Study On The Evolution Characteristic Of Emulsion Explosive Matrix During The Aging Process

Emulsion explosive matrix(EEM)is the main component of emulsion explosive which is widely used in engineering blasting operations.As a kind of highly concentrated W/O emulsion,EEM is a thermodynamically unstable system.Therefore,as the storage time increases,EEM will gradually become unstable and degenerate,resulting in the decline of its performance.The phenomena occurring in the aging process of EEM can not be completely explained by the classical emulsion stability theory.At present,the shelf life of emulsion explosive products is mostly determined by experience,lacking of strong theoretical support.So it is very necessary to study the aging process of EEM.In this paper,the aging process of EEM is firstly studied from the classical emulsion stability mechanism,and the reasons for the instability of EEM are analyzed from the classical emulsion stability mechanism.The basic EEM formulation is used for sample preparation,which is helpful for the relevant mechanism studied in depth.The main research work of this paper is as follows.(1)Experimental study and regular analysis of the aging process of EEM.The instability process of latex matrix was accelerated by high and low temperature circulation method,and the phenomenon of latex matrix in the aging process was observed by multi-angle observation combined with macroscopic observation,optical microscopy,particle size analysis and thermal analysis.The results show that the crystallization of the supersaturated ammonium nitrate solution in the dispersed phase is the main cause of EEM instability.The formation of crystals within a single droplet is relatively independent,and the spatial location at which it occurs is random.The precipitated crystals grow between the droplets to form a crystallization cluster.Under the experimental conditions in this paper,the size of untransformed droplets does not change during the aging process.(2)Crystallization kinetics of latex matrix instability process.Based on the formation mode and process of ammonium nitrate crystallization in dispersed droplets,the aging equation of EEM was deduced.The results of experiments and literature data show that the aging equation is consistent with the change law of crystallization rate during the instability of EEM and emulsion explosive,so it provides a method to quantify the aging degree of EEM.The characteristic time represents the time required for the aging rate of a certain type EEM to reach the maximum in a certain external environment,which is convenient for intuitive and quantitative evaluation of the storage performance of EEM and its products.(3)Evolution of the EEM aging process.By the observed phenomenon in experiment,the aging model of EEM was established based on the percolation theory.The model was built on a grid,and the occupancy of lattice points represented whether the dispersed phase droplets were crystallized,so as to realize the evolution of emulsion matrix instability.As the degree of aging increases,when the critical condition is reached,the crystal clusters which are independent of each other will be connected.A crystal cluster that spans the entire system will appear.At this time,the overall demulsification occurs in the system,and the crystallization possibility of droplet reaches the maximum.By combining with the aging equation,a method is provided for calculating the overall demulsification time of EEM,which is of important reference significance for determining the storage life of EEM and its products.(4)The effect of storage diameter on EEM during the aging process.According to the renormalization theory,the crystallization clusters have fractal characteristics near the critical conditions.So the aging experiments of the EEM with different storage diameters are designed,and the observed phenomena are analyzed according to the aging model.The results show that for the same variety of EEM,the larger the storage diameter is,the shorter the time required for overall demulsification of the sample,and the shorter the time interval between overall demulsification and full failure of the sample is,which has certain reference significance for industrial design and parameter optimization of remote delivery.