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Theller
Engineering
707-762-3820
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MEASURING HOT TACK with MECHANICAL ATTACHMENTS
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Until the late 1980'S hot tack was measured exclusively using non-instrumented
mechanical accessories or attachments to conventional laboratory heatsealers. The
attachments/accessories employed variously springs, levers, pulleys, weights, etc.,
depending on the design, but were all intended to simulate the immediate stressing of a
newly-formed heatseal in a vertical form-fill packaging machine, and to measure the
amount of force required to peel the hot seal. In the US the two most popular methods
were the DuPont spring (accessory), and the Frito Lay attachment using pulleys and
weights. In Europe the Brugger system enjoyed wide use.
The principal advantage of the non-instrumented mechanical methods is that they
simulate closely the way in which the cross seal in a packaging machine is stressed.
The most severe disadvantages are:
- They are notoriously dependent on operator technique, with consequent
reproducibility problems.
- Each test cycle gives a go/no-go result, which requires many cycles at a great
expenditure of time to develop the quantitative data required to characterize even a
single sample.
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No information is generated on the time duration of the test. Hot Tack testing is
done to get information on the strength of the seal within the first 1000
milliseconds of its life - - while the sealed package is still in the machine and
subject to the stresses characteristic of the process. The mechanical methods apply
stress to the seal almost immediately after the jaws open,
but the endpoint of the test may not be reached until several seconds later which is
highly undesirable.
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