SINOPEC Baling SEBS YH-504 is a linear styrene-ethylene/butylene-styrene triblock copolymer supplied by Sinopec Baling Petrochemical Co., Ltd. The grade is a non-oil-extended hydrogenated styrenic block copolymer in which terminal polystyrene blocks phase-separate from a saturated ethylene/butylene midblock. The polystyrene domains form physical crosslinks below the styrene glass transition temperature, while the saturated midblock provides elongation, low-temperature flexibility, and resistance to oxidative chain scission. YH-504 is used in adhesive, asphalt, polymer modification, and specialty compounding operations where a lower melt viscosity than standard linear SEBS grades is required. The material is typically supplied as white pellets; exact bulk density, pellet size, and volatiles vary with production lot and should be checked against the certificate of analysis.

Property Boundaries and Certification Requirements

Specifications for YH-504 are defined by the manufacturer’s certificate of analysis and should be confirmed for each lot. The values in the following table are representative of the grade and normalized to recognized methods where possible; they are not intended as release limits unless the purchaser and supplier agree in writing. Melt flow rate values reported at 230 °C and 5 kg are not interchangeable with 190 °C/2.16 kg polyolefin-condition values.

For incoming quality control, a single capillary rheometer fitted with a 1.0 mm die is used to detect lot-to-lot variation in apparent shear viscosity at 200 °C and 100 s⁻¹. Batch-to-batch variance in MFR is typically controlled within ±0.5 g/10 min according to manufacturer certificates; compounders compensate through feed rate adjustment rather than barrel temperature changes because the latter can destabilize the styrenic domain network.

The following matrix lists methods commonly used to evaluate YH-504 compounds across application classes. Compliance must be demonstrated on the finished article and is not automatically conferred by the neat resin.

On a co-rotating twin-screw extruder with L/D ratio of 40:1 to 52:1, YH-504 is introduced at the main feed throat with the base polymer or filler. Barrel set temperatures of 170–220 °C are typical; the melt temperature at the die should not exceed 230 °C for prolonged residence times because the polystyrene end-blocks begin to lose network integrity and the melt may undergo chain scission. Pre-drying at 70 °C for 2–4 h in a desiccant dryer is required when ambient relative humidity exceeds 60% RH, and for compounds containing magnesium hydroxide or aluminum trihydrate the filler moisture should be below 0.2 wt% to prevent vent flooding. Die pressure is maintained below 15 MPa; above this limit, sharkskin melt fracture is observed on strand pelletizers with 2.0 mm die holes. A high-shear kneading block located immediately after the melting zone can produce a 8–15 °C adiabatic temperature rise; therefore, temperature probes upstream and downstream of the kneading section are used to verify actual melt temperature rather than barrel set point alone.

What Distinguishes YH-504 from YH-503 and Oil-Extended SEBS Grades?

YH-504 is positioned as a lower-solution-viscosity linear SEBS relative to YH-503. The difference is most visible in melt pressure during compounding: on a 25 mm counter-rotating twin-screw extruder at 200 °C, YH-504 can reduce die pressure by roughly 20–30% compared with YH-503 at the same screw speed. YH-503 is selected when higher melt strength and higher tensile properties after repeated processing are required; YH-504 is selected for improved wet-out of fillers, reduced cycle time, and lower processing torque. Oil-extended SEBS grades do not provide the same formulation freedom because the extender oil is fixed at 30–50 phr, and the oil migrates to surfaces under heat aging. In contrast, YH-504 allows the compounder to select a naphthenic, paraffinic, or ester plasticizer at the level needed for the application. This independence is critical for compliance with 21 CFR 177.2600 and USP <88> where extractable oil fractions must be controlled. Compared with styrene-ethylene/propylene-styrene grades, YH-504 displays greater polyethylene-phase compatibility, whereas SEPS grades often show stronger interaction with polypropylene continuous phases; selection is therefore determined by the continuous phase of the target compound.

When YH-504 is added to polypropylene at 5–10 wt%, notched Izod impact strength at −20 °C typically increases from 4 kJ/m² to 9–12 kJ/m² in unfilled formulations, measured by ISO 180:2023. The improvement depends on the matrix melt flow rate, coupling agent type, and screw design. Flexural modulus retention is usually 80–90% of the unmodified compound. The SEBS phase encapsulates glass fiber in reinforced compounds and reduces stress concentration; addition levels above 12 wt% are avoided because the compound becomes difficult to pelletize and may require a second downstream cooling step. On injection molding machines with clamp force between 1,200 kN and 2,500 kN, YH-504 compounds are processed at melt temperatures of 180–200 °C and mold temperatures of 30–50 °C. The rear barrel zone is set 20 °C below the front zone to avoid bridging at the feed throat. Gate diameter should be at least 1.0 mm; gates smaller than 0.8 mm produce high shear heating and surface flow marks. Mold release agents based on silicone are avoided because they interfere with subsequent bonding or adhesion; if release is required, a fluoropolymer release agent is applied sparingly.

