Description
Sikaflex®-521 UV is a one-component silane terminated polymer (STP) adhesive sealant designed for interior and exterior sealing and bonding applications. This moisture-curing, non-sag sealant provides reliable adhesion to a wide range of substrates without the need for special pre-treatment, making it suitable for general-purpose industrial and construction use.
Key Features
- One-component silane terminated polymer adhesive sealant
- Designed for both sealing and bonding applications
- Broad adhesion to multiple substrates without special pre-treatment
- Weathering and aging resistant for exterior exposure
- Isocyanate-free and solvent-free formulation
- Low odor for improved handling
- Can be painted and sanded after curing
- Non-sag consistency for vertical and overhead applications
Technical Specifications
| Specification | Value |
|---|---|
| Chemical Base | Silane Terminated Polymer |
| Color | White, grey |
| Cure Mechanism | Moisture-curing |
| Density (uncured) | 1.4 kg/l (11.7 lb/gal) |
| Application Temperature | 5 to 40 °C (41 to 104 °F) |
| Skin Time | 30 minutes |
| Shrinkage | 2% |
| Shore A Hardness | 40 |
| Tensile Strength | 1.8 MPa (260 psi) |
| Elongation at Break | 400% |
| Tear Propagation Resistance | 5.5 N/mm (30 pli) |
| Service Temperature | -50 to 90 °C (-58 to 194 °F) |
| Shelf Life | 12 months |
Compatible Substrates and Materials
- Metals
- ABS
- Polycarbonate (PC)
- FRP (fiber-reinforced plastic)
- Wood
- Metal primers and coated surfaces
- Ceramic materials
- Various plastics
Application Guidance
Surfaces must be clean, dry, and free from grease, oil, and dust prior to application. Sikaflex®-521 UV can be applied between 5 °C and 40 °C, with optimal performance between 15 °C and 25 °C. Apply using manual or powered dispensing equipment and complete tooling within the skin time. Adhesion testing on actual substrates is recommended, especially for materials prone to stress cracking.
Typical Use Cases
- General-purpose sealing in construction and industrial applications
- Interior and exterior joint sealing
- Light bonding applications across multiple substrates
- Sealing in transportation and fabrication assemblies
- Maintenance and repair sealing tasks
Target Industries and Buyers
- Construction and building trades
- Transportation and vehicle manufacturers
- Industrial fabrication and assembly
- Maintenance, repair, and operations (MRO)
- General contractors and installers
Performance Advantages
Within the general-purpose adhesive sealant category, Sikaflex®-521 UV offers broad substrate compatibility combined with weather-resistant performance. Its silane terminated polymer chemistry enables adhesion without special pre-treatment on many surfaces, making it a versatile option for mixed-material assemblies and exterior sealing applications.
Common Questions
Q: What type of product is Sikaflex®-521 UV?
A: It is a one-component silane terminated polymer adhesive sealant.
Q: Can it be used outdoors?
A: Yes, it is designed with weathering resistance for exterior applications.
Q: Does it require primer on all substrates?
A: It bonds to many substrates without special pre-treatment, though testing is recommended.
Q: Is it suitable for bonding and sealing?
A: Yes, it is designed for both sealing and light bonding applications.
Q: Can it be painted after curing?
A: Yes, it can be painted and sanded after curing.
Q: What is the curing mechanism?
A: It cures by reacting with atmospheric moisture.
Q: What is the application temperature range?
A: The recommended range is 5 °C to 40 °C (41 °F to 104 °F).
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