Jul 03,2025 ZHONGLITEC

What is Hydrogenated Styrene-Isoprene Block Copolymer(SEP(S))

Hydrogenated Styrene-Isoprene Block Copolymer (SEP(S)) is a specialized thermoplastic elastomer that belongs to the family of hydrogenated styrenic block copolymers (HSBCs). It is composed of three distinct polymer segments:

S: Styrene (polystyrene blocks – provide rigidity and strength)

E: Ethylene

P: Propylene

(S): Another styrene block (in some structures)

This material is produced by first synthesizing a styrene-isoprene-styrene (SIS) block copolymer, and then hydrogenating the isoprene mid-block to increase its thermal stability, weather resistance, and oxidative durability. The result is a copolymer with soft rubbery behavior and excellent mechanical and environmental resistance, useful in demanding applications.

Key Features of SEP(S)

Property	Description
Thermoplastic Elasticity	Soft, flexible like rubber but processes like plastic
High Weather Resistance	Excellent UV and ozone resistance due to hydrogenation
Chemical Stability	Improved resistance to oxidation and aging
Low Permanent Deformation	Good recovery after stretching or compression
Excellent Clarity	Some grades offer optical transparency suitable for consumer goods
Low Color and Odor	High purity allows for use in hygiene and medical applications

Types and Structures

SEP(S) can come in various molecular architectures:

Linear Triblock (SEP): Styrene end blocks with a hydrogenated polyisoprene mid-block
Multiblock or Star-Shaped: Multiple arms of SEP chains for higher strength or viscosity
Blended with Other Polymers: Often blended with polypropylene, polyethylene, or oils to tailor hardness and elasticity

Common Applications

Hydrogenated SEP(S) is used where durability, flexibility, and processability are all required:

Adhesives: Especially in hot-melt pressure-sensitive adhesives (HMPSA)

Medical and Hygiene Products: Tubing, films, closures, bandages

Footwear: Outsoles, midsoles, cushioning materials

Automotive Parts: Seals, gaskets, soft-touch surfaces

Consumer Goods: Grips, soft-touch packaging, toys

Wires and Cables: As insulation and sheath components

Advantages over Non-Hydrogenated SIS

Much better thermal stability

Improved UV and oxidation resistance

Greater durability in outdoor or high-heat environments

Broader application range from medical to industrial

Processing and Handling

Like other thermoplastic elastomers, SEP(S) can be processed using conventional plastic processing methods:

Injection Molding

Extrusion

Film Casting

Blow Molding

Compounding with other resins or oils

It requires no vulcanization (unlike rubber), enabling fast and energy-efficient production.

Summary

Hydrogenated Styrene-Isoprene Block Copolymer (SEP(S)) is a high-performance elastomer that combines the elasticity of rubber with the processability of plastic, enhanced by the hydrogenation of its soft block for superior durability. It is a versatile material used across multiple industries that require strength, flexibility, and stability over time, especially in medical, automotive, and adhesive applications.