Product SINOPEC Baling Hunan SBS YH-801 is a linear styrene-butadiene-styrene triblock copolymer manufactured by SINOPEC Baling Petrochemical Co., Ltd. at the Yueyang, Hunan polymerization complex. The grade is supplied as a non-oil-extended porous crumb or densified pellet and is used in thermoplastic elastomer compounding, footwear soling, polymer-modified bitumen, pressure-sensitive adhesive formulations, and impact modification of styrenic and olefinic resins. The YH-801 designation identifies a controlled styrene/butadiene mass ratio and a linear molecular architecture in which polystyrene end blocks are covalently bonded to a polybutadiene midblock. Phase separation of the styrene domains produces physical crosslinks that are thermoreversible, allowing the material to be processed on conventional thermoplastic equipment while retaining elastomeric behavior at service temperatures.

The grade is commonly compared with higher-styrene linear SBS grades such as YH-792 and with oil-extended or radial star-branched SBS types. YH-801 is positioned as a lower-styrene, general-purpose linear grade. Its block configuration yields lower Shore A hardness, lower tensile strength at break, and higher elongation than SBS grades containing approximately 40 wt% styrene, while its linear structure provides reduced melt viscosity relative to star-branched SBS of comparable styrene content. This combination is relevant in asphalt modification and adhesive compounding where low-temperature flexibility, spray viscosity control, and stable phase dispersion are preferred over maximum tensile strength.

Which Lot-Release Parameters Govern Incoming Inspection?

The following table summarizes the typical specification envelope reported for YH-801 in producer technical literature. Individual lot results may differ, and the manufacturer’s certificate of analysis is the normative document for each shipment.

The 30–32 wt% styrene content positions YH-801 below high-styrene grades such as YH-792, which commonly carry approximately 40 wt% styrene. This lower styrene fraction reduces the volume fraction of glassy polystyrene domains, producing a softer elastomer with lower room-temperature tensile strength and higher elongation. For applications requiring hardness above 85 Shore A, YH-801 can be compounded with general-purpose polystyrene at 10–30 phr; however, the blending operation must generate sufficient shear to disperses the polystyrene as a fine particulate or co-continuous phase rather than as large domains that reduce tear strength. Unlike oil-extended SBS grades, YH-801 contains no process oil at the point of supply, allowing the formulator to select and load oil independently. This increases formulation flexibility but also means that oil addition must be controlled to avoid rapid hardness loss or oil migration in finished articles.

Lower Diblock Content and Physical Crosslink Density

Diblock species in SBS act as network defects because the diblock chain contains only one polystyrene end block and therefore cannot participate in two separate glassy domains. The presence of diblock raises viscous flow, lowers tensile strength, and increases stress relaxation at elevated temperature. YH-801 is specified with a diblock content of ≤1.0 wt%, which is lower than some commodity SBS grades. In practical terms, this specification provides a more complete physical network after melt processing. The effect is measurable as higher retained stress and lower compression set after repeated loading. Compounds based on YH-801 can exhibit tensile set values below 25% after 24 h relaxation following 100% elongation, evaluated according to ISO 2285:2013. The low diblock content is a parameter that differentiates YH-801 from less tightly controlled general-purpose SBS grades where diblock fractions above 2 wt% may be accepted.

The linear architecture further differentiates YH-801 from radial star-branched SBS of the same styrene content. In melt processing, linear SBS exhibits lower zero-shear viscosity and lower die swell than star-branched grades, which is useful in thin-wall injection moulding and in bitumen blending. In solution, the linear structure yields lower solution viscosity at equivalent solids; in adhesive coating, this allows higher solids loading without exceeding spray-viscosity limits. The trade-off is reduced tensile strength and lower upper service temperature relative to star-branched grades because the linear molecule lacks the multifunctional branch point that retards physical crosslink relaxation above 80°C.

If the Grade Is Compounded on a Twin-Screw Extruder at 200°C

The processing window for YH-801 is defined by melt rheology and the thermal sensitivity of the polybutadiene midblock. On a co-rotating twin-screw extruder with an L/D ratio of 36:1 to 48:1, barrel zones are typically set from 150°C in the feed section to 200–220°C at the die. A segmented screw configuration with kneading blocks in the second and third zones is preferred for oil absorption and filler dispersion. Screw speeds of 200–400 rpm and residence times of 60–120 s are commonly used. The maximum melt temperature measured by an infrared probe should not exceed 230°C; above this threshold, thermo-oxidative degradation of the polybutadiene segment produces gel particles and reduces elongation. At the lower boundary, barrel temperatures below 150°C increase motor torque, and on production lines the torque may exceed 85% of available motor rating. Localized shear heating can then generate non-uniform melt temperatures even when barrel setpoints remain unchanged.

