Bada AG BADAFLEX® SEBS-Comp. TPE-S 60A 5123 FR S1 is a pellet-form styrenic block copolymer thermoplastic elastomer based on a hydrogenated styrene-butadiene-styrene block copolymer matrix. The name places the compound in the 60 Shore A hardness class under ISO 868:2003 or ASTM D2240-15; the styrenic end blocks form physical crosslinks at service temperatures, while the ethylene-butylene midblock provides elastomeric recovery, oxidative stability, and greater resistance to chain scission than unsaturated SBS block copolymers. The “FR S1” suffix signals a flame-retardant modification. It does not reference a single test result; the relevant classification path may include UL 94 vertical burning, IEC 60695-11-10 flame exposure, or DIN EN 45545-2 railway-materials requirements. The definitive rating and thickness dependency must be read from the manufacturer’s certificate or yellow card.

The product belongs to the group of TPE-S compounds in which an SEBS network is extended with process oil and modified with fillers, stabilizers, and flame-retardant additives. Because the designation contains 60A, the material is expected to provide a Shore A durometer reading of approximately 60 when measured after 15 s on a specimen of at least 6 mm thickness. The flame-retardant package normally increases density relative to a non-FR SEBS; typical results can exceed 1.0 g/cm³ under ISO 1183-1:2019. Published data for this specific configuration is limited, so tensile strength, elongation at break, tear resistance, and compression set should not be inferred from general-purpose SEBS grades.

The compound is used where flexible design, polyolefin adhesion, flame resistance, and low fume performance are specified. Candidate applications include cable harness strain-relief grommets, gaskets for enclosures, edge protectors, industrial profiles, and interior mass-transit or building components. In automated high-volume production, the material is processed on injection molding and extrusion lines; its positioning is different from EPDM/PP thermoplastic vulcanizates, thermoplastic polyurethanes, and plasticized PVC in terms of density, low-temperature flexibility, compression set, and flame-retardant stability.

What thermal and rheological constraints are introduced by the flame-retardant system?

Flame-retardant SEBS compounds have a narrower melt corridor than unfilled SEBS because flame-retardant additives and their synergists can decompose, volatilize, or migrate at temperatures that are only moderately above the polymer’s normal melt-processing range. For 60 Shore A SEBS, melt temperatures are commonly held between 180 °C and 220 °C. The lower boundary is set by melt homogeneity and the upper boundary by additive degradation, surface bloom, or acid formation from halogenated systems. If no grade-specific profile is available, a starting melt temperature of 190 °C is used, with cylinder zones maintained at 180 °C to 210 °C and the nozzle set at 200 °C. The exact limits for BADAFLEX® SEBS-Comp. TPE-S 60A 5123 FR S1 must be confirmed from the Bada AG processing datasheet because the flame retardant chemistry can shift the upper limit downward.

Melt viscosity of SEBS compounds decreases strongly with shear rate. In capillary rheometry, a 60 Shore A SEBS grade may display a viscosity of roughly 100 Pa·s to 300 Pa·s at 1000 s^-1 and 200 °C, but published data for this specific configuration is limited. The power-law index is generally between 0.35 and 0.55, meaning flow is shear-thinning and will respond to injection-speed changes. In injection molding, filling speed should be limited at the start to avoid jetting and then increased to keep flow-front velocity above 200 mm/s in thin sections. Holding pressure is typically 30 % to 60 % of the injection pressure, with holding time adjusted to gate freeze-off; if the FR filler raises thermal conductivity, gate freeze time may be shorter than a non-FR SEBS.

Tool and runner design should anticipate the shear-thinning response. Cold-runner systems are usually sized with full-round runners of 4 mm to 6 mm for medium-sized parts, and gate land lengths are kept below 1.0 mm to prevent premature freeze-off. Hot-runner manifolds should be operated no higher than the upper melt-temperature limit; melt residence time above 200 °C should be kept below 15 min to limit yellowing and additive migration. For multicavity tools, flow balancing is critical because flame-retardant fillers increase viscosity sensitivity to local shear history and can shift the filling pattern relative to unfilled SEBS.

Moisture control is an operational boundary. SEBS itself is non-hygroscopic, but halogen-free intumescent or metal-hydrate flame-retardant packages can absorb surface moisture during storage. If ambient relative humidity exceeds 60 % or containers have been opened for more than 8 h, the compound should be pre-dried in a desiccant dryer at 70 °C to 80 °C for 2 h to 4 h. Insufficient drying creates splay, weld-line porosity, and variable flame-test results because hydrolysis of phosphate esters or other synergists changes the surface composition. Production-scale trials on vented injection barrels with a vent-port length of 20 mm to 25 mm show that vacuum venting reduces gas entrapment but cannot replace proper pre-drying.

