Polyurethane adhesive is a one-part adhesive that’s typically applied as a liquid from the nozzle of a bottle. It rapidly becomes sticky but joints can be repositioned for several minutes. Generally, the full strength is reached after about 24 hours.

Polyurethane adhesives provides a gap-filling adhesive suitable for most materials. (Getty Images)
Different types of polyurethane adhesive cure to give varying degrees of flexibility — from hard and brittle to rubbery. The construction grades match the flexibility of wood and can also be sanded.
This type of adhesive is widely used within construction and other industries. It forms a strong bond between almost any materials whether it’s porous or non-porous. It also adheres well to wood, metals, concrete and brick, rubbers, cured epoxy, leather, tile, glass, and many plastics.
However, polyurethane adhesive is less effective on some plastics, such as polypropylene and polyethylene, waxy or oily surfaces, and coatings such as Teflon and silicone. Similar polyurethane expanding foams are also used for sealing large gaps and insulating.
Polyurethane adhesive is supplied as a liquid containing monomers. When exposed to normal atmospheric humidity the monomers polymerize to form thermoset plastic, bonding adjacent surfaces in the process.
Cyanoacrylate adhesive works in the same way but is only suitable for surfaces in extremely close contact. Polyurethane adhesive expands and foams during curing, allowing it to fill large gaps. However, bond strength greatly reduces as the gap size increases.
Polyurethane adhesive is a one-part adhesive that’s typically applied as a liquid from the nozzle of a bottle. It rapidly becomes sticky but joints can be repositioned for several minutes. Generally, the full strength is reached after about 24 hours.
Different types of polyurethane adhesive cure to give varying degrees of flexibility — from hard and brittle to rubbery. The construction grades match the flexibility of wood and can also be sanded.
This type of adhesive is widely used within construction and other industries. It forms a strong bond between almost any materials whether it’s porous or non-porous. It also adheres well to wood, metals, concrete and brick, rubbers, cured epoxy, leather, tile, glass, and many plastics.
However, polyurethane adhesive is less effective on some plastics, such as polypropylene and polyethylene, waxy or oily surfaces, and coatings such as Teflon and silicone. Similar polyurethane expanding foams are also used for sealing large gaps and insulating.
Polyurethane adhesive is supplied as a liquid containing monomers. When exposed to normal atmospheric humidity the monomers polymerize to form thermoset plastic, bonding adjacent surfaces in the process.
Cyanoacrylate adhesive works in the same way but is only suitable for surfaces in extremely close contact. Polyurethane adhesive expands and foams during curing, allowing it to fill large gaps. However, bond strength greatly reduces as the gap size increases.
Before applying the adhesive, both surfaces should be thoroughly cleaned. Polyurethane adhesive is very difficult to remove from skin and clothes, so gloves should be worn during its application. This type of adhesive should be applied to one surface and, ideally, the other surface should be slightly damp.
Although atmospheric humidity is typically sufficient to complete curing, some additional moisture is beneficial. The surfaces should then be clamped together until the adhesive has cured. Polyurethane adhesive will expand and foam during curing, which means it is normal for quite a lot to emerge from the edges of the joint.
This should not be removed until curing has completed. It can then be cut away with a sharp knife or scraped with a chisel.
Because atmospheric humidity causes polyurethane adhesive to cure, it has a short shelf life. It should be purchased in relatively small containers. The lid should always be placed on the nozzle between uses. It should also be stored upside down so that any curing occurs at the bottom of the bottle.
Filed Under: Adhesives • epoxies
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