1070-4272/01/7405-0845$25.00C2001 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 74, No. 5, 2001, pp. 845!850. Translated from Zhurnal Prikladnoi Khimii, Vol. 74, No. 5,
2001, pp. 820!825.
Original Russian Text Copyright + 2001 by Krivoguz, Yuvchenko, Zvereva, Pesetskii.
AND POLYMERIC MATERIALS
Grafting of Methylenebutanedioic Acid to Low-Density
Polyethylene in the Course of Reactive Extrusion,
Initiated with Carborane-Containing Peroxides
Yu. M. Krivoguz, A. P. Yuvchenko, T. D. Zvereva, and S. S. Pesetskii
Belyi Institute of Mechanics of Metal!Polymer Systems, Belarussian National Academy of Sciences,
Institute of Chemistry of New Materials, Belarussian National Academy of Sciences, Minsk, Belarus
Institute of Physical Organic Chemistry, Belarussian National Academy of Sciences, Minsk, Belarus
Received November 23, 2000
Abstract-The influence of carborane-containing peroxides on the efficiency of grafting of methylenebutane-
dioic acid to low-density polyethylene in a single-screw extrusion reactor equipped with a static mixer was
Grafting of monomers containing chemically active
functional groups to polyolefin macromolecules is a
subject of active study in many research centers ,
which is due to growing use of grafted products in
preparation of polymeric composites, mostly of poly-
mer blends and alloys. As a rule, grafting is performed
in a polyolefin melt; as continuous reactors are used
special extruders acting simultaneously as high-per-
formance mixers of the components and providing
controllable feeding of the components, removal of
by-products, accurate temperature control, control of
the velocity of the reaction mixture transport, etc.
[1, 6]. The yield of the grafted product and the course
of side processes are determined both by the extruder
design features and by the reaction mixture composi-
tion [1, 5, 6]. In particular, we showed in [5, 6] that
the course of grafting of methylenebutanedioic acid
(MA) to low-density polyethylene (LDPE), at identi-
cal apparatus design and process (thermal) parameters,
is largely influenced by the nature and concentration
of the peroxide initiator. Use for these purposes of
commercial peroxides [dicumyl peroxide (DCP), 2,5-
dimethyl-2,5-di-tert-butylperoxyhexane, etc.] results
in active chemical cross-linking of the macromole-
cules, occurring simultaneously with grafting of MA.
As a result, strongly cross-linked products are formed,
which limits their use for fabrication of composites.
Furthermore, the product obtained by grafting of MA
to LDPE (LDPE-graft-MA) with traditional peroxides
exhibits a poor resistance to thermal oxidative degra-
dation in air and in aqueous solution .
In  we described the synthesis of unsaturated
carborane-containing peroxides. These peroxides can
be used for cross-linking of polyethylene , initiat-
ing high-temperature radical cross-linking reactions.
In contrast to cross-linked polyethylene prepared with
traditional peroxides, the product obtained with car-
borane peroxides exhibits enhanced resistance to ther-
mal oxidative degradation . Presumably, the ther-
mostabilizing effect of carborane peroxides is due to
grafting of carborane-containing fragments formed by
thermolysis of the peroxide to macromolecules and
intermolecular cross-linking through boron atoms. The
possibility of grafting to polyolefin molecules of func-
tional groups of unsaturated peroxides is indicated,
e.g., by Assoun et al.  who studied grafting of
carboxy groups to polypropylene macromolecules in
the melt under the action of peroxy acids.
It is interesting to evaluate the effect of carborane-
containing peroxides as initiators of grafting of func-
tional monomers to polyethylene macromolecules.
Here this problem is studied with grafting of MA to
LDPE as example.
We used LDPE of 158033020 brand [GOST (State
Standard) 16337377, Polimir Production Association,
Novopolotsk; density 0.92 g cm
, mp 105oC] and
MA purchased from Chemical Division Pfizer, the
United States. The following carborane-containing
peroxides were chosen (Table 1): peroxy esters I and