Thixotropic flame inhibitors for rocket propellant grains

Abstract

Disclosed is a thixotropic flame inhibitor for a rocket propellant grain luding an organic thixotrope in amounts from about 5 parts to about 30 parts into HTPB liquid polymer in amounts from about 70 parts to about 95 parts by stirring at elevated temperatures. After cooling the mixture to room temperature, appropriate quantities of di- or polyfunctional isocyanates and cure catalysts are added to promote cure at room temperature. Fine particulate matter may also be added to increase viscosity. The resulting formulation is a room-temperature curable, thixotropic mixture which will not flow under its own weight when applied to wettable non-horizontal surfaces in appreciable thicknesses, and which, when cured, is suitable as an inhibitor for composite solid rocket propellants. Thixotropy may be controlled by the level of organic thixotrope in the formulation while viscosity may be adjusted by the level of particulate filler; these parameters determine the allowable thicknesses from one-coat applications.