"Initiators, Free-Radical". In: Encyclopedia of Polymer Science and ...

578 INITIATORS, FREE-RADICAL Vol. 6
Table 6. Commercial Dialkyl Peroxides
CAS 10-h
registry t1/2,
Name number Structure ◦ C a,b
2,5-Di(tert-butylperoxy)- [1068-27-5] 131
2,5-dimethyl-3-hexyne
2,5-Di(tert-butylperoxy)- [78-63-7] 120
2,5-dimethylhexane
1,3(4)-Bis(2-(tert- [25155-25-3] 119
butylperoxy)-
1-methylethyl)benzene
Di(tert-butyl) peroxide [110-54-4] 129
Di(tert-amyl) peroxide [10508-09-5] 123
Dicumyl peroxide [80-43-3] 117
aTemperature at which t1/2 = 10 h.
bIn dodecane.
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temperature curing of unsaturated polyester resin compositions. tert-Amyl diperoxyketals
are good initiators for acrylics, especially in the preparation of high
solids coatings resins (110).
Di(tert-alkyl) Peroxides. Some commercially available dialkyl peroxides
and their corresponding 10-h half-life temperatures in dodecane are listed in
Table 6 (111). Dialkyl peroxides initially cleave at the oxygen–oxygen bond to
generate alkoxy radical pairs:
Because high temperatures are required to decompose dialkyl peroxides at useful
rates, β-scission of the resulting alkoxy radicals is more rapid and more extensive
than for most other peroxide types. When methyl radicals are produced from
alkoxy radicals, the dialkyl peroxide precursors are very good initiators for crosslinking,
grafting, and degradation reactions. When higher alkyl radicals such as
ethyl radicals are produced, the dialkyl peroxides are useful in vinyl monomer
polymerizations. The behavior of di(tert-butyl) peroxide [110-54-4] under high
pressure has been investigated (112,113).
Dialkyl Peroxydicarbonates. Some commercially available dialkyl peroxydicarbonates
and their corresponding 10-h half-life temperatures (determined
in trichloroethylene solutions) are listed in Table 7 (114). These peroxides are
active at low temperatures and initially undergo homolytic cleavage to produce
(28)