Synthetic rubber is black because carbon black is used as a filler.
If it is white then talc or ground chook feathers is the filler.
Neither of them serves any purpose other than to bulk out the material and protect against UV penetration.
What makes the difference is the binders
For decades the price of natural latex has gone lower than the floor as synthetics , particularly silicons replaced latex products.
So rubber compounders pack as much latex in as they can get away with and that is what causes rubber stuff to fall apart in short time.
