Hot tack - Hot seal strength testing of thermoplastics, per ASTM F-1921 method B.

Intertek evaluates product seal strengths by performing Hot tack testing according ASTM F1921 (method B). Hot tack measures the strength of heat seals formed between thermoplastic surfaces of flexible webs, immediately after the seal has been made and before it cools to room temperature. This heat seal property is important since this situation occurs on vertical form-fill-seal packaging.

In the heat sealing process, contents are dropped into the bag immediately after the horizontal seal bars have opened. Since the content can be heavy, the hot seal must be able to withstand high loads, thus requiring a high hot tack force. This measurement will be of influence while upgrading packaging materials or packing production processes.    

Hot tack testing provides:

  • Threshold sealing temperature, the minimum temperature at which the required hot tack strength is reached
  • Seal strength, which is the maximum peak force
  • Hot tack temperature range, the temperature range in which the required hot tack strength is obtained
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