LCY Chemical Globalprene® SEBS 9551 is introduced as a linear styrene-ethylene/butylene-styrene triblock copolymer produced by anionic polymerization followed by selective hydrogenation of the polybutadiene midblock. The saturated midblock replaces the unsaturated butadiene segment of styrene-butadiene-styrene block copolymers with an ethylene/butylene random copolymer, removing main-chain olefinic sites that otherwise participate in ozone-induced chain scission and radical-initiated oxidative crosslinking. The grade is characterized by a nominal styrene content of 30 wt%, a specific gravity of 0.91 when tested under ASTM D792, and a Shore A hardness of approximately 65 when compression-molded film is measured under ASTM D2240. The high molecular weight is reflected in a 10 wt% solution viscosity in toluene of roughly 1500 mPa·s at 25°C, which places the product in the high-viscosity region of the Globalprene SEBS series. Because the material is supplied as free-flowing pellets with a bulk density near 0.60 g/cm³, hopper feeding in automated compounding lines is generally stable when storage conditions remain below 40°C and relative humidity below 60%.

The intended use envelope for Globalprene SEBS 9551 covers thermoplastic elastomer compounds, hot-melt adhesives, sealants, polymer modification, and bituminous binder modification. In each application, the polymer contributes elastic recovery, cohesive strength, and elevated softening characteristics. The grade is distinguished from lower-molecular-weight SEBS products by its higher melt viscosity and tensile stress capability, but these same properties require specific compounding strategies to avoid excessive shear heating.

What Property Set Distinguishes Globalprene SEBS 9551 from Unsaturated Block Copolymers?

The primary structural difference is the saturated ethylene/butylene midblock obtained by selective hydrogenation of the polybutadiene precursor. In SBS grades, the elastomeric segment retains high levels of main-chain unsaturation, which participates in radical-initiated crosslinking and oxidative cleavage. SEBS 9551 retains a residual unsaturation level low enough that oxidative failure shifts from rapid embrittlement to gradual thermo-oxidative softening. Consequently, compounded SEBS surfaces exposed to xenon-arc accelerated weathering under ISO 4892-2 typically show no surface cracking after 500 h, whereas unprotected SBS surfaces can develop micro-cracking and gloss loss at shorter intervals. In hot-air aging at 100°C, retention of tensile strength and elongation is governed by the antioxidant package rather than by main-chain unsaturation. The saturated backbone does not undergo the rapid embrittlement associated with butadiene auto-oxidation.

Compression set resistance of the hydrogenated midblock is also differentiated from unsaturated SBS and from partially crosslinked thermoplastic vulcanizates. When tested as a compression-molded plaque under ISO 815-1 at 70°C for 22 h, SEBS 9551 compounds can provide compression set values below 50% depending on oil loading and filler selection. However, the polymer is not a chemically crosslinked network. At continuous service temperatures above 120°C in air, the styrenic domains soften and creep becomes the dominant deformation mechanism. This boundary should not be exceeded without supplemental crosslinking or blending with a high-heat thermoplastic phase.

Twin-Screw Compounding Window and Melt Rheology

Melt processing of LCY Chemical Globalprene SEBS 9551 on a 25 mm co-rotating twin-screw extruder with an L/D ratio between 32:1 and 48:1 requires a barrel profile from 180°C in the feed zone to 220–230°C in the melting and mixing sections, with die temperature held at 200–210°C. Because the low-shear melt viscosity is high, screw configurations containing two or three kneading blocks in the plastification zone are recommended. If the melt temperature rises above 260°C, gel formation and extrudate surface roughness can occur. Torque-limited operation often dictates plasticizer addition. Naphthenic or paraffinic oils at 20–50 phr reduce drive torque by 25–45%, depending on screw rotation and oil aromatic content. Without plasticizer, the material can be processed in injection molding, but long flow paths and thin wall sections require clamp-end fill pressure above 90 MPa and melt temperature below 240°C.

The grade’s high molecular weight produces a pronounced shear-thinning response. In capillary rheometry conducted according to ASTM D3835 at 220°C, apparent viscosity decreases by more than one order of magnitude as apparent shear rate increases from 100 s⁻¹ to 1000 s⁻¹. This behavior supports filling of injection molds and uniform dispersion of fillers under high-shear conditions, but it also means that low-shear zones in the die or hot-runner system can retain stagnant polymer and generate degradation byproducts over extended runs. Frequent purging with a polypropylene-based purge compound is recommended when color changes or extended downtime are required.

