Synthesis Of Novel Organophosphorus Flame Retardants And Research To Flame Retarded Polycarbonate

In order to reduce halogen flame retardant harm to human health and environment, although halogenated compounds show good flame retardancy and have been used widely for several decades, their use has been curtailed in many countries because of toxic and corrosive fumes released during combustion. Environmental concerns about halogenated flame retardants are the driving forces behind the development of cost effective, halogen-Free alternatives. Organo-phosphorus flame retardant, as an alternative, possess the properties of "enveriment-Friendly" and high efficient. It could impart good flame retardancy to the resin and has the advantages of low smoke and low toxicity. In recent years, the organic-phosphorus flame retardants have become a hot topic of the flame retardants developed neighborhood. Polycarbonate is a very important polymer material, have outstanding properties, such as good mechanical properties and chemical stability etc. Therefore, they are widely used in the fields of construction, automobiles, electronic and electric devices, etc. But the polymers are easily flammable and subjected to various mandatory controls.Synthesis of novel phosphate flame retardant and their intumescent flame retardant Polycarbonate has become the world’s research focus of flame retardant Polycarbonate.In this work, novel flame retardants additives,[poly(diethylene-N-N’-phosphoramidate),(PDEP)] and bis(2,6-dimethylphenyl) phenyl phosphonate (BDMPP) were designed and synthesized on basis of the materals of phenylphosphonicdichloride (DCPPO)、piperazine and2,6-dimethylphenol. And the structure of PDEP and BDMPP compounds were characterized by FTIR,’H-NMR,31P-NMR and TGA,and the effect of reaction parameters on the yield were studied.The thermogravimetric analysis (TGA) results demonstrate that PDEP and BDMPP showed good char-forming ability. Its initial decomposition temperature was219℃,281℃based on5%mass loss, and its char residues was18.1、33.3%at600℃, and10.5、9.1%at800℃, respectively.PDEP and BDMPP were used to impart flame retardancy to PC by melt blending. Combustion behaviours of PC/PDEP and PC/BDMPP systems were assayed by limiting oxygen index (LOI) and vertical burning test (UL94). The results indicated that the LOI values of PC/7wt.%PDEP and PC/7wt.%BDMPP were34.8,32.7%, and PC/7wt.%BDMPP also passed UL94V-0rating with3.2mm samples. Although PC/7wt.%PDEP failed to pass UL94V-0rating with3.2mm samples, but its LOI value increased to23.8%compared to pure PC, and its burning time decreased from23s to12s. So the organo-phosphorus compound could enhance the flame retardancy of PC. Thermogravimetric analysis results showed that in N2, the initial degradation temperature of PC/PDEP and PC/BDMPP systems decreased but the residual char yields increased. The analysis of scanning electron microscopy (SEM) and FTIR reflected that BDMPP occurred thermo-oxidative degradation and formed phosphoric and polyphosphoric acids at lower temperature. The acids promoted the char-forming, and then a protective layer formed to stop the propagation of heat and oxygen to melt polymer matrix during combustion. Therefore, it prevents the polymer from further burning. Results of mechanical properties test indicated that the effects of PDEP and BDMPP on the Izod impact strength of PC were negative.The tensile and flexural strength of PC also declined due to the addition of PDEP, but both of properties of PC increased due to the addition of BDMPP.