SINOPEC Baling SEBS YH-602T is a linear triblock copolymer composed of polystyrene end blocks and a saturated poly(ethylene-co-butylene) midblock. The polymer is produced by anionic polymerization of styrene and butadiene followed by selective hydrogenation of the midblock. The CAS Registry Number 66070-58-4 applies to the SEBS copolymer class. Saturation removes the main-chain unsaturation present in the SBS precursor and alters long-term thermal and ultraviolet ageing behaviour. The grade designation YH-602T sits in the high-styrene segment of the Baling SEBS product line; manufacturer-published trade literature typically places the styrene mass fraction for this series between 30% and 36%, although the lot certificate remains the controlling specification. The material is supplied as a free-flowing powder or densified particle and is intended for compounding, hot-melt adhesives, polymer modification, sealants, asphalt modification, and selected thermoplastic elastomer applications.

Which specification fields control YH-602T in comparison with adjacent SEBS grades?

The controlling certificate of analysis for SEBS YH-602T records styrene mass fraction, volatile matter, ash content, hardness, tensile properties, and melt mass-flow rate. Test methods used for lot release are generally aligned with rubber and thermoplastic elastomer standards. The following table consolidates representative product-line values for high-styrene Baling SEBS grades; SINOPEC Baling does not publish a fully harmonized international datasheet for YH-602T, and lot certificates may differ. The table should not be used as a purchase specification without lot-level confirmation.

Comparative lot selection should also record solution viscosity and residual diblock content when solvent-based processing is used. The manufacturer commonly reports residual styrene-butadiene diblock content separately because elevated diblock content lowers tensile strength and increases tack in hot-melt formulations.

Melt Processing Boundaries and Oil Uptake Behaviour

When YH-602T is compounded with polypropylene and white mineral oil, the processing sequence uses a high-shear twin-screw extruder with a length-to-diameter ratio of 40:1 to 52:1. An atmospheric or vacuum vent is required to remove volatile residues, and oil injection is staged downstream of the first melting zone to preserve the polystyrene end-block network during initial fusion. Barrel temperatures from feed to die are typically profiled from 160 °C to 210 °C. Melt temperatures above 230 °C may initiate oxidative gel formation during extended residence time. In production-scale compounding, screw speeds between 200 rpm and 400 rpm are used with torque control rather than temperature override. The powder dosage rate and side-stuffer speed are set by the maximum feed capacity of the extruder.

Batch-to-batch variation in SEBS powder bulk density can alter gravimetric feeder output by as much as 5%; feeder recalibration is required when switching lot numbers. The material may require pre-drying when open storage has exposed the powder to relative humidity above 60%. Surface moisture pickup can cause porosity in extruded profiles and reduced tensile strength. Drying at 60 °C to 80 °C for 2 hours to 4 hours in a desiccant dryer or tray dryer is generally employed before processing.

Oil uptake is not unlimited. YH-602T can be compounded at oil loadings typical of high-hardness SEBS compounds, but excessive paraffinic oil addition collapses the polystyrene domain network and produces a discontinuous phase with low tensile strength. The critical oil loading is formulation-specific and must be determined by hardness, tensile strength, and compression set testing. Aromatic process oils with high solvent power for polystyrene should be avoided because they plasticize the end-block domains and reduce creep resistance. Paraffinic white oils with aromatic content below 5% are generally preferred.

In injection molding of YH-602T-based compounds, clamp force requirements may increase relative to lower-hardness SEBS compounds because the high styrene content raises viscosity at low shear rates. The melt should be evaluated over the shear-rate range encountered in the runner and gate, not only by single-point melt mass-flow rate. Injection molding trials on machines with clamp force from 800 kN to 3,200 kN have been reported for SEBS compounds of similar Shore harness, but published data for this specific grade are limited.

When YH-602T replaces SBS in oxidative and UV-exposed compounds

In applications where the base polymer must survive repetitive thermal cycling or outdoor exposure, the saturated ethylene/butylene midblock in YH-602T reduces the concentration of allylic hydrogen atoms available for radical chain degradation. Under accelerated ageing test methods such as ISO 188:2011, SEBS compounds typically retain a higher percentage of original tensile strength than SBS compounds of similar styrene content. However, published comparative data for YH-602T specifically are limited; compound-level ageing results depend on antioxidant package, filler, process oil quality, and end-use temperature.

