REACTIONS OF CALCO2246 IN AN ISOCYANATE CURED PBX FORMULATION;

摘要

Energetic materials tend to degrade with time, which can lead to a decrease insafety margins, increases in whole life cycle cost and loss of overall effectiveness.An important aspect of both propellant and polymer bonded explosive (PBX) ageingprocesses is the level of anti-oxidant present to prevent material deterioration that isassociated to auto-oxidation mechanisms.Ageing trials tend to measure the amount of anti-oxidant as an indication of thematerial's stage of degradation. That is to say, the rate of degradation is presumedto be dependent on the amount of antioxidant available to prevent cross-linking andsubsequent hardening of the polymer.In this work, the antioxidant chemistry of a PBX was studied using nuclear magneticresonance (NMR) and infrared spectroscopy techniques. It was demonstrated thatthe Calco2246 antioxidant was not consumed during the curing of HTPB withisocyanates in a number of compositions. However, in the analysis of one particularPBX composition, extracts analysed by NMR spectroscopy indicated that Calco2246was almost entirely consumed prior to ageing. Comparison of model compoundswith the extract spectra suggested that the phenolic groups on Calco2246 reactedwith isocyanates to form urethane species.Initial reactions of two antioxidant/urethane products suggested that a doublysubstituted Calco2246 species was an ineffective antioxidant whilst the singlysubstituted material did behave as an antioxidant but was less effective thanCalco2246.The reaction of Calco2246 with hexyl isocyanate in HTPB/DOA/catalyst/bondingagent was followed using NMR spectroscopy and a theoretical model was produced.