The use of photoinitiators in the UV curing process shows remarkable possibilities in myriad applications. Highlighting critical factors such as reactivity, cure speeds, and application details, Industrial Photoinitiators: A Technical Guide is a practical, accessible, industrially oriented text that explains the theory, describes the products, and outlines the practice in simple language for the novice and expert alike.
The basics of UV light
The book begins by examining the nature of UV light and the types of commercial UV lamps that are available. It discusses the light absorption process and the excited states that are produced by the photoinitiator prior to the production of radicals. Next, the book examines the structure of the photoinitiator and the mechanism by which a reactive species is formed, along with the deactivating processes that inhibit the various photophysical and photochemical steps that occur as radicals are produced.
Commercial photoinitiators
Providing a list of companies and suppliers, the author explores the distinct groups of commercial photoinitiators and the variations in their structure. He describes the factors that determine which photoinitiators should be chosen for a particular application and how the different types are used. He also explains the reasons why a cured coating may display yellowing and describes the use of stabilizers to reduce the yellowing effect.
Cationic curing
Exploring a small but growing area of interest in the UV curing industry, the book concludes by discussing cationic curing and examines the different scope of parameters and different chemistry involved. It also describes factors that affect the use of cationic photoinitiators.
Based on more than 30 years of experience working with photoinitiators, W. Arthur Green offers a unique resource that provides product developers and others working in industry with the practical information they need to fully understand the basics of this evolving field.
Let there be light
The electromagnetic spectrum
The generation of UV energy
The light absorption process
UV safety and ozone
A little chemistry
Free radical chemistry
The chromophore and absorption of UV energy
Type I photoinitiators: Mechanism of the scission process
Type II photoinitiators: Mechanism of the abstraction process
The influence of molecular substitution on absorption and photoactivity
Photobleaching
Diverse mechanisms: Variations on the Type I and Type II process
The thiol-ene photopolymerization
Academics unlimited
Triplet lifetimes and monomer quenching reactions
Modification of hydroxyacetophenones
Alkylaminoacetophenones and wavelength selection
Phosphine oxides: Reactivity and solvolytic stability
Benzophenone and thioxanthone triplet reactions
Substituted benzophenones
Substituted thioxanthones
Novel photoinitiators
Radical reactions
Commercial photoinitiators
Type I photoinitiators
Type II photoinitiators
Blends of photoinitiators
Migration and polymeric photoinitiators
Visible light curing
Water-based UV curing
Hydrogen donors
Factors affecting the use of photoinitiators
Matching the photoinitiator absorption to the UV source
Photoinitiators for UV LEDs
Oxygen inhibition
Film thickness, surface and depth cure, shrinkage and adhesion
Sensitization and synergy
The effect of pigments on the UV curing process
Photoproducts and the yellowing of coatings
Intrinsic color, photoyellowing, and oxidation products
The formation of photoproducts
Cationic chemistry
The light absorption process and the generation of acid
Epoxy polymerization and the dark reaction
Triarylsulphonium salts
Dialkylphenacylsulphonium salts
Diaryliodonium salts
Ferrocenium salts
Factors affecting the use of cationic photoinitiators
The influence of the anion
Photochemical radical decomposition of onium salts
Sensitization of the cationic photoinitiator
The influence of temperature on the polymerization
The effect of water on polymerization
Appendix A: Tables and absorbance graphs
Appendix B: Further information
Index
Biography
W. Arthur Green received his degree in industrial chemistry in 1964 and has more than 40 years of experience working with photoinitiators. Since his retirement, he has continued to work part-time in the UV curing industry as a technical advisor and still presents papers and takes part in training sessions for companies involved in photoinitiators.
