The resistance of a newly formed heat seal to separation while the seal is still hot, before it has cooled to ambient temperature.
Also called: hot tack; hot seal strength; hot-tack seal strength.
Why can a strong cooled seal open during handling?
The bond measured while hot can differ from the bond measured after cooling. A strong later peel result does not by itself answer whether the newly made seal withstands an earlier load.
Identify the forces a new seal encounters and when they occur. Compare that bond state with the laboratory result, recognising that package transfer and a tensile fixture apply loads differently.
Record the material construction, sealing time, upper and lower temperature conditions, force, delay before withdrawal and withdrawal rate. Different delays can assess different stages of bond development even when displayed sealing temperatures match.
Use hot-tack results to assess the stated early-handling load. Leakage through the finished package remains a separate integrity question.