When YH-504 Replaces Unhydrogenated SBS in Outdoor Sealing Profiles

When YH-504 replaces an unhydrogenated SBS in outdoor sealing profiles, the processing window narrows because the saturated midblock has higher melt viscosity at equivalent shear. On a 65 mm single-screw extruder, screw speed is limited to 60–80 rpm to keep melt temperature below 230 °C. The benefit appears in weathering: after 1,000 h xenon-arc exposure according to ISO 4892-2:2013 method A, a YH-504-based seal retains 85–95% of initial tensile strength, while an SBS control typically falls below 50%. Compression set after 22 h at 70 °C is typically 35–45% for YH-504 compounds compared with 50–60% for SBS compounds, measured by ISO 815-1:2019. The nonpolar surface of YH-504 requires corona treatment to 40–45 mN/m for acceptable paint adhesion; untreated parts show adhesion failure at the primer interface. Aromatic process oils are restricted to 20 phr or less in sealing formulations requiring tensile strength above 8 MPa, because higher aromatic oil contents solvate the polystyrene domains and reduce cohesive strength.

For hot-melt pressure-sensitive adhesive compounding, YH-504 is combined with a C5/C9 tackifying resin and a naphthenic oil in a low-shear axial-flow mixer at 80–120 rpm. Homogeneous adhesive mixtures can be reached in 45–60 min at 160 °C; above 180 °C the adhesive may emit volatile oligomers and requires localized exhaust. Loop tack values of 2.5–4.0 N/cm² are typically recorded by ASTM D6195-03 when the resin-to-polymer ratio is between 1.5:1 and 2.5:1. Coat weight is maintained at 20–30 g/m² on a standard slot-die coating head; lower coat weights produce edge curl and lower peel. The saturated EB midblock allows the adhesive to retain pressure-sensitive properties after 500 h of heat aging at 70 °C per ASTM D4498-07, whereas an SBS-based control loses tack due to oxidative crosslinking of the midblock. The lower solution viscosity of YH-504 reduces gear pump wear in continuous coating lines; pump inlet pressure is typically 0.5–1.0 MPa lower than with standard linear SEBS grades.

Compounding Halogen-Free Flame-Retardant Cable Sheathing

Compounding YH-504 with magnesium hydroxide or aluminum trihydrate at loadings of 60–65 wt% is performed on a co-rotating twin-screw extruder with atmospheric and vacuum venting. The mineral filler is side-fed after the polymer melting zone to limit the temperature increase caused by filler friction. Filler surface treatment with stearic acid or a silane coupling agent is necessary; untreated magnesium hydroxide increases compound viscosity to the point where the extruder torque limit is reached before uniform dispersion occurs. The limiting oxygen index of a 60 wt% magnesium hydroxide compound can reach 36–40% under ISO 4589-2:2017, but elongation at break falls below 150% when the filler exceeds 65 wt%. Volume resistivity after conditioning at 23 °C and 50% RH is in the range of 10¹⁰–10¹² Ω·cm when measured by IEC 62631-3-1:2016. Published data for YH-504 in this specific compound configuration is limited; production trials are usually required to establish the exact tensile, fire, and electrical balance.

In asphalt binder modification, YH-504 is added at 3–6 wt% and dispersed under high shear at 170–180 °C. Dynamic shear rheometer testing according to AASHTO T315 is used to measure the complex shear modulus G*/sin δ before and after rolling thin film oven aging. A typical specification target is G*/sin δ ≥ 1.0 kPa at 64 °C for the unaged binder and ≥2.2 kPa after RTFO aging. The lower solution viscosity of YH-504 compared with YH-503 allows dispersion in 45–60 min at 600 rpm in a laboratory high-shear mixer; however, published data for field-scale asphalt terminal blending of this specific grade is limited. Storage stability tests at 163 °C for 48 h according to EN 13399:2017 should be performed to measure phase separation because the density difference between SEBS and asphalt can cause top-bottom softening point differences above 2.5 °C if the binder is not chemically compatible. Addition rates above 6 wt% may increase the mixing viscosity beyond spray-applied paving specifications and require a polymer-in-oil predispersion step.