LCY Chemical’s Globalprene® SEBS 9559 is a linear styrene-ethylene/butylene-styrene triblock copolymer supplied as a porous pellet or powder. The model designation identifies a non-oil-extended SEBS with a controlled styrene/rubber ratio and molecular weight distribution for compounding, polyolefin modification, and elastomeric adhesives. The saturated ethylene/butylene midblock differentiates 9559 from SBS by removing main-chain unsaturation; residual unsaturation in the midblock is typically low enough that thermo-oxidative and ozone-driven chain scission proceed more slowly than in unsaturated SBS grades. The polystyrene domains undergo glass transition near 95 °C, while the EB continuous phase retains segmental mobility below −40 °C. These domains are not covalently crosslinked; they soften at processing temperature and reform upon cooling, which permits recycling of clean runner scrap in many formulations.

The grade is used in dry form and not oil-extended by the manufacturer. It accepts paraffinic white oils and polyolefin modifiers, but the addition of aromatic process oils or strong polar solvents can solvate the polystyrene domains and reduce the upper service temperature. Lot-specific certificates of analysis should be requested for exact melt index and styrene content; distributor data sheets compile typical values across several production campaigns rather than single-lot guarantees.

What Sets the 9559 Specification Apart from General-Purpose SEBS?

Publicly available datasheets for 9559 are less commonly distributed than those for 9551 and 9554. The table below is therefore a supplier-reported envelope rather than a certified lot release specification. The polymer architecture, saturated midblock, and controlled styrene content are more consistent identifiers of the grade than any single melt-flow value.

Because the 9559 designation is a commercial grade rather than a standards-defined material, a formulator should not transfer a guaranteed value from another Globalprene grade to 9559. Melt-index behavior is particularly sensitive to production campaign, drying, and test conditions under 200 °C/5 kg versus 230 °C/2.16 kg.

On a co-rotating twin-screw extruder with 40 L/D and segmented kneading blocks, the practical processing window for 9559 is set by feed-intake behavior and melt temperature rather than by a narrow degradation threshold. Feed-throat temperatures above 45 °C can cause porous pellets to bridge in gravimetric feeders; when condensation is present, drying for 2 h at 70 °C before hopper loading is recommended. Barrel set points from the feed section to die are commonly 170–220 °C, but the die section is maintained below 230 °C. Melt temperature measured with an immersion thermocouple should not exceed 260 °C; above this temperature and with residence time above 120 s, gel formation can occur. Oil injection should follow the melt seal, typically after barrel 7 of 10, to prevent screw slip and vent flooding. Vacuum venting of −0.08 MPa gauge is applied before the final mixing zone to remove moisture and low-molecular-weight volatiles. If the screw configuration contains excessive kneading blocks after oil injection, local viscous heating can exceed the barrel set point by 15–25 °C and initiate gel specks. The same constraint applies to hot-face pelletizing; die plate temperatures at or above 260 °C can cause strand breaks and off-spec fines.

When Polypropylene Modification Demands a Saturated Midblock

SEBS 9559 is compounded with PP homopolymer, random polypropylene, or impact copolymer to increase low-temperature impact while retaining exterior aging resistance. At 20–30 wt% addition to PP with an MFR of 25 g/10 min at 230 °C/2.16 kg per ASTM D1238-23, notched Izod impact at −20 °C per ASTM D256-23 can improve substantially, but flexural modulus measured by ASTM D790-17 declines with increasing SEBS content. The actual increase depends on SEBS domain size and the presence of a compatibilizer; without sufficient shear, large SEBS domains reduce impact efficiency. Injection molding should use a melt temperature of 200–230 °C and mold temperature of 30–60 °C. The SEBS phase remains saturated and does not introduce the same UV oxidation sites as unsaturated EPDM or SBS, but carbon black or hindered phenolic/phosphite stabilizer packages are still required for extended outdoor service. In thin-wall parts, the MFR of the PP/SEBS blend is often lower than the base PP; injection speed and packing pressure must be increased to avoid short shots and sink marks. Gate freeze time is controlled by the PP content and oil level; mold temperatures below 30 °C can cause surface delamination between PP-rich skin and SEBS-rich core.

