A seal is a crucial aspect of flexible packaging, in fact in many other forms of packaging. Sealing is usually done by using adhesives. When sealing is done using adhesion, there are different factors to consider like dwell time, drying time, seal strength etc. If the drying time is too high, there are chances that seals may fail even before complete drying of the seal. To control the quality of the seal, different tests are performed. Peel strength or bond strength tester is commonly performed. But there is one important test, which often get skipped and that is hot tack testing. In this test, the strength of seal is checked when it is not dried completely. This ensures that packing does not fail in the packing line.

The best method to perform this test is to use Hot Tack Tester. This is a standardised testing equipment in which a sealed is formed first and separated immediately. It helps in measuring the capacity of adhesives to form the bond with the surface of another material when it comes in contact with the substrate. This test is very important in filling line of the flexible packing. If the seal strength becomes weak, the penetration of air inside the packet may spoil the content. It is usually performed on the pressure sensitive adhesives.

It is important to check the seal strength because, in the filling line, the contents are filled immediately in the packet once it is sealed from the one side. At this point of time, the packet should be able to bear the weight of the materials, be it light or heavy. The seal should not fail as it is already designed as per the intended application.  

Testing Procedure
Depending upon the intended working conditions, a heat sealer is incorporated into the machine. This sealer creates a seal using the heat sealing technique. As soon the seal forms, a tensile strength is applied on the sample to separate the bond created. The tensile strength is applied when the seal is not even dried. The test is performed during the drying time taken by the bond to form.


Hot tack tester comes with a bright digital LED display that shows the force required to separate the bond when it is drying.

Labtiger’s Hot tack tester’s design is complying with international testing standards which makes the tested products accepted worldwide. It is now becoming one of the most used instruments in the packaging industry.