The range of heat-sealing conditions within which a specified material combination achieves defined seal results.
Also called: heat-sealing window; heat seal window; seal process window; sealing temperature window.
Is a sealing window just a temperature range?
A temperature range describes only one slice when other factors are held fixed. The process question is which combinations of time, temperature, pressure and material produce the required result. Keep sealing conditions separate from the conditions used to measure the resulting bond.
State what acceptable means for the comparison. Seal strength, opening behavior, appearance, early bond strength and package integrity are distinct outcomes; a single pass at one setpoint does not locate a robust operating region. A chart without its material pair and fixed conditions cannot be transferred directly to another blister format.
Why can a laboratory window fail to transfer to the line?
Actual contact time, heating surfaces and pressure at the materials can differ from nominal settings. A laboratory response belongs to its defined material and test arrangement. It does not by itself qualify an entire production line.
Compare actual contact and material conditions, then assess the required outcomes on the production format. Document the combinations studied and excluded; a successful setpoint does not establish the surrounding acceptable range.