Inhibition of Rubber Oxidation by Carbon Black

Indirect measurements have shown that small amounts of carbon black inhibit rubber oxidation during Banbury mastication. To provide a more comprehensive picture of this inhibitory action, a study was made of its effects on some physical properties of fully compounded and vulcanized stocks prepared from masticated natural and synthetic polymers. The action of carbon black, with the exception of its behavior in Butyl rubber, was found to be broadly similar to that of standard antioxidants. The largest change in vulcanizate properties occurred in cold rubber after high-temperature mastication. The usual shortening and stiffening resulting from gelation of the polymer at high mastication temperatures was completely inhibited when the mastication was carried out in presence of small loadings of carbon black.