Post-vulcanization analysis - possible?

[Hman750]

I have some (small) rubber wheels that are used as chain tensioners for drive chains. Some of them seem to chunk apart relatively early, while others last much longer. Is there a method to determine what the material differences might be? They appear identical and seem to have the same durometer, the only visible differences being tiny logos on one type of wheel while none appear on the other.

 

[GrahamBennett]

The wheels can be analysed by thermogravimetric analysis techniques especially if combined with a mass spectrometer. Rubber Consultants can do this for you at a cost.