Structure Design And Performance Control Of Huisgen Reaction-cured Network Structure Material System

The polymeric binder acts as an elastomeric matrix for the solid propellant and is a key component in determining the mechanical properties of the solid propellant.Most thermoset binder systems are cured with isocyanate.However,due to the sensitivity of the isocyanate to humidity,it is easy to form a defective network structure,which adversely affects the mechanical properties of the propellant.Moreover,in high-energy nitrate plasticizer propellant systems,isocyanates may also lead to the formation of unnecessary nitroso derivatives,which is not conducive to the preservation of solid propellants.The development of thermosetting binder systems that are highly mechanical and insensitive to ambient humidity and compatible with high energy particulate components have become a technical requirement for the development of solid propellants.As a typical click chemistry reaction,the Huisgen cycloaddition reaction of azido and alkynyl groups is highly valued by researchers in the field of composite materials.The process of the triazole ring prepared by the Huaisgen cycloaddition reaction of the alkynyl group and the azide group has the advantages of being insensitive to water,high reaction efficiency,mild conditions,and no other by-products,and can construct a new triazole curing system.It is worth noting that for the trend of high energy and greening of pushers,the azeotropic polyether-based adhesives that have attracted much attention can not only have good compatibility with high-energy nitrate plasticizers,but also have rich azide group that is perfectly adapted to the triazole curing system.In this paper,based on the design of the number of functional groups of alkynyl compounds,particle curing synergists and polyurethane-like structures,Investigate the key factors and design criteria that determine the high mechanical properties of the triazole curing system,and expect to obtain high performance and control methods for the binder matrix.Firstly,a kind of glycidyl azide polymer(GAP)-based composite has been fabricated using propargyl-terminated ethylene oxide-tetrahydrofuran copolymer(PPET)with two(p-)and three(t-)alkyne functionaloties via Huisgen reaction.Independent upon the PPET functionality,both crosslink density and mechanical properties for two GAP/PPET systems showed a positive-interrelation changes of initial increase and subsequent decrease with an increase of azide/alkyne molar ratios.At equivalent of azide/alkyne molar ratios,the composites containing t-PPET with higher alkyne functionality exhibited better mechanical properties while those with two alkyne functionality presented lower glass transition.Under the regulation of alkyne functionality and azide/alkyne molar ratio as three functionality and 3:1 respectively,the tensile strength,Young's modulus and breaking elongation could simultaneously reach the maximum values of 1.38 MPa,4.07 MPa and 122.5%,which was ascribed to optimal participation of azide/alkyne reaction into network construction.Multi-walled carbon nanotubes(MWCNTs)are also commonly used for nanomodified reinforced nanoparticles.At the same time,it has been proved that MWCNT can promote combustion decomposition by adding it to solid propellant.In view of the shortcomings of poor dispersion of the original MWCNT in the organic matrix,the alkyne-based MWCNT was designed as a particle curing synergist to be added to the alkyne-terminated polytetrahydrofuran(PTMO)/GAP network.A triazole ring is formed between the MWCNT and the GAP,which promotes the dispersion of the MWCNT in the matrix,constructs a mode of a co-continuous structure,and improves network performance.The test results show that when the addition chain of alkynylated MWCNT is 1.0wt%,the mechanical properties of the nanocomposites are simultaneously enhanced and toughened.At this time,the tensile strength reached 2.03 MPa,and the Young's modulus and the elongation at break increased by 107.70% and 23.56%,respectively,compared with the blank sample.In view of the excellent mechanical properties of the thermosetting binder isocyanate curing system and the verification of the propellant application.It is desirable to design a binder system based on a urethane structure of a triazole curing system,and it is desired to obtain a high elongation and high modulus adjustment technique.Alkyl-terminated copolyethers having a urethane structure were obtained using TDI and propargyl alcohol,and then a cure network was constructed with a terminal azide-capped novel polyether(ATPET).The mechanical tests show that the network constructed by ATPET/PrPET has the best mechanical properties,tensile strength 2.05 MPa,modulus 1.88 MPa and elongation at break 221.440% when the reaction functionality is 1.0.