Bada AG BADAFLEX® SEBS-Comp. TPE-S 40A 1279 GR is presented as a styrenic thermoplastic elastomer compound based on a poly(styrene-ethylene/butylene-styrene) block copolymer. The grade designation places the material in the 40 Shore A hardness class, while the 1279 GR suffix identifies a proprietary variant supplied as granulate. Published data for this specific configuration is limited; grade-specific values from the producer’s certificate of analysis and technical datasheet take precedence over the contextual property windows provided here. The saturated ethylene/butylene midblock removes main-chain unsaturation and thereby reduces oxidative degradation and ozone sensitivity relative to styrene-butadiene-styrene compounds. Under ozone exposure according to ISO 1431-1, stabilized SEBS compounds commonly withstand 72 h at 40 °C and 50 pphm without visible cracking, whereas unstabilized SBS may require higher antiozonant loadings to approach equivalent performance.

The 40 Shore A hardness is determined by durometer under ISO 48-4 or ASTM D2240 on test plaques conditioned at 23 ± 2 °C and 50 ± 10 % relative humidity. In low-hardness SEBS-TPE-S compounds, durometer readings can shift with oil loss, surface bloom, or excessive regrind content. For repeatable readings, fresh surface cuts and calibrated durometers are required. Hardness alone is not sufficient for function; compression set, tensile set, and stress-strain response are required to predict elastic recovery in service.

The ranges in the table are not grade-specific. The actual BADAFLEX 40A 1279 GR formulation may contain selected fillers, stabilizers, or processing aids that shift density, tear strength, or compression set into a narrower specification band. When the grade is considered for an application, the supplier control plan should be used for incoming inspection, and specimen preparation should follow the same test method designations as the producer’s data sheet.

How Does the Nominal 40 Shore A Hardness Influence Seal Retention and Tactile Response?

In sealing applications, the installed force of a soft TPE gasket declines over time through stress relaxation and compression set. Compression set measured per ISO 815-1 after 22 h at 70 °C is therefore the primary screening parameter. A value above 60% may be acceptable in a static grip overmoulding but is usually undesirable in a dynamic seal because leakage paths develop at low interference. The elastic recovery after short-term compression is influenced by the styrenic domain content and the molecular weight of the ethylene/butylene midblock. Softer compounds at 40 Shore A often require higher molecular weight SEBS or selective partial crosslinking to achieve the same sealing force retention as a 50 or 60 Shore A variant.

For tactile overmoulding on polypropylene or polycarbonate, the low hardness reduces peak contact pressure and improves conformability. Adhesion to the substrate is not an inherent property of the TPE; it is developed by melt fusion at the interface and is sensitive to substrate surface temperature, mould release residue, and the presence of an amorphous skin on the insert. Production-scale adhesion testing is commonly performed by peel adhesion according to ISO 813 or ASTM D429, but pass criteria are part-specific. A processing boundary emerges because raising melt temperature to improve adhesion can degrade the oil-extended SEBS phase. Exceeding 250 °C may volatilize plasticizer and produce surface splay, creating a conflict between bond strength and optical quality.

Field data from injection moulding lines indicate that batch-to-batch viscosity differences in soft SEBS-TPE-S compounds appear primarily as screw recovery time changes. A shift of 10% in oil or plasticizer content can change melt viscosity sufficiently to require adjustment of screw back pressure from 20 bar to 50 bar to avoid air entrapment and inconsistent shot volume. Melt volume-flow rate is often quantified according to ISO 1133-1:2022 at 230 °C with a 2.16 kg or 5 kg load, but the exact condition must match the producer’s datasheet. A single MFR point does not capture the shear-thinning behavior relevant to thin-wall filling; capillary rheometry across shear rates from 100 s⁻¹ to 10,000 s⁻¹ reveals the rapid viscosity reduction that permits injection filling with moderate clamp force.

Material handling and pre-drying are not secondary steps for soft SEBS compounds. Although the SEBS midblock is hydrophobic, surface condensation and silo-bound moisture can become visible as splay or porosity when the granules are processed at elevated melt temperatures. Pre-drying is recommended when ambient relative humidity exceeds 60% or when regrind fraction is higher than 30%. A desiccant dryer set to 60 °C to 80 °C for 2 h to 4 h with a dew point below -20 °C is commonly used for comparable SEBS-TPE-S grades. Residence times above 4 h at 80 °C can lead to agglutination of low-hardness pellets, hopper bridging, and feed throat sticking on production lines.

When the Grade Is Processed Through a Reciprocating-Screw Injection Moulding Line

Comparative process windows for SEBS-TPE-S compounds place melt temperature between 190 °C and 230 °C. A general-purpose polyolefin screw with 20:1 to 25:1 L/D and compression ratio of 2.5:1 to 3.5:1 typically provides sufficient homogenization without excessive shear heating. The low hardness of 40 Shore A compounds lowers screw friction and may extend recovery time. Adding back pressure from 20 bar to 50 bar can improve melt homogeneity but also increases residence time. If the non-return valve is worn, low-viscosity SEBS melt leaks backward during injection, producing short shots and inconsistent cushion. Production-scale troubleshooting therefore begins with verifying check ring clearance and cushion stability before temperature profile changes.

