Tincured

Tincured is a term used in polymer science to describe silicone elastomers and adhesives that are cured with tin-based catalysts, typically through condensation cure systems. The term distinguishes tin-cured formulations from platinum-cured silicones, which use a different catalyst and curing mechanism.

Chemistry and process: Tin-cured silicones rely on organotin catalysts such as dibutyltin dilaurate or stannous octoate to promote crosslinking between silanol groups and siloxane chains. Curing is often moisture-assisted and can occur at ambient or mildly elevated temperatures. Depending on formulation, byproducts such as acetic acid or alcohol may be released during cure, which can impart odor and, in some cases, affect metal parts or coatings.

Properties and applications: Tincured silicones are generally economical and cure readily at room temperature, with good adhesion to many substrates. They tend to cure faster than platinum-cured systems but may exhibit higher shrinkage, lower thermal stability, and potential sensitivity to moisture during storage. The acids released during curing can pose compatibility concerns with certain metals or coatings. Applications include general-purpose sealants, adhesives, potting compounds for electronics, automotive gaskets, and weatherproof seals.

Limitations and alternatives: Platinum-cured silicones, cured via platinum-catalyzed hydrosilylation, offer higher purity, better aging resistance, and no acidic byproducts, making them preferable for medical devices and high-precision electronics, albeit at higher cost. In some applications, formulators select tin-cured systems for cost reasons or for specific curing profiles.

Etymology and usage: The term derives from tin-based catalysts used in the curing process and is sometimes written as “tin-cured” or “tin-cure” silicone.