|
Beyond the typical characteristics of our general purpose gels, certain
applications are uniquely sensitive and require specialized properties.
Low Volatility Silicone Gels
For some uses, low molecular weight volatiles from the gels can result in
problems. This can range from re-condensing volatiles onto surfaces, which can
interfere with adhesion or can lead to decomposition under high voltage or
very high temperature conditions. They can also re-condense and obscure/fog
optical surfaces. For these cases, there are low volatility products that can
be used.
Low Extractable Gels
Gel extractables may be measured by determining the weight loss of a cured gel
after immersion in a solvent. The weight loss represents the gel fraction from
the cured material in a swollen state. Compared to standard gels, 3-4130
Dielectric Gel offers approximately 25-50 percent less extractables with
methyl ethyl ketone (MEK) as the solvent.
Extreme Low Temperature Products
Dow Corning ® brand silicone gels can typically withstand cold environments
down to at least –45°C(-49°F). For even colder uses, there are specialized
products that will perform down to –80°C.
Toughened Gels
For applications that require gels with added strength, there is a family of
tough or firm gel products. These materials also have enhanced chemical
adhesion, but cure slightly harder than standard gels. Some of the products
allow rapid room temperature curing and some contain UV dyes for easy
inspection.
Optically Clear Materials
For optical applications, many of the silicone gels are highly transparent in
many wavelength ranges including the visible range. These materials have some
of the highest transmission values of any polymeric materials in selected
wavelength ranges.
Thermally Conductive Gels
Most gels are formulated without fillers. However, for applications that
require heat dissipation and the soft nature of silicone gels, there are some
products that include conductive fillers. This significantly increases the
thermal conductivity values of these materials to > 0.8 watts/meter-K.
One-Part UV Curing Gels
The most common cure mechanism for silicone gels is room temperature or heat
accelerated addition cure, which meets the needs for most processes. However,
for applications requiring extremely rapid cure, there are products which cure
with UV light exposure. This allows cure within seconds and in the presence of
temperature sensitive components. Generally, deep section cure is not possible
with these materials.
One-Part Heat Curing Silicone Gels
Most of the silicone gels are supplied as 1:1 mix ratio two-part products.
For easy processing without the need for mixing, there are one-part gels
available. These have long room temperature storage lives but require high
heat exposure in order to cure and have generally longer curing times.
Solvent Resistant Gels
Standard silicone gels are non-polar and susceptible to swelling in solvents
and fuels. Fluorosilicone gels increase the polar nature of the material and
provide improved resistance in applications with solvent and fuel exposure.
Flame Resistant Gels
The materials used in certain applications are required to meet special
criteria such as those from Underwriters Laboratories for flammability. There
are gels which possess a UL 94V flammability classification.
Thixotropic Gels
Most gels are supplied as low viscosity liquids, but there are some products
that have been formulated with thixotropic properties. This gives them a
reduced tendency to flow and allows them to be more easily contained in
specific areas of a module.
|
Change
