The hydrogenated styrene–butadiene block copolymer Asahi Kasei Tuftec™ H1041G is a pelletized SEBS for melt compounding, polymer modification, injection moulding, and elastomeric film extrusion. The product contains a polystyrene endblock content of 30 wt% and a saturated ethylene-butylene midblock, which removes backbone unsaturation and thereby improves resistance to thermo-oxidative degradation relative to unhydrogenated styrene–butadiene–styrene triblock copolymers. Representative values from manufacturer data sheets include a melt flow rate of 5 g/10 min at 230 °C/2.16 kg when measured according to ISO 1133-1:2022, density of 0.91 g/cm³ according to ISO 1183-1:2019, Shore A hardness of 67 according to ISO 7619-1:2018, tensile strength of 30 MPa according to ISO 37:2017, elongation at break of 600% according to ISO 37:2017, and tear strength of 35 kN/m according to ISO 34-1:2015. The melting range is not discrete because the midblock is amorphous, but the polystyrene domains soften at approximately 90–110 °C and phase mixing accelerates above 160 °C.

Compounding of H1041G with paraffinic process oil reduces hardness and modifies melt viscosity. At oil loadings of 30–80 phr, Shore A hardness falls to 30–45, tensile strength declines to 5–12 MPa, and elongation at break may remain above 500% when mixed on a co-rotating twin-screw extruder. Below 30 Shore A, the compound can become tacky and pelletization may require anti-blocking agents or blending with a higher-styrene block copolymer. In comparison with higher-styrene SEBS grades, H1041G has fewer polystyrene endblock associations, resulting in a lower rubbery plateau modulus and lower melt viscosity at equivalent temperature. The grade is therefore selected for low-hardness and high-elongation compounds rather than for high-modulus structural parts.

What Processing Characteristics Distinguish H1041G During Twin-Screw Compounding?

Twin-screw compounding of H1041G has been reported on co-rotating extruders with L/D ratios of 40:1 to 52:1 and specific torque above 7 Nm/cm³. The amorphous midblock softens without a crystalline melting plateau; barrel temperatures from 160 °C to 190 °C are sufficient for early plastication. When formulations contain mineral oil, oil injection is normally positioned after the first mixing zone, at barrel 5–7 of a 12-barrel configuration, to reduce screw slip. Processing with oil injection in the feed throat has been associated with throughput fluctuations of 5–10% and reduced melt pressure on commercial lines. The melt temperature at the die is commonly held between 200 °C and 220 °C; short residence times up to 8 min at temperatures up to 260 °C are tolerated, but prolonged hold-up oxidatively degrades the saturated midblock and shifts the melt flow rate upward.

Pre-drying is not normally required because the polymer absorbs less than 0.05 wt% moisture; however, pellets stored at relative humidity above 60% can carry surface water and are dried at 70–80 °C for 2–4 h before processing in closed hoppers. Venting with an atmospheric port between the plasticizing and metering zones reduces volatiles from low-viscosity oils. Fine fillers above 25 wt% may require forced side-feeding to prevent hopper bridging. Melt filtration through screen packs of 60–120 mesh is used in strand pelletizing to remove agglomerates; pressure drop across the screen pack increases with filler loading above 40 wt%. Melt pumps stabilize die pressure to ±0.5 MPa when low-viscosity oils are present.

In polypropylene impact modification, H1041G is melt-blended at addition levels of 15–30 wt% using a co-rotating twin-screw extruder with underwater pelletizing. The dispersed SEBS domains improve notched Izod impact strength measured at 23 °C according to ISO 180:2019; unmodified polypropylene homo-polymer typically fractures below 4 kJ/m², while H1041G-modified compounds can reach 8–15 kJ/m² depending on PP melt flow rate and screw intensity. At loadings above 30 wt%, tensile creep modulus measured at 1 h under ISO 899-1:2003 may fall below 600 MPa. The lower styrene content of H1041G delays co-continuous phase inversion relative to high-styrene SEBS, allowing toughness development at lower rubber content.

Elastomeric film lines running H1041G compounds use cast-film dies with lip gaps of 0.5–1.5 mm and chill-roll temperatures of 20–35 °C. At 30–70 phr oil loadings, the melt strength is sufficient for film thicknesses above 100 µm, but edge tear and draw resonance can occur at line speeds above 30 m/min when the compound melt index exceeds 30 g/10 min. Film tensile properties after stretching are evaluated under ISO 527-3:2018; typical machine-direction elongation exceeds 400%, while transverse-direction tear strength is influenced by die orientation and polypropylene content. Published data for this specific H1041G film configuration is limited, so pilot-scale trials on a 300 mm cast-film line are recommended before commercial runs.

