Once adhesive is on a part it begins to skin, cool, lose solvent or react. Open time is the window during which the mating part can still be placed and get a good bond. Hot melts may have only a few seconds; contact cements need a minimum drying time as well as a maximum. Exceeding open time is a classic cause of adhesive failure on the second surface.
Open time on the MMA is eight minutes, so no laying beads on the whole rack and then going to lunch.
Open time shortens in warm, dry or drafty conditions, so data sheet values measured at 23 C overstate it on a summer floor.
Also heard as
- open assembly time
Related terms
Pot life
How long a mixed batch of two-part adhesive stays usable before it thickens too much to apply.
Fixture time
The time until a bond is strong enough to handle or unclamp the assembly without moving the parts.
Hot melt
A solid thermoplastic adhesive melted in a tank or gun, dispensed hot and set within seconds as it cools.
Contact cement
An adhesive applied to both surfaces and left to dry before they are pressed together for an instant bond.