SBR Sponge
Grade
also Buna-S
Sponge = sponge / closed-cell foamed SBR
Choose for low-force sealing, gasketing, padding and insulation where compressibility, not strength, is the requirement.
Values for the Sponge condition
Other SBR grades and fills
SBR is listed in 14 conditions; see the grade overview at SBR.
Compare all 14 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
SpongeThis page Sponge / closed-cell foamed SBR | Choose for low-force sealing, gasketing, padding and insulation where compressibility, not strength, is the requirement. | — | 2 | 200 | 20 Shore A |
Shore A 40 | Pick for soft seals, low-closure-force gaskets and cushioning where high flexibility matters more than strength. | — | 9 | 550 | 6 Shore D |
Flame-retardant SBR compound | Use for underground mining belts, cable jackets and transit parts requiring flame and smoke ratings. | — | 10 | 300 | 70 Shore A |
Shore A 50 | Balanced softness and strength for flexible gaskets, diaphragms and vibration pads. | — | 12 | 480 | 8 Shore D |
Oil-extended SBR | Pick when processing softness and cost per volume matter (tire treads, soft mats); oil lowers strength and increases extractables. | — | 13 | 480 | 55 Shore A |
SHA60Default Shore A 60 | Default workhorse compound for mats, gaskets, hose covers and molded goods needing wear resistance at lowest cost. | — | 15 | 400 | 12 Shore D |
Weather/ozone-protected SBR | Specify for outdoor-exposed mats, seals and covers; antiozonant/wax and high black loading slow cracking but SBR still ages faster than EPDM. | — | 15 | 380 | 65 Shore A |
Emulsion-polymerized SBR | Default commodity raw polymer route: cheapest, easy mixing and extrusion, used in general rubber goods and truck-tire compounds. | — | 16 | 400 | 13 Shore D |
Shore A 70 | Use where extrusion resistance and wear life dominate: tire treads, conveyor covers, wheels, bushings. | — | 18 | 350 | 20 Shore D |
High-styrene SBR resin | Blended in to stiffen and harden compounds (shoe soles, hard rolls, hard mats); brittle and not elastomeric on its own. | — | 18 | 120 | 50 Shore D |
Shore A 80 | For rollers, scraper blades, skirting and pads where high stiffness and abrasion resistance are needed. | — | 20 | 250 | 28 Shore D |
SBR/NR blend compound | Blend NR in when higher tear strength, tack and lower heat build-up are needed while keeping SBR cost and wear resistance. | — | 20 | 450 | 60 Shore A |
Shore A 90 | Chosen for hard wheels, mallet faces and stiff pads; elongation and tear resistance are sacrificed. | — | 21 | 170 | 38 Shore D |
Solution-polymerized SBR | Choose for low-rolling-resistance / high-wet-grip tire treads and cleaner, more uniform compounds with silica reinforcement. | — | 22 | 450 | 15 Shore D |
What is SBR Sponge?
SBR Sponge is SBR in the Sponge grade — choose for low-force sealing, gasketing, padding and insulation where compressibility, not strength, is the requirement. SBR Sponge has a tensile strength of 2 MPa (0.218 ksi), weaker than 85% of polymer grades. Elongation at break is 200% and the elastic modulus is 0 GPa (2.18×10⁻⁴ Msi). SBR Sponge has a density of 0.45 g/cm³ (0.0163 lb/in³), lighter than 84% of polymer grades. Its glass-transition temperature is -52°C (-62 °F). SHA60 is the default condition FabDigit quotes; Sponge is available on request or by drawing note.
Advantages
- Forms and bends easily — 92/100, better than 97% of polymer grades
- Lightweight — 0.45 g/cm³ (0.0163 lb/in³), better than 84% of polymer grades
- Low embodied carbon — 3.2 kg CO₂/kg, better than 81% of polymer grades
- Ductile — tolerates forming and impact — 200%, better than 76% of polymer grades
Limitations
- Difficult to machine — 15/100, worse than 99% of polymer grades
- Needs corrosion protection — 45/100, worse than 98% of polymer grades
- High mold shrinkage — 3%, worse than 97% of polymer grades
- Low stiffness — 0 GPa (2.18×10⁻⁴ Msi), worse than 96% of polymer grades
- Poor heat conductor — 0.06 W/m·K (0.0347 BTU/hr·ft·°F), worse than 84% of polymer grades
SBR Sponge properties
Typical room-temperature values for SBR Sponge; 17 are specific to this condition. Other listed values are SBR reference data and may not represent this condition. Bars are the position among polymer grades.
Physical4
SBR Sponge has a density of 0.45 g/cm³ (0.0163 lb/in³), lighter than 84% of polymer grades. Its glass-transition temperature is -52°C (-62 °F).