Clamp-force requirements for 60 Shore A SEBS are commonly estimated at 0.4 t/cm² to 0.6 t/cm² of projected area, but thin-wall parts with high L/t ratios may require 0.8 t/cm² when the melt is processed near the lower temperature boundary. Screw back pressure in metering is set at 5 bar to 10 bar hydraulic to homogenize the flame-retardant dispersion without excessive shear heating; screw rotation should be selected so that melt temperature does not rise more than 5 °C above the cylinder set point. Vented barrels with active vacuum of 80 mbar to 120 mbar are used where monolayer parts are produced from hygroscopic FR packages.

For extrusion, a single-screw extruder with L/D ratio 24:1 to 30:1, a compression ratio of 2.5:1 to 3.5:1, and a screen pack with 60/80/60 mesh configuration is commonly used for SEBS profile compounds. The flame-retardant version may require a lower screw speed and a breaker plate with generous flow passages to reduce shear heating. If a side-fed compounded FR masterbatch is used, the side feeder must be placed after the polymer melt seal to prevent low-bulk-density additives from blowing back through the main feed. This practice is documented on twin-screw lines with L/D ratios of 40:1 to 44:1; barrel wear in the side-feed zone is monitored because mineral-based flame-retardant fillers increase abrasion.

Regrind usage requires particular attention. Flame-retardant additives can become partially degraded or migrate during multiple heat histories, producing lower tensile elongation and changed flame classification. A conservative starting level is 10 % regrind blended with virgin pellets; higher fractions should be validated by complete mechanical and flammability testing. In production, batch-to-batch variation is minimized by using loss-in-weight feeders with a tolerance of ±0.5 % on additive addition and by sealing the edge trim for immediate reuse.

Comparative property and processing differentiation against non-FR SEBS, TPV, TPU, and PVC-P

The flame-retardant SEBS grade differs from a non-FR 60 Shore A SEBS primarily in density, flow behavior, surface quality, and flammability. The incorporation of a char-forming or endothermic flame-retardant system typically raises the compound density by 0.05 g/cm³ to 0.15 g/cm³ and reduces melt flow length under a fixed injection pressure. It may also lower elongation at break and increase tear sensitivity at weld lines. These effects are additive-package dependent and not unique to this product; the Bada AG datasheet should be used for comparative values.

Against an EPDM/PP thermoplastic vulcanizate of the same hardness, the SEBS grade has lower density, better surface appearance, higher colour consistency, and more consistent overmoulding adhesion to polyolefins. It also flows more easily into long or thin flow paths at lower melt temperatures. However, the SEBS midblock is non-polar and aliphatic, so the compound swells in mineral oil and is not suitable for continuous contact with hot hydrocarbon fluids. A TPV generally provides better hot-oil resistance and can retain tensile properties at higher continuous-use temperatures; the SEBS grade is preferred where low-temperature flexibility and low compression set are required without high oil exposure.

Compared with a 60 Shore A thermoplastic polyurethane, the SEBS compound offers lower density, better moisture stability, easier drying, and a wider processing window. It also reduces the risk of viscosity drift caused by absorbed moisture that can hydrolyze ester-based TPU in the barrel. The trade-off is lower abrasion resistance, lower tear propagation resistance, and lower resistance to fuels and polar solvents. In conveyor or wheel applications demanding abrasion, TPU is usually selected; in seals or grommets where chemical resistance is secondary and stable electrical insulation is required, the SEBS-FR grade may be more appropriate.

Compared with plasticized PVC-P, the SEBS compound contains no ortho-phthalate plasticizer and therefore avoids plasticizer migration, low-temperature stiffening, and extraction fogging. It is often preferred for interior automotive or rail parts that require low volatile organic compound emissions. However, PVC-P is generally lower in cost and has inherent flame resistance due to chlorine; a halogen-free SEBS-FR grade may require a higher loading of non-halogenated flame retardants, which can raise hardness and density. The difference in density and material cost must be evaluated against processing energy and secondary operations.

Within the TPE-S family, the difference between SBS and SEBS should be considered. SBS has unsaturated polybutadiene midblocks and is more susceptible to thermo-oxidative degradation, yellowing, and viscosity drift. SEBS, as in this grade, is hydrogenated and generally requires less antioxidant protection than SBS, but the hydrogenation increases melt viscosity at equal hardness. The 60 A hardness indicates a soft segment volume that supports high elongation and elastic recovery; harder grades in the Badaflex series would provide higher modulus but lower flexibility for sealing or strain-relief use.

