Study Of Preparation And Its Structure And Properties Of Intrinsical Flame-retarded Polyphosphazene Elastomers

The inorganic backbone of polyphosphazenes has the characteratios of good flexibility,high thermal stability,and intrinsic flame retardancy,and different types of organic side groups can impart a wide range of properties to polyphosphazene materials.Therefore,the structural design of organic side groups of polyphosphazenes is expected to obtain intrinsically flame-retarded polyphosphazene elastomers.In this paper,a method for the controlled synthesis of linear polydichlorophosphazene with high relative molecular weight and low distribution coefficient was studied and its side groups were substituted.A series of intrinsically flame retardant aliphatic linear alkoxy/phenoxy substituted polyphosphazene elastomer was synthesized.The cross-linking of polyphosphazene elastomers was discussed and the following results were obtained:1.Synthesis of linear polydichlorophosphazene intermediate(PDCP).This research method realizes the controlled polymerization of high molecular weight and low distribution coefficient PDCP,with a number average molecular weight of more than 100,000 and a molecular weight distribution coefficient of between 1 and 1.5.2.A series of aliphatic linear alkoxy/phenoxy substituted polyphosphazenes were synthesized.The thermal analysis results show that the co-substituted products have higher thermal stability and higher combustion residual rate than their mono-substituted products,and the glass transition temperature of polymers increases with the increase of phenyl oxygen amount.When the molar ratio of n-butoxy and phenoxy in polyphosphazene was 1:3,the thermal stability is best.Its initial decomposition temperature,maximum thermal decomposition temperature and residual rate were 248.54 ?,646.68 ? and 55.37%,respectively.3.The effects of two crosslinked systems of isophorone diisocyanate(IPDI)/ethylene glycol and bisphenol A on the thermal stability,tensile mechanical properties and flame retardancy of phenoxy polyphosphazene elastomers were investigated.The effects of two substituents,n-butoxy and phenoxy,on the properties of cross-linked elastomers were investigated.The results show that the above two cross-linking systems basically have no effect on the properties of the phenoxy-substituted polyphosphazene elastomers;however,different side groups have a greater influence on the properties of the polyphosphazenes.The limiting oxygen index(LOI)of the crosslinked polyphosphazene was 25%,the UL-94 rating of the crosslinked elastomer PIEBP and PPIBP all reached V-0,and PLPP was V-1.