Ageing behaviour of rocket propellant formulations with ADN as oxidiser

摘要

Characteristics and ageing of several ADN containing composite rocket propellant formulations were investigated. Binders have been GAP cured with BPS (bis-propargyl succin-ate) and Desmophene~(tm) D2200 cured with Desmodur~(tm) N3400. Comparisons are made with AP analogues, with formulations where HMX has replaced Al, and with typical HTPB/Al/AP formulations. GAP-BPS/ADN/HMX and GAP-BPS/ADN/Al have low strength and low strain capability compared to HTPB/AP/Al-based propellants. Desmophene™ -bonded materials (ADN/Al, AP/Al, AP/HMX) have lower strain capabilities but higher strength values. The effectiveness of a bonding agent for ADN named HX-880 was studied, but a negligible effect on the mechanical properties was found and incompatibility with ADN was observed. SEM analyses of the GAP-BPS/ADN formulations showed the presence of voids and a high porosity of the propellant formulations. With ageing the ADN formulations showed remarkable chemical decomposition (mass loss measurements evidenced an autocatalytic behaviour at above 60°C) and, more severe, extended dewetting between matrix and ADN prills. The glass transition temperatures determined by DMA for the GAP- and Desmophene™-based formulations are about half as negative as the values of the AP/Al/HTPB-based propellants. The dynamic mechanical behaviour of the ADN formulations is different to the HTPB-based materials. Only one obvious peak in the loss factor curve was found instead of two. The filler (HMX or Al), oxidisers (AP or ADN) and curing agents (BPS or N3400) have influences on the glass transition temperature, peak broadness and apparent activation energy of the shift of peak temperature. The total peak of the GAP formulations is broader than the one of the Desmophene™ formulations. Lowering of T_g by the addition of AP was found. The fact that systematically the glass transition temperature is lower with AP compared to the ADN-based formulations can be explained with a stronger interaction between ADN and binder chains than between AP and binder chains.