ISSN 1070-4272. Russian Journal of Applied Chemistry, 2006, Vol. 79, No. 1, pp. 137!141. + Pleiades Publishing, Inc., 2006.
Original Russian Text + S.E. Mitrofanova, E.N. Girfanova, I.Yu. Averko-Antonovich, E.N. Cherezova, 2006, published in Zhurnal Prikladnoi Khimii,
2006, Vol. 79, No. 1, pp. 139!143.
AND POLYMERIC MATERIALS
New Oligomeric Thioether Antioxidants for Polymers
S. E. Mitrofanova, E. N. Girfanova, I. Yu. Averko-Antonovich, and E. N. Cherezova
Kazan State Technological University, Kazan, Tatarstan, Russia
Received June 20, 2005; in final form, November 2005
Abstract-Polyfunctional oligomeric antioxidants with a sterically hindered phenolic fragment were prepared.
The influence of these antioxidants on oxidation and degradation of SKI-3 rubber was analyzed.
Unsaturated nature of rubber macromolecular units
makes possible processing of rubbers into articles via
vulcanization and preparation of technically valuable
structural materials thereof, on the one hand, and is
responsible for gradual aging of the material, above
all, due to oxidation, on the other. Oxidation follows
the radical-chain mechanism [1, 2]. The primary oxi-
dation products of the polymer are polymeric peroxy
radicals (PRs) and hydroperoxides (HPs).
Chemically, antioxidative stabilization of polymer-
ic materials consists in scavenging of free radicals and
hydroperoxides. The most efficient and widely applied
PR scavengers are sterically hindered phenols (SHPs)
and aromatic amines . Hydroperoxides are de-
composed by compounds containing sulfur(II) atoms
. The researchers’ attention is currently focused on
stabilizers whose molecules contain several centers
able of decelerating oxidation of polymers. They are
attractive because of possible synergism of antioxida-
tion effects .
It should be taken into account that the use of
monomeric antioxidants often causes problems due to
their volatility, insufficient solubility, and washing out
from polymers. At the same time, a number of studies
showed that, with polymeric antioxidants eliminating
such problems, the functional groups act less efficient-
ly . Oligomeric antioxidants (OAOs) would appar-
ently be the best choice.
In this study, we developed a procedure for syn-
thesis of OAOs whose molecules contain centers able
of inhibiting oxidation via scavenging PRs and HPs
and examined their stabilizing performance.
As reactants served 4-dimethylaminomethyl-2,6-di-
tert-butylphenol (Mannich base, MB), mp 93395oC,
and a sulfur-containing oligoether TPM-2 [TU (Tech-
nical Specifications) 38103636387; dynamic vis-
cosity 1.9 Pa s at 25oC] with 3.42 wt % terminal
The antioxidants were synthesized by the following
procedure. A flask equipped with a stirrer, a water-
cooled reflux condenser, a thermometer, and a bubbler
was charged with TPM-2 and MB (when the reaction
was run in a solution, appropriate solvent was added).
The amount of MB taken for the reaction was gov-
erned by the preset number of the SH groups to enter
into the reaction (the calculations were carried out for
100, 75, 50, and 25% conversions of the SH groups in
the oligomer). The reaction mixture was stirred at
1003140oC in a nitrogen flow. The reaction was
monitored from evolution of dimethylamine absorbed
by 0.1 N H
with indicator (Methyl Orange).
The completion of the process was judged from
ceased evolution of dimethylamine.
The mass fraction of the SH groups was deter-
mined by a laboratory technique according to GOST
(State Standard) 12 812380.
The resulting stabilizers were introduced into 5%
solutions of SKI-3 (hereinafter, the weight percentage)
in toluene and stirred at room temperature until com-
plete homogenization, whereupon the solvent was
Self-oxidation of the polymer was run by the proce-
dure from  under oxygen (p
= 250 mm Hg) at
165oC (polymer weighed portion 0.1 g).
The oxidation, degradation, and mass loss tem-
peratures of the polymer were determined by differen-
tial thermal (DTA) and thermogravimetric (TGA)
analyses on an MOM (Hungary) derivatograph; the
heating rate for the samples was 5 deg min