polymers getting yellow with temperature

Amount of amines, aromatic rings, ...?

Oliver

Based on my experience, yellowing is typically a result of some breakdown or crosslinking (depending upon the material in question) in polymers. Typically, these can be traced back to tensile strength, elongation to break, etc. This is the most common situation. (A lot of polymers also yellow upon radiation due to this reason, as well)

Sometimes yellowing is due to electron exicitation due to heat. The color restores after some (or long) time. I have just had one application of such a type. I am not sure how this may be traced back to some physical property...maybe, zeta potential or charge?

Niles

Since you are concerned with color I suggest you actually measure color or color shift. Concerning equipment I found this link, for example:

That's what we used to do to measure the effictiveness of stabilizers on color stability of (colored) polymers upon heat ageing.

You can then try to correlate a "color shift" with a mechanical property, like tensile strength, elongation or impact strength, for example, since those properties are typically most sensitive to thermooxidative surface degradation, although during an induction period you may see discoloration without any change in any of those mechanical properties ...

You can also analyse autooxidation, i.e. the formation of ROOH and carbonyl groups as function of the degree of heat aging as described in: "Stabilization of Polymeric Materials, H.Zweifel, Springer Verlag"

"Glass" schrieb im Newsbeitrag news:ch1h56$m9h$ snipped-for-privacy@atlantis.cu.mi.it...

UV (carbonyl) or IR (carbonyl) or there is also a norm for yellowness measurement or NMR or mechanical properties and maybe some others

Guenter Beyer

UV (carbonyl) or IR (carbonyl) or there is also a norm for yellowness measurement or NMR or mechanical properties and maybe some others

Guenter Beyer

As a follow-up to Rolf's suggestion on direct color measurement, Hunter Laboratories, Inc. and Munsell make equipment to measure color quantitatively. Such measurements are not susceptible to the subjectiveness of the unaided human eye interpretation of color.

Niles