SINOPEC Baling SEBS YH-602 is a linear hydrogenated styrene-butadiene-styrene block copolymer produced by Sinopec Baling Petrochemical. The polymer is manufactured through sequential anionic polymerization of styrene and butadiene, followed by selective hydrogenation of the polybutadiene midblock to a saturated ethylene/butylene structure. This structural saturation raises the onset of thermo-oxidative degradation relative to unhydrogenated SBS and reduces UV-induced chain scission. The grade is supplied as a porous pellet or crumb; bulk density is typically 0.30–0.50 g/cm³, with variation dependent on pellet geometry and conveying configuration. YH-602 is positioned for adhesive, sealant, plastic modification, wire-and-cable, and asphalt modification applications in which higher styrene content and elevated hardness are required.

What Are the Published Specification Limits for YH-602?

Table 1 consolidates the specification envelope published in Sinopec Baling product documentation. Values are representative production midpoints or boundary values; a current certificate of analysis should be used for release testing because production tolerance can shift the midpoint by small increments.

The 35 mass% styrene content differentiates YH-602 from lower-styrene SEBS grades in the same producer range. The higher polystyrene block fraction increases the glassy domain volume, which raises hardness measured by ASTM D2240-15 and reduces oil absorption at equivalent process oil loading. The melt mass-flow rate of 0.5–1.5 g/10 min under ISO 1133-1:2022 at 230 °C with 5 kg places the grade in the medium-viscosity region for SEBS. Published data for the molecular weight distribution of YH-602 is limited; therefore, rheological comparisons across batches should rely on melt mass-flow rate and solution viscosity rather than inferred molecular weight.

Processing Window Constraints in Twin-Screw Compounding

YH-602 should be pre-dried at 70–80 °C for 2–3 h when storage relative humidity has exceeded 60% or when surface moisture is confirmed above 0.1 mass%. In a co-rotating twin-screw extruder with an L/D ratio of 36:1 to 44:1, a barrel profile from 160 °C in the feed zone to 220 °C at the die is used for plastic modification. The melt temperature should not exceed 250 °C; sustained residence above this threshold promotes thermo-oxidative chain scission even though the ethylene/butylene midblock is saturated. When high-shear kneading blocks are used, local viscous heating can increase melt temperature by 10–30 °C, requiring lower barrel set points. A melt-temperature window of 220–230 °C at the die is often required for balanced filler dispersion and surface finish; deviations greater than ±5 °C can alter melt pressure and produce surface roughness on extruded profiles.

Process oil selection is critical. Liquid paraffinic or naphthenic oils with a viscosity-gravity constant below 0.85 and aniline point above 100 °C are preferred for oil extension. Aromatic oils are not recommended because they plasticize the polystyrene domains and reduce tensile strength measured by ASTM D638-14 Type IV. When oil loading exceeds 50 phr, tensile strength falls non-linearly; published data for this specific configuration is limited, and the inflection depends on filler type, oil aromaticity, and mixing history. Strong oxidizing agents and high levels of unsaturated plasticizers are also incompatible with the saturated midblock because they can initiate radical degradation during long residence at elevated temperature.

For filled compounds, filler addition should occur downstream after the polymer is fully fluxed. Premature feeding of high-surface-area silica at the feed throat can coat pellets, reduce wall friction, and create feed blockage. On a 40 mm co-rotating twin-screw extruder, a screw speed of 300–500 rpm with an output rate of 10–20 kg/h is a representative starting condition; specific mechanical energy for silica-filled SEBS compounds is typically 0.15–0.25 kWh/kg. Batch-to-batch variation in pellet bulk density can alter loss-in-weight feeder mass flow by ±5%; therefore, feeder calibration should be repeated when changing lot numbers. Injection molding of YH-602 compounds uses clamp pressure sufficient for 300–800 bar melt pressure and mold temperature of 20–50 °C. The polymer is not crosslinkable by sulfur vulcanization because the midblock is saturated; crosslinking, when required, is accomplished with peroxide-coagent systems or radiation dosing.