Migration Resistance and Regulatory Compliance for Skin-Contact Articles

The saturated midblock of H1041G reduces solvent extractables relative to unhydrogenated SBS in polar media, but oil-extended compounds still release aliphatic hydrocarbon migration products. Extraction testing of neat polymer plaque in hexane according to ISO 6427:2013 can show extractables below 5 wt%, whereas oil-extended formulations may exceed 20 wt%. For skin-contact articles, the finished compound is evaluated under ISO 10993-5:2009 for in vitro cytotoxicity and ISO 10993-10:2013 for irritation when intended for prolonged contact; these data are formulation-dependent and are not supplied by the base-polymer grade alone. The unmodified polymer may be considered for food-contact use under 21 CFR 177.1810 when finished-article migration testing complies with the applicable end-use restrictions. REACH SVHC screening and RoHS Directive 2011/65/EU heavy metal limits are assessed on the final component rather than on the pellet.

In sealing applications, compression set is measured according to ISO 815-1:2019 at 70 °C; oil-free H1041G plaques can show compression set above 50% after 22 h, whereas blends with polypropylene at 20–30 wt% may reduce set to 30–45%. High-temperature service above 120 °C requires additional primary antioxidants because the saturated midblock can undergo chain scission despite the absence of main-chain double bonds. When used in contact with copper or other transition metals, metal deactivators may be necessary to prevent catalytic oxidative degradation.

When H1041G Replaces Non-Hydrogenated SBS in Durable Soft-Touch Applications

Substitution of H1041G for an SBS grade in a 50 Shore A soft-touch compound alters both thermal stability and tensile-strength balance. Unhydrogenated SBS compounds at this hardness may exhibit tensile strengths above 20 MPa, whereas the corresponding oil-extended H1041G compound often falls to 8–15 MPa unless polypropylene content is increased. The trade-off is greater resistance to ultraviolet-induced chain scission; after 500 h of QUV exposure under ASTM D4329-21 cycle A, the hydrogenated grade retains a higher fraction of elongation at break than an unhydrogenated SBS reference, although published data for this specific configuration is limited. Processors may raise melt temperature by 30–40 °C without gel formation, which reduces torque and permits higher screw speeds.

Differences from other Tuftec grades are most evident in dynamic mechanical analysis. Higher-styrene Tuftec grades display a higher rubbery plateau modulus between 25 °C and 80 °C and require more plasticization to reach the same hardness; lower-flow grades show higher melt viscosity and are less suited to thin-wall injection moulding. H1041G therefore occupies a mid-flow, low-hardness position in the product line, with pellet integrity retained at moderate oil loading. Dynamic mechanical analysis of the neat polymer typically shows a midblock glass transition at approximately −50 °C and a polystyrene domain transition near 100 °C. This low midblock transition contributes to low-temperature flexibility; notched Izod impact at −30 °C in polypropylene compounds can remain above 6 kJ/m² when the blend contains 20 wt% H1041G.

In adhesive and sealant formulations, H1041G is used as a polymer base when the adhesive requires plasticizer tolerance and shear holding power at temperatures below 60 °C. Hot-melt viscosity at 180 °C is typically below 20,000 mPa·s for the neat polymer, allowing application by slot-die coaters. Toluene solutions at 20–40 wt% solids can be applied to nonwoven substrates; residual solvent is removed below 100 °C to avoid substrate distortion. Peel adhesion values depend on substrate surface energy and surface preparation and are not controlled by the base polymer alone. The saturated midblock is compatible with paraffinic and naphthenic process oils, polyolefin elastomers, and low-density polyethylene. Aromatic oils are not recommended because they preferentially solvate the polystyrene domains, reducing hardness and creep resistance. Phthalate plasticizers are generally not required and can exude at loadings above 30 phr. Fatty-acid amides and metallic stearates can be used as internal and external lubricants at levels up to 0.5 wt%; higher loadings may deposit on mould surfaces.

Injection moulding of H1041G-based compounds on machines with clamp force above 80 t uses nozzle temperatures of 190–230 °C, injection pressures of 40–70 MPa, and mould temperatures of 20–50 °C. The base polymer flow allows thin-wall filling, but excessive injection speed can create jetting and weld-line surface defects when polypropylene is present. Mould release is improved with 0.2–0.5 wt% erucamide or silicone masterbatch; however, slip additives above 0.5 wt% reduce paint adhesion in cross-cut testing under ISO 2409:2013. The material should not be processed in direct contact with ketones, aromatic hydrocarbons, or chlorinated solvents because these dissolve or swell the polystyrene domains.