ISSN 1070-4272, Russian Journal of Applied Chemistry, 2015, Vol. 88, No. 6, pp. 1052−1056. © Pleiades Publishing, Ltd., 2015.
Original Russian Text © D.V. Leonov, N.L. Levkina, T.P. Ustinova, 2015, published in Zhurnal Prikladnoi Khimii, 2015, Vol. 88, No. 6, pp. 957−962.
Choice of the Composition and Complex Evaluation
of the Properties of Polycaprolactam Modiﬁ ed
with Oxidized Graphite
D. V. Leonov, N. L. Levkina, and T. P. Ustinova
Engels Institute of Technology, Branch of Gagarin State Technical University,
pl. Svobody 17, Engels, Saratov oblast, 413100 Russia
Received March 13, 2015
Abstract—Modiﬁ cation of polycaprolactam by introducing oxidized graphite in the step of the polymer synthesis
improves the tribological properties of the material with preservation of its main physicomechanical properties.
Modern studies in the ﬁ eld of the polymer modiﬁ cation
are aimed at improving the consumer’s characteristics of
the resulting materials. In particular, various modifying
additives, e.g., graphite, are used for improving the
tribological characteristics of polymers and parts thereof.
However, the graphite content of the polymer matrix
should be high, about 30%, which negatively affects the
properties of the composite material.
In this study, we examined the possibility of modiﬁ -
cation of the polyamide matrix by introducing oxidized
graphite (OG) in the step of the polymer synthesis by the
method of cationic polymerization. Oxidized graphite
is capable of thermal expansion under the conditions of
polycaprolactam (polyamide-6, PA-6) synthesis; also,
its density is initially considerably lower than that of
dispersed graphite, which allows the weight fraction of
the modiﬁ er in the polymer matrix, necessary for obtain-
ing PA-6 with improved tribological properties, to be
decreased with preservation of the required set of the
other operation properties.
In accordance with this goal, our study had several
aims: determination of the optimum conditions for PA-6
synthesis and of the optimum content of the modiﬁ er
(oxidized graphite) introduced into the polymerizing
system; evaluation of the main physicomechanical,
physicochemical, and functional properties of modiﬁ ed
PA-6; comparison of the efﬁ ciency of using the suggested
modiﬁ er, compared to using dispersed graphite.
The investigation objects were as follows: polycap-
rolactam synthesized in a laboratory using caprolactam
[GOST (State Standard) 7850–86] and phosphoric acid
(GOST 6552–80); oxidized or intercalated graphite (com-
pound prepared by intercalation of acid molecules or ions
into the interlayer space of the graphite crystal lattice) .
In our study, we used the standard procedures for
evaluating the physicomechanical and physicochemical
properties of the modiﬁ ed polymer and the following
investigation methods: IR spectroscopy (Mettler Toledo
probe spectrometer), optical microscopy (Axeoimager
A2m microscope), dynamic abrasion (load F
= 20 N,
R = 10 mm, rotation rate 286.5 rpm, test time 2 h),
determination of the volume electrical resistivity
(F507 teraohmmeter), and determination of the thermal
conductivity coefﬁ cient (PIT device).
RESULTS AND DISCUSSION
The optimum parameters of cationic polymerization
of caprolactam have been published, but modiﬁ cation
of polycaprolactam by introduction of oxidized graphite