Dynasol Group

Dynasol Group is a synthetic rubber and styrenic block copolymer supplier with production platforms in Spain, Mexico, and China. The product range includes solution-polymerized styrene-butadiene rubber (SSBR) under the Solprene trade name, high-cis and low-cis butadiene rubber (BR), styrene-butadiene-styrene block copolymers (SBS), hydrogenated styrenic block copolymers (SEBS and SEPS) under the Calprene trade name, and emulsion styrene-butadiene rubber (E-SBR) under the Emulprene trade name. Each grade is defined by bound styrene content, vinyl content, total diblock content, Mooney viscosity or melt flow, and stabilizer loading. Certificates of analysis report these values against methods that commonly include ISO 1133-1:2022 for melt flow rate, ISO 37 for tensile properties, ISO 868 for hardness, and ASTM D445 for solution viscosity in toluene. Manufacturing sites operate under ISO 9001:2015 and ISO 14001:2015 registered systems. Selection among the families depends on service temperature, oil compatibility, green strength, and whether the final part is vulcanized or thermoplastic.

What Distinguishes Solution-Polymerized SSBR from Emulsion SBR in Dynasol Grade Selection?

The distinction between solution and emulsion SBR is controlled by polymerization mechanism. Anionic solution polymerization in hydrocarbon solvent permits control of styrene distribution, vinyl content, and branching. Emulsion free-radical SBR contains soap residues, higher gel, and a broader molar mass distribution. In silica-filled tire tread compounds, SSBR with 20–35 wt% styrene and 20–50% vinyl content is selected because polar vinyl groups interact with precipitated silica after silanization. Dynamic mechanical analysis according to ASTM D6601 or ISO 4664-1 is used to measure loss tangent at 0°C and 60°C; wet grip and rolling resistance are optimized separately. Emulsion SBR remains lower in cost and may provide better tensile strength and tear at equal filler loading, but residual fatty acids can interfere with silane coupling and increase compound viscosity. Green strength of SSBR is often lower than E-SBR, a known handling limitation on open mills and in calendering. Published data for Dynasol-specific silica tread performance is limited; compound results depend on silica surface area, silane coupling agent, and mixing sequence.

Oil extension alters vulcanization kinetics by reducing the concentration of reactive double bonds per unit volume. In a rotorless curemeter according to ASTM D5289, an oil-extended SSBR tread compound at 160°C typically displays lower minimum torque and lower maximum torque than the oil-free equivalent, while scorch time and optimum cure time lengthen because curative diffusion is restricted by the oil phase. The shift is not universal; it depends on the accelerator package, silane coupling agent, and oil aromaticity. A deeper ram is required in a 1.0 L laboratory internal mixer with a fill factor of 0.70 when oil-loaded silica compounds are mixed, because wall slip and undispersed silica increase batch-to-batch variation. Addition of 2.5 wt% of a carbon black masterbatch modifies compound viscosity and electrical conductivity; volume resistivity is tracked by ASTM D257, and cure kinetics are confirmed by ASTM D5289. Published data for this specific configuration is limited; processors must generate a compound-specific cure curve before changing oil level.

On a 40:1 L/D co-rotating twin-screw extruder, SBS and SEBS compounds are run at barrel set temperatures of 170–200°C. For unsaturated SBS the die melt temperature is kept below 220°C; for SEBS the limit can be raised to 230°C, but residence time above 200°C should remain under 90 s to minimize chain scission. In high-shear dispersion of paraffinic oil into SEBS, the adiabatic temperature rise across kneading blocks must be controlled; a rise above 20°C indicates excessive shear heating. Pre-drying at 80°C for 2–4 h is required when pellet exposure has exceeded RH 60%, otherwise surface porosity develops in injection molded articles. Injection molding of soft SEBS grades uses a specific injection pressure of 80–100 MPa for a 2.0 mm wall thickness; clamp force is calculated from projected area and cavity pressure, not from material hardness alone. Nozzle shut-off should be positive, and decompression should be limited to prevent air entrapment in oil-extended grades. These parameters are observed in production-scale behavior on conventional hydraulic and electric injection molding machines; lot-to-lot viscosity differences require adjustment of back pressure and screw speed.

