SINOPEC Baling SEBS YH-507H is a hydrogenated styrenic block copolymer with a polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene molecular architecture. The grade is produced by sequential anionic polymerization of styrene and butadiene followed by selective hydrogenation of the polydienic midblock. The hydrogenation step saturates the midblock double bonds and reduces the rate of thermo-oxidative chain scission relative to unsaturated SBS grades. In the manufacturer’s nomenclature, the YH prefix designates the Baling SEBS product family, while the 507H suffix situates the material within the 507 series. Published English-language documentation for the exact suffix distinction is limited and should be verified against the current technical data sheet.

Specification Parameters and Standardized Test Methodology

Incoming inspection for YH-507H should be based on the manufacturer’s certificate of analysis. The parameters commonly controlled for SEBS of this architecture include melt mass-flow rate, Shore A hardness, tensile strength, elongation at break, density, bound styrene content, volatiles, ash, and compression set. The corresponding methods are ISO 1133-1:2022 or ASTM D1238-20 at 230 °C and 2.16 kg or 5.00 kg; ASTM D2240-15e1 for durometer hardness; ISO 37:2017 or ASTM D638-14 for tensile properties; ISO 2781:2018 or ISO 1183-1:2019 for density; and ISO 247-1:2022 for ash. Compression set is frequently evaluated after 24 h at 70 °C under 25% strain by ASTM D395-18. Exact numerical specification limits for YH-507H have not been reproduced in this document because they are lot-specific and subject to revision by the manufacturer.

Bound styrene content is a critical hidden variable because the polystyrene endblock weight fraction controls hardness, modulus, and upper service temperature. Batch-to-batch variation in bound styrene of 1 wt% can shift Shore A hardness by approximately 3 to 5 points in SEBS of this class. The certificate of analysis for YH-507H should therefore report bound styrene content by ISO 5478:2006 or ASTM D5775-95(2019). In hydrogenated SBCs, the diblock content, where relevant, is a separate parameter that influences tensile strength and melt processability. Grades intended for elastic recovery typically require low diblock content, while adhesive and tackified compounds may tolerate higher diblock content in exchange for lower viscosity.

On co-rotating twin-screw compounding lines, feeding behaviour is governed by pellet bulk density, screw configuration, and feed-throat temperature. A typical production-scale setup for SEBS of this hardness class is a 40 mm screw diameter extruder with L/D 44:1, run in starve-fed mode at screw speeds of 250 min⁻¹ to 350 min⁻¹. Barrel settings from 150 °C in the feed zone to 200 °C at the die are used to establish a melt seal before the first kneading block. If the melt seal is not formed, torque fluctuation and head pressure instability can occur. Head pressure variation exceeding 15% of the mean for more than 30 s on a 40 mm line indicates feed inconsistency, inadequate melting, or vent flooding.

Drying before processing is required for pellets that have been exposed to ambient air with relative humidity above 60%. A desiccant hopper dryer set to 80 °C for 2 h to 4 h with a dew point below -30 °C removes surface moisture and prevents steam-related surging at atmospheric vents. In closed-loop water-ring pelletizing systems, residual surface moisture can produce visible bubbles in extruded sheet or profile. The use of unprotected pellets in a humid environment without drying is an operational boundary that may shift melt quality and extrudate clarity.

What Distinguishes YH-507H from Non-Hydrogenated and Oil-Extended Alternatives?

Compared with unsaturated SBS grades, the hydrogenated midblock of YH-507H allows melt processing at temperatures that would generate gel bodies or viscosity drift in non-hydrogenated block copolymers. Unsaturated SBS grades are typically limited to barrel settings below 190 °C for extended residence times, whereas SEBS grades of this type are commonly run up to 230 °C without rapid thermal-oxidative degradation. This distinction is relevant in polypropylene compounding and in applications requiring repeated heat exposure during downstream welding or overmoulding. Compared with oil-extended SEBS grades, YH-507H is positioned as a formulation-building block rather than a pre-softened compound. The formulator can select paraffinic plasticizers, secondary resins, stabilizers, and fillers independently. Paraffinic mineral oil with aromatic carbon content below 1 wt% is preferred for compatibility with the ethylene-butylene midblock. Naphthenic oil may be used at reduced addition levels, while aromatic oil is not recommended because of migration and mechanical property loss.

Plasticizer loading and filler dispersion interact with the molecular architecture. Addition of 30 phr of paraffinic oil to an SEBS of this type reduces Shore A hardness and tensile strength while increasing melt flow; the exact shift is grade-specific. For compounds filled with calcium carbonate or talc, filler particle size above 10 µm may nucleate surface defects in thin-wall moulding. Published data for the specific YH-507H configuration is limited for filled systems, so pilot-scale compounding trials should precede commercial scale-up.

