Bada AG BADAFLEX® SEBS-Comp. TPE-S 60A 1087 2K is a hydrogenated styrenic block copolymer compound based on SEBS, with a nominal hardness of 60 Shore A and a manufacturer suffix signalling two-component injection moulding. The three-digit field 1087 is an internal Bada AG identifier and does not map directly to a mechanical property. Grade-specific values for melt flow rate, density, tensile strength, elongation at break, tear strength, compression set, and substrate adhesion must be obtained from the current Bada AG technical datasheet or lot certificate. The following technical description distinguishes between class-typical SEBS TPE-S behaviour and product-specific requirements.

SEBS is produced by hydrogenation of the midblock in styrene-butadiene-styrene block copolymer. The resulting ethylene/butylene segment has lower residual unsaturation, which improves thermo-oxidative stability during melt processing and reduces yellowing compared with unhydrogenated SBC grades. The polystyrene end-blocks form a physical crosslink network below the styrene glass transition; above that transition the endblock domains soften and the compound flows. This mechanism differs from TPV compounds, where dynamic vulcanization of an EPDM phase creates permanent crosslinks, and from TPU, where hydrogen-bonded hard segments provide thermal and solvent resistance. Consequently, an SEBS TPE-S at 60 Shore A typically has lower density and lower pre-drying demand than TPU, but also lower resistance to aromatic and chlorinated solvents and lower abrasion resistance; it is generally selected where polyolefin compatibility and soft-touch haptics dominate the application.

Hardness is measured according to ASTM D2240-15 or ISO 48-4; values are influenced by specimen thickness, temperature, and reading time. A 60 Shore A SEBS compound does not have a fixed tensile modulus. Depending on oil extension, filler type, and endblock content, class-typical tensile strengths are often in the single-digit megapascal range and elongation at break can exceed 400%, but published data for this exact Bada AG configuration is limited. Those ranges must not be used as a product specification.

What crystallisation and compatibility mechanisms govern 2K adhesion to polyolefins?

In two-component injection moulding, the SEBS midblock is chemically compatible with polypropylene and polyethylene, but adhesion does not occur simply from melt contact. The first-shot substrate must be heated by the second melt to a surface temperature that permits chain movement, and the TPE-S melt must remain fluid long enough for interdiffusion. On a two-component injection machine with a rotating platen or core-back tool, the substrate is transferred after cooling to a residual mould temperature; the second barrel is typically set between 180 °C and 220 °C. If the substrate surface does not reach at least 120 °C, adhesive failure tends to occur at the interface. If the substrate is contaminated with mould release agent, oil, or condensed volatiles, a correct thermal history cannot by itself ensure adhesion.

Polar substrates such as PC, PA, or PBT usually require a functionalised SEBS or an additional tie layer, because non-functional SEBS midblock cannot reliably wet the polar surface. The 2K identification in this Bada AG grade indicates a formulation intended for two-component processing, but does not by itself define the substrate list. Bada AG may provide a substrate adhesion matrix for the specific 1087 grade; without that matrix, general class behaviour cannot be used to qualify a commercial part.

Adhesion strength is evaluated by peel testing. ISO 8510-2 or ASTM D903 can be applied to flexible-to-rigid assemblies; failure mode is recorded as cohesive or adhesive. A cohesive tear in the TPE-S layer demonstrates that interfacial strength exceeds the bulk strength of the compound, while a clean adhesive separation indicates insufficient interdiffusion, contamination, or a crystallised skin on the substrate surface.

For polypropylene inserts or first shots, corona or plasma surface activation is sometimes used as a risk-reduction step. Corona discharge must be applied within a defined time window and at controlled power, because excessive treatment can oxidise the surface and create low-molecular-weight fragments that act as a weak boundary layer. Plasma treatment of the polar substrate is not a substitute for correct pre-drying of the TPE-S material.

The compound is processed in conventional three-zone screw injection machines. A general-purpose screw with a check ring is acceptable; a high-dispersion screw improves colour uniformity but can add shear heating. The shot weight is controlled by melt cushion of 2 mm to 5 mm; inconsistent cushion is a common source of batch-to-batch part weight variation on production lines.

Rheological Boundaries in SEBS–Silica Compounding

SEBS in neat form has high melt viscosity; compounders extend it with paraffinic or naphthenic oil and add mineral filler. The oil is absorbed into the ethylene/butylene phase while the polystyrene endblock domains remain intact. In production-scale twin-screw extruders with L/D from 40:1 to 52:1, SEBS is fed at the main throat, oil is injected after the polymer is molten, and silica or calcium carbonate is added through a side feeder. Temperature profiles are often set between 170 °C and 210 °C, with vacuum devolatilisation before the die. If free oil is present on the pellet surface or if filler dispersion is incomplete, injection moulding produces surface streaking and variable hardness; these are compounding failures rather than moulding defects.

