Sikaflex 521UV UV Resistant LM Polyurethane Sealant 10. 3oz 300ml Cartridge White. Sikaflex 521 UV is a multi-purpose, UV resistant, non-sag, elastic, one-part silane-terminated polymer sealant, which cures on exposure to atmospheric moisture to form a durable elastomer. Sikaflex-521 UV is solvent and isocyanate free. Uses Sikaflex 521 UV bonds well to a wide variety of substrates without the need for special pre-treatment and is suitable for making permanent, high strength elastic seals. Compatible substrate materials include wood, metals, particularly aluminum including anodized components , sheet steels including phosphated, chromated and zinc-plated components , metal primers and paint coatings two-part systems , ceramic materials, plastics and glass. Characteristics Advantages Very low VOC/solvent free. Silicone and PVC-free. Isocyanate-free. High electrical resistance. Resistant to aging and weathering. Sikaflex 521UV UV Resistant LM Polyurethane Sealant 10. 3oz 300ml Cartridge White. Sikaflex 52 1 UV is a multi-purpose, UV resistant, non-sag, elastic, one-part silane-terminated polymer sealant, which cures on exposure to atmospheric moisture to form a durable elastomer. Sikaflex-521 UV is sol