Bada AG BADAFLEX® SEBS-Comp. TPE-S 45A 1956LD is introduced as a hydrogenated styrenic block copolymer compound with a nominal indentation hardness of 45 Shore A measured to DIN ISO 7619-1 or ASTM D2240-15. The TPE-S classification identifies a styrenic block copolymer structure; the SEBS designation denotes selective hydrogenation of the midblock from a styrene-butadiene-styrene precursor to a saturated ethylene-butylene sequence. This hydrogenation removes main-chain unsaturation and reduces the tendency to thermo-oxidative chain scission during repeated melting. The suffix 1956LD is manufacturer-specific and is not defined uniformly across Bada AG public technical literature; lot-specific colour, flow, and mechanical values must therefore be verified against the current certificate of analysis. The product is supplied as granules suitable for injection moulding and single- or twin-screw extrusion. In its nominal hardness class, the material is specified where low sealing force, soft-touch surface character, and elastomeric recovery are required. Class-typical property ranges for equivalent 45 Shore A SEBS compounds—not a substitute for the Bada AG certificate of analysis—include density from 0.98 g/cm³ to 1.05 g/cm³ to ISO 1183-1:2019, tensile strength from 4 MPa to 8 MPa to DIN 53504, elongation at break from 500% to 800% to DIN 53504, and 100% tensile modulus from 0.6 MPa to 1.2 MPa. The hydrogenated midblock differentiates the product from unsaturated SBS at equivalent hardness by lowering gel formation at processing temperatures between 180 °C and 240 °C and by preserving elongation after outdoor exposure.

In sealing applications, the low indentation hardness reduces compression force on mating surfaces. A static radial seal produced from this grade can be installed with a compression ratio from 10% to 25%; higher compression ratios accelerate compression set. The compound is not selected for continuous exposure to hot hydrocarbon media above 80 °C, because the SEBS midblock swells and loses tensile retention in non-polar fluids. Swelling tests to ISO 1817 in IRM 903 oil at 70 °C/72 h typically show mass change below 10% for this chemistry, but application-specific validation is required because oil absorption is compound-specific.

What Differentiates This Grade from SBS, TPE-U, TPV, and Plasticised PVC at the Same 45 Shore A Hardness?

At 45 Shore A, SEBS-type compounds occupy a defined performance envelope between unsaturated styrenic block copolymers, thermoplastic polyurethane, thermoplastic vulcanizates, and plasticised PVC. Unsaturated SBS compounds often show lower retention of elongation after re-melt and outdoor exposure because the butadiene segment contains double bonds; hydrogenation in the Bada AG grade removes that unsaturation and reduces oxidative crosslinking. In tensile testing to DIN 53504, class-typical SBS compounds at 45 Shore A may exhibit tensile strength from 3 MPa to 6 MPa, while equivalent SEBS compounds range from 4 MPa to 8 MPa; the overlap means hardness alone is insufficient for selection. When compared with TPE-U at the same Shore A value, the SEBS compound has lower density and lower abrasive wear resistance. TPE-U density typically falls from 1.15 g/cm³ to 1.25 g/cm³ to ISO 1183-1:2019, whereas the BADAFLEX® SEBS-Comp. remains in the 0.98 g/cm³ to 1.05 g/cm³ class-typical range. TPE-U also shows higher tear strength, often above 30 N/mm to ISO 34-1, while the SEBS class-typical value is below 25 N/mm. The SEBS compound provides lower moisture uptake and better resistance to hydrolytic degradation than polyester-based urethane grades. Against a TPV of equivalent hardness, compression set is typically higher for SEBS; TPV values are commonly 20–35% after 70 °C/24 h, while SEBS compounds of this class range from 30–45% to ISO 815-1. Against plasticised PVC, the SEBS grade avoids intentionally added phthalate plasticiser systems and offers lower density, but plasticised PVC can still show greater tensile strength and lower raw-material cost.

