Curing of energetic polymer

Abstract

Hydroxyl Terminated Polybutadiene (HTPB) based polyurethane elastomers are widely used as binders for composite propulsion systems used in modern rockets and missiles. However, the hydroxyl terminated polymer, HTPB, used in the formulation of the propellant is inert, which dilutes energy density of the composite. In order to overcome this problem, inert binders are being replaced by energetic polymer binders, which releases tremendous amount of energy during thermal decomposition, and contributes to the overall energy output of the formulation. In this study, the curing characteristics and thermal behavior of energetic Glycidyl Azide Polymer (GAP) are compared to the inert HTPB. Both the polymers were cured using the curing agent; Isophorone Diisocyanate(IPDI) in presence of a catalyst (dibutyltin dilaurate) and chain extender (butane 1,4 diol). The curing kinetics of both polymers was investigated by FTIR spectroscopy. The thermal decomposition kinetics of cured HTPB and GAP was treated by Kissinger analysis and the activation energies were computed. It is concluded that the cured GAP-IPDI system exhibits superior energy output as compared to the cured HTPB-IPDI system. The HTPB-IPDI system exhibits higher reaction rate, higher thermal stability andlower glass transition temperature.