Study On Preparation And Application Of Thermal Isolative And Thermostable Materials Based On Polyphosphazene Elastomer

Polyphosphazene has high performance such as thermostability, low temperature resistance, radiation resistance, flame retardance because of its unique structure. It has a broad application prospect, can be used as special rubber and elastomer, medical materials and optical materials. Linear polydichlorophosphazene is important intermediate for the preparation of various of polyphosphazene. The research status is studying the preparation methods and the substitution reaction mechanism of PDCP, and synthesizing polyphosphazene elastomer with high molecular weight, thermostability, low temperature resistance and high mechanical strength.According to the current situation, this paper aims to:(1)prepare PDCP which used for the synthesis of polyphosphazenes derivatives; (2) prepare mixed replaced polyphosphazene by substitution reaction of PDCP, characterize structure and properties, explore the influence of side groups structure on the properties of productions; (3)explore the mechanism of PDCP nucleophilic substitution reaction, and study the effect of reaction conditions; (4)prepare crosslinkable polyphosphazene elastomer, study the effect on the production morphology of crosslinking degree.The main contents and results of this research mainly contain:Using (PC15 and NH4C1) or HCCP as raw material, PDCP was synthesized through solution method. The PDCP synthesized by HCCP had the higher molecule weight and the higher yield, and be more friendly to the environment.Some kinds of replaced polyphosphazenes were prepared by the nucleophilic substitution reaction between PDCP and sodium alkoxide/sodium phenolate. Their molecular weight could be more than 105. The Tg of these kinds of polyphosphazenes was decided by the structure of substituent: substituent with small size and good flexibility might decrease Tg, and substituent with big size and bad flexibility might increase Tg. The thermal stability of these replaced polyphoshazene was affected by the interaction strength between various kinds of substituents, the stronger the interaction between side groups was, the higher the thermal stability was.For the first time, the concentration of nucleophilic reagent was real-time calibrated by chemical quantitative method, and the reaction mechanism of the nucleophilic substitution of PDCP was analyzed, conclusions were summarized as follows:nucleophilic substitution reaction of PDCP belonged to SN2 nucleophilic substitution type. Protic solvent was adverse to the nucleophilic substitution reaction of PDCP, and polar aprotic solvent was favorable to this reaction. The higher the polarity of aprotic solvent was, the faster the nucleophilic substitution of PDCP reacted.Some new kinds of self-crosslinked polyphosphazenes were obtained by the substitution reaction of PDCP with the main nucleophiles(n-butoxy-, trifluoroethoxy-, phenoxy-) and the nucleophiles with crosslinks(2-hydroxyethoxy-). Without crosslinking agent, these polyphosphazenes can be crosslinked by heat drying, and the productions were elastomer. The thermal properties and mechanical properties of these polymer, before and after crosslinking, was analyzed. The thermal properties of the polymer was excellent, and the mechanical properties was significantly improved. The morphology of the crosslinking production was studied by changing the ratio of the substituent with crosslinks.