Efficiency of brominated fire retardants in epoxy composites materials

Introduction. Composites based on epoxy oligomers are characterized by complex of beneficial operational properties. However, wide use of such composites in modern construction industry is limited by their relatively low fire safety. It is known that properties related to fire safety can effectively be controlled by brominated fire retardants. At the same time, quantitative dependencies between amount, chemical type of retardant and properties related to fire safety of epoxy polymers till now are not revealed in detail. Purpose of the work. The purpose of this work is to study the dependencies between combustibility, fume evolution of epoxy-based polymers and amount and chemical type of industrial additive and reactive brominated fire retardants. Materials and methods. Epoxy polymers were prepared on the base of ED-20 epoxy resin. Several additive and reactive flame retardants are used: hexabromobenzene, decabromo-diphenyloxide, 2,4,6-tri-bromanyline, 3,5,3,5-tetrabromo-4,4-diamino-diphenylsulfone, N(2,4,6-tribromophenyl)maleimide, 2,4,6-tribromophenol, tetrabromo-diphenylolpropane, pentabromophenol, pentabromophenol glycidyl ether, tetrabromo-phthalic anhydride, chlorohydrin pentabromophenol ether, microencapsulated chladone 114B2, CCl4, ammonium polyphosphate, decabromodiphenyloxide, reactive halogen-containing epoxy oligomers OXYLIN-6 and UP-631 and brominated epoxy oligomer ED-22. DuPont-9900 device is used for thermal analysis. Properties related to fire safety are determined in accordance with RU GOST 12.1.044-89 and several methods that were previously developed by authors of this work. Results. It is shown that there is only a weak dependence between chemical structure of the bro-minated fire retardants and combustibility of epoxy polymer. The primary factor that determines fire safety is the total amount of bromine. Another important factor that controls efficiency of brominated fire retardant is the proximity between temperatures of start of intensive decomposition for polymer and brominated com-pound. As gas phase fire retardants, brominated compounds inhibit the radical chains of flame processes and phlegmatize the flame by decomposition products. The flammability and combustibility of epoxy polymers decreases together with the increase in the content of additive brominated fire retardants: the oxygen index can be increased by about 50 %, the ignition temperature decreases by about 5 %. The effectiveness of microencapsulated fire retardants that allow to actively suppress the ignition source and to eliminate fire at the initial stage, significantly depends on the diameter of the microspheres and the chemical nature of the fire retardant used; in general, the effectiveness of microencapsulated fire retardants is slightly lower than the effectiveness of their active compound. The use of reactive compounds prevents the migration of the fire retardant; for such fire retardants, a linear dependence between oxygen index and bromine concentration was observed. Conclusion. In the present work we have summarized results of several laboratory tests that allow to reveal the influence of content and chemical nature of brominated fire retardants to the fire hazard indicators of epoxy polymers. A correlation was found between the oxygen index and the combustibility index. It is shown that to obtain low-combustible materials the oxygen index should exceed 31 %. It has been estab-lished that the chemical structure of additive aromatic brominated fire retardants has practically no effect on flammability. It was found that the optimal concentration of industrial brominated fire retardants is 8-10 % by weight.

бромсодержащий антипирен, горючесть, кислородный индекс, коэффициент дымообразования, термостойкость, brominated flame retardant, combustibility, limiting oxygen index, fume evolution index, thermal stability

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