SIS 1126 is a clear, linear styrene-isoprene-styrene (SIS) block copolymer based on styrene and isoprene, with a polystyrene (bound styrene) content of 16%. It is a thermoplastic elastomer: the glassy polystyrene end blocks act as physical cross-links for the rubbery polyisoprene mid-block, giving a soft, tacky, highly elastic material that melts and flows when heated and re-solidifies on cooling. SIS 1126 is used as an ingredient in formulating adhesives, sealants and coatings, and as a modifier of bitumen, thermoplastics and other compound formulations. CAS 25038-32-8; typical trade designation SIS 1126.
Specifications
| Property | Value |
|---|---|
| Appearance | White (clear, translucent pellets or crumb) |
| Structure | Linear triblock, polystyrene-polyisoprene-polystyrene (SIS) |
| Bound styrene | 16.0 ± 2.0 wt% |
| Di-block content | 50.0 ± 3.0 wt% |
| Volatility | ≤ 0.70 wt% |
| Ash content | ≤ 0.20 wt% |
| Yellow index | ≤ 6.0 |
| Melt flow rate | 8.0–14.0 g/10 min |
| Tensile strength | ≥ 4.0 MPa |
| Elongation at break | ≥ 1100% |
Chemical Structure
SIS is a triblock copolymer of styrene (C8H8) and isoprene (C5H8) prepared by anionic polymerisation. Nominal repeat: (C8H8)x–(C5H8)y–(C8H8)x. Backbone SMILES (monomer units): C=CC1=CC=CC=C1.CC(=C)C=C.
Typical Applications
- Hot-melt and pressure-sensitive adhesives: labels, tapes, hygiene and packaging.
- Sealants, coatings and mastics.
- Modifier of bitumen (asphalt) and thermoplastics.
- Compounded rubber and general formulation use.
Packaging and Storage
Supplied in 25 kg bags, or as agreed. Store in a cool, dry, well-ventilated place away from direct sunlight, heat and ignition sources. Keep the material sealed and add antioxidant as supplied; because the polyisoprene mid-block is unsaturated, protect from prolonged heat, light and air to avoid ageing.
FAQ
What is the CAS number of SIS 1126? The styrene-isoprene-styrene block copolymer is assigned CAS 25038-32-8.
What does the 16% bound styrene mean? It is the weight fraction of polystyrene in the polymer. Lower styrene content gives a softer, tackier, more elastic material suited to adhesives; higher styrene gives more strength and hardness.
Is SIS the same as SBS? No. Both are styrenic block copolymers, but SIS has a polyisoprene mid-block and SBS a polybutadiene mid-block. SIS typically offers better tack and adhesion; SBS is often used where higher cohesion is needed.
Further Information
For the full technical background, see SIS (Styrene-Isoprene-Styrene) Block Copolymer: Properties, Production and Applications. To request current specifications, a COA or a quotation, contact the PolyBlueChem team.
