Bada AG BADAFLEX® SEBS-Comp. TPE-S 65A 5331 is a melt-processable styrenic thermoplastic elastomer based on a styrene-ethylene-butylene-styrene block copolymer. The grade carries a nominal hardness of 65 Shore A, placing it in the medium-soft segment of TPE-S compounds intended for injection molding and extrusion. The saturated ethylene-butylene midblock provides thermo-oxidative and ultraviolet resistance relative to unsaturated SBS materials, while the styrenic end blocks form reversible physical crosslinks under melt processing. Typical application fields include soft-touch grips, sealing profiles, anti-slip pads, appliance boots, medical device housings, and consumer goods overmolded onto polyolefin substrates. The designation 5331 identifies a series-specific formulation within the BADAFLEX® range, and the SEBS-Comp. classification distinguishes it from crosslinked TPV, thermoplastic polyurethane, and commodity SBS compounds. Lot-specific values for density, tensile properties, compression set, and melt flow rate should be taken from Bada AG technical documentation; generic published ranges for this hardness class are not a substitute for batch certificates.

What technical profile distinguishes BADAFLEX® SEBS-Comp. TPE-S 65A 5331 from SBS and TPV alternatives?

The hydrogenated midblock changes long-term heat and UV behavior compared with styrene-butadiene-styrene grades. SBS compounds retain unsaturation that limits continuous service near 60–70 °C and reduces ozone resistance according to ISO 1431-1:2019; an SEBS grade typically withstands higher air-oven exposure with less discoloration and better retention of tensile properties. Compared with a PP/EPDM thermoplastic vulcanizate of equivalent hardness, the SEBS compound may present lower density, easier colorability, and lower compression set at room temperature, but TPV grades often deliver superior hot-oil and compression-set performance above 100 °C when crosslink density is optimized. Against polyester TPU, the BADAFLEX® grade has a lower density and negligible moisture sensitivity, but abrasion resistance and tensile strength are generally lower. Table 1 outlines representative property bands for medium-hardness SEBS compounds using standardized test methods; exact Bada AG lot values for 5331 must be obtained from the manufacturer.

Published data for this specific configuration is limited; the ranges above are class-typical and must not be used as release criteria for the 5331 grade.

On a reciprocating-screw injection molder with a general-purpose polyolefin screw of 20:1 to 24:1 L/D and compression ratio of 2.2:1 to 2.8:1, the melt temperature window is typically 190 °C to 230 °C, with a mold temperature of 20 °C to 50 °C. Back pressure should be maintained between 20 and 50 bar to avoid excessive shear heating; screw speed in the 80–140 rpm range is usual. Drying at 60–80 °C for 2–4 h is recommended when the material has been exposed to more than 60% relative humidity. Residual moisture above 0.05% can generate splay, surface streaks, and nozzle drool. Holding pressure, injection velocity, and gate geometry must be optimized because high shear can raise melt temperature above 250 °C and initiate chain scission in the styrenic block structure. The use of hot-runner systems is feasible, but residence time should not exceed 15 min at melt temperature. Purging with polyethylene or polypropylene is preferred after processing colored or filled resins.

Rheological characterization of medium-hardness SEBS compounds on a capillary rheometer in accordance with ISO 11443:2021 typically shows shear-thinning behavior, with apparent viscosity at 230 °C and 1000 s^-1 in the range 40–90 Pa·s for unfilled grades. Melt flow rate according to ISO 1133-1:2022 at 230 °C and 5 kg is generally between 5 and 25 g/10 min, but the exact value affects gate freeze and packing efficiency. Spiral flow tests at 2.0 mm wall thickness and 230 °C may show flow lengths in the 200–400 mm range depending on gate pressure; these values should be generated on the production tool because geometry and shear history dominate short-shot behavior. At high injection velocities producing shear rates above 10,000 s^-1, the compound can exhibit sharkskin or melt fracture. Reducing injection velocity or increasing gate diameter is preferable to raising melt temperature, because prolonged exposure above 240 °C degrades the hydrogenated midblock and shifts hardness upward.

Selection boundaries for plasticizer-free sealing and soft-touch components

BADAFLEX® SEBS-Comp. TPE-S 65A 5331 is used where a plasticizer-free, non-polar soft-touch material is required. In sealing applications such as appliance grommets and automotive interior mats, the material provides dimensional stability at service temperatures below 90 °C, but not in continuous contact with hot mineral oil or fuel. The absence of phthalate plasticizers removes plasticizer migration and fogging concerns in interior automotive applications; OEM odor and fogging requirements such as VDA 270 and VDA 278 should be confirmed on production lots. For medical device grips, the component designer must verify grade-specific cytotoxicity data according to ISO 10993-5 and whether the formulation is listed for skin-contact use. FDA 21 CFR 177.2600 compliance should not be assumed; Bada AG documentation for the 5331 lot is the controlling reference.

When insert-molded or two-shot geometries using a polypropylene substrate are produced, melt temperature should be set in the 210–230 °C band and mold temperature between 30 °C and 50 °C. Interfacial bonding is influenced by the surface cleanliness of the substrate and by the presence of mold release; silicone-based release agents reduce peel strength. The SEBS phase can wet polypropylene near its melting point, but the styrenic domains must retain enough orientation to stabilize the bond line during ejection. For applications where the substrate is ABS or polycarbonate, initial adhesion is usually lower, and a mechanical anchor, chemical primer, or co-molding design is necessary. Peel adhesion should be measured by a defined test such as ISO 8510-1 or a panel-standard 90-degree peel method. Published data for this specific 5331 configuration is limited, so production validation on the intended substrate is required.

