LCY Chemical Globalprene® SEBS 9645D is supplied as a linear styrene-ethylene/butylene-styrene triblock copolymer in pelletised form. The hydrogenated mid-block distinguishes it from unmodified styrene-butadiene-styrene block copolymers: saturation of the butadiene segment removes most main-chain unsaturation, which alters oxidative stability, ultraviolet resistance, and oil compatibility. The manufacturer’s published typical data for the neat grade list a styrene mass fraction of 32 %, a specific gravity of 0.91 g/cm³ according to ASTM D792, and a Shore A hardness of 65 after 10 s dwell according to ASTM D2240. The product is not oil-extended and contains no intentionally added plasticiser. Individual lot certificates remain the controlling specification for release purposes.

Mechanical screening of the neat polymer is performed on injection-moulded plaques because orientation and cooling history affect tensile response. Under ASTM D638-14, Type IV specimens cut from 2 mm plaques and pulled at 500 mm/min give a tensile strength at break of approximately 25 MPa and an elongation at break of approximately 500 %. Melt flow rate is measured under ISO 1133-1:2022 at 230 °C with 2.16 kg load. The material is strongly shear-thinning; apparent viscosity at 100 s⁻¹ and 200 °C is markedly lower than at 0.1 s⁻¹. This property reduces injection pressure in thin-wall tools but complicates profile extrusion die design.

The table summarises typical neat-polymer data; it does not constitute a batch release specification.

Does 9645D Require Pre-Drying Before Twin-Screw Compounding?

Moisture uptake of neat SEBS is lower than that of polyamide or polyester, but surface condensation on cold pellets transferred from outdoor silos can carry enough water to generate splay on injection-moulded parts and to reduce melt viscosity through hydrolytic degradation. A hopper dryer set at 70–80 °C with a dew point below -20 °C and residence time of 2–4 h is recommended when storage relative humidity exceeds 60 % RH or when pellet surface temperature at feed is below 10 °C. Target pellet moisture is below 0.05 %. On co-rotating twin-screw extruders with L/D 32:1 to 48:1, barrel temperatures are set in the range 180–230 °C. The feed zone is kept below 120 °C to prevent premature blocking of the first screw elements. A vacuum vent at -0.08 MPa gauge after the second kneading block removes residual moisture and oligomer volatiles. Melt temperature measured at the die should remain below 260 °C; above this threshold, oxidative chain scission accelerates and gel bodies may form in dead spots. Screw speeds above 600 rpm in a 40:1 L/D machine can raise melt temperature by 5–15 °C relative to the barrel set point; this effect is formulation-dependent and is more severe in high-viscosity, low-oil compounds. Die-head pressure above 180 bar is a practical indicator of screen pack blinding or insufficient melt temperature. A gear pump inlet pressure of 60–80 bar is a typical target for strand pelletising. The strand water bath should be held at 25–40 °C; water temperatures below 20 °C can chill the strand surface and produce transverse fracture during pellet cutting. Pellet quality is also influenced by die hole land length; a land length/diameter ratio between 4:1 and 8:1 is common for SEBS compounds to limit die swell and permit clean cutting.

Compounding practice with 9645D uses paraffinic or white mineral oils with kinematic viscosity of 40–100 cSt at 40 °C. Naphthenic oils are generally less compatible with the saturated ethylene/butylene mid-block and can exude at oil loadings above 20 wt%. Oil is injected after the first intensive mixing section so that pellet transport in the feed zone remains slip-free. Shore A hardness decreases as oil loading increases; additions of 10 wt%, 30 wt%, and 50 wt% typically produce hardness reductions of 10 points, 20–25 points, and 35–40 points, respectively. Polypropylene homopolymer at 10–30 wt% raises upper service temperature, improves chemical resistance, and reduces tack; copolymer PP improves impact at low temperature. Calcium carbonate filler above 20 wt% reduces tensile strength and increases specific gravity to 1.1–1.2 g/cm³; silane-treated fillers preserve elongation at break more effectively than untreated mineral powders. Organoclay and talc may be used in flame-retardant wire and cable formulations, but they require high-shear dispersion and a coupling agent to prevent water uptake and dielectric loss. Published data for specific formulation gradients in 9645D is limited; optimisation should be performed by design-of-experiment studies rather than by extrapolation from emulsion SBS compounds.

