Meaning
Radical generation efficiency depends on the chemical cleavage of tertiary amines during free radical photopolymerization, a mechanism known as amine co-initiator dealkylation. This specific reaction sequence consumes electron donors to accelerate cure kinetics in ultraviolet-curable acrylate coatings and moulding formulations. The boundary of this definition sits at the point where hydrogen abstraction completes and polymerization termination pathways begin.
Formulators track this property to control crosslink density in thick-section photopolymers.
Radical Kinetics
Photocuring speeds rely on the rate at which amine co-initiator dealkylation supplies active radicals to unsaturated oligomers. Tertiary amines transfer an electron to an excited photoinitiator molecule, creating an exciplex intermediate prior to proton transfer. Subsequent carbon-nitrogen bond cleavage yields alpha-amino alkyl radicals capable of initiating monomer addition.
High reaction rates prevent oxygen inhibition at the surface of extruded films and injection-moulded sheets.
Resin Yield
Chemical suppliers adjust raw material purity to optimise amine co-initiator dealkylation during high-speed UV moulding operations. Virgin polymer batches maintain predictable stoichiometry, whereas regrind materials introduce variable contaminant levels that interfere with electron transfer efficiency. Part specifications dictate strict allowable limits for unreacted monomer fractions within finished mouldings.
Excess residual odour and surface tackiness appear when molecular cleavage proceeds incompletely across the production run.
Processing Limits
Machine operators control lamp intensity and web speed to match the kinetics of amine co-initiator dealkylation during continuous sheet extrusion. Datasheet values assume ideal laboratory exposure conditions that industrial tooling configurations rarely replicate. Production throughput must be balanced against thermal degradation risks caused by exothermic peak release during rapid polymer network formation.
Moulded components exhibit dimensional distortion and micro-voiding when the polymerisation rate outpaces volatile outgassing from the resin matrix.
