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Hot Tack

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Q. What is “hot tack” and why is it important?

A. Hot tack is the strength of a hot seal during the first 500 to 1000 milliseconds after the sealing die (platen) opens away from the film. The strength of a seal changes rapidly as the seal cools. Therefore, hot tack is a variable that is a function of time and of ambient-cooling conditions affecting transfer of heat from the seal to its environment. Hot tack is important particularly in those converting operations where product is dropped into a package shortly after the seals have been made, such as on a vertical form fill and seal machine. Proper sealant film selection would take into consideration the weight of the product and force at which the product would be coming in contact with the molten polymer seal. Polyethylene films can be designed to have specific hot tack properties that match up well with the converting method employed.