LCY Chemical Globalprene® SEBS 9557D is a linear styrene-ethylene/butylene-styrene block copolymer produced by anionic polymerization followed by selective hydrogenation of the butadiene midblock. The terminal polystyrene blocks form physical crosslink sites that soften above the polystyrene glass transition temperature and re-form on cooling, giving thermoplastic processability without vulcanization. The saturated ethylene/butylene midblock reduces the oxidative and ultraviolet degradation channels present in unsaturated styrene-butadiene-styrene copolymers. The product is supplied as a pelletized base polymer with a non-staining stabilizer package. It is used in polypropylene modification, compounded thermoplastic elastomers, hot-melt adhesives, and soft-touch overmolding. The current certificate of analysis should be consulted for lot-specific properties.

What Are the Primary Specification Boundaries for 9557D?

The representative values in Table 1 are taken from the supplier’s published technical datasheet and are not specification limits. They are provided only for preliminary compounding calculations. Rheological and mechanical data are generated on compression-molded specimens under controlled laboratory conditions. Production compounds containing oils, fillers, tackifiers, or other polymers will deviate from the base polymer values.

The melt flow rate is measured at 230 °C with a 5 kg piston load. Both ASTM D1238 and ISO 1133-1:2022 are accepted for incoming quality control. The styrene content is controlled within a narrow manufacturing window, but the supplier’s certificate of analysis should be requested for the exact lot value. Published data for this specific configuration is limited to the supplier’s current technical datasheet and should not be extrapolated to formulated compounds without additional testing.

Melt Flow Positioning Versus Other Globalprene SEBS Grades

Within the LCY Globalprene SEBS family, 9557D is differentiated primarily by its melt flow and the absence of reactive functional groups. The grade is unfunctionalized; no maleic anhydride graft is present. Maleated SEBS grades are used when adhesion to polyamide, polyester, or metal surfaces is required. 9557D will not provide that interfacial adhesion and should not be used as a coupling agent in glass-reinforced polyamide. Its advantage is lower melt viscosity at comparable styrene content, which reduces fill pressure in injection molding and permits higher line speeds in profile extrusion.

Compared with unsaturated styrene-butadiene-styrene block copolymers, the saturated midblock of 9557D allows processing temperatures up to approximately 230 °C without the rapid chain scission observed in SBS. Sustained exposure above 240 °C is still not recommended. Branched SEBS grades may offer higher melt strength for foaming; 9557D has a linear structure that gives lower shear viscosity at high throughput. Direct commercial-grade comparisons are constrained because molecular weight distribution and block architecture are not fully disclosed in public datasheets.

In twin-screw compounding operations, pellets are typically dried at 80 °C for 2–4 h in a desiccant dryer with a dew point not above −40 °C when the storage relative humidity exceeds 60%. Co-rotating extruders with L/D 40 and atmospheric venting are used for oil-extended compounds; vacuum devolatilization is required when mineral oil is injected downstream. A typical barrel profile runs from 160 °C in the feed zone to 200–220 °C in the mixing zone, with melt thermocouples maintained below 240 °C. Stock temperatures above 240 °C for more than 90 s can produce gel particles by thermo-oxidative coupling followed by crosslinking. Kneading blocks with 30° forwarding angle are preferred over all-forward screw configurations to disperse the SEBS phase into polypropylene; all-forward screws can leave rubber domains large enough to reduce impact energy. Copper and copper alloys are incompatible in hot melt handling because copper ions catalyze thermo-oxidative degradation. Amine-based additives should be evaluated for color and odor generation in hot-melt systems before production.

Polypropylene toughening with 5–20 wt% 9557D is performed on twin-screw extruders by side-feeding the SEBS after the polypropylene melt reaches 190 °C. The notched Izod impact energy, measured per ASTM D256, depends on the base polypropylene melt flow rate, the SEBS molecular weight, and the number-average rubber particle diameter. A rubber particle diameter below 1 μm is generally needed to prevent brittle failure at −30 °C. This morphology is achieved only with sufficient shear and residence time. Batch-to-batch variation in the base polypropylene and in the SEBS melt flow rate will shift the ductile-to-brittle transition temperature, so incoming melt flow control per ISO 1133-1:2022 is recommended. Published data for this specific configuration is limited, and the impact improvement must be confirmed on the production-scale line.

