TSRC Taipol® SEBS 6014 is a linear styrene-ethylene/butylene-styrene triblock copolymer with CAS 66070-58-4. Manufacturer-published typical-property ranges place the styrene mass fraction at 12–14 wt%, specific gravity at 0.90–0.92 (ASTM D792), Shore A hardness at 45–50 (ASTM D2240, 15 s indentation), and melt mass-flow rate at 20–25 g/10 min (230 °C, 2.16 kg, ISO 1133-1:2022). The product is used as a base polymer or modifier in oil-extended TPE compounds, hot-melt adhesives, sealants, breathable films, and overmoulded polyolefin components. The following tables list representative values, not lot acceptance limits; certificates of analysis govern batch release.

The saturation of the ethylene/butylene midblock differentiates 6014 from unhydrogenated SBS grades in durability terms. Outdoor weathering of coloured compounds is assessed with ISO 4892-2 or ASTM D4329 using xenon-arc or fluorescent UV exposure; SEBS typically shows slower yellowing and better elongation retention than SBS at equivalent antioxidant levels.

What Distinguishes Low-Styrene SEBS 6014 from High-Styrene SEBS Grades?

In SEBS triblock copolymers, the polystyrene end-blocks form discrete glassy domains that act as physical crosslinks. A styrene content of 12–14 wt% places 6014 in the low-styrene segment of the SEBS product range; high-styrene grades with 25–30 wt% styrene exhibit higher room-temperature modulus, higher tensile yield, lower melt flow, and greater resistance to stress relaxation at elevated temperature. The same distinction appears in hardness: 6014 typically measures 45–50 Shore A after 15 s per ASTM D2240, while a 30 wt% styrene grade can exceed 70 Shore A under the same conditions. Quantitative comparison of modulus and strength must be made with specimens prepared and tested under ISO 37; the lower styrene content also means the order-disorder transition temperature is lower, so 6014 can be processed at lower melt temperature but sacrifices load-bearing capacity above 60–70 °C unless compounded with polypropylene or endblock resin.

Compounding of 6014 into an oil-extended TPE is typically performed on a co-rotating twin-screw extruder with L/D ratio of 32:1 to 48:1 and screw diameter selected for the desired throughput. Polypropylene homopolymer with melt mass-flow rate of 20–40 g/10 min (230 °C, 2.16 kg) is dry-blended at 10–30 wt% and fed to the main throat. After the melt seal is formed, a paraffinic process oil with kinematic viscosity of 100–400 cSt at 40 °C is injected downstream at 50–120 phr; oil temperature during injection is commonly held at 60–80 °C. Calcium carbonate or talc at 20–80 phr is side-fed after oil dispersion to avoid binder displacement and filler compaction in the feed zone. This sequence prevents screw slippage and phase inversion, but lot-to-lot variation in melt flow of 6014 can shift the location of the melt seal; screw speed and downstream feed-point set points should be adjusted from certificate-of-analysis melt flow data. Tensile bars per ISO 37 and hardness plaques per ASTM D2240 are collected from each production campaign because filler dispersion and oil uptake are not captured by melt flow alone.

Plasticizer selection is narrow for 6014 compounds. Paraffinic white oil with aromatic carbon content below 5% and pour point below -20 °C is preferred; aromatic and naphthenic oils partition into or swell the polystyrene domains. The resulting hardness loss and tensile set increase can be evaluated after 72 h at 70 °C using ISO 37 and ASTM D2240.

Compounding Sequence, Oil Injection, and Twin-Screw Extruder Set-Up

In commercial compounding lines, the feed sequence has a stronger effect on pellet quality than the neat-polymer melt index. The polymer and polypropylene are starve-fed at the main throat. Oil injection is introduced only after the first kneading block; injection before the melt seal can wet the feed zone and cause conveying instability. For a 40:1 L/D extruder, a common temperature profile is 170–220 °C from feed throat to die, with die melt temperature maintained below 230 °C to limit oxidative chain scission. Screw speed is adjusted to a specific mechanical energy input that avoids excessive shear heating, and vacuum devolatilization is applied after oil addition to remove residual moisture and low-boiling oil fractions.

When High Ambient Humidity Threatens Surface Finish in Injection Moulding

Open storage of SEBS pellets in environments above 60% RH makes pre-drying necessary. A desiccant dryer with a dew point below -40 °C, set at 70–80 °C for 2–4 h, reduces free surface moisture below 0.1 wt%; hot-air hopper drying at the same temperature is acceptable for pre-compounded material but not for wet regrind. Injection moulding barrel temperatures from rear to nozzle are generally profiled at 180–230 °C, with the nozzle held at 200–230 °C. Mould temperature is usually controlled between 20 °C and 50 °C; for thin-wall parts with wall stock below 1 mm, higher melt temperatures and injection velocities are used to avoid premature freeze-off. Cavity pressure transducers are recommended during process development; packing pressure is held to maintain a cavity pressure above 30 MPa until gate freeze, while back pressure at screw recovery is maintained at 0.5–1.0 MPa to homogenize melt without excessive shear heating.

