Synthesis And Properties Of Amimo-cyclophosphazene And Fluorinated Polyphosphazene

Polyphosphazene is a class of polymers with a main chain structure of alternating phosphorus and nitrogen atoms with two organic side groups attached to each phosphorus,and its physical and chemical properties can be altered by manipulating the structure of the substituted side groups at the phosphorus,so that it can be used in various application.Epoxy resin is a typical thermosetting plastic,which is widely used in various fields due to its excellent bond strength,insulation properties,excellent chemical resistance and mechanical properties.Also,the research on the flame retardant and mechanical properties of epoxy resins is a hot topic in today's flame retardant polymer science.Polyphosphazene epoxy curing agents have gained much attention due to their excellent flame retardant properties.Due to the diversity of polyphosphazene side groups,there is also a research space in the application of superhydrophobic nano-coatings of such materials.Fluorinated polyphosphazene has high contents of fluorine with a low surface energy,therefore,it holds good hydrophobic properties.In addition,the phosphazene backbone itself has excellent flame retardant properties.So,fluorophosphazene has a good application prospect in hydrophobic flame retardancy.In present piece of research work,different cyclotriphosphazene derivatives containing amino groups with aromatic rings were designed,and cyclotriphosphazenes substituted with o-phenylenediamine,aniline and catechol were successfully synthesized.The as-synthesized product with the best thermal stability,that is,TPDACP,evaluated by thermal properties,and further curing reaction with epoxy was carried out by TPDAC.The expected results at the initial structural design were verified by its flame retardancy tests,char forming mechanism and mechanical properties.Adding TPDAC to E-44/DDS epoxy gives a new epoxy thermoset system.Analysis of the char and gaseous products showed that the improved flame retardancy of the epoxy resin was caused by the effective synergistic flame retardant action occurring in the coacervate phase and the gas phase.Also,adding of TPDAC reduces the release of flammable gases.The decomposition of TPDACP promotes the formation of a polyphosphoramide carbon layer in the polymerization phase,while,at the same time,releasing less combustible gas in the gas phase to suppress flame generation.Due to its excellent high carbonization efficiency and versatility,TPDAC has excellent carbon residue and flame retardant effects,and its mechanical properties have also been greatly improved.The regulation of the fluorine contents is also achieved by adjusting the side group structure of the fluorophosphazene.The hydrophobic properties and other comprehensive properties,for example,thermal behavior and mechanical properties of different products were tested to select the optimal pendant structure.We also explored the effect of complex pairing hydrophobic properties with two different matrices of phenoxy polyphosphazene and silicone rubber.