Injection velocity should be moderate to high because the compound undergoes shear thinning. Gates below 0.8 mm for soft SEBS grades can generate high shear rates and melt fracture, visible as matte streaks or rough gate vestige. To fill thin walls, raising injection speed while lowering melt temperature within the allowed window often improves flow length and reduces flash. Mould temperature typically remains between 20 °C and 40 °C; for polished surfaces, a mould surface temperature up to 50 °C can improve replication and adhesion without excessive cycle-time penalty. Holding pressure must be reduced relative to semicrystalline polyolefins because compressibility of SEBS elastomer melts is higher. Overpacking causes flash, part sticking, and dimensional distortion. Pack pressure profiles can be optimized by cavity pressure sensors: the switch-over point should occur at 95% to 98% of filled volume, with holding time equal to the observed gate freeze time.

Runner and gate design changes with 40 Shore A materials. Because the compound is compressible and low-durometer, the runner should be full-round or trapezoidal with polished surfaces; sharp corners create dead spots and black specks. Gate thickness should be between 50% and 70% of the wall thickness, and gate length should be as short as possible to avoid premature freeze. Vent depths for SEBS compounds are typically 0.01 mm to 0.02 mm; larger vents cause flash because of low melt viscosity. On production lines, flash at the parting line often indicates either worn clamp force below design tonnage or excessive melt temperature. Effective cavity pressure during packing for soft TPE-S often falls between 200 bar and 400 bar, lower than rigid polyolefins.

Chemical service boundaries for SEBS-TPE-S differ from polar elastomers. Prolonged direct contact with aromatic hydrocarbons, esters, ketones, or chlorinated solvents can extract the oil phase and cause shrinkage and hardening. Chemical resistance must be evaluated according to ISO 175 with the actual contact fluid; a generic oil resistance claim is not valid for SEBS unless the producer supplies specific test data. In automotive or industrial service, mineral oil at elevated temperatures may swell the compound; continuous exposure above 70 °C in hot oil requires alternative chemistries such as crosslinked TPV or nitrile-bearing TPE. The compound should not be combined with peroxide masterbatches or strong free-radical generators unless explicitly specified by the producer, because uncontrolled crosslinking or chain scission can alter hardness, gel content, and surface appearance. Amine-based additives and accelerators are generally outside the intended formulation of SEBS compounds and should be avoided in adjacent rubber compounds to prevent contact contamination.

Volume-Filled SEBS Versus Crosslinked TPV and Segmented TPU

The main differentiation of BADAFLEX SEBS-Comp. TPE-S 40A 1279 GR from a crosslinked TPV at the same nominal hardness is melt recyclability and lower density. TPVs based on dynamically vulcanized EPDM in polypropylene typically offer lower compression set at 125 °C when tested according to ISO 815-1, but they have a higher processing melt temperature and may show flow marks in thick sections. SEBS compounds can be reprocessed as regrind more readily because there is no thermoset rubber phase; the melt contains a physically crosslinked network of styrenic domains that re-forms upon cooling. This physical network limits continuous service temperature relative to TPVs. SEBS-TPE-S grades are generally specified for continuous service below 90 °C to 100 °C unless the producer’s data indicates otherwise, while many EPDM/PP TPVs can withstand 120 °C to 135 °C in static applications.

Relative to TPU, the SEBS compound has lower density, often 0.89 g/cm³ to 1.10 g/cm³, compared with 1.15 g/cm³ to 1.25 g/cm³ for polyester-based TPU, and it offers a dry-touch low-temperature flexible response. TPU is superior in abrasion resistance, tensile strength, and fuel/oil resistance. For applications requiring ISO 4649 abrasion loss below 50 mm³ or contact with ASTM Reference Fuel C, a TPU or other specialty elastomer is generally required. Against SBS-based TPE-S, the SEBS grade provides improved UV and oxidation resistance because the ethylene/butylene midblock is saturated, but it can be more oil-extended and may have lower green strength. Compared with plasticized PVC, SEBS-TPE-S often avoids phthalate plasticizers in many formulations, but oil extraction can still occur. Density is generally lower than PVC-P, which commonly ranges from 1.20 g/cm³ to 1.35 g/cm³. Relative to silicone rubber, SEBS-TPE-S is melt-processable on standard thermoplastic equipment and can be co-injection overmoulded without a crosslinking step, but silicone rubber provides better high-temperature compression set and autoclave resistance. The choice between SEBS and silicone is often decided by ISO 815-1 compression set after repeated autoclave cycling; silicone can maintain sealing force at 121 °C to 134 °C, while SEBS may show progressive stress relaxation.

Regulatory documentation for the granulate is incomplete without the final article specification. REACH registration under EU 1907/2006 and RoHS screening under 2011/65/EU Annex II are supplier-level declarations; SVHC content should be confirmed with the producer or importer. The material is not automatically suitable for food contact, medical, or potable water service. If the application requires food contact compliance, the exact compound must be listed in the producer’s EU 10/2011 declaration of compliance. For medical devices, ISO 10993-5 and ISO 10993-10 testing is performed on the finished sterilized component, not on the raw granulate alone; sterilization method, dosage, and post-sterilization aging influence biocompatibility. Halogen-free claims require verification because flame-retardant or mineral-filled variants may contain halogens at trace levels.

An application scenario in which a low closure force sealing ring is overmoulded onto a polypropylene housing illustrates the interaction of these properties. The seal must be evaluated for compression set per ISO 815-1, adhesion per ISO 813, and dimensional change after conditioning in the intended cleaning agent. If the seal is exposed to quaternary ammonium disinfectants at 60 °C, chemical resistance should be tested according to ISO 175 for the actual contact time and concentration. Finished article validation remains the end user’s responsibility; the raw granulate datasheet provides only the initial material property window.