Sikaflex®-521 UV
Isocyanate-free, weathering-resistant sealant
Sikaflex®-521 UV is a weathering-resistant, 1-component Silane Terminated Polymer (STP) sealant that cures on exposure to atmospheric humidity. This multipurpose product is suitable for internal and external sealing applications.
- Ageing and weathering resistant
- Bonds well to a wide variety of substrates without the need for special pre-treatment
- Can be painted
- Can be sanded
- Low odour
- Isocyanate- and solvent-free
- Silicone- and PVC-free
PRODUCT BENEFITS
- Ageing and weathering resistant
- Bonds well to a wide variety of substrates without the need for special pre-treatment
- Can be painted
- Can be sanded
- Low odour
- Isocyanate- and solvent-free
- Silicone- and PVC-free
Usage
Sikaflex®-521 UV adheres well to a wide variety of substrates and is suitable for elastic sealing and bonding. Suitable substrate materials include timber, metals, metal primers and paint coatings (2-part systems), ceramic materials and plastics. 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. Tests with actual substrates and conditions have to be performed to ensure adhesion and material compatibility.Packaging
| Cartridge | 300 ml |
| Unipack | 600 ml |
Product Details
| Chemical base | Silane Terminated Polymer | |
| Colour (CQP001-1) | White, grey | |
| Cure mechanism | Moisture-curing | |
| Density (uncured) | depending on colour | 1.4 kg/l |
| Non-sag properties | Good | |
| Application temperature | ambient | 5 ─ 40 °C |
| Skin time (CQP019-1) | 30 minutes A | |
| Curing speed (CQP049-1) | (see diagram) | |
| Shrinkage (CQP014-1) | 2 % | |
| Shore A hardness (CQP023-1 / ISO 48-4) | 40 | |
| Tensile strength (CQP036-1 / ISO 527) | 1.8 MPa | |
| Elongation at break (CQP036-1 / ISO 527) | 400 % | |
| Tear propagation resistance (CQP045-1 / ISO 34) | 5.5 N/mm | |
| Service temperature (CQP513-1) |
4 hours 1 hour | -50 ─ 90 °C 140 °C 150 °C |
| Shelf life | cartridge / unipack | 12 months B |
CQP = Corporate Quality Procedure | A) 23 °C / 50 % r. h. | B) storage below 25 °C |
CURE MECHANISM
Sikaflex®-521 UV cures by reaction with atmospheric moisture. At low temperatures the water content of the air is generally lower and the curing reaction proceeds somewhat slower (see diagram 1).
Diagram 1: Curing speed Sikaflex®-521 UV
CHEMICAL RESISTANCE
Sikaflex®-521 UV is generally resistant to fresh water, seawater, diluted acids and diluted caustic solutions; temporarily resistant to fuels, mineral oils, vegetable and animal fats and oils; not resistant to organic acids, glycolic alcohol, concentrated mineral acids and caustic solutions or solvents.
Application
Surface preparation
Surfaces must be clean, dry and free from grease, oil and dust.
Surface treatment depends on the specific nature of the substrates and is crucial for a long lasting bond. Suggestions for surface preparation may be found on the current edition of the appropriate Sika® Pre-Treatment Chart. Consider that these suggestions are based on experience and must be verified by tests on original substrates.
Application
Sikaflex®-521 UV can be processed between 5 °C and 40 °C but changes in reactivity and application properties have to be considered. The optimum temperature for substrate and sealant is between 15 °C and 25 °C.
Sikaflex®-521 UV can be processed with hand, pneumatic or electric driven piston guns as well as pump equipment. For advice on selecting and setting up a suitable pump system, contact the System Engineering Department of Sika Industry.
Tooling and finishing
Tooling and finishing must be carried out within the skin time of the sealant. It is recommended to use Sika® Tooling Agent N. Other finishing agents must be tested for suitability and compatibility prior to use.
Removal
Uncured Sikaflex®-521 UV can be removed from tools and equipment with Sika® Remover-208 or another suitable solvent. Once cured, the material can only be removed mechanically. Hands and exposed skin have to be washed immediately using Sika® Cleaner-350H cleaning towels or a suitable industrial hand cleaner and water. Do not use solvents on skin!