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| HS Code | 918458 |
| Chemical Name | Polybutadiene |
| Chemical Formula | (C4H6)n |
| Cas Number | 9003-17-2 |
| Appearance | Colorless to pale yellow solid rubber |
| Density | 0.90-0.92 g/cm3 |
| Glass Transition Temperature | -110°C to -100°C |
| Mooney Viscosity Ml 1 4 At 100 C | 35-55 |
| Tensile Strength | 12-20 MPa (with reinforcement) |
| Tensile Elongation At Break | 400-600% |
| Abrasion Resistance | Excellent |
| Resilience | Very high, typically above 80% |
| Solubility | Soluble in hydrocarbons and aromatic solvents |
| Thermal Conductivity | 0.22 W/(m·K) |
| Hardness Shore A | 55-75 |
As an accredited Polybutadiene Rubber factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Polybutadiene Rubber is packaged in 25 kg bales, wrapped in polyethylene film, and stacked on wooden pallets for safe transport. |
| Container Loading (20′ FCL) | Polybutadiene rubber bales are loaded into a 20-foot FCL container, secured tightly, protected from moisture and heat. |
| Shipping | Polybutadiene rubber (BR) is typically shipped as solid bales, crumb, or pellets in polyethylene-lined bags, cartons, drums, or FIBC bulk bags. It is non-hazardous and generally unregulated for transport. Keep dry, protect from contamination, and avoid prolonged heat or direct sunlight. Use clean, covered containers for safe handling. |
| Storage | Store polybutadiene rubber in a cool, dry, well-ventilated area away from direct sunlight, heat sources, open flames, and strong oxidizers. Keep bales or blocks in original unopened packaging, elevated off the floor, and protected from moisture and ozone. Avoid excessive stacking or compression to prevent deformation. Follow manufacturer’s shelf-life guidelines and first-in, first-out usage. |
| Shelf Life | Polybutadiene Rubber has a typical shelf life of 1–2 years when stored in a cool, dry, dark place away from ozone and sunlight. |
High-cis neodymium-catalysed polybutadiene with ≥ 96% cis-1,4 content and Mooney viscosity ML 1+4 100 °C = 40–60 MU is introduced into silica-reinforced passenger tyre treads at 20–35 phr in blends with solution SBR. The low glass transition temperature of −105 °C to −95 °C does not act as a direct wet grip failure mechanism; the reduced hysteretic response at 0 °C to 30 °C lowers tan δ in the wet braking frequency range and shifts the performance balance toward abrasion improvement. Silica dispersion is governed less by BR content than by the silane coupling reaction of bis(triethoxysilylpropyl) tetrasulfide at a first-pass dump temperature of 145–155 °C; below 140 °C the silane remains under-reacted, and above 160 °C premature gel formation and scorch risk rise. Production-scale tangential internal mixers with net chamber volumes of 270–350 L and fill factors of 0.70–0.75 are operated at rotor speeds of 40–55 min⁻¹; fill factors below 0.65 intensify shear heating, while fill factors above 0.80 inhibit adequate silanization and dispersion. The discharged compound is milled at 55–65 °C and sheeted before sulfur curative addition at 90–105 °C. Mooney viscosity is measured by ASTM D1646-19, cure behaviour by ISO 6502:2018 at 160 °C, tensile by ISO 37:2017, and abrasion by DIN ISO 4649:2020 Method A; tread acceptance typically requires abrasion loss below 120 mm³ and tensile strength above 18 MPa. Sidewall compounds use higher BR loadings of 40–60 phr with natural rubber because flex fatigue resistance under ASTM D4482-11 is improved, but tear strength under ISO 34-1:2022 declines when high-cis BR exceeds 50 phr in low-sulfur systems.
