Synthesis, characterization, migration and catalytic effects of energetic ionic ferrocene compounds on thermal decomposition of main components of solid propellants

• Energetic ionic ferrocene compounds are proposed as low-migration BR catalysts.
• 16 new ionic ferrocene derivatives have been synthesized and characterized.
• They are of highly thermal stability and low migration tendency.
• They show highly catalytic effects on thermal degradation of AP, HTPB and their 1:1 mixture.

Sixteen new energetic ionic ferrocene compounds, [FcCH2N(CH3)2(CnH2n+1]+X− (Fc = ferrocenyl; X− = nitrate or picrate anion; n = 3–10), were synthesized in high yields and characterized by 1H NMR, 13C NMR, UV–Vis, elementary analysis, TG and DSC methods. All the compounds show high thermal stability. Cyclic voltammetry investigations revealed that the ionic compounds exhibit redox waves for ferrocenyl groups and are considered as irreversible redox systems. Migration studies disclosed that their migration tendency increases with elongation of alkyl chain length in the cations of the compounds, and much slower than that of neutral n-butylferrocene (NBF). The sensitivities tests towards impact and friction revealed that all picrates are sensitive compounds, while the nitrates are less sensitive analogs. Their catalytic performances for thermal degradation of main components of solid propellants such as ammonium perchlorate (AP), 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), 1,2,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX) and hydroxyl-terminated polybutadiene (HTPB) as well as 1:1 mixture of HTPB and AP, were evaluated by DSC and/or TG techniques. All the ionic compounds can efficiently catalyze the thermal degradation of AP, HTPB and their 1:1 mixture. Compounds 1–8, 11 and 16 exhibit catalytic activity in thermal decomposition of RDX. None of them display distinct catalytic effect on the thermal degradation of HMX. These low-migration ferrocene derivatives may be used as alternatives to NBF in HTPB/AP composite solid propellants.

A series of energetic ionic ferrocene compounds were synthesized and fully characterized. These compounds exhibit high thermal stability and low migration tendency. The thermal experimentation clearly demonstrated that the ferrocenes efficiently catalyze thermal decomposition of ammonium perchlorate (AP), hydroxyl-terminated polybutadiene (HTPB) and their 1:1 mixture. They may be used as alternatives to n-butyl ferrocene in HTPB/AP composite solid propellants.Figure optionsDownload as PowerPoint slide