Russian Journal of Applied Chemistry, 2011, Vol. 84, No. 11, pp. 1988−1992.
Pleiades Publishing, Ltd., 2011.
Original Russian Text © O.G. Khelevina, 2011, published in Zhurnal Prikladnoi Khimii, 2011, Vol. 84, No. 11, pp. 1903−1907.
AND POLYMERIC MATERIALS
Cross-Linking of Liquid Low-Molecular-Weight Siloxane
Rubbers with Orthotitanic Acid Esters
O. G. Khelevina
Ivanovo State University of Chemical Technology, Ivanovo, Russia
Received March 18, 2011
Abstract—The kinetics of cross-linking of SKTN liquid low-molecular-weight siloxane rubbers with orthotitanic
acid esters (tetraethoxytitanium, tetrapropoxytitanium, tetrabutoxytitanium) was studied. The effective rate constants
of the cross-linking at 130, 140, 150, and 160°С and the activation energies of the reaction were calculated. The
effect of a catalyst, tin phthalocyanine, on the cross-linking of SKTN liquid rubbers with orthotitanic acid esters
Vulcanization of polyorganosiloxanes containing
terminal silanol groups with orthotitanic acid esters was
studied in [1–5]. At elevated temperatures (above 100°С),
the vulcanization occurs at high rate in accordance with
Scheme (1) reﬂ ects only the ﬁ nal result of the cross-
linking. The cross-linking reaction occurs in steps,
and at room temperature soluble polymers are formed
. Thus, in the first steps of the cross-linking the
orthotitanic acid esters react as bifunctional compounds,
increasing the molecular weight of the linear molecules.
Condensation of polysiloxanediols with orthotitanic acid
esters occurs via formation of an intermediate complex
of two polysiloxanediol molecules with one molecule of
orthotitanic acid ester (RO)
Ti, which is favored by high
coordination power of titanium (the coordination number
of titanium is 6 ).
The formation of Ti–O–Si bonds in the course of
vulcanization of polysiloxanediols with orthotitanic acid
esters is conﬁ rmed by a characteristic band at 980 cm
in the IR spectra, assigned to stretching vibrations of
Ti–O–Si bonds [4, 7].
Despite the fact that vulcanization of polysiloxanediols
with orthotitanic acid esters was the subject of numerous
studies, the kinetics of this reaction was not examined,
which does not allow substantiated choice of vulcanization
process parameters. The effect of catalysts on the course
of the cross-linking was not examined either.
This study concerns the kinetics of cross-linking of
SKTN liquid low-molecular-weight siloxane rubbers with
orthotitanic acid esters and the effect of catalysts on the
For our experiments we chose SKTN-A and SKTN-G
low-molecular-weight siloxane rubbers with molecular