Influence of the Ratios of Natural and Butadiene–Styrene
Rubbers on the Viscosity of Rubber Blends and Fragmentary
Mobility of Macromolecules
S. V. Usachev, E. L. Nikitina, and Yu. S. Makaricheva
Yaroslavl State Technical University, Yaroslavl, Russia
Received March 20, 2008
Abstract—The structural states of macromolecules of natural and butadiene–styrene rubbers in their blends
were studied by evaluating the spin–lattice relaxation times of carbon nuclei. The relationship between the
viscosity of rubber blends and fragmentary mobility of macromolecules was examined.
ISSN 1070-4272, Russian Journal of Applied Chemistry, 2009, Vol. 82, No. 3, pp. 492–495. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © S.V. Usachev, E.L. Nikitina, Yu.S. Makaricheva, 2009, published in Zhurnal Prikladnoi Khimii, 2009, Vol. 82, No. 3, pp. 498–501.
The dependences of the viscosity of blends of
natural (NR) and butadiene–styrene (BSR) rubbers on
the elastomer ratio are reported and analyzed in
numerous papers [1–3]. The dependences given by
different authors are essentially different.
The diversity of the trends observed is apparently
due to different conditions of compounding and
different degrees of NR plasticization in its
compounding with other rubbers. It is known that
compounding of rubbers of different nature results in
formation of predominantly heterophase systems in
which the components are separated by a layer of
segmental solubility and by thicker boundary layers of
phases, consisting of macromolecules with altered
supramolecular organization. The density of the layer
of segmental mutual diffusion is lower than the
additive value [1, 2]. The density of the boundary
layers depends on the nature of the contacting
polymers. Changes in the supramolecular structure and
density of macromolecule arrangement in the
interphase area can be manifested in changed mobility
of carbon atoms and separate atomic groups of the
macrochains. These atoms and groups can differently
respond to contact between two different polymers.
In this study we examined changes in the mobility
of chain fragments arising when rubbers of different
chemical structures are compounded. This character-
istic can offer important information on the structural
state of macromolecules and of the system as a whole.
The mobility of the atomic groups in macro-
molecules of rubbers and their blends was evaluated by
C nuclear relaxometry. To study the rheological
aspect of compounding of NR blends differing in the
degree of plasticization with SKMS-30ARK rubber,
we determined the viscosities of the systems obtained.
The composition dependence of the viscosity is plotted
in Fig. 1. NR–SKMS-30ARK rubber blends were
prepared under the same conditions, both for
individual rubbers and for their compounds, on 320–
160/160 laboratory rollers to eliminate the effect of the
blending time on the viscosity. Filled rubber stocks
containing (wt proportion)  rubber 100, stearin 2.5,
sulfenamide Ts 0.1–1.2, sulfur 2–2.5, and P-324
carbon black 50 were prepared in a 4.2-l rubber mixer
with oval rotors at a rotation rate of 40 rpm for 12 min.
Experiments with increasing content of the
vulcanization accelerator and decreasing sulfur content
in the blend were performed with an increase in the
BSR amount in NR–BSR compounds, so as to equalize
the vulcanization kinetics and attain equal degree of
cross-linking with further vulcanization of rubber
stocks. Two cases of variation of the viscosity of NR–
BSR blends were considered. In the first case (Fig. 1a),
AND POLYMERIC MATERIALS