| Composite propellants were the most widely used propellants and were widely used in rockets and missiles.The internal defects of composite propellant(hereinafter referred to as propellant)would cause the sharp change of propellant combustion surface,and then affected the equipment performance.The self-healing material could self-repair damage and reduce internal defects,which played an important role in improving the propellant quality and equipment performance.However,the application research of the self-healing materials on propellants was almost blank at present,and most of self-healing materials can not have both medium-low temperature(which presented the safe temperature of propellants,below 80 ℃)self-healing ability and high strength mechanical properties resulting in they can not meet the requirements of propellants for safety and structural stability.Therefore,it was particularly important to prepare a high-strength medium-low temperature self-healing material and apply it to propellant.This paper constructed medium-low temperature self-healing materials with high strength mechanical properties based on the reversible action of aromatic disulfide bonds and hydrogen bonds,and carried out research on their application performance in propellants.The main research contents and conclusions of this paper were summarized as follows:A self-healing material based on aromatic disulfide bond was designed and prepared.A hydroxy-terminated polybutadiene(HTPB)based adhesive which can repair itself at 80 ℃ was obtained by introducing aromatic disulfide bond.The effect of the content of disulfide bond hard segment on the mechanical properties and self-healing properties of the material was studied.The results showed that the self-healing efficiency and mechanical properties of the material increase with the increment of the content of disulfide bond hard segment,when the content of disulfide bond hard segment was less than 50%.When the content of disulfide bond hard segment is higher than 50%,the self-healing efficiency would be reduced due to the increment of hard segment binding energy.When the content of disulfide bond hard segment was 50%,the self-healing efficiency of the material obtained was the best.In addition,compared with the control sample without disulfide bond,the important role of disulfide bond in improving the self-healing performance of the material was confirmed.A self-healing material based on hydrogen bonding supramolecular interaction was designed and prepared.In order to avoid the formation of cross-linked structure,linear polypropylene glycol was selected as the soft segment.Polyurethane materials with biphenyl ring,long chain and asymmetric aliphatic ring hard segment structures were prepared with diphenylmethane diisocyanate(MDI),hexamethylene diisocyanate(HDI)and isophorone diisocyanate(IPDI),respectively.The effect of hard segment structure on mechanical properties and self-healing properties of the materials was investigated.The results showed that the biphenyl ring structure with high binding energy would enhance the hard segment interaction,which was beneficial to enhance the mechanical properties of the material,and was not conducive to the self-healing behavior.The long chain structure will weaken the interaction of hard segments,which was beneficial to enhance the dynamic properties of molecular chain segments,but not conducive to the improvement of mechanical properties.The asymmetric aliphatic ring structure took into account the advantages of both.The maximum tensile strength of PPG-IP-PA synthesized by IPDI can reach 3.85 MPa,the elongation at break was close to 3000%,and the mechanical properties can be fully recovered after 12 hours at room temperature,with excellent comprehensive properties.A self-healing material based on the interaction of heterogeneous hydrogen bond and aromatic disulfide bond was designed and prepared.In order to further improve the mechanical properties of the polymer,poly(tetrahydrofuran)was selected as the soft segment,and the composition of strong and weak hard segments was regulated by changing the proportion of MDI and IPDI to form heterogeneous hydrogen bonds.The influence of heterogeneous hydrogen bonds on the properties of the materials was studied.The results showed that with the increase of MDI ratio,the proportion of hard segment increased,the heterophase hydrogen bonding was enhanced,and the mechanical properties were greatly improved.However,the increment of hard segment structure would lead to the deterioration of polymer chain segment dynamics,which would negatively affect the self-healing performance.When the MDI ratio was 40%,the comprehensive properties of the obtained sample PU-C were the best,with 8.0MPa tensile strength and 930% elongation at break,and the mechanical properties could be fully restored after 5 h of self-heal at 60 ℃.The application properties of self-healing materials in propellants were studied.PSP-130 PA,which had the best mechanical and self-healing properties,was selected as the adhesive to prepare the self-healing propellant sample,and the self-healing and combustion properties of the self-healing propellant were studied.The results showed that the self-healing propellant is not effective in repairing large scale damage.The damaged propellant can only recover 30%tensile strength after 12 h self-heal at 60 ℃.However,the self-healing propellant can effectively repair the damage in a small area,and the yield strength of the damaged propellant can be restored to more than 95% of the original strength.In addition,compared with the traditional HTPB adhesive,the introduction of PSP-130 PA not only improved the interface peeling strength by 140%,but also enabled the interface to be repaired several times.Among them,the initial repair efficiency of debonding interface peeling strength reached 87%,and the secondary repair efficiency still reached 64%.Like traditional HTPB-based propellants,SHP also had good combustion performance. |
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