Synergistic action of Sb2O3 with bromine-containing flame retardant in polyolefins. 1—the variance in their performance versus Sb/Br ratio

The synergistic action of antimony (Sb) with bromine (Br) was studied for polypropylene-2,3-dibromopropylpentabromophenyl ether–Sb2O3 systems at various Sb/Br molar ratios. Oxygen index, weight loss rate and heating value were used to evaluate the retardant effect. Bromine and antimony emission and their material balances were measured by gravimetric and X-ray fluorometric analysis of heated samples at each reaction time. Retarded HBr formation in the gaseous phase through SbBr3, SbOBr and Sb4O5Br2 was proved by X-ray diffraction analysis of heated residues and model products. SbBr3 and HBr formation were greatest at Sb/Br ratios of 1/3 and 1/4, respectively, while the highest oxygen index and the lowest weight loss rate and heating value were obtained at 1/4. Consequently, HBr will most probably produce the retardant effect rather than SbBr3. Effective synergistic action at the Sb/Br ratio of 1/4 is explained by presuming the formation of an acidic HBr.SbBr3 complex in the molten phase for the particular reaction pattern of bromine in 2,3-dibromopropylpentabromophenyl either.