Adheseal PU25 Polyurethane Adhesive

Adheseal PU25 FC is a medium-modulus, fast-curing polyurethane sealant and adhesive for expansion joints, precast and tilt-up panels, pavement joints, window perimeters, curtain walls, metal cladding and general construction sealing. It combines ±25% movement capability with a firmer Shore A 25 cured profile, making it a versatile middle ground between the softer PU15 and the high-modulus PU50.

PU25 is designed for contractors who need one polyurethane sealant to cover a broad range of construction and fabrication work. It adheres to common porous and non-porous building materials, remains permanently elastic after cure and can be used internally or externally. Once fully cured, it is also suitable for below-waterline applications and has been tested for contact with potable water to AS/NZS 4020.

Fast-curing polyurethane sealant for expansion and construction joints

PU25 FC is particularly suited to expansion and connection joints where movement, toughness and faster site progression are important. Typical applications include precast and tilt-up panel joints, concrete and masonry connections, pavement joints, car parks and driveways, metal cladding, bolted lap joints, seam sealing and aluminium fabrication.

It can also be used for window perimeter and curtain wall sealing. Glazing and aluminium contractors use PU25 where a medium-modulus polyurethane weatherseal is appropriate, but it should not be confused with a structural glazing adhesive.

Why choose PU25 FC?

• Medium-modulus performance: 0.4 MPa modulus at 100% elongation gives a useful balance between flexibility and cured firmness.
• ±25% joint movement: accommodates expansion and contraction in correctly designed movement joints.
• Shore A 25 hardness: firmer than PU15 while remaining flexible enough for moving construction joints.
• Greater than 400% elongation: provides substantial stretch under movement before failure.
• Fast-curing FC formulation: designed for efficient construction and sealing work.
• Potable water tested: suitable for applications requiring AS/NZS 4020 tested contact with drinking water.
• Below-waterline use: suitable for below-waterline applications once fully cured.
• UV and weather resistant: accelerated testing showed no chalking, cracking or yellowing under the stated test conditions.
• Paintable: can be overpainted with compatible acrylic, oil and rubber-based paints after adhesion testing.

Compatible substrates

PU25 bonds to common construction materials including concrete, masonry, brick, aerated concrete, cement-based renders and mortars, timber, aluminium, stainless steel, galvanised steel, powder-coated and painted surfaces, compatible plastics, porcelain, glazed tiles, rubber and fibreglass. Adhesion testing is recommended where substrate coatings or compositions vary.

Joint design and application

Apply PU25 to structurally sound, stable, dry and clean substrates free from dust, oils, grease, curing compounds and surface water. Concrete should cure for at least 28 days before application.

Movement joints should generally be designed at approximately a 2:1 width-to-depth ratio. Internal joints require a minimum width and depth of 5 mm, while external joints should be at least 10 mm wide. Maximum joint width is 30 mm and maximum depth is 15 mm. Use correctly sized backing rod on deeper joints to control depth and prevent three-sided adhesion.

For porous concrete, masonry and similar substrates, use Everflex Supaprime where priming is required. For aluminium, stainless steel, PVC, galvanised steel, powder coat and other demanding non-porous surfaces, lightly abrade where appropriate, clean thoroughly and use Adheseal 50A surface preparation where required.

Window and glazing applications

PU25 can seal window perimeter joints, curtain wall interfaces and aluminium construction joints where a flexible polyurethane weatherseal is required. Its medium-modulus profile makes it a tougher, more general-purpose option than PU15 for mixed construction work.

PU25 is not suitable for structural glazing. Where the sealant forms part of the structural glass-bonding system, use an approved structural glazing silicone system instead.

Important limitations

• Do not use in internal swimming pools with high chlorine exposure.
• Do not use in totally confined spaces where atmospheric humidity cannot reach the sealant.
• Do not use in aquariums, for mirror bonding or for structural glazing.
• Do not use on bituminous surfaces, natural rubber, EPDM rubber or materials that may leach oils, plasticisers or solvents.
• Do not use on lead or copper. Stain-test sensitive natural stone before use.
• Do not apply where active moisture vapour transmission may cause bubbling.
• Keep uncured PU25 away from cleaning agents, solvents and alcohol that may affect cure or colour.

PU15 vs PU25 vs PU50

PU15, PU25 and PU50 share the same broad polyurethane sealant family but are tuned for different joint conditions:

• PU15: low modulus and Shore A 15 for highly flexible window perimeter joints, curtain walls, façade weathersealing and movement-sensitive connections.
• PU25 FC: medium modulus and Shore A 25 for versatile construction sealing across expansion joints, precast, pavement, window perimeters and mixed-material joints, with potable-water testing and below-waterline capability once cured.
• PU50: high modulus and Shore A 45 for firmer, tougher joints, anti-pick applications and demanding high-contact areas.

Browse the full Polyurethane Sealants range for additional construction joint options.