Issues Related with Pot Life Extension for Hydroxyl-Terminated Polybutadiene-Based Solid Propellant Binder System

Extension of the pot life for hydroxyl‐terminated polybutadiene (HTPB) based propellant binder systems was attempted through employing a bicurative system comprising of toluene‐di‐isocyanate (TDI) and isophorone‐di‐isocyanate (IPDI). Pot life characteristics were studied through evaluating curing kinetics for the HTPB‐bicurative binder formulations. Curing kinetics were studied through viscosity buildup during the cure reaction and estimation of the rate constants for viscosity build‐up. Introduction of IPDI slowed down the curing process, but at the same time, has not adversely affected the mechanical characteristics. One of the discouraging factors in adopting IPDI as curative is the poor interface characteristics between liner and insulator of the solid propellant grains, and it has been proposed that the root cause for the same is the permeation of IPDI through the insulator. Quantification of such permeation was attempted from the numerical values for cross‐link density evaluated for various binder compositions. Remedy for poor interface characteristics is suggested in this study.