Preparation of NC-BA-RDX coating ball particles by means of layer-to-layer assembly technique

Taking RDX as core material, NC as outside layer and LBA-201 bonding agent as middle layer, the NC-BA-RDX coating ball particles were prepared by layer-to-layer assembly technique. The effects of the vacuum degree and stirring speed on the shape, cubic density and size of the spheric particles were investigated by experiments. The coating ball particles were observed and analyzed by means of SEM, TEM and DSC, and the mechanical properties of the propellant were measured. The results show that the samples prepared by the technique present spherical shape with uniform particle sizes, dense structure and excellent fluidity. The better coating ball particles can be obtained by slowly increasing vacuum degree and temperature during the process of taking out solvent, and the optimum time of taking out solvent is 20-25 min. When stirring speed increases from 700 r/min to 2000 r/min, the medium diameter (d₅₀) of ball particles decreases from 386.7 μm to 18.4 μm, and the SPAN value decreases from 0.334 to 0.107. The suitable stirring speed is 1500-1800 r/min. The intensity of melt endotherm peak obviously weakens and the peak temperature decreases by 1.7°C. Meanwhile, thermal decomposition peak temperature increases by 4°C, and the exothermic enthalpy reduces by 142 J/g. The elongation of CMDB propellant with NC-BA-RDX increases by 111.9% at low temperature (-40°C) and 51.3% at high temperature (50°C). The maximum tensile strength increases by 0.62 MPa at high temperature and 3.24 MPa at low temperature.