Mineral-filled compounds containing calcium carbonate or talc can be produced with high filler loadings because the polymer’s high network strength prevents phase inversion. However, zero-shear viscosity imposes a practical limit on screw feeder accuracy when filler content exceeds 50 wt%. A compound containing 40 phr paraffinic oil and 20 phr polypropylene follows rule-of-mixtures behavior only below 20 wt% polypropylene; beyond that threshold, the morphology becomes co-continuous and flexural modulus measured by ISO 178 can increase non-linearly. Published data for this specific grade under ISO 178 are limited, so compound validation on production-scale equipment is required.

Adhesive and sealant formulations incorporating LCY Chemical Globalprene SEBS 9551 use hydrogenated hydrocarbon tackifier resins rather than rosin ester resins to maintain a single-phase melt. Addition of hydrogenated resin at 30–60 wt% lowers the softening point and increases substrate wet-out. In hot-melt bonding for automotive interior trim assembly, peel adhesion per ISO 11339 is a more reliable discriminator than loop tack because loop tack saturates with high-molecular-weight SEBS networks. In solvent-borne contact adhesives, a 10 wt% solution in cyclohexane/acetone mixtures can require application by roll coater rather than spray because of high solution viscosity. Silane-terminated sealants incorporate the SEBS as a non-reactive viscosity and sag-resistance modifier; sag is measured by ASTM D2202 or ISO 7390, with acceptable values frequently below 3 mm after 24 h for cartridge-grade sealants.

When Replacing SBS in Polymer-Modified Bitumen, Temperature Control Becomes Critical

SEBS 9551 can be dispersed into paving-grade bitumen using high-shear rotor-stator mixers at 170–180°C. Above 190°C, oxidative chain scission can occur if oxygen ingress is not controlled by nitrogen blanketing. Typical dosage is 3–6 wt% based on binder mass, with dispersion time of 30–60 min under high shear. The modified binder’s rutting resistance is evaluated by multiple stress creep and recovery testing according to ASTM D7405 or EN 16659. Non-recoverable creep compliance J_nr at 3.2 kPa typically remains below 0.5 kPa⁻¹ for heavy-traffic performance. Compared with SBS modification, SEBS 9551 raises the high-temperature performance grade without requiring sulfur vulcanization, but the absence of intractable chemical crosslinks can reduce high-temperature storage stability if the blend is stored for more than 48 h at 160°C without agitation. Under such conditions, phase separation can occur at the top of the tank, and re-homogenization requires re-shearing at 175°C.

For polymer modification of polyethylene or polypropylene, SEBS 9551 functions as an impact modifier and compatibilizer because the styrenic end-blocks associate with aromatic or semi-crystalline phases while the saturated midblock provides rubbery domains. When blended with polypropylene at 10–30 wt%, Izod impact resistance measured by ISO 180 can improve without sacrificing tensile modulus below 20 wt% loading. Beyond that threshold, modulus loss may be unacceptable for rigid packaging applications, and a higher-styrene SEBS or a different modifier should be evaluated.

Solvent Resistance, Swelling Metrics, and Regulatory Boundaries

The saturated midblock is generally resistant to polar solvents, dilute acids, and dilute bases. Aromatic-rich process oils, chlorinated solvents above 80°C, and strong oxidizing acids can swell the styrenic domains or increase extractable content. Swelling is measured by ASTM D471, with mass uptake typically rising above 50% after 72 h exposure to toluene at 23°C. In aliphatic hydrocarbon fluids below 60°C, swelling is substantially lower, but the polymer is not a barrier resin. Equipment designers should not specify SEBS 9551 as the sole sealing element against aromatic oils or fuel blends containing high aromatic content.

Compliance status should be verified against current supplier certifications. Typical SEBS grades of this composition are manufactured under ISO 9001 and ISO 14001 management systems. Heavy metal content can be certified below 10 mg/kg for each of lead, cadmium, mercury, and hexavalent chromium when tested by IEC 62321 procedures. Food-contact suitability is not automatically conferred by the base polymer. Specific compounds must be evaluated under FDA 21 CFR 177.1810 or the applicable regional migration standard before use in food-contact articles. Likewise, medical-grade suitability requires additional biological testing according to ISO 10993 on the finished component, not on the raw polymer alone.