In a multicomponent injection moulding cell equipped with a 1,000 kN clamp force and a two-cavity hot-runner tool, BADAFLEX® SEBS-Comp. TPE-S 45A 1956LD is processed as the overmould on a polypropylene substrate. Gate sequencing must delay SEBS injection until the PP surface has reached 70–90 °C. If the SEBS melt temperature exceeds 220 °C, flash becomes difficult to eliminate because the low-hardness compound has low melt viscosity; vent depths are therefore maintained below 0.02 mm. A barrel profile of 160–190–200–210 °C from feed throat to nozzle, with a nozzle temperature of 210–220 °C and mould temperature from 20 °C to 40 °C, typically balances surface reproduction and cycle time. Back pressure is kept between 5 bar and 10 bar to avoid shear overheating, and cushion is held at 3 mm to 5 mm to prevent gas entrapment in the soft component.

Rheological and Thermal Processing Limits on Injection Moulding and Extrusion Lines

The melt viscosity of a 45 Shore A SEBS compound is shear-sensitive. Melt flow rate measurements to ISO 1133-1:2022 at 230 °C and 5 kg are typically between 5 g/10 min and 25 g/10 min for this hardness class. Higher-flow variants may reach 40 g/10 min, but the 1956LD suffix should not be used to infer a specific flow value. Drying is required when storage conditions exceed 60% relative humidity; a desiccant hopper dryer set to 70 °C for 2–4 h reduces surface moisture below 0.05%. The barrel residence time must not exceed 10 min at melt temperatures above 230 °C, and shutdown purging should use a polypropylene or polyethylene carrier, not general-purpose polystyrene, to avoid incompatible thermal degradation in the feed zone. The compound should not be blended with amine-based stabiliser masterbatches or amine-cured rubber residues, because polar amines can accelerate oxidative breakdown of process oil and create surface tack. Direct transition from polycarbonate at 280 °C is not recommended because residual carbonates degrade at the SEBS melt temperature and produce black specks; the barrel is purged at 180–200 °C before introducing the TPE-S.

For extrusion of flat profiles and extruded seals, a single-screw extruder with a three-zone screw and a compression ratio between 2.5:1 and 3.5:1 is used. The screw L/D ratio is typically 25:1 to 30:1. Because the compound is low in hardness, die swell is controlled by a temperature profile of 160–190 °C and a screen pack with 60–100 mesh; excessive screen pack pressure increases melt temperature and can produce surface roughness. In production, operators report that water-bath temperatures below 10 °C may cause micro-tearing in thin sections; a water bath temperature of 20–30 °C is preferred. Outdoor soft-touch parts require UV-stabilised variants. Unpigmented SEBS parts will still develop surface tack and chalking despite hydrogenation; accelerated weathering to ISO 4892-2 at 1,000 h can be used for comparative colour change, but final part geometry affects shading and edge erosion.

When Substituting BADAFLEX® TPE-S 45A 1956LD for Plasticised PVC in Medical Device Grips

Plasticised PVC replacement in medical and personal-care grips is driven by plasticiser migration and disposal constraints. The BADAFLEX® SEBS-Comp. grade contains no intentionally added phthalate plasticisers, which differentiates it from flexible PVC compounds that rely on 30–50 phr of DINP, DOTP, or DEHP for Shore A reduction. Instead, the SEBS compound is plasticised with paraffinic or naphthenic process oils within the SEBS midblock; oil migration potential across polycarbonate or ABS contact surfaces is lower than many phthalate systems, but extraction in polar media must be verified for the end use. Cytotoxicity and skin irritation may be evaluated to ISO 10993-5:2009 and ISO 10993-10:2010 for medical device housings. The relevant food-contact provision for styrene block copolymers is often 21 CFR 177.1810, but compliance depends on specific additives and release limits; the supplier’s statement must be matched to the final part and process.

Extrusion of soft-touch air-tight seals from BADAFLEX® SEBS-Comp. TPE-S 45A 1956LD is not carried out on a corotating twin-screw compounding line for finished-part production because the grade is already a compounded TPE-S. Fabricators instead use a single-screw profile line with a pin-and-die vacuum calibrator and a gauge tolerance of ±0.05 mm. The melt is conditioned in a static mixer after the screen pack to reduce memory effects. A cooling water temperature of 20–24 °C and haul-off speed set to produce 0.8–1.2 m/min for a wall thickness of 2.0 mm limit pore formation. Long-term compression set under continuous closure at 70 °C is the critical boundary for seal recovery; published data for this specific 1956LD configuration is limited, so physical validation to ISO 815-1 using the final seal cross-section is required before production release.