Sikaflex?-221 is a high-quality multi-purpose 1-component polyurethane adhesive / sealant that cures on exposure to atmospheric humidity. It is suitable for internal sealing and simple bonding applications. Sikaflex?-221 bonds well to a wide variety of substrates and is suitable for making permanent elastic seals of high adhesive strength. Suitable substrate materials are metals, metal primers and paint coatings (2-C systems), ceramic materials and plastics. Test with actual substrates and conditions have to be performed to ensure adhesion and material compatibility.