Mechanisms of antioxidant action: Effect of amine complexing on the photo-antioxidant activity of zinc diethyldithiocarbamate in polypropylene

Abstract An elaborate investigation on the identity and usefulness of the antioxidants naturally occurring in Hevea latex is of value because there is an increasing demand for special types of rubber with low nitrogen and ash contents, less water absorption, better electrical properties, and less odor than common crepe, and because these rubbers are generally unstable in comparison with the usual grades of rubber crepe and sheet. for the purpose of the investigation, fresh latex was separated into main-fractions, the most important of which have been called water-solubles and ether-solubles. These were further separated into various subfractions, which, one by one, have been tested for their antioxidant activity on raw rubber. In the following table only those fractions which show an outstanding antioxidant action are recorded. It is shown further that the amino acids are most remarkable in their antioxidant action : minute quantities exert a strong retarding action on the oxidation of raw rubber. Choline and cephaline are most probably the active components of the second water layer. The active ether-soluble fractions could not be identified due to the small quantities separated.

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Mechanisms of Antioxidant Action: The Antioxidant Activity of “Spin-Traps” in Rubber

Rubber Chemistry and Technology ◽

10.5254/1.3536033 ◽

1984 ◽

Vol 57 (4) ◽

pp. 779-791 ◽

Cited By ~ 6

Author(s):

L. P. Nethsinghe ◽

G. Scott

Keyword(s):

Antioxidant Activity ◽

Mechanism Of Action ◽

Nitroxyl Radicals ◽

Antioxidant Action ◽

Spin Traps ◽

Phenolic Group ◽

Stable Phenoxyl ◽

High Level

Abstract A number of nitrones containing a partially hindered phenolic group are shown to be effective antidegradants for sulfur vulcanized rubbers. They exhibit a high level of antiozonant and antifatigue activity, but unlike commercial antiozonants they do not cause discoloration of light colored formulations. The new antidegradants are less effective than conventional additives as thermal antioxidants, but their performance as antifatigue agents and antioxidants is augmented by their use in combination with nonstaining antioxidants. The mechanism of action of the phenolic nitrones is believed to involve their oxidation to stable phenoxyl/nitroxyl radicals.

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UV-effects on antioxidant activity of selected carotenoids in the presence of lecithin estimated by DPPH test

Journal of the Serbian Chemical Society ◽

10.2298/jsc0811051c ◽

2008 ◽

Vol 73 (11) ◽

pp. 1051-1061 ◽

Cited By ~ 4

Author(s):

Dragan Cvetkovic ◽

Dejan Markovic

Keyword(s):

Antioxidant Activity ◽

Ultraviolet Radiation ◽

Energy Input ◽

High Energy ◽

Antioxidant Action ◽

Dpph Radical ◽

Dpph Test ◽

Uv Photons

The effects of ultraviolet radiation (UV) on the antioxidant action of three selected carotenoids (?-carotene, lycopene and lutein) in the presence of a lipoidal lecithin mixture were studied by the DPPH (1,1-diphenyl-2-picrylhydrazyl) test. The test is based on the measurement of the decrease of the free DPPH radical absorbance at 517 nm caused by the antioxidant action of carotenoids, which appeared to be strongly affected by UV-action. The high-energy input of the involved UV-photons plays a major governing role.

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EVALUATION OF ANTIOXIDANT ACTIVITY BY STABILIZATION OF VITAMIN A AND CAROTENE

Canadian Journal of Research ◽

10.1139/cjr50f-013 ◽

1950 ◽

Vol 28f (6) ◽

pp. 157-165 ◽

Cited By ~ 1

Author(s):

H. J. Lips ◽

W. D. McFarlane

Keyword(s):

Antioxidant Activity ◽

Vitamin A ◽

Ultraviolet Irradiation ◽

Wheat Germ ◽

Mineral Oil ◽

Ethylene Dichloride ◽

Antioxidant Action ◽

Accelerated Tests ◽

Wheat Germ Oil ◽

General Evaluation

Accelerated tests for antioxidant activity are described which depend on the protection of vitamin A concentrates (in ethylene dichloride solution) against ultraviolet irradiation, and on the protection of carotene (in mineral oil solution) against heat and aeration. The protection of vitamin A was influenced by light-filtering effects; the carotene method appeared to be more generally useful. The stabilizing power of wheat-germ oil for both solutions of Vitamin A and carotene against light is partly due to a screening effect by pigments. Some of the protection is also due to other components of the wheat-germ oil, but it is not known whether these function as stabilizers against light according to the usual theories of antioxidant action. Light-accelerated decomposition of vitamin A and carotene appeared more suitable for special tests than for general evaluation of antioxidants; stability experiments in the absence of light gave a more generally applicable picture of antioxidant activity.

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