Tooling for the 65 Shore A compound requires generous venting and polished or textured steel. Vent depths of 0.01–0.02 mm and land lengths below 1.0 mm are typical; insufficient venting causes burn marks, short shots, and gloss variation. Cold sprue bushings should have included angles of 3°–5°, and runner diameters should not fall below 4.0 mm for multi-cavity tools. Gate lands below 0.8 mm create excessive shear and surface defects. Draft angles of 1° on textured walls and 0.5° on polished walls reduce ejection stress, especially because the material is flexible and can deform under deep undercuts. Mold release sprays should be silicone-free; external release agents based on fluoropolymer may be considered only after adhesion and post-mold bonding tests.

After 168 h at 100 °C, an air-circulating oven exposure typically reveals whether the SEBS grade retains tensile strength and elongation within the application limit. For a 65 Shore A SEBS compound, retention above 80% of original tensile strength is common for plaque specimens, but the 5331 lot values should be confirmed. Compression set measured per ISO 815-1:2019, 22 h at 70 °C, is generally reported between 30% and 55% for unfilled SEBS in this hardness range; lower values are achievable with carbon black or mineral fillers but at the expense of density and soft-touch characteristics. Parts subjected to continuous clamping stress should use a compression-set target below 40% to avoid permanent thickness loss.

When regrind fractions exceed pilot-trial thresholds during sustained production

Regrind incorporation affects pressure loss, melt viscosity, and the threshold for surface defects. For a 65 Shore A SEBS compound, regrind fractions up to 20 wt% are often processable without significant shift in tensile or compression-set properties if the material is unmixed, dried, and free of dust. Above 30 wt%, the reduction in strain at break and the increase in melt flow may be measurable, especially when injection molding thin walls below 1.0 mm. Repeated thermal histories lower the molecular weight of the styrenic end blocks and reduce the physical crosslink density, causing hardness and compression set to drift. A production control plan should measure melt flow rate per ISO 1133-1:2022 at 230 °C and 5 kg, plus Shore A hardness per ISO 868, to detect lot-to-lot drift before injection-molded parts fail dimensional tolerances. Hot-runner systems and long barrel residence necessitate tighter regrind control because residence times above 10–15 min degrade the SEBS midblock and increase yellowing.

Resistance of the BADAFLEX® grade to environmental media follows the expected behavior of a hydrogenated styrenic copolymer. The material resists dilute acids, dilute bases, and many aqueous cleaning solutions at room temperature, but aromatics, ketones, esters, and chlorinated solvents can attack the styrenic or rubber phases. Ozone resistance is higher than that of unsaturated SBS grades when tested according to ISO 1431-1:2019 under 50 pphm ozone at 40 °C; ultraviolet exposure per ISO 4892-2 method A is generally suitable for indoor applications, but black or UV-stabilized compounds are required for extended outdoor service. Contact with concentrated nitric acid or strong oxidizing agents is to be avoided. Mineral oil and non-polar aliphatic oils cause swelling above 70 °C; the compound is therefore unsuitable for hydraulic sealing service.

Pigment masterbatches for the BADAFLEX® grade should be based on a carrier resin compatible with SEBS, typically polypropylene, ethylene copolymer, or SEBS-based masterbatch. Liquid colorants can create screw slippage in the feed zone; pelletized microdispersions are preferred. Avoid metal stearates during blending when precise adhesion to polypropylene is required, because migration of the lubricant can reduce bond strength. Silicone-based processing aids are generally tolerated in low concentrations below 0.5 wt%, but higher levels may reduce printability and coating adhesion. Conductive carbon black or mineral fillers can increase hardness and density; additions above 10 wt% shift hardness and modulus and should be revalidated for hardness 65 Shore A.

Production-scale failure modes observed on twin-screw compounding and injection molding lines for SEBS-type TPE-S include feed throat bridging, screw slippage, and uncontrolled frictional heating in compression zones. The 65 Shore A compound is usually pelletized into free-flowing granules, but fine dust or regrind can accumulate and obstruct hopper discharge. A desiccant dryer with dew point below -20 °C is recommended for humid ambient conditions. Barrel temperature profiles are typically flat or slightly reverse in the first two zones to avoid premature melting and feed-zone blockage. Melt temperature should be verified with a needle pyrometer during production, with alarm limits set at 245 °C to 255 °C.

Regulatory documentation for the grade should be verified against the Bada AG safety data sheet and product datasheet for the specific lot. The matrix in Table 2 lists standards frequently requested for consumer, automotive, and medical applications.

The density advantage over plasticized PVC is significant: SEBS compounds in 65 Shore A typically fall near 0.90 g/cm³, while flexible PVC can exceed 1.25 g/cm³. This difference reduces part mass by roughly 25–30% when wall thickness and mechanical design are equivalent, but tooling and melt delivery must be adjusted for lower melt density and different heat capacity. The TPE-S 65A 5331 does not require stabilizers such as those used in PVC, but it is not inherently flame-retardant; flame resistance must be formulated with FR additives that do not degrade the SEBS midblock. Prior to production release, Bada AG lot certificates for 5331 should be checked for rheology, tensile, compression set, and any application-specific regulatory statements. Processing on a high-L/D twin-screw extrusion line requires pre-validation of melt temperature and regrind limits because published data for this specific configuration is limited.