Study On Coating Of Micro-NTO By Spray Drying

The modern battlefield environment requires ammunition to ensure low vulnerability while improving the range and damage capability.3-nitro-1,2,4-triazol-5-one(NTO)is a high-energy insensitive energetic material.Its theoretical detonation speed is close to RDX,its impact and friction sensitivity are comparable to TATB,and it has high density and low production cost.However,the molecular structure of NTO makes it highly acidic and has poor external compatibility with many commonly used metal materials.And NTO are soluble in common solvents such as water,ethanol,acetone,etc.,and it is not convenient to use the water suspension process for coating.In this paper,on the basis of micron-sized NTO obtained by spray recrystallization process,seven kinds of binders(F₂₆₀₂,F₂₆₀₄,F₂₄₆₁,F₂₃₁₄,ACM,Estane,EVA)were selected to coat and modify micron-sized NTO by spray drying process.The influence of formulation system design and process factors on the performance of coated products was systematically studied.The main research contents are as follows:(1)The dispersion stability of the spray-dried precursor micron-sized NTO suspension was investigated by absorbance test.The optimal dispersion process parameters were as follows:ultrasonic dispersion was carried out at a power of 325 W the magnetic stirring rate was 450rpm,and the dispersion time was 20 min.(2)Based on the morphology,crystal form,coating effect and thermal decomposition performance of the particles,the suitable binder for coating NTO was screened.The selected 7binders all achieved good coating on NTO,and the coated products had good appearance.Compared with micron-sized NTO,the average activation energy of F₂₃₁₄-coated NTO particles is increased by 18.27 k J?mol^-1,and the critical temperature of thermal explosion is increased by5.8 K,which has the most significant improvement on the thermal stability of NTO.(3)Based on the morphology,coating effect and thermal decomposition performance of the coated products,the single factor method was used to optimize the process parameters of the spray drying process.The optimal process parameters are as follows:the solid content of the feed liquid is 2%,the mass fraction of the binder is 3.5%,the air flow rate is 414 L/h,the feed rate is 4.5 m L/min,and the inlet temperature is 80?.Compared with micron-sized NTO,the activation energy of F₂₃₁₄-coated NTO particles was increased by 40.22 k J·mol^-1 under this process condition,which indicate greatly improved thermal stability of NTO.