SIKAFLEX 291 iCURE

What Sikaflex 291 iCure is and why choose it

Sikaflex 291 iCure (often marketed as Sikaflex-291i) is a one-component, non-sag polyurethane adhesive sealant, specially developed for marine applications. It cures with atmospheric moisture to form a highly elastic, durable seal that meets the low spread-of-flame requirements of the International Maritime Organisation (IMO) and is Wheelmark approved for use on boats and ships.
All performance data below is based on publicly available product information and may not be fully verified. For critical design or safety decisions, always refer to the current official technical data sheet.

Main features

• One-component, moisture-curing polyurethane sealant.
• Non-sag consistency for easy application on vertical and overhead joints.
• Specifically formulated for marine use on boats and ships.
• Forms a highly elastic, vibration-resistant joint.
• Low odour and solvent-free formulation with very low VOC and isocyanate content (per manufacturer data, not independently verified).
• Non-corrosive; suitable for use on common marine metals when correctly pre-treated.
• Can be painted once cured (paint compatibility and preparation must be checked case by case).
• Bonds well to a wide variety of typical marine substrates such as GRP/gelcoat, fibreglass, metals and wood (based on manufacturer and distributor information).
• Wheelmark approved and compliant with IMO low spread-of-flame requirements for marine safety (according to published product data, not independently verified).
• Based on distributor information, it is used both above and below the waterline and offers resistance to salt water (this point is not directly verified from the manufacturer’s datasheet).

Technical specifications (summary)

The values below are general characteristics drawn from public product descriptions and safety data; they may vary by country/version and are not guaranteed. For exact figures (density, shore hardness, tensile strength, movement capability, skin time, full cure time, temperature resistance, etc.), consult the current official product data sheet for your region.

• Chemistry: Polyurethane sealant.
• Curing mechanism: Moisture-curing (iCure system) forming an elastic sealant.
• Components: 1-component, ready to use.
• Consistency: Non-sag paste suitable for vertical and horizontal joints.
• Typical application areas: Marine sealing and light-duty bonding on boats and ships (above and, according to distributors, also below the waterline; this specific claim is distributor-based and not manufacturer-verified here).
• Approvals (not independently verified):
  • Meets IMO low spread-of-flame requirements for marine applications.
  • Wheelmark approved (marine safety marking for certain shipboard materials).

Applications and use cases

Sikaflex 291 iCure is designed as a multifunctional marine sealant and light-duty adhesive. Typical uses described in public sources include (examples only, not exhaustive):

• Elastic, vibration-damping sealing joints in boatbuilding (interior and exterior).
• Sealing and bonding in GRP/gelcoat hulls and decks.
• Sealing joints between deck and hull (deck-to-hull bonding lines) according to distributor use cases.
• Sealing around keel/hull interfaces and stern tube areas (as described by distributors; always verify suitability for permanent immersion in your specific case).
• Sealing of deck hardware and fittings (e.g. rail bases, cleats, hatches) when appropriate surface preparation and design are followed.
• Interior sealing in cabins, lockers and technical compartments on board.
• General-purpose sealant for marine repairs where an elastic, paintable joint is required.

The exact suitability for each application (especially for critical structural joints or permanent underwater exposure) must always be confirmed against the latest official product data and design guidelines.

FAQ – Sikaflex 291 iCure

1. Is Sikaflex 291 iCure the same as Sikaflex-291i?

Public product listings describe Sikaflex 291 iCure as the updated curing-system version of Sikaflex 291, marketed as Sikaflex-291i. In practice, "Sikaflex 291 iCure" and "Sikaflex-291i" are generally used for the same marine adhesive sealant. Always check the packaging and local data sheet to confirm the exact product you are using.

2. Can I use Sikaflex 291 iCure below the waterline?

Some distributors state that Sikaflex 291 iCure is used above and below the waterline for marine sealing. This specific claim is not verified here directly against the manufacturer’s technical data sheet. Before using it for permanent underwater joints, consult the current official data sheet and, if needed, the manufacturer’s technical support to confirm suitability and any limitations.

3. How long does Sikaflex 291 iCure take to cure?

Cure time depends on joint thickness, temperature and humidity. As a moisture-curing polyurethane, it skins over and then cures through from the outside inward. Typical data (skin time, cure rate per 24 h, full cure time) are not listed here and must be taken from the latest official product data sheet for your climate and joint dimensions.

4. Is Sikaflex 291 iCure paintable?

According to manufacturer information, Sikaflex-291i can be overpainted once sufficiently cured. Paint compatibility, required surface preparation and waiting time depend on the specific coating system. Always follow the coating manufacturer’s recommendations and carry out a small compatibility test where possible.

5. What substrates does Sikaflex 291 iCure bond to?

Public data indicate good adhesion to many marine substrates such as gelcoat/GRP, fibreglass, metals and wood, provided they are properly cleaned and pre-treated. Exact preparation (cleaner, activator, primer) must be checked in the official Sika pre-treatment charts and product data sheet for your region.

6. Is it suitable as a structural adhesive?

Sikaflex 291 iCure is primarily a sealant with elastic properties and limited adhesive strength, typically intended for sealing and non-structural or lightly loaded bonding tasks. For structural bonding, consult Sika’s dedicated structural adhesives and use the official technical documentation to select the correct product.