| Property | Standard | Condition |
|---|---|---|
| Mooney viscosity | ASTM D1646-19 | ML 1+4 100 °C |
| Cure characteristics | ISO 6502:2018 | 160 °C moving-die rheometer |
| Tensile stress-strain | ISO 37:2017 | Type 2 dumbbell |
| DIN abrasion | DIN ISO 4649:2020 | Method A, non-rotating |
| Hardness | ASTM D2240-15 | Shore A |
| Tear strength | ISO 34-1:2022 | Nicked angle |
| Low-temperature brittleness | ISO 812:2017 | Impact failure |
In bulk high-impact polystyrene production, polybutadiene rubber with Mooney viscosity 35–55 MU and solution viscosity 40–170 mPa·s at 5 wt% in styrene is dissolved in styrene at 6–10 wt% before free-radical initiation. Low-cis and medium-cis grades are preferred because thermal crosslinking during prepolymerization controls particle stabilisation; high-cis grades dissolve more slowly and can produce gel specks at equivalent shear conditions. Prepolymerisation is conducted in stirred vessels at 120–145 °C to a conversion of 12–25%, where the phase inversion from rubber-in-styrene to styrene-in-rubber occurs. Continuous finishing reactors then raise conversion to 75–90% at 150–180 °C. Rubber particle diameter is controlled by agitator tip speed and is typically 0.5–4.0 µm; below 0.5 µm impact efficiency under ASTM D256-23 declines, while above 4.0 µm gloss and tensile strength under ASTM D638-22 are impaired. Grafting efficiency is stabilised by thermal initiators and chain transfer agents; insufficient grafting produces free rubber particles that lower heat distortion temperature. Melt flow rate is checked under ASTM D1238-20 at 200 °C/5 kg, and Vicat softening under ASTM D1525-17. Operational boundaries include pre-dissolution temperature above 60 °C to prevent rubber lumping in the feed line; residual styrene devolatilisation below 300 ppm is required for food-contact HIPS under 21 CFR 177.1640, though additive-specific compliance is grade-dependent.
High-cis neodymium-catalysed BR with Mooney viscosity 40–50 MU is milled at 70–85 °C with zinc diacrylate at 20–40 phr, zinc oxide at 5–10 phr, and dicumyl peroxide at 0.5–1.5 phr. Zinc diacrylate dispersion is the primary processing constraint: undispersed particles act as stress concentrators and reduce initial velocity after repeated impact. The mixed stock is compression moulded at 150–165 °C for 12–20 min under 10–15 MPa mould pressure; cure is monitored by moving-die rheometer per ISO 6502:2018 with tc90 of 8–15 min at 160 °C. Core compression is measured under ASTM D575-91 Method A. Coefficient of restitution is not governed by a single ASTM procedure; OEM test methods typically use inbound ball velocity near 38 m/s. Overcure beyond tc90 + 2 min increases surface hardness and lowers resilience; undercure leaves free zinc diacrylate and produces compression loss after repeated impact. The workable process window is approximately ±2 min at 160 °C and ±1 phr peroxide, beyond which core recovery falls outside OEM specification. Antioxidants such as 0.2–0.5 phr of phenolic types are included to limit thermo-oxidative degradation during service, but higher levels interfere with peroxide cure and lower crosslink density.
Cover compounds for mining conveyor belts use polybutadiene to shift the failure mode from cut growth to abrasion. In a typical Banbury or intermeshing tangential mixer, BR is added at 20–40 phr with natural rubber and carbon black N220 or N330; oil addition is held at 5–15 phr to avoid lowering tear strength. Mixing follows ASTM D3182-21; dump temperature is controlled at 150–160 °C for the first pass, with sulfur and accelerator added at 90–105 °C on the second pass. Extruded cover sheets are calendered at 0.8–1.2 mm gauge onto carcass plies and vulcanised in a continuous rotocure at 150–160 °C for 20–30 min or in an autoclave under 0.5–0.7 MPa steam. The cured compound is evaluated for abrasion with DIN ISO 4649:2020 Method A; high-abrasion-resistant covers require loss below 90 mm³. Tear strength under ISO 34-1:2022 should exceed 30 kN/m for belt covers carrying sharp ore. Adhesion to steel cord is tested by ISO 7623:2022; cobalt salt systems in the skim compound are used, but amine-based antioxidants are avoided because they can poison the cobalt-rubber adhesive bond.
