Characterization of 1,2,3-triazole crosslinked polymers based on azide chain-ends prepolymers and a dipolarophile curing agent as propellant binders: The effect of a plasticizer

The 1,2,3-triazole crosslinked polymers with potential use as a binder system in solid rocket propellants were prepared by mixing of an azide chain-ends diazide prepolymer, a dipolarophile curing agent, which act as a crosslinker, and a plasticizer at CC/N3 ratio of 1.1. A wide range of the plasticizer ratios were investigated: 0-300 wt% for the polycaprolactone (PCP) and polycaprolactone ether (PCE) prepolymer based binders, and 0-500 wt% for the polyethylene glycol (PEG) prepolymer based binder. Even at high amounts of plasticizer, sufficient initial reactivity and good conversion were obtained, however the increase of viscosity was considerably delayed. Crystalline domains of in the 1,2,3-triazole crosslinked polymers were effectively eliminated by the plasticizer. The tensile strength and modulus (100% and 300%, respectively) decreased with increasing of the amount of plasticizer whereas the elongation at the break was only modestly affected. PCP showed excellent elongation at the break compared to PEG at the same levels of plasticizer as well as good tensile strength. In contrast, the binder network prepared from the PCE prepolymer collapsed due to its low degree of crosslinking.