TSRC Taipol SEBS 7131 is a linear styrene-ethylene/butylene-styrene triblock copolymer produced by anionic polymerization followed by selective hydrogenation of the mid-block. The saturated ethylene/butylene segment confers oxidative stability and ultraviolet resistance that are not available in unsaturated styrenic block copolymers. The polystyrene end-blocks form physical crosslinks at ambient temperature and dissipate above the styrenic glass transition, allowing melt processing. The grade is supplied as dense pellets and is used in thermoplastic elastomer compounding, pressure-sensitive adhesives, sealants, polyolefin impact modification, and polymer modification. The nominal bound styrene content is 30% by mass, which places the product between low-styrene SEBS grades developed for very soft elastic articles and high-styrene SEBS grades used for rigid compounds. Pellets exposed to relative humidity above 60% RH should be dried below 0.1% moisture before melt processing; a desiccant dryer set at 75–85 °C for 2–4 h is normally sufficient. Failure to dry the pellets results in strand porosity, inconsistent melt viscosity, and reduced tensile values on finished parts.

What Raw-Polymer Specifications Frame the 7131 Design Envelope?

Indicative property data for the neat polymer are obtained from compression-molded specimens prepared at 180–190 °C and conditioned for 24 h at 23 ± 2 °C and 50 ± 5% RH. The following values are not specification limits; they represent the typical range reported by the manufacturer and should be verified against the lot certificate of analysis.

The moderate styrene content produces a balance of tensile strength, elastic recovery, and melt processability. Because the grade is unfunctionalized, it has low intrinsic adhesion to polar substrates; adhesion to metals, glass, or polar thermoplastics requires a primer, a tie layer, or blending with a maleic anhydride-grafted SEBS. The saturated mid-block permits continuous service in properly stabilized compounds at 80–90 °C in air, which is higher than the practical upper limit of many SBS-based compounds.

Injection Molding and Extrusion Equipment Settings

Melt processing is controlled by the polystyrene endblock content and the molecular weight distribution. A co-rotating twin-screw extruder with L/D 40:1 and vacuum venting at −0.08 MPa is suitable for oil extension, filler dispersion, and blending with polyolefins. Barrel set points typically range from 160 °C near the feed throat to 210 °C at the die. The melt temperature measured at the die should remain below 240 °C; sustained melt temperatures above 260 °C cause endblock degradation, gel formation, and loss of tensile properties. On production extrusion lines, die-head pressure rise is observed when residual moisture exceeds 0.1%, and the resulting pellets show surface roughness and reduced bulk density. For injection molding, barrel temperatures from 190 °C to 230 °C and mold temperatures from 20 °C to 50 °C are typical. A short screw cushion of 2–4 mm and back pressure between 5–10 bar reduce drooling and improve shot-weight consistency. Clamp force requirements depend on the part geometry, but machines with 800–1 200 kN clamping force are adequate for many technical components produced from compounds containing this grade.

When the product is extended with paraffinic white oil, oil absorption is slower than with low-viscosity SEBS grades. Oil addition is best performed in a twin-screw extruder using side injection or staged liquid feed after the polymer has reached a melt state. Specific energy input in a L/D 40:1 corotating extruder is generally in the range of 0.15–0.30 kWh/kg. If a single-screw extruder is used, a screw with 3:1 compression ratio and a Maddock mixing section is required for melt homogeneity.

When Solvent-Based Adhesives Demand High Cohesive Strength at Low Additive Loading

In solvent-borne adhesive formulations, SEBS 7131 is dissolved in toluene, cyclohexane, methylcyclohexane, or blends thereof at solids concentrations from 20 wt% to 40 wt%. High-shear dispersion at 300–1000 rpm in a jacketed stainless steel vessel prevents microgel formation and reduces dissolution time. The grade develops high solution viscosity because of its linear architecture and molecular weight; this limits the practical solids content in some coating lines. Addition of hydrogenated tackifier resins at tackifier-to-polymer ratios between 0.5:1 and 1.5:1 increases peel adhesion but reduces shear holding power when characterized by ASTM D3654-22 for shear and ASTM D903-20 for peel. Plasticization with naphthenic or paraffinic oil reduces solution viscosity and final hardness. Aromatic oil should be avoided because it solvates the polystyrene end-blocks and degrades cohesive strength. The product has no maleic anhydride functionality; adhesion to aluminum, glass, or treated polyester requires a silane primer, a chlorinated polyolefin primer, or a functionalized SEBS tie layer. Without such surface preparation, peel failure is predominantly adhesive at the substrate interface.

In sealant compounds, the polymer is typically compounded with paraffinic oil, calcium carbonate, and a hindered phenolic antioxidant. The saturated mid-block allows the compound to retain elongation under heat aging at 100 °C for 168 h when tested according to ISO 188:2023 and ISO 37:2017. The exact retention depends on antioxidant type and filler loading; published data for this specific formulation configuration is limited. Processing temperatures for sealant extrusion should not exceed 230 °C at the die, and vacuum venting is required to remove low-molecular-weight volatiles that otherwise create surface defects.

Compared with unsaturated SBS grades, the hydrogenated mid-block of SEBS 7131 raises the onset of oxidative degradation and permits higher continuous service temperatures. Compared with high-styrene SEBS grades, the 30% styrene fraction lowers hardness and tensile modulus while retaining adequate melt strength for profile extrusion. Compared with low-molecular-weight SEBS grades intended for high-flow injection molding, this grade exhibits higher cohesive strength and higher solution viscosity, making it less suitable for thin-wall parts with long flow paths. Compared with maleic anhydride-grafted SEBS, the unfunctionalized structure lacks polar adhesion but offers simpler compatibility with hydrocarbon tackifiers, polyolefins, and paraffinic oils. Storage should be in original sealed packaging at temperatures below 40 °C and away from direct sunlight; prolonged exposure to ultraviolet light can yellow the pellets and increase gel content.