Theoretical investigation of the structures and properties of CL-20/DNB cocrystal and associated PBXs by molecular dynamics simulation

Structural evolution of CL-20/DNB cocrystals at high temperature: Phase transition and kinetics of thermal decomposition

As a typical new energetic material, CL-20/DNB cocrystals have been recognized as a promising explosive owing to their excellent comprehensive performance. The thermal decomposition behavior, structural evolution and dynamic process of CL-20/DNB cocrystals under high temperature were studied by means of thermogravimetric differential heating, X-ray diffraction, Raman spectroscopy to gain insight into the cocrystal materials. The study found that the decomposition of CL-20/DNB cocrystal is a heterogeneous process accompanied by the sublimation of DNB and structural change of CL-20. The phase transition of β → γ-CL-20 was observed at 120 °C. The kinetics of decomposition and the mechanism of micro structural evolution on CL-20/DNB cocrystals with heating were revealed. The primary NO⋯H hydrogen bonds of the cocrystal are broken, accompanied by the melting of DNB in the temperature range of 100-120 °C. Subsequently, the DNB single component decomposes completely, leading to lattice collapse of cocrystal; simultaneously, CL-20 undergoes a transition process from β phase to γ phase. Ultimately, γ-CL-20 gradually decomposes with increasing temperature. The activation energy of cocrystal is also obtained as 129 ± 10 kJ/mol. The understanding of cocrystal explosive was deepened and the further application was promoted.

The role of hydrophilic/hydrophobic group ratio of polyvinyl alcohol on the miscibility of amlodipine in orodispersible films: From molecular mechanism study to product attributes

The miscibility of the therapeutic drug in the polymer matrix is the key to the successful design and development of orodispersible films (ODFs). In the present study, four hydrolyzed polyvinyl alcohols (PVAs) with identical polymerization degree were investigated as carriers for Amlodipine (AML) ODFs systematically. The drug-polymer miscibility and the intermolecular interaction were investigated by Flory-Huggins theory, Gordon-Taylor theory, molecular simulation, FTIR, Raman and ¹H NMR. The product attributes of ODFs were also studied. A pharmacokinetic study in rats was then conducted using the film product of PVA5-72, the best performer tested. The results revealed that the drug-polymer miscibility decreased linearly with the increase of hydrolyzed degree of PVA. Hydrogen bonds formed between the drug and the hydrophilic and hydrophobic groups of PVAs were the main intermolecular interaction that caused the differences in drug-polymer miscibility. Furthermore, drug-polymer interaction influenced the product attributes of ODFs, including dissolution profile, mechanical properties and physical stability. The pharmacokinetic study showed the ODFs disintegrated rapidly, and the amorphous AML dissolved and absorbed in the gastrointestinal tract, which was comparable to the commercial product. The research offered a foundation for development scientists in designing and formulating PVA films.

Effect of fluoropolymer content on thermal and combustion performance of direct writing high-solid nanothermite composite

The addition of fluoropolymers can improve the reactivity of Al and enhance the combustion performance of thermites, which has attracted great interest. Also, direct writing 3D printing technology for the preparation of energetic materials is an innovative process that can meet a variety of complex requirements. In this study, soluble Viton F2311 was used as a binder, and F2311/Al/CuO (FMICs) nanocomposites were prepared by direct writing. The components of FMICs were evenly distributed without obvious agglomeration. The thermal and combustion properties of FMICs with different mass fractions of F2311 were systematically studied. As the F2311 content increases, the thermite reaction of FMICs is advanced and the system has a higher exothermic and combustion rate. The F2311 content had little effect on the combustion flame temperature of FMICs, all of which were above 2400 K. Compared with PTFE and new fluoropolymers/nanothermites, F2311/nanothermites shows better processability and reaction properties and probably has promising applications.