name, or open the interactive family chart.
Working with BR
Is BR easy to machine?
Cured BR is best cut by water-jet, die-cutting or cryogenic grinding; conventional machining smears and heats the part.
Can BR be welded?
Not weldable — join by vulcanised splices, unvulcanised gum-strip build-up or cyanoacrylate/chloroprene adhesives after abrasion and primer.
Can BR be formed, bent or molded?
Raw BR cold-flows and bands poorly on the mill, so it is normally masterbatched with NR/SBR and 30–60 phr black; compression, transfer or injection cure at 145–180 °C with sulfur/CBS systems.
BR 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 |
|---|---|---|
| cis-1,4 microstructureNi/Co/Nd high-cis grades; Li grades ≈30–40 % cis | 92 – 99 | 96 |
| trans-1,4 microstructurehigh-cis grades; TBR grades >70 % | 1 – 5 | 2 |
| 1,2-vinyl microstructureHVBR grades 50–90 % | 1 – 4 | 2 |
| volatile matterGB/T 8657 bale specification | ≤ 0.75 | 0.4 |
| ashGB/T 8657 | ≤ 0.3 | 0.15 |
| antioxidant (non-staining)added to bale rubber | 0.2 – 1 | 0.5 |
| carbon black (in typical vulcanizate)phr, not wt % of polymer; N330/N550 typical | 30 – 60 | 50 |
| 1,3-butadiene (repeat unit)homopolymer; no comonomer | balance |
What surface finishes work on BR?
Deflash by cryogenic tumbling; surfaces can be chlorinated or plasma/primer treated for adhesion; add wax, antiozonant and carbon black for outdoor colour and ozone protection.
How much does BR cost?
BR is a standard-cost polymer ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
BR — frequently asked
What is BR used for?
BR is typically used for tire sidewalls, golf ball cores, conveyor belts and rubber blends. In short: highest-resilience diene rubber; lowest Tg at -105 °C; blend component, poor green strength.
What is the tensile strength of BR?
BR has a typical tensile strength of 15 MPa (2.18 ksi) — weaker than 74% of polymer grades. Strength varies by condition: see the 9 listed tempers.
Is BR easy to machine?
Not especially — machinability is rated poor (25/100, worse than 93% of polymer grades). Cured BR is best cut by water-jet, die-cutting or cryogenic grinding; conventional machining smears and heats the part.
Can BR be welded?
Not readily — weldability is rated poor (20/100). Not weldable — join by vulcanised splices, unvulcanised gum-strip build-up or cyanoacrylate/chloroprene adhesives after abrasion and primer.
What surface finishes work on BR?
Deflash by cryogenic tumbling; surfaces can be chlorinated or plasma/primer treated for adhesion; add wax, antiozonant and carbon black for outdoor colour and ozone protection.
Can BR be formed, bent or molded?
Raw BR cold-flows and bands poorly on the mill, so it is normally masterbatched with NR/SBR and 30–60 phr black; compression, transfer or injection cure at 145–180 °C with sulfur/CBS systems.
What is the maximum service temperature of BR?
BR is rated for continuous use to about 90°C (194 °F), and briefly to 120°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does BR cost?
BR is a standard-cost polymer ($$), 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
- GB/T 8657 (BR) — SAC (2019)
- ASTM D5900 / D3568 — Standard practices for rubber test recipes and BR evaluation — ASTM (2020)
- Engineered Materials Handbook Vol. 2 — Engineering Plastics & Elastomers — ASM International (1988)
- Rubber Technology: Compounding and Testing for Performance — Hanser (2009)
- Buna CB / Nd-BR grade datasheets — ARLANXEO / LANXESS (2023)
- Polymer Handbook (4th ed.) — polybutadiene thermal and optical constants — Wiley (1999)
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.