SEBS (styrene–ethylene/butylene–styrene) is a thermoplastic elastomer: it stretches and recovers like rubber, yet it melts and can be injection-moulded or extruded like a plastic. Because its rubbery mid-block is fully saturated, SEBS resists heat, UV, ozone and oxidation far better than SBS, which makes it the base polymer for soft-touch grips, hoses and tubing, medical compounds, adhesives and PP modification.
This guide explains what SEBS is made of, the properties that matter in a formulation, where SEBS is used, and how to choose a grade by styrene content and structure. If you are deciding between hydrogenated and standard styrenic block copolymers, read SEBS vs SBS next.
What is SEBS made of?
SEBS is a styrenic block copolymer (SBC). Each chain has three blocks: a hard polystyrene (PS) block at each end and a soft ethylene–butylene (EB) block in the middle. It is made by hydrogenating SBS: the butadiene mid-block of SBS still carries double bonds, and hydrogenation turns it into a saturated ethylene–butylene chain. That one step is why SEBS outlasts SBS outdoors and at higher processing temperatures.
In the solid, the polystyrene ends of many chains gather into tiny glassy domains. These domains act as physical cross-links that hold the rubbery mid-blocks together, so SEBS needs no vulcanization. When the material is heated above the softening point of polystyrene, the domains melt and the polymer flows; on cooling they re-form. SEBS belongs to the wider family of thermoplastic elastomers.
Is SEBS a rubber or a plastic?
Both, which is the point of a thermoplastic elastomer. SEBS rubber behaves like a cross-linked elastomer at room temperature, but the cross-links are physical, not chemical. That gives SEBS the soft feel and recovery of rubber with the processing of a thermoplastic: short cycle times, colour in the melt, and reusable sprues and runners. Neat SEBS is rarely used on its own; it is usually compounded with oil, PP and fillers into an SEBS elastomer compound (often just called TPE or TPS).
Key properties of SEBS
| Property | What it means in practice |
|---|---|
| Thermoplastic elastomer | Rubber-like at room temperature but processed on injection-moulding and extrusion lines; no vulcanization, and clean scrap can be reground |
| Saturated mid-block | Much better heat, UV, ozone and oxidation resistance than SBS |
| Oil extension | Takes up large amounts of paraffinic oil, so compounds range from gel-soft to firm |
| Polyolefin compatibility | Blends well with PP and PE, and bonds to PP in two-shot moulding |
| Low-temperature flexibility | The ethylene-butylene phase stays rubbery well below freezing |
| Upper use limit | Polystyrene domains soften near 100 °C; PP in the compound raises heat resistance |
| Clean and colourable | Low odour, light colour and easy pigmenting; selected grades are listed for medical uses |
Two levers control most SEBS compounds. Oil makes them softer and easier to flow; PP makes them harder, stiffer and more heat resistant. Fillers lower cost, and the styrene content of the SEBS sets the balance between strength and softness.
SEBS applications
The main SEBS applications fall into six groups. The grades named here are the LCY Globalprene SEBS grades on our LCY SEBS page, with the uses LCY lists for them.
Soft-touch overmoulding and injection-moulded parts
SEBS compounds are the standard material for soft grips on tools, toothbrushes, razors, kitchen utensils and electronics, and for seals, plugs and feet. In two-shot or insert moulding they bond to PP by melt adhesion without primers; bonding to ABS, PC or PA needs a specially modified compound. Plastic-modification grades such as 7533, 9550 and 9901 are typical starting points.
Hoses, tubing and profiles
Extruded SEBS compounds are used for flexible hoses, tubing and window and appliance seals where a thermoplastic replacement for vulcanized rubber or plasticised PVC is wanted. The saturated mid-block keeps hoses flexible after long UV and ozone exposure, and the compound can be made translucent or coloured.
Medical and hygiene products
Medical tubing, stoppers, grips and hygiene components use SEBS because it is soft, clean, free of plasticiser and can be sterilised by common methods. LCY lists 9550, 9551 and 9552 (and their U versions) for medical uses. The finished compound, not the base polymer, must meet the regulatory tests for each device.
PP and PE modification
SEBS raises the impact strength and low-temperature toughness of PP and improves the flexibility of PE film. The radial, low-styrene grade 9645D is listed for PP impact toughening, and 9526D for impact-resistant toughening and protective film. For automotive PP compounds, also compare POE, which is the more common choice when cost per kilogram decides.
Adhesives, sealants and protective film
In hot-melt adhesives, pressure-sensitive adhesives and sealants, SEBS gives cohesive strength and ageing resistance, and it does not yellow like unsaturated rubbers. Low-styrene 9557D, 9526D and 9901 are listed for adhesives, sealants and protective film.
