Sinopec Baling Hunan SBS YH-1401 is a linear styrene-butadiene-styrene thermoplastic elastomer manufactured by the Sinopec Baling Petrochemical subsidiary in Hunan, China. The grade is supplied as a white porous pellet or granular solid with a nominal styrene/butadiene mass ratio of 40/60 and a non-oil-extended formulation. It is positioned in the Baling SBS portfolio for bituminous waterproofing, polymer-modified asphalt, high-strength thermoplastic compounds, and solvent-borne adhesives. The property values in this document are representative supplier technical literature data, not a batch release certificate; contract specifications may set narrower release limits.

Lot-to-lot variation in the SBS polymerization can shift the diblock content from 0.5 wt% to 1.0 wt%. In asphalt modification, diblock content above 1.0 wt% may reduce elastic recovery because non-coupled butadiene chains do not participate in the styrene-crosslinked network. Production-scale users therefore monitor the grade by gel permeation chromatography and Fourier-transform infrared spectroscopy after incoming receipt.

What Is the Structural Basis for the Grade’s Melt Rheology and Thermoplastic Character?

The 40/60 styrene/butadiene mass ratio produces a two-phase morphology in which the polybutadiene midblock forms a continuous rubber phase and the polystyrene end-blocks segregate into glassy domains. These domains act as physical crosslinks below the polystyrene glass transition near 95 °C; above that threshold the domains soften, allowing thermoplastic flow. The polybutadiene phase contributes low-temperature flexibility with a glass transition near -85 °C, although the unsaturated midblock remains susceptible to oxidation and UV degradation unless stabilised.

The linear architecture and high molecular weight of YH-1401 result in a melt flow rate in the range of 0.3–2.0 g/10 min under 200 °C/5 kg load according to ISO 1133-1:2022. This is lower than standard adhesive-grade SBS materials such as YH-792, which typically shows higher melt flow. In compounding, the material is usually processed on corotating twin-screw extruders with L/D 48 or greater, using a barrel profile from 140 °C in the feed zone to 190 °C at the die. Screw speeds of 250–400 min⁻¹ provide sufficient shear for dispersion; melt temperatures above 200 °C are not recommended because the butadiene block can undergo thermal degradation and gel formation.

The grade has a tensile strength not less than 24 MPa and elongation at break not less than 600% when tested on compression-molded sheets according to ISO 37:2017. Hardness is typically 85–90 Shore A under ISO 48-4:2018 or ASTM D2240. Density at 23 °C is approximately 0.94 g/cm³ under ISO 2781:2018. The low diblock content, usually ≤1 wt%, is significant because higher diblock fractions lower tensile strength and increase cold flow in adhesive and asphalt applications.

Because the material is non-oil-extended, it is shipped as high-hardness crumb or pellets. Cold flow during ambient storage can occur in warehouses above 30 °C; pallet stacking above two high may cause blocking. SBS pellets should be stored below 40 °C and protected from UV exposure. Surface oxidation, visible as yellowing, does not necessarily alter bulk melt viscosity but can affect clarity in light-colored compounds.

At 4–6 wt% addition to paving-grade bitumen, YH-1401 is typically dispersed in a high-shear mixer at 170–180 °C for 40–60 min. Rotor-stator clearances below 0.5 mm are used on production-scale polymer-modified bitumen plants to break the SBS pellets into a fine continuous network. The resulting polymer-modified bitumen is evaluated according to EN 14023:2010, ASTM D36 for softening point, ASTM D6084 for elastic recovery, and ASTM D4402 for Brookfield viscosity at 135 °C. On production-scale PMB units, batch-to-batch variation in SBS pellet size can influence wetting and dispersion rate. Preheating the bitumen to 160 °C before SBS addition and maintaining high-shear recirculation prevents undispersed gel particles that would otherwise appear in fluorescence microscopy as swollen SBS domains larger than 10 µm.

In mill-scale and plant-scale trials, the practical upper dosing limit is normally governed by viscosity increase rather than solubility. At 6 wt% SBS, Brookfield viscosity at 135 °C may exceed 3 Pa·s, requiring heated transfer lines and positive-displacement pumps; at 4 wt% the viscosity remains lower and is more compatible with conventional road paving equipment. Published data for this specific grade in all regional bitumen sources is limited, so the exact viscosity plateau must be confirmed against the project bitumen’s saturate, aromatic, resin, and asphaltene fractions.

The type of bitumen has a large effect on phase stability. In paraffinic or high-wax bitumen, storage stability can be lower because the SBS phase separates during static storage. The tube test under EN 13399 can quantify top-bottom softening point difference. For such systems, the SBS dosage may be reduced to 2–4 wt% and a reactive compatibility agent is added. In naphthenic aromatic bitumen, YH-1401 typically disperses without compatibility agents because the aromatic fraction swells the polystyrene domains and improves network formation.

The high styrene content of 40 wt% contributes to high-temperature softening point and elastic recovery but raises low-temperature flexibility limits compared with 30/70 SBS grades. In cold-climate modified asphalt, formulators may blend YH-1401 with lower-styrene grades or process oils to balance high-temperature rutting resistance with low-temperature cracking resistance under EN 12591 or ASTM D6373 conditions.

