A single pack waterproof polyurethane adhesive
Purbond is a new adhesive manufactured by BoatCraft Pacific for bonding timber, semiporous and non-porous surfaces. Features of Purbond are
* high adhesive strength
* no long term creep in stressed joints
* suitable for use on damp surfaces
* can be applied direct from the bottle
* application is to one surface only, coverage 200 - 250 ml per square metre
* 100% waterproof, withstands 72 hour boiling water test
* sets in 1 - 2 hours, fully cured in 24 hours
* invisible in close fitting glue lines
* contains no volatile or flammable ingredients
* sands easily and does not blunt cutting tools
Purbond is a moisture curing, 100% solids, polyurethane adhesive. It reacts with surface moisture on any substrate, especially semiporous materials, which initiates its curing reaction. In the process of this reaction, Purbond foams and expands slightly, forcing its way into gaps, unevenness, or pores on each of the mating surfaces, thus enhancing the contact area of the joint. It has high shear strength and is creep resistant.
Purbond can be used for bonding most materials including timber, plywood, fibre and particle boards, foamed plastics, concrete, even metals. While a strong bond will be formed to most substrates, it may not be structural with all materials. The bond is stronger than all timbers softer than pine and oregon, especially Western Red Cedar, and breaks the timber grain of them. Harder timbers will be bonded with equal strength, but the glue line may break before the timber. In test pieces we have obtained 100% wood failure with hard timbers such as Rosewood and Tasmanian Oak.
Purbond is recommended for wooden boat building applications including both timber laminating and cedar strip planking, where its ease of use will be particularly appreciated. It is suitable for all interior and exterior joinery and fitting out, and wherever surfaces are imperfectly mated. It is not recommended for gap filling of open joints, where the glue can expand out of the joint, or for joints subject to forces of peel or direct tension. For such applications, use Bote-Cote® Epoxy adhesive.
PREPARATION AND APPLICATION
Surfaces to be bonded must be sanded, clean, and free from dust, grease or other contaminants. Timber and concrete generally have adequate surface moisture to initiate cure. Other dry surfaces may be dampened with water before application by wiping with a damp cloth.
Apply Purbond directly from the bottle to one surface only. Spread with a scraper to a thin layer, then join and clamp the parts. Application rates will vary with the roughness of the surface. On an average surface, coverage will be 200 - 300 ml per square metre. Clamps may be removed when the exudate is hard, generally after 2 - 3 hours unless temperatures are very cold. At temperatures below 10 deg C, allow 5 - 6 hours for cure.
Some adhesive will expand out of the joint. It is best left to harden, and cut off or sanded after it has cured. Purbond sands easily without clogging the paper. It does not blunt cutting tools such as chisels and planes.
SOME USES OF PURBOND
Purbond is most effective in sliding type
(“shear”) joints, but is less effective in peel or tensile joints. Some
examples of its best usage are:
Mortise and tenon and biscuit joints
Bonding plywood e.g. to make thick ply panels, or to timber reinforcing strips
Laminating bench tops
Boat building using cedar strip planking
Glueing to aluminium
Glueing to concrete
Glueing Stainless Steel to MDF and Plywood
Glueing foams including expanded polystyrene, PVC, polyurethane, or polyethylene
PURBOND FOR CEDAR STRIP PLANKING
Purbond is especially useful for the Strip Planking method of boat building, and great efficiency will be obtained by using it with Quickstrip profiled strips.
Assemble Quickstrip planks onto the boat with the tongue uppermost. Place each fresh strip in a glueing jig with its groove uppermost, and simply run a bead of Purbond along the groove direct from the bottle. Spread the bead out into the groove with a suitably shaped wooden spatula. Then flip the strip over, and mount it onto the tongue of the previously fitted strip. Fasten at each station in the usual way, nailing into the upper half of the strip to force it down onto the station.
STORAGE AND HANDLING
Purbond is moisture sensitive, and containers must be kept sealed after use. If left unsealed, a skin may form, but the rest of the product will remain useable. If the bottle is stored upside down, this skin will then be at the bottom, and cannot prevent Purbond being squeezed out of the bottle. Shelf life is at least one year.
Always wear rubber gloves when using Purbond. Contact with the skin will cause temporary blackening which cannot be removed by washing. Prolonged contact may induce allergenic reactions such as rashes or breathing congestion in sensitive people.
Clean up with most solvents such as acetone. Do not thin Purbond with solvents.
PROPERTIES OF PURBOND
Chemical type Moisture curing polyurethane
Colour Honey colour
Solids content 100 %
Specific Gravity 1150 kg/m3
Viscosity 3000 mPa.sec
Spread rate 200 – 300 gm per m2
Open time 45 – 60 minutes
Set time 2 hours
Full cure time 24 hours
Temperature resistance 120 Deg C
Boil resistance 72 hours
Flammability Non flammable
Flash Point >200 Deg C
Shear strength exceeds 10 MPa
Please call Boatcraft Pacific 07 3806 1944 ( +617 3806 1944) for how to contact your nearest reseller.
Copyright Boatcraft Pacific Pty. Ltd.