Preparation of new phosphorus-nitrogen composite flame retardant and its application in TPU
A phosphorus-nitrogen organic salt flame retardant(EP)was synthesized through a simple one-step reaction us-ing etdronic acid as a phosphorus source(EA)and antiphenylenediamine(PPD)as a nitrogen source.Its structure was characterized by 1H-NMR and FTIR spectroscopy.The flame-retardant TPU was prepared by mixing TPU with EP us-ing a melt blending method,and its thermal stability,flame retardant performance,and mechanical properties were inves-tigated.The results indicated that the addition of EP generated little effect on the thermal stability of TPU,and its flame retardancy was significantly improved.The flame-retardant TPU containing 3 wt.％EP(TPU-3％EP)obtained a lim-iting oxygen index of 28.40 vol.％and also achieved a UL 94 V-0 classification in the vertical burn experiment.The re-sidual carbon yield(CY)was more than twice that of pure TPU.Compared with pure TPU,the total heat release and peak heat release rate of TPU-3％EP were reduced by 22.12％and 61.85％,respectively,and its effective combustion heat was also reduced.EP can enhance the flame-retardant performance of TPU mainly by catalyzing the condensation phase to form charcoal and isolate thermal oxygen exchange.Moreover,the free radical quenching effectiveness in the gas phase also generates a certain flame-retardant effect.
phosphorus-nitrogen organic salt flame retardantthermoplastic polyurethaneflame retardancy
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