Study On Safety Characteristics And Ignition Growth Law Of PBT-based Insensitive Propellant

As one of the typical energetic materials,solid propellants often encounter different external stimuli during actual production,storage and transportation.Due to the complex composition and formulation system of solid propellants,there are many stimuli(such as impact,accidental ignition)that induce accidental deflagration.To evaluate the safety profile of solid propellants,this paper takes PBT-based insensitive composite propellant(the mass ratio of Al/AP/HMX/binder is 19:44:15:22)as the research object.The sensitive stimulus parameters that may be encountered in the whole life cycle are analyzed and studied.Focus on the impact safety of PBT-based insensitive composite propellants and the ignition response characteristics under different ignition pressure.The main conclusions are as follows:The response characteristics of PBT-based insensitive composite propellants to shock wave stimulation,thermal stimulation,mixed stimulation and other sensitive parameters were studied.The results show that: The detonator cannot directly detonate the PBT-based insensitive composite propellant;The critical initiation pressure of PBT-based insensitive composite propellants is between 4.53 GPa and 4.63 GPa;In the slow heating test,the PBTbased insensitive composite propellant was thermally decomposed at 136.8 ℃,and the response degree was combustion;87 s after the ignition of the external fire test,the PBT-based insensitive composite propellant was burned;In the detonation test,the response level of the PBT-based insensitive composite propellant was burning;The above results show that PBT-based insensitive composite propellants are not sensitive to shock wave stimulation,thermal stimulation and mixed stimulation parameters.The impact safety characteristics of PBT-based insensitive composite propellants were investigated.Under the penetrating impact of bullets and fragments,the internal reaction of PBT-based insensitive composite propellant relieves pressure from the penetrating point,so no explosive reaction occurs,and the response level is all combustion;In the Susan impact test,when the PBT-based insensitive composite propellant was impacted,it was wrapped by an aluminum shell,and the rear end steel applied a load,and deflagration occurred;In the brittleness test,when the impact speed of the sample is greater than 156 m/s,the sample hits the target plate and compresses the sample due to inertia,and ignition occurs,but does not expand into deflagration.Based on the ignition part of the brittleness test,the initial dynamic activity ratio was introduced to characterize the fragmentation degree of the sample at different impact speeds,which provided a basis for evaluating the safety characteristics of insensitive solid propellants under impact stimulation.The results show: Inside the high-pressure airtight container,through high-speed video,it was observed that the flame generated in the ignition powder propagated through the cracks all the way to the bottom of the propellant.As the initial ignition pressure increases,the flame propagation time decreases.In the ultra-high pressure airtight container,the increase of the initial ignition pressure accelerated the formation of the hot spot of the solid propellant,but the burning rate was low and no shock wave was formed.Therefore,the burning time of the PBT-based insensitive composite propellant decreases,and the maximum burning pressure increases first and then remains unchanged.The above results show that the combustion state of the PBT-based insensitive composite propellant does not change abruptly at different ignition pressures,and the transition from combustion to detonation is unlikely to occur under accidental ignition.