HT-2PC Automatic Hot Tack Tester

HT-2PC Hot Tack Tester is a highly technical instrument designed to measure the ‘Hot Tack Seal Strength’ of flexible packaging materials. It follows the principles of ASTM F1921 Standard Test Method for Hot Seal Strength (Hot Tack) of Thermoplastic Polymers and blends comprising the sealing surfaces of flexible webs.

What is Hot Tack Seal Strength?

Hot Tack Seal Strength is a measure of the strength of a hot heat seal tested within milliseconds after heat sealing. On production packs, newly formed hot seals are frequently exposed to disruptive forces, such as when contents are dropped into the pouch. These force act on the hot seal and if there is inadequate resistance they can break all or part of the seal. Therefore it is essential to measure the amount of stress the seal can withstand.

The HT-2PC has been designed to test the hot seal strength under accurately controlled conditions, simulating the stresses a pack is exposed to on a high speed packaging line. A heat seal that has cooled to ambient temperature will reach its maximum seal strength after several minutes or even hours. Measuring strength of cooled seals prepared on a Lab Heat Sealer and tested on a separate Tensile Tester does not correlate with the strength of a hot seal.

Principle of Operation

HT-2PC Automatic Hot Tack Tester replicates the heat sealing processes employed on automatic packaging lines in particular VFFS packaging machines, combined with a high speed tensile tester.

The operator chooses (or creates) a ‘parameter template’ from the library which sets the machine to test at defined values for temperature, pressure, dwell time, cooling time and peeling speed. The template can be a Single Test, Replicate Test, Sequential Test or Seal Initiation Test. These are then loaded to the ‘Playlist’. Film is loaded either manually for a single test, or a long strip is wound onto the film feeding device.

Once the playlist is started everything is sequenced automatically. The film is pushed into the sealing jaws, and is clamped. The hot sealing bars close to the desired pressure and after the dwell time elapses the jaws open. Next, the programmed cooling time runs down and then the sealed film is peel open at the test speed. All measurements of the seal properties are recorded at high speed to ensure transient forces are captured accurately. The results are displayed and saved automatically on the industrial pc, and saved for later recall, reporting or export to other software. The playlist then increments to the next test, the film is indexed to the next position and the test sequence starts again.

Parameter Templates

Parameter templates are used to load the required test settings. These are Single Test, Replicate Tests, Sequential Tests or Seal Initiation Tests. PLC control of all the parameters enables simulation of production packaging machines. A wide range of setting for each parameter enables testing of various materials to suit each application:

• Sealing temperature for top and lower sealing jaws, set individually.
• Sealing pressure
• Sequence timers for Delay Time, Dwell time, and Cooling Time
• Peeling speed
• Output configuration

Automatic Film Feeding Device

The Film Feeding Device is conveniently located in the front panel allowing easy use and access to the most frequently used parts. The clamps are easily loaded and clamp the film automatically once the test has been activated. Vertical movement of the lower clamp is controlled by an electric motor that enables accurate positioning and speed control through an encoder. The film folding devices sets the film up ready for sealing and the sealing is made through The sealing bars incorporate the heating element and sensors to complete the feed back loop of the PID temperature control.

Data Capture

The software is designed to be user friendly with drop down menus and easy key-strokes. The software is con-trolled through the touch screen (or keyboard and mouse) for parameter setting, measuring and data recording and storing for later recall. The software enables efficient use of the instrument by any person involved in testing, from production machine operators to quality control and R&D personnel. Report-ing is via a clear easy to read graphical media which shows each test and at the end of the test or series an overlay of test results.