Among hydrogenated styrenic block copolymers specified for melt-compounded elastomeric goods, LCY Chemical Globalprene® SEBS 9552 is introduced as a linear triblock copolymer with a saturated ethylene/butylene midblock and controlled styrenic endblock fraction. The product is produced by sequential anionic polymerization followed by selective hydrogenation; the hydrogenated midblock retains a low level of residual unsaturation, which improves resistance to ozone cracking, ultraviolet degradation, and thermo-oxidative chain scission relative to unhydrogenated styrene-butadiene-styrene block copolymers. The nominal bound styrene content is 30% by weight, with a diblock fraction below 1% by weight. This composition provides a physically crosslinked network at service temperature through phase-separated polystyrene domains, while retaining melt processability because the network is non-vulcanized and reversible. The grade is supplied in pellet form for injection molding, extrusion, melt compounding, and solvent-borne adhesive systems.

Representative producer-published values for the neat polymer are shown in Table 1. These values are not lot-specific specifications and should be verified against the certificate of analysis for the purchased production lot.

The combination of 30 wt% styrene, 75 Shore A hardness, and 5 g/10 min melt-flow rate places 9552 in the medium-styrene, medium-flow segment of the SEBS family. Differential scanning calorimetry under ASTM D3418 typically shows a polystyrene endblock glass transition near 95°C and an ethylene/butylene midblock transition below -40°C. The resulting mechanical profile is that of a flexible elastomer with recovery from extension, but the upper continuous service temperature is limited by endblock softening rather than by covalent network breakdown.

What Distinguishes the 9552 Architecture From Unsaturated SBS and Other SEBS Grades?

Unsaturated SBS grades contain pendant vinyl and cis/trans double bonds in the polybutadiene midblock. Those double bonds are the primary initiation sites for ozonolysis, photo-oxidation, and thermal embrittlement. In Globalprene SEBS 9552, selective midblock hydrogenation reduces residual unsaturation to a level that permits compounding without sulfur or peroxide vulcanization for many applications. Compared with high-molecular-weight SEBS grades, 9552 has a lower apparent melt viscosity and a higher melt-flow rate; this reduces injection fill pressure and permits shorter cooling times in thin sections. However, the lower molecular weight also reduces extensional viscosity and melt strength, so blow molding of large parisons or deep-draw thermoforming may require a higher-viscosity grade. The melt-flow rate of 5 g/10 min at 230°C and 5.0 kg piston load under ASTM D1238 is a specific differentiation parameter; formulators use this value to estimate machine capability and to compare incoming lots against a control.

On a co-rotating twin-screw extruder with an L/D ratio of 40:1 to 52:1, SEBS 9552 is typically processed with barrel set points of 190°C in the feed zone and 220°C to 230°C in the mixing and metering zones. The melt temperature is kept below 240°C to reduce the risk of gel formation and color shift. Pellets are pre-dried at 80°C for 2 h to a moisture content below 0.05% by weight; higher residual moisture produces surface defects in extruded profiles and viscosity instability in the melt. Screw speeds between 250 and 400 rpm are used in production, with specific mechanical energy input adjusted according to oil loading. For filled compounds, the addition of calcium carbonate, talc, or carbon black past the midpoint of the screw reduces torque and prevents dust-related feeding fluctuations. Die pressure is controlled by a gear pump and screen changer; screen packs with 100-mesh to 325-mesh filtration remove gel agglomerates larger than 44 µm. Water-bath pelletizing requires water temperatures from 30°C to 40°C and dry air knife pressure sufficient to prevent strand carry-over.

Compounding and Dispersion Variables in Polyolefin-Matrix Blends

Globalprene SEBS 9552 is applied as an impact modifier and soft-touch modifier in polypropylene and polyethylene matrices. The styrenic domains retain their reinforcing character when the compound is cooled below the polypropylene crystallization temperature, while the ethylene/butylene midblock contributes elastomeric compliance. In polypropylene-rich blends, the use of 10 wt% to 30 wt% SEBS 9552 can increase notched Izod impact strength measured under ASTM D256 and reduce brittle failure at low temperature; actual values depend on matrix molecular weight, nucleating additives, and cooling rate. A paraffinic or naphthenic process oil is used to lower hardness and increase flow. Aromatic oils should be limited to below 5 wt% of the total compound, because aromatic fractions can partition into the styrenic domains, plasticize the physical crosslinks, and reduce tensile strength and heat resistance. In a typical oil-extended formulation, the polymer is fed into the main throat of a twin-screw extruder, and oil is injected after the melting zone. If oil is added too early, the viscosity drops before adequate dispersion of the SEBS within the polyolefin matrix, creating soft spots and unstable pelletizing.

