Brominated DGEBA Epoxy Resins

Brominated epoxy resins are the reaction product of epichlorohydrin and brominated bisphenol A. They are primarily used in applications where ignition resistance is a requirement, such as printed-circuit boards and other products that need to be flame-retardant. Tetrabromobisphenol A is the largest flame retardant in terms of commercial use at present. It is used in an estimated 95 percent of all flame-retardant printed wiring boards and is used in many flame-retardant surface-mounted adhesives.2 It is manufactured by several producers and is priced as a commodity product. 

The synthesis of brominated epoxy resins was discussed in Chap. 2. The resulting resins are available primarily as semisolids or solids in solvent solutions. They have properties similar to those of other DGEBA epoxies except that the high bromine content (18 to 21 percent) in the finished resins provides outstanding flame ignition resistance. Tetrabromo diphenylolpropane (Fig. 4.2) is an example of a commercially brominated epoxy resin. 

Standard epoxy resins are usually blended with brominated epoxy resins to provide the concentration of bromine required to provide ignition temperature resistance. Brominated resins have also been used as flame-retardant additives in thermoplastic compounds. 

FIGURE 4.2 Chemical structure of epoxy resin based on tetrabromo diphenylolpropane. 

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Brominated Epoxy Resins. The conventional DGEBA epoxy resins are flammable when cured. In an adhesive, flammability is generally not considered critically important because the mass of adhesive in any one area is relatively small. However, in certain applications (printed-circuit manufacture, aircraft interiors, furniture, etc.) nonflammability is an important criterion. Flame-retardant additives and chlorinated curing agents have been used to impart nonflammability to epoxy resins. 

Diglycidyl ether of bisphenol A (DGEBA) [CAS 1675-54-3] Brominated bisphenol A based epoxy resins... 

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