For soft-touch overmolding onto PP, SEBS 9559 can be compounded to 40–70 Shore A with oil and polypropylene. Mold adhesion to PP is mechanical or diffusion-based; the surface temperature of the PP core above 120 °C at the time of overmolding improves melt bonding. In two-shot molding, the second barrel temperature is set 180–210 °C, and hard PP substrates should have a raised surface to create mechanical interlock if chemical adhesion is insufficient. In footwear and tool grips, the compound is injection molded with mold temperatures of 20–50 °C; gate freeze time is controlled by the PP content and oil level. Gloss and abrasion resistance are adjusted with styrenic or polyolefin resins, not by the base SEBS alone. Surface tack can appear at oil loadings above 120 phr; adding 10–25 phr PP reduces tack and improves compression set but increases hardness.

Sealant and Adhesive Systems With High Oil Loading

High oil-loading TPE formulations use 80–150 phr paraffinic white oil with kinematic viscosity at 40 °C of 60–120 mm²/s. At these levels, Shore A hardness falls below 40 and melt index increases, but tensile strength drops from the neat polymer range to 3–8 MPa depending on filler. Oil absorption on a 40 L/D extruder is improved by split injection; 60–70% of the oil is added after the polymer is melted and the remainder is added downstream before the final distributive mixing section. Higher oil levels can produce surface tack and compression set increases. For low-hardness TPE compounds, PP or other crystalline polyolefins are added at 10–25 phr to reduce tack and improve compression set but with a corresponding increase in hardness. Tack and peel adhesion to glass, aluminum, and polycarbonate are formulation-dependent; the unmodified polymer alone does not provide structural adhesion to polar substrates. If adhesion to polar substrates is required, a maleic anhydride–functionalized SEBS or a compatible tackifier resin must be considered because 9559 has no grafted polar functionality.

Selection Matrix Against Adjacent LCY SEBS Grades

9559 is positioned by melt flow and tensile response relative to adjacent LCY grades. The comparison is not a direct substitution statement because oil tolerance, filler acceptance, and thermal stability differ with formulation additives.

9552 is preferred for high-speed injection molding where lower melt viscosity is required and tensile demand is moderate. 9554 is selected when tensile strength and low creep are more important than ease of oil absorption. 9559 is specified for TPE compounds requiring a balance of oil tolerance, tensile retention, and processability; field results on 40 L/D compounding lines show lower motor torque than 9554 at the same screw speed and output, with accepting moderately lower tensile strength. The grade is not equivalent to maleated SEBS and should not be used as a direct tie-layer without functional group verification.

Flame-Retarded, Filled, and Outdoor Compounds Demand Stabilizer Rebalancing

Neat SEBS 9559 is combustible and is not UL 94 recognized as supplied. Flame resistance is generated by halogen-free mineral fillers such as magnesium hydroxide or aluminum trihydrate; adding these fillers at 50–65 wt% can raise compound density above 1.2 g/cm³ and reduce elongation to 100–250%. These changes must be evaluated for cable jacketing applications, where low-smoke halogen-free formulations are processed on tandem extruders. Outdoor compounds require hindered amine light stabilizers and UV absorbers; SEBS itself has better ozone resistance than SBS but still undergoes oxidative degradation if unstabilized. Avoid storage of pellets in hot, humid bays above 40 °C and 70% RH for more than 6 months without sealed liners; condensed moisture can produce surface defects in extruded profiles.

For medical device compounds, the base polymer is not a certification by itself. Formulations containing 9559 may be evaluated under ISO 10993-5 for cytotoxicity, ISO 10993-10 for skin irritation, and ISO 10993-11 for systemic toxicity after the finished device is defined. Radiation sterilization doses between 25 kGy and 50 kGy are commonly evaluated; post-sterilization tensile retention must be measured because aromatic polystyrene blocks can undergo crosslinking during irradiation and alter elongation. If food-contact status is required, the finished article must comply with FDA 21 CFR 177.1810 or the appropriate European Plastics Regulation 10/2011 migration limits; the supplier’s food-contact statement for the raw polymer does not automatically cover the compounded article. Compliance with REACH and RoHS is handled through the supplier’s product declaration; downstream formulators remain responsible for SVHC screening of additives, oils, and fillers.