Aging Effects on the Burning Rates of Composite Solid Propellants with Nano-Additives

Abstract

The aging behavior of composite propellant is a key parameter in determining the usable service life of an energetic system. The effect of aging on composite propellant burning rates is an understudied topic in the open literature. Recent research in the authors’ laboratory has led to the development of high-burning rate propellants containing titania nanoparticles and fluorescing propellants containing quantum dots. The current study assessed the aging behavior of composite ammonium perchlorate (AP)/hydroxyl terminated polybutadiene propellants, with specific emphasis on fluorescent properties and burning rates. Propellant formulations were based on either 80% monomodal or 85% bimodal AP distributions with and without titania nanoparticles and quantum dots. Propellant samples were thermally aged at temperatures of 63 and 85°C and humidity levels of 25 and 75% for up to 195 days to yield approximate service lives in the range of 0–25 years. Fluorescent imaging experiments were conducted with an ultraviolet light source to measure the uniformity of propellant samples. Ballistic testing was conducted in a constant-volume strand burner over the pressure range of 500–2250 psia (3.5–15.5 MPa). Spatial uniformity of the propellant fluorescence was not significantly altered with propellant age but did decrease in intensity to some degree. In general, the burning rate and pressure index of propellants decreased with increasing service life. Propellant formulations containing 85% bimodal AP were found to be more stable than formulations containing 80% monomodal AP. Inclusion of quantum dots or titania nanoparticles in the propellant formulation increased aging stability.