Page 2 - Jabar Catalog Silicone2

SILICONE rubber provides the
maximum in reliability – whether
exposed to adverse environmental
conditions, stored for indefinite periods,
or used under normal conditions.
Resisting conditions which normally
cause rubber to deteriorate, silicone
rubber offers a useful life which is
unmatched by other known elastomers.
It resists temperature extremes, ozone,
corona, radiation, moisture,
compression set, weathering, and
chemical attack.
Silicone has been with us since 1944,
and has gone through hundreds of
improvements. Originally sacrificing
physical strength and elongation, we
now have a large variety of compounds
available which provide resistance to a
broad range of temperatures with
excellent electrometric physical
properties.
When comparing elastomers for an
application, one should not only
consider the physical requirements. The
“Total Cost”, or the cost of the part
including purchase price, installation,
maintenance, and service life, should
also be considered. Many elastomers are
available at a much lesser cost than
silicone, but fail to provide the user the
reliability, and durability over an
extended period of time. Users should
consider the “Total Cost” package when
selecting or specifying silicone rubber
parts for an application.
CHEMICALLY, silicone rubber is quite
different from other elastomers. It is this
difference, which gives them their
unique combination of properties and
permit silicone to perform in many
applications where no other elastomer
can be used. The basic difference
between silicone polymers and
“Organic” polymers is in the molecular
make-up. Silicone or Dimethyl
Polysiloxane, is made up of
silicone/oxygen linkages, the same
found in high temperature materials
such as quartz, glass, and sand. Natural
rubbers, or Organic polymers, are made
up of carbon/carbon linkages. Many
organic polymers witness
“unsaturation” where carbon atoms are
joined together by double bonds,
making them susceptible to the adverse
affects of ozone.
Through altering the chemical make-up
of the silicones by adding phenyls, vinyl
and, fluorine’s, significant variations in
physical properties can be achieved. The
addition of phenyls improves low
temperature flexibility and resistance to
gamma radiation. Vinyl side groups
improve the vulcanization
characteristics and the compression set
of the cured material. Fluorosilicones
enable the user to witness the physical
properties inherent in standard silicone
and maintain resistance to solvents and
fuels.
TEMPERATURE EXTREME STABILITY is
silicones most outstanding property.
Under normal operating conditions,
temperatures as high as 500°F and as
low as -150°F do not destroy the
physical and electrical properties of
silicone. At elevated temperatures, the
tensile, elongation, and abrasion
resistance of silicone is far superior to
that of most organic elastomers. The
advantages of silicone over natural
rubbers is readily apparent in Figure
16A, which compares the effects of heat
aging at 400°F. To show the true
superiority of silicone, we have shown
the effects in increments of DAYS for
silicone, while the increments for
organic rubber are shown in HOURS.
Before aging, the organic rubber had
higher tensile and elongation
characteristics, but after only an hour
into the test the silicone shows to be the
elastomer of choice. As shown in Figure
16A, silicone shows stability throughout
the term of the test. The estimated
Useful Life of silicone at different
temperatures is shown in Table 16B We
consider the useful life to be the
elastomer’s ability to retain flexibility
(measured here in elongation). In many
applications, such as electrical cables,
and insulator pads, the flexibility
requirement may not be as critical,
extending the “Useful Service Life” far
beyond that indicated.
Já-Bar Si l icone Corporation • Phone: 973. 786-5000 • Fax: 973. 786-6067 • www.JaBar.com 2
FIGURE 16A
Technical Data
Mechanical Sealing Products