A compound that passed once is not the same as a compound that passes every time. The lot record is how you tell the difference.
What should be on it
- A lot number you can trace to the mixing date and site.
- Results against limits for the tests that matter: hardness, tensile, elongation, compression set, specific gravity, and cure behaviour (ML, MH, ts2, t90).
- The method each result came from, so you can repeat it.
- A verdict that is not left to interpretation: within limits or not.
- Raw-material lots used, so a polymer or curative issue can be traced both ways.
How to read cure data
ML is minimum torque (a viscosity proxy), MH is maximum torque (a crosslink proxy), ts2 is how long before cure starts, t90 is time to 90 percent cure. Shifts in these between lots often show up before hardness moves. Our lot passport charts the last several lots so you can see drift.
What the record cannot tell you
A passing result says the lot met its limits. It does not say the compound suits your duty. That comes from the datasheet, your fluid testing and your approval process.
Ask suppliers
- Are retained samples kept, and for how long?
- What happens when a lot fails: scrap, rework or concession, and who decides?
- Is the record issued before shipping or after?
You can see an example on the Track page, using a sample lot.
About this article. It is original writing prepared from public sources, standards and general industry practice. It is not a copy of any book or standard and it is not engineering advice. Confirm values against the current edition of the standard and test in your own application. Only analyse material you own or are entitled to analyse.
