Brominated phenolic resin

Bradford, I. Synthesis and Characterization of a Novel Brominated Phenolic Resin for Glass Fiber-Reinforced Composites. M.S. Thesis, Tuskegee University, Aug 2002. 

The resin cure of butyl normally uses one of a series of active, brominated phenolic resins such as Schenectady s SP-1055. The resin cure of butyl can proceed at temperatures from ambient to very high depending on the specific resin chosen and on the concentration and type of cure activator. Features of the resin cure are high stability, heat resistance, and the capability to be compounded into light colored and white formulations. 

Figure 2. SEM view of wood fibers impregnated with brominated phenol-formaldehyde resin. The line trace indicates bromine concentration in the wood...

TG-MS is an ideal technique for identifying residual volatiles in polymers. The detection of residual volatiles (and of other impurities) can often yield clues as to manufacturing processes. In many cases, such as in the determination of highly volatile materials, of residual solvents or plasticisers, use of TG-MS is requested. Specifically, there are reports on the entrapment of curing volatiles in bismaleimide laminates [145] and elastomers [48], on the detection of a curing agent (dicumylperoxide) in EPDM rubbers and of bromine flame retardants in electronic waste [50], of plasticisers such as bambuterol hydrochloride [142] or TPP and diethylterephthalate in cellulose acetate [143], on solvent extraction and formaldehyde loss in phenolic resins [164], and on the evolution of toxic compounds from PVC and polyurethane foams [146]. 

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. 

Epoxy resin Poly-(diallyl-phthalate) ABS PC-ABS blend Brominated bisphenol A Dechlorane Plus Octabromodiphenyl oxide Brominated phenol, triphenyl phosphate 0.5 mg sample at 950°C DB-5 fused silica capillary, 30 m x 0.25 mm i.d., 1.0-pm film 40°C for 4 min, ramp at 10°C/min to 320°C, hold for 18 min MS (El, 15-650 mass range) Injector T = 300°C detector T = 300°C 30/1 injection spUt [49]a,e... 

Hirohata, T. Misaki, T. Yoshii, M. Bromine, chlorine and boron modified phenolic resins with excellent flame retardance and thermal stability. Zairyo (English translation) 1987, 36 (401), 184-188. 

Incorporation of the above m-brominated phenolics into epoxy resin was accomplished either by the thermally catalyzed phenolic hydroxyl - epoxy reaction or by the caustic catalyzed reaction (U). The reactions are depicted as follows ... 

Intrinsically non-flammable polymers are few, but phenolic resins have a good reputation both in Are and smoke performance, which has resulted in their becoming increasingly favoured for reinforced plastics structures, for example, underground transport, where such concerns are greatest. Polyether ether ketone (PEEK) is also a low fire and smoke polymer. Unsaturated polyesters, vinyl esters and epoxy resins bum readily, but modified versions are available with improved behaviour. For example, both bromine and chlorine are used extensively in the form of chlorendic (HET) acid, tetrachlorophthalic anhydride (TCPA) and tetrabromo-phthalic anhydride (TBPA) which can be reacted into the polyester in small quantities and can act as permanent (non-migrating) flame retardants. 

In both oases, the functionality of the phosphorus oxychloride compound is reduced by hydrolysis after esterification with the phenolic compound. The reaction of monophenyl phosphoric acid with 1,3,5,7-tetiaazatricyclo [3.3.3.P ]decane can produce linear or crosslinked products [179]. The phosphorylated phenolic resin synthesized as desoribed in Scheme 30 can be brominated at the ortho and para positions not blocked during polymerization. These phosphorylated j enohc resins have a bromine eontent of 43% [179], In analogy with the reactions described in Scheme 29,2,4,6-tribromophenol... 

Interpenetrating polymer network varnishes are composed of the phenolic resin, an epoxy resin, flame retardants, for example brominated epoxies or acrylates, and triphenylphosphate, polymerization initiators for radical polymerization of the acrylates and curing accelerators to catalyze the reaction between epor groups and phenolic groups. 

Flame retardants containing bromine are twice as effective as those containing chlorine. However the price is higher and the UV resistance is lower. The products containing bromine are of aliphatic, cycloaliphatic, aromatic and aromatic-aliphatic type. Tetra-bromobisphenol A (TBBA) is condensed as a flame retardant in PC and expanded polystyrene (EPS). In phenolic and unsaturated polyester (UP) resins di- and tri-brominated phenols and tetra-bromophthalic anhydride serve as reactive components in the resin backbone. 

Trihydric phenols have only played a minor role because of their high price. Bisphenol A [2,2 -Z /5(hydroxyphenyl)propane] is still being used to a small extent in phenolic resin production. However, there is renewed interest in some specialty phenols such as chlorinated and brominated types as a result of legislation regarding flame retardancy. 

It is generally accepted that degradation of epoxy resins starts by dehydration of secondary alcoholic groups followed by homolytic scission of the formed allylic bond [34, 35]. There have been various studies carried out for the brominated epoxy resin treatment. In the study of Balabanovich [33], brominated epoxy resin produces gases and oil as pyrolysis products at the temperature of about 100 °C. However, these pyrolysis volatiles are contaminated by brominated phenols, brominated alkanes, and HBr, which is a difficult point for pyrolysis of brominated epoxy resin. 

Based on analysis of products distribution [25], it was concluded that there were two kinds of decomposition action hydrolysis mainly at lower temperature and pyrolysis mainly at higher temperature. At low-temperature stage, the brominated epoxy resin was mainly decomposed into bisphenol A, brome-phenol, isopropyl phenol monomer, etc., while at high-temperature stage, the brominated epoxy resin was mainly decomposed into phenol, o-cresol, p-cresol, and other small molecule compormds without bromine. 

NMR is shown in Table 16. A phenolic resin composition patented by Hitachi, based on a brominated cresol novolak, meets UL V-1 fire resistance ratings. Another area where considerable development has taken place is in modifying phenolics with epoxy resins for use in items ranging from circuit boards to recreational equipment. 

Exceptional heat resistance and low compression set can be obtained by curing butyl rubbers with dimethylol phenol resins. The curing reaction is very slow even at high temperatures and when activated by halogens. Stannous chloride, and combinations of a halogenated polymer (such as neoprene, halobutyl or brominated resin) with zinc oxide, are the most commonly used halogen-bearing activators. The systems shown in Table 5 are typical. 

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