Shelf life varies by product. Many stable solid intermediates, such as sulphonic acid salts, are commonly given a shelf life or retest period of one to two years when kept dry and sealed. Amines that oxidise and esters that hydrolyse keep for less.
The supplier should state a shelf life or retest date on the COA or in the TDS. If it does not, ask for one and the basis for it.
What shortens shelf life
These are the usual causes of decline in storage:
- Moisture, which causes caking and can hydrolyse reactive products such as vinyl sulphone para base ester.
- Air, which oxidises many aromatic amines and turns them darker.
- Heat, which speeds up most degradation and can be severe in containers at port in summer.
- Light, which can discolour some amines and nitro compounds.
- Damaged or poorly sealed packs, which let in all of the above.
Shelf life versus retest date
A shelf life is a date after which the product should not be used. A retest date is a date after which the product should be tested again before use. Many intermediates are given a retest date, because a stored lot may still meet the specification later.
If a lot passes retest, you can usually use it and set a new retest date. If it fails, it may be reworked or rejected. Agree this approach with your own quality team.
How to protect what you buy
Ask for packing that suits the product. Sealed liners suit moisture-sensitive powders, and a nitrogen blanket in drums suits liquid amines. See how intermediates are packed and shipped.
Check the manufacture date on arrival. A lot that sat in a supplier's warehouse for months has less life left. Your contract can require a minimum remaining shelf life at dispatch.
Transit time counts against shelf life too. Several weeks at sea, plus port and customs time, can use a large part of a short shelf life, so plan order timing around it.
Store in a cool, dry place and use older lots first. Keep a retained sample of each lot, so you can compare it with the stored stock if results drift.
Signs a lot has aged
Watch for caking, darker colour, a changed smell or lower assay. In use, aged intermediates often show as lower dye strength or a duller shade. Retest any lot that looks different from the retained sample, using the methods in how intermediate purity is tested.
Next step
We check manufacture dates and packing at loading, so you receive fresh lots in sound packs. To discuss your intermediates, book a free sourcing review.