Peroxide initiation

Peroxide curing systems Peroxide decomposers Peroxide initiators Peroxides... 

Two secondary propagating reactions often accompany the initial peroxide decomposition radical-induced decompositions and -scission reactions. Both reactions affect the reactivity and efficiency of the initiation process. Peroxydicarbonates and hydroperoxides are particularly susceptible to radical-induced decompositions. In radical-induced decomposition, a radical in the system reacts with undecomposed peroxide, eg ... 

Resin cement materials are provided as a two-part powder—Hquid product. The powder consists largely of poly(methyl methacrylate) to which various fillers (qv) maybe added. These include calcium carbonate [471-34-1], siHca [7631-86-9], barium carbonate [513-77-9], and calcium tungstate [7790-75-2]. An organic peroxide, eg, benzoyl peroxide, capable of generating free radicals is also present (see Initiators Peroxides, organic). 

Free radicals are initially generated whenever polymer chains are broken and carbon radicals are formed. These effects occur during manufacture and in service life. Many elastomers are observed to oxidize at relatively low temperature (about 60°C), where carbon-hydrogen and carbon-carbon bond cleavages are highly unlikely. It has been demonstrated [52] that traces of peroxides impurities in the rubber cause low-temperature oxidation of rubber. These initiating peroxides are present in even the most carefully prepared raw rubber polymer [53]. 

Peroxide decomposers—These function by reacting with the initiating peroxides to form nonradical products. Presumably mercaptans, thiophenols, and other organic sulfin compounds function in this way [19]. It has been suggested that zinc dialkyldithiocarbamates function as peroxide decomposers, thus giving mbber compounds good initial oxidative stability. 

An identical reaction to the previous one can be carried out with carbon tetrachloride either at 25-106°C and under 30-80 bar or in the presence of a radical initiator (peroxide) ... 

Ozone is known to be a powerful oxidant capable of both initiating peroxidation in lipids and reacting with... 

Initiators (peroxides, azo-compounds, polyphenylbutanes) accelerate the oxidation of hydrocarbons. The rate of initiated oxidation is much higher than the rate of initiator decomposition [9,10,12,13]. 

It is well known that neutrophils, monocytes, macrophages, and other phagocytes produce superoxide upon activation with various stimuli and therefore, are potential initiators of lipid peroxidation. In 1985, Carlin and Arfors [75,76] showed that leukocytes initiate the oxidation of unsaturated lipids. Surprisingly, the leukocyte-initiated peroxidation of linoleic acid was not inhibited by SOD and, therefore, apparently was not initiated by superoxide, while liposome peroxidation was mediated by superoxide. No convincing explanations were given. 

LES/FDF-approach. An In situ Adaptive Tabulation (ISAT) technique (due to Pope) was used to greatly reduce (by a factor of 5) the CPU time needed to solve the set of stiff differential equations describing the fast LDPE kinetics. Fig. 17 shows some of the results of interest the occurrence of hot spots in the tubular LDPE reactor provided with some feed pipe through which the initiator (peroxide) is supplied. The 2004-simulations were carried out on 34 CPU s (3 GHz) with 34 GB shared memory, but still required 34 h per macroflow time scale they served as a demo of the method. The 2006-simulations then demonstrated the impact of installing mixing promoters and of varying the inlet temperature of the initiator added. 

Intermolecular electron transfer initiated peroxide decomposition. . 1231... 

Intramolecular electron transfer initiated peroxide decomposition. . 1236 HIGH-EFFICIENCY ORGANIC CHEMILUMINESCENT REACTIONS INVOLVING PEROXIDE INTERMEDIATES. 1238... 

Problem 15.44 Propanal reacts with 1-butene in the presence of uv or free-radical initiators (peroxides, sources of RO ) to give CHjCHjCOCHjCH CHjCH,. Give steps for a likely mechanism. ... 

Beside mechanical characterization, one important aim of this work is the evaluation of the effects of E-beam modification of PTFE powder on the friction and wear properties of PTFE-filled EPDM composites crosslinked by a radical-initiated peroxide system. Friction and wear properties of EPDM composites were... 

The OOQOOH radical may isomerize further, similar to the reactions of RO2. The isomer-ized product decomposes into a ketohydroperoxide5 species and one OH radical. The keto-hydroperoxide is fairly stable below about 800 K, but at higher temperatures it decomposes to yield two additional radicals [426]. Thus it is not until this final decomposition step of the ketohydroperoxide that chain branching is finally achieved in the low-temperature mechanism, yielding three radicals from the initial peroxide radical. 

Figure 3.3-7. Peroxide decomposition, change of intensity with time. Solid line, intensity dashed line, pressure dotted line, temperature initial peroxide concentration 1 wt.%.

In a recent patent Stamatoff (76) has described the polymerization of unsymmetrically substituted halophenols in a manner similar to that described by Price, using as initiators peroxides or persulfates. 

The major impurities which are found in any polymer are the unreacted monomer itself, unreacted initiator (peroxides and all types of photoinitiators) and catalysts used in the polymerization process, as well as traces of the solvent and of water. Within the polymer chain itself there will be some defects or impurity sites which result essentially from oxidation reactions during the making of the polymer. The polymerization process on an industrial scale cannot be performed in the absence of atmospheric oxygen, and this will attack the growing polymer chain at random points to produce... 

Two secondary propagating reactions often accompany the initial peroxide decomposition radical-induced decompositions and /3-scission reactions. Both reactions affect the reactivity and efficiency of the initiation process. 

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