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Differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA) were used to examine the thermal decomposition of benzoyl peroxide (BPO). The interruption rescanning method was adopted to examine the effect of thermal history on the autocatalysis and thermal decomposition of BPO. Autocatalysis of BPO was verified through isothermal experiments. According to the DSC linear temperature rise data of BPO, mathematical methods were used to decouple and divide the peaks. Kinetic analysis using both the Kissinger and Friedman methods was performed. The initial decomposition temperature of the decoupled BPO ranged between 101.4 and 104.6 °C. The peak temperature was 110.9–126.2 °C, and the decomposition enthalpy was 229.7–524.2 J g–1. The apparent activation energy was higher in the coupling state than after decoupling one. The thermal history and isothermal experiments demonstrated that BPO possessed autocatalytic properties. Results revealed that initial decomposition temperature tended to decrease with the increase in interruption temperature. In addition, the apparent activation energy of BPO decreased following the thermal history analysis because of the formation of intermediate products from BPO in the thermal history experiments, which further promoted BPO's thermal decomposition. This effect led to a decrease in BPO's initial decomposition temperature. [ABSTRACT FROM AUTHOR]

The flow stress behaviors of both the as-cast and homogenized Mg-8Gd-3Y-1Nd-0.5Zr alloy were investigated using a Gleeble-1500 thermal simulation test machine in the temperature range of 460-520 °C and strain rate range of 0.001-1 s. The processing maps for the two alloys were developed on the basis of flow stress data obtained at a strain of 0.5. It was found that the processing maps of both the as-cast alloy and homogenized alloy consisted of one stability and one instability domains. According to the processing maps and the microstructural observations, the optimum hot-working parameters for the two alloys were determined to be at a temperature of 500 °C and at a strain rate of 0.01 s. The hot workability of the homogenized alloy was better than the as-cast alloy in the safe domain, while the homogenization treatment increased the instability domain. The microvoids, which initiated along the dynamic recrystallized (DRX) grain boundaries and led to intercrystalline cracking, were an important factor contributing to the expanded instability domains for the homogenized alloy. Dynamic precipitation in the DRX grain in the as-cast alloy contributed to a lower DRX, hence prevented the formation of microvoids, which resulted in a reduced tendency for DRX intercrystalline cracking during hot deformation. [ABSTRACT FROM AUTHOR]

To improve the safety of ammonium nitrate explosives, the melamine urea-formaldehyde resin (MUF resin) was selected for the preparation of three typical nitramine explosives (cyclotetramethylenetetranitramine, HMX; cryclo-trimethylenetrinitramine, RDX; and hexanitrohexaazaisowurtzitane, CL-20) based green polymer-bonded explosives (GPBXs) via interfacial polymerization. Meanwhile, the corresponding composite particles prepared by physical mixing and drying bath methods were studied and compared. The particle morphology, crystal structure, thermal stability, and safety performance of the resultant composite particles were characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectra, differential scanning calorimeter (DSC), and impact sensitivity test, respectively. SEM results showed that MUF was successfully coated on the surface of the three explosives, and different composite particles prepared by the same method have their own unique characteristics. Such effect is attributed to the resin's ability to isolate and buffer external stimuli. It is obvious that the interfacial polymerization is an effective desensitization technique to prepare core-shell composite particles for explosives. [ABSTRACT FROM AUTHOR]