Weather-resistant STP adhesive and sealant with a broad adhesion spectrum
Sikaflex®-521 UV is a weather-resistant, one-component STP adhesive and sealant with good adhesion to a wide range of substrates such as metals, ABS, PC, FRP and wood where no special pre-treatment is usually required. This universal product is suitable for interior and exterior sealing.
- Resistant to ageing and weathering
- Good adhesion to a wide range of substrates without special pre-treatment
- Free from isocyanate and solvents
PRODUCT ADVANTAGES
- Resistant to ageing and weathering
- Good adhesion to a wide range of substrates without special pre-treatment
- Free from isocyanate and solvents
- Can be painted over
- Sandable
- Low odor
Application
- Surface pre-treatment
The bonding surfaces must be clean, dry and free of grease, oil and dust. The surface pre-treatment depends on the specific nature of the substrate and is crucial for a durable bond. Instructions for substrate pre-treatment can be found in the current Sika® pre-treatment table. The information contained therein is based on experience and must always be verified by preliminary tests with original materials.
We recommend pre-treatment with SikaPrimer 207 Link for all surfaces except wood.
- Application
Sikaflex®-521 UV can be processed between 5 °C and 40 °C. Changes in reactivity and application properties must be taken into account. The optimum temperature for substrate and sealant is between 15 °C and 25 °C.
Apply Sikaflex®-521 UV with a suitable cartridge/bag gun or pump system. Information on selecting and setting up a suitable pump system can be obtained from System Engineering at Sika Industry.
- Smoothing
Smoothing must be carried out before the sealant forms a skin. For smoothing we recommend Sika® Smoothing Agent N Link. Other smoothing agents must be tested for their suitability.
- Removal
Uncured Sikaflex®-521 UV can be removed from tools and equipment with Sika® Remover-208 Link or other suitable solvents. Cured material can only be removed mechanically.
Hands/skin must be washed immediately with suitable cleaning cloths (e.g. Sika® Cleaner-350H) or industrial hand cleaners and water. No solvents on the skin!








