SINOPEC Baling SEP YH-4020 is a hydrogenated styrenic block copolymer with a saturated ethylene/propylene mid-block and styrenic end blocks. The grade is positioned for low-hardness elastomeric compounds, transparent oil gels, sealants, adhesive systems, and polymer modification. Unlike SBS or SIS grades, the saturated mid-block contains no polybutadiene or polyisoprene double bonds, shifting oxidative and UV degradation mechanisms away from unsaturation-driven crosslinking. Producer literature identifies YH-4020 as a lower-styrene, lower-Shore-A material within the Baling SEPS range, but lot-specific melt flow, styrene mass fraction, and hydrogenation catalyst residue should be confirmed against the certificate of analysis before compounding.

What Specification Ranges and Test Methods Apply to YH-4020?

The values in the following table are representative producer data and are not batch-release limits. They are supplied here for initial grade screening and should be verified with the manufacturer’s certificate of analysis for each lot.

Typical values do not establish food-contact or medical-device compliance. For regulated end uses, migration behavior should be evaluated under EU 10/2011 or US FDA 21 CFR 177.1810 where applicable. Extractable oligomers from hydrogenated styrenic block copolymers depend on polymerization stopping agents, antioxidant package, and processing stabilizers. When the final article falls under ISO 10993, the complete formulation must be tested rather than the base resin alone.

When YH-4020 Is Compounded on a Twin-Screw Line

Feeding behavior on 30 mm to 65 mm co-rotating twin-screw extruders with L/D 40 to 52 is sensitive to pellet bulk density and surface moisture. At ambient relative humidity above 60%, pre-drying at 70–80 °C for 2–4 h is recommended before closed gravimetric feeding, because steam generated at the vacuum vent can destabilize melt temperature by 2–4 °C. Barrel set points from feed to die are commonly 160 °C to 210 °C; melt temperature should remain below 230 °C to limit chain scission. Throat bridging is reduced when pellets remain below 40 °C and the feed zone uses deep-channel conveying elements with 1.5 D to 2.0 D pitch.

Dispersive mixing of mineral fillers into YH-4020 requires lower specific energy than high-styrene SEBS because the random ethylene/propylene mid-block has lower melt elasticity. On 40 L/D machines, kneading blocks should be placed after the polymer melting zone, and specific energy input should not exceed 0.25 kWh/kg unless oil is present. Gravimetric feeder validation is necessary because a 5–10% shift in melt flow rate can alter starve-fed torque and melt temperature independently of barrel settings.

Oil-extended compounds are best produced by a two-stage masterbatch process. A first masterbatch at approximately 30 wt% oil reduces subsequent let-down torque instability. Direct oil injection at the main feed throat can cause screw slip; downstream injection after the first kneading zone, at 7 D to 9 D from the feed barrel, is preferred. Vacuum vent pressure between -0.08 MPa and -0.095 MPa assists volatile removal. Melt filtration through 100 mesh screens is recommended for film and medical compounds to remove agglomerates; screen-pressure buildup is generally lower than for high-styrene SEBS grades because of limited gel content.

Thin elastic films are produced by cast extrusion or blown film, where the saturated ethylene/propylene mid-block yields fewer macro-gel defects than polybutadiene-containing SBS because saturated chains are less prone to melt-state crosslinking. On a 45 mm single-screw extruder with a 300 mm slot die, die temperatures of 200–215 °C and chill-roll temperatures of 15–25 °C are used to control blocking. Adding 5–15 phr of a hydrogenated hydrocarbon tackifier raises surface tack but reduces tensile elongation; ASTM D882 tensile testing and ASTM D624 tear testing should define the tackifier ceiling.

Adhesive, Sealant, and Oil Gel Formulation Boundaries

Solvent-based pressure-sensitive adhesives are typically prepared at 25–35 wt% solids in a 70/30 cyclohexane/methyl ethyl ketone blend. Hydrogenated hydrocarbon tackifiers at 30–50 phr maintain low yellowness; rosin esters increase adhesion to polar surfaces but plasticize the styrene domains and reduce elevated-temperature shear. Brookfield viscosity below 1500 mPa·s at 25 °C is desirable for bar coating; ASTM D1084 controls viscosity, while ASTM D3330/D6195 are used for peel and loop tack. Published data for this resin-tackifier combination is limited beyond laboratory formulations.

Oil gels use white mineral oil with kinematic viscosity of 40–100 mm²/s at 40 °C. YH-4020 is charged at 10–20 wt% into a heated sigma-blade mixer at 170–190 °C under nitrogen. Cone penetration by ISO 2137 and oil bleed after 24 h at 70 °C are used for release testing. Higher oil viscosity reduces bleed but increases mixing torque; compatibility limits should be confirmed by cloud point or DSC.

YH-4020-based soft compounds can be injection molded with melt temperatures of 200–220 °C and mold temperatures of 15–40 °C. Because the material is low-modulus, ejection requires draft angles of 0.5–1.0 mm and large-diameter ejector pins. Vent depths should not exceed 0.02 mm to avoid flash, and back pressure above 0.5 MPa can raise melt temperature by 3–6 °C; barrel set points must be reduced accordingly. Clamping force is compound-dependent but commonly falls at 2–4 tonnes/in² of projected area for soft TPS compounds.

In polypropylene toughening, YH-4020 is added at 5–20 wt% to improve impact resistance. The saturated ethylene/propylene mid-block has better thermo-oxidative resistance than SBS, allowing compounding temperatures up to 230 °C in polypropylene systems. Notched Izod figures under ISO 180/A should be used to optimize twin-screw screw speed between 200–400 rpm on 40 L/D machines; published data for this exact matrix is limited because reactor-grade PP crystallinity and impact-copolymer content strongly affect the observed toughness increment.

Comparative Differentiation Rests on Styrene Content and Mid-Block Crystallinity

Relative to YH-4010, YH-4020 has a lower styrene mass fraction and lower Shore A hardness. The lower aromatic phase fraction reduces tensile strength and modulus while improving conformability and tack. YH-4010 is therefore specified for higher-hardness molded goods, whereas YH-4020 is specified for soft transparent compounds and gels. Compared with ethylene/butylene-based SEBS grades such as YH-502, the ethylene/propylene random mid-block suppresses polyethylene-like crystallinity, so YH-4020 produces lower haze and lower room-temperature modulus but also lower tensile strength. The saturated mid-block gives equivalent ozone and UV resistance to SEBS and a substantial improvement over SBS and SIS; accelerated weathering should be conducted under ISO 4892-2 and ozone resistance under ISO 1431-1.

Medical or hygienic components should be sterilization-tested on the finished part. Gamma radiation above 25 kGy can increase melt flow rate through chain scission; ethylene oxide sterilization at 55 °C and 60% RH requires residual gas measurement by ISO 10993-7. Cytotoxicity and irritation tests under ISO 10993-5 and ISO 10993-10 are formulation-dependent because antioxidant packages, oil, and surface additives control biological response more than the base polymer. Extractable data for this specific grade under EU 10/2011 food simulants are limited and should be requested from the producer before commercialization.