Study on thermal performance of FOX 7/HMX mixed system

DOI:	10.11809/bqzbgcxb2024.01.028
Keywords:	1, 1 diamino 2, 2 dinitroethylene (FOX 7); octogen (HMX); thermal decomposition; crystal transformation; thermal conductivity
Abstract:	To study the thermal properties of FOX 7 and its mixed system with HMX, differential scanning calorimetry (DSC) and thermal constant analyzer were used to investigate the thermal decomposition behavior, thermal conductivity, and other thermal properties of HMX and FOX 7 blends, as well as explosive formula with different ratios of HMX to FOX 7. The thermal properties of explosive formulations were also studied by slow burning test. The results show that in the FOX 7/HMX mixed system, the decomposition heat release and crystal form transformation heat absorption of HMX and FOX 7 interact with each other: HMX is partially decomposed at 247.3 ℃, and the exothermic peaks at 282.5 ℃ corresponding to the superposition of the decomposition peak of HMX and the second decomposition peak of FOX 7. The endothermic peaks of β γ transition of FOX 7 and β δ transition of HMX are delayed by 8.5 ℃ and 9.5 ℃, respectively compared with those of elemental particles. The relative content of HMX and FOX 7 in the formula determines the decomposition peak temperature of both, which may be related to the mutual influence of the thermal effect of the two and the integrity of the adhesive on the encapsulation of explosive particles. As the HMX content in the formula increases from 25% to 60%, its melting endothermic peak advances from 276.6 ℃ to 252.5 ℃; As the content of FOX 7 in the formula increases from 25% to 60%, the first step decomposition peak and the melting decomposition process of HMX interact, resulting in only one exothermic decomposition peak. The exothermic decomposition reaction of FOX 7 in the first step will cause it to undergo melting decomposition earlier.The thermal conductivity, thermal diffusivity, and specific heat capacity of FOX 7 particles are higher than those of HMX. With the increase of FOX 7 content and the decrease of HMX content, the thermal conductivity, thermal diffusion coefficient, and specific heat capacity of the mixed explosive formula increase with the constant total content.
Published:	2024-01-28
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