In a direct SBS replacement, hardness and tensile modulus often increase because the high-styrene SEBS forms a more continuous polystyrene domain network. The melt-processing window narrows relative to lower-styrene SBS because polystyrene end-block association raises low-shear viscosity. Processing measurements should be taken at 190 °C and 230 °C according to ISO 1133-1:2022 to establish the comparative flow curve. When the same screw design and temperature profile are retained, a SBS-to-YH-602T substitution may require increased screw torque and higher melt pressure at the die. Equipment operators should monitor head pressure and melt temperature at start-up; an increase above 10% over the SBS baseline indicates that screw speed or temperature profile adjustments are needed.

Compared with maleic anhydride-grafted SEBS, YH-602T is not functionalized. It will not spontaneously bond to nylon, polyethylene terephthalate, or metal surfaces. Interfacial adhesion to polar engineering thermoplastics requires a separate compatibilizer or a grafted SEBS tie layer. In multi-layer structures, the selection between YH-602T and maleated SEBS should be based on peel strength after bonding measured according to ASTM D3330/D3330M-04 or an equivalent T-peel method.

The difference between YH-602T and lower-styrene Baling SEBS grades such as YH-502 is primarily a shift in the rubber-to-plastic balance. YH-502 is typically selected when lower hardness and higher elongation are required. YH-503 provides an intermediate styrene content and is often used for general-purpose compounds. YH-602T is positioned for higher hardness, higher tensile strength, and greater resistance to heat distortion. The higher styrene content also raises the glass transition temperature of the polystyrene microphase, so dynamic mechanical analysis shows a higher softening point than lower-styrene grades. This distinction should be confirmed by dynamic mechanical thermal analysis rather than inferred from Shore A hardness alone.

In hot-melt pressure-sensitive adhesives, YH-602T is dissolved in a paraffinic or naphthenic process oil at temperatures between 150 °C and 180 °C with tackifier addition under nitrogen or a sealed mixer to limit oxidation. Adhesive viscosity is measured with a Brookfield thermosel viscometer at 180 °C; target values depend on coating equipment and substrate. Loop tack and 180° peel adhesion are tested according to ASTM D6195-03 and ASTM D3330/D3330M-04, respectively. Shear adhesion failure temperature is evaluated under ASTM D4498-13. The higher styrene content of YH-602T relative to YH-503 generally shifts the adhesive failure mechanism from cohesive to interfacial at lower tackifier concentration, but the transition point must be measured for each formulation.

In polymer modification, YH-602T at 10% to 30% by mass in polypropylene improves low-temperature impact toughness. Notched Izod impact strength is evaluated per ISO 180:2023 or ASTM D256-23, and flexural modulus per ISO 178:2019 or ASTM D790-17. The actual result is a function of phase morphology and processing shear; compounders should map the property surface with a design of experiments rather than assume linear additive response. At addition levels above 25%, melt flow and flexural modulus may decrease rapidly; this property cliff-edge must be measured for each base polypropylene resin and screw configuration.

In asphalt modification, YH-602T is dispersed into hot bitumen at 180 °C to 200 °C under high-shear rotor-stator mixing. The SEBS content in asphalt blends typically ranges from 4% to 8% by mass. Storage stability is assessed by hot storage separation testing, and separation tendency is compared with SBS-modified asphalt. The saturated midblock reduces high-temperature oxidation of the modifier compared with SBS; however, compatibility with the specific bitumen source controls phase separation. Relevant test methods include penetration ASTM D5/D5M-20, softening point ASTM D36/D36M-14, and dynamic shear rheometer measurements under ASTM D7175-15. Published comparative data for YH-602T in specific bitumen grades are limited; jar testing and DSR frequency sweeps are required before production qualification.

For wire and cable jacket compounds based on SEBS YH-602T, the base polymer is not flame-retardant. A typical halogen-free formulation contains magnesium hydroxide or magnesium carbonate at loadings of 50% to 65% by mass. Elongation and tensile properties are tested after thermal ageing per IEC 60811-501, volume resistivity per IEC 62631-3-1, and heat shock performance per IEC 60811-508. RoHS 2011/65/EU and REACH compliance must be verified on the final compound and any color concentrates because the base polymer does not automatically confer regulatory compliance to the finished article. Halogenated flame retardants that generate acidic species at processing temperatures may accelerate degradation; hydrotalcite or calcium stearate acid scavengers can be used where acidic volatiles are present.

The polymer should be stored below 40 °C and protected from direct sunlight to minimize oxidative degradation of the antioxidant package. Avoid open storage in high-humidity environments; when relative humidity exceeds 60%, sealed packaging and pre-drying are required before melt processing. The product is not intended for use in applications requiring direct food contact unless the finished compound is tested and approved against the relevant food-contact regulation. For EU applications, migration testing according to EU 10/2011 would be required on the finished article.