SINOPEC Baling SEBS YH-507 is a linear styrene-ethylene/butylene-styrene block copolymer manufactured by Sinopec Baling Petrochemical Co., Ltd. The grade is supplied as a neat, non-oil-extended elastomer, and its saturated ethylene/butylene mid-block provides higher resistance to oxidative and ultraviolet embrittlement than unsaturated SBS copolymers. Typical datasheet ranges consolidated from publicly available technical summaries for YH-507 report a Shore A hardness of 65 to 72, tensile strength of 18 MPa to 22 MPa, elongation at break of 400% to 550%, specific gravity of 0.92 to 0.94, and melt flow rate of 3 g/10 min to 10 g/10 min under 230 °C and 5 kg load. Tensile properties are determined under ASTM D638-14, hardness under ASTM D2240-15, specific gravity under ASTM D792-20, and melt flow rate under ISO 1133-1:2022. The current certificate of analysis is the governing release document.

Styrene endblock content is commonly reported at approximately 30 wt%. The polystyrene end blocks provide physical crosslinks at ambient temperature; this reversibility permits reprocessing but limits load-bearing service to temperatures below the endblock softening range. Continuous load-bearing applications should be restricted to service temperatures below 70 °C to 80 °C unless the compound is crosslinked or blended with a higher-heat-distortion resin. Because YH-507 is linear, its zero-shear viscosity is lower than that of radial or star-branched SEBS of comparable molecular weight. In large-scale twin-screw compounding, motor torque is less likely to be the limiting factor than feeder drag and screw fill at high output.

What Limits Melt Blending, Pellet Stability, and Injection Moulding Throughput?

Compounding of YH-507 in a co-rotating twin-screw extruder with an L/D ratio of 40:1 to 52:1 is performed with barrel set points between 180 °C and 220 °C. The elastomer is shear thinning; apparent melt viscosity falls more steeply than a constant-viscosity model predicts as screw speed increases above 250 rpm. On production lines this behaviour lowers head pressure at high throughput, but it can also reduce the specific mechanical energy input required for filler and oil dispersion. Pellet strand temperature, not barrel set point, should be monitored at the strand die; strand temperatures above 240 °C promote oxidative discolouration and surface roughness.

Moisture control is an operational boundary. At relative humidity above 60%, packages opened for more than 2 h should be dried in a desiccant bed or vacuum dryer at 70 °C to 80 °C for 2 h to 3 h. Moisture is not a hydrolytic degradation catalyst for SEBS, but it produces surface splay, gate blush, and nozzle drool during injection moulding. Thermal degradation in YH-507 occurs primarily through chain scission in the ethylene/butylene mid-block and oxidative discolouration of polystyrene end blocks above 250 °C. At barrel residence times above 8 min, discolouration can occur even at 230 °C.

Injection moulding of YH-507-based compounds requires attention to gate geometry and injection velocity. Thin-wall parts with flow length-to-wall thickness ratios above 150:1 typically demand injection pressures up to 90 MPa and mould temperatures from 30 °C to 60 °C. High injection velocity above 60 cm³/s through small gates can induce melt slip and jetting; reducing velocity to 30 cm³/s to 45 cm³/s and increasing nozzle temperature to 220 °C usually suppresses the defect. Because the saturated mid-block cannot undergo accelerated sulfur vulcanization, standard sulfur cure systems used in SBS/NR or SBR compounds are ineffective. Peroxide crosslinking is possible through hydrogen abstraction from the ethylene/butylene segment, but the scorch window in SEBS/polypropylene thermoplastic vulcanizate formulations is narrow. Co-agent trimethylolpropane trimethacrylate at 0.5 phr to 2 phr with dicumyl peroxide can be used to raise compression set resistance, although polypropylene degradation must be managed by using low-peroxide dosing and stabiliser packages.

For polyolefin modification, YH-507 is incorporated into polypropylene and polyethylene compounds at 5 wt% to 25 wt%. In polypropylene homopolymer, the dispersed elastomer phase increases notched impact resistance and reduces low-temperature embrittlement, but it also lowers tensile modulus and heat distortion temperature. Phase inversion and severe melt viscosity rise typically occur when elastomer loading exceeds approximately 35 wt% in a neat homopolymer matrix; compounds in that region require processing aids and lower injection speeds. Automotive interior compounds often use 15 wt% to 25 wt% YH-507 with coupled-PP base resin, talc, and colour masterbatch. Grain reproduction in grained surfaces is more sensitive to mould temperature and pack pressure than to the SEBS grade; mould temperatures at the upper end of 30 °C to 60 °C improve replication but extend cycle time.

