Bridgestone Corporation

Bridgestone Corporation-sourced solution-polymerized styrene-butadiene rubber and high-cis polybutadiene rubber grades are compounded into downstream rubber and polymer-modified materials where filler dispersion, cure kinetics, and dynamic mechanical response determine final part performance. The following application scenarios address processing conditions, regulatory constraints, formulation ratios, and terminal articles across six manufacturing sectors. Published data for this specific supplier configuration is limited in some areas; where that occurs, the absence of publicly verifiable figures is stated instead of generating unverified values.

What Changes When High-Cis BR Is Blended with SSBR in Tread Compounds?

Bridgestone Corporation-sourced SSBR grades with terminal chain-end functionalization are typically used in passenger car radial tread formulations because the functional group reacts with silanol groups on precipitated silica and reduces filler-filler networking. The ratio of SSBR to high-cis BR commonly ranges from 60:40 to 80:20, depending on whether the tread must prioritise wet grip or rolling resistance. Compounding uses precipitated silica at 70–85 phr, carbon black N234 or N330 at 5–15 phr, bis[3-(triethoxysilyl)propyl] tetrasulfide at 6–8 phr, TDAE oil at 15–25 phr, zinc oxide at 2.5–3.0 phr, stearic acid at 1.0–2.0 phr, sulfur at 1.5–1.8 phr, CBS at 1.5–2.0 phr, DPG at 1.5–2.0 phr, 6PPD at 1.5–2.0 phr, and antiozonant wax at 1.0 phr. The compound Mooney ML 1+4 at 100 °C measured to ASTM D1646-19a is generally held between 55 and 80 MU to retain extrudate dimensional stability while allowing adequate filler incorporation.

Processing in a 270L tangential internal mixer with a fill factor of 0.70–0.75 and rotor speed of 35–45 rpm typically requires a two-stage sequence. The first stage drops at 150–160 °C after the silane coupling reaction has been held above 140 °C for 60–90 s; dropping below this window leaves unreacted TESPT, while exceeding 170 °C initiates premature vulcanization and generates gel particles. A remill stage at 140–150 °C improves silica dispersion, and the final stage on a two-roll mill at 90–100 °C incorporates sulfur and accelerators. Extrusion is typically performed on a cold-feed pin barrel extruder with L/D 18:1–20:1 at screw speeds below 25 rpm to avoid scorch; die swell can increase by 10–15 % if the BR content exceeds 40 phr without raising filler loading.

Performance thresholds for a tread compound with an SSBR to BR ratio of 70:30 typically include tan δ at 0 °C above 0.25 and tan δ at 60 °C below 0.10 when measured by dynamic mechanical analysis at 1 Hz and 0.1 % strain. Abrasion resistance tested to ISO 4649:2021 usually falls between 80–120 mm³ for silica-rich tread formulations; if the sample falls outside this range, mixing quality or silane coupling efficiency should be investigated. Tensile strength to ISO 37:2017 is normally above 15 MPa for laboratory sheets cured at 160 °C for t90 plus 2 min. The following comparative target windows are used for initial screening:

Regulatory compliance for passenger tire tread compounds exported to the EU must account for the tyre labelling regulation EU 2020/740, which replaced EC 1222/2009, and rolling resistance, wet grip, and external noise values must be generated on standardized reference test tyres. REACH Annex XVII entry 50 restricts polycyclic aromatic hydrocarbon content in extender oils, requiring TDAE oils with less than 1 mg/kg benzo[a]pyrene and 10 mg/kg sum of eight PAHs. The finished tread compound is not a food-contact article; therefore FDA 21 CFR clearance is not applicable. Terminal articles include passenger car radial tire treads, light truck tire treads, and racing tire tread compounds where high-temperature hysteresis control is critical.

