Organic peroxides are compounds possessing one or more oxygen–oxygen bonds that are thermally and photolytically sensitive to facile homolytic cleavage. Thermal decomposition rates are affected by the structure of the organic peroxide and the decomposition conditions. The initially formed free radicals from the oxygen–oxygen bond homolysis are reactive intermediates which quickly undergo a variety of subsequent reactions to form stable products. Thermolysis of organic peroxides is used commercially to initiate free‐radical reactions, eg, halogenation, vinyl monomer polymerization, unsaturated resin cure, polyolefin cross‐linking and rheology modification. Many organic peroxides also undergo reactions in which free radicals are not involved, eg, heterolyses, hydrolyses, reductions, and rearrangements. This article reviews the physical and chemical properties, synthetic methods, and the principal commercial uses of organic peroxides of the following classes: hydroperoxides, dialkyl peroxides, α‐oxygen‐substituted hydroperoxides and dialkyl peroxides, ozonides, peroxyacids, diacyl peroxides, and alkyl peroxyesters. Class discussions cover the broad structural variation that is possible, including organomineral and polymeric derivatives when appropriate. Emphasis is placed on the relationship between peroxide structure and reactivity (thermal stability). Physical hazards associated with organic peroxide manufacture, handling, storage, transportation, and use are discussed. An overview of health hazards associated with handling of organic peroxides is presented.
Most commercial free‐radical applications employ initiators such as peroxides and azo compounds. Lesser amounts of carbon–carbon initiators and photoinitiators, and high energy ionizing radiation are also used commercially to generate free radicals. The chemical initiators are substances possessing labile oxygen–oxygen, carbon–nitrogen, or carbon–carbon covalent bonds that under certain thermal, chemical, or photochemical conditions undergo homolytic scission of the labile bond to produce free radicals. The free radicals produced are useful in many industrial chain reactions, eg, halogenations, additions to carbon–carbon double bonds, polymerizations of vinyl monomers, grafting reactions, curing of rubbers and unsaturated polymers, cross‐linking of polyolefins, modification of polyolefins, and reactive processing. In this article free‐radical initiator decomposition pathways are reviewed. Initiator reactivity is related to chemical structure and to first‐order decomposition parameters such as temperature, frequency factor, and activation energy. Reactivity of derived free radicals is also related to structure and to the occurrence of secondary reactions such as β‐scission and induced decomposition. The energy and the chemical properties of the free radicals determine commercial utility, thus the interrelation of initiators, their kinetics, and the radicals produced provide guidelines for initiator selection.
Most commercial free‐radical applications employ initiators such as peroxides and azo compounds. Lesser amounts of carbon–carbon initiators and photoinitiators and high energy ionizing radiation are also used commercially to generate free radicals. The chemical initiators are substances possessing labile oxygen–oxygen, carbon–nitrogen, or carbon–carbon covalent bonds that under certain thermal, chemical, or photochemical conditions undergo homolytic scission of the labile bond to produce free radicals. The free radicals produced are useful in many industrial chain reactions, eg, halogenations, additions to carbon–carbon double bonds, polymerizations of vinyl monomers, grafting reactions, curing of rubbers and unsaturated polymers, cross‐linking of polyolefins, modification of polyolefins, and reactive processing. In this article free‐radical initiator decomposition pathways are reviewed. Initiator reactivity is related to chemical structure and to first‐order decomposition parameters such as temperature, frequency factor, and activation energy. Reactivity of derived free radicals is also related to structure and to the occurrence of secondary reactions such as β‐scission and induced decomposition. The energy and the chemical properties of the free radicals determine commercial utility; thus the interrelation of initiators, their kinetics, and the radicals produced provide guidelines for initiator selection.
Most commercial free‐radical applications employ initiators such as peroxides and azo compounds. Lesser amounts of carbon–carbon initiators and photoinitiators and high‐energy ionizing radiation are also used commercially to generate free radicals. The chemical initiators are substances possessing labile oxygen–oxygen, carbon–nitrogen, or carbon–carbon covalent bonds that under certain thermal, chemical, or photochemical conditions undergo homolytic scission of the labile bond to produce free radicals. The free radicals produced are useful in many industrial chain reactions, eg, halogenations, additions to carbon–carbon double bonds, polymerizations of vinyl monomers, grafting reactions, curing of rubbers and unsaturated polymers, cross‐linking of polyolefins, modification of polyolefins, and reactive processing. In this article free‐radical initiator decomposition pathways are reviewed. Initiator reactivity is related to chemical structure and to first‐order decomposition parameters such as temperature, frequency factor, and activation energy. Reactivity of derived free radicals is also related to structure and to the occurrence of secondary reactions such as β‐scission and induced decomposition. The energy and the chemical properties of the free radicals determine commercial utility; thus the interrelation of initiators, their kinetics, and the radicals produced provide guidelines for initiator selection.
Organic Peroxides Inorganic Peroxides Azo Compounds Carbon–Carbon Initiators Other Radical Generating Systems Initiation Through Radiation and Photoinitiators Economic Aspects
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