Organic Peroxides are especially useful as free radical sources because of
the wide range of temperatures under which they undergo cleavage to form
The reactivity of the peroxide is often expressed in terms of half life as a
means of comparing the rate of decomposition relative to other peroxides. The
rate of decomposition for most peroxides is temperature dependent and follows
first order kinetics.
Half life data for virtually all of the commercial peroxides have been
determined. Usually 1-hr and 10-hr half-lives are reported.
Promoters and accelerators are commonly used to alter the rate of
decomposition of some initiators, thereby extending the temperature range under
which they can be employed.
Peroxides are classified according to several general chemical types. Major
classes include hydroperoxides, alkyl peroxides, acyl peroxides, ketone
peroxides, peroxyesters, peroxydicarbonates, peroxyketals and peroxyacids. Some
of these classes contain many peroxides having a wide range of reactivities and
so may be found in a variety of applications.
In the ensuing discussion on the various applications of Organic Peroxides,
those peroxides which are readily available in India by virtue of indigenous
manufacture will be marked in bold print.
Applications in Polymerizations :
Polymerization applications involve the use of Organic Peroxide initiators in
suspension, emulsion and bulk polymerization systems. Peroxides are often used
alone as free radical sources, but metal redox catalysts may also be used.
Polythene, the highest volume thermoplastic resin, is produced in several forms
high, medium, low, linear low, high molecular high density. LDPE is made with
peroxyesters such as butyl per benzoate. t-butyl peroctoate, t-butyl per
pivalate, t-butyl peracetate as well as decanoyl peroxide and di-t butyl
peroxide. Medium density PE is manufactured with peresters such as butyl
perpivalate t-butyl perisobutyrate, tbutyl perneodecanoate and may also use
peroxydicarbonates such as di (secbutyl) peroxydicarbonate and diisopropyl
peroxydicarbonate. Combinations of these peroxides are also used.
The development of LLDPE has replaced some LDPE because of greater toughness
and tensile strength resulting from the more oriented structure of linear PE.
LLDPE is manufactured under several licenced processes using metal catalysts
replacing organic peroxides. HDPE also involves the use of catalysts other than