Adheseal Hi-Flex 50 Hybrid MS Polymer Sealant

For sealing construction joints, prefabricated concrete panels, and forming critical bond breakers under waterproofing membranes, Hi-Flex 50 Hybrid MS Polymer Sealant provides primeless adhesion and high movement capacity without the risk of gassing or bubbling, even in high humidity.

What it does

Hi-Flex 50 is a neutral-cure, moisture-curing MS Polymer hybrid sealant that combines elastomeric flexibility with high UV and weathering resistance. The formulation cures by reacting with atmospheric humidity to form a permanently elastic joint seal. Because it contains no isocyanates, solvents, or acids, it is non-corrosive to galvanized steel, zinc-coated steel, and concrete. It incorporates biological inhibitors to resist mould and fungal growth in hot, humid environments, and is compatible with Adheseal Everflex membranes including Aqua-Ban, WPM, WPUV, and SMP.

Numbers that matter

• ±25% movement capability: Tested to ASTM C719, allowing the joint to accommodate thermal and structural expansion and contraction without adhesive or cohesive failure.
• 3.0mm per 24 hours cure rate: Standard moisture-cure window at 25°C and 50% relative humidity, with a quick 10-minute tooling skin time.
• -40°C to 100°C service temperature: Maintains structural flexibility and joint integrity across extreme environmental exposure.
• 35 Shore A hardness: Measured under ASTM D2240, offering a balanced, medium-modulus resistance suitable for foot traffic and general joint protection.
• 200% elongation at break: Tested to ASTM D1412, confirming high elasticity under tensile strain before material rupture.

Where to use it

Hi-Flex 50 adheres to most common building materials without staining or bleeding. Suitable substrates and applications include:

• Waterproofing: Serving as a fillet sealant and bond breaker under selected Everflex waterproofing membranes.
• Substrates: Masonry, fibre cement board, brick, aluminium, powder coat, concrete, timber, plaster board, stone, rubber, fibreglass, porcelain, and plastics.
• Assembly & Fabrication: Seam sealing, bolted lap joints, prefabricated concrete panels, aluminium fabrication, acoustic ceiling tiles, display signs, and lightweight component bonding.

Limitations

• Water immersion: Not suitable for continuous submersed environments or internal swimming pools where high chlorine concentrations exist.
• Cure restrictions: Do not use in totally confined spaces; the polymer requires atmospheric humidity to cure.
• Substrate compatibility: Do not use on lead, copper, brass, titanium-zinc, bituminous surfaces, natural rubber, or EPDM. Avoid contact with materials leaching oils, plasticisers, or solvents.
• Stone staining: Perform a stain-testing program before application on any natural stone. Adheseal S100 is recommended for marble and granite.
• Glazing limits: Not suitable for structural glazing; use N-80 or N-60 glazing silicone instead. Do not use for adhering mirrors.
• Bubbling risks: Avoid application when moisture-vapour transmission is active or emanating from the substrate, as this may trap gas and cause bubbling.
• Chemical exposure: Do not expose the sealant to cleaning agents, solvents, or alcohols during its curing phase.

Installation and joint design

Joints should maintain a 2:1 width-to-depth ratio. Internal joints require a minimum width and depth of 5mm, while external joints require a minimum width of 12mm. For joints deeper than 10mm, insert an open-cell backer rod 25% larger than the joint width. If using a closed-cell backer rod, do not damage its outer skin, as punctured closed-cell backing can cause gassing and bubbles in the curing sealant.

For porous substrates such as concrete, aerated concrete, bricks, and mortars, prime with Everflex Supaprime. For non-porous metals and plastics, slightly roughen the surface and pre-treat with Adheseal 50A surface prep. Allow primers to dry for at least 30 minutes but no more than 2 hours before gunning the sealant.

When used as an adhesive, apply a triangular bead by holding the nozzle at 90° to the surface. Compress the adhesive bead to no less than 2mm thickness to ensure adequate wet transfer and bond-area contact.