Primer Chemistry for Photocurable Interfaces: Coupling Reactions, Film Thickness, Cure Compatibility and Recoat Windows

A primer is not qualified by its name, nominal concentration or initial contact angle. It is an interphase whose substrate-facing anchoring, deposited mass and continuity, drying or condensation state, outward-facing functionality and compatibility with the overlying photocure must all be demonstrated. Time between priming and coating is likewise not a universal open time: the surface changes through reaction, adsorption, migration, contamination and physical ageing.

This review defines a state-resolved primer qualification framework. It separates substrate anchoring from coating-facing reactivity; treats thickness, coverage and surface segregation as measured variables; checks whether the primer inhibits, absorbs, consumes or participates in the photocure; and maps recoat performance against both elapsed time and interphase state. Mechanical evidence is interpreted with conversion, chemistry, morphology and failure locus. The evidence supports two-sided verification across silane, polyolefin, coating and polymerisable primer systems. It does not establish a commercial formulation, universal film thickness, drying schedule, recoat window, cure compatibility rule, adhesion threshold or durability claim.