Styrene Isoprene Styrene (SIS) polymers are a type of thermoplastic elastomer composed of alternating segments of styrene and isoprene monomers. SIS exhibits rubber-like elasticity and resilience, along with the processability and versatility of thermoplastics. It is commonly used in applications requiring flexible and impact-resistant materials, such as adhesives, sealants, and certain types of medical devices.