ISSN 1070-4272, Russian Journal of Applied Chemistry, 2015, Vol. 88, No. 4, pp. 626−629. © Pleiades Publishing, Ltd., 2015.
Original Russian Text © I.T. Gabitov, A.G. Mustaﬁ n, V.P. Zakharov, R.M. Akhmetkhanov, 2015, published in Zhurnal Prikladnoi Khimii, 2015, Vol. 88, No. 4,
AND POLYMERIC MATERIALS
A series of uracil derivatives are used in practical
medicine as drugs . Some uracils, in particular,
5-hydroxy-6-methyluracil and 5-amino-6-methyluracil,
exhibit antioxidant activity in radical-chain oxidation of
isopropanol and 1,4-dioxane [2, 3]. Therefore, the study of
the inhibiting performance of 5-hydroxy-6-methyluracil
in thermal oxidative degradation of rigid and plasticized
polyvinyl chloride (PVC) is of scientiﬁ c and practical
As investigation object we used 5-hydroxy-6-
Thermal oxidative dehydrochlorination of rigid or
plasticized PVC was performed at 175°С in a bubbler
reactor in an oxygen stream (3.5 L h
). The time τ of
PVC thermal stability was determined by the change in
the color of Congo Red indicator due to HCl evolution
in the course of the polymer degradation (175°С) in
accordance with GOST (State Standard) 14041–91.
The PVC dehydrochlorination rate was determined
by the procedure described in . The hydroperoxide
accumulation was monitored by iodometric titration .
Polyvinyl chloride S-7059М was puriﬁ ed by washing
with ethanol in a Soxhlet apparatus. The ester plasticizer,
dioctyl phthalate (DOP), was puriﬁ ed by ﬁ ltration through
a column packed with aluminum oxide. 5-Hydroxy-6-
methyluracil (main substance content 99.0%) was used
without additional puriﬁ cation.
Introduction of 5-hydroxy-6-methyluracil into
rigid PVC under the conditions of thermal oxidative
degradation leads to a noticeable decrease in the polymer
dehydrochlorination rate (Fig. 1). The maximal decrease
in the HCl elimination rate is observed at the uracil content
of 2 mmol mol
PVC (critical antioxidant concentration).
At antioxidant concentrations higher than the critical
concentration, the polymer degradation rate increases.
The rate of thermal oxidative dehydrochlorination of
the polymer in the presence of uracil decreases virtually to
the level corresponding to the rate of thermal elimination
of HCl from PVC in an inert atmosphere, which is typical
of antioxidant stabilizers. 5-Hydroxy-6-methyluracil is
comparable in stabilizing performance against thermal
Low-Toxic Nitrogen-Containing Antioxidant
for Polyvinyl Chloride
I. T. Gabitov, A. G. Mustaﬁ n, V. P. Zakharov, and R. M. Akhmetkhanov
Bashkir State University, Kommunisticheskaya ul. 19, Ufa, Bashkortostan, 450076 Russia
Received March 3, 2015
Abstract—The kinetics of thermal oxidative dehydrochlorination of rigid and plasticized polyvinyl chloride
in the presence of 5-hydroxy-6-methyluracil was studied. 5-Hydroxy-6-methyluracil shows high antioxidant
performance, inhibiting the polymer degradation. This additive signiﬁ cantly decelerates the accumulation of hy-
droperoxides in the course of oxidation of the polyvinyl chloride plasticizer, dioctyl phthalate, which ultimately
leads to considerable deceleration of the degradation of the plasticized polymer.