Tsung-Mao Yang

This study mainly explored the performance characteristics of nitramine‐based (NB) gun propellants using TEGDN as an energetic plasticizer by experimental method. Three series of NB gun propellant samples with RDX, HMX or CL‐20 were prepared referring to the formulation of JA2 gun propellant. Their thermochemical characteristics, explosion heat, chemical stability and compatibility, impact, friction and electrostatic spark sensitivities, and compressive strength were determined by various instruments. The experimental results indicated that the NB gun propellant samples with RDX have lower decomposition temperature, and those with CL‐20 have higher thermogravimetric loss. Three series of NB gun propellant samples have good chemical stability and compatibility, and their explosion heat is close to that of JA2 gun propellant, but their sensitivity is lower than that of JA2 gun propellant. The maximum stress of three series of NB gun propellant samples decreases with increasing cyclic nitramine (RDX, HMX or CL‐20) content, and their compressive strength is better than that of JA2 gun propellant.

Traditional primary explosives often contain heavy metals, especially toxic lead, such as lead azide (LA) and lead styphnate (LS) that can cause environmental pollution problems. Copper(I) 5‐nitrotetrazolate (DBX‐1) is a green primary explosive without toxic heavy metals, which is considered as one of the most promising alternatives to LA. DBX‐1 is usually synthesized from sodium 5‐nitrotetrazolate dihydrate (NaNT ⋅ 2H₂O) and copper(I) chloride (CuCl). However, most of the synthesized products are irregular flakes with poor flowability, which affects the loadability. In this study, dextrin was used as a crystal shape modifier to improve the morphology of the synthesized product. Taguchi analysis method was used to determine the optimal experimental conditions for obtaining the spherical DBX‐1 with smaller particle size. The synthesized products were characterized by SEM, FTIR, UV‐Vis, STA TG‐DSC and VST, and their sensitivity was determined by BAM fallhammer, BAM friction tester and electrostatic spark sensitivity tester. The experiment results showed that the optimal combination of synthesis parameters was the NaNT ⋅ 2H₂O concentration of 4.4 wt.%, the reaction temperature of 100 °C, the reaction time of 75 min and the additional dextrin solution of 5.0 mL. The average particle size of the synthesized spherical DBX‐1 was 33.0 μm. The decomposition activation energy was calculated by Kissinger method and Ozawa method to be 178.5 and 178.8 kJ/mol, respectively. The compound had good chemical stability. In addition, the sensitivity of spherical DBX‐1 was lower compared to that of flaky DBX‐1 and LA.

This study mainly explored the characteristics of NC/HTPB-based high-energy gun propellants with RDX, CL-20 or TKX-50 by experimental method. Three series of test samples were prepared referring to the formulation of M1 single-base gun propellant (M1 SBP). The thermochemical characteristics, chemical stability, explosion heat, impact and friction sensitivities of prepared samples were determined by simultaneous differential scanning calorimetry–thermogravimetric analysis (STA DSC–TGA), vacuum stability tester (VST), bomb calorimeter (BC), BAM fallhammer and BAM friction tester, respectively, and compared with those of the reference sample M1. The experimental results indicated that the thermochemical characteristics of NC/HTPB-based high-energy gun propellants were similar to those of M1 SBP. The NC/HTPB-based high-energy gun propellants had good chemical stability and were superior to M1 SBP. The explosion heat of NC/HTPB-based high-energy gun propellants was close to and slightly larger than that of M1 SBP. In addition, the NC/HTPB-based high-energy gun propellants had lower impact and friction sensitivities than the M1 SBP. Therefore, the NC/HTPB-based high-energy gun propellants have the potential to replace the M1 SBP. The combustion performances of NC/HTPB-based high-energy gun propellants will be continuously studied and verified in the future.

