| Hydroxyl Terminated Poly-Butadiene(HTPB),which has polyhydroxy functional groups,can be cured by isocyanate-based curing agent,and thereby gives a certain shape and mechanical properties to the energetic materials.It is the most commonly used binder of energetic materials such as composite solid propellant,PBX explosive,gas generating agent and many more.HTPB binders.However,when a binder for the energetic material is affected by heat,mechanical and chemical factors,the defects of the microcracks may be generated inside the energetic material,which can have a significant effect on the mechanical properties and application reliability of the energetic materials.If the HTPB binder system is self-repairing,it could be expected to significantly improve the application reliability of the damaged energetic materials and prolong the service life.It has a good application prospect to introduce self-repairing properties into energetic materials,so based on the Diels-Alder reaction and HTPB binders of solid propellants,two novel compounds--furfuryl-terminated polybutadiene(FTPB)and trifurfuryl propane(TFP)were designed and synthesized,and their structures were characterized.Two different self-repairing systems were designed and their mechanical properties,self-repairing properties,reaction kinetics and their applications in propellants were studied.FTPB and TFP were prepared by end-group modification of furfuryl for hydroxyl-terminated polybutadiene(HTPB)and trimethylolpropane(TMP),and the structures of the products were characterized by IR and NMR spectra,besides the property and the decomposition behavior were studied.Two kinds of self-repairing binder systems were designed based on N,N’-(1,3-phenylene)bismaleimide(PDMI)and tolylene diisocyanate(TDI): TFP chain-extending FTPB-PDMI self-repairing system,HTPB-TDI and FTPB-PDMI self-repairing system.Tensile test,scanning electron microscopy and hot-stage polarization microscope were used to study the mechanical properties and self-repairing properties of the two self-repairing systems.The TFP chain-extending FTPB-PDMI self-repairing system has the best mechanical properties and self-repairing properties when the content of TFP is 10%.The mechanical properties and self-repairing properties of HTPB-TDI and FTPB-PDMI self-repairing system were related to the content FTPB-PDMI system.DMA was used to study the network structure of HTPB-TDI and FTPB-PDMI self-repairing system,which proved that the network had an interpenetrating network structure.The Diels-Alder reaction kinetics of FTPB-PDMI system was studied by FTIR,UV-Vis and DSC to determine the kinetic model and activation energy of the reaction system.The activation energy of the homopolymer and the mode of the main chain fracture were confirmed by the molecular simulation results.The two systems were applied as self-repairing binder systems to the three-component solid propellants with solid content of 80%.The morphology,mechanical properties and self-repairing properties of the two systems were studied.The propellant with self-repairing ability and a certain degree of mechanical strength was obtained to meet the application requirements. |
