Studies on Curing of an Aluminized Ammonium Perchlorate Composite Propellant Based on Nitrile Butadiene Rubber Using a Quinol Ether of 1,4-Benzoquinone Dioxime

The isocyanate-based curing agents used for polyurethane are toxic and hygroscopic in nature. In the present work, an alternate approach was adopted, a reaction between the unsaturated rubber having an α-methylene hydrogen atom and a dinitrosobenzene (DNB) - generating system (quinol ether of 1,4-benzoquinone dioxime, QE) without a catalyst, thus generating a cured system. QE is a novel curing agent for propellant applications which imparts the necessary curing. The curing reaction between nitrile butatadiene rubber (NBR) and quinol ether (QE) was studied by FTIR and the results revealed the formation of anil groups (Ar–C=N). The anil group results from the reaction between NBR and DNB, generated on decomposition of QE. Propellant formulations were prepared with variation of the curing agent from 0.2 to 0.5%. The composition and rheological, mechanical, ballistic and thermal properties of the resulting cured systems were investigated. The viscosity and spreadability were suitable for casting. The tensile strength, modulus, and hardness show an increasing trend and the elongation decreases on varying QE from 0.2 to 0.5% in the propellant. However, all of the compositions showed nearly the same burning rate and pressure exponent. The QE based curing system is non-hygroscopic and has extremely low toxicity. The experimental results revealed that the proposed curing agent may find application in explosives and propellants.