Characterization of Electrospinning Prepared Nitrocellulose (NC)-Ammonium Dinitramide (ADN)-Based Composite Fibers

Nanoscale composite energetic materials (CEMs) based on oxidizer and fuel have potential advantages in energy adjustment and regulation through oxygen balance (OB) change. The micro- and nanosized fibers based on nano nitrocellulose (NC)-ammonium dinitramide (ADN) were prepared by the electrospinning technique, and the morphology, thermal stability, combustion behaviors, and mechanical sensitivity of the fibers were characterized by means of scanning electron microscope (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), gas pressure measurement of thermostatic decomposition, laser ignition, and sensitivity tests. The results showed that the prepared fibers with fluffy 3D macrostructure were constructed by the overlap of micro/nanofibers with the energetic particles embedded in the NC matrix. The first exothermic peak temperature (T_p) of the samples containing ADN decreased by 10.1 °C at most compared to that of ADN, and the pressure rise time of all the samples containing ADN moved forward compared to that of the sample containing NC only. Furthermore, ADN can decrease the ignition delay time of NC-based fibers under atmosphere at room temperature from 33 ms to 9 ms and can enhance the burning intensity of NC-based fibers under normal pressure. In addition, compared to the single high explosive CL-20 or RDX, the mechanical sensitivities of the composite materials containing high explosive CL-20 or RDX were much decreased. The positive oxygen balance of ADN and the intensive interactions between ADN and NC can reduce the ignition delay time and promote the burning reaction intensity of NC-based composite fibers, while the mechanical sensitivities of composite fibers could be improved.

Cellulose nanosphere: Preparation and applications of the novel nanocellulose

Over the past few years, cellulose nanosphere (CNS) has gained growing attention and rapid development. As a new type of nanocellulose materials, CNS can be prepared from native cellulose by using methods which have been adopted extensively to prepare the well-known nanocelluloses, i.e., cellulose nanofiber and cellulose nanocrystal. The particular interest is that the regenerated cellulose and mercerized cellulose can also be used as important feedstocks to produce CNS. In this review, the preparation methods of CNS are described and discussed, via both top-down processes, including chemical, mechanical, and enzymolysis ones, and bottom-up processes by using various cellulose I and II starting materials. This review also highlights the researches relative to cellulose composite nanospheres, and summarizes the applications of spherical cellulose-based nanoparticles. Finally, the future challenges and opportunities of CNS are prospected in this work.

Nitration of Chitin Monomer: From Glucosamine to Energetic Compound

The nitration of chitin monomer in a mixture of nitric acid and acetic anhydride was conducted and a highly nitrated (3R,4R,6R)-3-acetamido-6-((nitrooxy)methyl)tetrahydro-2H-pyran-2,4,5-triyl trinitrate (1) was obtained. Its structure was fully characterized using infrared spectroscopy, NMR spectroscopy, elemental analysis, and X-ray diffraction. Compound 1 possesses good density (ρ: 1.721 g·cm⁻³) and has comparable detonation performance (V_d: 7717 m·s⁻¹; P: 25.6 GPa) to that of nitrocellulose (NC: V_d: 7456 m·s⁻¹; P: 23 GPa; I_sp = 239 s) and microcrystalline nitrocellulose (MCNC; V_d: 7683 m·s⁻¹; P: 25 GPa; I_sp = 250 s). However, Compound 1 has much lower impact sensitivity (IS: 15 J) than the regular nitrocellulose (NC; IS: 3.2 J) and MCNC (IS: 2.8 J). Compound 1 was calculated to exhibit a good specific impulse (I_sp: 240 s), which is comparable with NC (I_sp: 239 s) and MCNC (I_sp: 250 s). By replacing the nitrocellulose with Compound 1 in typical propellants JA2, M30, and M9, the specific impulse was improved by up to 4 s. These promising properties indicate that Compound 1 has a significant potential as an energetic component in solid propellants.

New insensitive high-energy dense biopolymers from giant reed cellulosic fibers: their synthesis, characterization, and non-isothermal decomposition kinetics

Renewable giant reed has been explored for the first time to develop new advanced high-energy dense biopolymers through carbamate surface functionalization and nitration of native cellulose and cellulose microcrystals.