Kraton Japan Kraton™ D SBS D1101 JU is a linear styrene-butadiene-styrene block copolymer with a bound styrene content of 31% by mass and a specific gravity of 0.94. The polymer is classified as a thermoplastic elastomer based on a glassy polystyrene endblock domain and an elastomeric polybutadiene midblock, eliminating the need for vulcanization. The CAS registry number for the styrene-butadiene-styrene block copolymer class is 9003-55-8. The grade is targeted at high-cohesive-strength adhesive formulations, polymer-modified bitumen, and compounded thermoplastic elastomer articles where melt flow can be managed by shear or plasticization.

Physical Properties and Standard Test Designations

The combination of 31% styrene and a low diblock fraction yields a dense physical crosslink network. The tensile strength of 33 MPa and 880% elongation at break reflect a balance between cohesive strength and extensibility. The 2.8 MPa 300% modulus indicates a soft strain-stiffening response, while the Shore A hardness of 71 is typical for SBS grades used in flexible articles. The melt flow rate of 1.0 g/10 min under ASTM D1238 at 200 °C/5 kg places this product in the low-flow range of the Kraton D line, requiring higher process energy than grades such as D1102.

In the solid state, the polystyrene end blocks associate into discrete domains with a glass transition temperature near 90 °C. The polybutadiene midblock exhibits a glass transition near −90 °C. These values define the service window: low-temperature flexibility is limited by the butadiene phase, while upper service temperature under load is limited by softening of the styrene domains. The block architecture permits reprocessing above 150 °C, when polystyrene domains soften and the material flows, and re-forms physical crosslinks upon cooling.

On a co-rotating twin-screw extruder with an L/D ratio of 40:1, a barrel profile from 150 °C in the feed zone to 190 °C at the die is typical for dispersing D1101 JU into polystyrene, polyethylene, or polypropylene carriers. Screw speeds above 300 rpm are generally required for adequate dispersive mixing because the low melt flow rate limits distributive mixing. In injection molding, melt temperatures between 170 °C and 200 °C and mold temperatures between 20 °C and 50 °C are practical; thin-wall sections may require elevated injection pressures. Pre-compounding with naphthenic or paraffinic oil at 5–30 phr is a common method to reduce viscosity before final let-down. Direct feeding of high-viscosity D1101 JU into small injection-molding machines without plasticizing oil may lead to increased screw recovery time and short shots.

What Processing Constraints Arise from the Low Melt Flow Index?

The melt flow rate of 1.0 g/10 min is the central processing constraint. Under identical conditions, D1102 is typically reported at 6 g/10 min, making D1101 JU significantly more viscous. The difference produces higher melt pressure in single-screw extruders and requires either longer L/D barrels or higher screw torque. In strand pelletizing, die swell is lower than that of low-molecular-weight SBS, but strand tack can be reduced by cooling water at 20–40 °C. If melt temperature exceeds 230 °C, thermal-oxidative scission of the polybutadiene midblock accelerates; this reduces tensile strength and can increase gel content. A nitrogen blanket on the feed hopper and a hindered phenolic antioxidant masterbatch are standard practices. Moisture uptake is generally low; pre-drying is not routinely required unless condensation has occurred, but surface moisture should be removed above 60% relative humidity to avoid surface defects in extruded profiles.

Oil extension of D1101 JU alters the rheological balance. Addition of paraffinic or naphthenic oil at 5 phr lowers melt viscosity by a factor that depends on oil solvency; aromatic oils soften the polystyrene domains and reduce tensile strength more than paraffinic oils at equal loading. The practical upper limit for oil extension in many SBS compounds is around 30 phr for extrusion-grade flexible articles, beyond which Shore A hardness and tensile strength decline sharply. Mixing order matters: oil should be added after the polymer is fluxed, preferably through an injection port downstream of the feed throat, to avoid lubricating the solids-conveying zone and reducing throughput. On co-rotating twin-screw extruders, oil injection after 50–60% of the barrel length is common for SBS compounds.

When D1101 JU Replaces D1102 in Solvent-Borne Adhesive Formulations

Substituting D1101 JU for D1102 in toluene-based adhesives raises solution viscosity at equal solids. The solution viscosity of D1101 JU at 25% solids in toluene is approximately 4,000 mPa·s; the lower-molecular-weight D1102 gives a substantially lower value under the same conditions. To maintain roll-coating or slot-die coatability, solids must be reduced or the solvent blend adjusted with methylcyclohexane or ethyl acetate. The higher molecular weight of D1101 JU increases shear holding power and heat resistance in pressure-sensitive adhesives, but loop tack and room-temperature peel may decrease unless tackifier level is increased. Comparative testing should follow ASTM D3330 for peel adhesion, ASTM D6195 for loop tack, PSTC-107 for shear holding power, and ASTM D4498 for shear adhesion failure temperature, using tape samples prepared at 20 µm dry adhesive thickness on 50 µm polyester film.

In hot-melt pressure-sensitive adhesives, D1101 JU is generally used at lower concentration than D1102 because its higher melt viscosity raises application temperature. Typical hot-melt systems are run at 160–180 °C with slot-die coaters; above 200 °C, degradation of the polybutadiene midblock accelerates. The high molecular weight improves cohesion at 60 °C, but formulators must rebalance tackifier and oil levels to prevent loss of wet-out on low-energy substrates. When bonding to untreated polyethylene, surface treatment by corona discharge is often required regardless of SBS grade.