Solid footwear soling compounds blend high-cis BR with natural rubber at 30–50 phr; mixing follows ASTM D3182-21, injection moulding is conducted at 150–170 °C, and the cured compound is specified at Shore A 60–70 under ASTM D2240-15 and DIN abrasion below 120 mm³ under DIN ISO 4649:2020. Beyond 50 phr BR, trouser tear strength under ISO 34-1:2022 usually falls below 15 kN/m, limiting use in safety footwear.
Polybutadiene is not a primary bitumen modifier; SBS and SBR dominate because the high unsaturation of BR accelerates oxidative embrittlement during hot-mix storage at 160–180 °C. Technical literature examining BR at 2–5 wt% of bitumen reports low-temperature elasticity but poor high-temperature storage stability; published data for this specific configuration is limited. No ASTM or CEN specification covers BR-modified bitumen directly. If BR is used, pre-blending with ground tyre rubber or sulfur crosslinking at 0.1–0.3 wt% is required to reduce phase separation. The material is not recommended for polymer-modified bitumen meeting EN 14023:2010 or ASTM D5976 unless supported by project-specific testing.
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Polybutadiene rubber (BR) is a solution-polymerized homopolymer of 1,3-butadiene manufactured in bale and crumb form. The principal grade families are defined by catalyst architecture rather than a single model designation: high-cis neodymium-catalyzed BR with cis-1,4 content of 96–99 % and vinyl content below 1.5 %; medium-cis cobalt- or nickel-catalyzed BR with cis-1,4 content of 50–70 %; low-cis lithium-catalyzed BR with cis-1,4 content of 36–42 % and vinyl content of 10–15 %; and high-vinyl lithium-catalyzed BR with vinyl content of 50–80 %. Commercial specification sheets identify a grade by nominal Mooney viscosity ML 1+4 at 100 °C, usually 35–60 MU, and, where applicable, oil-extension level of 25, 37.5, or 50 phr treated distillate aromatic extract or naphthenic oil. The material is used in tire treads, sidewalls, retread compounds, conveyor belt covers, footwear soles, and as a graft substrate in high-impact polystyrene and acrylonitrile-butadiene-styrene resins. Differences from other elastomers are structural and application-specific: BR lacks the non-rubber constituents of natural rubber, has lower hysteresis than SBR but poorer wet traction, is sulfur-vulcanizable in conventional accelerated systems unlike EPDM, and has negligible oil resistance compared with nitrile or chloroprene rubbers because of its non-polar hydrocarbon main chain. Testing and compounding are anchored by ISO 2476 and ASTM D3189, with Mooney viscosity determined under ASTM D1646 or ISO 289-1, microstructure under ISO 12965, volatile matter under ISO 248-1, and ash under ISO 247.
High-cis neodymium grades exhibit a glass transition temperature of -107 °C to -103 °C when measured by differential scanning calorimetry under ASTM E1356. The low vinyl content, below 1.5 %, reduces the number of pendant olefinic groups that increase segmental friction; the resulting hysteresis is low in dynamic mechanical analysis at 60 °C, which correlates with lower heat build-up in tire service. Lithium-catalyzed low-cis grades have a higher vinyl content of 10–15 % and a glass transition temperature of -95 °C to -90 °C. This architectural difference raises wet-grip potential at low temperature but also increases rolling resistance. The molecular weight distribution is broader for neodymium grades, typically with a polydispersity index of 2.5–4.5 by gel permeation chromatography, whereas lithium-catalyzed grades are narrower, with polydispersity index 1.05–1.25. The broader distribution in Nd-BR improves processability in high-shear mixing without sacrificing abrasion resistance, while the narrow distribution in Li-BR gives controlled solution viscosity and reproducible grafting behaviour in styrene monomer.
