Epoxy Resins
Authors: Pham Ha Q. , Marks Maurice J. 
Published: November 2005

Epoxy resins are reactive intermediates used to produce a versatile class of thermosetting polymers. They are characterized by the presence of a three‐membered cyclic ether group commonly referred to as an epoxy group, 1,2‐epoxide, or oxirane. The most widely used epoxy resins are diglycidyl ethers of bisphenol A derived from bisphenol A and epichlorohydrin. The outstanding performance characteristics of the thermosets derived from bisphenol A epoxies are largely conveyed by the bisphenol A moiety (toughness, rigidity, and elevated temperature performance), the ether linkages (chemical resistance), and the hydroxyl and epoxy groups (adhesive agents). In addition to bisphenol A, other starting materials such as aliphatic glycols and both phenol ando‐cresol novolacs are used to produce specialty resins. Epoxy resins may also include epoxide‐bearing compounds based on aromatic amine, triazine, and cycloaliphatic backbones.

A variety of reagents have been described for converting the liquid and solid epoxy resins to the cured state, which is necessary for the development of the ultimate end‐use properties. The curing agents or hardeners are categorized as either catalytic or coreactive. Catalytic curing agents initiate resin homopolymerization, either cationic or anionic, as a consequence of using a Lewis acid or base in the curing process. Coreactive curing agents are polyfunctional compounds typically possessing active hydrogens that are employed up to stoichiometric quantities with epoxy resins. The important classes of coreactive curing agents include multifunctional amines and their amide derivatives, polyphenols, polymeric thiols, polycarboxylic acids, anhydrides, phenol–formaldehyde novolacs and resoles, and amino–formaldehyde resins.

The largest single use of epoxy resins is in the protective coatings market where high corrosion resistance and adhesion to substrates are important. Epoxies have gained wide acceptance in protective coatings and in electrical and structural applications because of their exceptional combination of properties such as toughness, adhesion, chemical and thermal resistance, and good electrical properties.

The article contains sections titled:1.Introduction2.History3.Industry Overview4.Classes of Epoxy Resins and Manufacturing Processes5.Liquid Epoxy Resins (DGEBA)5.1.Caustic Coupling Process5.2.Phase‐Transfer Catalyst Process6.Solid Epoxy Resins Based on DGEBA6.1.SER Continuous Advancement Process6.2.Phenoxy Resins6.3.Epoxy‐Based Thermoplastics7.Halogenated Epoxy Resins7.1.Brominated Bisphenol A Based Epoxy Resins7.2.Fluorinated Epoxy Resins8.Multifunctional Epoxy Resins8.1.Epoxy Novolac Resins8.1.1.Bisphenol F Epoxy Resin8.1.2.Cresol Epoxy Novolacs8.1.3.Glycidyl Ethers of Hydrocarbon Epoxy Novolacs8.1.4.Bisphenol A Epoxy Novolacs8.2.Other Polynuclear Phenol Glycidyl Ether Derived Resins8.2.1.Glycidyl Ether of Tetrakis(4‐hydroxyphenyl)ethane8.2.2.Trisphenol Epoxy Novolacs8.3.Aromatic Glycidyl Amine Resins8.3.1.Triglycidyl Ether ofp‐Aminophenol8.3.2.Tetraglycidyl Methylenedianiline (MDA)9.Specialty Epoxy Resins9.1.Crystalline Epoxy Resins Development9.2.Weatherable Epoxy Resins9.2.1.Hydrogenated DGEBA9.2.2.Heterocyclic Glycidyl Imides and Amides9.2.3.Hydantoin‐Based Epoxy Resins9.3.Elastomer‐Modified Epoxies10.Monofunctional Glycidyl Ethers and Aliphatic Glycidyl Ethers11.Cycloaliphatic Epoxy Resins and Epoxidized Vegetable Oils12.Epoxy Esters and Derivatives12.1.Epoxy Esters12.2.Glycidyl Esters12.3.Epoxy Acrylates12.4.Epoxy Vinyl Esters12.5.Epoxy Phosphate Esters13.Characterization of Uncured Epoxies14.Curing of Epoxy Resins15.Coreactive Curing Agents15.1.Amine Functional Curing Agents15.1.1.Primary and Secondary Amines15.1.1.1.Aliphatic Amines15.1.1.1.1.Ketimines15.1.1.1.2.Mannich Base Adducts15.1.1.1.3.Polyetheramines15.1.1.2.Cycloaliphatic Amines15.1.1.3.Aromatic Amines15.1.1.4.Arylyl Amines15.1.2.Polyamides15.1.3.Amidoamines15.1.4.Dicyandiamide15.2.Carboxylic Functional Polyester and Anhydride Curing Agents15.2.1.Carboxylic Functional Polyesters15.2.2.Acid Anhydrides15.3.Phenolic‐Terminated Curing Agents15.4.Melamine‐, Urea‐, and Phenol‐Formaldehyde Resins15.5.Mercaptans (Polysulfides and Polymercaptans) Curing Agents15.6.Cyclic Amidines Curing Agents15.7.Isocyanate Curing Agents15.8.Cyanate Ester Curing Agents16.Catalytic Cure16.1.Lewis Bases16.2.Lewis Acids16.3.Photoinitiated Cationic Cure17.Formulation Development With Epoxy Resins17.1.Relationship Between Cured Epoxy Resin Structure and Properties17.2.Selection of Epoxy Resins17.3.Selection of Curing Agents17.4.Epoxy/Curing Agent Stoichiometric Ratios17.5.Catalysts17.6.Accelerators18.Epoxy Curing Process18.1.Characterization of Epoxy Curing and Cured Networks19.Formulation Modifiers19.1.Diluents19.2.Thixotropic Agents19.3.Fillers19.4.Epoxy Nanocomposites19.5.Toughening Agents and Flexiblizers20.Coatings Applications20.1.Coatings Application Technologies20.1.1.Low Solids Solventborne Coatings20.1.2.High Solids Solventborne Coatings20.1.3.Solvent‐Free Coatings (100 % Solids)20.1.4.Waterborne Coatings20.1.5.Powder Coatings20.1.6.Radiation‐Curable Coatings20.2.Epoxy Coatings Markets20.2.1.Marine and Industrial Maintenance Coatings20.2.2.Metal Container and Coil Coatings20.2.3.Automotive Coatings20.3.Inks and Resists21.Structural Applications21.1.Structural Composites21.1.1.Epoxy Composites21.1.2.Epoxy Vinyl Ester Composites21.1.3.Mineral‐Filled Composites21.2.Civil Engineering, Flooring, and Construction21.3.Electrical Laminates21.4.Other Electrical and Electronic Applications21.4.1.Casting, Potting, and Encapsulation21.4.2.Transfer Molding21.5.Adhesives21.6.Tooling22.Health and Safety Factors23.Acknowledgments