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After applying the coating by one of the processes above, it can be cured in
one of the following conditions, depending on the product family being
used.
Room Temperature Cure
A room temperature cure process can be used for either the RTV
Elastomeric or RTV Elastoplastic Coatings. After application, the
coating is simply allowed to cure in ambient room conditions (roughly 70°F/21°C
and 30-80% relative humidity). These materials cure by using moisture in
the air. On exposure to the air, the coating will begin to cure.
During cure, roughly 3-6 weight % of methanol will be evolved.
Adequate ventilation should be provided. In addition, the RTV
Elastoplastic Coatings are supplied in solvent and provisions must be made
for solvent removal. Please contact Dow Corning's Solutions Unit for
process design guidance.
The coatings will be handleable on the device in about 5-60 minutes
depending on the product chosen and the thickness of the coating. Full
cure should occur in 24 hours in the typical thicknesses used for conformal
coatings.
If the coating is being dip coated, that is applied from a bath, it should
be covered as much as possible, especially during downtime. Blanketing
with dry air or nitrogen is also helpful in extending bath life. If
material is being used from its original container, it should be kept closed
when not in use.
Simple room temperature curing processes are more appropriate for low to
medium volume applications. Some of the RTV Elastomeric Coatings
are designed for fast tack free times and faster processing.
Simple ambient curing is not possible for the Solventless Heat Cure
Coatings.
Mild Heat Acceleration
All of the above considerations for room temperature curing apply for
coatings which cure with mild heat acceleration. However, after applying
the coating and allowing a few minutes at ambient conditions, the coated part
can then be elevated to modest temperatures up to about 60C for 5-10 minutes.
This will help achieve more complete cure in this surprisingly short
time. Temperature can be provided in a batch or belt oven.
This process is more useful for volume production but is also not
appropriate for the Solventless Heat Cure Coatings.
Heat Curing Above 100C
True heat curing is done above 100C rather than at the milder temperatures
described above. The Solventless Heat Cure Coatings do not require
moisture for cure. All of the components needed for cure are included in
the material as supplied. After application, the coating simply needs to
be brought to elevated temperatures in order to cure. This can be done in
a batch or belt oven.
Heat curing at these elevated temperatures is not appropriate for the
RTV Elastomeric or RTV Elastoplastic Coatings.
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