How rubber ages - any polymer scientists on here?

[Globalti]

I'm about to flog some 10 year old but almost unused Continental MTB slicks on Eblag. When I first got them, they left indelible brown stains on the kitchen lino. I'm no rubber scientist but I always assumed this was something to do with the high sulphur content of the rubber. Now they seem harder and less smelly and sticky than I remember - would this be because the sulphur has actually migrated out?

 

[ArDee]

I’m not a polymer scientist; but, have dealt with polymers in my job.

The sulphur is there as cross linking between the rubber molecules and provides suitability and strength to a material that is otherwise very elastic. The degradation you’ve seen, being less sticky, is probably oxidisation rather than loss of sulphur from the rubber. The oxidisation will reduce the tensile strength of the material (its ability to lengthen, without cracking) and the peel strength (its ability to stick to it’s self); hence, old tires when blown up and placed under tension crack and may flake little bits off the surface.

Hope this is of some use.

 

[Globalti]

Yes it is, thanks.