Flexible cable jacketing, strain-relief boots, enclosure gaskets, and interior rail or building profiles are typical application routes. For electrical and electronic equipment, the material may be evaluated under IEC 60695-2-12 at glow-wire temperatures of 650 °C or 750 °C, depending on the end-product standard. In railway vehicles, TPE-S materials are screened under DIN EN 45545-2 for hazard levels using parameter groups such as R22, R23, and R24; the “S1” label may refer to smoke production category or to an internal Bada AG flame-retardant series. Building-sector seals may require classification under EN 13501-1, where smoke classes include S1, S2, and S3. A manufacturer test report is necessary before specifying this grade in escape-route or load-bearing applications.

The product’s non-polar SEBS structure gives inherently good electrical insulation and low moisture uptake. Surface resistivity and volume resistivity values should be taken from the supplier’s data because flame-retardant fillers can reduce resistivity if they contain conductive or hygroscopic species. For high-voltage connector boots, partial discharge behaviour and tracking resistance under IEC 60112 may be relevant. For outdoor seals, weathering resistance should be confirmed under ISO 4892-2:2013 cycles, but published data for this specific configuration is limited.

For cable coating, the grade may be extruded as a jacket over polyolefin insulation; adhesion to polyolefins is generally good without a separate adhesive layer, which reduces production steps. The flame-retardant package may affect surface roughness and printability; laser marking contrast and ink adhesion should be trialled because some FR additives exude to the surface over time. In injection moulded connectors, mould shrinkage is anisotropic and should be determined on a cavity-specific basis. A post-mould conditioning time of 24 h at 23 °C and 50 % relative humidity according to ISO 291:2008 is suggested before dimensional verification.

If halogen-free low-smoke certification or railway compliance is a project requirement

The suffix “FR S1” is not a complete regulatory statement. It does not confirm halogen-free chemistry or a specific smoke-density result. A compound may contain halogenated retardants and still be designated FR by the supplier. For projects requiring low acid-gas generation, low smoke optical density, or compliance with halogen-free specifications, the Bada AG datasheet and a third-party test report for EN ISO 4589-2 limiting oxygen index, IEC 60754-1, IEC 60754-2, or DIN EN 45545-2 smoke-density methods should be requested. If the material is intended for railway interiors, the manufacturer should provide a certified hazard level rather than a generic FR S1 label.

When switching from a general-purpose SEBS to the flame-retardant grade, melt rheology changes can require gate-size revisions. A gate diameter of 1.0 mm to 2.5 mm for a typical grommet may be adequate, but high flame-retardant filler concentration can lower the effective flow length. Parts with wall thickness below 1.5 mm should be evaluated for flow hesitation, weld-line weakness, and flame-test edge effects. In flame-retardant compounds, skin-core morphology may differ from the core because fillers align during filling; burn-test reproducibility can therefore be affected by gate location and weld-line distribution.

In compounding, the additive system must be dispersed without exceeding local melt temperatures that cause degradation. Twin-screw extruders with segmented screws and moderate shear kneading blocks are preferred; high-shear kneading elements can generate local temperatures above 240 °C, which is undesirable for many SEBS flame-retardant packages. The avoidance of amine-based stabilizers or certain halogenated synergists may be necessary to prevent premature crosslinking or acid generation. The manufacturer’s formulation is proprietary, but production records should track melt pressure at the die and specific energy input as indicators of dispersion consistency.

Because SEBS is a non-polar hydrocarbon elastomer, the compound is limited in resistance to mineral oils, aromatic solvents, and chlorinated hydrocarbons. Swelling in aggressive media can exceed 50 % by mass. It should not be used for prolonged load-bearing exposure above 120 °C; creep and stress relaxation become significant. For outdoor service, UV stabilization is required despite the hydrogenated midblock, and black or pigmented formulations are recommended under ISO 4892-2:2013 accelerated weathering. Post-mould shrinkage and anisotropy are higher than in rigid thermoplastics; dimensional checks should be performed after 24 h at 23 °C and 50 % relative humidity. Published data for this specific configuration is limited, so critical design values must be obtained from Bada AG’s current technical datasheet or through application-specific moulding trials.

Batch-to-batch variance in flame-retardant dispersion may appear as surface mottling or variation in burn-test results. Incoming-material quality audits should include melt mass-flow rate under ISO 1133-1:2022, hardness under ISO 868:2003, density under ISO 1183-1:2019, and a small-scale flammability check against the production reference. The audit limits should be derived from a process capability study of at least 25 consecutive batches. Without such data, a one-point specification is insufficient for critical flame-retardant components.