Melt flow index is determined under ISO 1133-1:2022 or ASTM D1238-23. For SEBS TPE-S grades, common test conditions are 190 °C/2.16 kg or 230 °C/2.16 kg; the Bada AG datasheet is required to identify the correct condition for this grade. Melt flow index is used for lot acceptance and not as a direct measure of two-component mould fill behaviour.

Thermal degradation in SEBS TPE-S is usually observed as viscosity reduction, yellowing, and gel formation. The ethylene/butylene midblock is susceptible to chain scission at excessive hold times; the maximum safe residence at 200 °C should be determined for the individual grade. In moulding practice, this limits hot-runner volume and start-up hold time. Melt temperature overshoot due to shear heating is detected by comparing barrel set-point with a melt thermocouple in the machine nozzle; differences greater than 10 °C indicate excessive screw rotation or back pressure.

Moisture on pellet surfaces is a separate process risk. Although SEBS absorbs very little moisture, condensation on cold pellets can occur in high-humidity handling. Drying at 60 °C to 80 °C for 2 h to 4 h in a desiccant dryer reduces the risk of splay and surface defects. When moulding heavy soft-touch components, drying alone does not compensate for melt-temperature inhomogeneity from an undersized screw or excessively high screw speed.

When Hot-Runner Tooling Requires Controlled Melt Residence

In a two-component mould with a hot-runner manifold, the TPE-S shot resides in the heated channel during the injection and cooling cycle. If the hot-runner volume is larger than the shot size or if the cycle is interrupted, the compound experiences additional thermal history. Severity increases with temperature; a temperature overshoot of 10 °C above setpoint can reduce melt viscosity and shift peel performance. Use of sequential valve-gate control, low-manifold-volume channels, and rapid pressure release reduces dead zones. If black specks or colour drift appear, purging with an SEBS-specific purging compound is required; purging agents that are chemically incompatible with styrenic block copolymers may leave residues that further degrade the next shot.

Because SEBS TPE-S viscosity is shear-rate dependent, mould fill is not predicted by a single viscosity number. Capillary rheometry or injection-pressure transfer studies are used to establish the relationship between injection velocity, cavity pressure, and gate freeze. In practical two-shot applications, gate freeze must occur after the substrate surface has been wetted and before the second component in the cavity has solidified; premature gate freeze causes short shots and weak adhesion at the end of flow.

Within the BADAFLEX family, a TPE-S 40A grade will be softer and may exhibit higher oil loading, while an 80A grade will be harder and may show better compression set and higher tensile strength. A TPE-E or TPE-U of the same nominal hardness may have better tensile and heat resistance but different adhesion, moisture sensitivity, and mould release behaviour. The 1087 2K grade should not be assumed interchangeable with BADAFLEX TPE-S grades that lack the 2K suffix.

Because the softness of SEBS TPE-S is partly achieved by oil extension, long-term contact with amorphous or low-crystallinity substrates can lead to migration of the extender into the substrate at elevated service temperature. This changes hardness, surface tack, and compression set. Compression set measured under ISO 815-1 at 70 °C/24 h is a common screening test for sealing applications. Lower compression set is achieved by endblock selection and process history; higher mould temperature can improve phase separation but may prolong cycle time and increase post-mould shrinkage.

Regulatory Compliance and Extractables Documentation

Compliance depends on the complete compound recipe, including oil, filler, stabilisers, and colourants. The grade designation alone does not confer food-contact, medical, or automotive compliance. When a part requires regulatory approval, the converter must obtain the Bada AG product-specific declaration or raw material disclosure. The table below lists standards and test methods frequently referenced for SEBS TPE-S compounds; it is not a compliance certificate.

In application use, this compound class is generally suited for soft-touch overmoulding on polypropylene and polyethylene, and for seals and gaskets where hardness of 60 Shore A is acceptable. It should not be used as a direct substitute for TPV in continuous high-temperature oil exposure, or for TPU in abrasive or high-solvent environments, without component-level validation. Performance should be confirmed using the target geometry and full processing conditions; laboratory plaques may not reproduce the same cooling rate, orientation, or substrate temperature history. Production validation must include short shots, worst-case melt temperature, lowest substrate temperature, and maximum mould release contamination. Storage in sealed, dry containers at ambient temperature is recommended. If condensation occurs, drying at 60 °C to 80 °C may be required. Avoid use with strong oxidising acids and high-polarity solvents unless data for the specific grade confirms compatibility; oil extenders can be extracted by non-polar solvents, changing hardness and dimension. The product should not be mixed with other TPE-S grades without compatibility verification because oil migration can alter adhesion and surface tack over time.