For structural timber joints, boat building, and demanding exterior installations where a completely waterproof bond is required, Unobond FC Polyurethane Adhesive provides a fast-setting, moisture-curing polyurethane bond. Fully cured, this single-pack adhesive achieves a D4 water-resistance classification, making it suitable for marine environments and exposure to severe weather.
Unobond FC is a moisture-curing adhesive that requires atmospheric humidity or moisture within the substrates to activate the curing process. During assembly, the adhesive foams and expands slightly, forcing its way into surface irregularities and gaps to maximise the overall contact area of the joint. When applied between tight-fitting substrates, the adhesive cures to an invisible bond line that can be painted over with acrylic, oil, or rubber-based paints once fully cured.
Unobond FC bonds porous to porous, or porous to non-porous substrates, provided at least one of the mating surfaces contains moisture. Suitable substrates include:
All mating surfaces must be structurally sound, dry, clean, and free of grease, oils, curing compounds, or release agents. Concrete must be cured for at least 28 days prior to application. Metal surfaces should be lightly sanded and wiped down with Adheseal Xylene solvent.
At least one of the substrates must have a minimum moisture content of 8% to trigger the cure. In dry, cool conditions or when bonding non-porous surfaces, a light mist of water can be sprayed over the opposing surface before assembly. Apply the adhesive between 5°C and 35°C, keeping the bead approximately 10mm in from the edge to minimise squeeze-out. Tool with a spatula within the 10-minute skinning window, bring the surfaces together immediately, and clamp tightly.
Required clamping pressures:
Allow any squeeze-out adhesive to dry completely before removing it with a sharp blade. Attempting to remove wet squeeze-out will spread the adhesive and stain the surrounding surface. Cured adhesive can be machined, sanded, or cut without blunting tools or clogging sandpaper.
Yes, Unobond FC is rated D4 for waterproof bonding. It withstands a 72-hour boiling water test, confirming its suitability for marine and demanding exterior applications where water exposure is constant.
Yes, consistent clamping or firm pressure is essential for maximum bond strength. Maintain pressure for at least 60 minutes at 23°C and 50% relative humidity, applying 50 PSI for softwoods and 150 PSI for hardwoods.
No, Unobond FC is an adhesive, not a primary gap filler. Using it as such reduces the structural strength of the bond. For gap filling, dedicated products like Adheseal GapFilla are more appropriate.
Apply Unobond FC at temperatures between 5°C and 35°C. Crucially, at least one of the bonding surfaces must have a moisture content of at least 8% for proper cure activation.
| Application | Key benefit | Primary trades |
|---|---|---|
| Structural timber bonding for exterior and marine environments | Achieves D4 waterproof rating, survives 72-hour boiling water test, resists low temperatures for durable performance. | Boat builders, exterior carpenters, joiners |
| Bonding diverse construction materials (metal, wood, concrete) | Develops 5 N/mm² tensile strength. Adheres to porous and non-porous substrates, non-corrosive to galvanised and zinc-coated steel. | General builders, fabricators, metalworkers |
| Installation of floor mouldings, skirting boards, and sub-flooring | Fast 1-2 hour setting time allows quick progression. Slight expansion fills minor substrate irregularities, contributing to a secure fix. | Finish carpenters, flooring installers |
| Manufacturing of furniture and cabinets | Delivers strong, resilient bonds with invisible glue lines in close-fitting joints. Low VOC content supports indoor air quality requirements. | Cabinet makers, furniture manufacturers |
Correct surface preparation is essential for structural bond strength and long-term durability.
Ensure substrates are structurally sound, stable and free from dust, loose or friable material, oils, grease, curing compounds and other contaminants. Allow new concrete to cure for at least 28 days before bonding and remove surface laitance by mechanical means if necessary.
Lightly abrade metals and dense surfaces, then use the two-wipe method with a suitable solvent such as xylene and fresh cloths. Replace cloths regularly to avoid spreading contamination back over the surface.
