SINOPEC Baling SEPS YH-4053 is a selectively hydrogenated styrenic thermoplastic elastomer based on a styrene-ethylene/propylene-styrene triblock architecture. The product is supplied as white porous pellets and is manufactured by catalytic hydrogenation of a styrene-isoprene-styrene precursor, saturating the midblock while retaining polystyrene end blocks. The amorphous ethylene-propylene midblock imparts a glass transition temperature below -40°C when evaluated by differential scanning calorimetry according to ISO 11357-2:2020. The YH-4053 designator identifies a linear grade within the Baling SEPS series. In release documentation, the grade is positioned for soft compounds, polymer modification, adhesives, sealants, and articles requiring reduced main-chain unsaturation relative to SIS. Lot-specific certificates govern final property limits and batch-to-batch variance.

Molecular architecture and specification range

The block copolymer contains two polystyrene segments flanking a saturated ethylene-propylene midblock. The selective hydrogenation step is controlled to achieve a hydrogenation degree above 98% in the manufacturer’s internal release method. This saturation reduces susceptibility to ozone cracking and oxidative chain scission during prolonged thermal aging. In contrast to unhydrogenated SIS, the midblock does not undergo rapid degradation under cyclic strain; ozone resistance is assessed according to ISO 1431-1:2022. The aromatic end blocks retain the ability to form physical crosslinks below the styrene glass transition, while melt processing remains thermoplastic above 100°C. Table 1 summarizes representative technical data sheet values for the grade.

Values shown are representative manufacturer technical data sheet figures; lot-specific release values may differ and should be confirmed before specification locking. Published data for this specific configuration is limited in some application-specific performance areas, particularly long-term load-bearing behavior.

What processing boundaries define the compounding window?

Compounding on a production-scale co-rotating twin-screw extruder with L/D 40:1 and segmented kneading elements requires melt temperatures in the range 190–230°C. The temperature profile is typically set with feed zone at 160°C, ramping to 210°C, and die at 200°C; actual barrel settings require adjustment for screw speed and throughput. Pre-drying at 80°C for 2 h in a desiccant dryer is recommended when ambient relative humidity exceeds 60%. Moisture levels above 0.1% can produce surface defects during extrusion. In injection molding, melt temperatures of 200–230°C and injection pressures between 40 MPa and 80 MPa are common for soft-touch SEPS compounds. Residence time above 10 min at melt temperatures exceeding 260°C should be avoided because polystyrene domain degradation and midblock chain scission may occur.

For soft-touch grips and roll covers, YH-4053 is compounded with paraffinic white oil at ratios from 20 phr to 150 phr. At oil loadings above 100 phr, Shore A hardness values below 15 are achievable, but tensile strength and tear resistance decline proportionally. Compression set after 22 h at 70°C according to ISO 815-1:2014 typically remains below 60% for formulations containing high molecular weight SEPS, although published data for this specific configuration is limited and must be confirmed by laboratory compounding. The saturated midblock reduces oil evaporation loss versus SIS in hot air aging at 100°C per ISO 188:2023.

When soft-touch compounds must retain oil without migration

Mineral oil selection should use kinematic viscosity between 50 cSt and 500 cSt at 40°C per ASTM D445-21. Lower-viscosity oils reduce compound hardness but increase extractability under ISO 6427:2013. The ethylene-propylene midblock has greater compatibility with aliphatic and naphthenic oils than styrene-butadiene midblocks, permitting higher oil loading before macroscopic migration occurs. For formulations requiring low surface tack after aging, a high molecular weight SEPS grade or partial replacement with SEBS is typically necessary. Published data for this specific configuration is limited for oil retention under contact pressure; qualification should include ISO 10147:2012 or equivalent extraction testing on finished articles.

Hot-melt adhesive formulations using YH-4053 typically combine the elastomer with hydrogenated tackifier resins at 20–50 wt% and paraffinic or naphthenic process oils at 5–20 wt%. Brookfield viscosity at 180°C per ASTM D3236-15 is controlled by resin softening point and elastomer molecular weight. Compared with SIS-based hot melts, YH-4053 formulations exhibit lower color development during 72 h aging at 177°C and improved retention of peel adhesion on polypropylene substrates when tested per ASTM D903-98(2024). The grade may require higher application temperatures than low-viscosity SIS grades; published data for open-time adjustment in this specific configuration is limited and should be evaluated on production coating equipment.

Medical device applications require lot-specific evaluation under ISO 10993-5:2009 and ISO 10993-10:2021. The grade can be processed without vulcanization, eliminating sulfur or accelerators; however, antioxidant systems and mineral oil grades must be selected for USP Class VI or relevant national pharmacopoeia requirements. Regulatory compliance for food-contact adhesives may be reviewed under FDA 21 CFR 175.105 or 177.2600 depending on the article type. REACH and RoHS documentation is lot-specific; no halogenated flame retardants are used in the base polymer.

In polyolefin modification, YH-4053 is used as an impact modifier and compatibilizer. At addition levels of 5–20 wt% in polypropylene homopolymer, notched Izod impact at -20°C per ISO 180:2023 commonly increases relative to unmodified homopolymer, while tensile yield strength declines roughly in proportion to elastomer content. The ethylene-propylene midblock has better compatibility with polypropylene than styrene-butadiene midblocks, reducing dispersed-phase size in co-continuous morphologies. Twin-screw compounding at 200–230°C with a screw speed of 300–500 rpm is typical for this application, but published data for this specific grade is limited and laboratory compounding is required.

Bituminous modification with YH-4053 uses addition levels of 3–8 wt% relative to base asphalt. The saturated midblock maintains storage stability in hot mix tanks under agitation at 180–190°C, and ring-and-ball softening point is measured per ASTM D36-14. Compared with SIS-modified asphalt, YH-4053 provides lower viscosity build at equivalent polymer loading and reduced degradation after thin-film oven aging per ASTM D1754-14. Low-temperature flexibility is evaluated by bending beam rheometer methods per ASTM D6648-08; published data for this specific configuration is limited and should be verified on production-scale blending units.

Relative to conventional SEBS grades, YH-4053 yields softer compounds at equivalent styrene content and aromatic block fraction. The ethylene-propylene midblock has a lower plateau modulus than the ethylene-butylene midblock of SEBS, which translates to lower hardness and lower tensile strength but higher elastic recovery. In cyclic tensile testing at 100% strain, residual set after 60 min per ISO 2285:2019 is typically lower than for SIS and similar to or slightly below equivalent SEBS formulations. The grade should not be combined with strong oxidizing agents or exposed to sustained temperatures above 260°C, at which polystyrene domains degrade and the ethylene-propylene midblock may undergo chain scission.