Epoxy Brominated

Bottle waste, hydrolysis of, 564 Bottles PET, 21 recycled, 532 Branched polymers, 8 Branching, 13 Branching agents, 8 Branching sequence distributions, 446 Brill temperature, 142 Brominated epoxy reagents, 414 Bromination-lithiation, 354 BTDA. See 3,3, 4,4 -Benzophenone-tetracarboxylic dianhydride (BTDA)... 

However this solution is not always convenient and may prevent high productivity and/or the production of intricate forms which require high temperature processing. Fortunately, some fire retardants dramatically increase the flowability of fire retardant plastics melts. For example ABS, flame retarded with F-2016 or F-2016M (brominated epoxy) has much higher flowability, melt flow index (MFI), and spiral flow index, than virgin ABS (Fig. 1). 

Most circuit boards are FR-4 boards that meet standards for fire safety by the use of brominated epoxy resins in which the reactive flame-retardant tetrabromobisphenol A (TBBPA) forms part of the polymeric backbone of the resin. Alternative flame-retardant materials are used in only 3-5 per cent of the FR-4 boards, but additional alternative flame-retardant materials are also imder development. Little information exists concerning the potential environmental and human health impacts of the materials which are being developed as alternatives to those used today that are based on brominated epoxy resins. 

This rationale is evident also in other bromine-containing oligomers, for example those based on brominated epoxy resins (20) and on poly-pentabromobenzyl acrylates (21). 

Brominated diphenyl oxides, 77 461 Brominated epoxies, 70 383 Brominated epoxy ohgomers, 77 470 Brominated epoxy resin, 70 456 Brominated poly(isobutylene-co-p-methylstyrene), 4 438 blends with halobutyl, 4 453 copolymers, 4 446 vulcanization, 4 450 Brominated polystyrene(s), 77 470 474 20 65... 

New fire retardants not related to the chemistry of diphenyl ethers have been developed for more environmentally friendly applications.61-62 Among these newer compounds available for use in styrenic copolymers are a proprietary compound, brominated trimethylphenyl indan, brominated epoxy oligomers, and tris(tribromophenyl) cyanurate. 

Phenolic resins have a low flammability by themselves due to the high aromatic content which leads to a high char formation on thermal degradation. However, end-capped brominated epoxy resins are used when necessary. Decabromodiphenyl ether in combination with antimony oxide is also used. 

Additive flame-retardant compounds include brominated epoxy resins, chlorinated hydrocarbons, decabromodiphenyl ether, and pentabromodiphenyl ether. Where transparency is not important, antimony oxide can be used as a synergist to reduce the amount of halogen required. 

Two resins were used to do the first study on laminate construction. The first was a brominated epoxy vinyl ester resin with antimony pentoxide and the second was a brominated unsaturated polyester resin. They were both promoted to cure at room temperature with methyl ethyl ketone peroxide catalyst. The panels were then postcured at 250°F (121°C) for 8 h. Panels were prepared that varied in glass content from 25% to 70% and panel thickness varying from 0.05 in. to 0.25 in. and were tested at the same testing facility. A summary of the FSI test data for the first set of panels tested are shown in Figures 23.1 and 23.2. This graph in Figure 23.1 plots the FSI value versus the panel thickness. This data would indicate that the thickness of the test panel has no effect on the measured... 

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. 

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. 

Goobich, J., and Marom, G., Moisture Absorption by Tetraglycidyl 4,4/-Diaminodiphenyl Methane/4,4 Diamino-diphenyl Sulfone Epoxies Containing Brominated Epoxy Copolymers, Polymer Engineering and Science, vol. 22, 1982, p. 1052. 

EPON 1124-A-80 425-443 Acetone solution Conventional brominated epoxy for FR-4 applications Resolution... 

After treatment of shreddered printed circuit boards we received the following results The brominated epoxy resin has been oxidized to carbon dioxide, water and bromide. Glas fibers and residual metals are not changed through this process. The weight reduction was approx. 50 %. 

Brominated epoxy oligomers are available in a number of different forms, with variations in molecular weight and eqdcapping. In general, these are nonblooming soluble flame retardants with good UV stability. 

Figure 12.11 Py-GC/MS chromatogram of brominated epoxy resin at 450°C. Peaks labelled are 2-bromophenol and 2-bromo-4-isopropenylphenol, respectively...

Although some competitor resins (e.g., polyimides and cyanate esters) are replacing epoxy resins in some more demanding applications, in which the superior glass transition temperatures or lower dielectric permittivity/low dielectric loss are preferred, brominated epoxies are still widely used. 

Earlier in this chapter, it was indicated that the presence of halide ions (e.g., Cl and Br ) is undesirable because they tend to promote the corrosion of parts of the IC. Low-flammability requirements for these encapsulants are realized through the use of brominated epoxy resins in combination with antimony oxide (Sb203). For some time the brominated epoxies have been suspected as a possible source of Br ions. Since it is difficult to achieve low flammability for these encapsulants without the bromine-containing species, efforts have been made to arrive at bromine-containing flame retardants of greater hydrolytic stability so that the flame retardant does not inadvertently diminish the corrosion protection these encapsulants are expected to provide. 

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