The real “recycling” operation has a very long history where the final goal was, and still is,  de-vulcanisation of rubber for re-vulcanisation in new compounds. ​

This recycling must be done in 2 steps: ​

First the size-down of the tire into small grains and then as 2nd step, the de-vulcanisation of these grains.​

This process is done in a mechanical, thermal, chemical way. Several processes and several chemical agents exist.​

The master question is: how can we know if “re-cycled” rubber is de-vulcanised? ​

Or in other words: When is it a re-active rubber?​

The simple answer was given by many European rubber labs: “the proof is by eating the cake!”. ​

If a MD Rheometer test shows the traditional S curve, then there was a re-vulcanisation of the recycled rubber grains: the grains are re-active.​