Tin-cured (or Condensation Cure) and Platinum-cured (or Addition Cure) is the most typical representative product of RTV silicone rubber, These two types of silicone rubber are usually used in the production of silicone molds. Both types has advantages and disadvantages and neither are compatible with one another. In order to help you choose the most suitable type of rtv silica gel, the difference between these two types of silicone rubber is listed below for your reference.
Principle of curing
Tin cured silicone rubber uses tin salts as a catalyst and uses moisture in the air to transform from liquid to solid.
Platinum cured silicone rubber uses a platinum catalyst and uses heat to transform from a liquid to a solid. In a platinum-based silicone cure system, a hydride- and a vinyl-functional siloxane polymer react in the presence of a platinum complex catalyst, creating an ethyl bridge between the two.
Tin-cured silicone is usually water white or translucent by default. Platinum-cured silicone is usually translucent or transparent (clear). As for other colors, silicone pigments can be added.
Tin cured silicone rubber uses tin salts (usually 2%~5%) , Platinum cured silicone rubber uses platinum catalyst (usually usually 100% or 10%) . Therefore , Platinum cured silicones require very accurate and careful mixing, but this is not the case with tin cure ones.
Cure inhibition is the failure of a compound to cure against a surface within the recommended cure time. The surface in contact with the pattern remains gummy or uncured.
Tin catalyst rubbers are not sensitive to inhibition, meaning they will cure at room temperature over virtually any surface.
Platinum-cure silicone rubbers are critically sensitive to sulfur or amines and will not cure under any circumstances when exposed. You cant use latex gloves while mixing them, nitrile or vinyl are the best choice.
In condensation curing, the polymer chains bond together via a crosslinker and ethanol is released as a by-product. Addition cure silicone rubberdoes not release any by-products during curing.
The hardness of tin-cured silicone is usually 5~40 Shore A, and the hardness of platinum-cured silicone is usually 0-50 Shore A.
The tin-cured silicone rubber shrinks slightly after curing, generally about 0.3%, while the shrinkage of platinum-cured silicon is relatively low, generally about 0.1%.
Tin cured silicone belongs to industrial grade silicone , Not FDA compliant for food or skin applications.
Platinum-cured silicone is odorless, food-grade, Certain formulations are safe to use directly on the skin, either for moulding or for building up realistic skin effects.
Tin cured variants are less expensive and also prove to be easier to use while platinum based ones turn out to be quite expensive.
Generally, Tin-cured silicones are more tear resistant than platinum- cured silicone, platinum- cured silicone offer exceptional heat resistance. If high temperatures are anticipated, then platinum-cured silicone are typically a better choice. But for economy, general mold making and prototype applications, tin-cured silicone rubber would be preferable.