Volatile Reactive-Diluent Loss During Handling and Cure: Composition Drift, Emissions, Surface State and Requalification

Reactive diluents reduce viscosity and participate in network formation, but some can also leave an uncured or curing formulation by volatilisation. The resulting problem is not captured by total mass loss, total volatile organic compound concentration, viscosity or final conversion alone. A defensible assessment must distinguish loss from the liquid formulation, atmospheric transport, chemical conversion, reaction-driven redistribution and later outgassing from the cured article. This review defines a measurement and requalification architecture for volatile reactive-diluent loss during storage-like handling, heating, deposition and cure. It combines time-resolved gravimetry with speciated chemical analysis, process-state sampling, surface-versus-bulk measurement where selective loss is plausible, cure kinetics and end-use response. The evidence supports formulation-specific mass and species balances and shows why emissions measurements cannot be converted automatically into resin depletion. It does not establish a universal loss limit, open time, processing temperature, replenishment rule, surface-to-core gradient or exposure-control instruction.