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Dow Corning offers two thermal cure chemistries for silicone release coating
products:
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Addition Cure, catalyzed by platinum or rhodium
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Condensation Cure, catalyzed by tin
Addition Cure
Addition-cure chemistry has been successfully applied to solventless,
solvent-based and emulsion coatings alike. In this cure system, the addition of
a silicon hydride group across a vinyl (or hexenyl) group is catalyzed by a few
parts per million of an organoreactive platinum (or rhodium) complex. There are
no "leaving" groups, so nothing is evolved during cure. And
"post-cure" (if any) is minimal.
Condensation Cure
The tin-catalyzed condensation reaction has long been the
"workhorse" of the release coating industry. Coatings consist of a
silanol-functional polymer, a diluent and a silicon-hydride crosslinker. Cure
is initiated at elevated temperatures by high levels of a tin-salt catalyst.
Cure takes place relatively slowly - generally speaking, the lower the
temperature, the slower the cure. Once initial cure is complete, a period of
post-cure is required to complete the reaction.
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