Originally Posted by
dscheidt
The layer of rubber that contacts the tube is a mixture of unvulcanized rubber and one of a few suitable vulcanization ultra-accelerators. There's an activator in the glue, which activates the ultra-accelerator. The patch then vulcanizes itself to the tube. Patches can fail from age if the vulcanization gets kicked off, which can happen with high temperature, and which might ahppen at slow rate with time. There are probably failures where the ultra-accelerator breaks down and doesn't do its job.
Does that activation imply that the glue needs to match the patch?? E.g. in Japan, patches and glue are marketed separately. For bigger tears you may e.g. buy a sheet out which you cut out a patch. Any shop will likely be offering a can of glue that can last for years without drying up. Myself I mix Rema and some quality Japanese products, but have yet to run into any problems.