SINOPEC Baling SEBS YH-1361A is a linear hydrogenated styrene-butadiene-styrene triblock thermoplastic elastomer. The polybutadiene midblock is hydrogenated to a poly(ethylene-co-butylene) sequence, reducing residual unsaturation in the rubber segment and separating the grade from conventional unsaturated SBS in thermal ageing and ultraviolet exposure. The grade is supplied as a porous white pellet or crumb and is intended for thermoplastic elastomer compounding, bituminous modification, and hot-melt adhesive formulation. The polystyrene endblocks exhibit a glass transition near 95°C, while the hydrogenated midblock glass transition lies between -55°C and -50°C, establishing a broad service plateau. The linear architecture produces higher low-shear viscosity and greater melt strength than many radial SEBS grades, but it also raises melt pressure during extrusion and injection molding.

Published data for this specific configuration is limited; the following values are representative of current production and should be confirmed against the SINOPEC Baling certificate of analysis for individual lots. Differences between production trains and sampling points can shift melt flow rate by approximately 0.2 g/10 min without altering the grade designation.

What lot-release properties define YH-1361A for compounding-grade use?

Lot-release conformity for YH-1361A is established against the test methods listed below. The figures are typical production ranges, not a sales specification. The grade is released on the basis of the current SINOPEC Baling technical data sheet and certificate of analysis; the table below is a compilation of commonly reported properties.

In twin-screw extruder compounding of YH-1361A with polypropylene or polyethylene, feed-zone set points of 160–180°C and barrel profiles rising to 200–220°C are used to balance block melting against viscosity buildup. Extruders with L/D 32:1 or 40:1 and vacuum venting at -0.06 MPa to -0.08 MPa remove residual moisture and low-molecular volatiles. Screw configurations should favor distributive mixing elements over high-intensity kneading blocks, because local shear heating above 230°C can initiate thermal-oxidative chain scission and increase melt flow drift. Pre-drying at 80°C for 2–4 h is required when moisture exceeds 0.1 wt% by Karl Fischer titration; at relative humidity above 60%, closed hopper dryers are required. In injection molding of YH-1361A-based compounds, short-shot studies on machines with clamp force from 3 kN/cm² to 5 kN/cm² projected area and cushion control are used to avoid residence times beyond 6 min at 200°C.

Batch-to-batch variance in melt flow rate is observed at the beginning of production campaigns; stabilization with 0.1–0.3 wt% hindered phenolic/phosphite antioxidant and pre-blending of regrind at maximum 20 wt% limits drift. In-line melt temperature sensors and pressure transducers before the die are used to maintain specific energy input below 0.25 kWh/kg; higher energy input reduces molecular weight and lowers tensile strength. Wet pellets create surface splay and die-lip deposit. Vacuum venting at -0.06 MPa is insufficient if the feed rate exceeds the vent capacity; foaming at the die indicates volatile entrainment.

Melt rheology, drying thresholds, and high-shear compounding limits

Rheological response is shear-thinning across the processing range. The low residual unsaturation suppresses crosslinking and gel formation during normal melt processing, but extended residence at high temperature shifts molar mass distribution. Oil extension with paraffinic process oil from 20 to 100 phr reduces die pressure and Shore A hardness while retaining tensile strength; naphthenic oils are less compatible and should not exceed 30 phr without evaluating extractable content. The grade’s viscosity at low shear is governed by the linear triblock architecture; this results in higher die swell than branched SEBS and requires die land lengths of 10–15 mm in strand pelletizing to control swell.

At melt temperatures above 260°C, degradation accelerates; melt temperature measurements with a needle probe should remain below 245°C during continuous operation. The compounding window is narrower than for oil-tolerant SBS grades because the hydrogenated midblock is less polar and oil uptake is slower. Oil adsorption in a high-speed mixer at 80–100°C requires 20–30 min to reach free-flowing material before extrusion. Attempts to bypass the soak step produce die pressure fluctuations and surface roughness.

For hot-melt adhesive compounding, YH-1361A is typically formulated with hydrogenated tackifier resins having softening points between 80°C and 120°C and paraffinic oil. The open time and cohesive strength depend on the ratio of tackifier to elastomer; formulations near 1:1 tackifier-to-polymer show a balance of peel and shear. In bituminous modification, the grade is added at 3–8 wt% to asphalt with high-shear mixers at 170–180°C; the hydrogenated midblock improves viscosity-temperature balance and storage stability against phase separation compared with unsaturated SBS.

When YH-1361A replaces SBS or EPDM in a weather-exposed profile

Formulators replacing unsaturated SBS with YH-1361A in outdoor profiles should increase initial stabilizer package only for processing, not for service. The grade’s saturated midblock tolerates long-term UV exposure with lower antioxidant demand than SBS. Replacement of EPDM eliminates the vulcanization step and permits regrind reuse, but the upper continuous service temperature is lower than peroxide-cured EPDM; published data for specific YH-1361A compounds at temperatures above 100°C is limited.

The operational boundaries of YH-1361A include sensitivity to aromatic and highly polar plasticizers. Avoid low-molecular-weight aromatic oils above 5 phr and excessive levels of polyester plasticizers because these selectively swell the polystyrene endblocks and reduce tensile strength and creep resistance. The grade should not be exposed to strong oxidizing acids or high concentrations of ketone solvents. Regulatory documentation for SINOPEC Baling SEBS YH-1361A should be confirmed for food-contact applications under FDA 21 CFR 177.1810 and for European Union compliance under REACH Regulation (EC) No 1907/2006 and RoHS Directive 2011/65/EU. The product does not contain intentionally added heavy metals above the threshold limits established by the relevant annexes.