SIS | High-Performance Styrene-Isoprene-Styrene for Hot Melt Adhesives
Overview
SIS (Styrene-Isoprene-Styrene) is a premium thermoplastic elastomer that has revolutionized the hot melt adhesive industry. This linear triblock copolymer combines the processing advantages of thermoplastics with the elastic properties of rubber, making it the preferred choice for pressure-sensitive adhesives, hot melt formulations, and specialty coating applications across diverse industrial sectors.
SIS belongs to the styrene block copolymer family, featuring a unique molecular architecture with hard styrene end-blocks and a soft isoprene mid-block. This structure creates physical crosslinks through microphase separation, delivering exceptional elasticity without chemical vulcanization. The polymer is produced via sequential anionic polymerization, resulting in controlled molecular weight distribution and consistent performance characteristics.
With CAS number 25038-32-8, SIS typically contains 15-30% styrene content, providing an optimal balance between tack, cohesive strength, and processing flexibility. The isoprene segments contribute superior low-temperature flexibility and adhesion properties, making SIS particularly valuable in hot melt adhesive formulations where permanent tack and repositionability are critical requirements.
Key Features & Benefits
- Exceptional Tack Properties: Superior initial adhesion and permanent tack for pressure-sensitive applications
- Excellent Low-Temperature Performance: Maintains flexibility and adhesion down to -40°C
- Outstanding Processing Characteristics: Low melt viscosity enables easy coating and application
- Superior Cohesive Strength: Balanced molecular structure provides excellent holding power
- Thermal Stability: Maintains performance integrity at elevated processing temperatures
- Chemical Compatibility: Excellent compatibility with tackifying resins and plasticizers
- Reversible Bonding: Thermoplastic nature allows for repositioning and recycling
- Transparent Appearance: Clear polymer base suitable for optical clarity requirements
Applications
SIS dominates the hot melt adhesive industry with applications spanning multiple sectors:
Hot Melt Adhesive Applications
- Pressure-Sensitive Tapes: Medical tapes, packaging tapes, and industrial adhesive tapes
- Label Adhesives: Permanent and removable labels for packaging and industrial marking
- Graphic Arts: Mounting adhesives for signage and display applications
- Assembly Bonding: Automotive interior components and electronic device assembly
- Packaging Sealants: Flexible packaging films and food-grade applications
Industrial Applications
- Footwear Industry: Sole bonding and upper assembly adhesives
- Construction: Roofing membranes and waterproofing systems
- Automotive: Interior trim bonding and vibration dampening
- Electronics: Component encapsulation and wire harnessing
- Medical Devices: Skin-contact adhesives and wound care products
Technical Specifications
SIS exhibits excellent thermal and mechanical properties with typical styrene content ranging from 15-30%, melt flow index of 5-40 g/10min (200°C), and glass transition temperatures optimized for room temperature applications. The polymer demonstrates outstanding solution viscosity characteristics in toluene, typically ranging from 700-2000 mPa·s at 25% concentration.
For full technical details and specific grade comparisons, please view our datasheet (TDS).
Comparison & Alternatives
SIS vs SBS Comparison
While both SIS and SBS are styrene block copolymers, SIS offers superior low-temperature flexibility and tack properties due to its isoprene mid-block. SBS provides higher tensile strength and is more cost-effective for applications requiring structural bonding rather than pressure-sensitive adhesion.
Grade Variations
Different SIS grades offer varying styrene content and molecular weights to optimize performance for specific applications. Higher styrene content grades provide increased cohesive strength, while lower styrene variants offer enhanced tack and flexibility for demanding hot melt adhesive formulations.
FAQ
What is SIS used for?
SIS is primarily used in hot melt adhesive formulations for pressure-sensitive tapes, labels, and packaging applications. Its exceptional tack properties and low-temperature flexibility make it ideal for applications requiring permanent adhesion with repositioning capability.
Is SIS suitable for high-temperature applications?
SIS maintains good performance up to 80°C in service conditions, though processing temperatures can reach 180°C. For applications requiring higher service temperatures, consider SEBS alternatives or specialized high-temperature SIS grades.
What's the difference between SIS and SBS?
SIS offers superior low-temperature flexibility and tack properties due to its isoprene mid-block, making it preferred for pressure-sensitive adhesives. SBS provides higher strength and is more suitable for structural bonding applications.
How does SIS perform in hot melt adhesive formulations?
SIS excels in hot melt formulations due to its low melt viscosity, excellent compatibility with tackifiers, and outstanding pressure-sensitive properties. It typically comprises 20-40% of hot melt adhesive formulations.
What processing equipment is recommended for SIS?
Standard hot melt processing equipment including heated tanks, gear pumps, and slot-die coating systems work well with SIS. Temperature control and proper mixing are essential for optimal performance in adhesive formulations.
Contact SIS Supplier Shenzhen Bohr Chem
Ready to enhance your hot melt adhesive formulations with premium SIS? Contact us today for technical datasheets, sample requests, or processing optimization support for your specific applications.