Peroxy carbonate initiators, decomposition

Peroxy-linked dimers are also formed from linoleate hydroperoxides in the presence of free radical initiators and copper palmitate, and carbon-carbon linked dimers in the presence of copper catalysts. Decomposition of methyl linoleate hydroperoxides at 210°C under nitrogen produces mainly carbon-carbon linked dimers (82%), monomers with loss of diene conjugation, volatile compounds (4-5%) and water. The resulting dimers contain carbonyl and hydroxyl groups and double bonds scattered between carbon 8 and carbon 10. Linoleate hydroperoxides can dimerize by one of the termination reactions discussed in Chapter 1. The termination reactions involving combination of alkyl, alkoxyl, or peroxyl radical intermediates produce dimers with carbon-carbon, carbon ether, or peroxy links. The carbon-carbon and carbon-oxygen linked dimers are favored at elevated temperatures and the peroxy-linked dimers at ambient temperatures. The peroxy-linked dimers may also decompose to the ether-linked and carbon-carbon linked dimers via the corresponding alkyl and alkoxyl radical intermediates. 

The decomposition of the initially formed hydroperoxide is catalyzed by the paint drier. The resulting free radicals, R" and RO, combine to form ether, peroxy and carbon-carbon crosslinks between oil molecules. These crosslinks form a continuous three dimensional matrix. 

---