Asphalt, waterproofing and oil gels
SEBS is used in premium modified bitumen and waterproofing membranes where long-term weathering matters, with 7550, 7551 and 7554 listed for this. Because it absorbs large amounts of oil, SEBS also forms soft gels for cushions, toys, cable filling and oil modification (7550, 7550U).
How to choose an SEBS grade
Start from the application, then check three grade properties:
- Styrene content. More styrene (30–33%) gives higher strength, hardness and heat resistance; low styrene (13%) gives softer, more flexible, tackier products for film and adhesives.
- Structure. Linear grades are the general choice; radial grades such as 9645D flow differently and are used where the producer lists them, for example PP impact toughening.
- Molecular weight. Higher-molecular-weight SEBS holds more oil and keeps its properties at higher temperature, but it is harder to process; lower-molecular-weight grades flow more easily.
| Need | Styrene content (BD/SM) | LCY grades on our page | Typical uses listed |
|---|---|---|---|
| Soft, flexible films and tacky products | 13% (87/13) | 9557D (linear), 9645D (radial) | Film and protective film, adhesives, sealants, waterproofing; 9645D also for PP impact toughening |
| General TPE compounds and overmoulding | 30–33% (70/30 to 67/33) | 7533, 7550, 9550, 9551, 9552, 9901 | Plastic modification, footwear and foam, adhesives, sealants |
| Medical and hygiene compounds | 30–33% | 9550, 9550U, 9551, 9551U, 9552, 9552U | Plastic modification and medical |
| Asphalt modification and waterproofing | 30–33% | 7550, 7551, 7554, 7554U | Asphalt modification and waterproofing membranes |
| Oil gels and soft compounds | 30% (70/30) | 7550, 7550U | Oil modification, adhesives, footwear |
| Protective film and impact toughening | 31% (69/31) | 9526D | Adhesive, protective film, impact-resistant toughening |
BD/SM is the ratio of butadiene (before hydrogenation) to styrene by weight. Grade data sheets are sent on request with your quotation.
Processing SEBS compounds
- Compounding. Pre-absorb the oil into the SEBS crumb, then compound with PP, filler and stabilizers on a twin-screw extruder. An antioxidant package protects the compound during processing; see our antioxidants and HALS.
- Moulding and extrusion. SEBS compounds run on standard PP equipment. They need no drying unless fillers or the substrate require it.
- Overmoulding. Mould the rigid PP part first and overmould the SEBS compound while the substrate is still warm for the best bond.
- Regrind. As a thermoplastic, clean SEBS scrap can be reused within the limits your part allows.
SEBS compared with other elastomers
- SEBS vs SBS: SBS is cheaper but ages faster; see SEBS vs SBS and our SBS and oil-extended SBS grades.
- SEBS vs TPV: TPV handles higher temperatures and oils better; see TPV vs TPE.
- SEBS vs POE and EPDM: for PP impact modification, see what is POE and POE vs EPDM.
- SEBS vs silicone: silicone takes higher temperatures; SEBS is cheaper and is moulded like a thermoplastic.
Frequently asked questions
What does SEBS stand for?
Styrene–ethylene/butylene–styrene: two polystyrene end blocks joined by an ethylene–butylene mid-block, made by hydrogenating SBS.
What is SEBS rubber used for?
Soft-touch grips and overmoulded parts, hoses and tubing, seals, medical and hygiene products, PP and PE modification, adhesives and sealants, asphalt modification and soft oil gels.
Can SEBS be recycled?
Yes. SEBS is a thermoplastic, so production scrap can be reground and remelted. Overmoulded parts made of SEBS on PP can often be recycled together with polyolefins, but check this with your recycler.
Is SEBS food-safe or medical-grade?
It depends on the grade and on the finished compound. Some SEBS grades are listed by the producer for medical uses; ask us for the producer’s declaration for your market before you specify one.
How much oil can SEBS absorb?
A lot. High-molecular-weight SEBS can carry more oil than its own weight without bleeding, which is how very soft gels are made. The exact oil level depends on the grade, the oil type and the PP content.
Get an SEBS recommendation
Tell us the part, the process, the hardness and temperature range you need, and any medical, food-contact or weathering requirements. As an SEBS supplier, we will suggest an LCY grade or compound route, email the TDS and arrange samples. Contact our technical team or write to info@sychemtech.com.
Related products: our SEBS and SBS range, LCY SEBS grades, TPV and TPE, POE elastomers and PP resin.
