Chemistry Reference
In-Depth Information
system, which, due to presence of the double bonds, may be cross-linked
with conventional systems, which are of relatively low price, good con-
tents miscibility and ability to be used within the temperature range 233-
408 -K [11-15].
Next level in the field of thermoplastic elastomers began with develop-
ment of the metallocene catalysts and their use in stereo block polymeriza-
tion of ethylene and propylene and copolymerization of these olefins with
other monomers, leading to macromolecules with a “customized” structure
with a microstructure and stereo regularity defined upfront. The catalysts
enabled production of the homogeneous olefin copolymers, which have
narrow distribution of molecular weights (RCC=M
w
/M
n
<2.5). According
to the developed technology called Incite and using the on-place catalyst
[16, 17]. The Dow Chemical Co company produces the olefin elastomers
Engage
TM
which contain over 8% of octene. Co-polymers Engage are
characterized by lack of relation between the traditional Mooney viscosity
and the technological properties. Compared to other homogeneous poly-
mers with the same flow index, they are characterized by higher dynamic
viscosity at zero coagulation speed and decreasing viscosity at increasing
coagulation speed. They have no fixed yield point. Saturated nature of
elastomer, caused by absence of diene in the chain, results in some restric-
tions in choice of the cross-linking system. The ethylene-octene elasto-
mers can be easily radiation cross-linked with peroxides or moisture, if
they are formerly grafted with silanes. There is relatively not much de-
scription of the behavior of the ethylene-octene elastomer in the dynamic
vulcanization process in the literature. The specific physical properties of
such elastomers and possibility to process them within a periodic process
as well as within a continuous process, due to convenient form of the com-
mercial product (granulate) encouraged us to start the recognition works
on development of the technology of producing thermoplastic vulcani-
zates from the mixture of elastomer Engage and iPP.
Use a silane-based cross-linking system in the dynamic vulcaniza-
tion process seemed the most interesting. For the research works one of
the known methods of cross-linking poliolefins with silanes was used,
assuming that the cross-linking of EOE would proceed according to the
analogous mechanism. In the seventies of the twentieth century the Dow
Corning Co. company developed two methods of the hydrolytic cross-
linking of polyolefins grafted with vinylosilanes according to the radical
mechanism [18, 19]. Nowadays three polyolefin cross-linking methods