| Property | Test method | High-cis Nd-BR | Low-cis Li-BR | High-vinyl Li-BR |
|---|---|---|---|---|
| cis-1,4 content | ISO 12965 | 96–99 % | 36–42 % | 15–30 % |
| vinyl content | ISO 12965 | ≤ 1.5 % | 10–15 % | 50–80 % |
| Mooney viscosity ML 1+4 at 100 °C | ASTM D1646 | 40–50 MU | 35–45 MU | 45–60 MU |
| Glass transition temperature | ASTM E1356 | -107 to -103 °C | -95 to -90 °C | -25 to -5 °C |
| Volatile matter | ISO 248-1 | ≤ 0.5 wt% | ≤ 0.5 wt% | ≤ 0.5 wt% |
| Ash content | ISO 247 | ≤ 0.5 wt% | ≤ 0.5 wt% | ≤ 0.5 wt% |
In passenger and commercial tire compounds, high-cis neodymium BR is introduced at 20–40 phr in tread formulations to lower heat build-up and improve abrasion resistance. On a 270-L intermeshing internal mixer with a fill factor of 0.72, a two-stage mix is used: the first pass combines natural rubber, BR, 50–60 phr N234 carbon black, zinc oxide at 3.0 phr, stearic acid at 2.0 phr, and 5–15 phr treated distillate aromatic extract; the dump temperature is controlled at 150–160 °C. The second pass at 95–105 °C incorporates sulfur at 1.8–2.5 phr and a sulfenamide accelerator, typically TBBS at 1.0–1.4 phr, with diphenylguanidine at 0.2–0.5 phr as a secondary accelerator. Under DIN ISO 4649, replacement of 30 phr natural rubber by high-cis BR reduces abrasion loss by 15–30 % relative to an all-NR control at equal hardness; published data for this specific configuration is limited, but the directional effect is reproducible across laboratory abrasion testers. In sidewall compounds, 20–35 phr BR improves crack growth resistance under ASTM D1052 Ross flex, although green tack falls as BR content exceeds 40 phr, requiring tackifier resin at 2–4 phr to maintain tire-building ply adhesion.
A processing limitation of high-cis BR is its lower green strength and higher cold flow compared with natural rubber. Slab handling at mill temperatures above 60 °C may require active cooling or a swing-arm conveyor to prevent sagging and deformation before extrusion. BR does not require mastication; prolonged mixing at temperatures above 165 °C can initiate gel formation in the absence of adequate antioxidant protection. Oil-extended grades with 37.5 phr TDAE or naphthenic oil are preferred when mixing energy must be reduced, because oil extension lowers the effective Mooney viscosity to 35–45 MU and improves filler incorporation without raising compound hardness.
| Parameter | Test method designation | Typical control window |
|---|---|---|
| Mooney viscosity ML 1+4 at 100 °C | ASTM D1646 / ISO 289-1 | 38–52 MU |
| Volatile matter | ISO 248-1 | ≤ 0.5 wt% |
| Ash | ISO 247 | ≤ 0.5 wt% |
| cis-1,4 content | ISO 12965 | 96–99 % |
| Vinyl content | ISO 12965 | ≤ 1.5 % |
| Tensile strength in ASTM D3189 evaluation compound | ASTM D412 | 15–20 MPa |
| Elongation at break | ASTM D412 | 400–550 % |
| DIN abrasion loss | DIN ISO 4649 | 80–120 mm³ |
This window is not a commercial specification for any single manufacturer but is representative of published data and ISO 2476 evaluation.
