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Sikaflex-591 sealant
At a glance
- For interior and exterior
- High weather resistance
- Permanently elastic
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Looking for a versatile sealant for your boat? Sikaflex-591 is a multifunctional marine sealant specially developed for the demanding conditions encountered on the water. Whether you need to seal a joint above or below the waterline, Sikaflex-591 is suitable for a wide range of marine applications. Thanks to its excellent UV resistance, colour stability and mould-resistant properties, Sikaflex-591 is highly suitable for both interior and exterior applications.
Sikaflex-591 is based on Sika’s advanced STP (Silane Terminated Polymer) technology. The sealant is free from solvents, isocyanates, phthalates and PVC and complies with the requirements of the International Maritime Organization (IMO) for low flame spread.
Benefits of Sikaflex-591
- Excellent UV and weather resistance.
- Mould-resistant and colour stable.
- Suitable for both interior and exterior applications.
- Excellent adhesion to most substrates with minimal surface preparation.
- Free from solvents, isocyanates, phthalates and PVC.
- Suitable for use above and below the waterline.
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Complies with IMO requirements for low flame spread.
What is the difference between Sikaflex-591 and Sikaflex-291i?
We are often asked which marine sealant is the best choice. The main difference lies in their UV resistance.
- Sikaflex-591 is particularly suitable for exterior applications thanks to its excellent UV resistance and can be used indoors as well as above and below the waterline.
- Sikaflex-291i is also a versatile marine adhesive and sealant but has more limited UV resistance. For applications that are continuously exposed to UV radiation, Sikaflex-591 is therefore the better choice.
What is Sikaflex-591 used for?
Sikaflex-591 is a versatile sealant specifically developed for marine applications. It is ideal for creating flexible, vibration-resistant joint seals and offers a wide range of uses both above and below deck. It adheres well to many commonly used substrates in the marine industry.
Typical applications of Sikaflex-591 include:
- Bonding and sealing interior and exterior components.
- Flexible joint sealing.
- Sealing non-ferrous metals.
Please note: this sealant is not suitable for use on teak or on plastics that are susceptible to stress cracking, such as acrylic (PMMA/Perspex®) and polycarbonate (PC).
Directions for use
- Surface preparation
Ensure that the surface is clean, dry and free from grease, oil, dust and any other contaminants.
- Priming
Pre-treat the substrate with Sika Aktivator-205. For timber, ABS and non-ferrous metals, subsequently apply Sika Multiprimer Marine to achieve optimum adhesion.
- Applying the sealant
Apply the sealant using a standard cartridge sealant gun. The ideal application temperature is between 15°C and 25°C. Keep in mind that the skin formation time is approximately 35 minutes. Please note: if PU adhesives or other sealants have also been applied, allow them to cure for at least 24 hours before applying Sikaflex-591.
- Finishing
Tool the sealant joints smooth before skin formation occurs.
Specifications
Packaging: 70 ml (tube), 300 ml (cartridge)
Colour: white, grey, black
Chemical base: silane-modified polymer
Cure mechanism: moisture curing
Hardness (Shore A): 45
Tensile strength: 2.2 MPa
Elongation at break: 500 %
Shrinkage: 1 %
Service temperature: -50 °C to +80 °C
Density (uncured): 1.5 kg/L
Non-sag properties: very good
Application temperature: between 5 °C and 40 °C
Open time: 20 minutes
Skin time: 35 minutes
Shelf life: 12 months (stored at temperatures below 25 °C)
Application gun: caulking gun for cartridges
Product properties
The key technical properties clearly listed in one place.
- Article number
- LIJ001293
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The recommended application temperature range indicates the conditions under which the product can generally be applied and cured properly. Three temperatures matter:
- Air: the temperature in the workshop or outdoors.
- Substrate: the temperature of the surface being treated.
- Product: the temperature of the resin, adhesive or coating itself.
A cold substrate can cause condensation and affect adhesion. At higher temperatures, two-component products may react faster, reducing their working time. Check the dew point and follow the product instructions.
- 5-40 °C
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The chemical base describes the chemistry of an adhesive, sealant, resin or coating, such as epoxy, polyester, polyurethane, (methyl)methacrylate or a hybrid polymer. It affects curing, flexibility and adhesion. Products with the same chemical base are not necessarily suitable for the same applications.
- Silane-modified polymer (STP)
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Hardness describes a material's resistance to indentation. For silicone rubber and other elastomers, the Shore A scale is commonly used: Shore A 15, for example, is softer than Shore A 40. Harder plastics may be rated on the Shore D scale. The number belongs to its Shore scale and is not a unit like MPa; values on different scales cannot be directly compared.
- Shore A 45
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The period for which an unopened product remains usable under the specified storage conditions. Check whether the period starts from the manufacturing date or another date. Shelf life may be shorter after opening, especially for products sensitive to air or moisture.
- 12 months
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The time after application during which a skin forms on the surface of a sealant. Tool the joint before the skin develops, as adjusting it afterwards can affect the finish or adhesion. Temperature and humidity influence this time.
- 35 minutes
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Cure shrinkage describes how much a resin, adhesive or rubber becomes smaller as it cures. The value is usually given as a percentage (%) and may refer to volume shrinkage or shrinkage along one dimension; these are not the same. Shrinkage matters for casting accuracy and for limiting stress or distortion.
- 1%
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Open time is the period during which an applied adhesive, sealant or mortar can still be assembled, positioned or adjusted. It is usually given in minutes under specified conditions, often around 20 or 23 °C. Open time generally starts at application and may differ from the working time after mixing.
- 20 minutes
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Elongation at break indicates how much a material can stretch during a tensile test before it breaks. It is expressed as a percentage (%) of the original length. At 100% elongation, the material has doubled in length just before breaking. A high value indicates a high ability to deform, but not how much force is needed.
- 500%
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Sag resistance describes how well a paste, sealant or coating stays in place after application without running or slumping. It matters on vertical surfaces, in thick adhesive joints and for overhead repairs.
A product may be thixotropic: it becomes easier to work when stirred or spread, then thickens again at rest. This makes application easier without the material immediately running down the surface. Sag resistance is not the same as viscosity; behaviour after application also matters.
- Very good
-
Tensile strength is the maximum tensile stress a material can withstand during a tensile test before failure. It is usually expressed in MPa (megapascals) or N/mm² (newtons per square millimetre); 1 MPa = 1 N/mm². Under comparable test conditions, a higher value means greater resistance to tension. In composites, fibre orientation also affects the result.
- 2.2 MPa
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The curing mechanism explains how a product develops its final strength or shape. The main mechanisms are:
- Two-component reaction (2K): a chemical reaction begins once components A and B are mixed. Mixing ratio and working time are important.
- Moisture curing (often 1K): the product reacts with moisture in the surrounding air. Temperature, humidity and film thickness affect the process.
- UV curing: light of the appropriate wavelength triggers the reaction. Areas that are not exposed to the light may not cure fully.
- Physical drying: water or solvent evaporates. This is different from chemical curing.
Some products use more than one mechanism, so the correct application conditions depend on the particular system.
- Moisture-curing
- Net contents
- 300 ml, 70 ml
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Heat resistance describes the temperature a material can withstand after correct processing and curing, usually expressed in degrees Celsius (°C). Continuous exposure is different from a brief temperature peak, and mechanical loading may also affect the limit. Heat resistance is not the same as the temperature at which the product can be applied.
- -50 to 80 °C
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