Introduced as a styrenic block copolymer compound, the model designation Bada AG BADAFLEX® SEBS-Comp. TPE-S 65A 1393 2K identifies a thermoplastic elastomer based on polystyrene-block-poly(ethylene-co-butylene)-block-polystyrene architecture, modified with processing oil, polyolefin, stabilizers, and a two-shot overmolding additive package. The product is not a generic SEBS raw polymer; the suffix 1393 2K denotes a specific formulation window intended for two-component processing, typically overmolding onto polypropylene substrates. The hardness specification 65A refers to the nominal Shore A value measured according to DIN EN ISO 868. Published data for this exact batch-specific configuration is limited; the technical statements that follow therefore distinguish between reported class behavior of 65 Shore A SEBS compounds and lot-specific certificates of analysis that must be obtained from Bada AG before production release.

Why Does the 2K Designation Reshape Mold Design and Adhesion Targets?

The two-component designation does not refer to the number of polymer phases—SEBS compounds already contain multiple phases—but to the intended use in multi-shot injection molding or overmolding. In a typical two-shot tool, the first polypropylene or PP-glass-filled carrier is molded, the mold rotates or indexes, and the BADAFLEX® material is injected over the substrate through a secondary injection unit. The process-critical variable is interfacial melt temperature: the TPE-S melt must contact the PP carrier while the substrate surface is still above its crystallization transition or at least in a softened state. Mold temperatures below 20 °C are generally unsuitable because skin solidification at the interface can reduce peel adhesion. Conversely, mold temperatures above 60 °C may extend cycle time and promote gate-stringing. Industry practice for similar SEBS overmolding grades uses steel temperatures of 30 °C to 50 °C, but the optimum must be established by instrumented mold trials.

The adhesion mechanism relies on diffusion and chain entanglement between the olefinic midblock of the SEBS and the semicrystalline polypropylene substrate. No amine-grafted adhesion promoter is normally required for PP, but mechanical interlock can dominate if the substrate is highly textured. Because of this, a flat smooth plaque test may underrepresent peel strength on a textured production part. Adhesion evaluation for two-component TPE/PP systems is commonly performed by peel testing in a tensile testing machine; however, no single ISO method is universally applied across all overmolded TPE geometries. Internal specifications therefore define peel angle, crosshead speed, and specimen width. Published adhesion values for the 1393 2K configuration are not available in open literature and must be generated on the intended substrate and mold texture.

Before molding, pellet surface moisture should be measured by Karl Fischer titration. Although saturated SEBS itself is not hygroscopic, condensation on cold pellets or high ambient humidity can introduce sufficient surface water to cause splay and interfacial defects. A desiccant dryer operating at 70 °C to 80 °C for 2 h to 3 h is typical for medium-hardness SEBS compounds. Residual moisture below 0.05 % by weight is the usual release criterion. General-purpose screws with an L/D ratio between 20:1 and 25:1 and a compression ratio of 2.5:1 to 3.5:1 are acceptable. At melt temperatures of 180 °C to 230 °C, the compound is shear-thinning; increasing injection speed can reduce viscosity more than would be expected for a simple Newtonian melt. But very high shear rates near the gate can generate local temperatures above the set barrel temperature. Therefore melt-temperature measurement with a hand-held pyrometer at the nozzle is necessary before setting the barrel profile.

Typical medium-flow SEBS compounds for two-shot molding show melt flow rates from 3 to 15 g/10 min when measured at 230 °C under 2.16 kg load according to ISO 1133-1:2022. The 1393 2K grade may fall outside this range because the second-component formulation can be adjusted for long flow paths. The lot-specific MFR should be used as the basis for gate sizing and fill-time simulation. Capillary rheometry at shear rates from 100 s⁻¹ to 1000 s⁻¹ demonstrates pronounced shear-thinning; mold-filling simulation requires Cross-WLF coefficients derived from lot-specific viscosity curves. On multicomponent injection molding lines with clamping force from 500 kN to 5000 kN, gate freeze-off and backflow through the non-return valve are observed as batch-to-batch processing bottlenecks. A shut-off nozzle on the second injection unit is recommended to prevent drooling during rotation of the moving mold half. The second-shot shot size should be controlled so that the cushion remains between 2 mm and 5 mm; insufficient cushion can cause inconsistent interface pressure and local delamination.

