Simulation And Experimental Study Of Substance Materials On Calendering Plasticization Of Energetic Materials

As important energy source in the military industry,energetic materials play an important role in national defense construction.It is of great significance to explore its processing and study the influence of process parameters on the performance of energetic materials.At present,grooved calender is mainly used to plasticize,dehydrate and granulate the modified double-base propellant in China.The processing technology is mainly determined based on experience,and safety problems such as explosion are prone to occur during the calendering process,and many processing test methods are limited.In this paper,the theoretical analysis of the modified double-base propellant calendering process was carried out firstly.The calculating of the amount of pile during the calendering process was determined by the critical point of effective rolling.Based on the real modified double-base propellant materials,the motion state,the shear-stretching situation of the material inside the pile at the calendering gap were simulated by POLYFLOW,and the effects of different gaps and different speed ratios on safe processing and material plasticization were studied in depth.Due to the particularity of the double-base propellant materials,it is impossible to use the real materials for experimental verification.Therefore,cellulose acetate(CA)-glyceryl acetate(GTA)system was selected as propellant substance.The reliability of the selected substance was proved by comparing the solubility parameter of the substance with the real double-base propellant.The swelling and dissolution experiment of the substance was carried out and the swelling kinetics was studied.Based on the propellant substance system,the calendering process of the material was studied by a customized groove calender;the customary groove calender were utilized to study the processing and plasticizing process of energetic materials.The effects of solid component addition contents,processing and equipment parameters on plasticization were investigated.The degree of material plasticization was characterized by scanning electron microscopy and thermal analysis.The main works are as follows:(1)Theoretical research of the modified double-base propellant during calendering process was studied,and analyzed flow velocity distribution and the force situation.The condition for determining the effective rolling of the material on the calendering rolls is that the contact angle must be smaller than the friction angle,and the amount of the pile is calculated in combination with the gap,the roll diameter and the effective working portion length of the roll.(2)POLYFLOW simulation results showed that the material inside the pile will produce upward velocity and large axial movement under the action of the pressing force.The material inside the pile is mainly subjected to stretching,and there is a vortex formed close to the roll surface.The material at the gap is mainly sheared.According to the maximum pressure value,the safety of the processing was evaluated,and the plasticizing effect of the material was evaluated according to the magnitude of the shear stress and the distribution of the mixing index.(3)The solubility parameter of the CA-GTA system is similar to that of the double-base propellant.The diffusion of GTA in CA satisfies Fickian's law of diffusion.The calendering experiment was carried out with CA-GTA propellant substance and the results showed that the phenomenon of wrapping roller is affected by temperature in the early stage of calendering and the speed ratio of rollers in the later stage.The dissolution and plasticization of CA by GTA is a physical process.With the increase of solid contents,the phenomenon of material loss in the early stage of calendering is serious,and the water repelling rate is increased,but the flow ability of the system deteriorates and the degree of plasticization decreases.(4)Through the range analysis of orthogonal experiment,the influence of different process and equipment conditions on the water repelling rate and the mechanical properties of the calendered specimens were investigated,and the optimum performance combination was obtained respectively.