1070-4272/01/7403-0483$25.00C2001 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 74, No. 3, 2001, pp. 483! 488. Translated from Zhurnal Prikladnoi Khimii, Vol. 74, No. 3,
2001, pp. 468!472.
Original Russian Text Copyright + 2001 by Usachev, Solov’eva, Solov’ev, Babyuk, Voronov.
AND POLYMERIC MATERIALS
Preparation of Chemically Cross-Linked Swollen Gels
from Spent Rubbers and Their Use
as Components of Rubber Stocks
S. V. Usachev, O. Yu. Solov’eva, M. E. Solov’ev, D. N. Babyuk, and V. M. Voronov
Yaroslavl State Technical University, Yaroslavl, Russia
Received December 23, 1999; in final form, March 2000
Abstract-A study was made of cross-linking of gelatinous compositions to obtain products classed with gels
of the first type in which a part of the plasticizer is firmly retained by the gel structure of the elastomer. The
elastic-hysteresis properties of the rubbers were studied.
According to the existing physicochemical con-
cepts of structure formation and properties of elasto-
mer blends, enhancement of fatigue-strength proper-
ties of rubbers based on them is due to a specific
structure of the boundary zone between the polymer
phases, incorporating along with the segmental inter-
diffusion layer also the boundary layers . A thin
contacting layer of one of the phases is characterized
by a less close packing of macromolecules and in
some cases by the lower degree of cross-linking .
The thinned layers provide efficient relaxation of
stresses, which is one of the causes of the mutual
reinforcement effect. Apparently, addition and distri-
bution in a rubber stock of microparticles of a poly-
meric substance with a fortiori thinned stated of
macromolecules due to filling of the interchain space
with a plasticizer could enhance the conformational
mobility of chains and accelerate relaxation of local
overstresses arising under applied mechanical field.
In this work we examined the efficiency of using as
such disperse phase swollen chemically cross-linked
polymer gels. Usually swollen polymer gels (polymer
jellies) are obtained from primary polymers . How-
ever, in our case it is interesting to prepare gels from
secondary polymeric materials, e.g., from spent rub-
bers, since products of spent rubber reprocessing are
widely used as components of rubber stocks, decreas-
ing their cost and modifying their properties.
Polymer jellies were prepared by plasticization of
crushed resins (CRs) of model composition and of
crushed spent heating tubes (HTs) which are an in-
evitable waste of tire production. Plasticization was
performed in hydrocarbon media at 1603200oC; the
CR : plasticizer ratio was 1 : 3. Model rubbers were
prepared from SKI-3 rubber; the polymer base of HT
rubbers was a combination of SKI-3 and SKD rub-
bers. As a plasticizer we used Vaseline oil which is
well compatible thermodynamically with SKI-3 and
SKD rubbers, and also PN-6sh aromatic oil whose
thermodynamic affinity for these rubbers is lower.
Plasticization at 1603200oC was performed until
visually uniform compositions were obtained; owing
to a low content of the polymer gel fraction and a
high content of the plasticizer, these gels can be
classed with jellies of the second type (swollen gels
with a physical network) . Degradation of the vul-
canization structure of CRs was monitored by varia-
tion of the content of the sol (S) and gel (G) fractions
and from the variation of the equilibrium swelling Q
of the insoluble fraction in toluene.
We calculated the index of degradation of the vul-
canization structure of the resins I
by the formula 
= Q(100 3 S),
where Q and S are expressed in percents.
For example, at the process temperature of 180oC
of the rubber in the final product obtained from
vulcanized unfilled SKI-3 rubber was 40.5, and the
viscosity-average molecular weight of the sol fraction
of the rubber was 42000.
Figure 1 shows variation with time of the gel frac-
tion content in HT reprocessing products heated in air
and in the Vaseline oil medium. It is seen that the