Industrial Photoinitiators: A Technical Guide

by Green; W. Arthur

• ISBN13: 9781439827451
• ISBN10: 1439827451
• Edition: 1st
• Format: Nonspecific Binding
• Copyright: 2010-04-22
• Publisher: CRC Press

Summary

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 lightThe 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 photoinitiatorsProviding 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 curingExploring 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. 

Author Biography

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.

Table of Contents

Acknowledgments	p. xiii
Introduction	p. xv
Let there be light	p. 1
The electromagnetic spectrum	p. 1
The generation of UV energy	p. 2
The medium-pressure mercury lamp	p. 3
The standard mercury arc lamp	p. 3
The electrodeless microwave-powered UV lamp	p. 5
Wavelength output of the medium-pressure mercury lamp	p. 7
Doped lamps	p. 8
The low-pressure mercury lamp	p. 10
The high-pressure mercury lamp or capillary lamp	p. 10
Flash lamps	p. 10
Fluorescent lamps	p. 11
Excimer lamps	p. 11
Light emitting diodes	p. 11
Lasers	p. 12
The light absorption process	p. 13
UV safety and ozone	p. 15
References	p. 15
A little chemistry	p. 17
Free radical chemistry	p. 17
The chromophore and absorption of UV energy	p. 18
The generation of radicals	p. 18
The polymerization process	p. 20
Type I photoinitiators: Mechanism of the scission process	p. 22
Alpha-scission	p. 22
Beta-scission	p. 23
Type II photoinitiators: Mechanism of the abstraction process	p. 24
Hydrogen abstraction from a donor molecule	p. 24
Intramolecular ¿-hydrogen abstraction: The Norrish Type II reaction	p. 25
The influence of molecular substitution on absorption and photoactivity	p. 26
Type I photoinitiators: Substitution effects	p. 27
Type II photoinitiators: Substitution effects	p. 28
Commercial photoinitiators	p. 30
Photobleaching	p. 31
Diverse mechanisms: Variations on the Type I and Type II process	p. 33
Acyloximino esters	p. 33
Anthraquinones	p. 34
BCIM and the lophyl radical	p. 35
Benzoylformate esters	p. 36
Substituted maleimides as photoinitiators	p. 37
Phosphine oxides and secondary scission	p. 38
Photo-acid generation	p. 39
Photo-base generation	p. 41
Anthracene peroxy radicals	p. 42
The thiol-ene photopolymerization	p. 43
References	p. 45
Academics unlimited	p. 47
Triplet lifetimes and monomer quenching reactions	p. 48
Modification of hydroxyacetophenones	p. 49
Alkylaminoacetophenones and wavelength selection	p. 50
Phosphine oxides: Reactivity and solvolytic stability	p. 53
Benzophenone and thioxanthone triplet reactions	p. 54
Substituted benzophenones	p. 58
Substituted thioxanthones	p. 60
Novel photoinitiators	p. 64
Radical reactions	p. 66
Primary radical reactions	p. 67
Recombination reactions	p. 67
Rearrangement reactions	p. 68
Disproportionation reactions	p. 69
Oxygen effects and chain transfer	p. 70
Termination reactions	p. 71
Identification of radicals and excited states	p. 71
References	p. 72
Commercial photoinitiators	p. 75
Type I photoinitiators (see Tables A.1 and A.2)	p. 75
Hydroxyacetophenones	p. 75
Alkylaminoacetophenones	p. 77
Benzil ketals and dialkoxyacetophenones	p. 78
Benzoin ethers	p. 79
Phosphine oxides	p. 80
Specialties	p. 82
Acyloximino esters	p. 82
BCIM and HABIs	p. 82
Photoacid generators	p. 83
Alphahaloacetophenones	p. 84
Trichloromethyl-S-triazines	p. 84
Photobase generators	p. 85
Type II photoinitiators	p. 86
Benzophenones	p. 86
Substituted benzophenones	p. 87
Thioxanthones	p. 88
Anthraquinones	p. 89
Benzoylformate esters	p. 90
Camphorquinone	p. 91
Blends of photoinitiators	p. 91
Migration and polymeric photoinitiators	p. 93
Migration of low-molecular weight species	p. 93
Polymeric photoinitiators	p. 95
Polymeric Type I photoinitiators	p. 98
Polymeric Type II photoinitiators	p. 98
Polymeric aminobenzoate hydrogen donors	p. 99
The "Nestlé list"	p. 99
Visible light curing	p. 99
Titanocenes	p. 101
Dibenzylidene ketones	p. 101
1,2-Diketones	p. 101
Ketocoumarins	p. 102
Dye sensitized photoinitiation	p. 102
Dye plus coinitiator	p. 102
Dye plus borate salt	p. 103
Dye plus HABIs	p. 103
Dye plus S-triazine	p. 103
Water-based UV curing	p. 103
Hydrogen donors	p. 105
Tertiary amines	p. 106
Alpha-amino acids	p. 108
Other types of hydrogen donor	p. 108
References and further reading	p. 109
Factors affecting the use of photoinitiators	p. 115
Matching the photoinitiator absorption to the UV source	p. 115
Absorption properties	p. 115
Formulating for LED UV	p. 116
Type I photoinitiator LED systems	p. 117
Type II photoinitiator LED systems	p. 117
The use of ITX as a sensitizer for LEDs	p. 118
Oxygen inhibition	p. 118
Radical-oxygen interaction	p. 118
Nitrogen and carbon dioxide inertion	p. 119
The effect of viscosity on cure	p. 121
Film thickness, surface and depth cure, shrinkage and adhesion	p. 123
Surface and depth cure	p. 123
Shrinkage and adhesion	p. 127
Sensitization and synergy	p. 128
Sensitization	p. 128
Synergy	p. 130
The effect of pigments on the UV curing process	p. 131
Pigment absorption and the pigment window: Choice of photoinitiator	p. 131
Replacing ITX	p. 133
Titanium dioxide whites and carbon blacks	p. 134
References and further reading	p. 136
Photoproducts and the yellowing of coatings	p. 139
Intrinsic color, photoyellowing, and oxidation products	p. 139
The formation of photoproducts	p. 139
Photoproducts from Type I photoinitiators	p. 140
Photoproducts from Type II photoinitiators	p. 145
References	p. 147
Cationic chemistry	p. 149
The light absorption process and the generation of acid	p. 150
Triphenylsulphonium salts	p. 150
Diphenyliodonium salts	p. 151
Epoxy polymerization and the dark reaction	p. 153
The polymerization process	p. 153
The effect of alcohols and chain transfer	p. 154
Hybrid cure	p. 155
Triarylsulphonium salts (see Tables A.7 and A.8)	p. 155
Sulphonium salts that may release benzene	p. 156
Sulphonium salts that are "benzene free"	p. 157
Dialkylphenacylsulphonium salts	p. 160
Diaryliodonium salts	p. 160
Iodonium salts that may produce benzene	p. 162
Iodonium salts that are "benzene free"	p. 162
Ferrocenium salts	p. 164
References and further reading	p. 165
Factors affecting the use of cationic photoinitiators	p. 167
The influence of the anion	p. 167
Photochemical radical decomposition of onium salts	p. 168
Sensitization of the cationic photoinitiator	p. 169
Extension of absorption wavelength by a sensitizer	p. 169
Sensitizers for cationic photoinitiators	p. 170
The influence of temperature on the polymerization	p. 170
The effect of water on polymerization	p. 172
References and further reading	p. 172
Tables and absorbance graphs	p. 175
Further information	p. 279
Index	p. 283
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