Prior to use, Dow Corning gels and elastomers should be kept sealed against
dirt and excess moisture. Any contaminants that find their way into the
gel prior to use will most likely find their way into your parts.
Dow Corning gels and elastomers can be dispensed manually or using one of
the many different types of meter mix equipment available. Typically the
two components are of matched viscosity and are readily mixed with a static
mixer.
| When manually mixing and dispensing, a thorough mix is
required. Best practices suggest putting the B part into the mixing dish
first. |  | A flat spatula or mixing tool should be used as it gives you
the ability to scrape the bottom and sides of the dish. After the A part
is added a good thorough mixing is required. |  |
Many of Dow Corning’s gels and elastomers are available in color-coded parts.
When mixed, the resulting color should be uniform. Streaks are
evidence of inadequate mixing. |  |
A good practice when hand mixing is to time your mixing, cure the sample and
test some of the physical properties (hardness or durometer are usually good
indicators) against the data sheet. If the properties are close, then you
have probably mixed thoroughly. If the properties are significantly
different, a longer mix time is warranted.
| During the mixing process, especially in hand mix applications;
air may be introduced into the gel or encapsulant. Entrapped air in the
mixture can be removed by using 28 inches (0.9 bar) of vacuum. |  | The container should be one fourth full or less to avoid
overflowing, as large bubbles will be formed almost immediately. |  | These should be collapsed by introducing atmospheric pressure
and then continuing the vacuum. |  |
The time for deairing to happen will be dependant on the amount of air in
the material and the viscosity of the material. In deairing high
viscosity encapsulants, it may be necessary to release and reapply the vacuum
several times to break the bubbles that form.
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