Before compounding or injection moulding, YH-801 porous crumb or densified pellets should be dried for 2 h at 60–70°C if ambient relative humidity exceeds 60 %RH. Moisture above 0.1 wt% can produce surface splay in injection moulded parts and reduce melt strength in continuous extrusion. In extrusion compounding, downstream feeding of filler after the polymer is molten reduces barrel wear and prevents excessive shear heating. If process oil is added, naphthenic oil is normally injected at 5–20 phr in footwear compounds because paraffinic and naphthenic oils plasticize the polybutadiene phase without dissolving the polystyrene domains as strongly as high-aromatic oil. High-aromatic oil tends to plasticize the polystyrene end blocks, reducing tensile strength disproportionately.

In injection-moulded footwear compounds formulated with YH-801, common ingredients include 15–35 phr general-purpose polystyrene, 5–20 phr naphthenic oil, 0.5–1.0 phr phenolic antioxidant, and 0.2–0.5 phr zinc stearate. Screw back pressure of 0.5–1.0 MPa and injection speed of 40–80 mm/s are used to avoid jetting. The resulting hardness is adjusted to 60–70 Shore A for midsoles or 75–85 Shore A for outsoles. The low diblock content contributes to dimensional stability and low tensile set after repeated flexing.

Asphalt Modification Requires a High-Shear Thermal Window Near 180°C

In polymer-modified bitumen, YH-801 is typically milled into hot asphalt at 175–185°C using a rotor–stator high-shear mixer. Mixing time of 60–120 min at rotor tip speeds of 15–25 m/s is common to reach equilibrium particle size. The polymer addition level is commonly 3–6 wt% relative to bitumen. The lower styrene content of YH-801 improves low-temperature flexibility of the modified binder; the difference from YH-792 is a smaller increase in ring-and-ball softening point for the same polymer loading because the polystyrene domains in YH-801 are less extensive. For a given bitumen source, YH-801 can produce a lower viscosity at 135°C than YH-792 at equal polymer content, which may favour pumping and spraying. The performance of the modified binder should be verified by ASTM D5973 for ring-and-ball softening point, ASTM D6084 for elastic recovery, and ASTM D4402 or EN 13302 for Brookfield viscosity. If the bitumen temperature exceeds 190°C, crosslinked gel can form from polybutadiene unsaturation; if the temperature falls below 170°C, dispersion slows and the product may remain as coarse particles that reduce elastic recovery and storage stability.

For solvent-borne contact adhesives, YH-801 is dissolved in toluene, cyclohexane, or toluene/hexane mixtures at 15–25% solids. The linear structure gives lower solution viscosity than radial SBS, permitting spraying through 0.3–0.5 mm nozzles at 0.3–0.5 MPa atomizing pressure without stringing. When compared with higher-styrene grades, YH-801 provides lower initial strength and longer open time; blending with 10–20 wt% hydrocarbon resin raises peel strength on low-density polyethylene surfaces. The lower diblock content reduces the tendency of the solution to form fibrous strands during roller coating.

In plastic impact modification, addition of 5–15 wt% YH-801 to polypropylene or high-impact polystyrene can increase notched Izod impact strength, but the extrusion step must produce a dispersed SBS particle size below about 1 μm. Larger domains can reduce tensile strength and gloss. Twin-screw compounding at 190–210°C with moderate shear is usually sufficient when the SBS is pre-blended with the matrix resin. The non-oil-extended nature of YH-801 avoids introducing process oil into the host resin, which is an advantage in applications where oil migration must be minimized.

Regulatory documentation for YH-801 can include REACH registration and RoHS compliance data from the producer. Food-contact status under 21 CFR 177.1640 or EU Regulation 10/2011 must be confirmed for the specific finished article and intended food type because YH-801 is sold as a bulk industrial elastomer, not as a food-contact-approved compound. Antioxidant systems, polymerization residuals, and intended service conditions can affect migration limits. The polymer is not recommended for continuous service in contact with strong oxidizing acids, high-aromatic solvents, or prolonged UV exposure at elevated temperature without adequate stabilizers. Aliphatic and naphthenic process oils are preferred; high-aromatic oils plasticize the polystyrene domains and reduce tensile strength disproportionately. Amine-based antiozonants are generally avoided in white or bright-coloured formulations because of staining and variable oxidative induction time; sterically hindered phenolics and phosphite stabilizer packages are preferred for long-term heat aging.