Photoinitiation, Photopolymerization, and Photocuring

Transcription

1 Jean-Pierre Fouassier Photoinitiation, Photopolymerization, and Photocuring Fundamentals and Applications Hanser Publishers, Munich Vienna New York Hanser/Gardner Publications, Inc., Cincinnati

2 Contents 1 Introduction 1 References 7 2 Basic Principles in Photoinitiation Processes of Photoinduced Polymerization Reactions Photopolymerization Reactions Photoinitiators and Photosensitizers Properties of Photoinitiators 11 References 15 3 Cbemistry, Excited States, and Reactivity of Radical Photoinitiators Introduction to Excited-State Processes Cleavable Photoinitiators a-cleavage Process Benzoin Ethers [14-17] Hydroxy Alkyl Phenyl Acetophenones [18] Dialkoxy Acetophenones [21] Phosphine Oxide Derivatives [23] Amino Ketones [26] Laser Spectroscopy of Photoinitiators ß-Cleavage Process Miscellaneous Primary-Cleavage Processes Photoinitiators Involving H-Abstraction or Electron Transfer Reactions Other Mechanisms of Initiation Norrish II Photoscission Process Charge Transfer Complexes Miscellaneous Photoinitiators Cleavage Reactions, Electron Transfer, and Monomer Quenching Monomer Quenching Amine Quenching Competition Between Cleavage and Quenching by Amines and Monomers Solvent Effects Structure-Property Relationships Role of the Skeleton Role of the Substitution Role of the Amine Role of the H Donor 56

3 Contents ix Role of the Initiating Radical Role of the Environment Photochemistry in Upper Excited States Other Factors How to Design Photoinitiators Exhibiting Specific Properties Enhanced and Redshifted Absorption Water Solubility and Hydrophilicity Acid-Releasing Systems Hydrophobie and Oligomeric or Polymerie Photoinitiators Copolymerizable Photoinitiators Photosensitized Deeomposition of Radical Photoinitiators Processes Involved Photoinduced Bond Cleavage via Electron Transfer Reaction Sensitized Reactions in Photoinitiating Systems Photosensitized Cleavage and Photoinduced Electron Transfer in Combinations of Photoinitiators Visible Light Photosensitive Systems Multicomponent Systems One-Component Systems (the Photoinitiator) Two-Component Systems Three-Component Systems Mechanism Involved in Three-Component Systems 92 References 93 4 Chemistry, Excited-State Processes, and Reactivity of Cationic Photoinitiators Diazonium Salts Onium Salts Chemistry of Onium Salts Iodonium and Sulfonium Salts Other Onium Salts Recent Developments Direct Photochemical Deeomposition of Onium Salts General Mechanism of Deeomposition Role of Various Factors Other Onium Salts Direct Photoinitiation of the Polymerization Sensitized Deeomposition of Onium Salts Sensitization by Hydrocarbons Electron Transfer with Dyes Electron Transfer with Metal Salts Energy Transfer with Ketones Electron Transfer with Ketones Electron Transfer with Radicals 132

4 x Contents Cationic Photoinitiators as Sources or Quenchers of Radicals Photosensitized Initiation of the Cationic Polymerization Reaction Organometallic Derivatives 138 References Photoinitiated Polymerization Reactions Components of a Typical Photopolymerizable Film Monomers and Oligomers for Polymerization Reactions Radical Monomers and Oligomers: Mono- and Multifunctional Acrylates Unsaturated Polyester Resins Thiol-ene Systems Cationic Monomers Particular Photopolymerizable Systems Expanding Monomers Liquid Crystalline Monomers Miscellaneous Monomers and Methods of Polymerization Anionic Photopolymerization Monitoring the Photopolymerization Reaction Spectroscopic Methods Other Methods Methods for Analyzing the Physical and Mechanical Properties Particular Features of a Radical Photopolymerization Reaction Effect of the Photoinitiating System Reactivity Concentration Improvement of Specific Properties Excited-State Behavior in Bulk Media OtherEffects Effect of Film Thickness Effect of the Light Source Polymerization Profile and Characteristics Role of the Monomer and the Oligomer Role of the Monomer in the Photopolymerization of Polyurethane Acrylates or Epoxy Acrylates Superficial Hardness Solubility Thermal Resistance Photochemical Stability Formation of Semi-interpenetrating Networks Problem of Oxygen 199

5 Contents xi 5-5 Curing of Pigmented Systems Redshifted Absorbing Molecules Combination of Photoinitiators Basic Systems Involving Two Components Multicomponent Systems Photochemical Effects of the Pigment Synergistic Effects Kinetic Aspects of the Cationic Photopolymerization of Epoxides Characteristics of the Laser-Induced Polymerization Reaction Matching of the Photoinitiating System Absorption Kinetics Reactivity of Laser-Sensitive Initiating Systems Photostabilization of Cured Coatings Mechanism of Photooxidation of UV-Cured Polymer Networks Photoaging Tests Photostabilizers and Photostabilization Mechanisms Mechanisms Performance of Light Stabilizers Effect on the Photopolymerization Profile Photoinitiator Light Stabilizer Interaction in Film Matrix 235 References Some Practical Aspects in Photocuring Benefits of Light-Curable Coatings Equipment in Light-Curing Technologies Light Sources Conventional Light Sources Lasers OtherSources Example of UV Drying Equipment for the Curing of Coatings Chemistry in UV Curing Acylate-Based Formulations Chemistry vs. Cured-Film Properties Chemistry vs. Adhesion Epoxide-Based Formulations Water-Based UV-Curable Systems Acid Curing of Thermosetting Coatings Thiol-ene Coatings Curing of Modified Silicone Monomers Principles of Hybrid and Dual Cure HybridCure Dual Cure 283

6 xii Contents Clear Coatings Pigmented Coatings Different Categories of Pigments Role of the Pigment Some luustrations of the Effects of Pigments Applications Inks, Coatings, Varnishes, Paints, and Adhesives Photopolymer Printing Plates Microelectronics Optics Dental and Medical Applications Laser-Induced Polymerization Imaging Science Three-Dimensional Modeling Composites Miscellaneous Safety and Market 330 References Latest Developments and Trends 350 References 360 Index 367