Polymer00020 - t-butoxy radicals undergo ß-scission to...

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9 bromo- 3,3,4,4-tetrafluorobutene (BTFB), and the total bromine comprised of 0.5 – 0.9 wt% of the fluoroelastomer. Reaction conditions in the continuous emulsion polymerization process can be adjusted to minimize unwanted transfer to incorporated bromine-containing units, thus avoiding excessive long-chain branching. Such transfer and branching reactions are more difficult to minimize in semi-batch processes, since the entire polymer formed remains in the reactor exposed to free radical activity until the end of the batch polymerization. Figure 1.4 shows the probable cure reactions resulting from initiator decomposition in a typical peroxide compound (Moore 2005). Most of the primary
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Unformatted text preview: t-butoxy radicals undergo ß-scission to acetone and methyl radicals. A major fraction of the methyl radicals add to the allyl functionality of the triallyl isocyanurate (TAIC) coagent to form radical adducts. Only a minor fraction of methyl radicals is involved in transfer reactions with fluoroalkyl bromide sites on polymer chains to form methyl bromide and polymeric radicals. If the radical trap concentration is reduced considerably, the amount of methyl bromide increases by up to a factor of two, still relatively low versus the total amount of methyl radicals produced....
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