Abstract
The heat-induced phase transitions of ε-HNIW, both neat and coated with various additives used in plastic bonded explosives, were investigated using powder X-ray diffraction and differential scanning calorimetry. It was found that ε-HNIW, after being held at 70°C for 60h, remained in the ε-phase. Applying other conditions, various phase transition parameters were determined, including Tc (the critical phase transition temperature), T50 (the temperature at which 50% of the phase transition is complete) and T180 (the percentage of γ-HNIW present in samples heated to 180°C). According to the above three parameters, additives were divided into three categories: those that delay phase transition, those that raise the critical temperature and the transition rate, and those that promote the phase transition. Based on the above data, a phase transition mechanism is proposed.
Highlights
The novel energetic compound 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (HNIW, widely known as CL-20) was first synthesized at China Lake by Nielsen in 1987.1 It is a polycyclic nitramine explosive with good chemical and thermal stability and exhibits suitable compatibility with most binders and plasticizers
Differential Scanning Calorimetry (DSC) was used to characterize the thermal behaviors of neat ε-HNIW and compound systems during heating to study the effects of different additives on phase transition of the ε-HNIW
Powder X-Ray Diffraction (PXRD) results confirmed the stability of the compound systems at ambient pressure and temperature
Summary
The novel energetic compound 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (HNIW, widely known as CL-20) was first synthesized at China Lake by Nielsen in 1987.1 It is a polycyclic nitramine explosive with good chemical and thermal stability and exhibits suitable compatibility with most binders and plasticizers. The density of pressed PBXs is affected by a number of variables, including particle size, morphology, pressing intensity, pressing temperature, and dwell time.[16]
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