| The initiation efficiency of dicumyl peroxide (DCP) acting upon dodecane has been quantified through measurements of initiator byproducts and alkyl radical yields. The latter were determined by trapping alkyl radicals with 2,2,6,6-tetramethyl-1-piperindyioxy (TEMPO). The instability of the resulting alkoxyamine with respect to disproportionation was found to be insignificant at the conditions employed in initiator efficiency studies. Higher temperatures leading to reductions in the overall initiator efficiency. Abstraction from the model hydrocarbon does not occur exclusively from secondary positions, but from primary sites as well.; Graft modification of model hydrocarbons can be initiated by hydroperoxides either thermally (at 170°C) or in conjunction with a catalyst (either cobalt or iron at 140°C). The addition of catalyst had no effect on the graft yield of a DCP initiated addition of vinyltrimethoxysilane to tetradecane, presumably due to the low yield and/or fast decomposition of hydroperoxides under graft-modification conditions.; Initiation efficiency of DCP in high-density polyethylene (HDPE) was studied by extending the nitroxyl-trapping techniques developed for the model hydrocarbon system. Initiation efficiencies determined by gas chromatographic analysis of DCP byproducts were significantly greater than those recorded in dodecane. Attempts to quantify alkyl radical yields by fluorescence analysis of a naphthoyloxy alkoxyamine derivative resulted in lower initiation efficiency values than measured by gas chromatography. This may have resulted from fluorescence quenching by a small amount of residual nitroxyl, which is difficult to remove from the polymer. |
