Fabrication Of Nano And Micro Particulates CL-20/NC By Electrospinning And Electrospray Methods

In this work, electrospray technique was firstly applied to fabricate nano and micro-spherical CL-20 particles. The influence of different electrospray parameters have on the structures and morphologies of CL-20 were thoroughly studied.(1)In order to understand the releationship between the properties of solution, such as conductivity, viscosity, concentration, the CL-20 particle structures, actone, ethyl acetate and the mixture of them were chosen to be the solvent. Besides, the effect of process parameters, like voltage, solution rate, were also investigated as experimental parameters on nanoparticle structures. CL-20 nanoparticles from several hundred nanometers to several microns were finally fabricated through optimizing the experimental parameters. Results also implied that particles with small size could be easily obtained when the conductivity of solution was good, meanwhile the particles were solid and with smooth surface. Otherwise, large hollow spherical particles could be attained. XRD and DSC investigations proved only β-CL-20 could be fabricated by electrospray technique, and the thermostability and activation energy of CL-20 particles were also declined.Besides, nitrocellulose(NC) nanofibers were acquired by electrospinning technique in this work. The influence of experimental parameters, such as properties of precursor solution(solvent type and solution concentrations) and process parameters(voltage, solution flow rate, distance between needle and plate), on the size and distribution of fiber diameter were studied. Results show that concentrations of precursor solution played an crucial role on the fabrication of fiber in the range of 6wt%~24wt%. Only microparticle or beaded fiber could be made if the precursor concentrations was small than 18wt%. Uniform fibers would be received by the electrospun process if the concentration was larger than 18wt%. SEM results show that, NC fibers with the diameter at the ranging from 200 nm to 900 nm could be achieved by adjusting voltage, solution flow rate and distance between needle and plate, etc. DSC-TG analyses of different shapes of NC indicated that the activation energy of NC fibers was lower than bulk NC, while the peak temperature of thermal decomposition of NC fiber was higher than bulk NC.Finally, CL-20/NC composite fiber with different mass ratios(CL-20:NC=1/8~8/8) were fabricated by cosolvent electrospinning technique. SEM analyses showed that composite fibers were uniform in size of diameter with smooth surface. The diameter of composite fibers increased with CL-20 mass ration. FTIR indicated that no chemical reaction happened between the NC and CL-20 in the process of formation. Fast speed camera system and thermal infrared imager systerm were used to test the combustion properties of the composite fibers and pure NC fiber, and the results revealed that combustion speed and flame temperature of fiber were both increased with the addition of CL-20.