SEBS Block Copolymer Architecture, Fillers, and Hardness Reduction at 65 Shore A

The base chemistry contains polystyrene end-blocks and a saturated ethylene-butylene midblock. The polystyrene domains form a physically crosslinked network at service temperature but melt at processing temperature, giving the material its thermoplastic character. Hardness reduction to 65 Shore A is achieved by selective extension with paraffinic white oil; total extractables and oil type influence the long-term migration behavior. Compared with unsaturated SBS grades, the hydrogenated midblock of SEBS provides improved resistance to oxidative degradation, ozone attack, and ultraviolet aging, although carbon black or UV stabilizer packages are still required for long-term outdoor exposure. The 2K modification may include additional flow modifiers, adhesion promoters, or stabilizer combinations, but the specific additive package is disclosed only in the supplier’s technical documentation.

The values in the table represent the typical property envelope for medium-flow SEBS TPE-S compounds at 65 Shore A, not lot-specific release values for the 1393 2K configuration. Batch-specific tensile strength and elongation can vary with color concentrate, regrind ratio, and moisture level, so the certificate of analysis remains the controlling document.

Typical two-component applications include soft-touch overmolded grips for hand tools, appliance knobs, closure seals, and automotive interior attachments. In these applications the SEBS grade provides a lower density than rigid PVC or TPU, but selection for a specific part should not be based on density alone. Automotive interior odor and fogging performance must be verified according to VDA 270, VDA 278, or the relevant OEM specification; published data for this specific product is limited. For food-contact uses, processors should request a lot-specific declaration against 21 CFR 177.1810 or EU Regulation 10/2011 because compliance depends on the entire formulation and migration test data. RoHS recast 2011/65/EU and REACH EC 1907/2006 requirements are normally addressed by the supplier’s safety data sheet and product declaration.

When a SEBS 65A 2K Grade Is Compared With TPU or EPDM/PP TPV in the Same Application

If soft-touch aesthetics and PP overmolding are primary requirements, the SEBS grade is normally evaluated before TPU because of its lower density and lower sensitivity to moisture. Aromatic TPU at the same hardness can provide higher abrasion resistance and better oil resistance but has a density of 1.10 to 1.20 g/cm³ and is more prone to hydrolysis in wet heat aging. EPDM/PP TPV provides better compression set and high-temperature resistance but often has a different surface feel and a darker natural color. The table below summarizes these positional differences; the comparison is class-based and not a substitute for grade-specific testing.

For two-shot overmolding onto polypropylene, the SEBS midblock is chemically compatible with the semicrystalline PP phase, so unprimed adhesion is usually stronger than is typical for unfilled TPU. However, TPVs are also PP-based and can bond well to PP; the choice between SEBS and TPV often depends on the required compression set at elevated temperature. At 70 °C, SEBS compounds in the 65 Shore A range may show a measurable increase in compression set relative to TPVs, but the softer SEBS flow path and lower processing temperature can reduce in-mold stress in thin-walled overmolded sections. No universal ranking applies.

Operational boundaries for the BADAFLEX® SEBS-Comp. TPE-S 65A 1393 2K include avoidance of prolonged melt temperatures above 240 °C, restriction of regrind to 20 % by weight unless validated by lot testing, and exclusion of aromatic or highly polar oils that may attack the polystyrene end-blocks. The material should not be combined with amine-based stabilizers or copper-containing pigments unless explicitly approved by Bada AG because such combinations can shift the degradation onset and alter adhesion. Processing in a high-humidity environment above 60 % RH without drying increases the risk of splay at the interface. These boundaries are drawn from SEBS class behavior; the 2K modification may narrow or widen the window depending on the additive package.

Because published data for this specific configuration is limited, the batch certificate of analysis is the controlling technical document. Color masterbatch, regrind level, sealing time, and mold surface finish must be fixed before process capability studies are executed.