In high-impact polystyrene suspension or bulk polymerization, Bridgestone Corporation-sourced low-solution-viscosity BR with controlled gel content is dissolved in styrene at 5–10 wt% before free-radical polymerization begins. Published data for this specific supplier configuration is limited in open literature; typical reactor feed uses BR with Mooney ML 1+4 at 100 °C of 35–55 MU and a 5 wt% styrene solution viscosity of 60–120 cP, measured by a Brookfield viscometer at 25 °C. During polymerization at 110–130 °C, phase inversion occurs when the styrene phase becomes continuous and the rubber phase precipitates into particles of 0.5–3.0 µm; shear rate in the prepolymerizer, usually 100–300 s⁻¹, controls the particle size distribution. Mineral oil at 1–3 wt% is added to adjust melt viscosity; excessive oil addition above 4 wt% lowers Vicat softening temperature and reduces rubber phase crosslinking.

Finished HIPS test methods include notched Izod impact strength to ASTM D256-23, tensile strength to ASTM D638-22, and melt flow index to ASTM D1238-20 under 200 °C/5.0 kg. Food-contact grades require compliance with FDA 21 CFR 177.1640 and EU Regulation EU 10/2011 for plastic materials intended to contact food. End products include refrigerator liners, packaging trays, appliance housings, and single-use cutlery; the BR content in HIPS normally ranges from 6 to 12 wt% depending on required impact strength and melt flow balance.

Two-stage mixing stabilises cut growth in BR-rich conveyor belt cover compounds

Conveyor belt cover compounds for aggregate and port terminal service are usually formulated with a blend of natural rubber and Bridgestone Corporation-sourced high-cis BR at 60:40 to 70:30 because the BR fraction reduces abrasion loss but increases cut growth when the blend exceeds 40 phr. Carbon black N220 or N234 at 45–55 phr, plasticizer at 5–10 phr, zinc oxide 4–5 phr, stearic acid 2 phr, TMQ 1.5 phr, 6PPD 1.5 phr, sulfur 2.0–2.5 phr, and CBS 1.0–1.5 phr are used. Test sheets cured to ISO 37:2017 should have tensile strength above 18 MPa and elongation at break above 400 %; abrasion resistance to ISO 4649:2021 is typically below 100 mm³ for well-dispersed N220 compounds. The two-stage mixing sequence stabilises cut growth by improving carbon black microdispersion and reducing the number of undispersed agglomerates that act as crack initiation sites under repeated flexing.

Processing in a 270L tangential internal mixer with a fill factor of 0.70 uses a masterbatch dump temperature of 140–150 °C and a final stage at 90–100 °C on a two-roll mill; the final sheet is calendered onto EP100–EP250 fabrics at 70–80 °C. The calender gap is set to 0.8–1.2 mm over the fabric thickness; variation in cover thickness beyond ±0.1 mm produces tracking errors at the finishing line. Vulcanization in a continuous rotocure at 150–160 °C requires 20–30 min depending on cover gauge; a cure rheometer trace to ISO 6502-2:2018 should show t90 between 8–15 min at 150 °C. Compliance for general-purpose conveyor belts includes ISO 14890:2013 for safety requirements; fire-resistant belts for underground mining require EN 14973:2015 or MSHA 30 CFR Part 14 depending on the jurisdiction. If the cover is intended to contact dry food, the finished belt must comply with FDA 21 CFR 177.2600 and EU 1935/2004, with migration testing under the assigned food simulant. End products include troughed conveyor belts in cement plants, port terminals, and quarry transfer stations.

For injection-moulded outsoles produced in multi-station rotary machines, low-styrene SSBR and Bridgestone Corporation-sourced high-cis BR are blended at 30:70 to 50:50; the BR-rich side controls flex fatigue, while SSBR contributes wet slip resistance. The compound contains precipitated silica at 40–55 phr, TESPT at 3–5 phr, naphthenic oil at 5–10 phr, zinc oxide 3 phr, stearic acid 1 phr, antioxidant 1 phr, sulfur 1.8–2.2 phr, and MBTS 1.5–2.0 phr. Compound Mooney ML 1+4 at 100 °C is kept between 45 and 60 MU to ensure flow length in the runner before scorch occurs. Mixing on a 110L internal mixer at a dump temperature below 130 °C prevents premature silane reaction and reduces scorch risk; the injection molding machine uses screw L/D 20:1, barrel temperature profile 70/80/85/90 °C, nozzle temperature 95–105 °C, and mould temperature 35–50 °C. Injection pressure is typically 90–120 bar and holding time 5–15 s depending on sole thickness.

