Synthesis Of An Amide Phosphonate Flame Retardant Additive And Its Basic Application Research In Polymeric Materials

Polymeric materials are widely used in various fields due to their excellent physical and chemical properties.However,the inherent flammability limit their application fields.Consequently,the improvement of flame retardancy is required.With the development of miniaturization,ultra-thinness and integration of electronic appliances,the flame retardant materials with high performance as well as excellent flame-retardant properties and comprehensive properties are required.Therefore,it is necessary to design and prepare the flame retardant additives with superior flame retardancy and compatibility for the polymeric materials.In this thesis,the intermediate dimethyl hydroxymethyl phosphonite was synthesized from dimethyl phosphite and paraformaldehyde,and then it reacted with toluene-2,4-diisocyanate and the phosphonate flame retardant toluene-2,4-dicarbamate methylphosphonate dimethyl with the similar segment structure of thermoplastic polyurethane(TPU).The obtained flame retardant defined as UPE was incorporated into TPU for improving its flame retardancy.The melting point of UPE was about 85?.The results of thermogravimetric analysis(TGA)indicated that the initial thermal decomposition temperature of UPE was 210.6? and the char residue was 21.4%at 800?.It is well known that the phosphorus-containing flame retardants exhibited excellent catalytic charring effects for oxygen-containing polymers.In this thesis,UPE was introduced into TPU matrix by melt blending.The results demonstrated that the TPU composites passed UL-94 V-0 rating without dripping during vertical burning test,and the limiting oxygen index(LOI)value was increased from 21.5%for pure TPU to 28.8%when 10 wt%UPE was added.The compactand sealed char layer was formed on materials surface during combustion,which exerted the barrier effect for the transfer of oxygen and heat.UPE firstly decomposed and generated phosphoric acid on heating and then stimulated the TPU matrix charring.Compared with pure TPU,the initial decomposition temperature of TPU/10 wt%UPE was earlier and the char residue increased from 7.5%to 18.4%at 800?.The cone calorimetry test showed that the parameters including the heat release rate,total heat release rate,smoke release rate and total smoke production of TPU/10 wt%UPE composites were significantly decreased compared with neat TPU.The flame retardant appeared good compatibility with the TPU matrix revealed by the results of scanning electron microscopy tests.The tensile strength and elongation at break of TPU/10 wt%UPE were 22.2 MPa and 1914.6%respectively,and it decreased by 7.9%and 5.8%compared with pure TPU.UPE produced PO free radicals during pyrolysis process and inhibited the combustion intensity of TPU composite in vapor phase.Meanwhile,the formed compacted char played good insolation effect in condensend phase.As a result,the flame retardant performance of TPU/UPE was effectively enhanced.UPE was also introduced into epoxy resin(EP)matrix.When 9 wt%UPE was incorparated,the EP thermosets passed UL-94 V-0 rating with the LOI value of 28.5%.The introduction of UPE promoted the degradation and charring of EP on heating,and the residual char of EP/9 wt%UPE was enhanced from 2.7%to 23.8%at 800?.The release of heat and smoke of EP/9 wt%UPE were reduced effectively compared with that of pure EP.The EP/UPE thermosets remained excellent mechanical perforamance due to the good compatibility between UPE and EP matrix.UPE exerted flame retardant effect in vapor and condensed phase simultaneously,and the EP/UPE thermosets were endowed excellent flame retardant properties.