Within the hydrogenated styrenic block copolymer class, SINOPEC Baling SEBS YH-504T is a linear triblock copolymer in which styrene endblocks are separated by a saturated ethylene/butylene midblock. The midblock saturation removes the main-chain allylic double bonds that otherwise dominate oxidative, ozone, and ultraviolet degradation in unhydrogenated SBS. Phase-separated polystyrene domains act as thermally reversible physical crosslinks; the ethylene/butylene phase contributes low glass-transition behaviour and extensibility. Manufacturer technical literature places the nominal styrene content at 34 wt% and typical density at 0.91 g/cm³ under ASTM D792-20. The standard shipment form is a free-flowing white pellet with low residual volatiles. YH-504T is directed toward compounding of thermoplastic elastomers, hot-melt adhesives, sealants, asphalt modification, and toughness modification of polyolefin compounds. The product designation does not contain processing oil; final compound hardness is therefore controlled by oil addition, filler loading, and polypropylene content rather than by a pre-oiled base. The molecular weight and styrene distribution produce a property envelope combining cohesive strength, elevated softening performance, and a dry non-blocking surface in unfilled mouldings.

The grade is differentiated from lower-styrene SEBS grades in the Baling portfolio by a higher endblock fraction. That shift increases tensile modulus, hardness, and high-temperature property retention but reduces melt flow. In production-scale compounding on a co-rotating twin-screw extruder with an L/D of 40:1, the material typically requires barrel temperatures from 170 °C in the feed section to 220 °C at the die to achieve stable melt homogenisation. Pre-drying at 80 °C for 2 h is recommended when storage relative humidity exceeds 60%, because condensed moisture can cause surface defects in extruded profiles. The viscosity curve under ISO 1133-1:2022 at 230 °C/5 kg indicates a medium-flow grade relative to high-viscosity adhesive types; however, actual flow at processing shear is strongly shear-thinning and should be confirmed by capillary rheometry rather than by melt index alone.

What Processing Consequences Arise When YH-504T Replaces Unhydrogenated SBS in a Compound?

Replacement of SBS with YH-504T generally raises the practical processing temperature by 20 °C to 30 °C because the hydrogenated midblock has no unsaturated double bonds to initiate radical scission at elevated temperatures. In twin-screw compounding, the absence of double bonds also reduces the risk of gel formation at hot spots; however, the higher melt viscosity increases specific mechanical energy input. On a 52:1 L/D co-rotating twin-screw extruder, operators often observe an increase in motor load relative to an equivalent melt-index SBS formulation. This requires torque-limited extrusion planning and may require mid-barrel oil injection rather than dry-blending oil into the feed throat. For injection moulding, melt temperatures between 190 °C and 230 °C and mould temperatures of 30 °C to 50 °C are typical. The styrenic domain reformation rate during cooling controls part stiffness development; higher mould temperatures allow more complete domain ordering and yield higher tensile modulus but extend cycle time. The saturated midblock also permits end-use exposure to 110 °C intermittent air ageing without the rapid embrittlement seen in SBS, as evaluated by retained elongation under ISO 188:2011 hot-air ageing.

Mechanical Property Envelope and Compliance Ceiling for YH-504T Compounds

Representative property values for compression-moulded test plaques prepared from YH-504T without oil are given below. Values are typical data from manufacturer technical literature and should be verified against the certificate of analysis for the specific lot.

The moderate hardness and low density of YH-504T allow formulation below 50 Shore A by addition of paraffinic oil at 30 phr to 100 phr without immediate bleed-out when the oil solubility limit is respected. Above 100 phr, surface migration of oil can reduce coefficient of friction and interfere with printing or adhesion. Fillers such as calcium carbonate at 5 wt% to 30 wt% raise density and lower compound cost but reduce tensile strength by dilution. For polyolefin modification, addition of 5 wt% to 15 wt% YH-504T to polypropylene is reported to improve impact resistance at low temperature; published data for this specific configuration is limited, and actual results depend on polypropylene melt flow and coupling agent selection.

When Asphalt Modification Demands High-Temperature Storage Stability Without Polymer Degradation

In polymer-modified asphalt, YH-504T is dispersed into hot asphalt at 170 °C to 190 °C using high-shear mixers. The hydrogenated midblock resists chain scission during prolonged hot storage; unhydrogenated SBS can degrade at midblock double bonds under the same thermal load. Storage stability is commonly assessed by softening point difference, measured under ASTM D36 or by separation tendency under ASTM D7173-21. YH-504T is generally compounded at 3 wt% to 7 wt% of asphalt; higher loadings improve rutting resistance but increase viscosity. The styrenic endblocks provide physical crosslinks that control high-temperature rutting, while the ethylene/butylene midblock contributes low-temperature flexibility. In comparison with SBS-modified asphalt, YH-504T-modified systems show less reversion of softening point after extended hot storage, but the lower solubility of SEBS in some asphalts can require aromatic-rich compatibilizers or extended shearing. Published data for this specific configuration is limited.

On production lines using twin-screw extruders with side-feed for filler, YH-504T is added in the main feed throat; oil is injected at a downstream barrel zone after the polymer has formed a melt seal. Adding oil too early reduces friction and can cause screw slip. Batch-to-batch variation in melt flow rate is controlled by the manufacturer within a narrow range; compounders should still monitor melt pressure before the die because viscosity shift alters strand diameter and pellet quality. Processors using vacuum venting should maintain -0.08 MPa gauge pressure on the final vent to remove low-molecular-weight volatiles without pulling polymer into the vent port.

Because YH-504T is supplied without oil extension, the compounder retains a wider formulation window than with pre-oiled grades. Oil-extended SEBS grades produce low-hardness compounds with reduced viscosity and lower tensile strength. YH-504T, by contrast, begins at a higher hardness plateau and accepts oil in increments to match target Shore A values while retaining cohesive strength. In compounds targeting 50 Shore A, typical oil addition is 30 phr to 60 phr, whereas a pre-oiled grade may already be near 40 Shore A after compounding. This difference matters in specification-driven markets because final melt viscosity and hardness can be adjusted independently without changing base elastomer lot.

For hot-melt pressure-sensitive adhesive applications, YH-504T is co-melted with hydrogenated tackifying resins and paraffinic or naphthenic process oils at 160 °C to 180 °C in a sigma-blade mixer or vertical kneader. Resin loading in pressure-sensitive adhesive formulations typically ranges from 30 phr to 80 phr, while oil addition is limited to 20 phr to 50 phr to maintain cohesive strength. The saturated midblock provides viscosity stability during prolonged holding at 160 °C; published measurement of melt viscosity over 24 h at 160 °C for hydrogenated SEBS grades shows less than 10% viscosity drift, whereas unhydrogenated SBS can show larger viscosity shifts due to oxidative coupling. In adhesive application, YH-504T is used as an elastomeric base for assembly tapes, label adhesives, and construction sealants requiring non-staining performance. The absence of unsaturation limits discolouration in contact with white or light-coloured substrates under UV exposure.

Resin selection is restricted to hydrogenated tackifier resins. Aromatic C9 resins may create soft-phase mixing limitations and increase melt viscosity; a hydrogenated C5/C9 resin with a softening point of 100 °C to 120 °C is preferred because of solubility parameter matching with the ethylene/butylene midblock. For sealing compounds, compressive set resistance is governed by the completeness of styrenic domain formation during cooling; slow cooling or annealing at 60 °C improves set resistance but reduces production rate. The product should not be combined with amine-based additives that can interfere with thermal stability or promote premature crosslinking in the melt.