What is the hot tack test method?

Hot tack testing FAQs

Interested in finding out more about hot tack testing? Got a question about how it fits into your testing process? Read on for the answers to all your burning hot tack and heat seal testing questions.

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What is hot tack testing?

Hot tack testing is a way of determining the strength of a heat seal, while it is still hot. Heat seals are frequently used in flexible packaging, particularly for ensuring an airtight seal for products that need to stay fresh and free from contamination. This means it’s particularly important for the food and pharmaceutical industries, but it is used in lots of other sectors as well.

Which ASTM standard does hot tack testing comply with?

Hot tack testing can comply with ASTM F1921, the standard test method used to evaluate the hot seal strength of packaging material. For the test to be compliant, it must be applied immediately after the seal has been made and before it has a chance to cool to room temperature.

How is a hot tack test validated?

A hot tack test is validated by measuring how well the seal is able to withstand force. This is important in determining the ability to the seal to withstand the kind of weights and pressures it will encounter during its lifespan. The temperature range of the hot tack is also measured, so performance can be validated at a range of different heats.

Which products offer hot tack testing?

There are a variety of machines that offer hot tack testing. Our recommended choice is the 75-50 Heat Sealer and Hot Tack Base, which provides a range of critical information needed to determine ideal sealing conditions for packaging films. It is also compliant with ASTM F1921 standards.

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What other types of seal strength testing are there?

There are several other types of seal strength testing that are ideal for flexible packaging. Some of the most important include the tensile strength testing and burst or creep testing, both of which can help you determine how well your seal performs in a variety of conditions. For more insights into the various ways to improve your QA, check out our guide to flexible packaging testing.

Seal strength and flexible packaging testing with Industrial Physics

With a huge range of testing instruments and many years of experience in the flexible packaging field, the Industrial Physics team is ready to help you find the testing solutions you need. Know you can trust in the integrity of your products, with full scale testing solutions. For more information on how we can help, get in touch

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:

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• 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