Butyl rubber is a synthetic rubber copolymerized from isobutylene and a small amount of isoprene. Its most significant characteristic is its extremely low gas permeability, making it difficult for air and water vapor to pass through. Therefore, it is widely used in tire inner liners and tubes, sealing materials requiring airtightness, and gaskets. Furthermore, it possesses excellent weather resistance, ozone resistance, heat resistance, and chemical resistance (acids and alkalis), and also excels in vibration absorption and electrical insulation, leading to its adoption in a wide range of applications such as anti-vibration materials, medical stoppers, and electrical insulation parts. Similar to general rubber, processing involves kneading followed by extrusion molding or press molding (vulcanization molding).