Shelf life
Shelf life turns up in 2 fields: powder coating, adhesives. Here is what it means to the people in each one.
Shelf life in powder coating
How long boxed powder stays sprayable and reactive when stored cool and dry.
Most thermoset powders keep 6 to 12 months below about 80 F with low humidity; low-cure and fast-cure grades keep less. Heat starts the cure reaction early and fuses particles into lumps, a fault called caking or sintering, while moisture makes powder fluidize badly and charge poorly. Old powder often loses flow and shows more orange peel even when it looks fine in the box.
"This box sat in the hot trailer all summer, it's caked solid, way past its shelf life."
Shelf life in adhesives
The use-by window for a sealed container of adhesive, tied to the storage conditions on the label.
Shelf life runs from a few months for some cyanoacrylates and film adhesives to two years for many epoxies and hot melts. Storage conditions matter: CA and some acrylics are kept refrigerated, film adhesives frozen, and moisture-cure products sealed. Quality systems quarantine expired lots and require recertification testing before any extension.
"Shelf life on that cartridge ran out two weeks ago, red-tag it, we can't use it on certified parts."