AdditionCured

Additioncured is a term used in polymer science to describe materials that cure via addition reactions rather than condensation or radical polymerization. In an addition-curing system, crosslinks form by direct addition between functional groups, typically with no release of small molecules.

The best-known example is addition-cure silicone elastomers, which cure via hydrosilylation: vinyl groups on siloxane strands react with Si-H crosslinker in the presence of a platinum catalyst to form a three-dimensional network. These systems are often supplied as two-part formulations that cure at room temperature or elevated temperatures.

Advantages: no byproducts, minimal shrinkage, high dimensional stability, low odor, excellent aging and chemical resistance, and predictable cure. They are favored in medical and electronics uses.

Applications include dental vinyl polysiloxane (VPS) impression materials; encapsulants for electronics; medical devices; aerospace adhesives.

Limitations and considerations: cost of platinum catalysts; sensitivity to poisons (sulfides, amines); catalyst deactivation; sometimes longer cure times; formulation complexity.

In contrast, condensation-curing systems release volatile byproducts (water, alcohol) and can exhibit more shrinkage or odor.