High-trans BR with trans-1,4 content above 90 % is semicrystalline at ambient temperature and is supplied for applications requiring shape retention, high modulus at low elongation, or controlled crystallinity. High-vinyl lithium-catalyzed BR grades shift the glass transition temperature from approximately -105 °C for high-cis BR to -25 °C to -5 °C as the vinyl content increases from 50 % to 80 %. This change in dynamic glass transition improves wet skid resistance in tread-cap compounds but raises rolling resistance; the selection of high-vinyl BR is therefore constrained by tire labelling class targets under Regulation (EC) No. 1222/2009. In a tread compound containing 30 phr high-vinyl BR, wet-grip index measured on a laboratory pendulum skid tester may improve by 3–6 %, while rolling resistance coefficient under ISO 28580 can increase by 5–10 % compared with a high-cis BR control; published data for this specific configuration is limited.
Solution-polymerized low-cis lithium BR is specified as a graft substrate in high-impact polystyrene and ABS production because its low gel content and narrow molecular weight distribution permit controlled rubber particle morphology. The critical incoming specifications are a Mooney viscosity of 35–45 MU, cis-1,4 content of 36–42 %, vinyl content of 10–15 %, gel content below 0.5 wt%, and a 5 wt% solution viscosity in styrene of 100–250 mPa·s. The rubber is dissolved in styrene at 8–12 wt% before thermal or peroxide-initiated polymerization; the prepolymer is then devolatilized in a falling-strand devolatilizer at 230–250 °C and 10–20 mbar. Rubber particle size is controlled by phase inversion during prepolymerization, with high-shear agitation in continuous prepolymerizers, typically 800–1200 s-1 shear rate, influencing final impact performance. In footwear, low-cis BR is blended with SBR or isoprene rubber at 15–30 phr to improve sole abrasion resistance; DIN ISO 4649 abrasion loss values below 120 mm³ are typical for solid sport-shoe soles, but published data for this specific configuration is limited. BR in these compounds lowers flex-cracking resistance at low temperature unless blended with a higher-cis or higher-trans elastomer.
BR cures more slowly than natural rubber in conventional accelerated sulfur systems. In a moving-die rheometer trace under ASTM D5289 at 160 °C, a typical ASTM D3189 black BR compound reaches tc90 in 8–12 min, whereas an analogous natural rubber compound reaches tc90 in 5–7 min. To balance crosslink density in NR/BR blends, sulfur is maintained at 1.8–2.5 phr and the accelerator ratio is adjusted, for example TBBS at 1.0–1.4 phr with diphenylguanidine at 0.2–0.5 phr. BR-rich compounds are sensitive to reversion-free cure only with a semi-efficient sulfenamide system; at 180 °C, ASTM D5289 maximum torque may decline due to chain degradation. Compared with EPDM, BR offers diene cure compatibility without peroxide, but it lacks saturated-backbone heat aging resistance; after 70 h at 100 °C under ASTM D573, tensile strength of an unprotected BR compound may fall by 20–35 %, whereas an EPDM compound retaining 80 % of original tensile strength is common. This cure-rate mismatch limits sulfur-cured BR/EPDM co-vulcanization to EPDM grades with ethylidene norbornene contents of 8–10 wt% and requires staged mixing to avoid curative migration. In SBR/BR blends, phase morphology is less problematic because both are non-polar and share similar solubility parameters, but SBR accelerates cure slightly relative to BR, and the low-temperature glass transition of the blend shifts downward as BR content increases, which reduces wet grip while improving abrasion resistance.
When BR is used in industrial products such as conveyor belt covers or anti-vibration mounts, the operational boundary is set by its low resistance to aromatic oils and its poor hot tear strength. The compound is reinforced with 50–70 phr N330 or N550 carbon black, and antioxidant packages based on hindered phenols and thioesters are required for service above 80 °C. Sulfur blooming can occur at sulfur levels above 2.5 phr in low-cis BR compounds, so a semi-efficient cure system is preferred. These constraints distinguish BR from natural rubber, which has higher green strength and better hot tear resistance, and from EPDM, which requires peroxide curing but withstands heat aging more effectively.
