1070-4272/05/7809-1531+2005 Pleiades Publishing, Inc.
Russian Journal of Applied Chemistry, Vol. 78, No. 9, 2005, pp. 1531!1537. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 9,
2005, pp. 1556!1562.
Original Russian Text Copyright + 2005 by Mamedov.
AND POLYMERIC MATERIALS
Sulfur-Free Vulcanization of Modified Butadiene!Acrylonitrile
Rubber SKN-40PVKh-30, Aimed To Obtain
Elastomeric Materials Resistant to Aggressive Media
Sh. M. Mamedov
Institute of Radiation Problems, National Academy of Sciences of Azerbaijan, Baku, Azerbaijan
Received November 17, 2004; in final form, April 18, 2005
Abstract-A study was made of the thermal, peroxide, and radiation vulcanization of modified buta-
diene3acrylonitrile rubber SKN-40PVKh-30 in the presence of a polyhalomethyl compound, 1,4-bis[(4-
trichloromethylphenyl)dichloromethyl]benzene, with epoxy and phenol3formaldehyde resins and 4,4`-
dithiobis-N-phenylmaleimide (a sensitizer) additionally included in the formulation with the aim to improve
the technical properties of the vulcanizates and elastomeric materials. The parameters of the three-dimensional
network of the vulcanizates were studied by sol3gel analysis; the total number of active chains of the network
), number of cross-linked molecules (1/M
), and gel fraction content were determined for the thermal,
peroxide, radiation, and thermoradiation vulcanizates.
Sulfur-free vulcanizing systems find growing use
in industry for preparing thermally stable vulcanized
rubbers resistant to thermal oxidative aging and other
effects. The most widely used are vulcanizing systems
based on organic peroxides, synthetic resins, and
polyhalo and other active additives capable of reacting
with macromolecules to form three-dimensional elas-
tomer structures based on C3C cross-links .
Depending on the conditions of elastomer vulcani-
zation with low-molecular-weight additives, the reac-
tions occurring in the system result in formation of
not only cross-links but also groups that are located
beyond the network points subsequently transforming
into cross-links. These processes are considered as
formation of heterogeneous vulcanization structures
Recently there has been much interest in the forma-
tion of vulcanization structures using new organic
cross-linking agents, modifiers, and sensitizers for
butadiene3acrylonitrile rubbers (BNRs) .
When stored or used in chemically and physically
aggressive media in contact with water, oil, oil-bear-
ing fluids, clay suspensions, and fuel, elastomeric
materials (EMs) prepared from SKN-40 and SKN-
40M rubbers vulcanized with sulfur-containing cross-
linking agents degrade because of the cleavage of
chemical bonds [4, 10].
One of the major factors affecting the resistance to
aggressive media and mechanical characteristics of
EMs is formation of chemical structures, i.e., vulcani-
zation bonds, in elastomers. The use of different
cross-linking agents and procedures results in forma-
tion in the elastomer of different types of three-dimen-
sional bonds, which, in turn, affects the service life
of EMs [1, 10].
Effective additives in preparation of vulcanization
structures are polyhalomethyl compounds (PHMCs)
such as 1,4-bis[(4-trichloromethylphenyl)dichloro-
methyl]benzene, epoxy (ERs) and phenol3formalde-
hyde (PFRs) resins, dicumyl peroxide (DCP), and
4,4`-dithiobis-N-phenylmaleimide (DTBPMI) accel-
erating radiation-induced vulcanization of elastomers
[8, 11]. It was also found [12, 13] that the service life
of EMs operating under various conditions can be pro-
longed by varying the vulcanization structures. How-
ever, the role of PHMCs, ERs, DCP, and DTBPMI as
cross-linking agents and sensitizers in radiation-
induced processes is poorly understood, and the avail-
able data are scarce.
In this study we examined the vulcanization of a
modified BNR, SKN-40PVKh-30, induced by heating
and g-irradiation with simultaneous introduction of
a PHMC, 1,4-bis[(4-trichloromethylphenyl)dichloro-
methyl]benzene, as cross-linking agent, of epoxy
and phenol3formaldehyde resins as modifiers, and of