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Hot Seal Strength (hottack) of Thermoplastics ASTM F1921 method B

Hot Seal Strength Tester
ASTM F1921 method B

Hottack 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 property is important since this situation frequently occurs on vertical form-fill-seal packaging. In this process, the 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 hottack force.

The film sample is fixed in the upper specimen grip which is connected to a load cell and the lower specimen grip which is connected to a peeling actuator. The film sample is inserted between the sealing bars by means of a specimen insertion mechanism. A seal is made under defined conditions of temperature, contact time and pressure. At the end of the sealing time, and after a preset delay time, the peeling actuator moves down with a preset speed and peels the hot seal totally apart. The maximum force required to peel or break the seal is the hottack force.

Specimen size:
A rectangular specimen is used. The specimen width may be either 25 mm, 15 mm or 1.00 inch. Specimen length must be between 250 and 350 mm.

The following data is obtained:
  • Treshold sealing temperature; this is the minimum temperature at which the required hottack strength is reached.
  • Seal strength, which is the maximum peak force.
  • The hottack temperature range, this is the temperature range in which the required hottack strength is obtained.

Equipment Used:
J&B Hottack tester model 4000

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**Please note that this test description is intentionally generic in nature and aimed at providing a descriptive summary to enhance test understanding. For more information please contact a Intertek PTL Technical Representative at . Due to copyright restrictions, we are not able to provide copies of standards. Standards can be obtained from appropriate standards authorities.

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