The liquid format of Unobond FC allows efficient coverage across large areas when spread correctly.
Open the drum and use appropriate dispensing equipment or a decanting process to apply adhesive onto one of the bonding surfaces. Keep the adhesive band approximately 10 mm in from external edges to minimise squeeze-out.
Use a spatula or suitable spreader to distribute Unobond FC evenly, targeting a glue line of approximately 0.1–0.25 mm (maximum 0.5 mm). Ensure complete coverage without pooling.
Firm, even pressure across the joint ensures structural performance and predictable results.
Bring the bonding surfaces together immediately after spreading and clamp tightly and evenly. Generate enough pressure to close joints and see some controlled squeeze-out along the edges.
Maintain clamping pressure for at least 60 minutes at 23°C and 50% RH with a pressing load of roughly 0.6 N/mm². Full cure is typically reached after about 24 hours, although low temperatures and humidity will slow the reaction.
Good cleanup and storage habits protect tools, maintain product quality and keep sites tidy.
Clean tools and fresh spills with xylene while the adhesive is still wet. Once cured, Unobond FC can only be removed mechanically by scraping or sanding.
Use appropriate hand wipes for skin cleaning and avoid solvent-based skin cleaners. After use, reseal the drum lid securely to limit exposure to air and store between 15°C and 25°C in a cool, dry place.
Warning: Hazardous chemical. Non-dangerous goods. Poison Schedule S5. Caution.
Wear overalls, gloves (Nitrile Rubber recommended for intermittent contact), safety glasses, and a respirator if inhalation risk exists. Use an organic vapour/particulate respirator meeting AS/NZS 1715 and AS/NZS 1716 standards.
Ensure adequate ventilation to maintain air concentrations below exposure standards. Use in well-ventilated areas, or with local exhaust ventilation.
Store in a cool, dry, well-ventilated place, out of direct sunlight and away from foodstuffs. Keep containers closed when not in use and check regularly for leaks. Dispose of contents and containers in accordance with local and national regulations.
Proper surface preparation and moisture management are critical for Unobond FC to achieve its full structural bond strength and D4 water resistance.
Surface prep: Ensure surfaces are structurally sound, dry, clean, and free of dust, oils, or grease. One bonding surface must contain a minimum of 8% moisture to activate curing.
Primer: Not required. The product uses substrate moisture for curing.
Surface prep: Surfaces must be structurally sound, dry, clean, and free of dust, oils, or form release agents. Concrete must be cured for at least 28 days to prevent adhesion issues. One bonding surface must contain a minimum of 8% moisture.
Primer: Not required. The product uses substrate moisture for curing.
Surface prep: Lightly sand metal surfaces to improve adhesion, then wipe with Adheseal Xylene solvent to remove contaminants. Ensure the mating substrate provides the necessary moisture for cure.
Primer: Not required, but Xylene cleaning is a necessary preparation step.
| Property | Value |
|---|---|
| Type of Product | Polyurethane Adhesive |
| Curing System | Moisture |
| Cure Time | 24 Hours |
| Density (Specific Gravity) | 1.085 ±0.02 g/cm³ |
| Pressing Time | 1 hour @ 0.6 N/mm² |
| Tensile Strength | 5 N/mm² |
| Tear Resistance | Up to 130 kg/cm² |
| Application Temperature | 5°C to 35°C |
| Service Temperature | -30°C to 100°C |
| Working Time | 15 minutes @ 23°C & 50% RH |
| Skinning Time | 10 minutes @ 23°C & 50% RH |
| Volatile By Volume | <1% |
| Shelf Life | 12 months in original packaging |
| Storage | Cool and Dry between 15°C and 25°C |
| Resistance | Insensitive to Frost, Sensitive to Humidity (cures product), Uninflammable |
| D Classification | D4 water-resistant bond |
| Colour | Blueish |
| Packaging Description | 6kg pail |
| Total VOC | <0.1% |
Here are some common examples on where Adheseal Unobond FC Polyurethane Adhesive used by our customers.
