If you send "need 75 Shore A FKM, high temperature", every supplier will answer a different question. A good request lets you compare offers on the same footing. This is the checklist we ask for, and you can print it from the website.
1. The duty
- What the part is and how it seals (static, dynamic, gas, liquid).
- Fluids, including additives and contaminants, with concentrations.
- Temperature: minimum, maximum, and how long it spends at the maximum.
- Pressure and whether it cycles quickly.
2. The numbers you need
Write each property as a limit with a method and a condition, not as an adjective.
- Hardness, for example 75 ±5 Shore A (ASTM D2240 or ISO 48-4).
- Tensile strength and elongation at break (ASTM D412).
- Compression set, with temperature and time (ASTM D395 Method B, 22 h at 150 °C, say).
- Fluid immersion: which fluid, which temperature and time, and the allowed change in volume and hardness (ASTM D471).
- Anything specific to the duty: low-temperature retraction, gas decompression, steam ageing.
3. The supply
- Form: sheet, strip or pellets, and how it will be moulded.
- Quantity per order and per year, and the delivery you need.
- Packaging and labelling.
4. The paperwork
- Certificate of analysis for each lot.
- Lot traceability back to raw-material lots, if you audit that far.
- Any third-party approval you require. State it and ask for the certificate. A supplier should not claim approvals it does not hold.
5. How you will judge it
Say how you will accept it. For example: the first three lots tested at your laboratory, then audit by certificate. Suppliers price differently when they know the tests.
Common mistakes
- A single "temperature range" with no hold time.
- A compression set value with no test condition.
- Asking for an equivalent to a named grade without the numbers behind it. Our Decode service exists for that.
When you are ready, start a requirement. We will turn it into limits and a test plan and track it for you.
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.