In hot-melt adhesive formulations, YH-602 is compounded with fully hydrogenated tackifying resins and saturated process oil. The use of YH-602 instead of lower-styrene SEBS is driven by the requirement for higher cohesive strength at elevated temperature. A starting formulation containing 25–35 phr YH-602 and a tackifier with a ring-and-ball softening point of 100–110 °C is processed in a heated sigma-blade mixer at 170–190 °C. Softening point of the finished adhesive is evaluated by ASTM E28-99; shear adhesion failure temperature is measured by ASTM D4498-07. Because published data for this specific formulation configuration is limited, these intervals should be confirmed experimentally rather than extrapolated from SBS-based hot-melt data.

During long hold times at 180 °C, SEBS-based adhesives typically show lower viscosity drift and lower color development than SBS analogs due to the absence of main-chain unsaturation. Viscosity stability is monitored by ASTM D3236-88 using a Brookfield Thermosel; the specific viscosity change for YH-602 is not published as a single value. For solvent-based adhesives, YH-602 dissolves in toluene, cyclohexane, and methyl ethyl ketone/toluene blends at 20–25 mass% solids. Solution viscosity at 25 °C in 25 mass% toluene is typically 2,000–4,000 mPa·s depending on molecular weight and solvent quality; however, published data for this specific configuration is limited.

When Lower-Styrene SEBS Grades Are Replaced by YH-602

YH-602 differs from lower-styrene grades such as YH-502 and YH-503 primarily in the mass fraction of polystyrene blocks. The higher aromatic block content of YH-602 raises tensile modulus and hardness, reduces creep under static load, and improves heat distortion resistance in unfilled compounds. The trade-off is a reduction in low-temperature flexibility and an increase in melt viscosity at equivalent processing temperature. Table 2 compares representative published values for three linear SEBS grades from the same producer.

When YH-602 replaces YH-503 in a compound, the required melt temperature is typically raised by 5–10 °C to compensate for the higher viscosity. The Shore A hardness can increase by 5–10 points, and elongation at break measured by ASTM D638-14 can decrease by 50–150 percentage points. These differences are not defects; they reflect an increase in the volume fraction of glassy domains. For soft-touch grips, gel-like compounds, or applications requiring high elongation at low hardness, YH-602 is therefore not a direct drop-in replacement for YH-502. Compared with SBS grades, YH-602 has a saturated ethylene/butylene midblock, which reduces UV-induced chain scission and permits higher service temperatures. After air aging at 100 °C for 168 h, SEBS grades generally show higher tensile strength retention than SBS analogs; however, the specific retention percentage for YH-602 has not been published in the consolidated datasheet.

For polypropylene modification, YH-602 is added at 10–20 mass% to improve low-temperature impact resistance. The compound is prepared in a twin-screw extruder at 190–220 °C, with polypropylene as the continuous phase and YH-602 dispersed as a discrete elastomer phase. Notched Izod impact strength is measured by ASTM D256-10; tensile properties are measured by ASTM D638-14. Published data for this specific configuration is limited, and the impact transition depends strongly on the base polypropylene melt flow rate and ethylene content. Higher styrene content in YH-602 increases compatibility with polystyrene and polar resins, but it can reduce the low-temperature impact increment relative to lower-styrene SEBS at equivalent loading.

Flame-retardant cable compounds based on YH-602 are formulated with magnesium hydroxide or aluminum trihydrate at total filler loadings of 60–70 mass%. The compound is processed in a twin-screw extruder with downstream side feeding to avoid viscosity spikes; cable jacket tensile properties are tested by ISO 37:2017, and heat deformation is tested by IEC 60811-507. YH-602 provides higher heat deformation resistance than lower-styrene SEBS because of the larger polystyrene domain volume. In asphalt modification, YH-602 is dispersed with a high-shear mill at 180–190 °C at addition levels of 2–4 wt%; penetration is measured by ASTM D5, and softening point by ASTM D36. Published data for this specific configuration is limited, so field-specific optimization is required.

RoHS and REACH Documentation Boundaries

Sinopec Baling SEBS YH-602 is supplied with documentation used for REACH compliance. The saturated hydrocarbon base polymer contains no intentionally added heavy metals. RoHS screening of electrical and electronic applications should be performed on the final compound rather than the neat polymer, because downstream fillers, colorants, and stabilizers dominate extractable metal concentrations. The base polymer is not a food-contact substance by itself; any use under food-contact regulations requires migration testing of the finished article according to jurisdiction-specific standards such as EU Regulation 10/2011 or FDA 21 CFR 177.2600 for rubber articles. The manufacturer has not published a generic food-contact approval for YH-602.