SINOPEC Baling SEBS YH-533 is a linear hydrogenated styrene-butadiene-styrene block copolymer supplied as white porous pellets. The butadiene midblock is produced by anionic polymerization and then subjected to selective hydrogenation, converting the main-chain unsaturation into an ethylene-butylene rubber sequence. This saturated midblock distinguishes YH-533 from unhydrogenated SBS grades in the same manufacturer portfolio by raising thermal-oxidative stability and reducing gel formation during high-temperature compounding. Incoming raw-material evaluation typically compares the lot certificate against the following values: bound styrene 30–33 wt%, volatile matter ≤1.0%, ash ≤0.2%, Shore A hardness 65–70, tensile strength ≥15 MPa under ISO 37:2017, elongation at break ≥500%, and melt flow rate 0.5–2.0 g/10 min at 230 °C/5 kg under ISO 1133-1:2022. Because the grade is not oil-extended, the formulator controls plasticizer content instead of inheriting a fixed oil loading from the manufacturer.

Typical application fields include polypropylene impact modification, compounded thermoplastic elastomers, asphalt modification, sealants, adhesives, and cable jacketing. In polyolefin modification, YH-533 functions as a discrete rubber phase dispersed in the polypropylene matrix. The saturation of the butadiene block limits odour and gelling during multiple regrind passes, a practical distinction from unhydrogenated SBS. Relative to oil-extended SEBS grades, the neat form offers wider compounding latitude but requires auxiliary oil dosing equipment if target Shore A hardness falls below 50.

What reported values define YH-533 in incoming raw-material inspection?

Raw-material laboratories typically record melt flow rate, moisture, and hardness before release to compounding. Test specimens are compression molded at 180 °C for 5 min under 10 MPa and cooled under pressure at 15 °C/min. Hardness is read 15 s after the presser foot contacts the sheet. Melt-flow testing is performed on pellets dried to 0.05% moisture; undried pellets produce falsely high MFR because residual water acts as a processing aid. The full certification data span the values in the following table. The ranges are drawn from manufacturer technical literature and should be verified against the current batch certificate.

Lot-to-lot variation in MFR of ±0.3 g/10 min is common across bulk deliveries. Automatic gravimetric dosing systems should be adjusted when the MFR shifts below 0.5 g/10 min because hopper bridging becomes more frequent. Bulk unloading should not use heated pneumatic lines above 50 °C; surface fusion of pellets at silo walls has been reported when discharge air exceeds 60 °C.

Processing boundaries on 40:1 L/D compounding lines

On a co-rotating twin-screw extruder with 40:1 L/D ratio and 35 mm screw diameter, YH-533 is introduced at the main feed throat. A barrel profile of 180/190/200/210/200/190 °C from feed throat to die keeps the melt below the thermal degradation threshold. Two kneading blocks in the plastication zone followed by one distributive mixing section are sufficient for dispersion; additional kneading elements raise melt temperature without improving property homogeneity. Melt residence time above 230 °C should not exceed 20 min; beyond that limit, torque and die pressure decrease irreversibly, indicating chain scission rather than external lubrication.

Moisture uptake above 0.1% creates surface roughness and microvoids in extruded strands, so the pellets are dried at 70–80 °C for 2–4 h when ambient relative humidity exceeds 60%. Strand pelletizing runs best with die water at 30–40 °C and an air-knife dewatering system. Strand breakage occurs when die swell exceeds 1.5 mm beyond the die hole, typically from low melt temperature or residual moisture.

Paraffinic white oils with aromatic content below 5% can be absorbed at loadings of 20–100 phr to produce soft compounds. Oil injection should be split between the second and fifth barrel zones to prevent screw slip and phase inversion. Dumping oil into the feed throat creates melt-temperature fluctuation of ±10 °C and poor dispersion. High aromatic contents are incompatible with the ethylene-butylene midblock and cause exudation; the onset of exudation should be checked by compression-set testing under ISO 815-1:2019 or by visual inspection after 7 days at 23 °C.

Where YH-533 is dry-blended into a polypropylene homopolymer with a melt flow rate of 3 g/10 min, addition levels between 10 wt% and 30 wt% reduce low-temperature brittle failure while lowering flexural modulus from approximately 1500 MPa to 400–700 MPa, depending on rubber-phase morphology. Notched Izod impact under ISO 180:2019 at −20 °C improves only when the dispersed rubber domains remain below 1 µm in number-average diameter; this requires minimum specific energy input above 0.20 kWh/kg in the melt-mixing zone. If screw speed is too low to reach that energy threshold, impact results remain unchanged even though the compound appears homogeneous. For highly filled or highly oriented polypropylene systems, published data for this specific configuration is limited.

When YH-533 replaces unhydrogenated SBS in PP compounds

Substitution of unhydrogenated SBS with YH-533 in a polypropylene impact modifier generally lowers odour, reduces yellowing after 500 h of QUV-A 340 exposure under ASTM G154-23, and raises continuous-use temperature by approximately 20–30 °C. The trade-off is a reduction in low-temperature elasticity: the ethylene-butylene midblock has a higher glass-transition temperature than a high-cis-butadiene midblock, so compounded products may lose impact below −40 °C unless rubber content is increased or the polypropylene grade is selected with lower crystallinity. Tensile yield stress, measured under ISO 527-2:2012, typically decreases by 10–20% at 30 wt% rubber loading, while elongation at yield remains dependent on matrix orientation and processing history.

Unlike oil-extended SEBS grades commonly used for soft-touch applications, YH-533 is shipped without paraffinic oil. This absence of oil removes a source of lot-to-lot plasticizer variation and allows the compounder to select a higher molecular weight oil for low-fogging automotive interiors under VDA 278:2011. However, the neat form also requires higher shear input during initial dispersion because there is no oil to reduce viscosity in the feed zone.

Regulatory limits, storage stability, and contamination boundaries

Under REACH, the neat polymer is considered a substance rather than a preparation; no SVHC is intentionally added. RoHS 2011/65/EU heavy-metal screens for lead, mercury, hexavalent chromium, PBB, and PBDE should be run on the final compound because additives and colour concentrates can introduce non-compliant elements. FDA 21 CFR 177.2600 and EU 10/2011 require migration testing on the finished article; completion of a compliance statement for the polymer alone is not sufficient.

YH-533 retains batch-certificate properties for 24 months when stored below 40 °C, protected from direct sunlight and moisture. Storage next to hot silos or steam trace lines should be avoided because agglomeration begins when surface temperature approaches 60 °C. The grade should not be blended with amine-based additives or unsaturated nitrile rubber scrap; amine stabilizers can decompose, and the unsaturated nitrile phase can accelerate oxidative chain scission at processing temperatures.