7. What is the difference between Sikaflex 291 and Sikaflex 291 iCure?

Distributor descriptions indicate that Sikaflex 291 iCure is a later version of Sikaflex 291 with a modified curing system (iCure). The result is a one-component marine sealant with similar intended use but an updated curing technology. For exact performance differences and compatibility, only the latest official technical data sheets provide authoritative information.

8. Can I sand Sikaflex 291 iCure after curing?

Some distributors mention that Sikaflex-291i is sandable after full cure. This detail is not independently confirmed here against the manufacturer’s data. Sandability depends on full cure, joint geometry and the abrasive method used. If sanding is critical for your application, verify this property in the official literature or through a practical test on a sample joint.

9. Is Sikaflex 291 iCure solvent-free?

Manufacturer product descriptions state that Sikaflex-291i is solvent-free with very low VOC and low isocyanate content. These statements are based on public information and are not independently tested here. For regulatory or certification purposes, rely only on the current official product and safety data sheets.

10. Where can I find exact technical values (strength, temperature resistance, etc.)?

The precise numerical values (e.g. tensile strength, elongation at break, shore hardness, application temperature range, service temperature range) are available only in the official technical data sheet and safety data sheet for Sikaflex 291 iCure/Sikaflex-291i in your country. For any engineering or safety-relevant decision, always base your design on those official documents.

Section 14 – Transport information (summary)

The following is a simplified summary of Section 14 of various Sikaflex-291i Safety Data Sheets. National versions of the SDS may differ slightly, so this information is indicative only and must not replace the full, current SDS.

• UN number / ID number: Not regulated as a dangerous good under ADR (road), IMDG (sea) and IATA (air).
• UN proper shipping name: Not regulated as a dangerous good (no specific UN shipping name assigned).
• Transport hazard class(es): Not classified as a dangerous good for transport by road, sea or air.
• Packing group: Not applicable, as the product is not regulated as a dangerous good for transport.
• Environmental hazards: Listed as “not regulated as a dangerous good” with respect to environmental transport hazard; nonetheless, releases to the environment should be avoided and normal good practice for chemicals should be followed.
• Special precautions for user: Generally indicated as not applicable for dangerous-goods transport purposes. Normal precautions for handling chemical products (e.g. preventing leakage, securing containers) still apply.
• Transport in bulk (IMO instruments, MARPOL/IBC): Not applicable for the product as supplied (usually delivered in cartridges or small containers).

Always check the latest Safety Data Sheet edition applicable to your country and mode of transport to confirm regulatory status and any special national provisions.

Section 8 – Exposure controls and individual protection measures (summary)

The points below summarise typical guidance from Sikaflex-291i Safety Data Sheets for Section 8 (Exposure controls / personal protection). Specific national OELs (occupational exposure limits) and recommended PPE can vary by country, so treat this as general guidance only and always follow the current SDS valid in your jurisdiction.

8.1 Exposure controls – engineering and environmental controls

• General ventilation: Use good general ventilation during application to keep airborne concentrations of any vapours or aerosols as low as reasonably achievable.
• Local exhaust: In confined spaces or where ventilation is insufficient, additional local exhaust ventilation may be required to control exposure, especially when tooling or cleaning with solvents is involved.
• Environmental exposure controls: Prevent uncontrolled release to drains, waterways or soil. Spills and residues should be collected and disposed of according to local regulations for chemical waste.

8.2 Individual protection measures – personal protective equipment

The specific PPE required depends on the actual working conditions (ventilation, exposure duration, method of application). As a general summary from public SDS information:

• Hygiene measures: Wash hands, forearms and face thoroughly after handling and before eating, drinking, smoking or using the toilet. Remove contaminated clothing and wash it before reuse. Ensure access to eye-wash facilities and, where feasible, a safety shower in areas where product is handled in bulk or over extended periods.
• Eye/face protection: Wear safety glasses with side shields or chemical splash goggles conforming to an appropriate standard whenever there is a risk of splashes or contact with liquid product.
• Hand protection: Wear suitable chemical-resistant gloves (material and breakthrough time must be selected based on local SDS recommendations and the duration of contact). Inspect and replace damaged or degraded gloves regularly.
• Skin and body protection: Use appropriate protective work clothing (e.g. long sleeves, long trousers or coveralls) to avoid repeated or prolonged skin contact. In more intensive operations, an apron or additional protective garments may be advisable.
• Respiratory protection: Under normal open-air or well-ventilated conditions, respiratory protection is often not required. In poorly ventilated areas, confined spaces or where exposure limits could be exceeded, use an approved respirator suitable for organic vapours and/or particulates, selected according to the local SDS and risk assessment.

Note: Some Sikaflex-291i SDS versions specify exposure limits for certain isocyanate components and emphasise the potential for sensitisation. Employers must consult the full SDS for their country, assess exposure in the workplace and select PPE and engineering controls accordingly.

Important: All technical, transport and safety information above is a non-exhaustive summary based on publicly available documentation at the time of writing and is not fully verified. For design, regulatory compliance, workplace safety assessments and transport classification, always consult the latest official technical data sheet and safety data sheet for Sikaflex 291 iCure/Sikaflex-291i applicable in your country.