A Thermoanalytical Investigation of Polyether Urethane Elastomers Suitable for Rocket Propellant Binders

摘要

To elucidate the firing instability encountered by the Air Force with some aged polyurethane rockets, which results in loss of chunks of propellant, an analytical investigation of thermal characteristics and stability was conducted on model compounds prepared from typical propellant raw materials, and on model propellant binder samples formulated with ammonium perchlorate to duplicate the chemical effects of the oxidizer. Formulation variables, catalysts and atmosphere all were found to affect thermal characteristics somewhat, but caused no catastrophic changes. A thermal popcorn effect was encountered at 300-350C with samples containing large excesses of isocyanate and which had been exposed to atmospheric moisture. This effect can be accounted for by volatilizations and dissociations which occur below urethane dissociation temperatures. The mathematics of steady-state propellant burning and pop-corning are discussed. Analytical correlations for infrared assignments, proton resonance (NMR) assignments, and thermogravimetric analyses were developed for application to polyurethanes. (Author)