ISSN print edition: 0366-6352
ISSN electronic edition: 1336-9075
Registr. No.: MK SR 9/7
Inhibitory effect of phenothiazine on the oxidation of natural rubber in the presence of α,α-diphenyl-β-picrylhydrazyl
J. Hrivíková, A. Hrivík, and V. Kellö
Department of Physical Chemistry, Slovak Technical University,
880 37 Bratislava
Abstract: The effect of phenothiazine (PT) on the oxidation of natural rubber in
the presence of α,α-diphenyl-ß-picrylhydrazyl (DPPH) was studied. Their
inhibitory effect was expressed by means of the length of the induction
period of oxidation and the index of the relative inhibitory efficiency Jre .
The synergistic effect on the subsequent oxidation of natural rubber thermally treated in an inert medium could be observed only at higher concentrations of phenothiazine and it decreased with increasing total concentration of the antioxidative mixture. Antagonism was observed at high
concentrations of DPPH in the presence of PT. At the oxidation of natural rubber without thermal treatment the mixture of DPPH and PT
appeared to be synergistic and the synergistic effect increased with the
molar fraction of DPPH. The course of the reaction between DPPH and PT,
accompanied by the formation of DPPH-H and phenothiazinyl radicals PT
( > N•) , was confirmed and the radicals were detected by the e.p.r. method.
Furthermore, basic reactions between DPPH and PT in the presence of
a thermally treated and subsequently oxidized rubber as well as the rubber
oxidized without a preliminary thermal treatment are described.
Full paper in Portable Document Format: 294a459.pdf
Chemical Papers 29 (4) 459–473 (1975)