Rheological characterisation should be performed by capillary rheometry at 190 °C, 210 °C, and 230 °C across shear rates from 100 s⁻¹ to 5000 s⁻¹. These data establish gate geometry and injection speed limits. SEBS compounds of this architecture display strong pseudoplasticity, with apparent viscosity decreasing as shear rate increases. The activation energy for flow is not a constant because hard block relaxation changes with temperature. Grade-specific Arrhenius coefficients for YH-507H have not been published in the open literature. Without a shear rate sweep, injection speed settings above 300 mm s⁻¹ may create jetting in unfilled compounds or burn marks at hot runner tips.

Dynamic mechanical analysis of SEBS of this class typically reveals a poly(ethylene-co-butylene) glass transition below -40 °C and a polystyrene endblock softening region near 95 °C to 105 °C. The service temperature ceiling for a low-set compound is therefore constrained by the onset of endblock softening rather than by midblock degradation. For YH-507H, the specific tan δ peak positions should be obtained by ISO 6721-1:2019 or ASTM D4065-20, because differences in endblock molecular weight and bound styrene content shift the upper-use transition.

Application areas for YH-507H include impact modification of polypropylene, soft-touch overmoulding, polymer modification of engineering thermoplastics, and high-tensile sealants. In polypropylene impact modification, addition levels of 5 wt% to 20 wt% are typical for SEBS of this stiffness class, although the exact loading must be determined by low-temperature Charpy or notched Izod impact testing according to ISO 179-1:2010 or ASTM D256-10(2018). For sealant and adhesive applications, SEBS is combined with tackifying resins and paraffinic oil to obtain pressure-sensitive compositions. YH-507H may be selected when higher cohesive strength is required than with softer oil-extended grades.

When Downstream Moulders Require Fast Cycle Times

Thin-wall moulding of YH-507H compounds places demand on melt fluidity and part ejection. If the grade has a melt flow rate lower than 5 g/10 min under 230 °C and 5.00 kg, filling of wall sections below 1.5 mm may require elevated injection pressure and high holding pressure. If melt flow rate exceeds 15 g/10 min at the same conditions, the material may flash in tools designed for tighter-tolerance moulding. These thresholds are indicative, not grade-specific, and should be verified by capillary rheometry. Mould temperature between 30 °C and 50 °C supports rapid crystallization of polypropylene in overmoulded formulations; higher mould temperature improves weld-line strength but extends cycle time.

Overmoulding onto polypropylene substrates relies on melt interdiffusion at the interface. A bond strength above 1 MPa in peel or lap shear configurations is often required as a production floor target. To promote interfacial interdiffusion, the substrate surface should be free of mould release and the melt temperature should remain above 200 °C at the interface. In soft-touch applications, compounds with hardness from 40 Shore A to 70 Shore A are typical, while YH-507H may be selected as the high-hardness component in blends with softer SEBS grades to adjust feel and scratch resistance. A polished mould surface with roughness below 0.5 µm Ra reduces tack and improves demoulding without external release agents.

Compounding bottlenecks for SEBS of this molecular weight class typically occur when downstream pelletizing is attempted at melt temperatures below 180 °C, because melt elastic recovery can produce pellet tailing and agglomeration. Underwater pelletizer water temperature between 30 °C and 50 °C is used to skin the pellets rapidly and prevent agglomeration. If the melt is too cold, die-face freeze-off occurs, while too hot causes pellet fusion in the spin dryer. These observations from production-scale lines are not grade-specific but define practical margins for YH-507H compounding trials.

Stabilization of the hydrogenated midblock requires an antioxidant system that can withstand continuous service temperatures near 90 °C for general industrial applications. Volatile phenolic antioxidants may be lost during high-temperature drying or processing; a phosphite co-stabilizer is commonly added to protect melt processing. Free amine-catalyzed condensation systems may cause colour drift and should be tested for compatibility before being combined with YH-507H. Published interaction data for this specific grade with amine-based additives is limited, so laboratory compounding with differential scanning calorimetry and melt flow stability tests under nitrogen is advisable.

Regulatory files should be requested from the manufacturer for the specific production site. SEBS of this type may be evaluated under EU REACH Regulation EC No 1907/2006, RoHS Directive 2011/65/EU, and FDA 21 CFR 177.2600 when the finished article is intended for repeated food-contact use. Compliance cannot be inferred from the polymer family alone because residual unsaturation, ash content, and stabilizer packages vary by grade and production campaign. A certificate of composition and a change notification agreement with the supplier should be maintained for regulated applications.