When YH-1401 Is Compounded into Solvent-Borne Adhesives and Sealants

When YH-1401 is compounded into solvent-borne contact adhesives and sealants, the high molecular weight produces high solution viscosity at moderate solids. For a 20 wt% solids solution in toluene, Brookfield viscosity can reach several Pa·s, which restricts spray application and favours brush or roller coating. Reducing solids to 15 wt% or blending with YH-792 is common when lower-viscosity spray systems are required.

For solvent-based adhesives, the polymer is allowed to dissolve under low-shear agitation at 20–25 °C for 4–8 h to avoid excessive chain breakdown. High-speed dispersers can generate enough heat to raise solution temperature above 40 °C, which accelerates oxidation; nitrogen blanketing or antioxidant addition is used in large tanks.

Compatible tackifier systems include C5 aliphatic resins, C9 aromatic resins, and rosin esters. Aromatic process oils above 30 phr should be avoided because they preferentially swell the polystyrene domains and reduce cohesive strength. Naphthenic or paraffinic oils at 5–20 phr are used for viscosity adjustment with less loss of tensile properties. Reference adhesion values are tested according to ASTM D903 or ISO 4587 on bonded substrates; peel strength depends on substrate surface energy, coat weight, and open time.

Pre-drying of pellets at 60–80 °C for 1–2 h with desiccant-dried air is recommended when storage relative humidity exceeds 60%. The grade is hydrophobic, but surface moisture can create steam bubbles during melt compounding. Avoid melt temperatures above 200 °C and avoid strong oxidizing agents; the unsaturated polybutadiene block can degrade by chain scission and crosslinking under prolonged high-shear and high-temperature conditions.

Thermoplastic Compounding and Footwear Modification Windows

In polypropylene and polystyrene compounds, YH-1401 is incorporated at 10–30 wt% to improve impact toughness and reduce brittle failure. The trade-off is a reduction in flexural modulus and heat deflection temperature. On a corotating twin-screw extruder, the material is typically fed in the main throat with the polyolefin, while oil or lubricants are injected downstream. Impact results are evaluated under ISO 180 or ASTM D256; flexural modulus under ISO 178 or ASTM D790.

In impact modification, the SBS rubber particle size and distribution depend on screw configuration. A kneading block section with 30–45° forward angles is used to disperse the SBS into a continuous polypropylene matrix. Too high specific mechanical energy input above 0.25 kWh/kg can degrade the polybutadiene block and reduce Charpy notch impact strength. Processors usually calibrate screw speed and throughput to maintain melt temperature below 190 °C at the die plate.

In footwear compounds, YH-1401 acts as a high-strength modifier for rubber-resin blends. It is blended with polystyrene, hydrocarbon resin, and oil at 140–170 °C in internal mixers or extruders. The non-oil-extended nature of YH-1401 requires the formulator to control oil level separately; oil uptake is lower than oil-extended grades, so the final hardness can be adjusted over a wider range. Slip resistance and abrasion are measured according to ASTM D5963 or ISO 4649.

The grade is produced under an ISO 9001 quality system. For final articles intended for food-contact use, converters must verify that the specific compound meets FDA 21 CFR 177.1810, which covers styrene block polymers used in repeated-use rubber articles. REACH and RoHS compliance statements are typically provided by the supplier on a per-shipment basis. EN 71-3 migration of certain elements applies only to finished toy formulations, not to the neat SBS granulate.

The Difference Between YH-1401 and Lower-Styrene, Oil-Extended, or Star-Branched Grades Is Visible in Viscosity and Strength

The primary distinction between YH-1401 and lower-styrene linear grades such as YH-791 is the styrene/butadiene mass ratio. YH-791 is typically supplied at 30/70 and has lower tensile strength and Shore hardness, which makes it softer and more rubbery but less resistant to high-temperature deformation. YH-1401, at 40/60, exhibits higher tensile strength, higher modulus, and higher hardness, although it sacrifices some low-temperature elasticity. Both are linear, but YH-1401 is positioned for applications requiring higher mechanical integrity.

Compared with YH-792, which also has a 40/60 styrene/butadiene ratio but a lower molecular weight, YH-1401 has lower melt flow and higher solution viscosity. In adhesive and footwear applications where fast wetting and low melt viscosity are required, YH-792 is often preferred. In bituminous systems where high molecular weight improves high-temperature elastic recovery and storage stability, YH-1401 is selected. The exact molecular weight cut is not disclosed on the public datasheet, but the melt flow difference is measurable under ISO 1133-1:2022.

Against star-branched SBS grades such as YH-802, the linear YH-1401 generally shows lower melt elasticity and lower coupling efficiency but more predictable thermoplastic flow. Star-branched structures can provide higher tensile strength at equal molecular weight, though they may require higher processing temperatures. The choice between YH-1401 and a star-branched grade depends on whether the downstream process is elongation-dominated or shear-dominated; in extrusion and bitumen dispersion, the linear grade is often easier to handle at moderate shear, while star grades may be chosen for high melt strength and improved cohesive strength.