Combustion and thermal behaviour of ballistically modified eva and estane based RDX-AP propellants

Abstract

This paper reports the findings of the combustion and thermal studies on RDXAP based propellants with ethylene vinyl acetate (EVA) and polyurethane-ester-MDI (Estane) binder systems plasticised with triacetin (TA) and glycidyl azide pre-polymer (GAP). Effect of incorporation of selected ballistic modifiers namely iron oxide, copper chromite, basic lead salicylate+cuprous oxide+carbon black combination and sodium borohydride (adsorbed on aluminium oxide) was also studied during this work. Incorporation of GAP as plasticizer in place of TA led to improvement in F by 36–52 J/g. Closed vessel evaluation results were in close agreement with the theoretically predicted performance. Burn rate enhancement by ballistic modifiers was observed in both acoustic burn rate experiments as well as closed vessel test. A major finding was the realization of pressure index value of the order of 0˙65–0˙68 with copper chromite in the high pressure regions (14–200 MPa) which is not reported earlier. DTA and DSC studies indicate that RDX decomposition is the major process during propellant degradation and ballistic modifiers catalyse condensed-phase/near-surface reactions involving GAP.