When 9557D Is Compounded with Paraffinic Oil for Soft-Touch Molding

Injection-molding compounds based on 9557D are frequently oil-extended with white paraffinic oil. The oil must have a paraffinic carbon content above 40% and an aromatic content below 1% to minimize loss of tensile strength and surface tack. Naphthenic oils are less compatible with the ethylene/butylene midblock and can exude over time. Addition of oil lowers hardness and melt viscosity; the maximum oil loading is often limited by the required compression set resistance. Compression set, measured per ISO 815-1:2022, is used to define the upper service temperature. The Shore A hardness reduction per 10 phr oil is not linear, and published data for this specific configuration is limited.

Injection molding of oil-extended compounds is performed with barrel temperatures from 180 °C to 220 °C, mold temperatures from 20 °C to 40 °C, and injection speeds sufficient to prevent premature expansion of the physical crosslinks. Clamp force requirement is not determined by the SEBS alone but by the compound’s melt viscosity and gate design. For multi-cavity tools with flow length-to-thickness ratios above 150, melt temperatures at the upper end of the range may be required to prevent jetting and surface flow marks. Overmolding on polypropylene substrates does not require an additional adhesive because of the compatibility of the ethylene/butylene midblock with polypropylene. Adhesion peel strength can be evaluated by ASTM D903.

Hot-melt adhesive formulations are produced in sigma-blade mixers or continuous kneaders at 170–190 °C using hydrocarbon tackifiers and paraffinic oil. Because the midblock is saturated, colorless hydrocarbon tackifiers can replace rosin esters to reduce odor and lower initial color. Viscosity at 180 °C is controlled through the resin-to-oil ratio; formulations with higher polystyrene end-block content have higher cohesive strength and shorter open time. For sprayable adhesives, Brookfield viscosity per ASTM D3236 is often specified between 5,000 mPa·s and 50,000 mPa·s depending on the dispensing method. Peel adhesion per ASTM D903 shifts from cohesive to adhesive failure as the tackifier loading increases beyond the compatibility limit of the midblock. Dynamic mechanical analysis is used to detect a single-phase or phase-separated morphology in the compounded adhesive.

Calcium carbonate is used at 10–40 phr in cost-reduced compounds. It raises hardness and density while reducing tensile strength. The reduction in tensile strength measured per ISO 37 is approximately linear with filler volume fraction and depends on filler particle size and stearic acid surface treatment.

The ethylene/butylene midblock is readily swollen by aromatic solvents, chlorinated hydrocarbons, and strong polar solvents. 9557D is therefore not suitable for gaskets exposed to gasoline, toluene, or methyl ethyl ketone. Long-term service in hot air is generally limited to 100 °C under intermittent load. Continuous stress relaxation at temperatures above the polystyrene softening point leads to loss of physical crosslinks. UV resistance is improved over unsaturated SBS but is not indefinite; outdoor applications require carbon black or UV stabilizer packages. Weathering per ISO 4892-2:2013 should be used to qualify outdoor compounds.

Certification Status Under Food-Contact and Electrical Equipment Directives

Compliance claims for 9557D must be verified against the current supplier certificate for the specific finished formulation. For food-contact applications, styrene block copolymers may be used under FDA 21 CFR 177.1810, subject to the limitations and extractives requirements set out in the regulation. Under EU Regulation 10/2011, compliance depends on the additive package and overall migration limits; no blanket approval exists without end-use testing. For electrical and electronic equipment, the base polymer is typically offered as compliant with Directive 2011/65/EU on the restriction of hazardous substances, with no restricted substance intentionally added. Under REACH Regulation (EC) No 1907/2006, the supplier states that the SVHC content is below 0.1 wt% per article. Table 2 summarizes the matrix.

Each production lot should be evaluated against the actual certificate of analysis and regulatory certificate before use in food-contact or medical applications.