Preparation And Properties Of Halogen-free Flame Retardant Radiation Crosslinked Polyethylene Composite Based On Cyclotriphosphazene Derivatives

As the largest and most important synthetic resin in the world,polyethylene?PE?has a huge application field and market.Although it has good mechanical properties,chemical stability and processability,but the property of being easy to burn is the disadvantage of PE which limits its development.Therefore,the research on improving the flame retardant property of PE is of great significance,which is conducive to further expanding the application market of polyethylene materials.At present,the flame-retardant modification of polymer materials is mainly achieved by adding flame retardant to prepare flame-retardant polymer composites.Among them,halogen flame retardant has a large proportion in the field of flame retardant because of its good flame retardant effect.However,because the hydrogen halide gas which is released by halogen flame retardant in the combustion process causes great harm to human body and environment.Based on above situations,various kinds of halogen-free flame retardant are studied by global researchers to replace halogen-containing flame retardant at present.It is a way to reduce casualties in the fire and the impact on the environment.In this paper,a kind of halogen-free flame retardant containing cyano aryl ether phosphazene?HPCTP-CN?and a kind of halogen-free flame retardant containing propenyl aryl ether phosphazene?HPCTP-bis S-C₃H₅?are prepared by nucleophilic substitution reaction.Phosphonitrilic chloride trimer is choosed as the reaction material.A series of composite materials with different content of aryl ether phosphazene type halogen-free flame retardants are prepared by applying them into the formulation of the PE-based halogen-free flame retardant system.Then high energy electron beam is used to irradiate the composite under different doses to prepare the polyethylene halogen free flame retardant irradiation crosslinking composite with different content of aryl ether phosphazene type halogen-free flame retardant.Finally,the effect by the content of halogen-free flame retardant and dose on the mechanical properties,melting processing properties,thermal stability,flame retardancy and insulation property of the materials is studied.The results show that the introduction of halogen-free flame retardant will affect the mechanical properties of the composite.However,with the increasing of irradiation dose,the mechanical properties of the composite will be improved.In addition,the introduction of halogen-free flame retardant will enhance the flame-retardant performance of the composite.At the same time,with the increasing of irradiation dose,the carbon residue and flame-retardant performance of the composite will also be improved.Under the irradiation,the aryl ether phosphazene type halogen-free flame retardant will have better flame-retardant performance.In the third chapter,a halogen free flame retardant containing cyanoaryl ether phosphonitrile?HPCTP-CN?is prepared by nucleophilic substitution reaction.Phosphonitrilic chloride trimer is choosed as the raw material.It is introduced into the formulation of the PE-based halogen-free flame retardant system of irradiated crosslinked polyethylene.The effect of the presence of cyanide group on the mechanical properties and gel content of the composites is studied.At the same time,the effects of different content of cyanoaryl ether phosphazene type halogen-free flame retardant in the composite and different irradiation dose on the property of the composite are studied.Taking PE-CN-4 as an example,the limiting oxygen index of PE-CN-4 is33%,which is 87.5%higher than that of pure PE and 26.9%higher than that of PE-CN-4 without irradiation.In the fourth chapter,a halogen-free flame retardant containing aryl ether phosphonitrile?HPCTP-bis S-C₃H₅?is prepared by one-step nucleophilic substitution reaction with Phosphonitrilic chloride trimer as raw material.It is introduced into the PE-based halogen-free flame retardant system of irradiated crosslinked polyethylene.The effect of the presence of allyl group on the mechanical properties and gel content of the composites is studied.At the same time,the effects of different content of the halogen-free flame retardant containing allyl aryl ether and irradiation dose on the property of the composite are studied.Taking PE-C₃H₅-4 as an example,the limiting oxygen index of PE-C₃H₅-4 can reach 33.2%,which is 88.6%higher than that of pure PE and 29%higher than that of PE-C₃H₅-4 without irradiation.In conclusion,two kinds of aryl ether phosphazene type halogen-free flame retardants with different structures are prepared by nucleophilic substitution reaction.Phosphonitrilic chloride trimer is choosed as the raw material.In this paper,they are introduced into the PE-based halogen-free flame retardant system.A series of radiation crosslinked polyethylene halogen-free flame retardant composites with better mechanical properties and flame retardant properties are obtained via irradiation crosslinking.