The main aim of this study is to develop the vacuum pour‐casting process of the red phosphorus smoke agents. The typical composition of MK 58 marine location marker prepared by tamp‐casting process is red phosphorus (RP)/magnesium (Mg)/manganese dioxide (MnO₂)/zinc oxide (ZnO)/epoxy resin (ER), which was selected as the original formula. Epoxy resin (ER) was replaced by hydroxyl terminated polybutadiene (HTPB) as the binder. First of all, simultaneous differential scanning calorimetry‐thermogravimetric analysis (STA DSC‐TGA) and vacuum stability tester (VST) were used to analyze the thermochemical characteristics, stability and chemical compatibility of the formula. Afterwards, Taguchi's experimental design method was used to design nine experimental conditions by way of orthogonal array with four control factors and three levels, and the scaled‐down smoke pellets were prepared using the vacuum pour‐casting method. The combustion phenomenon of these smoke pellets was recorded by the visual‐image capture system, and the flame temperature was measured by the temperature measurement system. The burning rate was chosen as the quality characteristic to analyze the optimal parameter combination of minimum burning rate. In addition, scanning electron microscopy coupled with energy dispersive spectroscopy (SEM‐EDS), tensile testing machine (TTM) and hardness tester (HT) were employed to observe the uniformity of the composition distribution in the pellet and to measure the mechanical strength and hardness of the pellets. Smoke density test chamber (SDTC) was used to measure the specific optical density of smoke generated by RP smoke agent. Finally, the operating conditions of the optimal parameter combination determined by Taguchi method were used to prepare the full‐size smoke candle, and its burning performance was verified and the feasibility of the vacuum pour‐casting technology was evaluated. The experimental results indicated that the optimal combination of parameters was the RP mixture/HTPB mass ratio of 84 : 16, the NCO/OH ratio of IPDI to HTPB (R value) of 1.6, the additional DOA of 4.5 wt % and the curing temperature of 50 °C. The prepared scaled‐down smoke pellets had good stability, chemical compatibility, hardness, mechanical properties and burning smoke density. In addition, the burning time and performance of the full‐size smoke candles prepared by vacuum pour‐casting technology also met the requirements.

In this study, a case study to produce microcellular foam of a commercial thermoplastic polyurethane (TPU) through the supercritical carbon dioxide (CO₂) foaming process is presented. To explore the feasibility of TPU in medical device and biomedical application, a soft TPU with Shore hardness value of 70A was selected as the model compound. The effects of saturation temperature and saturation pressure ranging from 90 to 140 °C and 90 to 110 bar on the expansion ratio, cell size and cell density of the TPU foam were compared and discussed. Regarding the expansion ratio, the effect of saturation temperature was considerable and an intermediate saturation temperature of 100 °C was favorable to produce TPU microcellular foam with a high expansion ratio. On the other hand, the mean pore size and cell density of TPU foam can be efficiently manipulated by adjusting the saturation pressure. A high saturation pressure was beneficial to obtain TPU foam with small mean pore size and high cell density. This case study shows that the expansion ratio of TPU microcellular foam could be designed as high as 4.4. The cell size and cell density could be controlled within 12–40 μm and 5.0 × 10⁷–1.3 × 10⁹ cells/cm³, respectively.

This study is focused on the micronization of p-toluenesulfonamide (p-TSA) using the rapid expansion of supercritical solution (RESS) process. Taguchi’s experimental design method was applied to determine the optimum operating conditions. L₉(3⁴) orthogonal array with four control factors and three levels of each control factor was used to design nine experimental conditions. Four control factors were selected, including extraction temperature, extraction pressure, pre-expansion temperature, and post-expansion temperature. The particle size and morphology of the prepared samples were observed by scanning electron microscopy (SEM). In addition, Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC) were employed to compare the differences between the raw and micronized p-TSA particles. The experimental and analytical results indicated that the extraction temperature was the most significant factor for the micronization of p-TSA in the RESS process, and the optimal operating conditions were at an extraction temperature of 50 °C, an extraction pressure of 220 MPa, a pre-expansion temperature of 220 °C, and a post-expansion temperature of 30 °C. The p-TSA particles were micronized from the original average size of 294.8 μm to the smallest average size of 1.1 μm at the optimal RESS process conditions. Furthermore, the physicochemical characteristics of p-TSA did not differ significantly before and after recrystallization.

Two case studies of salicylamide particle size reduction and isoniazid derivative synthesis and crystallization realized using sonocrystallization were investigated. The size, habit, structure, thermal behavior, and spectrometric properties of sonocrystallized crystals were analyzed through scanning electron microscopy (SEM), powder X-ray diffractometry (PXRD), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) spectroscopy. The effects of the operating parameters, such as sonication intensity, sonication duration, and solution concentration, on sonocrystallization were compared. The crystal size of salicylamide was reduced from 595 μm (the original size) and was efficiently manipulated to be between 40 and 80 μm. Moreover, compared with the crystal habits of unprocessed crystals and recrystallized crystals fabricated through conventional methods, the crystal habit of salicylamide could be modified to present a regular shape. The structure, thermal behavior, and spectrometric properties of sonocrystallized salicylamide were found to be in agreement with those of an unprocessed sample. For producing isoniazid derivative crystals, N′-(propan-2-ylidene)-isonicotinohydrazide was synthesized using isoniazid in acetone at 318 K. The resulting solution was then cooled by applying power ultrasound to isolate N′-(propan-2-ylidene)-isonicotinohydrazide crystals. The solid-state properties of the synthesized N′-(propan-2-ylidene)-isonicotinohydrazide was verified through PXRD, DSC, and FTIR spectroscopy. The feasibility of particle size manipulation was then demonstrated through sonocrystallization.