The Aging Performance Of HTPB Solid Propellant

HTPB solid propellants are widely used in the military field,such as aerospace and weapons,because of its excellent mechanical and ballistic properties.The propellants prepared years ago have been aging seriously due to the long storage time.The number of spent solid propellant is increasing with time going,which cause considerable economic losses.It is a great significance to predict the storage life of HTPB propellants by carrying out the thermal accelerated aging experiment and aging performance research of propellant and establishing its aging mechanism and aging state.In this paper,through thermal accelerated aging experiment at 70°C,the aging laws,and the correlation of different microscopic properties were studied and analyzed.Finally,a highly correlated HTPB propellants aging model was established to estimate the storage life of the propellants.The aging performance research of HTPB propellants is destructive owing to it focuses on the mechanical properties,which requires a large number of samples.In order to achieve non-destructive or micro-destructive monitoring of the aging state of the propellant,it is necessary to introduce the small sample analysis method or the in-situ analysis method.In this paper,the volume resistivity,thermal decomposition Ozawa activation energy and Kissinger activation energy,the UV absorption intensity of chlorine dioxide(AP decomposition product),ignition and combustion speed,and the interface between the adhesive matrix and solid filler were studied systematically.And the variation trends of infrared spectrum characteristic peak intensity,gel content and crosslink density were also used to verify the results.The results showed that the aging mechanism of this batch of propellant is post curing reaction in the early stage,oxidation cross-linking and degradation chain breaking in the middle stage,and oxidation cross-linking in the later stage.With the aging of the sample,the volume resistivity of the standard propellant grain increased rapidly,the activation energy of thermal decomposition decreased linearly,the total amount of gas produced by AP decomposition,the grain and combustion rate of the grain,and the interfacial bonding performance of the propellant deteriorated.The correlation between gel content and cross-linking density was studied,and the aging model was established to determine the standard to evaluate the propellant.The results showed that the infrared characteristic peak intensity of AP and C=C double bonds,the content of enriched gas,and the volume resistivity at 100 V were highly correlated with the change of gel content.While the thermal decomposition activation energy and the hydrophobic angle on the surface of the grain are related to the cross-linking density.The exponential aging model of infrared spectrum characteristic peak intensity,enriched gas content,volume resistivity and interface performance was set up,and the linear aging model of thermal decomposition activation energy,gel content and cross-linking density was also established.It can be seen that the gel content increased by 45% as the critical value of propellant failure,corresponding to natural storage for 21 years in conventional environment.Though studying the impregnation ability of solution to propellant grain in the pretreatment of spent solid propellants,it can be found that the hydrophobic angle can be reduced to the target value by using a small amount of surfactant.Furthermore,the simulation of the actual cutting process revealed that the polyoxyethylene ether compound could improve the impregnation ability(the impregnation efficiency was58.49%),slow down the adhesion phenomenon and improve the cutting efficiency.