1070-4272/05/7809-1503C2005 Pleiades Publishing, Inc.
Russian Journal of Applied Chemistry, Vol. 78, No. 9, 2005, pp. 1503!1507. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 9,
2005, pp. 1527!1532.
Original Russian Text Copyright + 2005 by Lin, Vorob’eva, Marchenko.
AND POLYMERIC MATERIALS
Influence of Copper on Oxidation of Polyethylene
D. G. Lin, E. V. Vorob’eva, and N. V. Marchenko
Skorina Gomel State University, Gomel, Belarus
Received May 3, 2005
Abstract-Thermal oxidation of polyethylene containing amine and phenolic antioxidants during contact with
copper (metal support, powder) and the trends in variation of the antioxidant performance were studied.
Oxidation of noninhibited polyethylene (PE) in
contact with catalytically active metals (including
copper) is accompanied by dissolution of the metal
support and transfer of the metal into the polymer
bulk . It was shown in  that noticeable
metal transfer starts since the end of the induction
period of polymer oxidation (IPO) (the IPO duration
was estimated from the content of carbonyl groups
in PE). Egorenkov  confirmed the carboxylate
mechanism of the metal transfer suggested in .
The absorption bands characteristic of metal salts of
fatty acids were found in the range 150031650 cm
in the IR spectra of PE films containing the trans-
ferred metal. Egorenkov  also confirmed the exist-
ence of two types of carboxylates (anhydrous and
hydrated) in PE. It follows from  that, in the
course of contact oxidation of PE on a copper support,
the most probable scheme of metal transfer is diffu-
sion in PE of low-molecular-weight metal carboxy-
lates (which are products of contact reactions).
The transferred metal compounds affect the devel-
opment of redox transformations in PE. For instance,
the copper compounds taken in small concentrations
catalyze PE oxidation, but at higher concentrations
they, on the contrary, inhibit it. Similarly, copper(II)
stearate affects oxidation of noninhibited PE .
Therefore, it was suggested to consider the catalysis
of PE oxidation on copper supports as homogeneous,
effected by the transferred copper-containing com-
pounds, the more so as, in the course of contact oxida-
tion of PE on a copper support, IPO practically coin-
cides with the time after which the metal transfer into
the PE film becomes noticeable.
An antioxidant (AO) introduced into PE increases
the IPO. Data on the influence of catalytically active
metals and their compounds on the oxidation of in-
hibited PE are fragmentary . It was shown in
 that IPO becomes shorter when PE containing a
phenolic AO contacts with copper, i.e., the AO be-
comes less effective. In the case of PE inhibited with
amine AO Neozon D, contact with copper, on the
contrary, increases the IPO . We suggested that,
upon contact with copper, the amine AO transforms
into a product with a higher inhibiting power. How-
ever, it remained unclear why the performance of the
phenolic AO drastically decreases in the presence of
copper . It is of interest to determine how trans-
formations of AO (phenolic or amine) are connected
with the copper transfer into the polymer being oxi-
dized. This was the subject of our study.
We used unstabilized, high-density PE prepared at
low pressure on complex organometallic catalysts
[GOST (State Standard) 16338385, base trade mark
20308-005]. Amine (Neozon D, N-phenyl-2-naphtyl-
amine, GOST 39379) and phenolic (Irganox 1010,
pentaerythriol ester of 4-hydroxy-3,5-di-tert-butyl-
phenylpropionic acid) AO were taken as inhibitors. To
prepare compositions with PE, an AO powder was
dissolved in acetone (GOST 2603379), and the solu-
tion was stirred on a magnetic stirrer for 3 min. The
AOs were introduced by wetting of a PE powder with
an AO solution, followed by solvent evaporation at
room temperature. For certain samples of inhibited
PE, we used fillers: a copper powder (trade mark M1),
which was introduced into the polymer by mechanical
mixing, or copper(II) stearate [TU (Technical Specifi-
cations) 6-09-12-152375] introduced similarly to AO
through the solvent. From PE blends with AO and
other modifiers, we prepared films (100 mm) by hot
pressing (150oC, 30 s) and used them in the study.