ISSN 1070-4272, Russian Journal of Applied Chemistry, 2007, Vol. 80, No. 6, pp. 988!991. + Pleiades Publishing, Ltd., 2007.
Original Russian Text + S.E. Mitrofanova, E.N. Cherezova, 2007, published in Zhurnal Prikladnoi Khimii, 2007, Vol. 80, No. 6, pp. 1014!1017.
AND POLYMERIC MATERIALS
Synthesis of Polyfunctional Sulfur-containing Oligomers
and Their Effection SKI-3 Rubber and Its Vulcanizates
S. E. Mitrofanova and E. N. Cherezova
Kazan State Technological University, Kazan, Tatarstan, Russia
Received November 20, 2006; in final form, February 2007
Abstract-Polysulfide oligomers with sterically hindered phenolic fragments were prepared. Their effect on
the antioxidative stability and kinetics of vulcanization of rubber stocks based on SKI-3 rubber was examined.
Polysulfide oligomers (PSOs) are widely used as
components of sealants. The use of PSOs as effective
vulcanizing agents for unsaturated rubbers has been
reported . When used as vulcanizing agents, PSOs
provide formation of more flexible cross-links com-
pared to rigid sulfur bonds, thus imparting enhanced
elasticity to the vulcanizates.
Along with acting as vulcanizing agents, polysul-
fide oligomers are potentially capable, owing to the
presence of sulfide and terminal hydrosulfide groups,
of inhibiting oxidation of polymers by decomposing
hydroperoxides (HPs), i.e., can act as secondary anti-
oxidants (AOs) . It has been shown that terminal
hydrosulfide groups of sulfur-containing oligomers can
be used for introduction of functional groups , e.g.,
sterically hindered phenolic (SHP) fragments scaveng-
ing peroxy radicals. Apparently, combination in one
molecule of centers inhibiting oxidation of organic
substrates by different mechanisms will substantially
enhance the stabilizing function of the oligomers.
The goal of this study was to develop a procedure
for preparing polysulfide oligomers with terminal
SHP fragments and evaluate their antioxidative and
The starting chemicals were 4-dimethylaminometh-
yl-2,6-di-tert-butylphenol (Mannich base, MB), mp 933
95oC, and commercial PSO NVB-5, TU (Technical
Specification) 38.50 309393, content of total sulfur
37.20 and of SH groups 4.74 wt %.
The PSOs were prepared as follows. A flask
equipped with a stirrer, reflux condenser, thermom
eter, and bubbler was charged with the synthesized
polysulfides (PSs) and MB. The mannich base was
taken in an amount theoretically required for the con-
version of all the SH groups in the PS. The mixture
was stirred at 1103120oC in a nitrogen flow for 33
3.5 h. The reaction course was monitored by the re-
lease of dimethylamine, which was absorbed by a 0.1 N
solution, using Methyl Orange as indicator.
When the release of dimethylamine ceased, the reac-
tion was assumed to be complete.
The weight percentage of the SH groups was deter-
mined by a laboratory procedure according to GOST
(State Standard) 12 8123 80.
The IR spectra were recorded in the range 40003
with a Perkin3Elmer 16PC-FT-IR device.
Autooxidation of the polymer was performed in
= 250 mm Hg) at 135oC (polymer sam-
ple weight 0.1 g). To introduce PSO into the rub-
ber, 5% solutions of SKI-3 in toluene were prepared;
the mixtures were stirred to complete homogenization,
after which the solvent was vacuum-evaporated.
The rate and degree of vulcanization of rubber
stocks were determined with a Monsanto 100 S rhe-
ometer at 151oC; the test time was 60 min.
In our study, we prepared PSs with different ex-
tents of branching at the molar ratio monomer : so-
dium tetrasulfide = 1 : 1, with the aim to examine
the effect of the structure on the PS properties. As
the starting monomer we used dichlorodiethyl formal,
pure or with additions of other chlorinated mono-
mers (molar ratios: dichlorodiethyl formal : 1,2,3-tri-
chloropropane = 98 : 2; dichlorodiethyl formal : di-
ethane : 1,2,3-trichloropropane = 84.5 : 15 : 0.5).