Ambient cured smokeless liner/inhibitor for propellants

Abstract

A liner composition is employed as a liner/inhibitor for a solid propellant rain while functioning as a liner-binder between the propellant grain and insulation or the motor case. The liner and inhibitor composition is prepared from the conventional binder systems (e.g., hydroxy terminated polybutadiene (HTPB), polysulfide, polyurethane, and polyester). The composition employs a cool burning oxidizer selected from oxamide and nitroguanidine. The type of solid propellant grain, particularly the crosslinking or reaction mechanism to form a chemical bond between the binder of the liner composition and the binder of the propellant, dictates the type formulation of the liner/inhibitor composition. A representative liner/inhibitor for a HTPB propellant grain contains from about 10 to about 70 weight percent oxidizer, from about 0.1 to about 1.0 weight percent cure catalyst selected from ferric acetyl acetonate and triphenyl bismuth, an isocyanate curing agent selected from toluene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate from about 1 to about 10 weight percent, and the balance of formulation hydroxy terminated polybutadiene. The use of the proper cure catalyst will produce a cured system at ambient (70.degree. F. or higher) in 24 hours. A chemical bond is formed between the liner and inhibitor binder and the propellant binder by the crosslinking action of the isocyanate curing agent and the hydroxyl groups of the binder systems. The chemical bond withstands the stresses of gas flow as well as the effects of spinning the rocket motor. Thus, the cool burning oxidizer in combination with the bonds between the binder systems which withstands the flow of gases will result in extinguishment of the liner/inhibitors at sudden pressure drop encountered at end of propellant grain burning and thereby result in elimination of smoke from the liner/inhibitor which is extinguished prior to bond failure.