Design And Preparation Of PEI Derivatives And Their Catalytic Performance For Thermal Decomposition Of AP

Ammonium perchlorate（AP）is an important part of solid propellant,and its thermal decomposition performance will directly affect the combustion performance of propellant.However,AP has the disadvantages of high decomposition temperature and insufficient decomposition.Adding a catalyst is an effective way to improve the thermal decomposition behavior of AP.The improvement of AP thermal decomposition performance is mainly reflected in reducing decomposition temperature and increasing decomposition heat.In this paper,based on the positive charge of polyethyleneimine（PEI）and a large number of amino groups in the intrinsic structure,while electrostatic self-assembly with the negatively charged AP,the metal catalyst is adsorbed on the surface of the AP,thereby enhancing the interface between the metal catalyst and the AP,weakening the agglomeration of the metal catalyst,and promoting the metal catalyst to play a better catalytic role.The main contents of this topic are as follows:（1）AP/metal catalyst and AP/PEI/metal catalyst samples were prepared by solvent volatilization method,and the thermal decomposition behavior of both samples was investigated by differential thermal analysis（DTA）and other thermal analysis instruments.The results showed that the addition of PEI could enhance the catalytic effect of the metal catalyst on the thermal decomposition of AP.Among them,the AP/PEI/Cu（Cl O₄）₂ sample with Cu（Cl O₄）₂ as the metal catalyst had the optimum catalytic performance at an additive content of 5 wt.%,resulting in a decrease in the low-temperature decomposition peak and the high-temperature decomposition peak of AP by 29.8 and 94.2℃,respectively,and an increase in the apparent exotherm of 512.91 J·g^-1.Scanning electron microscopy（SEM）,X-ray The results showed that the electrostatic interaction between PEI and AP and the adsorption of PEI on the metal catalyst were the important reasons for the enhanced catalytic performance of PEI on the metal catalyst.The results show that the electrostatic interaction between PEI and AP and the adsorption of PEI on metal catalysts are important reasons for the enhanced catalytic performance of PEI.Based on the test data and the available literature,a possible catalytic mechanism for the thermal decomposition of AP by PEI/Cu（Cl O₄）₂ was deduced.（2）To further enhance PEI’s adsorption capacity and adsorption strength on metal catalysts,the imidazole group with strong coordination ability with metal ions was selected to modify PEI molecules to prepare PEI-imidazole derivatives（PEI-ICA）.The structure of PEI-ICA was confirmed by the NMR test.The ICP-OES test confirmed that the introduction of imidazole groups can enhance the adsorption capacity and adsorption strength of PEI-ICA to metal catalysts.AP/PEI-ICA/metal catalyst samples were prepared by a solvent evaporation method,and their thermal decomposition behavior was studied by DTA and other thermal analysis instruments.The results showed that when Cu（Cl O4）2 was used as the metal catalyst,the AP/PEI-ICA/Cu（Cl O4）2 sample had the best catalytic performance when the additive content was 5 wt.%,which reduced the high-temperature decomposition peak of AP by 55.6°C and increased the apparent heat release by 598.71 J·g^-1.However,the low-temperature decomposition heat flow signal of AP/PEI-ICA/Cu（Cl O4）2 disappeared.To study the reason for the disappearance of low-temperature decomposition heat flow signals,AP/PEI-ICA/Cu（Cl O4）2 was studied by SEM,XPS,XRD,IR,ICP-OES,and Zeta potential tests.The results show that the electrostatic interaction between PEI-ICA and AP and the strong adsorption of PEI-ICA on metal catalysts are the reasons for improving the thermal decomposition behavior of AP.Based on the test data,combined with the analysis of the decomposition products of AP/PEI-ICA/Cu（Cl O4）2 by TG-DSC-MS,the possible catalytic mechanism of PEI-ICA/Cu（Cl O4）2 on the thermal decomposition of AP was deduced.（3）To reduce the energy loss of solid propellants caused by the introduction of non-energetic catalysts,tetrazole groups with energetic properties were selected to modify PEI molecules to prepare PEI-tetrazole derivatives（PEI-TAA）.The structure of PEI-TAA was confirmed by the NMR test.AP/PEI-TAA/metal catalyst samples were prepared by the freeze-drying method,and their thermal decomposition behavior was studied by DTA and other thermal analysis instruments.The results showed that when Cu Cl₂ was used as the metal catalyst,the AP/PEI-TAA/Cu Cl₂ sample had the best catalytic performance when the additive content was 3 wt.%,which reduced the high-temperature decomposition peak of AP by 94.5°C and increased the apparent heat release by 738.81 J·g^-1.At the same time,the low-temperature decomposition heat flow signal of AP/PEI-TAA/Cu Cl₂ disappeared.To study the reason for the disappearance of low-temperature decomposition heat flow signal,AP/PEI-TAA/Cu Cl₂ was studied by SEM,XPS,XRD,IR,Zeta potential,and TG-DSC-MS.The results show that the electrostatic interaction between PEI-TAA and AP and the adsorption of PEI-TAA on metal catalysts are the reasons for improving the thermal decomposition behavior of AP.Based on the test data,combined with the analysis of the decomposition products of AP/PEI-TAA/Cu Cl₂ by TG-DSC-MS,the possible catalytic mechanism of PEI-TAA/Cu Cl₂ on the thermal decomposition of AP was deduced.