Organic Peroxides

A review of the literature for these compounds has resulted in very little new information. Consequently, the content of this chapter is drawn heavily from the previous authors, including the tables. The only compounds where there has been publishing activity are: dibenzoyl peroxide, methyl ethyl ketone peroxide, t-butyl hydroperoxide, isopropylbenzene hydroperoxide, and peroxyacetic acid. A recent review compared the skin tumor promoting activity of different organic peroxides in SENCAR mice (especially t-butyl peroxide, dicumyl peroxide, and also dibenzoyl peroxide). Much of this literature is, however, irrelevant to health. The introduction presented in the previous edition is entirely correct and relevant. Peroxides are highly reactive molecules due to the presence of an oxygen–oxygen linkage. Under activating conditions, the oxygen–oxygen bond may be cleaved to form highly reactive free radicals. These highly reactive radicals can be used to initiate polymerization or curing. Consequently, organic peroxides are used as initiators for free-radical polymerization, curing agents for thermoset resins, and cross-linking agents for elastomers and polyethylene. In some cases they can be used as antiseptic agents. These materials must be handled and stored with caution. If free radicals are formed during storage in concentrated form, an accelerated decomposition could result, leading to the release of considerable heat and energy. It has been determined that decompositions of commercially available peroxides are generally low-order deflagrations rather than detonations. There have been several investigations into the types of physical hazards represented by organic peroxides. These compounds may possess the combination of thermal instability, sensitivity to shock, and/or friction, as well as flammability. Organic peroxides tend to be unstable, with the instability increasing with greater concentrations. Because of their instability, many peroxides are stored/handled in inert vehicles. Basically only acute health testing has been performed on organic peroxides. Exposures should be well controlled, primarily owing to the decomposition or deflagration hazard of the organic peroxide. The health data presented were collected and furnished by the Organic Peroxide Producers Safety Division of the Society of the Plastics Industry to the previous authors of this chapter and are presented again in this edition. This represents an effort by industry to evaluate their products and provide that information to the public. Most of the information in the table has been previously published in an industry bulletin. The analytic method should also be specific for each organic peroxide. Many analytical methods that have not been subjected to review by consensus standard organizations or regulatory agencies are in use. Some examples include gas chromatography (dialkyl peroxides such as di-t-butyl peroxide), high-pressure liquid chromatography (peroxyketals), and iodometric titration (peroxyesters, diacyl peroxides, hydroperoxides, and peroxydicarbonates). Some degree of selectivity in iodometric titrations may be obtained by variation of the reducing agent employed and the reaction conditions.