Setting Rate

Determining the Open Time and Setting Time of Hot Melt Adhesives (PAPT II Instrument)

For hot melts, open time (see below) is often very short. It is important to match the open time of the adhesive with the requirements of the process and conditions. A hot melt with an open time of 1-2 seconds in an application where it takes 4-5 seconds to form the bond after the adhesive has been applied would give poor wetting of the second substrate and a poor bond.

However, short compression times are the very essence of hot melt bonding processes and the situation can arise where the adhesive is still liquid when compression is removed and stresses on the joint may then force the substrates apart (eg tray erection, carton sealing).