In-Can Stability, Latency and Premature Cationic Polymerisation in Light-Curable Formulations
Segurola, Juan
2026-09-14 · Informe · Versión 0.3
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Cationic photopolymerisation is commercially established in coatings, inks, adhesives, release coatings, photoresists and selected additive-manufacturing formulations, but its storage and latency controls differ fundamentally from those of free-radical systems. A cationic formulation can fail before intended exposure through thermal, photochemical or redox activation of the photoacid generator; after even a short exposure it can continue through dark cure because protonic or oxonium centres may remain active. The same ingredient may increase intended cure while reducing shelf stability, or suppress acid migration while decreasing conversion and cure depth. This review develops a mechanism-led qualification framework for epoxy, oxetane, vinyl-ether and related cationically curable formulations. It compares onium-cation and counterion choices; reversible proton traps, acid scavengers, photobuffers, humidity blockers, microencapsulation, initiator purity and two-component supply; and the conditional use of radical inhibitors when a radical- promoted acid-generation route exists. Particular attention is given to water, hydroxyls, amines, sulfides, ionic contaminants, pigments, dyes, silica, clays, carbonaceous fillers, package contact and optical attenuation. Public commercial documentation is segregated from peer-reviewed evidence. No universal stabiliser, optimum counterion, shelf-life threshold or transferable dosage is proposed. The required output is a formulation- and package-specific stability window that preserves both storage integrity and the complete intended cure response.