Preparation Of Low Viscosity Hydroxyl Prepolymer-Based Polyurethane And Its Application In Propellant

In order to study the application of low viscosity adhesive on propellant,to improve the process performance and optimize the mechanical properties of propellant.Synthesis and processability of low molecular weight polyurethane elastomers were studied.The synthesis of B-PBT based polyurethane elastomer was studied,The B-PBT based polyurethane elastomer with good comprehensive properties was used as a binder in the propellant.The main work is as follows:The low molecular weight HTPB polyurethane elastomer was synthesized by two-step method.When the mass fraction of catalyst DBTDL is 0.004%,the pot life is up to 5h,which meets the requirement of processability.When the curing parameter R is 1.1 and the hydroxyl value of chain extender DEG is 60%of the total hydroxyl content of the reaction system,the tensile strength reaches 7.48MPa and the elongation at break reaches 540%.The low molecular weight HTPB polyurethane elastomer ensures excellent mechanical properties,reduces the viscosity of the slurry,and has a certain guiding significance to improve the processability of the HTPB propellant.The B-PBT based polyurethane elastomer was prepared by one-step method.The reaction temperature was 60? and the curing condition was 60? for 6 days.When the DEG was chosen as the curing agent,the process performance and mechanical properties of the elastomer were better.The mechanical properties of B-PTR1.1D3 and B-PTR1.1D4 showed good mechanical properties,tensile strength of 6.58MPa,6.74MPa and elongation at break of 599%and 659%,respectively.The glass transition temperature of B-PBT based polyurethane elastomer was about-30? by DMA tests.The results of creep analysis and stress relaxation analysis show that the elastic deformation of B-PBT based polyurethane elastomer is better after the stress is removed because of its cross-linking structure.Thermal analysis shows that the thermal decomposition of B-PBT based polyurethane elastomers is divided into three stages,namely decomposition of-N3,decomposition of carbamate groups,decomposition of macromolecule main chain,the thermal stability of B-PTR1.1D4 Thermal stability is the best.The B-PBT based polyurethane formulation with good comprehensive properties was selected and applied in propellant.Preparation of B-PBT based propellants using PBT based propellants,and found the use of B-PBT to replace PBT as the processing performance of the propellant binder have certain improvement.Mechanical properties test showed that the low temperature mechanical properties of B-PBT based propellants were significantly improved compared with PBT based propellants,the tensile strength reached 4.29MPa,and the tensile strength at room temperature and high temperature decreased.In addition,the elongation at break of B-PBT based propellant at high temperature was significantly higher than that of PBT based propellant at high temperature.The energy characteristics of B-PBT based propellant were calculated by the minimum free energy method,the characteristic velocity was 1609.3616m/s,the specific impulse was 268.0998s,and the heat of explosion at constant pressure was 5649KJ/kg.