When Hydrogenated Mid-Block SEBS Replaces Unsaturated SBS in Exterior Components

Hydrogenation of the butadiene mid-block converts the polydiene segment to a poly(ethylene-co-butylene) or poly(ethylene-co-propylene) sequence. The residual double bond content in SEBS is typically below 2 mol%, measured by iodine value. This conversion increases continuous service temperature from approximately 70°C for SBS to 100–120°C for SEBS and eliminates ozone attack sites. In exterior components, unsaturated SBS grades require protective wax and antioxidant packages; SEBS grades are evaluated under ozone exposure according to DIN 53509 at 50 pphm and 40°C with minimal change in tensile strength. The penalty is rheological: SEBS has higher melt viscosity at equivalent styrene content, requires paraffinic oil rather than naphthenic or aromatic oil, and can exhibit higher compression set. Under ISO 815-1, a 70 Shore A SEBS compound may show compression set of 25–45% after 22 h at 70°C, depending on filler and oil loading. For repeated food-contact applications, select SEBS and SBS grades meet FDA 21 CFR 177.2600 when compounded with permitted ingredients; the specific grade must be confirmed against the current certificate of compliance.

In polymer-modified bitumen, SBS is introduced at 3–6 wt% by in-line high-shear mixing at 170–190°C. The modified binder is tested for softening point by ASTM D36, elastic recovery by ASTM D6084 or EN 13398, and low-temperature flexibility by EN 14023 methods. Processing above 200°C degrades the butadiene block and reduces storage stability. In hot-melt pressure-sensitive adhesives, SBS and SEBS are compounded with hydrogenated tackifiers and paraffinic or naphthenic oils. Loop tack is measured according to ASTM D6195 or PSTC-16; SEBS is selected for UV-stable clear adhesives, while SBS is lower in cost but has limited oxidative stability. In footwear, SBS grades with low diblock and high flow are used for direct injection molding; abrasion resistance is evaluated by DIN 53516. Injection-grade SBS typically requires melt flow index of 5–30 g/10 min at 190°C/5 kg, but actual values are lot-dependent and must be confirmed against the certificate of analysis.

Calprene H SEBS Property Envelope and Regulatory Compliance Matrix

These ranges are typical across the product families, not specifications for any individual lot. The certificate of analysis for a specific grade such as Solprene 411 or Calprene H6170 must control final acceptance. Solprene 411 is a radial SBS grade with a nominal styrene content near 30 wt%, used in footwear and asphalt modification. Calprene H6170 is a linear SEBS grade with a nominal styrene content near 33 wt% and a Shore A hardness in the 70–80 range; current datasheets should be consulted because values are adjusted for processability and stabilizer package.

Thermal Degradation Pathways in Unsaturated SBS Block Copolymers Above 200°C

Thermal degradation of unsaturated SBS proceeds by butadiene mid-block chain scission and crosslinking. Above 200°C, the butadiene segment undergoes isomerization and radical formation that change solution viscosity and gel content. Under air, oxidative scission begins below 150°C and generates carbonyl species that can be tracked by infrared spectroscopy. In melt processing, the onset of degradation is not always visible as color until carbonyl index rises. The practical consequence is that barrel set points must be held within a narrow processing window; sustained operation above 210°C in a screw extruder results in decreased solution viscosity and increased gel content. Gel fraction can be measured by ASTM D3616, and melt stability can be evaluated by repeated melt flow measurements according to ISO 1133-1:2022. Stabilizer depletion is a separate failure mode; hindered phenolic antioxidants protect the unsaturated mid-block during storage and compounding, but excessive polymer residence time at elevated temperature consumes the stabilizer package and accelerates subsequent aging. This is why SBS processing is constrained more tightly than SEBS processing, and why scrap regrind levels above 15–20 wt% in SBS compounds require additional antioxidant adjustment.

Compared with sulfur-cured EPDM, SEBS grades from Dynasol Group do not require vulcanization, which eliminates sulfur and accelerator systems and reduces cycle time in injection molding, but hot-oil and hot-air compression set are inferior to a well-formulated EPDM compound. Compared with thermoplastic polyurethane, SEBS has lower density and lower hardness without plasticizer, but lower tensile strength and abrasion resistance. Compared with emulsion SBR, solution SBR grades have lower gel content and better silica interaction but higher cost and lower green strength. Compared with other SBS suppliers, the primary differentiators are control of diblock content, vinyl content, and hydrogenation conversion; the diblock fraction influences tack, flow, and hysteresis but reduces mechanical strength. For sub-ambient impact modification of polystyrene or polyphenylene ether, low-molecular-weight SBS grades are selected; for clear UV-stable compounds, SEBS is used. Published comparative data for Dynasol-specific products in these applications should be verified against current datasheets.