Within the Globalprene SEBS range, 9645D is positioned as a mid-flow general-purpose grade. Higher-flow grades such as 9552U reduce injection pressure for thin-wall parts but show lower cohesive strength and higher oil exudation sensitivity. Lower-flow grades such as 9550U provide higher tensile strength and lower compression set at 70 °C but require higher melt temperatures and slower cycling in injection moulding. Selection among these grades is driven by wall thickness, oil loading, and compression-set requirement rather than by hardness alone. Compared with EPDM, 9645D requires no sulphur or peroxide vulcanisation, reduces cycle time because scrap can be reground, and yields lower-density parts. The trade-off is a maximum continuous service temperature below crosslinked EPDM compounds; EPDM can be formulated for 150–175 °C continuous use while SEBS is generally restricted to 120 °C.

When SEBS 9645D Replaces SBS in Footwear Midsole Compounds

Substitution in footwear midsoles affects oil selection, stabiliser demand, processing temperature, and part performance. SBS tolerates aromatic or naphthenic process oils; SEBS 9645D requires paraffinic white oils to avoid surface exudation. Processing temperatures are raised by 20–40 °C relative to SBS, so the thermal stabiliser package must include a phenolic antioxidant and a phosphite secondary antioxidant; total stabiliser loading is typically below 0.5 wt%. In injection moulding, melt temperature should be 200–220 °C, high injection speeds are preferred to avoid premature freezing of the high-viscosity melt, and hold pressures are set between 40–70 MPa. Moulds designed for SBS may require larger gates or lower runner turbulence because SEBS die swell is higher and melt extensional viscosity is higher at low extension rates. The resulting midsole density is approximately 0.91 g/cm³ before filler addition, compared with 0.94 g/cm³ for a comparable SBS compound. Compressive set after 22 h at 70 °C according to ISO 815-1 is generally lower for SEBS 9645D than for SBS, supporting retention of midsole thickness. UV discolouration after 200 h in ISO 4892-2 cycle A2 is also lower because the saturated mid-block does not form conjugated enone chromophores. A formulation with 30 wt% paraffinic oil and 15 wt% polypropylene can retain tensile strength above 12 MPa and elongation at break above 400 %. Published data for this specific midsole configuration is limited; mould trials are required to balance cycle time, surface finish, and compression set.

Hot-melt adhesives based on 9645D use hydrogenated hydrocarbon tackifiers rather than rosin esters because the saturated mid-block gives lower solubility for polar tackifiers; tackifier loadings are typically 40–60 wt% of the total formulation. At 180 °C open-tank temperature, viscosity drift measured by ASTM D4499 can be held below 10 % over 8 h under a nitrogen blanket. Adhesive cohesive strength at 40 °C is controlled mainly by styrene content and endblock association; 9645D at 32 % styrene provides a mid-range balance. Softening point and open time are adjusted with wax type; Fischer-Tropsch waxes increase heat resistance but reduce hot tack. The neat polymer is not a pressure-sensitive adhesive; tackifier addition is required for pressure-sensitive tape applications. Equipment for hot-melt mixing includes vertical change-can mixers with high-torque sigma blades or horizontal twin-screw extruders with recirculation loops. Residual level of diblock species influences loop tack and cohesive strength: higher diblock content reduces viscosity and improves wetting but lowers high-temperature peel strength; low-diblock variants of 9645D are used where cohesive failure is the limiting performance mode.

Regulatory Status and Extractables Boundaries

LCY Chemical represents Globalprene SEBS 9645D as compliant with REACH registration, RoHS recast 2011/65/EU, and the SVHC candidate-list restrictions current at the date of the safety data sheet. The neat polymer does not contain phthalate plasticisers, bisphenol A, or heavy-metal heat stabilisers. These statements apply to the unmodified resin; compounders must verify the final formulation against RoHS and REACH Annex XVII because oils, fillers, colourants, and flame retardants change the regulatory profile. Food-contact status is not automatically granted under FDA 21 CFR 177.1810 or EU 10/2011; migration testing must be performed on the finished article under the intended time-temperature conditions. Medical device evaluation requires biocompatibility testing according to ISO 10993-5 and leachables characterisation according to ISO 10993-18 on the sterilised finished component; the neat resin alone cannot be cleared. Continuous load-bearing service should be limited to temperatures below 120 °C because the polystyrene end-block domains soften near 95–105 °C, leading to loss of elastic recovery. Sterilisation by gamma radiation above 25 kGy can shift molecular weight distribution and increase gel content; electron-beam processing can similarly alter colour and elongation. Users should request the LCY product stewardship summary before designing a regulated application.