Bada AG BADAFLEX® SEBS-Comp. TPE-S 50A 1840 2K is a thermoplastic elastomer compound based on styrene-ethylene-butylene-styrene block copolymers. The product carries a nominal hardness of 50 Shore A when tested according to ISO 868 or ASTM D2240. The 1840 identifier is a manufacturer-specific formulation code within the BADAFLEX TPE-S range, and the 2K suffix denotes suitability for two-component injection molding onto selected rigid substrates. In the TPE-S class, elastomeric recovery is obtained through phase-separated styrene domains rather than the dynamic vulcanization used in TPV grades. The compound is supplied as free-flowing pellets and is processed on conventional thermoplastic injection molding equipment. Published grade-specific data for the exact 1840 2K configuration is limited; the screening values described below are based on the general property envelope for SEBS-based 50 Shore A two-component compounds and are not contractual acceptance limits.

Does the 2K Suffix Signify Reactive Adhesion or Physical Bonding?

The 2K designation in the 1840 2K product refers to two-component injection molding, not to a reactive two-component thermoset system. Bonding to the rigid substrate occurs by interdiffusion and wetting at the melt–substrate interface. In SEBS-based compounds, adhesion to semi-crystalline polyolefins such as polypropylene or high-density polyethylene is promoted by maintaining the substrate surface temperature above the onset of chain mobility and by controlling the melt contact temperature. Unlike non-2K TPE-S grades, the compound is intended for direct injection onto a freshly molded or preheated polyolefin substrate without an adhesion promoter or primer. However, adhesion strength depends on interface temperature, injection speed, holding pressure, mold venting, and the crystalline morphology of the substrate. No reactive cure is involved; the bond is thermoplastic and can be disrupted by reheating above the melting or softening point of the substrate.

Adhesion to polar substrates such as polycarbonate, acrylonitrile-butadiene-styrene, or polyamide is not assumed for a general SEBS 2K grade. The manufacturer should be consulted before specifying the 1840 2K compound for dissimilar thermoplastic substrates. For polypropylene substrates, interface temperature remains the primary process variable. Production experience with SEBS-based 2K grades indicates that interfacial peel strength drops sharply when the polypropylene surface temperature falls below 30 °C at the point of TPE injection. On rotary platen or indexing mold systems, this condition can occur on the second injection station if mold cooling is not balanced against substrate thermal history.

On production-scale two-component injection molding machines with rotating platen or indexing mold systems, the material is normally processed in the second injection unit. Pre-drying is required at 70–80 °C for 2–4 h if bags have been opened or if ambient relative humidity exceeds 60 %. Drying equipment should deliver a dew point of −20 °C or lower, and residual moisture should remain below 0.05 wt% to prevent surface splay at the interface. Barrel temperatures from rear to nozzle are commonly set at 160 °C, 180 °C, 195 °C, 205 °C, and 210 °C, with melt temperature controlled between 190 °C and 220 °C. Screw configuration should use a minimum L/D of 20:1 and a compression ratio of 2:1–3:1. Excessive shear heating should be avoided because SEBS mid-block scission at temperatures above 240 °C produces a permanent viscosity reduction and lower tensile strength. Apparent shear rate in runner systems is typically kept below 10⁴ s⁻¹ to limit shear-induced chain scission.

Mold temperature is usually set between 20 °C and 50 °C for the polypropylene side. For thin-wall overmolding below 1.5 mm flow length, injection speeds are kept low to medium to avoid jetting. Holding pressure should be applied until gate freeze; typical packing pressure is 20–40 MPa over the projected TPE area. Back pressure between 5 bar and 15 bar improves melt homogeneity without excessive oil migration. Venting depths of 0.01–0.03 mm at the last fill point are required because insufficient venting creates entrapped air at the interface and can reduce peel adhesion by more than 20 % when tested according to ISO 8510-2. Gate design should use edge or submarine gates with a land length of 0.3–1.0 mm; pinpoint gates can generate excessive shear and local temperature spikes.

Two-Component Molding Conditions and Substrate Preparation

For polypropylene or high-density polyethylene substrates, surface contamination must be controlled before the second component is injected. Mold release sprays are generally avoided because residual silicone-based release agents create a barrier layer that inhibits wetting. If mold release is unavoidable, a non-silicone release agent validated for adhesion-neutral behavior should be used. Pre-molded inserts should be reheated to 80–120 °C by infrared or hot air before overmolding unless the two-component mold maintains the substrate above the required surface temperature. Co-molding in a single cycle with controlled substrate cooling is preferred because it avoids contamination and moisture uptake during intermediate storage.

The property envelope for SEBS-based 50 Shore A two-component compounds is shown below. The table is intended for initial material screening and does not replace the Bada AG certificate of analysis for lot-specific acceptance. Mechanical properties are strongly influenced by oil content, styrene block ratio, mold temperature, and specimen preparation. Hardness should be checked after conditioning at 23 °C and 50 % relative humidity for at least 24 h; immediate hardness readings after demolding can differ by several points.

The compound can be reprocessed if regrind is controlled. Production experience indicates that regrind ratios above 20 % can shift hardness and lower interfacial peel strength; lot blending should therefore be validated before production release. If the material is colored with masterbatch, a polyolefin carrier system at 2–3 wt% is typical, and pigment loading should be minimized because high filler content alters the 50 Shore A hardness plateau. Avoid combination with high aromatic process oils because they can plasticize the SEBS mid-block and reduce tensile strength. Strong oxidizing acids, ketones, and aromatic hydrocarbons can extract processing oil or stress-crack the compound; continuous immersion applications require specific validation of retention and tensile properties.

When SEBS-Based 50 Shore A Compounds Replace TPU or TPV in 2K Sealing Applications

Material substitution studies on two-component sealing and soft-touch applications typically compare SEBS 50A grades with polyurethane and dynamically vulcanized polyolefin elastomers. SEBS compounds have lower moisture uptake than TPU; this reduces drying intensity and hydrolytic degradation risk in humid production environments. The density of SEBS compounds is commonly lower than that of TPU grades at equivalent hardness, which can reduce part weight. Abrasion resistance measured according to DIN ISO 4649 is generally poorer for TPE-S than for TPU; therefore the material is not appropriate where sliding wear dominates. Compared with TPV, the SEBS 2K grade may offer a softer tactile response and better colorability but lower continuous service temperature. TPV types often retain compression-set resistance above 100 °C, while SEBS grades require compression-set validation above 70 °C according to ISO 815-1.

Typical use cases for the 1840 2K grade include overmolded handles, tool grips, gaskets, closures, and soft-touch elements on polypropylene or high-density polyethylene carriers. These applications require confirmed substrate adhesion and dimensional stability under end-use thermal load. For potable water or food contact, the specific compound must be evaluated against Regulation (EU) No 10/2011 or FDA 21 CFR 177.2600 for the exact additive package; no food-contact status is conferred solely by SEBS classification. For automotive interior applications, volatile organic compound and fogging behavior should be tested according to VDA 278 and DIN 75201; published data for this specific 1840 2K configuration is limited. Where high cosmetic surface quality and polypropylene substrate adhesion are specified, incoming PP resin should also be controlled for nucleating additives, because nucleation density changes the crystallization front and can alter peel strength; this interaction is typically evaluated by a 90° peel test on co-molded plaques before production release.