Can anyone give me some expedient advice on the breakdown of
synthetic rubber?

I am working with Museum Studies students on a Hat show, and one item
featured is a 1950s moulded synthetic rubber bathing cap. This cap was
originally bright yellow with moulded sunflowers, but over time has
begun to show mottled brown areas which have hardened, and begun to
split.

This appears to be an oxidisation process. The question I have is
exactly what chemical process is occurring here? What compounds are
reacting with oxgen, innate in the rubber?

Any suggestions would be gratefully received, as the students' show
opens tommorrow night, and the conservation label gets written this
afternoon!

Roxanne Fea
Curator of Social History
The Science Centre & Manawatu Museum,
Palmerston North, New Zealand