Synthesis Of Melamine Polyphosphate By Solid Phase Polycondensation And Its Application Research In EVA

Ethylene-vinyl acetate copolymer(EVA)is widely used in insulation film,commodity,cable sheath,seals,medical instruments,building materials,electrical accessories and so on.However,EVA belongs to combustible material.Its LOI is low(19%),with large heat release in combustion,and accompanied by melting dripping and a lot of smoke,which not only limits its application in some fields,but also poses a potential threat to people's lives,property and environment.Therefore,the study on the flame retardant properties of EVA material becomes very important.With the desperately demanding for green and environmentally benign flame retardants and relevant strict regulations,it is appealing and urgent to develop halogen-free additives for EVA.In this thesis,the solid-state synthetic method of melamine phosphate(MPP)and its application in EVA were studied.Firstly,MPP is synthesized by the solid-state polycondensation with melamine(MEL)and ammonium biphosphate(AP)as row material.Synthetics conditions of MPP were primarily studied,including the mole ratio of MEL to AL,the reaction temperature and reaction time.The molecular structure of the products were characterized by FTIR,XPS.Thermal stability were analyzed by thermal gravimetric analysis(TG).It is found that the optimum conditions for the synthesis of MPP are as follows:the reaction temperature is 325 ?,the reaction the time is 2 h and the mole ratio of MEL to AP is 1:2.The product obtained under this conditions showed highest content of flame retardant element(P)and better thermal stability,which started to decompose at 349 ?.Carbon residues of 48.4 wt%at 600 ? proved that the compounds have good carbonization behavior.Phosphoric acid can be obtained by the thermal degradation of P-O-P in MPP molecular,which can be used as acid source.The melamine group in MPP can act as gas source to be provided NH3 in its decomposition.It is necessary to find the carbon source in the intumescent flame retardant system.In this thesis,PER was used as the carbon source to be added to the EVA/MPP system,and the relationship between the loading ratios of PER and MPP on the flame retardance has been studied.The results show that MPP can improve the thermal stability of EVA through reducing the thermal decomposition rate of the material.The LOI vaules of EVA composites increased from 19.6%to 23.1%.Meanwhile,the cooperation of MPP and PER can endow EVA with better flame retardance.When the mass ratio of MPP to PER is 4:1,the flame retardant effect is the best.The LOI value is 24.2%and total heat release reduces from 107.1 MJ/m2 to 88.2 MJ/m2.In order to find out the better flame retardant formula and the corresponding synergistic flame retardant mechanism,the effect of different content of nano-SiO2 and Al2O3 on the flame retardance of EVA was investigated.The results show that the thermal stability of EVA can be improved by both nano-SiO2 and Al2O3,and the amounts of residual char are obviously improved.However,the flame retardancy of EVA is not improved with the increase of the content of nano-SiO2.It is found that when the content of nano-SiO2 was 4 wt%,the flame retardant system achieve the best flame retarding effect.The results indicate that flame retardants contribute to the formation of the high-quality carbon layer during combustion,which effectively improve the flame-retardant properties with the LOI value of 25.7%.While,the further increase of the content of nano-SiO2 did not enhance the flame retardant effect,because the high loading of filler can affect the properties of the char layer such as intumesence and continuity.Al2O3 can also play a synergistic effect in the intumescent flame retardant EVA composites.When 6 wt%Al2O3 was added into EVA,the LOI vaules can increase to 26.5%,with the greatly improved amounts of char at high temperature.However,the compactness of the residual char layer is not good,which could not play a role in efficient isolation of oxygen and heat.So it is not good as SiO2 in the cone calorimeter test.