The final outsole is tested to ISO 4649:2021 for abrasion loss below 120 mm³, to ISO 17707:2019 for flexing endurance, and to ASTM D2240-15 for Shore A hardness of 60–70. REACH Annex XVII restricts PAH and certain phthalates in consumer articles; EU footwear falls under REACH SVHC notification if substances above 0.1 wt% are present. The finished outsole is not intended for food contact, so FDA 21 CFR 177.2600 does not apply unless the sole is part of a food-processing boot. End products include sport shoe outsoles, casual footwear, and slip-resistant work boot soles.

When cis-1,4 content exceeds 96 %, golf ball core formulations shift to zinc diacrylate cure

High-cis Bridgestone Corporation-sourced BR with cis-1,4 content above 96 % and Mooney ML 1+4 at 100 °C of 40–60 MU is used in golf ball cores because the linear macrostructure permits high zinc diacrylate loading without excessive compound viscosity. The core formulation typically contains BR 100 phr, zinc diacrylate 20–35 phr, zinc oxide 5–10 phr, antioxidant 0.5–1.0 phr, and dicumyl peroxide 0.8–1.5 phr. Fillers such as tungsten or barium sulfate at 10–20 phr may be added to adjust density and moment of inertia; published data for this specific supplier configuration is limited, so exact density targets must be verified on core samples.

Mixing requires an internal mixer with temperature controlled below 80 °C because the peroxide half-life at 100 °C is short enough to create scorch; the batch is dropped at 75–85 °C. The compounded stock is extruded as a rod or preform, then compression moulded at 150–160 °C for 10–15 min. Core hardness measured to ASTM D2240-15 typically falls at Shore D 40–50, and rebound resilience measured to ASTM D2632-15 is above 70 %. The finished core is tested for compression deflection and initial velocity, but exact test protocols are proprietary to ball manufacturers. Golf balls are sporting goods; EU REACH and U.S. TSCA apply to chemical substances in the core, but no FDA food-contact clearance is required. Zinc diacrylate is subject to normal industrial hygiene controls. End products include two-piece and three-piece golf ball cores and practice ball cores.

Engine mount compounding with SSBR/BR blends and fatigue-critical filler distribution

Engine mount and body mount compounds using Bridgestone Corporation-sourced SSBR/BR blends are formulated for dynamic stiffness, damping, and fatigue resistance rather than abrasion. A typical starting point uses NR 60–70 phr, SSBR 15–20 phr, BR 15–20 phr, carbon black N330 or N550 at 35–45 phr, naphthenic oil at 5–10 phr, zinc oxide 3–5 phr, stearic acid 1–2 phr, 6PPD 1–2 phr, sulfur 1.5–2.0 phr, and CBS 1.0–1.5 phr. The filler distribution must be uniform; unmilled black agglomerates above 10 µm act as crack initiation sites during high-cycle fatigue testing. Processing uses a 160L intermeshing internal mixer with a fill factor of 0.72–0.78 and a first-stage dump temperature of 145–155 °C; the final stage on a two-roll mill at 85–95 °C prevents accelerator degradation.

The compound Mooney ML 1+4 at 100 °C is controlled between 40 and 60 MU to allow transfer molding into multi-cavity tools. Vulcanization is typically at 150 °C for t90 plus 3 min; mould design must avoid entrapped air because the high viscosity of the SSBR/BR fraction can trap gasses at knit lines. The finished mount is tested to ISO 7743:2017 for compression stress-strain, ISO 4664-1:2011 for dynamic properties, and ISO 1817:2015 for fluid resistance. Compliance depends on the OEM specification; under-hood parts are not food-contact articles, and REACH Annex XVII restrictions on PAH in extender oils apply. End products include engine mounts, transmission mounts, and chassis bushings.