Sikaflex -221 Multi-Purpose 1-Component Polyurethane Adhesive Sealant
A multi-purpose 1-component polyurethane adhesive and sealant that bonds well to a wide variety of substrates — metals, metal primers and 2-component paint coatings, ceramic materials and plastics. Ideal for making permanent elastic seals.
P.O Box 2806, Industrial Area 15, Sharjah UAE — expert coordination, authentic supply, site-ready delivery.
What is Sikaflex-221?
Sikaflex-221 is a multi-purpose, 1-component polyurethane adhesive and sealant that bonds well to a wide variety of substrates such as metals, metal primers and paint coatings (2-component systems), ceramic materials and plastics. It is ideal for making permanent elastic seals, as well as for internal sealing and simple bonding applications.
It cures on exposure to atmospheric moisture to form a durable, elastic joint. This product is suitable for experienced professional users only and should be tested with the actual substrates and conditions to ensure adhesion and material compatibility, as it is prone to stress cracking.
Bonds To
Key Benefits
- Bonds a wide variety of substrates — works with metals, plastics, wood, ceramics and painted surfaces as an excellent adhesive.
- Resistant to ageing — withstands weather and environmental factors while maintaining long-term elasticity for low-cost maintenance.
- Can be sanded and painted — suitable for visible joints, giving a clean finish.
- Rail-certified — passes EN45545-2 R1/R7 HL3 fire-safety requirements.
- Non-corrosive — safe for metals and other sensitive substrates.
- Low odour — releases very little smell — work- and business-friendly.
Cured Mechanical Properties
Chemical & Physical Properties
| Base Chemistry | 1-component polyurethane |
| Colour | White, Grey, Black, Brown |
| Cure Mechanism | Moisture |
| Density (uncured) | 1.3 kg/l (depending on colour) |
| Non-Sag Properties | Good |
| Application Temperature | 5 – 40 °C (ambient) |
| Skin Time | 60 minutes A |
| Open Time | 45 minutes A |
| Shrinkage | 5% |
| Shelf Life | 12 months B |
A — 23 °C / 50 % r.h. · B — Storage below 25 °C.
Curing Speed
| 23 °C / 50% r.h. | 3–4 mm after day 1, up to 8 mm after 4–5 days |
| 10 °C / 50% r.h. | 2 mm after day 1, up to 4 mm after 9–10 days |
Pack Sizes & Chemical Resistance
| Pack Sizes | Cartridge (300 ml), Unipack (400 ml & 600 ml), Pail (23 L), Drum (195 L) |
| Good Resistance | Fresh water, seawater, diluted acids & caustic solutions |
| Temporary Resistance | Fuels, mineral oils, vegetable & animal fats/oils |
Application Guide
Follow these steps for reliable bonding and elastic sealing with Sikaflex-221. The optimum temperature for both substrate and sealant is between 15 °C and 25 °C. Always refer to the current Sika Product Data Sheet.
Surface Preparation
Surfaces must be clean, dry and free from grease, oil and dust, and should be treated according to the specific nature of the substrate — correct preparation is crucial for a long-lasting bond. Use the appropriate Sika primer/activator for the substrate where required.
Application
The product can be processed between 5 °C and 40 °C, with the understanding that reactivity and application properties change with temperature. The optimum temperature is between 15 °C and 25 °C for both the substrate and sealant. Apply using manual, pneumatic or dispensing equipment such as electric-driven piston guns or pumps.
Tooling & Finishing
Tool and finish the sealant before a skin forms over the surface. Sika Tooling Agent N is recommended; any alternative brands should be tested before application for compatibility and suitability.
Overpainting
Painting is possible after skin formation. Where the paint requires a baking process, ensure the sealant is fully cured first. Paints such as 1C-PUR and 2C-Acrylic based systems are usually suitable — conduct preliminary trials under the actual manufacturing conditions to confirm.
Removal
Cured product can be removed physically. Uncured product can be removed using Sika Remover-208 or an alternative suitable solvent.
Chemical Resistance
Once cured, Sikaflex-221 offers general resistance to fresh water, seawater, diluted acids and caustic solutions, with temporary resistance to fuels, mineral oils and vegetable or animal fats and oils. See the Cautions below for chemicals it does not resist.
Chemical Limitations
Not resistant to certain chemicals — organic acids, glycolic alcohol, concentrated mineral acids, caustic solutions or solvents. Avoid exposure to these in service.
Skin Contact
If hands or skin are exposed, clean immediately with hand wipes (Sika Cleaner-350J recommended) or a suitable industrial hand cleaner and water. Never use solvents on the skin.
Paint Elasticity
Paints have lower elasticity than the sealant, which could lead to cracking of the paint over the joint area. Select a flexible paint system where movement is expected.
Related Products
Sikaflex-221 sits within Sika's polyurethane adhesive-sealant range. Explore the related grades below for higher-strength bonding, marine glazing and specialist applications. All stocked by Highway BMT.