Modified Fluororubbers Based on SKF-26:
Relaxation and Mechanical Properties
A. S. Ramsh, E. A. Sidorovich, G. P. Petrova, S. K. Kurlyand, M. V. Zhuravlev,
O. V. Blagodatova, N. V. Lebedev, and V. A. Gubanov
Lebedev Research Institute of Synthetic Rubber, Federal State Unitary Enterprise, St. Petersburg, Russia
Received August 5, 2010
Abstract—Samples of SKF-26 fluororubber modified by incorporating pendant methoxy groups into the
macromolecular chain were studied by dielectric spectroscopy and dynamic mechanical analysis.
ORGANIC SYNTHESIS AND INDUSTRIAL
ISSN 1070-4272, Russian Journal of Applied Chemistry, 2010, Vol. 83, No. 12, pp. 2172–2174. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © A.S. Ramsh, E.A. Sidorovich, G.P. Petrova, S.K. Kurlyand, M.V. Zhuravlev, O.V. Blagodatova, N.V. Lebedev, V.A. Gubanov, 2010,
published in Zhurnal Prikladnoi Khimii, 2010, Vol. 83, No. 12, pp. 2045–2047.
Methods of dielectric and dynamic mechanical re-
laxation furnish information on the phase state of
composites and on the expected temperature ranges in
which these materials can be efficiently used.
Our experiments were performed with SKF-26
rubbers [copolymers of vinylidene fluoride (VDF) and
hexafluoropropylene (HFP)] modified to various ex-
tents by introducing pendant methoxy groups into the
polymer chain . We expected that chemical modi-
fication with alkoxy groups will increase the glass α-
transition point depending on the degree of modi-
fication and on the distribution of the modifying
groups in the polymer chain.
For the initial unmodified SKF-26 rubber, the
temperature dependences of the dielectric loss tangent
tan δ at four frequencies (110 Hz; 1.1, 11, and
110 kHz) in the temperature range from –100 to
show that an increase in the frequency leads not only
to shift and considerable broadening of the α-transition
peak, but also to nontrivial increase in its intensity
(Fig. 1). The known β-transition at –45°C is clearly
seen at 110 Hz.
Figure 2 shows the temperature dependences of
tan δ at 110 Hz for a series of samples with methoxyl
With an increase in the degree of modification, the
intensity of the α-transition maximum observed for the
initial rubber at approximately +8°С decreases con-
siderably. First a step appears on the high-temperature
shoulder of the α-transition peak, and then it trans-
forms into a strong dielectric loss maximum at ap-
proximately +32°С. With a further increase in the
degree of modification, the temperature of this
maximum remains unchanged. At the highest degree of
modification, the “initial” maximum disappears.
The β-transition, which is due to uncompensated
dipoles in the polymer backbone, considerably de-
creases in intensity and is shifted toward negative
temperatures. Labile hydrogen atoms in the CH
fragment of the vinylidene fluoride unit of the macro-
Fig. 1. Dielectric loss tangent tan δ of SKF-26 rubber as a
function of temperature Т. Frequency applied: (1) 110 Hz,
(2) 1.1 kHz, (3) 11 kHz, and (4) 110 kHz.