In overmoulding onto unmodified polypropylene, 6014 does not require primer under typical processing conditions. The melt interface forms by interdiffusion of the ethylene/butylene midblock and the amorphous regions of the PP substrate; interface temperature above 150 °C and packing pressure above 30 MPa are typically required. Adhesion is evaluated by ISO 8510-2 or ASTM D903; published data for adhesion of 6014 to talc-filled or glass-filled PP grades are limited, so application-specific peel testing is required before tool release. Overmoulding trials on conventional hydraulic injection-moulding machines with clamp force from 500 kN to 1,500 kN are used for process development; unbalanced multicavity tools can produce cavity-to-cavity hardness variation because of differences in hold pressure.

For overmoulding onto polar substrates such as ABS or PC, direct adhesion between 6014 and the polar substrate is low. A tie layer of maleated polypropylene or maleated SEBS with maleic anhydride content of 0.5–1.0 wt% is normally inserted as a bonding film or co-injected layer. Peel strength is then evaluated per ISO 8510-2 or ASTM D903; published data for 6014 without tie-layer priming on polar substrates are limited.

Film Stretching, Microporosity, and Filler Loading

Breathable-film formulations based on SEBS 6014 typically contain calcium carbonate at 30–60 wt% and are cast or blown before machine-direction stretching. The filler particles detach from the matrix during uni-axial stretching to create micropores; moisture vapour transmission rate is measured according to ASTM E96/E96M and is a function of film thickness, draw ratio, filler particle size, and surface treatment. Published data for 6014 in this specific filled-film configuration are limited; therefore, laboratory-scale cast line trials with a draw ratio of 2:1 to 4:1 are used to establish the pore-density response before commercial modelling. The low styrene content and high elongation at break reduce stress whitening at high draw ratio compared with high-styrene SEBS, but film blocking and unwind force may increase unless anti-block masterbatch is added at 2–5 wt%.

Replacing SBS in Hot-Melt Adhesives and Sealants

SEBS 6014 is substituted for SBS in adhesive and sealant systems where the polymer melt is held at 160–180 °C for extended periods and where yellowing or backbone oxidation is a known failure mode. The hydrogenated ethylene/butylene midblock eliminates allylic unsaturation; this shifts the degradation mechanism from allylic hydrogen abstraction to saturated-chain oxidation, which is slower under the same oven-aging conditions. Comparative retention of elongation can be measured after accelerated heat ageing per ASTM D573 at 150 °C or 175 °C. Formulations commonly use hydrogenated hydrocarbon tackifiers with ring-and-ball softening point of 95–110 °C; viscosity stability is monitored at 180 °C for 8 h using ASTM D3236. Because the styrene content is low, formulations intended for service above 60 °C require endblock-resin reinforcement or polypropylene addition to prevent cohesive failure.

For medical elastomer applications, compounds based on 6014 may be sterilized by ethylene oxide or gamma irradiation. Gamma sterilization at doses above 25 kGy can crosslink or chain-scission the styrenic phase, shifting tensile and elongation values; dose mapping per ISO 11137 and post-sterilization tensile testing per ISO 37 are required. The neat resin is not a substitute for a drug master file or biocompatibility assessment; final compounds must be tested under ISO 10993-5 and ISO 10993-10 when intended for skin contact.

For food-contact and medical articles, 6014 may be evaluated in the final formulation under 21 CFR 177.1810 for repeated-use rubber articles; the neat resin data alone do not establish food-contact compliance. Electrical and electronic articles are qualified under RoHS Directive 2011/65/EU for restricted heavy metals at the finished-article level. The polymer itself has a typical upper continuous service temperature of 80–90 °C in load-bearing applications; unreinforced 6014 exhibits compression set after 22 h at 70 °C that is typically above 60% unless the compound is oil-extended or crosslinked. Sulfur vulcanization is ineffective because the midblock is saturated; peroxide crosslinking in the presence of polypropylene may be used with appropriate co-agents, but scorch time must be measured with a moving-die rheometer according to ISO 6502. Immersion in aromatic, chlorinated, or ketone solvents should be avoided for load-bearing or dimensionally stable articles because styrene domain swelling reduces physical crosslink density.