PUR hot melts set on cooling for fast handling, then react with moisture over hours to days and become crosslinked, so the final bond resists heat, solvents and creep far better than a standard hot melt. They are used for edge banding, profile wrapping, bookbinding and electronics. Unused adhesive cures in the equipment if exposed to air, so systems are purged and sealed carefully.
Book line runs PUR so the spines don't crack in the cold, but we purge the tank every weekend.
Also heard as
- reactive hot melt
- RHM
- PUR hot melt
Related terms
Hot melt
A solid thermoplastic adhesive melted in a tank or gun, dispensed hot and set within seconds as it cools.
Moisture cure
A cure triggered by humidity in the air or on the parts, used by silicones, urethanes and silane polymers.
Polyurethane adhesive
An adhesive based on isocyanate chemistry that cures into a tough, somewhat flexible bond.
Purge
To run adhesive through a mixer or dispense valve and discard it, clearing old, unmixed or off-ratio material.