Thin-wall injection molding of SEBS 9552 compounds uses melt temperatures from 200°C to 230°C, mold temperatures from 20°C to 50°C, and injection pressures up to 80 MPa. The shear-thinning behavior of the saturated midblock lowers pressure drop through gates and runners relative to a comparable-hardness thermoset rubber. However, mold temperatures above 60°C can prolong gate freeze time and increase cycle time because the polymer remains elastomeric rather than crystallizing sharply. Vent depth should be limited to 0.01 mm to 0.02 mm to prevent flash, and sprues should use a draft angle of at least 3° to allow clean ejection. Because the material is not crosslinked, production scrap can be reground and blended with virgin pellets at levels up to 20 wt% without measurable loss of hardness; higher regrind ratios require verification of tensile properties per ASTM D412.

Wire and cable jacketing compounds based on SEBS 9552 are typically formulated with polyethylene or polypropylene and halogen-free flame retardants. The grade is selected over unsaturated SBS when heat-aging resistance is required in accelerated oven tests such as IEC 60811-401, where tensile strength and elongation retention are measured after aging at 100°C for 168 h. In production, magnesium hydroxide or aluminum trihydrate is dispersed at loadings of 50 wt% to 65 wt% on a twin-screw line with downstream filler feeding. The main processing constraint is the viscosity increase from high filler surface area rather than the base polymer. Melt temperature is maintained below 240°C to avoid discoloration of the compound and surface oxidation of the filler.

Solvent-borne adhesive formulations with SEBS 9552 are prepared at solids levels from 15 wt% to 30 wt% in toluene, cyclohexane, or methylcyclohexane. Brookfield viscosity by ASTM D2196 at 25°C is used to control coating weight and open time. Higher solids and higher molecular weight increase viscosity; a production batch with a viscosity 15% above target may require a solvent adjustment of 3 wt% to 5 wt% to return to slot-die coating parameters. Hot-melt pressure-sensitive adhesive formulations are compounded at 180°C to 200°C under nitrogen in a sigma-blade or planetary mixer, with melt viscosity measured under ASTM D3236. Coating is performed at 160°C to 180°C with slot-die or roller coaters at coat weights from 25 g/m² to 50 g/m². The styrenic endblock content controls cohesive strength and upper service temperature; tackifying resin selection is normally divided between an endblock-compatible resin for heat resistance and a midblock-compatible resin for tack and wet-out. If the endblock-compatible resin level exceeds the styrene content by more than approximately 10 wt%, the resulting film may become too stiff and lose peel adhesion.

Sealing and gasket compounds based on SEBS 9552 should be evaluated for compression set under ASTM D395 Method B at 70°C for 22 h. Because the system is not vulcanized, compression set is inherently higher than that of a crosslinked elastomer; the addition of polypropylene or a higher-styrene SEBS reduces set but increases hardness. In dynamic sealing applications, the upper continuous temperature is typically limited to below 90°C unless the seal is reinforced by a vulcanized or crosslinkable binder. The choice of 9552 in these formulations is driven by processability and the ability to regrind edge trim, but the long-term load recovery of a thermoset rubber is not replicated.

When 9552 Replaces a Higher-Molecular-Weight SEBS in Thin-Wall Injection Molding

Grade substitution requires comparison of melt-flow rate, tensile strength, elongation at break, and compression set. SEBS 9552 has a melt-flow rate of 5 g/10 min at 230°C with a 5.0 kg load; a high-viscosity SEBS grade may have a melt-flow rate below 1 g/10 min under the same conditions. The higher flow of 9552 can permit a reduction of melt temperature by 10°C to 20°C or a reduction of injection pressure by 15% to 30% in thin-wall tools, depending on wall thickness and flow length. The trade-off is a lower melt strength, which can cause sag in thick sections or inadequate parison stability in extrusion blow molding. Published data for direct numerical comparison of 9552 with all adjacent LCY grades is limited; formulators should request the current certificate of analysis and lot-specific melt-flow data. Comparative testing under ASTM D1238, ASTM D2240, ASTM D412, and ASTM D395 is recommended before substitution in approved formulations.

Food-contact, medical, and potable-water qualifications are formulation-dependent and cannot be inferred from the base polymer alone. The neat grade may be evaluated under FDA 21 CFR §177.1810 for styrene block copolymers in contact with food, and under USP Class VI or ISO 10993-5 for medical polymers, but any compounded formulation containing oils, fillers, tackifiers, or color concentrates requires independent migration and biological testing. No statement in this technical introduction should be read as a certification for a specific end-use. Additional conformance checks for heavy metals, phthalates, and residual solvents may be required under EU Regulation 10/2011, REACH, or RoHS depending on the final article.

Operational boundaries for melt processing are set by the balance between endblock softening and thermal degradation. Minimum melt temperature for homogeneous single-screw extrusion is approximately 180°C. Sustained exposure to melt temperatures above 240°C or residence times above 10 minutes in large dead spots can initiate gel formation and color shift. The grade is incompatible with high-aromatic process oils, strong oxidizing acids, and chlorinated solvents under high shear. Amine-based antioxidants at excessive concentration may accelerate color development in light-stable or transparent compounds. Because SEBS 9552 is a thermoplastic rubber with physical crosslinks, continuous load-bearing applications above 90°C are likely to show creep and compression set; for such conditions a vulcanized elastomer or a crosslinkable SEBS compound should be specified. The property values shown here are typical and should not be used as sales specifications.