Dynasol Calprene® SEBS CH6120 PH is a linear styrene-ethylene/butylene-styrene triblock copolymer produced by the selective hydrogenation of a styrene-butadiene-styrene precursor. The CH6120 designation identifies the non-oil-extended SEBS grade, while the PH suffix specifies the powder presentation used where rapid solution dissolution, dry blending with polypropylene, or high-surface-area mixing is required. The saturated ethylene/butylene midblock distinguishes the product from unhydrogenated SBS block copolymers; the absence of in-chain carbon–carbon double bonds is the primary structural feature that raises thermal-oxidative stability and reduces ultraviolet-initiated chain scission. In the unfilled state, manufacturer-published datasheets place the bound styrene content at 30 wt% (ASTM D5775), specific gravity at 0.91 (ASTM D792), and Shore A hardness between 65 and 70 (ASTM D2240). Tensile properties reported for compression-molded plaques include tensile strength in the range of 25–35 MPa and elongation at break in the range of 500–600% (ASTM D412). The powder form is controlled for particle size distribution and bulk density to reduce feed segregation in continuous compounding; published data for the exact particle size envelope of this specific PH powder configuration is limited and should be confirmed against the current certificate of analysis.

What Distinguishes CH6120 PH from Pelletized H6120 and Higher-Melt-Flow SEBS Grades?

Within the linear SEBS product family, CH6120 PH occupies the medium-flow region. In comparison with pelletized H6120, the PH powder alters feeding behavior rather than molecular architecture. The powder morphology supports lower energy input in dry-blend dispersion but requires enclosed conveying or side stuffing to avoid dust formation. Against higher-flow grades such as H6140, CH6120 PH provides higher elastic recovery and better tensile retention at elevated temperature. The difference arises from the higher molecular weight tail, which increases solution viscosity and lowers melt mass-flow rate. Conversely, compared with high-molecular-weight H6170, CH6120 PH enters the melt state at lower torque; this is an advantage when combination with polypropylene in a corotating twin-screw extruder with L/D 40:1 at barrel temperatures between 200 °C and 230 °C is required. The styrene hard-block content difference of 30 wt% versus approximately 33 wt% for H6170 shifts the rubbery plateau modulus downward and reduces the hardness of an unfilled compound by approximately 4–7 Shore A units after identical compression molding.

The following representative values are drawn from manufacturer-published technical data for linear SEBS CH6120 and are applicable to the unfilled polymer. Values obtained in compounds will depend on oil type, filler content, and mixing history.

Melt Processing Boundaries on Twin-Screw and Injection Molding Equipment

On a corotating twin-screw extruder with L/D 40:1 and a barrel profile of 180–220 °C, the powder grade disperses into polypropylene at addition levels of 20–40 wt%. If the melt temperature exceeds 250 °C for more than 90 s, the ethylene/butylene midblock begins oxidative chain scission; torque drops more than 15% and tensile strength of molded plaques falls below 20 MPa. To avoid this, barrel temperature above 230 °C should be limited to the final two zones. Vacuum venting at -0.08 MPa gauge removes volatiles and reduces splay. In injection molding, barrel temperatures of 190–220 °C are usable; mold temperatures from 20 °C to 50 °C produce adequate surface gloss; clamp force of 4–8 kN/cm² projected area is typical for high-flow compounds. For compression molding, platen temperatures of 190–230 °C at 5–10 MPa for 8–12 min provide void-free sheets up to 6 mm. Mineral oil is preferred for mold release; silicone-based release agents should be avoided if post-molding adhesion or painting is required.

Compounds based on CH6120 PH are used in soft-touch grips, medical tubing, gaskets, footwear, and polypropylene impact modification. In thermoplastic elastomers, paraffinic white oil addition of 30–100 phr lowers Shore A hardness from approximately 65 to 20–40; compounds for medical tubing typically use 50–80 phr paraffinic oil and 10–20 wt% polypropylene to shift tensile strength to 8–15 MPa and elongation to 600–800%. The saturated midblock allows service temperature up to 100 °C in low-load applications, but continuous exposure above 120 °C in air should be avoided because antioxidant depletion accelerates after 500 h under ISO 188. In polypropylene impact modification, addition of 10–20 wt% improves notched Izod at -30 °C by 4–8 kJ/m² relative to unmodified polypropylene when tested under ISO 180/A. For adhesive formulations, the powder form permits dissolution in aliphatic or hydrogenated solvent systems to reach solids content of 20–40% with shorter mixing cycles than pelletized equivalents.

If the Powder Form Is Used in High-Humidity Compounding Facilities

In facilities where ambient relative humidity exceeds 60%, the powder’s larger surface area accelerates moisture adsorption relative to pelletized H6120. Uncontrolled moisture produces surface porosity and lowers tensile strength by 5–10% in sheet extrusion. A dehumidifying hopper at 70 °C for 2–4 h is recommended; the dried powder should be conveyed under nitrogen to prevent rehydration. The powder also segregates if stored at bulk depth greater than 5 m; the manufacturer’s bulk density range of 0.35–0.55 g/cm³ causes variable feed rates at screw speeds above 200 rpm if gravimetric feeders are not fitted with agitation. Loss-in-weight feeders with vertical agitator blades and closed venting maintain feed stability better than single-auger volumetric feeders in production-scale compounding lines.

Compared with unhydrogenated SBS, CH6120 PH sacrifices some room-temperature hysteresis and tear strength but gains a wider thermal window. In ASTM G154 Cycle 1 fluorescent UV exposure, SBS compounds typically show visible surface cracking and greater than 50% loss of elongation after 500 h, whereas SEBS compounds retain more than 80% of elongation under the same conditions. This makes CH6120 PH suitable for exterior applications requiring 1000 h xenon arc exposure per ISO 4892-2. The trade-off is lower compatibility with unsaturated rubber; blends with natural rubber or SBR require compatibilizers or are not recommended above 10 wt% SEBS in high-elongation vulcanizates. Contact with aromatic oils, chlorinated solvents, and strong mineral acids should be avoided because swelling and tensile loss exceed 20% after prolonged immersion.

Compliance of the finished article must be established by the converter. The base polymer is typically evaluated within the following framework:

For lot-specific molecular weight, solution viscosity, and powder particle-size data, the current certificate of analysis and the manufacturer’s technical service group should be consulted, particularly when the PH powder is substituted into an existing pellet-based formulation.