The initials “RTV” stand for"Room Temperature Vulcanizing". That’s
as opposed to vulcanization through heat and pressure.
The rubber compounds you mention are all RTV’s – different brands
Please be advised that "zero-shrinkage " mold materials will will
result only in zero-shrinkage molds,not in zero shrinkage castings.
There are just too many other factors involved, all introduced by
Castaldo Products Mfg. Corp