In solvent-based contact adhesives, D1101 JU provides higher cohesive strength than low-viscosity SBS but requires longer dissolution time. Mixing equipment with high-shear dispersers or sigma-blade mixers is typical. Solids contents of 15–25% are common; viscosity at 25% in toluene of 4,000 mPa·s is acceptable for brushing formulations but may be too high for spray application without dilution. The grade is compatible with hydrocarbon tackifiers, rosin esters, and selected C5/C9 resins; aromatic-modified resins may soften the styrene domains and reduce high-temperature strength. Open time, bond strength, and heat resistance should be evaluated using ASTM D6465 or ASTM D903 for adhesive bonds.

Polymer-modified bitumen production with D1101 JU requires high-shear milling because the low melt flow rate resists dispersion into bitumen at conventional mix temperatures. A rotor-stator mill operating at 3,000–5,000 rpm and a bitumen temperature of 175–185 °C is often used; mixing time is typically 60–90 min. The SBS phase swells in the maltene fraction while the polystyrene domains remain associated, raising the ring-and-ball softening point and improving low-temperature cracking resistance. Performance is evaluated under EN 14023 or ASTM D6373 for polymer-modified binders; storage stability is assessed by EN 13399. If the blend is held above 190 °C for extended periods, butadiene unsaturation may degrade, increasing separation and lowering elastic recovery.

Asphalt modification with D1101 JU is usually conducted in a two-stage process: pre-mixing at 160–170 °C in low-shear tanks, followed by high-shear milling and maturation. The polymer content is typically 3–6% by mass of binder. Higher loadings increase viscosity beyond pumpable limits unless crosslinking additives are used. The low melt flow of D1101 JU supports high-temperature rutting resistance but requires longer maturation than higher-MFR SBS grades.

Thermal Degradation Pathways in SBS Compounding Are Governed by Butadiene Unsaturation

Thermal-oxidative degradation of D1101 JU is initiated at the unsaturated polybutadiene midblock. Chain scission reduces molecular weight and tensile strength; crosslinking and gel formation raise melt filter pressure. In extrusion, a nitrogen blanket on the hopper and a barrel profile not exceeding 200–210 °C at the die are typical. Addition of 0.1–0.3% by mass of a hindered phenolic antioxidant, with or without a phosphite costabilizer, is common. The styrene end blocks are more thermally stable; their glass transition near 90 °C remains unchanged under normal processing. Degradation is evaluated by melt flow rate shift, yellowness index under ASTM E313, and gel content by filtration through a 325-mesh screen pack at 200 °C. If gel content exceeds a producer-defined limit, screen-pack pressure rises and output drops. Published data for this specific configuration is limited; therefore, process windows should be validated on the actual compounding line.

In footwear compound formulations, D1101 JU is used as the primary elastomer phase in blends with polystyrene or high-styrene resins. The low melt flow rate provides high tensile strength and abrasion resistance in unit soles, but cycle time in injection molding can be longer than with D1102. Typical compound formulations contain 20–40 phr of oil, 10–25 phr of polystyrene, and 0.5–1.0 phr of antioxidant, depending on hardness and flex fatigue targets. Flex fatigue is assessed under ASTM D1052; tensile properties are measured under ASTM D412. Microcellular soles may use chemical blowing agents at 0.5–2.0 phr, processed at 170–190 °C.

Incoming quality control for D1101 JU typically includes melt flow rate under ASTM D1238, bound styrene content by infrared spectrophotometry, solution viscosity in toluene, and gel content by pressure filtration. Lot-to-lot variation in melt flow rate can shift extrusion output and die pressure; therefore, formulators often blend multiple lots in silos to normalize viscosity. Pellet or crumb geometry affects feeding consistency on loss-in-weight feeders; crumb bridging in hoppers is managed with vibrating hopper bottoms. The low melt flow of this grade makes gel defects more visible in film and adhesive coating lines; filtration through 200–325-mesh screens is common.

In the United States, food-contact adhesive uses should be verified against 21 CFR 175.105; repeated-use rubber articles require confirmation against 21 CFR 177.2600. Under REACH, SBS polymers may be exempt from registration as polymers if the monomers are registered and the polymer meets the definition of a polymer under Article 3(5). The grade-specific SDS and regulatory datasheet remain controlling for substances of concern, residual monomers, and packaging restrictions. RoHS compliance applies at the finished article level, not to the raw polymer.

Compared with D1102, D1101 JU provides higher tensile strength and lower melt flow, making it suitable for high-strength compounds and adhesives but less suitable for high-speed injection molding of thin-wall articles. Compared with D1118, which contains a higher diblock fraction and is used in tackified pressure-sensitive formulations, D1101 JU yields a more cohesive, less tacky network. Reformulation may be required when switching between these grades because tackifier compatibility and oil loading differ. The product is not intended for applications requiring continuous service above 70 °C under load without crosslinking or reinforcement. In solvent systems, aromatic solvents that dissolve the polystyrene domains reduce cohesive strength; paraffinic or naphthenic solvents preserve the physical crosslink network. In polymer-modified bitumen, high-temperature storage above 190 °C should be minimized to limit degradation. Published data for this specific configuration is limited; therefore, grade-specific technical datasheets should be consulted before final formulation lock.