Effect and mechanism of lithium aluminium hydride on the pyrolysis process of RDX

Searching for efficient additives for explosives and propellants is always desirable but challenging. To understand the contribution of lithium aluminium hydride (LiAlH₄) to the decomposition process of cyclotrimethylenetrinitramine (RDX), the thermal decomposition behaviours of RDX with various ratios of LiAlH₄ addition were investigated by thermogravimetric-differential scanning calorimetry (TG-DSC). The main pyrolysis gas products of RDX, RDX/LiAlH₄ (4:1) and RDX/LiAlH₄ (1:1) were compared by combining thermogravimetric-Fourier infrared spectroscopy (TG-FTIR) and thermogravimetric-photoionization mass spectrometry (TG-MS) techniques, and the influence of LiAlH₄ on the main RDX pyrolysis pathways was analysed. The results show a strong interaction between LiAlH₄ and RDX during thermal decomposition, and the decomposition peak temperature of RDX decreases from 239.8 °C to about 166.4 °C coupled with explosive decomposition. In the presence of LiAlH₄, the active hydrogen of the melted LiAlH₄ interacts with the nitro-oxygen of RDX, significantly decreasing the decomposition temperature of RDX and changing the decomposition pattern. This study contributes to further insight into the pyrolysis properties and decomposition mechanism of nitramine energetic materials in the presence of metal hydrides.