Checking for Differences of Materials

Check the relevant standards (you may be knowing). Quality of material depend on its "constituents" and "process of making" to get "certain range of properties". Standards broadly define these three things. You have to narrow down these as per your need and specify while ordering.

GA - Without a lab test, the heat deflection temperature is a good reference. I heat stake lots of plastics and Torlon at 675°F punch temperature is much higher than most engineering plastics at 300-400°F. Quick test if you have a soldering iron with adjustable tip temperature is to use the above values to discriminate between materials.

This may be a semantics thing, but chances are very good that the Torlon you buy tomorrow will not be "the Torlon 5530 material is the same one that I purchased earlier."

It may be from a different manufacturing run, but it will still be Torlon. Unless you are buying in bulk, the bags will be labeled.

Some lot-to-lot color variation is typical with most thermoplastic resins. This is one reason many molders just paint everything with paint, after molding.

If you are buying from a reputable supplier, I wouldn't worry.

I think ozzb is correct about softening points.

Lyn is exactly right, because thermoplastic suppliers do not supply "guaranteed minimum" specification values the way steel manufacturers do, they supply "typical" values so every manufacturing run can and most likely WILL be different. Your best bet is to only deal with a reputable supplier that isn't going to substitute a batch from some no-name generic manufacturer in BFE outer Mongolia instead of the name brand manufacturer that you specified and then forge the paperwork and pocket the difference in cost. Dealing with name brand suppliers is really the only defense unless you want to invest in having each and every batch tested against the "typical" values but even then, how much variation from "typical" can you tolerate? And how much variation does the manufacturer think is appropriate? Are they the same?

The melting test - while hazardous - due fluorine outgassing is separating the real from the also run. A capacitance measurement - on a for you standard flat or cylindrical form also helps to keep the supplier be honest. The dielectric factor of any matter is differing widely. Air=1, water = 80 about. Ceramics, glass, plastics inbetween. Measuring capacitance is as simple as anything else in the toolroom. Mechanical close tolerances are the key. The device itself is 100-200 dollars. Saves a lot of headache.

If you have conductive carbon loading (You better know it,, and can measure its resistance), you need from batch to batch consistent samples. But, I think that is your target after all. The exact measurement value does not matter. Any gross deviation between samples will alert you for trouble and be proof too.

Are you concerned that you will not get Torlon 5530, versus a different grade of Torlon? That there is lot to lot variability? Or that you might not get Torlon (Polyamide-imide) but possibly some other "black plastic"?

The last situation is the simplest to attempt without lab testing. You can check the specific gravity - 1.6. (Actually can simply do a sinks/floats test in water to rule out polyethylene.) Also look for glass fibers - Torlon 5530 is 30% glass-fiber reinforced. Check the glass transition temperature - it is 260C. (Torlon is an amorphous polymer and doesn't actually have a melting point.)

Are you buying this as a bulk material directly from the manufacturer or from a middle man, or from a fabricator in the form of stock shapes? For the first two, you want to get a certificate of analysis with each shipment/lot. While data sheets give "typical values", some properties are tested on every lot. This varies by manufacturer, material type, and customer requirements. You can discuss with them what properties you require to be tested on each shipment. For the third case (net shapes), the best you can do is to go with a reputable supplier. If you really need the physical properties of the material, you will have to send a sample to the lab.