Mechanical9
SBR Sponge has a tensile strength of 2 MPa (0.218 ksi), weaker than 85% of polymer grades. Elongation at break is 200% and the elastic modulus is 0 GPa (2.18×10⁻⁴ Msi).
Thermal8
SBR Sponge is rated for continuous service to 85°C (185 °F). It conducts heat at 0.06 W/m·K (0.0347 BTU/hr·ft·°F), worse than 84% of polymer grades. Thermal expansion is 220 µm/m·K (122.2 µin/in·°F).
Electrical5
SBR Sponge is an electrical insulator with a dielectric strength of 20 kV/mm (508 V/mil) and a resistivity of 1×10⁹ 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 SBR Sponge takes about 95 MJ of energy and emits 3.2 kg of CO₂ — less than 70% of polymer grades. Typical recycled content is 5%.
Manufacturability5
SBR Sponge's machinability is poor (15/100, worse than 99% of polymer grades); weldability not recommended (12/100); formability excellent (92/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SBR Sponge
Is SBR easy to machine?
Cured SBR is die-cut, waterjet-cut or ground rather than machined; use sharp knives with water/soap lubrication and freeze or backing plates for close tolerances.
Can SBR be welded?
Not weldable as a thermoplastic; join by uncured splicing and re-vulcanization, hot bonding to metal (Chemlok primers) or cyanoacrylate/contact adhesive for cured parts.
Can SBR be formed, bent or molded?
Mixed on two-roll mill/Banbury, then calendered, extruded, compression/transfer/injection molded and sulfur-cured at ~150–180 °C; good green strength and easy extrusion, but tack is lower than NR.
What surface finishes work on SBR?
Surfaces can be buffed, ground or texture-molded; use chlorination or plasma to improve paint/adhesive adhesion, and post-cure oven cycle to reduce blooming and volatiles.
SBR 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 |
|---|---|---|
| styrene (bound)23–24 % typical for E-SBR 1500/1502; ≥50 % in high-styrene resins | 15 – 40 | 23.5 |
| carbon black (N330/N550/N660)phr in the compound, not wt % of polymer | 0 – 80 | 50 |
| precipitated silicaphr; primary filler in S-SBR green-tire treads | 0 – 80 | 0 |
| process/extender oilphr; 37.5 phr in OE-SBR 1712 | 0 – 50 | 10 |
| sulfur + acceleratorsphr, sulfur cure system | 1.5 – 4 | 2 |
| zinc oxidephr activator | 3 – 5 | 4 |
| stearic acidphr activator | 1 – 3 | 2 |
| antioxidant / antiozonantphr, 6PPD/TMQ type | 0.5 – 3 | 1.5 |
| butadienebalance of the copolymer backbone | balance | — |
SBR Sponge — frequently asked
What is SBR Sponge used for?
SBR Sponge is typically used for tire treads, footwear soles, belts, gaskets and flooring. In short: lowest-cost general-purpose rubber; better abrasion than NR; tire-tread workhorse.
What is the tensile strength of SBR Sponge?
SBR Sponge has a typical tensile strength of 2 MPa (0.218 ksi) — weaker than 85% of polymer grades. Strength varies by condition: see the 14 listed tempers.
Is SBR Sponge easy to machine?
Not especially — machinability is rated poor (15/100, worse than 99% of polymer grades). Cured SBR is die-cut, waterjet-cut or ground rather than machined; use sharp knives with water/soap lubrication and freeze or backing plates for close tolerances.
Can SBR Sponge be welded?
Not readily — weldability is rated not recommended (12/100). Not weldable as a thermoplastic; join by uncured splicing and re-vulcanization, hot bonding to metal (Chemlok primers) or cyanoacrylate/contact adhesive for cured parts.
What surface finishes work on SBR Sponge?
Surfaces can be buffed, ground or texture-molded; use chlorination or plasma to improve paint/adhesive adhesion, and post-cure oven cycle to reduce blooming and volatiles.
Can SBR Sponge be formed, bent or molded?
Mixed on two-roll mill/Banbury, then calendered, extruded, compression/transfer/injection molded and sulfur-cured at ~150–180 °C; good green strength and easy extrusion, but tack is lower than NR.
What is the maximum service temperature of SBR Sponge?
SBR Sponge is rated for continuous use to about 85°C (185 °F), and briefly to 120°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- ASTM D2000 — Classification System for Rubber Products in Automotive Applications — ASTM (2020)
- ASTM D1418 — Rubber and Rubber Latices Nomenclature — ASTM (2017)
- Vanderbilt Rubber Handbook, 14th ed. — R.T. Vanderbilt (2010)
- The Rubber Formulary / Rubber Technology Handbook — Noyes / Hanser (1999)
- IISRP Synthetic Rubber Manual (SBR grade series) — IISRP (2012)
- Materials Selection in Mechanical Design (elastomer property/eco data) — Ashby / Elsevier (2019)
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.