SikaFlex 521 UV Weatherproof and UV Resistant Polyurethane Polymer Sealant Adhesive


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Sikaflex®-521 UV is a one component weather resistant sealant based on Silane Termination Polymer (STP) that hardens upon exposure to atmospheric moisture.

This multipurpose product is suitable for interior and exterior sealing applications.


Resistance to aging and atmospheric agents

▪ Adheres well to a wide variety of substrates without the need for special pre-treatments ▪

▪ Can be painted

▪ Can be sanded

▪ Low odor emission

▪ Free of solvent and isocyanate

▪ Free of silicone and PVC


Sikaflex®-521 UV adheres well to a wide range of substrates and is suitable for elastic bonding and sealing.

Suitable substrates are wood, metals, primers for metals and painted surfaces (two-component systems), ceramic and plastic materials.

Seek manufacturer's advice and perform tests on original substrates before using Sikaflex®-521 UV on materials prone to stress cracking.

This product is suitable for experienced professional users only.


Sikaflex®-521 UV can be processed between 5 ° C and 40 ° C but variations in reactivity and application properties must be considered. The optimum temperature for substrates and sealant is between 15 ° C and 25 ° C. Sikaflex®-521 UV can be processed with manual, pneumatic or electric piston guns, as well as with pumping equipment.

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