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International Standards

ASTM F 1921

Introducing ASTM F1921 - Industrial Physics

ASTM F1921 is the ASTM international standard test method to measure the heat seal - or ‘hot tack’ - strength of thermoplastic polymers and blends used for the sealing surfaces of flexible packaging products. 

This effective ASTM standard approach is designed for heat seal testing immediately after a seal has been made and before it cools to ambient temperature.

To undertake these tests successfully you’ll need a hot tack testing machine that can automatically heat seal a specimen and immediately determine its strength. Plus it must do this at a precisely measured time following the heat sealing cycle.  

Hot tack testing – operator don't touch!

A prerequisite of the ASTM F1921 approach is that the operator doesn’t influence the hot tack test after the sealing sequence has begun. You run the risk of this when you take a manual approach to hot tack testing as your results could be influenced by the operator’s technique. Therefore the ASTM F1921 standard doesn’t allow for non-instrumented manual procedures that use any combination of springs, levers, pulleys and weights.  

There are two variations within ASTM F1921 hot tack testing and they differ primarily in two respects:  

  1. The rate of grip separation during testing of the heat sealed specimen 
  2. Whether the testing machine generates the cooling curve of the material under test, or measures the maximum force observed following a set delay time. 

Both hot tack tests can be used to inspect the same materials and within the range and capacity of the machine employed.  

Hot tack and adhesion testing - stick with us!  

At Industrial Physics we’re pretty hot on hot tack testing! In fact, we’ve written an FAQ blog on the subject - just click right here to read.     

We trust we’ve shown it can be a sticky subject for your business if your testing processes are not up to scratch. So you’ll be pleased to hear that the IP team can help you with all of your adhesion testing needs. 

Full list of adhesion standards we can help you with, just click here!  

ASTM F1921 testing equipment  

So, how can Industrial Physics improve your ASTM F1921 testing? 

Across our portfolio of brands we manufacture several heat sealing machines and hot tack testing devices.  


The SL-10 hot tack tester & seal tester  

The most precise and consistent heat seal tester in the packaging industry! The testing capabilities of his heat sealer include heat seal testing and hot tack testing. The SL-10 provides critical information needed to determine ideal sealing conditions for packaging films. 

The TS-12 heat sealer machine

The TS-12 is one of the most precise and consistent table top sealers available, perfect for laboratory heat sealing applications. This digitally controlled heat sealer produces heated crimp seals for flexible packaging materials.  


Your global test and inspection partner for ASTM F1921