The determination of zinc oxide in rubber vulcanizates by x-ray diffraction

The important role of zinc oxide in accelerated rubber vulcanization has not been throughly defined. One major void in the investigations reported has been the absence of a suitable analytical method for following the rate of disappearance of zinc oxide. A method based on x‐ray diffractometry is here presented for the direct determination of zinc oxide in rubber vulcanizates. The technique employed is rapid and nondestructive and has a relative error less than ±10% of the amount of zinc oxide present. Application to typical accelerated rubber vulcanizates has shown that the rate of zinc oxide disappearance was independent of the amount and type of reinforcing filler. It was found also to be independent of the degree of crosslinking despite the known dependence of high level crosslink formation on the presence of zinc oxide in this type of curing system. The major part of the reacted zinc oxide appeared as zinc sulfide.