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Posted by BigCommerce on Jun 7th 2021

There are two types of silicone rubber:

Tin (condensation) cured and Platinum ( addition) cured silicone rubber. Both types has advantages and disadvantages and neither are compatible with one another. Silicone rubber is an excellent choice for making molds, they offer excellent strength, flexibility, and are self-releasing. The only thing RTV silicone will stick to is silicone itself. Tin (condensation) cured silicone rubber uses tin salts as a catalyst and uses moisture in the air to transform from liquid to solid. Platinum (addition) cured silicone rubber uses a platinum catalyst and uses heat to transform from a liquid to a solid. Platinum (addition) cured silicone’s can be heat accelerated, for every 10 degrees above 70°F you can reduce the cure time in half, so if you heat the platinum cured silicone at 150°F it will be ready to use in 20-30 minutes.
Tin (Condensation) Cured
+ Typically less expensive
+ Less prone to inhibition
+ Will cure in lower temperatures or over frozen patterns
+ Excellent physical properties
– Not FDA compliant for food or skin applications
– Typically higher shrinkage compared to platinum cured silicones
– Over a long period of time can lose its flexibility and strength
Platinum (Addition) Cured
+ Very long library life
+ Some are FDA compliant for food and skin contact
+ Excellent physical properties
+ High heat deflection (can withstand heat -like the oven up to 400°F)
+ Can be heat accelerated
– Prone to inhibition caused by poisonous substrates such as sulfur, tin, synthetic rubber, some adhesives, latex, nitrile, etc..
– Requires very accurate and careful mixing