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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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