Peroxide Decomposer Research Articles

コイの脂質過酸化物の吸収におよぼすビタミンEおよびエトキシキンの影響について

The effect of antioxidants on the absorption of lipid hydroperoxide in carp, Cyprinus carpio has been studied. The carp were divided into four groups. Group 3 was given synthetic diet with vitamin E (dl-α-tocopheryl acetate), Group 4 the diet with ethoxyquin (6-ethoxy-1, 2-dihydro-2, 2, 4-trimethylquinoline) and the others synthetic diet only. After they were fed on these diets for two weeks, the following 14C-labelled compounds were administered by polyethylene catheter. Group 1: 1-14C-methyl linoleate (1-14C-ML) Group 2: purified 1-14C-methyl linoleate hydroperoxide, POV 5960meq/kg (1-14C-MLHP) Group 3: 1-14C-MLHP plus vitamin E Group 4: 1-14C-MLHP plus ethoxyquin After 24 hours, all the fish were killed. The distribution of radioactivity in various tissues was compared among the four groups. The results are summarized as follows: 1) The carp absorbed little hydroperoxide of methyl linoleate. 2) The distribution of radioactivity in Group 3 was about the same as that in the control (Group 1). It is suggested therefore that vitamin E may act as a peroxide decomposer and stabilizing factor of intestinal epithelium. 3) Since the radioactivity in Group 4 was negligible, ethoxyquin was not effective for absorption of hydroperoxide in vivo.

Antioxidative stabilization of poly(vinyl chloride)

AbstractHalogenated resins such as poly(vinyl)chloride undergo rapid degradation when exposed to heat. Such degradation is significantly increased by oxygen, and it is believed that the induction of the process of decomposition is caused by autoxidation of the polymer, followed by extensive dehydrohalogenation. Sulfur‐containing peroxide decomposers allow primary stabilization of PVC with organic compounds which are not HCl acceptors but prevent free radical cross‐linking of the polymer. This implies a discolored polymer melt (due to loss of HCl and formation of polyenes) which nonetheless exhibits good long term stability (no cross‐linking). The stabilization of labile chlorine atoms results from the oxidation of various chain irregularities, and thus the elimination of the early discoloration can be achieved by the use of small quantities of monohydrocarbyltin co‐stabilizers. The relative performance of various antioxidant systems are reported and possible stabilization mechanisms are discussed.

Some Aspects of Thermal and Photochemical Autoxidation

AbstractFollowing an outline of the pioneering work of Haber's School, emphasis is placed on a critical review of the most important recent achievements. These embrace, in the area of thermal autoxidation: the concept of critical antioxidant concentration, the multiple effects of heavy metals (including catalyst‐inhibitor conversion), the development of new synergistic antioxidant combinations composed of free radical acceptor and peroxide decomposer and, finally, Denisov's direct experimental evidence for the reaction of heavy metals with molecular oxygen in organic media in support of Uri's trace metal hypothesis of the general mechanism of the initiation of autoxidation. The following recent advances in the field of photochemical autoxidation are described: photosensitized initiation by trace metals and its inhibition, the singlet oxygen hypothesis, the inadequacy of phenolic antioxidants and the reliance on UV absorbers, the importance of energy transfer in photochemical protection leading to new stabilizers. A very recent innovation which is relevant to both thermal and photochemical autoxidation is highlighted, i.e., the development of new α‐dithidiketone chelates, particularly bis (stilbenedithiolate) nickel (= NiS4C4Ph4or, abbreviated, NiSDT) as antioxidants which combine in a unique way the properties of free radical acceptors, peroxide decomposers and UV stabilizers. They were then found to be the most powerful antioxidants for polyethylene and polypropylene.

Practical Approaches to the Light Stabilization of Polypropylene Multifilaments

The stabilization of polypropylene against the effects of ultraviolet light has been the subject of considerable research. Stabilizing polypropylene multifilament yarns is understandably more difficult than stabilizing monofilaments or molded articles. Due to the small diameters of fiber (< 50 microns), conventional uv screeners (such as the benzophenones and benzotriazoles) offer little protection from ultraviolet light. Peroxide decomposers of the dialkylthiodipropionate variety have been found to be virtually ineffective in increasing fiber lifetimes, whereas certain phosphites are quite useful. Supporting laboratory data have shown that at low temperatures phosphites decompose hydroperoxides more rapidly and more efficiently than the dialkylthiodipropionates. Nickel stabilizers appear to be considerably more effective for multifilaments than the uv screeners. Our findings indicate that the Ni compounds function as quenchers of electronically excited carbonyl groups which arise from the photolysis of carbonyl impurities in the polymer. Combinations of the various types of stabilizers can lead to increased fiber lifetimes.

The oxyluminescence of polymers III. Effects of oxidation and structure; Mechanisms involved

AbstractStudies of polypropylene oxyluminescence show the luminous intensity to be dependent upon the degre of oxidation. The length of the low intensity level portion of the luninescence curve, or pseudo induction period, was found to be a measure of the useful stabilizer life, and the intensity of this portion indicative of the effectiveness of stabilization. The effect of peroxide decomposers was studied and results indicate that peroxide reactions are major producers of luminescence. Analysis of the accepted modes of polymer oxidation, in view of our luminescence findings, indicate that the rate of luminescence buildup should depend upon ease of R. formation and the luminous intensity should be dependent on peroxy radical concentration. The effect of tertiary‐carbon content on luminescence was also investigated, and luminous intensity was found to be dependent upon the amount of polymer branching. Model Compounds having slight structural variations were examined and were found to produce different intensity‐time curves during oxidation, which may be attributed to ease of formation of a reactive site and subsequent peroxy radical reactions.

Synergistic antioxidant combinations. Mechanism of stabilization with organo‐sulfur compounds

AbstractThe ability of diaryl disulfides to inhibit polyethylene oxidation is a result of the formation of an active antioxidant from these additives. This is evident from their ineffectiveness to inhibit until substantial oxidation has occurred. Elemental sulfur also appears to form a more effective stabilizer as oxidation proceeds. Thiolsulfinates have been suggested as the active products which are formed from disulfides. However, phenyl benzenethiolsulfinate decomposes rapidly even at its melting point (70°C.), and yet the protection obtained when it is added to cumene at 120°C. far exceeds the time in which total decomposition would occur. At low concentrations, phenyl benzenethiolsulfinate also fails to inhibit until oxidation has proceeded for an appreciable time. Thermal decomposition of phenyl benzenethiolsulfinate yields sulfur dioxide in addition to other products. Elemental sulfur and the several organo‐sulfur compounds studied function as stabilizers through their ability to decompose peroxides. Sulfur dioxide is by far the most effective peroxide decomposer. It apparently functions catalytically through an ionic mechanism forming products which do not propagate oxidation. The additional role of sulfur compounds to decompose peroxides, coupled with the ability to regenerate chain terminators in antioxidant combinations may account for the high order of synergism obtained with these compounds.