Soft-touch TPE compounds based on YH-507 typically contain polypropylene as the semicrystalline phase and paraffinic oil as the rheology modifier. The ratio of SEBS to oil controls hardness and compression set; a 50:50 elastomer-to-oil ratio can produce Shore A hardness near 40, whereas a 65:35 ratio can remain near 55 Shore A. The linear polypropylene phase may be added at 20 phr to 60 phr to improve mechanical strength and processability, but excessive polypropylene raises hardness and reduces rubbery character. At oil loadings above 80 phr in a single-pass mixing cycle, compression set rises rapidly and surface tack appears; this is a processing cliff-edge because the phase morphology shifts from continuous elastomer to oil-swollen network. Additive packages for SEBS compounds typically include primary hindered phenol antioxidants at 0.1 wt% to 0.3 wt% and phosphite process stabilisers at 0.1 wt% to 0.25 wt%. The saturated mid-block requires lower antidegradant loading than SBS, but the polypropylene phase in TPE compounds still requires stabilisation.

When Asphalt Modification Requires Saturated Mid-Block Ageing Resistance

In polymer-modified bitumen, YH-507 is evaluated when hot storage stability and oxidative ageing resistance are more important than low-temperature elastic recovery. The saturated mid-block disperses more slowly in bitumen than unsaturated SBS; high-shear milling at 180 °C to 190 °C is usually required, and pre-swelling with aromatic process oil can shorten dispersion time. The absence of main-chain unsaturation reduces gel formation during prolonged storage at transport temperatures. Modification levels from 4 wt% to 8 wt% by mass of bitumen are typical in waterproofing membranes and paving binder trials. Heat ageing data for SEBS-modified binders generally show lower carbonyl formation than SBS-modified binders under the same oxygen exposure; however, the saturated polymer is less shear-responsive at low temperature and may not match high-vinyl SBS in elastic recovery. Storage stability of SEBS-modified bitumen can be inferior to SBS if density mismatch and phase separation are not controlled. Compatibilisers or aromatic-rich extended oils are often used; without them, the polymer phase can settle during 48 h to 72 h hot storage.

Adhesive and sealant formulations use YH-507 for its saturated mid-block and lower solution viscosity. In toluene or cyclohexane/2-butanone blends, solids contents of 20 wt% to 25 wt% are achievable with low gel content. Tackified pressure-sensitive adhesives combine the polymer with hydrogenated tackifiers and paraffinic oils; end-block compatibility governs cohesive strength, and mid-block solvency controls pressure-sensitive tack and oil bleed. In hot-melt adhesives, the absence of unsaturation permits processing at 170 °C to 190 °C without rapid viscosity drift. On slot-die coating lines, viscosity at application temperature determines web penetration; adding process oil or low-molecular-weight tackifier lowers viscosity, while raising SEBS content increases cohesive strength. For flame-retardant wire and cable formulations, the grade serves as an elastomeric modifier in halogen-free compounds. Alumina trihydrate or magnesium hydroxide loadings above 50 wt% reduce tensile strength, so a higher-hardness YH-507 compound or a peroxide-modified variant may be required. Published data for this specific configuration in conduit systems is limited.

Regulatory and handling boundaries for YH-507 compounds are established at the finished-article level. The neat polymer is typically assessed against REACH Regulation (EC) No 1907/2006 and RoHS Directive 2011/65/EU; food-contact status, when required, is evaluated on the final compound under the relevant migration test, such as FDA 21 CFR 177.2600 for rubber articles or the EU Plastics Regulation 10/2011/EU where applicable. Medical device use requires ISO 10993 biological evaluation on the finished component; no statement of universal medical-grade status should be inferred from the base resin. The material is combustible and should be stored away from ignition sources. Strong oxidising acids, high-pressure oxygen, and prolonged ozone attack under stress should be avoided. Halogenated solvents used for cleaning should be removed before melt processing because residual solvent can cause bubble formation and surface defects.

Differentiation from Unsaturated SBS and Other Baling SEBS Grades

YH-507 differs from unsaturated SBS grades primarily in mid-block saturation. Under accelerated ageing in air at 100 °C, SBS compounds of equivalent hardness tend to harden and lose elongation earlier than SEBS compounds because the butadiene segment reacts with oxygen and ozone. YH-507 is therefore specified for outdoor seals, gaskets, and under-hood parts where unsaturated SBS would require heavy antidegradant loading. Within the Baling SEBS family, YH-507 is a lower-solution-viscosity grade than high-molecular-weight film and extrusion grades. Its melt flow rate in the 3 g/10 min to 10 g/10 min range places it in the higher-flow region among neat SEBS products, making it suitable for multi-cavity injection moulds and thin-wall parts. The trade-off is lower melt strength in extrusion blow moulding, profile calendering, and sheet extrusion.

Compared with oil-extended SEBS products, YH-507 is supplied without process oil. This permits formulator control over hardness, compression set, and oil migration. Addition of paraffinic or naphthenic oil at 30 phr to 80 phr lowers hardness to the 30 Shore A to 50 Shore A range, but high oil loadings above 80 phr in a single-pass mixing cycle can produce surface migration and pellet tack. Compared with maleic anhydride-grafted SEBS, YH-507 is unfunctionalised. Adhesion to polyamide, PET, or metal surfaces requires a separate functionalised tie layer, reactive compounding, or substrate surface treatment.